IMPROVEMENT OF PHYSICO-CHEMICAL PROPERTIES OF …

IMPROVEMENT OF PHYSICO-CHEMICAL PROPERTIES OF

PALM OLEIN BLENDED WITH RICE BRAN OIL

By

Surin Watanapoon

A Master’s Report Submitted in Partial Fulfillment of the Requirements for the Degree

MASTER OF SCIENCE

Department of Food Technology

Graduate School

SILPAKORN UNIVERSITY

2004

ISBN 974 – 464 – 509 - 1

การปรับปรงุคณุลักษณะทางกายภาพ และ ทางเคมีของน้าํมันปาลมโอเลอีน ผสมกับน้ํามนัรําขาว

โดย นายสุรินทร วฒันพูล

สารนิพนธนี้เปนสวนหนึง่ของการศึกษาตามหลักสูตรปริญญาวิทยาศาสตรมหาบัณฑิต สาขาวิชาเทคโนโลยีอาหาร ภาควชิาเทคโนโลยีอาหาร

บัณฑิตวิทยาลัย มหาวิทยาลัยศิลปากร ปการศึกษา 2547

ISBN 974 – 464 – 509 – 1 ลิขสิทธ์ิของบณัฑิตวิทยาลัย มหาวิทยาลัยศิลปากร

The graduate school, Silpakorn University accepted master’s report entitled

“IMPROVEMENT OF PHYSICO-CHEMICAL PROPERTIES OF PALM OLEIN

BLENDED WITH RICE BRAN OIL” by Surin Watanapoon in partial fulfillment of

the requirements for the degree of master of science, program of food technology.

……………………………………. (Asso. Prof. Chirawan kongklai, Ph.D.)

Dean of graduate school

……./……./…….

Master’s Report advisor

Bhundit Innawong, Ph.D.

Master’s Report committee

…………………………………. Chairman

(Arunsri Leejeerajumnean, Ph.D.)

………/……../………

…………………………………. Member

(Bhundit Innawong, Ph.D.)

………/……../………

…………………………………. Member

(Sopark Sornwai, Ph.D.)

………/……../………

IV

K 44403357 : สาขาวิชาเทคโนโลยีอาหาร คําสําคัญ : น้ํามันปาลมโอเลอีน / น้ํามันรําขาว / ความคงตัวตอความเย็น / ความคงตัวตอความรอน สุรินทร วัฒนพูล : การปรับปรุงคุณลักษณะทางกายภาพและทางเคมีของน้ํามันปาลมโอเลอีนผสมกับน้ํามันรําขาว (IMPROVEMENT OF PHYSICO-CHEMICAL PROPERTIES OF PALM OLEIN BLENDED WITH RICE BRAN OIL) อาจารยผูควบคุมสารนิพนธ : อ. ดร. บัณฑิต อินณวงศ. 104 หนา. ISBN 974-464-509-1

น้ํามันปาลมโอเลอีน เปนน้ํามันที่ใชมากในอุตสาหกรรมการทอด อยางไรก็ตาม น้ํามันปาลมโอเลอีนก็มี

ขอจํากัด คือการงายตอการตกผลึกที่ดานลางของภาชนะบรรจุหรือเมื่อเก็บไวเปนเวลานาน การศึกษาวิจัยนี้ไดคนหาการตานทานการตกผลึกของน้ํามันปาลมโอเลอีนโดยผสมกับน้ํามันรําขาวในอัตราสวนตาง ๆ กัน รวมถึงการประเมินคุณภาพของน้ํามันดาน ความคงตัวตอความรอนของน้ํามันปาลมโอเลอีนที่ผสมกับน้ํามันรําขาวอีกดวย

จากการศึกษาการตานทานการตกผลึกของน้ํามันปาลมโอเลอีนเมื่อผสมกับน้ํามันรําขาวในอัตราสวนตางกัน โดยศึกษาถึงการเปลี่ยนแปลงดาน การทดสอบที่อุณหภูมิตํ่า จุดขุนมัว และ ความคงตัวตอความรอน โดยการที่จะใหความรอนที่อุณหภูมิ 180 องศาเซลเซียส และ โดยไมมีการกวน ทําการทดสอบสมรรถนะการทอดดวยการทอดดวยมันฝรั่งสด ซึ่งจะประเมินคุณลักษณะทางกายภาพและทางเคมีของน้ํามันดวย การเปลี่ยนแปลงของสีทั้งหมด ความหนืด จุดการเกิดควัน ปริมาณกรดไขมันอิสระ และ คาเปอรออกไซด

การใชน้ํามันรําขาวในปริมาณที่สูง จะชวยชะลอการเกิดผลึกสีขาวในน้ํามันปาลมโอเลอีน โดยมีการลดลงของจุดขุนมัว เมื่อเทียบกับน้ํามันปาลมโอเลอีน 100 เปอรเซ็นต โดยน้ํามันรําขาวจะแสดงผลลบตอการทดสอบที่อุณหภูมิตํ่า จึงไมเหมาะตอการนําไปทําน้ําสลัด น้ํามันรําขาวสามารถปรับปรุงคุณลักษณะทางกายภาพและทางเคมีของน้ํามันผสม โดยทําใหน้ํามันผสมมีความคงตัวตอความรอนสูงขึ้นเมื่อเทียบกับน้ํามันปาลมโอเลอีน 100 เปอรเซ็นต การผสมน้ํามันปาลมโอเลอีนกับน้ํามันรําขาว 50 เปอรเซ็นต จะใหผลตอการเปลี่ยนแปลงปริมาณกรดไขมันอิสระ คาเปอรออกไซด และความหนืด เล็กนอย เพราะฉะนั้น น้ํามันรําขาวนอกจากสามารถปรับปรุงการตานทานการตกผลึกแลว แตยังชวยปรับปรุงความสามารถในการตานทานความรอนใหกับน้ํามันผสม เมื่อเทียบกับน้ํามันปาลมโอเลอีนอีกดวย ภาควิชาเทคโนโลยอีาหาร บัณฑิตวิทยาลัย มหาวิทยาลัยศิลปากร ปการศึกษา 2547

ลายมื่อช่ือนักศึกษา …………………………………

ลายมือช่ืออาจารยผูควบคุมสารนิพนธ …………………………………….

V

K 44403357: MAJOR: FOOD TECHNOLOGY

KEY WORD: PALM OLEIN / RICE BRAN OIL / COLD STABILITY / THERMAL

STABILITY

SURIN WATANAPOON : IMPROVEMENT OF PHYSICO-CHEMICAL OF

PALM OLEIN BLENDED WITH RICE BRAN OIL. MASTER’S REPORT

ADVISOR: BHUTDIT INNAWONG, Ph.D. 104 pp. ISBN 974-464-509-1

Palm olein (PO) was widely used in frying industry. However, it proned to

form a fat crystals at the bottom of the container or after long periods of storage. This

study was investigated to determine the resistance on crystallization of the blended oil

between palm olein and rice bran oil (RBO) at various proportions. Their thermal and

cold stabilities of the blended oils were also evaluated.

The resistance to crystallization of PO blended with RBO at various

proportions was determined by means of monitoring the changes in cold test and

measuring the cloud point. The thermal stability was conducted by continuous heating

without agitation and frying at 180oC. The changes in physico-chemical properties of

oils were detected by several physical and chemical indexes consisting of overall color

difference, viscosity, smoke point, free fatty acid content (FFA), and peroxide value

(PV).

The blended oils with high RBO were able to retard the formation of white

crystals and resulted in the reduction of the cloud point as compared with the control

(100% PO). The additional RBO in blended oil represented the negative responses in

cold test, and these oils could not used for the salad oil manufacturing. RBO improved

the physico-chemical properties of the blended oils and exhibited high thermal stability

as compare with the control. Blending PO with 50% RBO strongly was recommended

as the minimum changes in FFA, PV, and viscosity. Therefore, the blending of RBO

in PO was the potential technique to improve not only the resistance from

crystallization but also elevated thermal stability of blended oil.

Department of Food Technology Graduate School, Silpakorn University Academic Year 2004

Student’s signature ………………………………

Master’s Report Advisor’s signature …………….………………..

VI

ACKNOWLEDGEMENTS

I wish to express my sincere thanks to my advisor Dr. Bhundit Innawong for

his kindness, ideas, and knowledgeable advice everywhere my Mater’s program. I

gratefully thanks for the time to make suggestions and help me for the master report

preparations.

I gratefully thank for my committee Dr. Arunsri Leejeerajumnean and Dr.

Soprak Sornwai. I would like to thank all graduate school and my friends that assisted

in this research. I many thank all staffs and faculty in Food Technology department

for the good things during I spent time at the department.

I sincerely thank Pamola Company Limited that time and resource support

during this research. I would like to thank all works staffs who to work together and to

share happiness and trouble throughout my job.

Many thanks all of my parents, my wife’s parents, and relations for their love,

opportunity, spirit, and financial support that they are given me throughout my

program. Finally, I lovely thank my wife who to share happiness and trouble and spirit

that she has given me every times.

VII

TABLE OF CONTENTS

Page

Thai Abstract ……..........................................................…................………….........IV

English Abstract …….………….……………………………………………………..V

Acknowledgements ……….........................................................................................VI

List of tables ……….................................................….............................................VIII

List of figures ………..................................................................................................IX

Chapter

1 Introduction ………............................................................................................1

2 Literature review …………................................................................................3

2.1 Palm oil ………................................................................................3

2.2 Rice bran oil ...................................................................................17

2.3 Blended oil .....................................................................................22

2.4 Crystallization of fats and oils .......................................................23

References ………................................................................................25

3 Resistant to crystallization of palm olein blended with rice bran oil ………..29

4 Thermal stability of palm olein blended with rice bran oil ….…………........41

5 Summary …………………...….......................................................................64

Appendix

Appendix A ...............………..........................................................................65

Appendix B ......…...........................................................................................76

Vita ..............................…..........................................................................................104

.

VIII

LIST OF TABLES

Table Page

2.1 Fatty acid composition of palm oil. ........................................…........................4

2.2 Triglyceride composition of crude palm oil. .............….....................................7

2.3 Major physical properties of palm oil. ..................…..........................................8

2.4 Refining crude palm oil: unit process. ......................................…....................12

2.5 Fatty acid composition and physical characteristic of palm oil product .........13

2.6 Triglyceride compositions of palm oil products.........…...................................13

2.7 Typical fatty acids composition of rice bran oil. ...........................…...............18

2.8 Characteristic of refined rice bran oil .............................…..............................21

3.1 Changes in cloud point and cold test of palm olein blended with

rice bran oil. ………………………………………………………….37

4.1 Changes in color value of palm olein blended with rice bran oil

by heating method. …………………………………………………...52

4.2 Changes in color value of palm olein blended with rice bran oil

by frying method. …………………………………………………….53

IX

LIST OF FIGURES

Figure Page

2.1 Extraction of crude palm oil. ..............................…............................................5

2.2 Refining of palm oil. ......................................……............................................6

2.3 Dry fractionation process. ........................................……..................................9

2.4 Detergent fractionation process. .......................................…............................10

2.5 Solvent fractionation process. ..................…….................................................11

2.6 Palm oil utilization chart. .......................……...................................................16

2.7 Rice bran oil extraction process. .................................……..............................19

2.8 Rice bran oil refining process. ..........................……........................................20

3.1 Physical characteristic of palm olein blended with rice bran oil stored

on day 5 and day 10 ……………………………………..…………...38


on day 15 and day 20 …………………...……………………………39


on day 25 and day 30 …………………………...……………………40

4.1 Changes in overall color difference of palm olein blended with rice bran oil

in heating method. …………………………………………………...54

4.2 Changes in overall color difference of palm olein blended with rice bran oil

in frying method. …………………………………………………….55

4.3 Changes in viscosity of palm olein blended with rice bran oil in heating

method. ………………………………………………………………56

4.4 Changes in viscosity of palm olein blended with rice bran oil in frying

method. ……….……………………………………………….……..57

4.5 Changes in smoke point of palm olein blended with rice bran oil in heating

method. ………………………………………………………………58

4.6 Changes in smoke point of palm olein blended with rice bran oil in frying

method. ………………………………………………………………59

X

Figure Page

4.7 Changes in free fatty acid of palm olein blended with rice bran oil in heating

method. ………………………………………………………………60

4.8 Changes in free fatty acid of palm olein blended with rice bran oil in frying

method. ………………………………………………………………61

4.9 Changes in peroxide value of palm olein blended with rice bran oil in heating

method. ………………………………………………………………62

4.10 Changes in peroxide value of palm olein blended with rice bran oil in frying

method. ………………………………………………………………63

1

CHAPTER 1

INTRODUCTION

Frying oil is considered as the major raw material used in the frying

manufactures and its quality intimately relates to the fried product properties. Because

fat becomes an integral part of the product during the frying process, it is important to

make certainly that the fat can deliver the correct characteristics such as flavor, texture,

appearance, health, and content claims (Saguy and Dana, 2003). Thus, the frying fat

and oil commonly selected to fill into the fryers must be more able to resist the

oxidative deterioration. The oils with high saturated or monounsaturated fatty acid

contents such palm olein, peanut oil, and coconut oil can compatibly meet this

requirement. However, these oils still have a little problem in the appearance due to

the clouding formation during shelf storage. In addition, the consumers always

assumed the clouding appearance representing low quality attributes of oil although

the clouding did not detrimentally influenced the oil quality (Siew and Ng, 1996; Swe

et al., 1994).

Palm olein (PO) was the liquid fraction from palm oil in the fractionation

process. Normally, it contained about 46% saturated fatty acid and it was widely used

in frying industry due to its excellent frying performance and oxidative stability (Anon,

1991; Basiron, 1996). However, the palm olein tended to form cloud appearance and

results in the visible suspension of fat crystals normally seen in the container at the low

temperature or after long period of storage at room temperature. The fat crystals

forming in the container were normally in the β-form of saturated fatty acids and

diglycerides. The β-form of fat crystal expressed the highest melting points when

compared to others (Siew and Ng, 1996; Swe et al., 1994; Swe et al., 1995).

The several procedures were conducted to reduce the clouding problem, for

example, the application of double fractionation process, the use of crystal inhibitor,

and the oil blending technique. Double fractionation was the process applying the

Chapter 1: Introduction 2

second crystallization of palm olein to elevate iodine value above 60 (Basiron, 1996).

The crystal inhibitor was a fat-soluble products comprising of general molecule

structure similar to triglyceride but differ in some specific ways. The chemical

compounds potentially retarding the crystal growth, as the fat crystal inhibitors, for

instance, lecithin, oxystearin, and polyglycerol (Weiss, 1983). The blending of the

high unsaturated fatty acid oil, for instance, soybean oil (SBO), sunflower seed oil

(SFO), rice bran oil (RBO), and safflower seed oil (SAF) together with palm olein to

reduce the crystallization of triglyceride at low temperature was introduced by many

researchers. Mostafa et al. (1996) reported that palm olein blended with cottonseed

oils could decrease the cloud point. Teah and Ahmad (1991) investigated the mixing

oil consisting of sunflower seed oil, single fractionated palm olein, and double

fractionated palm olein was capable to inhibit the formation of fat crystals at temperate

climate.

Rice bran oil, also called rice oil was obtained from the rice milling process,

and used extensively in Asian countries (Orthoefer, 1996b). RBO normally contained

approximately 40% polyunsaturated, 40% monounsaturated, and 20% saturated fatty

acid (Orthoefer, 1996a). In addition, rice bran oil also comprised the nutritious

substance, known as a γ- oryzanol, preventing the oxidation during frying and it

contains 400 mg/kg oil of total tocotrienol (Sonntag, 1979). This substance could

retard the rate of oxidation equal to palm oil (Rossell, 2001).

Then, rice oil could be the potential oil using to blend with palm olein for

preventing fat crystals formation during oil storage. However, the blends between

palm olein and rice bran oil would change the physical and chemical characteristic

such as an increase in viscosity and color, and the reduction of the degree of

unsaturation during heating and frying similar to PO application (Moreira et al., 1988;

Orthoefer et al., 1996 White, 1991).

The objective of this study was to investigate the changes in physico-chemical

properties of the blended oil between palm olein and rice bran oil. The effect of

different blending ratio was investigated to figure out the blended oil preventing higher

thermal stability, better frying performance and appearance.

3

CHAPTER 2

LITERATURE REVIEW

2.1 Palm oil

Palm oil is derived from the mesocarp of the palm fruit, species Elaeis

guineesis. Presently, palm oil is now the second largest vegetable oil in the world

production and the leader in the world exports (Pantzaris, 1995). In generally, palm oil

had reddish brown in color due to it was high content of carotenoid, α and β carotene

about 500-700 ppm. During refining process, the β-carotene was gradually decreased.

Palm oil has a semi-solid consistency at ambient temperature, due to containing about

50% of saturated fatty acids and about 50% unsaturated fatty acids. The chain lengths

of fatty acids presented in the triglyceride comprising of a very narrow range from 12

to 20 carbon atoms (Basiron, 1996).

Sambanthamurthi et al. (2000) reported that over 95% of palm oil consisted of

the mix triglycerides containing glycerol molecules as the backbone and each of

molecule esterified with the three fatty acid. The major fatty acids in palm oil were

myristic, palmitic, stearic, oleic, and linoleic (Table 2.1). Goh (1991) reported that

two major components of triglycerides in palm oil were unsaturated-dipalmitin (C50)

and palmitounsaturated (C52) (Table 2.2). Normally C50 included palmitic-oleic-

palmitic (POP) and palmitic-palmitic-oleic (PPO), and C52 was palmitic-oleic-oleic

(POO) (Basiron, 1996). However, the triglycerides in palm oil partially exhibited the

physical characteristics of the palm oil such as melting point and crystallization

behavior (Sambanthamurthi et al., 2000).

Sambanthamurthi et al. (2000) reported that the minor constituents of palm oil

could be divided into two groups. The first group consisted of fatty acid derivatives,

such as partial glycerides (mono-and diglycerides), phosphatides, ester and sterols.

The second group included classes of compounds not related chemically to fatty acid,

such as hydrocarbons, aliphatic alcohols, free sterols, tocopherol, pigments, and trace

Chapter 2: Literature review 4

metals. Most of the minor components found in the unsaponnifiables fraction of palm

oil were sterols, higher aliphatic alcohol, pigments, and hydrocarbons. In addition,

palm oil contained mainly three types of diglyceride, C32 (dipalmitoylglycerol or PP),

C34 (palmitoyloleoylglycerol or PO), and C36 (dioleoylglycerol or OO). The

diglycerides in palm oil affected its physical property such as crystallization (Table

2.3).

Basiron (1996) reported that the extraction processes of palm oil usually began

with the fruit reception, sterilization, stripping, digestion, oil extraction, clarification,

and oil storage, respectively (Figure 2.1). Crude palm oil was extracted commercially

from the fresh fruit bunches variable amount of undesirable components and

impurities, such as mesocarp fibers, moisture and insoluble, free fatty acid,

phosphatides, trace metals, and oxidation products. As the result, palm oil was

normally refined to bland, stable product before used for consumption or formulation

of edible product (Figure 2.2).

Table 2.1 Fatty acid composition of palm oil

Weight (%)

Fatty acid Symbol Mean Range

Saturated Acids

Lauric C12:0 0.2 0.1 – 0.3

Myristic C14:0 1.1 1.0 – 1.3

Palmitic C16:0 44.7 43.9 – 46.0

Stearic C18:0 4.2 3.9 – 4.4

Arachidic C20:0 0.4 0.3 – 0.7

Mono-unsaturated Acids

Palmitoleic C16:0 0.1 0 – 0.1

Oleic C18:0 39.2 38.0 – 40.6

Poly-unsaturated Acids

Linoleic C18:2 10.0 9.2 – 10.5

Linolenic C18:3 0.3 0.3 – 0.6 Source: (Goh, 1991)


FRUIT RECEPTION

Fresh fruit bunches

STERILIZATION

STRIPPING

DIGESTION

OIL EXTRACTION

CLARIFICATION

CRUDE PALM OIL

STORAGE

Figure 2.1 Extraction of crude palm oil Source: (NorAini et al., 1992)

By steam in 3 horizontal sterilizers Peak pressure: 40-45 psi Time: 75-90 min

In rotary drum stripper Speed: 21-23 rpm

In steam-jacketed Cylindrical vessels with vertical Rotary shaft Temperature: 90-95oC

By screw press

At 85-95oC In settling tank


CRUDE PALM OIL

DEGUMMING

BLEACHING

FILTRATION

FFA DISTILLATION & DEODORIZATION

COOLING

POLISHING

REFINED, BLEACHED & DEODORIZED PALM OIL STORAGE

Figure 2.2 Refining of palm oil Source: (NorAini et al., 1992)

Phosphoric acid 0.1% Temperature: 80oC Time: 15 min /Under vacuum

Bleaching earth 1% Temperature: 95oC Time: 30 min

Temperature: 260oC Time: 1 ½-2 hr

Under vacuum

Pass through filter


Table 2.2 Triglyceride composition of crude palm oil

Weight (%)

Triglycerides Mean Range

C46 0.8 0.4 – 1.2

C48 7.4 4.7 – 10.8

C50 42.6 40.0 – 45.2 (POP, PPO)

C52 40.5 38.2 – 43.8 (POO)

C54 8.0 6.4 – 11.4 Source: (Goh, 1991)

Basiron (1996) reported that two methods of refining, namely physical and

chemical refinings, were available to refinie crude palm oil (Table 2.4). However,

physical refining has become the major processing route because of cost effective,

high efficiency, and simple effluent treatment. However, both processes were able to

produce refined, bleached, and deodorized (RBD) palm oil of desirable quality and

stability for edible purposes.


Table 2.3 Major physical properties of palm oil

Property Mean Range

Apparent density at 50oC g/ml 0.889 0.888 – 0.889

Refractive index at 50oC 1.455 1.455 – 1.456

Solid fat content (%)

At 5oC 60.5 50.7 – 68.0

At 10oC 49.6 40.0 – 55.2

At 15oC 34.7 27.2 – 39.7

At 20oC 22.5 14.7 – 27.9

At 25oC 13.5 6.5 – 18.5

At 30oC 9.2 4.5 – 14.1

At 35oC 6.6 1.8 – 11.7

At 40oC 4.0 0.0 – 7.5

At 45oC 0.7 -

Slip point (oC) 34.2 31.1 – 37.6 Source: (Sambanthamurthi et al., 2000)

The triglycerides in palm oil usually consisted of a combination of fatty acids

with different chain lengths as well as degrees of unsaturation. This resulted in the

presence of substantial quantity of both low and high melting triglycerides.

Fractionation, the crystallization of the oil under controlled cooling followed by

separation was applied to yield a low melting liquid phase (olein) and a high melting

solid phase (stearin) (Basiron, 1996).

Gunstone and Norris (1983) reported that fractionation process could be

classified to three methods, such as dry fractionation, detergent fractionation, and

solvent fractionation (Figure 2.3, 2.4, and 2.5, respectively). However, the dry

fractionation was the most widely used process. It was fully reversible modification

process, as it involved no chemical change in composition (Kellens, 1993).


PALM OIL

MELTING

CRYSTALLIZATION

FILTRATION

PALM OLEIN PALM STEARIN

Figure 2.3 Dry fractionation process Source: (Bernardini, 1983)


CRYSTALLIZATION

MIXER

FIRST CENTRIFUGATION

DETERGENT

SUSPENSION

STEARIN-DETERGENT

MELTING

OLEIN SECOND CENTRIFUGATION

STEARIN DETERGENT

Figure 2.4 Detergent fractionation process Source: (Bernardini 1983)


Palm oil Solvent

1st Crystallization

1st Filtration

1st Solid phase Liquid phase

2nd Crystallization

2nd Filtration

2nd Solid phase Olein phase

Distillation Distillation Distillation

Solvent

Stearin Stearin Olein

Figure 2.5 Solvent fractionation process Source: (Bernardini 1983)


Table 2.4 Refining crude palm oil: unit process

Stage Principal impurities reduced or removed

Degumming Phospholipids, trace metals, pigments

Neutralization Fatty acids, phospholipids, pigments, oil insoluble, water

soluble

Washing Soap

Drying Water

Bleaching Pigments, oxidation products, trace metal, traces of soap

Filtration Spent bleaching earth

Deodorization Fatty acids, mono-and diglyceride, oxidation products, pigment

Physical refining Fatty acids, mono-and diglyceride, oxidation products, pigment

Polishing Removal of trace oil insoluble Source: (Basiron, 1996)

Palm olein, was the liquid fraction obtained from fractionation of palm oil after

crystallization under controlled temperature. The physical characteristics of palm

olein differed significantly from those of palm oil. It was fully liquid in ambient

temperature (Pantzaris, 1995). However, the difference in fatty acid compositions was

also worthy, for instance, oleic and linoleic acid contents increased and the saturated

fatty acid content was lowered (Anon, 1991). Two major grades of palm olein were

produced in Malaysia, standard olein and double fractionated (or super) olein, which

has lower cloud point (Pantzaris, 1995).

PO application extended from daily usage in the kitchen toward the industrial

uses. It contained the excellent physical properties and oxidative stability for deep-

frying involving temperature over 180oC, due to vary low content of linolenic fatty

acid and combined with the naturally occurring vitamin E. Furthermore, foods fried in

palm oil and palm olein gradually absorbed less fat and tended to be less soggy than in

the case with other vegetable oils as shown in Table 2.5 and 2.6 (Anon, 1991).

Palm stearin, the solid fraction of palm oil, was characterized by a higher

melting point and a lower iodine value than those of the unfractionated oil. However,


during crystallization at controlled temperature, it was a co-product of palm olein.

Palm stearin was very useful source for the fully natural hard fat component used to

produce such as shortening, pastry margarine, vanaspati, etc. (Anon, 1991; Pantzaris,

1995).

Table 2.5 Fatty acids composition and physical characteristics of palm oil products

Fatty acids Palm oil Palm olein Palm stearin

C12:0 0 – 0.4 0.1 – 1.1 0.1 – 0.6

C14:0 0.6 – 1.7 0.9 – 1.4 1.1 – 1.9

C16:0 41.1 – 47.0 37.9 – 41.7 47.2 – 73.8

C16:1 0 – 0.6 0.1 – 0.4 0.05 – 0.2

C18:0 3.7 – 5.6 4.0 – 4.8 4.4 – 5.6

C18:1 38.2 – 43.5 40.7 – 43.9 15.6 – 37.0

C18:2 6.6 – 11.9 10.4 – 13.4 3.2 – 9.8

C18:3 0 – 0.5 0.1 – 0.6 0.1 – 0.6

C20:0 0 – 0.8 0.2 – 0.5 0.1 – 0.6

Iodine value 50.6 – 55.1 56.1 – 60.6 21.6 – 49.4

Slip point (oC) 32 – 39 19.4 – 23.5 44.5 – 56.2

Cloud point (oC) - 6.6 – 11.5 - Source: (Pantzaris, 1995; Tan and Flingoh, 1981)

Table 2.6 Triglyceride compositions of palm oil products

Carbon number Palm oil Palm olein Palm stearin

C46 0.4 – 1 - 0.5 – 3

C48 5 – 11 1.3 – 4.0 13 – 56

C50 40 – 45 37.7 – 45.4 34 – 50

C52 38 – 44 43.3 – 51.3 5 –37

C54 6 – 11 7.0 – 12.6 Tr – 8 Source: (Pantzaris, 1995; Tan and Flingoh, 1981)

Basiron (1996) found that the ranges of palm oil application in foods were

shortening, margarine, vanaspati, deep-frying fat, and specialty fats (Figure 2.6).


The contribution of palm oil to world food supplies has increased steadily in

the last 20 years and its position as a major commodity in the world trade was expected

to continue. However, consumers’ awareness of palm oil use in human nutrition was

rather low. The Malaysia Palm Oil Promotion Council has therefore invited a group of

professional scientists from a range of appropriate disciplines, to carry out an objective

review, based on an evaluation of the published information in the scientific literature

(Anon, 2000). This review is here presented as 15 facts are:

Fact 1

Palm oil is one of the sixteen edible oils processing on FAO/WHO Food

Standard under the Codex Alimentarius Commission Programme.

Fact 2

Palm oil has had a long history of food use dating back over 5,000 years.

Fact 3

Presently it is consumed worldwide as a cooking oil, in margarine and

shortening and is also incorporated into fat blends and a wide variety of food products.

Fact 4

Palm oil contains an equal proportion of saturated and unsaturated fatty acids.

Fact 5

Palm oil is prepared from the fresh palm fruit by cooking and processing only.

It should be clearly distinguished from palm kernel oil and coconut oil, because it has a

lower level of saturated components, with no significant content of capric, lauric, and

myristic acids.

Fact 6

Current food labeling regulations were classified palm oil like all other

vegetable oils, as cholesterol free.

Fact 7

For most food uses palm oil does not require hydrogenation, thus avoiding the

formation of Trans-fatty acids, and uncommon cis-fatty acids found in hydrogenated

oils.


Fact 8

Refined palm oil, as used in foods, is rich source of tocopherols and

tocotrienols having vitamin E activity. Unrefined palm oil is also a rich source of

carotenoids.

Fact 9

Like other common edible fats and oils, palm oil is readily digested, absorbed

and utilized as a source of energy.

Fact 10

A number of recent controlled human effect studies in Europe, USA, and Asia

have confirmed that there is no significant rise in serum total cholesterol when palm

oil, providing most of the dietary fat, is used as an alternative to other fats in the

habitual diet.

Fact 11

In the above-mentioned studies the level of HDL cholesterol, regarded as

beneficial, was unaltered or significantly enhanced.

Fact 12

The content of lipoprotein in blood plasma, a potent risk indicator of coronary

heart disease, was significantly reduced when palm oil provided most of the dietary

fat.

Fact 13

Not all saturated have the same effect on plasma cholesterol concentration.

Fact 14

Dietary palm oil performs comparably with other more unsaturated oils when

studied in a rat model of arterial thrombosis.

Fact 15

As compared with a number of other edible oils, dietary palm oil reduces the

number of chemically induced tumors in rats.


Figure 2.6 Palm oil utilization chart Source: (Basiron 1996)

Fresh fruit bunches

Mill process

Kernel Crude palm oil Fruit residues

Refining

Fractionation and refining Splitting

Fatty acids GlycerolRBD PO

RBD Olein RBD Stearin

Fatty alcohols, amines, amides

EmulsifiersHumectant Explosives

MargarinesShorteningsVanaspati Frying fatsIce cream

ShorteningsMargarinesVanaspati

Palm midfraction

Blending

Cocoa butter equivalent

Confectioneries

Soap

Splitting

Fatty acids

Soap Food emulsifiers

Frying Cooking

Shortenings Margarines


2.2 Rice bran oil Rice bran oil, also called rice oil, the by-product from rice milling. The oil has

been used extensively in Asian countries such as Japan, Korea, China, Taiwan,

Thailand, and Pakistan (Orthoefer, 1996a). Rice bran oil is generally considered to be

one of the highest quality vegetable oil available in term of its cooling qualities, shelf

life, and fatty acid composition (Hargrove, 1994).

Orthoefer (1996b) reported that the bran and polish, the source of rice bran oil

was derived from the outer layers of the rice caryopsis during milling. Rice bran oil

usually contains palmitic, oleic and linoleic fatty acids constituting more than 90% of

the fatty acid portion of the glycerides (Table 2.7). However, the major molecular

species of rice bran oil triglycerides were palmitic-linoleic-oleic, oleic-linoleic-

palmitic, palmitic-linoleic-linoleic, linoleic-linoleic-palmitic, and finally triolein.

Rice bran contains several enzymes. Lipase has been the major type enzyme

and affected the keeping quality, and the subsequent industrial usage of the rice bran.

Lipase predominately promoted hydrolysis of the oil in bran into glycerol and free

fatty acid (FFA). The rate of FFA development was quite high and directly depended

on environmental condition. FFA developed about 5-7% per day and up to 70% FFA

for a single month during storage (Orthoefer, 1996b).

Hargrove (1994) reported that there were many potentially suitable methods to

stabilize or inactivate the lipase in rice bran. Most commercial systems currently

utilized in the united state employed the moisture added or dry extrusion methods.

The bran temperature maintained at 90-100oC, after extrusion for 2-3 minutes prior to

cooling. After the extrusion stabilization, bran could be produced that would remain

stable under normal warehouse storage for maximum six months but refrigerated

storage was able to extend the shelf life significantly.


Table 2.7 Typical fatty acids composition of rice bran oil

Fatty Acids Weight (%)

C14:0 Tr

C16:0 16

C18:0 2

C18:1 42

C18:2 38

C18:3 1.4

C20:0 0.6 Source: (Hargrove, 1994)

Nicolosi et al. (1994) and Orthoefer (1996b) found that oil easily removed from

the bran using hydraulic pressing and/or solvent extraction (Figure 2.7). Extraction of

the oil may be carried out with a variety of solvents, although hexane is generally used.

Rice bran for solvent extraction may be steamed for stabilization and to facilitate pellet

or collate formation for higher solvent per collation rate leading to shorter extraction

time. The extraction usually may be divides into a batch type or continuous extractor.

The solvent plus oil, referred to as micella, is filtered prior to distillation of solvent.

The wet defatted bran is desolvented, dried, and cooled. The solvent is recovered

throughout the process. However, crude rice bran oil is dark greenish brown to light

yellow, depending on the condition of the bran, extraction method, and composition of

the bran.

The products of extraction may consist of defatted bran, crude rice bran oil,

wax, and soap of fatty acid. In refining process (Figure 2.8), the processes used to

preparation of food oils consist of dewaxing, the simplest technique to remove the wax

from crude rice bran oil is to use settling tanks in which the crude oil is gradually

cooled, followed by filtering or centrifuging (Orthoefer, 1996b).


Rice bran mill

Stabilization

Drying

Storage

Hexane extraction

Meal desolventizing Hexane distillation

Defatted meal Crude rice bran oil

Figure 2.7 Rice bran oil extraction process

Source: (Nicolosi et al., 1994)


Crude rice bran oil

Phosphoric acid

Water

Deguming Phospholipids

NaOH

Neutralization Fatty acid soap

Acid activated

Bleaching earth

Bleached oil

Deodorization Vegetable oil

Distillated

Rice bran oil

Figure 2.8 Rice bran oil refining process

Source: (Nicolosi et al., 1994)


Nicolosi et al. (1994) presented that the degumming process generally used of

degumming agents such as phosphoric or citric acid to hydrolyze at 60-80oC. The wet

gum was separated from the oil by centrifugation. Acid degumming was usually

combined with neutralization with sodium hydroxide, at temperature less than 65oC.

Free fatty acids presently were converted to sodium soaps, being hydratable and

removable by centrifugation. Bleaching of the oils was carried out to remove

pigments, oxidized lipids, and polar component from the oil. Acid activated bleaching

clay was removed by filtration. Finally, to removed of odors, flavors, and fatty acid by

steam distillation or deodorization at 220-225oC, 4-8 mmHg. The volatile compounds

including aldehydes, ketones, and peroxide could be removed from oils. After

deodorization, the rice bran oil was cooled to 10-14oC prior to storage (Table 2.8).

Table 2.8 Characteristic of refined rice bran oil

Characteristic Quality

Iodine value 99-108

Saponification value 180-190

Smoke point 213oC

Fire point 352oC

Cloud index 17oC

Refractive index 25oC 1.470 – 1.473

Specific gravity 25/25oC 0.916 – 0.921

Unsaponifiable matter 3-5%

Total tocopherol 200 mg/kg (0.02%) Source: (Hargrove, 1994)

Winterization was performed to remove the high melting triglyceride from the

fractions, the oil remained liquid at refrigeration temperature. The oils was winterized

by slowly cooling the oil to 5oC and holding for up to several days. The saturated

glyceride crystallize could be removed by filtration producing a stearin (high melting

fraction and rice oil (low melting fraction) (Nicolosi et al., 1994). The composition of

rice bran oil suggested that it could be used as a salad oil and for cooking. Therefore,


it had excellent oxidation stability, because it contained the natural tocopherol

(Sonntag, 1979).

Diack and Saska (1994) and Roger et al. (1993) found that fully processed rice

bran oil contained a high amount of unsaponifiable component compared to most other

vegetable oils. Two groups of components found in the unsaponifiable fraction of rice

bran have been investigated for possible health benefit, such as the tocotrienol and the

γ-oryzanol. Although, their concentrations substantially depended on the origin of the

rice bran.

Rice bran oil was used for both edible and industrial application. As only high

quality rice bran oil was used for foods. The oxidative stability of rice bran oil was

equivalent to or better than soybean, corn, canola, cottonseed, and safflower oils in

deep frying condition. Winterized rice bran oil was suitable for making mayonnaise

and salad dressing. The stearin separated during winterization could be used in

margarine and shortening application (Orthoefer, 1996b).

2.3 Blended oil The blending, mixing two or more straight or modified oils and fats, could be

the correct balance of properties such as melting point, plastic range, color, texture,

iodine value, etc (Berger, 1982). Consequently, blending was the simplest method

used to modify oils and fats for some specific applications (NorAini et al., 2001).

In tropical countries, palm olein were sold in supermarket or retail shops for

general household cooking and frying which might have a preference for a particular

flavor and taste. Palm olein could easily be blended with other oils such as groundnut

oil and sesame oil that had proved to be very popular in China as household frying

oils. The blends of palm olein with soybean oil provided oil with a balance ratio of

polyunsaturated, monounsaturated, and saturated fatty acids as recommended by some

health organizations. The new cooking oil was recently introduced in the local market

under the brand name of DAISY. This cooking was the blend of palm olein with

sunflower seed oil and canola oil (Razali and NorAini, 1994).

In Egypt, cottonseed oil was the major vegetable oil; it comprised 79.6% of the

total oil production. Recently, palm olein has been intensively used in Egypt as a

frying medias due to high oxidative stability and low price as compared to other


similar frying media. Blending of cottonseed oil with palm olein also improved the

frying performance (Mostafa et al., 1996). However, the palm olein was blended with

high polyunsaturated fatty acid such as SBO and SFO to increase the cold stability and

frying performance (Basoglu et al., 1996; Chu, 1991).

In 1992, Uniliver in Italy using palm olein as the main component blended with

sunflower seed oil and groundnut oil. The product was sold in Italian supermarkets

under the brand name of FRIOL. Blending of palm olein with other polyunsaturated

oil it was a good practice because the final blended oil had a better frying performance

when compared with the polyunsaturated oil alone (Razali and NorAini, 1994)

2.4 Crystallization of fats and oils Crystallization, it was necessary to increase the concentration of the solute to

be crystallized above the saturated solution concentration at a given temperature,

called supersaturated. A crystal nucleus was the smallest crystal that could exist in a

solution of a certain concentration and temperature. Aggregates of molecules smaller

than nucleus were called embryos and would redissolve if formed. When molecules

came together to form a crystal, there were two opposing forces. Firstly, energy was

evolved due to the heat of crystallization, which flavour the process. Secondly, the

surface of the crystal increased as the molecules aggregated together, called nucleation.

A crystal nucleus had formed; it would start growing by the incorporation of other

molecules, called crystal growth (Timms, 1995).

The most common types of fat crystals were the three systems such as, the

triclinic system, called beta (β). It was the most stable polymorphic form, the common

orthorhombic system, called beta prime (β′). It had intermediate stability, and the

hexagonal system, called alpha (α), the least stable polymorphism form (Newar,

1996).

Palm oil consisted of 50% saturated and 50% unsaturated fatty acids. The

major triglycerides, according to equivalent carbon number were C50 (42.58%) and

C52 (40.46%) (Cheman, 1999). The major diglyceride is C34 (54.4%), C36 (33.0%),

and C32 (12.6%). The diglyceride in palm oil affected the physical properties such as

crystallization and melting point. Also, slow down transformation of the crystals form


the α form to β′ form and subsequently, to the β form (Sambanthamurthi et al., 2000;

Siew and Ng, 1995; Siew and Ng, 1996a).

The major triglycerides of the olein fraction were C50 (42.04%) and C52

(45.66%). The stearin fraction consisted of C48 (22.3%), C50 (40%), and C52 (29%)

(Cheman, 1999). Palm olein tended to crystallize at low temperature. This

crystallization caused the cloud formation, sometimes observed as white sediments at

the bottom of the containing. The visual observation of these crystals was often seen

as a defect to consumers and there was no deterioration in oil quality (Siew and Ng,

1996).

Clouding was obtained after storing palm olein at 12.5oC for 12 to 24 hours and

easily separated by centrifugation. Palmitic-oleic-palmitic or POP and palmitic-oleic-

stearic or POS levels were high in the cloud material (Swe et al., 1994). The

composition of purified palm olein crystal formed at room temperature (25oC) was

identified. In addition, the major 1,3-dipalmito-glycerol was the high melting

glycerides (Swe et al., 1995). GC and HPLC analyzed the composition of the crystal

obtained during the storage of palm olein between 28oC and 10oC. The crystals were

the beta form, and consisted of high and low melting component. Although, the high

melting component mainly 1,3-dipalmitin. The mainly low melting components were

tripalmitin and dipalmitin (Siew and Ng, 1996).

Some vegetable oils form sediment or a cloudy haze during storage at room

temperature such as palm olein, canola oil, and sunflower seed oil. Among the

component implicated in turbidity formation were saturated triglyceride, waxes, free

fatty acid, hydrocarbon, sterol and their ester, and fatty alcohol (Przybylski et al.,

1993; Rivarola et al., 1985).

The higher cloud point of palm olein, compared to any other liquid oil, has

been a problem over years and partially overcome by blending, adding additives or

using a double fractionation method, but the problem still resists (Swe et al., 1994).


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29

CHAPTER 3

Resistance to Crystallization of Palm Olein Blended with

Rice Bran Oil

Abstract

The resistance to crystallization of palm olein (PO) blended with rice bran oil

(RBO) in various proportions was investigated via monitoring the changes in cold test

and cloud point during the storage. All blended oils were continuously kept at 3

different temperatures (15oC, 20oC, and room temperature; RT about 32oC).

Regarding to the cold stability test, the blends of 40% to 60% RBO kept at 20oC and

RT except at 15oC still remained visually clear after 30 days. All blends of both oils

did not pass the cold test. The cloud points of the blends significantly (p<0.05)

decreased to 5.4oC with increasing the ratio of RBO. It was observed that the addition

of RBO intensively retarded the fat crystallization and the optimum blends of both oils

(PO: RBO) was recommended as 40:60.

Keywords: crystallization, palm olein, rice bran oil, cold stability, cloud point

Chapter 3: Resistance to crystallization of palm olein blended with rice bran oil 30

Introduction

Palm olein (PO) is the liquid fraction usually received from the fractionation

step in the palm oil production (Pantzaris, 1995). It is widely recommended for

cooking and frying processes in both food service institutions and industry due to its

heat stability (Anon, 1991; Basiron, 1996). As a result of containing about 46% of the

saturated fatty acid, palm olein has the tendency to crystallize at low temperature or

during long storage period at room temperature (Basiron, 1996). The changes in oil

appearance could be sometimes observed as the white crystals at the bottom of the

bottle (Siew and Ng, 1996). Swe et.al. (1994) reported that the POP and the POS

triglycerides were the major constituents in the cloud materials occurring within PO

after stored for 15-16 hours at 12.5oC. The visual observation of the fat crystals was

often notified as an important defect and misjudged by consumer (Basiron, 1996).

However, the fat crystals formation or the cloud materials of PO absolutely did not

conduct the deterioration and affected the oil quality (Siew and Ng, 1996a).

Few available procedures were explored to retard the white crystal formation at

the oil bottles, for instance, the application of double fractionation, the addition of the

crystal inhibitors, and the blending with different vegetable oils (Basiron, 1996;

Mostafa et al., 1996). The oil blending was the simplest method to modify the oil

properties for the specific application. PO was occasionally blended with other oils

containing high unsaturated fatty acid such as soybean oil, sunflower seed oil, and etc.

(Basoglu et al., 1996; NorAini et al., 2001).

In an earlier study, Teah and Ahmad (1991) reported that the blends of

sunflower seed oil (SFO) with 50% to 70% single fractionated PO would improve the

crystallization temperature down to at 10oC. In addition, they also found that a blend

of 30% double fractionated PO with 70% SFO would be suitable for climate

temperature. NorAini et al. (1992) determined the resistance to crystallization of PO

with soybean oil (SBO) at different temperatures. They reported that PO of iodine

value (IV) 65 had more ability to form fat crystals than PO IV60 or IV 63. Their study

also showed that in the applications such as salad oil, the addition of PO IV65 was able


to blend upto 30% with SBO while the use of PO IV60 or IV63 was limited to only

10% of blended oil.

Rice bran oil (RBO) was generally considered to be one of the highest quality

vegetable oils available in term of its excellent cooking quality, shelf life, and fatty

acid compositions (Hargrove, 1994). In general, it contained 40% polyunsaturated

fatty acid, 40% monounsaturated fatty acid, and 20% saturated fatty acid (Orthoefer

1996). In addition, RBO naturally consisted of the tocotrienol and γ-oryzanol to

excessively prevent the oxidation during frying at the high temperature (Sonntag,

1979).

Accordingly, this works was carried out to prepare the different blends of PO

with RBO and study their resistance to the fat crystallization as well as cold stabilities

measured by the cold test and cloud point.

Materials and Methods

The experiments were conducted with 100% single fractionation palm olein

(PO) (IV 56-58) obtained from Oleen Co., Ltd., Thailand for edible oil processing

company. The pure rice bran oil (RBO) using King brand from Thai edible oil Co.,

Ltd., Thailand were purchased from local supermarket.

Oil blending procedure

The pure PO and RBO were heated up to 60oC using hot plate (Thermolyne:

type Cimerac 2, Thermolyne Cooperation, USA) and then filtered through a Whatman

qualitative filter paper No. 4 (Whatman International Ltd., Maidstore, England). The

filtered oils were differently blended to various PO:RBO proportions (w/w) including

0:100 (pure RBO), 40:60, 45:55, 50:50, 55:45, 60:40, and finally 100:0 (pure PO).

Each of blended oil samples was filled into the 4 oz. glass bottle Regarding to NorAini

et al. (1995), all bottled oil samples were heated to 70oC for 1 hour to destroy any

crystal nuclei that might be presented using the hot air oven (Memmert, model 600,

Memmert GmbH Co.KG, Germany). The blended oils were allowed to cool to room

temperature and then covered with the plastic caps. Each of blended oil samples was

divided into two groups for further experiments.


To study the resistance to fat crystallization, the first group of the blends was

separated to store at 3 different temperatures (consisting of 15oC, 20oC and room

temperature; RT about 32oC) using the control temperature cabinets (P. Chemical Ltd.,

Thailand). Referred to the graphical methods proposed by NorAini et al. (1995), the

blends of both oils were periodically observed by visual inspection every 5 days for 30

days and graphically recorded the changes in physical properties with respect to the

crystal formation stages appearing in the container.

Cold test and Cloud point testing

The cold stability of the blends was determined using the cold test (AOCS,

method Cc 11-53) and the cloud point as described by AOCS method Cc 6-25.

The second group of blended oil samples was randomly measured the cold test

and kept in the ice bath with the control condition at 0oC for 5.5 hours to evaluate the

resistance to crystallization. This was commonly used as an index of either the

winterization of edible oil or the removal of tristearin. The oil samples must remain

clear after 5.5 hours at 0oC and was officially stated that the oil passed the cold test or

exhibited the positive response.

The cloud point was measured as the temperature at which a cloud occurring in

visual appearance was induced in the oil sample caused by the first stage of

crystallization.

Statistical analysis

All data were subjected to analyze the variance using General Linear Model

(GLM) and Least Significant Difference (LSD) at 5% confidence level was performed

to determine the difference among mean using SAS procedure (Ver. 8.1, SAS Inst.,

Cary, NC, USA).

Results and Discussion All the blended oils of PO with RBO exhibited the negative results measured

using the cold test at 0oC for 5.5 hours (Table 3.1). Therefore, all the blends and both

pure oils (including PO and RBO) could not resist the formation of fat crystals at

relatively low temperature and still not pass through the cold test since the major


composition of triglycerides and related compounds such as fatty acids and partial

glycerides were most of saturated fatty acids constituted in the single fractionated PO

(IV 56-58) and some saturated contents of RBO significantly affected the crystal

growth. Regarding to the interactions between triglycerides and diglycerides in PO,

the diglycerides were intensively able to deteriorate the PO during the crystallization.

Even though, the addition of RBO was unable to inhibit fat crystal formation, the

changes in oil compositions may attempt some benefits to improve the oil thermal

stability.

The cloud points of the blends ranged from 4.9-5.8oC (18% total difference) as

shown in Table 3.1. However, all blends containing 40 to 60% RBO remarkably

(p<0.05) decreased the cloud point as compare to 7.8oC of the pure PO. The reduction

of the cloud point may contribute upon the modification of unsaturated contents in the

blends because RBO normally contained greater unsaturated fatty acids, especially

oleic acid (C-18) up to 80%. This caused the dilution of fat crystal formation due to

lower saturated fatty acid in the blends (Orthoefer 1996). Few researchers had studies

the blends of oil containing greater unsaturated fatty acid oil such as SBO with low-

erucic acid rapeseed oil (LEAR) and reported the same results (NorAini et al., 1992;

NorAini et al., 1995).

Higher cloud point of PO as compared to any other liquid oils has continuously

been a visual problem over the years and has overcome by blending with unsaturated

oils, adding additives or using a double fractionation (Swe et. al., 1994). Thus, the

resistance to crystallization of single fractionated PO blended with RBO was strongly

recommended to solve this problem. At 15oC, the blends (PO:RBO) in all interested

proportions except the pure RBO continued forming the fat crystals at the bottom of

the containers after 5 days of storage and substantially developed abundant fat crystals

that would result in the final semisolid within 30 days. However, the pure (100%)

RBO also first formed the clouding point at 10 days (Figure 3.1a). The crystallization

of the blends was usually accelerated with high proportions of PO at the low

temperature since the single fractionated PO comprised high-saturated fatty acid.

Several researches indicated that the fat crystallization was generated with respect to

the early nucleation of some certain high melting glycerides (Swe et al., 1994; Swe et

al., 1995). According to several studies, they found that the major components causing


the clouding of PO were POP, POS, and diglycerides particularly 1,3 PP (Siew and

Ng, 1996a; Siew, 2002; Swe et al., 1994; Swe et al., 1995). After 10-15 days of

storage at 15oC, the oil samples created some tiny particles at the bottom and the pure

PO was entirely solidified as shown in the Figure 3.1b-3.2a. On 20 days, the blends

with 50% and 60% PO developed the semi-solid whileas the blends with 45% PO was

visually observed to be only cloudy (Figure 3.2b). At 30 days, all oil samples with

high PO completely set to solid state only except the pure RBO and the blend in

proportions PO:RBO (40:60) still displayed the tiny particle (Figure 3.3b). In general,

the crystallization behavior of the blended oils based on the polymorphism of fat and

the nucleation of triglyceride crystals gradually formed after long period of storage

(Siew and Ng, 1996a; Siew and Ng, 1996b; Siew and Ng, 1996c; Swe et al., 1995).

Therefore, the removal or inhibition of the crystals formation would be essential to

improve the oil quality and appearance.

At 20oC and RT, all the blends and the pure oils existed completely clear

throughout 30 days (Figure 3.1-3.3) due to high temperature storage. In general, the

pure PO was completely clear at temperature between 22-25oC but exhibited

cloudiness and sedimentation at low temperature (Siew, 2002). Regarding to this

experiment, the blends of PO with RBO kept at 20oC and RT significantly impeded the

fat crystallization and was capable to achieve the persistent problem of PO during the

distribution in the oil market.

Conclusions All various blends of PO with RBO were unable to retard the fat crystal

formation at relatively low temperature (at 0oC, 5.5 hours) and still not pass through

the cold test. The cloud points of the blends ranged from 4.9-5.8oC and remarkably

(p<0.05) decreased with greater %RBO addition. The blends of PO with various

proportions (40% to 60%) of RBO extensively resisted the fat crystallization and still

remained transparently clear during 30 days of storage at 20oC and RT. In contrast,

the blends kept at 15oC could not prevent the clouding formation due to the hard

melting triglycerides crystals. Therefore, the blends of both oils could be the potential

future product utilized in the food manufacturing.


References Anon. 1991. Palm oil in the diet. In: Palm oil and human nutrition. Selangor. Palm

Oil Institute of Malaysia (PORIM). p 15-18.


Improved quality of cooking and frying oil by blending palm olein. In: Word

Conference and Exhibition on Oilseed and Edible Oils Processing. Vol 1.


Basiron Y. 1996. Palm oil. In: Hui YH, editor. Bailey’s Industrial Oil and Fat

Products. Vol 2. New York: John Wiley and Sons. p 271-375.

Hargrove KL Jr. 1994. Processing and utilization of rice bran in the United

States. In: Marshall WE, Wadwurth JI, editors. Rice Science and Technology.

New York: Marcel Dekker. p 381-400.

Mostafa MM, Rady AH, Faried A, El-Egieul A. 1999. Blending of palm olein with

cottonseed oil. In: Proceeding of the 1996 PORIM International Palm Oil

Congress, (chemistry and technology). Malaysia. p 286-300.

NorAini I, Razzali I, Habi N, Miskandar MD, Miskadar MS, Radauan J. 2001. FTN2:

Blending of palm products with other commercial oil and fats for food

applications. In: 2001 PIPOC International Palm Oil Congress Food

Tecnology and Nutrition Conference. Malaysia. p 13-22.

NorAini I, Hanirah H, Flinguh CH Oh, Sudin N. 1992. Resistance of crystallization

of blends of palm olein with soybean oil stored at various temperatures. J Am

Oil Chem Soc 69(12):1206-1209.

NorAini I, Hanirah H, Sudin N, Flingoh CH SH, Tang TS. 1995. Clarity of blends of

double-fractionated palm olein with low-erucic acid rapeseed oil. J Am Oil

Chem Soc 72:443-448.


Pantzaris TP. 1995. Pocket book of palm oil uses. Palm Oil Research Institute of

Malaysia. Kaula Lumphur. Malaysia. 158 p.

Siew WL, Ng WL. 1996a. Characterization of crystals in palm olein. J Sci

Food Agri 70:212-216.


Siew WL, Ng WL. 1996b. Effect of diglycerdes on the crystallization of palm

olein. J Sci Food Agri 71:496-500.

Siew WL, Ng WL. 1996c. Crystallization behavior of palm oleins. Elaeis 8(2):75-82

Siew W L. 2002. Understanding the inter actions of diacylglycerols with oils for

better product performance. Palm Oil Dev 36:6-12.

Sonntag NOV. 1979. Composition and characteristics of individual fats and oils:

rice bran oil. In: Swern D, editor. Bailey’s Industrial oil and fat products

Vol 1. 4th ed. New York: Wiley and Sons. p 407-409.

Swe PZ, CheMan YB, Ghazali HM. 1995. Composition of crystals of palm olein

formed at room temperature. J Am Oil Chem Soc 72(3):343-347.

Swe PZ, CheMan YB, Ghazali HM, Wei LS. 1994. Identification of major

triglyceride causing the clouding of palm olein. J Am Oil Chem Soc

71(10):1141-1144.

Teah YK, Ahmad I. 1991. Palm olein improves cooking oil blends. Palm Oil Dev.

15:2-8.


Table 3.1 Changes in cloud points and cold test of PO blended with RBO

Ratio Cloud points Cold test*

PO:RBO (oC) (0oC; 5.5 hour.)

0:100 4.0±0.1 Negative

40:60 4.9±0.2 Negative

45:55 5.0±0.3 Negative

50:50 5.3±0.1 Negative

55:45 5.5±0.1 Negative

60:40 5.8±0.4 Negative

100:0 7.8±0.4 Negative

* Negative: Did not pass through cold test according to AOCS Cc 11-53


(a)

(b)

RT = room temperature

Figure 3.1 Physical characteristic of palm olein blended with rice bran oil stored at

various temperatures on day 5 and day 10.


(a)

(b)





(a)

(b)




41

CHAPTER 4

Thermal Stability of Palm Olein Blended with Rice Bran Oil

Abstract

The frying performance of palm olein (PO) blended with rice bran oil (RBO) in

various proportions was evaluated by means of monitoring their chemical and physical

changes over 40 hours of heating and intermittent frying of potato chips. Regarding to

official oil quality indexes, free fatty acid content (%FFA), peroxide value (PV),

viscosity, and overall color difference (∆E) of all blends intensively elevated (p<0.05)

with longer time due to the deteriorative process. In contrast, the smoke point

adversely decreased (p<0.05). The additional RBO in PO remarkably displayed

(p<0.05) better thermal stability and frying performance with respect to its naturally

abundance of γ-oryzanol and tocotrienols. The blends of both oils beneficially

improved (p<0.05) the oxidative stability. Conclusively, the most appropriate

PO:RBO ratio probably was 50:50. After 40 hours of heating, the viscosity, %FFA,

and PV of the blends at 50:50 were relatively lower by 5.1%, 36.5%, and 4.2%

respectively, and the smoke points exhibited notably higher (1.69%) than the ones in

100% PO.

Keywords: thermal stability, palm olein, rice bran oil, blended oils, deterioration

Chapter 4: Thermal stability of palm olein blended with rice bran oil 42

Introduction

During the deep fat frying, the frying oils used continuously or repeatedly at

high temperatures in the presence of oxygen and water from the wet foods, were

abused via thermal oxidation, polymerization, and hydrolysis. The resultant

decomposition products adversely affected the flavor and color of both fried products

and oil (Clark and Serbia, 1991; White, 1991). Thus, the thermal stability and frying

performance of frying oil normally be considered as one of the most criteria to

appropriately select the types of oil used in the frying process (Fauziah et al., 2000).

In addition, the customers regularly bought the oil with respect to its nutritional value,

availability, price, flavor, and stability during storage (Mostafa et al., 1996). Thus, the

excellent frying oil must perform the excellent ability in oxidative stability, flavor

stability, taste, nutritional values (Xu et al., 1999).

Normally, the frying manufacturers substantially utilized palm olein (PO) as a

frying medium due to its unique chemical compositions and good oxidative stability

(Teah and Ong, 1988; Mostafa et al., 1996). PO, the liquid fraction of palm oil,

normally comprised largely of 46% of saturated, 43% of monounsaturated, and 11% of

unsaturated fatty acids (Sambanthamurthi, 2000). In addition, PO was remarkably

composed of about 1000 ppm of vitamin E and one-third of which were tocopherols

and two-third were the unsaturated analogues, tocotrienols (Mostafa et al., 1996).

These abundant substances have been demonstrated to display better cooking and

frying performance than most of the liquid vegetable oils.

As a result of high-saturated content, PO consequently solidified and partially

formed visually cloudy suspension of fat crystals normally seen in the container after

long storage at room temperature (Siew and Ng, 1996a). Consumers usually

associated clouding with low quality cooking oil since they required the cooking oil

remaining clear and transparent at room or lower temperature storage. This has been

limited the shelf storage during distribution. It has been well known that blending of

PO with high-unsaturated content such as RBO or SFO may improve the physico-

chemical properties and stability (NorAini et al., 2001; Yoon et al., 1987). In fact,

extensive quantities of blended oils presently are used for cooking, frying and

manufacturing of salad dressings.


Rice bran oil (RBO), also called rice oil, remarkably possesses the excellent

frying performance, good stability and also contributes a pleasant flavor to the fried

food (Maccaskill and Zhang, 1999). Normally, RBO contains approximately 40%

polyunsaturated, 40% monounsaturated, and 20% saturated fatty acid, and higher

concentration of unsaponifiables such as γ-oryzanol and tocotrienols. RBO presently

is one of the most important qualities of cooking oil used extensively in Asian

countries (Orthoefer, 1996). Haumann (1996) reported that the ideal frying oil would

be a low saturated, ultra high oleic (90% or greater) and very low linolenic (less than

0.5%) fatty acid contents.

Several studies (Kochhar, 2000; Haumann, 1996) found that the stable and

healthful frying oil was commercially formulated under brand Good Fry Oil containing

the main component of high-oleic sunflower seed oils. Its excellent oxidative and

flavor stabilities dealing with the additional small portion of sesame seed oil and rice

bran oil were substantially beneficial effects to use as industrial frying and cooking oil.

Basoglu et al. (1996) determined the frying performance of the double-fractionated

palm olein (IV 60) blended with sunflower seed oil (SFO) and soybean oil (SBO) and

indicated that the blends effectively improved better frying performance than the pure

ones. The addition of SFO and SBO in PO achieved to gradually darken the oil color,

increase free fatty acid content, and decrease the smoke point. Mostafa et al. (1996)

also reported that the blends of PO with cottonseed oil dramatically improved the

oxidative stability and prolonged shelf life of the fried products.

The objectives of this study were conducted to examine the changes in physical

and chemical properties of various blends of PO with different RBO with respect to

heating and frying tests and to evaluate the optimum ratio of the blended oil providing

better performance as a frying medium or cooking oil.

Materials and Methods The experiments were conducted with 100% single fractionation palm olein

(IV 56-58) obtained from Oleen Co., Ltd., Thailand for edible oil processing company.

The pure rice bran oil (RBO) using King brand from Thai edible oil Co., Ltd.,

Thailand were purchased from local supermarket.


Oil blending preparation

The PO and RBO were heated up to 60oC using hot plate (Thermolyne: type

Cimerac 2, Thermolyne Cooperation, USA) and then filtered through a Whatman

qualitative filter paper No. 4 (Whatman International Ltd., Maidstore, England). The

filtered oils were differently blended to various PO:RBO proportions (w/w) including

0:100 (pure RBO), 40:60, 45:55, 50:50, 55:45, 60:40, and finally 100:0 (pure PO).

The prepared blends were used in further heating and frying tests.

Heating experiment

A 900 ml of blended oil was subjected to continuous heating process at 180oC

using an electrical hot plate (Thermolyne: type Cimarec 2, model 46920-26,

Burnshead/ Thermolyne Cooperation, USA) for 40 hours. The heating schedule was

run for 5 days, and 8 hours per day. Approximate 100 g of treated oil was randomly

taken periodically after 8, 16, 24, 32, and 40 hours, respectively and then kept in the

cold storage at 4oC before further physical and chemical analyses. During heating test,

no fresh oil was added into the vessel to maintain the oil level. All experiments were

performed in triplicate.

Frying experiment

The fresh potatoes purchased from the local supermarket were washed with

soft water at room temperature, peeled, and then sliced to thickness of 2 mm. All

sliced potatoes were immediately kept in plastic bags for frying experiment.

A 3000 g of each blended oil (PO and RBO) was heated in a batch deep fat

fryer (Princess, model 2627WA, Princess Household Applied Co., Ltd, Netherlands).

A 100 g of the slices was fried in the batch fryer at 180oC for 2 min. The frying cycle

was every 20 min and twenty-four batches of the sliced potatoes were continuously

fried daily (8 hours/day) for 5 days. At the end of daily frying operation, the fryer was

switched off and the oil temperature was allowed to equilibrate to room temperature

for overnight and then reheated in the next frying day.

A 100 g of oil sample was periodically withdrawn at 8, 16, 24, 32, and 40

hours, respectively, and then kept at 4oC before the further analyses. Fresh oil was not

added to the frying vessel until the experiment was finished.


Physical analysis

The changes in oil color were measured using Electric Lovibond Tintometer

model PFX190 covet 10-mm observer 2o illuminant D65 (The Tintometer Co., Ltd.,

England). The measurements were displayed in the unit of CIE (1976) system: L*

(lightness-darkness), a* (red-green), and b*(yellow-blue). The overall color difference

(∆E) was calculated to represent the color development because of thermally

detrimental oil.

The viscosity was measured using Brookfield viscometer model LVF100

(Brookfield Engineering Laboratories, Inc., USA) at 30oC, speed 50 rpm with the disk

spindle No.LV-2. The inclination of smoke point was estimated according to AOCS

Cc 9a-48.

Chemical analysis

The percentage of free fatty acid (%FFA) expressed as oleic acid content was

determined by alkaline titration according to AOCS Ca 5a-40. The peroxide value

(PV) was measured according to AOCS Cd 1-53.

Statistical analysis

All the data were subjected to analysis of variance using General Linear Model

(GLM) and Least Significant Difference (LSD) at 5% confidence level was performed

to discriminate the difference among means of PO:RBO proportions using SAS

procedure (Ver. 8.1, SAS Inst., Cary, NC, USA).

Results and Discussion Color Development of the blended oils (PO:RBO)

Generally, the fresh PO exhibited redder than the pure RBO with respect to

higher a* value of -6.0 and -7.6, respectively (Table 4.1). PO normally was known to

have a somewhat higher orange-red color as compared with the polyunsaturated oils

such as rice bran oil (RBO) and soybean oil (SO). This was an inherent property of

palm containing carotenoid pigments approximately 500-700 ppm (Basoglu et al.,

1996; Basiron, 1996). Several researches were explored the carotenoid compounds


that usually comprised most of α-carotene and β-carotene accounting for 90% of the

total catotenoids and the remaining substances included phytoene, lycopene, and

neurosporene (Basoglu et al., 1996; Sambanthamurthi et al., 2000). In the oil

manufacturing, the fresh PO was regularly measured as red and yellow units using

Lovibond instrument and was about 1 of redness and 7.2 of yellowness as compared

with SBO which showed 0.5 of redness and 3.3 of yellowness (Basoglu et al., 1996).

Thus, the pure PO color was normally darker than RBO in nature. Consequently, the

blending PO with RBO could improve the color of the blended oil due to the dilution

effect. During heating, both PO and RBO underwent (p<0.05) darker, redder, and

more yellow with longer time. As expected, all blends at every ratio progressively

impeded the rate of color changes, especially, in redness up to 16 hours of heating. In

frying experiment, there was not difference in overall color among the blends and the

pure ones (Table 4.2).

The overall color difference (∆E) of all blends increased up to 70% and 50%,

respectively, in heating and frying over 40 hours as shown in Figure 4.1-4.2. In

general, the heated oil intensively darkened during heating and frying due to its

degradation and oxidative reactions. The oxidized products subsequently breaking

down and generating a great variety of hydrocarbons and polymers resulted in the

darker color development. The color substances could dissolve in frying oil and make

the oil seem deterious (CheMan et al., 2003; Stevenson et al. 1984; Xu et al. 1999).

With a somewhat higher in red color, PO would start darkening at faster rate

than polyunsaturated RBO. However, this did not significant affect the color of the

fried potato. Thus, color alone was not conclusive in describing the oxidation state of

the oil. In addition, the blends with PO and RBO still contained the much more natural

antioxidants providing the great beneficial effect to prevent the oil deterioration.

Changes in viscosity

The viscosity of all blended oil samples gradually increased (p<0.5) over 40

hours during heating and frying tests (Figure 4.3-4.4). In general, the viscosity of all

blends and both pure oils tended to increase because of their oxidation and

polymerization. This could be explained by the formation of polymer compounds and

the tendency toward forming during heating and frying (CheMan et al., 2003). As


expected, the viscosity of RBO showed significantly higher than PO as compared to

the same periods of thermal processes. For example, after 40 hour of heating and

frying tests, the viscosity of RBO was measured as 100.5 cp and 101 cp, respectively,

which was greater than PO about 13.6% and 23.2%, respectively. Regarding to the

difference in fatty acid compositions, RBO naturally comprised most of substantially

higher unsaturated fatty acids such as linoleic acids and oleic acids tended to be rapidly

oxidized and form polymer compounds, for instance, dimmers, trimers, and tetramers

(Bracco et al., 1981). In contrast, PO normally contained largely of 46% of saturated,

43% of monounsaturated, and 11% of unsaturated fatty acids (Sambanthamurthi,

2000). While oxidation of saturated fatty acids generally produced various

hydrocarbons, carbonyls, and ketones, these products directly promoted the dark color

development but did not really affect the viscosity. The increase in viscosity of each

blend at various RBO proportions was obvious and fluctuated among themselves.

However, the lowest viscosity of the blends (PO:RBO) was in wide ranges of 45:55

and 50:50, respectively.

Thermal effects on smoke point

Normally, the frying oil would be considered to discard when its smoke points

was less than 170oC because of an excessive smoke formation in the environment and

health hazard concerns. The smoke points of all oil samples gradually decreased

during heating and frying over 40 hours due to the consequence of an increased in

polar components and the accumulation of low molecular weight decomposition

(LMWD) products (Augustin et al., 1987; Yoon et al., 1987). As expected, RBO

exhibited better physical resistance to decline the smoke points since it contain with

high-unsaturated contents as compared to the pure PO. After heating for 40 hours, the

smoke points of RBO and PO were 186oC and 176.7oC, respectively. It seemed that

RBO intensively resisted breaking down its constituents more superior (approximately

5.3%) than PO. In the end of frying experiment, the use of PO as frying medium

might be unacceptable with regard to lower smoke point than the industrial regulations

(as seen about 169.7oC). Thus, the blending PO with RBO provided the great

advantage to prolong the frying oil life in the fryer. In addition, the smoke points of all

blends in frying experiment were significantly lower than in heating test because the


majority of reactions took place in the hot oil was pyrolysis and oxidative degradation

and resulted in the accumulation of LMWD products such as carbonyls, hydrocarbons,

and partial glycerides. These results agreed with Basoglu et al. (1996) that attempted

to blend SBO and SFO with PO.

Deteriorative Stability of blends (PO:RBO)

Free fatty acid formation presently is the most important chemical index used

to decide the state of oil deterioration since it is very simple alkaline titration and cost

effective. Thus, almost the fried food manufacturers have been applied to monitor the

frying oil quality. The fresh and the blends used in both heating and frying all had

FFA contents below 0.12%. The FFA contents of all blends substantially increased

(p<0.05) as shown in Figure 4.7-4.8 due to hydrolysis and thermal cleavage. The fresh

PO displayed slightly higher value than the fresh RBO. Yoon et al. (1987) reported

that FFA of the fresh RBO used in their experiment was about 0.17 and finally reached

0.64 after 50 hours of heating, whereas that of double fractionated (DF) PO increased

from 0.23 to 1.30 in the same period and they also proposed that DFPO had a higher

free fatty acid than RBO. The FFA content from frying test was higher than heating

test since the moist foods regularly were fried and then existed the evaporation of

liquid water from foods to the hot oil (CheMan et al., 2003; Pantzaris, 1999). This

promoted the rapid rate of hydrolysis of triglycerides in the frying oil. Regarding to

the USDA regulations, it usually limited the FFA content not excess more than 2% in

meat products and 1% in fried snack foods. Thus, the suitable blending PO with RBO

at 50:50 notably employed to use for the fried food application.

The FFA of PO higher than RBO in both heating and frying because the

decomposition of the secondary oxidation products was created as peroxide value

(Figure 4.9-4.10). The FFA content of the PO: RBO proportions of 50:50 were the

lowest.

Peroxide value (PV) in all oil samples relatively increased within the 8 hour of

heating and frying and subsequently represented the constant tendency until 32 hour of

both heating and frying but suddenly sharp dropped after 40 hrs (Figure 4.9-4.10).

However, the differences in PV of all oils were not found (p>0.05). In addition, PV of

fresh PO was considerably higher (p<0.05) than that of RBO in the frying test.


Although, fresh PO naturally contains a great variety of abundant (about 500-700 ppm)

carotenoids such as tocotrienols, α-carotene, β-carotene, and lycopene, acting as a

source of antioxidants, these substances were relatively uncompatible with the

excellent antioxidative efficiency of γ-oryzanol and tocotrienols in RBO (Basoglu et

al., 1996; Sambanthamurthi et al., 2000). In general, peroxide molecules initially

formed were highly unstable and reacted quickly to form secondary oxidation products

(CheMan et al., 2003). As a result of PV measurement, the blending PO with RBO

provided the sufficient ability to suppress the peroxide formation during frying process

and the blend at 50:50 exhibited the best ability to prevent the peroxide formation.

Conclusively, the blended oil between PO and RBO at ratio of 50:50 was the most

appropriate blended oil to utilize as a new trend of cooking oil due to remarkable

thermal and oxidative stability.

Conclusions

The blending PO with RBO predominantly provided the synergistic ability to

retard the thermal and oxidative reactions during thermal process since the blends

represented better thermal stability and frying performance than the fresh ones. The

most appropriate ratio of the blended oil was 50:50 due to its ability to lower both FFA

content and PV by 57.4%, 4.42% in heating test and 46.7%, 131% in frying

experiments, respectively.


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Table 4.1. Changes in color value of palm olein blended with rice bran oil by heating

method

Scale Tim

e

100PO 100RBO 40PO: 45PO: 50PO: 55PO: 60PO:

Valu

e

(hrs) 60RBO 55RBO 50RBO 45RBO 40RBO

L* 0 93.2±0.

7

94.4±0.

1

95.2±0.

1

88.1±0.

5

92.0±3.

4

94.9±0.

2

94.3±0.

6

8 91.2±0.

3

94.1±0.

1

94.0±0.

1

85.7±0.

7

90.1±4.

0

93.7±0.

1

93.0±0.

8

16 90.9±0.

1

92.7±0.

4

92.6±0.

1

83.7±0.

7

88.3±3.

7

92.6±0.

1

92.2±0.

6

24 89.8±0.

4

91.5±0.

6

91.4±0.

2

81.2±0.

7

86.8±3.

9

91.5±0.

3

91.4±0.

2

32 88.4±0.

4

89.8±0.

6

89.4±0.

4

79.3±3.

6

86.4±0.

7

89.8±0.

6

89.7±0.

6

40 86.0±0.

7

87.7±0.

3

86.8±0.

3

75.0±0.

5

82.4±2.

0

87.5±0.

3

87.2±0.

8

a* 0 -6.0±0.1 -7.6±2.6 -6.4±0.3 -6.7±0.2 -6.4±0.2 -6.5±0.2 -6.4±0.1

8 -7.1±0.1 -7.1±0.6 -7.5±0.1 -8.5±0.1 -7.8±0.5 -7.3±0.1 -7.2±0.3

16 -8.3±0.2 -8.6±0.3 -9.0±0.1 -8.2±0.4 -8.4±0.2 -8.9±0.1 -8.8±0.2

24 -8.4±0.1 -9.5±0.3 -9.2±0.1 -6.6±0.5 -7.9±0.7 -9.2±0.2 -9.3±0.1

32 -7.0±0.4 -8.7±0.5 -7.1±0.3 -5.2±0.6 -3.4±1.7 -7.8±0.5 -8.0±0.4

40 -3.6±0.5 -5.6±0.3 -2.7±0.3 -1.7±1.1 -0.5±0.3 -4.7±0.3 -4.3±1.1

b* 0 21.7±1.

3

23.3±6.

4

20.2±0.

3

18.8±0.

1

20.0±1.

1

20.3±0.

1

20.2±0.

3

8 36.5±2.

7

23.7±1.

0

29.8±0.

6

38.2±1.

0

35.5±1.

7

30.4±0.

6

30.4±0.

9

16 43.9±2. 33.5±2. 42.3±1. 55.5±1. 51.3±1. 42.5±0. 41.1±0.


0 1 1 1 3 9 6

24 53.0±2.

7

45.1±2.

9

53.9±0.

6

69.8±1.

0

59.0±6.

2

52.6±2.

0

50.5±0.

5

32 64.4±1.

0

58.4±1.

8

67.1±0.

5

83.3±5.

5

77.6±5.

3

64.4±1.

5

62.5±0.

9

40 74.1±1.

1

70.4±0.

4

78.5±1.

0

89.9±6.

8

87.7±5.

9

74.5±0.

4

74.5±2.

0 n = 9


Table 4.2. Changes in color value of palm olein blended with rice bran oil by frying

method

Scal

e

Tim

e

100PO 100RBO 40PO: 45PO: 50PO: 55PO: 60PO:

valu

e

(hrs) 60RBO 55RBO 50RBO 45RBO 40RBO

L* 0 93.9±0.

3

94.0±0.

7

94.5±0.

2

94.7±0.

4

94.8±0.

4

94.3±0.

3

94.3±0.

8

8 93.0±0.

4

93.4±0.

9

93.0±0.

3

92.2±0.

4

92.4±0.

1

92.0±0.

4

92.5±0.

8

16 92.7±0.

6

92.2±0.

6

91.9±0.

3

91.1±0.

5

91.3±0.

6

90.9±0.

4

91.8±0.

6

24 92.1±0.

6

91.6±0.

6

91.2±0.

3

90.1±0.

5

90.2±0.

9

90.3±0.

6

90.8±0.

5

32 91.5±0.

3

89.7±1.

2

89.7±0.

3

88.9±0.

6

87.5±1.

0

88.9±1.

1

89.2±1.

0

40 89.7±1.

2

88.5±1.

5

87.2±0.

5

87.1±0.

9

85.9±1.

1

86.5±1.

4

87.1±1.

2

a* 0 -6.0±0.1 -6.4±1.9 -5.9±0.7 -6.2±0.5 -6.1±0.5 -6.0±0.5 -6.1±0.4

8 -7.2±0.2 -7.2±0.4 -6.8±0.2 -7.2±0.4 -7.1±0.5 -6.7±0.1 -6.7±0.2

16 -8.0±0.2 -8.0±0.2 -7.7±0.2 -8.2±0.5 -8.2±0.8 -7.5±0.2 -7.5±0.3

24 -8.6±0.1 -8.7±0.4 -8.3±0.2 -8.6±0.6 -8.6±0.9 -8.0±0.1 -8.1±0.3

32 -9.2±0.2 -8.8±0.3 -8.2±0.2 -8.1±0.8 -7.9±0.8 -7.8±0.8 -8.2±0.3

40 -8.9±0.5 -8.5±0.5 -6.4±0.3 -6.6±1.4 -5.9±1.0 -5.9±1.7 -6.6±0.9

b* 0 20.7±1.

0

21.4±4.

7

19.5±1.

5

20.3±1.

3

20.1±2.

1

20.0±0.

2

19.9±0.

1

8 29.7±2.

6

26.3±1.

6

28.7±1.

6

33.3±2.

3

33.5±2.

9

31.0±2.

6

29.7±4.

5

16 31.2±3. 32.1±2. 35.2±0. 40.6±1. 41.2±2. 35.9±5. 33.8±4.


0 4 4 8 1 0 9

24 36.5±3.

0

37.3±2.

5

40.5±0.

9

46.8±1.

8

47.8±1.

6

40.9±5.

8

39.0±5.

6

32 42.5±3.

1

45.5±2.

6

49.6±1.

1

54.3±1.

8

56.0±1.

2

49.3±5.

9

47.5±4.

6

40 49.4±2.

9

54.8±3.

2

61.3±0.

5

62.8±2.

1

65.5±2.

2

61.3±4.

6

59.0±5.

3 n = 9


0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

0 8 16 24 32 40

Heating Time (Hours)

Ove

rall

colo

r di

ffer

ence

(100 PO) (100 RBO) (40 PO:60 RBO) (45 PO:55 RBO)(50 PO:50 RBO) (55 PO:45 RBO) (60 PO:40 RBO)

Figure 4.1 Changes in overall color difference of palm olein blended with rice bran oil

in heating method


0.00

10.00

20.00

30.00

40.00

50.00

60.00

0 8 16 24 32 40

Frying Time (Hours)

Ove

rall

colo

r di

ffer

ence


Figure 4.2 Changes in over all color difference of palm olein blended with rice bran oil

in frying method


0.00

20.00

40.00

60.00

80.00

100 .00

120 .00

140 .00

0 8 16 24 32 40


Vis

cosi

ty (c

entip

oise

)


Figure 4.3 Changes in viscosity of palm olein blended with rice bran oil in heating

method


0.00

20.00

40.00

60.00

80.00

100 .00

120 .00

140 .00

0 8 16 24 32 40

Frying Time (Hours)

Vis

cosi

ty (c

entip

oise

)


Figure 4.4 Changes in viscosity of palm olein blended with rice bran oil in frying

method


150 .0

200 .0

250 .0

0 8 16 24 32 40


Smok

e po

int (

o C)


Figure 4.5 Changes in smoke point of palm olein blended with rice bran oil in heating

method


150 .0

200 .0

250 .0

0 8 16 24 32 40

Frying Time (Hours)

Smok

e po

int (

o C)


Figure 4.6 Changes in smoke point of palm olein blended with rice bran oil in frying

method


0.000

0.200

0.400

0.600

0.800

1.000

0 8 16 24 32 40


Free

fatt

y ac

id (%

)


Figure 4.7 Changes in free fatty acid of palm olein blended with rice bran oil in

heating method


0.000

0.200

0.400

0.600

0.800

1.000

1.200

1.400

1.600

0 8 16 24 32 40

Frying Time (Hours)

Free

fatt

y ac

id (%

)


Figure 4.8 Changes in free fatty acid of palm olein blended with rice bran oil in frying

method


0.000

1.000

2.000

3.000

4.000

5.000

6.000

7.000

0 8 16 24 32 40


Pero

xide

val

ue (m

eq/k

g)


Figure 4.9 Changes in peroxide value of palm olein blended with rice bran oil in

heating method


0.000

2.000

4.000

6.000

8.000

10.000

12.000

0 8 16 24 32 40

Frying Time (Hours)

Pero

xide

val

ue (m

eq/K

g)


Figure 4.10 Changes in peroxide value of palm olein blended with rice bran oil in

frying method

64

CHAPTER 5

SUMMARY

The improvement in thermal and cold stabilities of palm olein (PO) blended

with rice bran oil (RBO) was investigated in this study. According to the cold stability

test, the oil blended between PO and high RBO could not resist the fat crystal

formation on storage temperature at 15oC. In contrast, all the blended oils remarkably

displayed the excellent resistant to crystallization at 20oC and room temperature. All

blends could retard the crystal formation and remain completely clear and transparent

at 20oC and room temperature for 30 days of experiment. Thus, the effective and

suitable temperature was about 20oC to maintain the blends clear without any

cloudiness. In addition, the blends of PO with 40-60% RBO considerably provided the

most resistance to crystallization of fats. The blended PO with 60% RBO decreased

the cloud point to 5.4oC as compared with 7.3oC of fresh PO. However, all blended oil

did not pass cold test so they were not suitable for salad oil making.

According to the thermal stability test, the blends of PO: RBO in 50:50 ratio

was recommended as the best suitable proportion for frying process since it colud

exhibit superior oxidative stability for 40 hours of heating and frying. This proportion

remarkable decreased FFA content, PV, viscosity, and overall color difference and also

elevated the smoke point.

In future, the blended oil is an alternative source potentially utilize in frying

industry, and capable to modify their properties via the addition of the fat crystal

inhibitors such as sorbitan tristearate and other unsaturated oils such as SBO or SFO to

receive the excellent cold stability, or may add the natural antioxidants in its, for

instance, rosemary extract and sage. The appropriate parameters to measure the oil

deterioration will be further investigation.

65

APPENDIX A

A.O.C.S. Official Method Cc 6-25

Cloud Test

Definition: The cloud point is that temperature at which, under the conditions of this

test, a cloud is induced in the sample caused by the first stage of crystallization.

Scope: Applicable to all normal animal and vegetable fats.

A. Apparatus:

1. Oil sample bottle, 115 ml (4 oz.).

2. Thermometer, A.O.C.S. Specification H 6-40

3. Water bath made up of water, chipped ice and water, or chipped ice, salt and

water, depending upon the temperature required. The temperature of the cloud

bath shall be not less than 2oC. nor more than 5oC. Below the cloud point. A

beaker or sauce pan is a convenient container for this purpose.

B. Procedure:

1. The sample must be completely dry before making the test. Heat 60 to 75 g of

sample to 130oC. Immediately before making the test. Pour ca 45 ml of the

heated fat into an oil sample bottle.

2. Begin to cool the bottle and contents in the water bath, stirring enough to keep

the temperature ca 10oC above the cloud point, begin stirring steadily and

rapidly in a circular motion so as to prevent supercooling and solidification of

fat crystals on the sides or bottom of the bottle.

3. From this point on do not remove the thermometer from the sample, since to do

so may introduce air bubbles which will interfere with the test. The test bottle

is maintained in such a position that the upper levels of the sample in the bottle

and the water in the bath are about the same.

4. Remove the bottle from the bath and inspect regularly. The cloud point is that

temperature at which that portion of the thermometer immersed in the oil is no

longer visible when viewed horizontally through the bottle and sample.

Appendix A 66

A.O.C.S. Official Method Cc 11-53

Cold Test

Definition: This method measures the resistance of the sample to crystallization and

is commonly need used as an index of the winterizing or similar stearin

removing processes.

Scope: Applicable to all normal, refined and dry, animal and vegetable oils.

A. Apparatus

1. Oil sample bottles, 115 ml. (4 oz). These must be completely clean and dry.

2. Chipped ice and water bath at 0oC. Prepare by filling a container (pail or

bucket 4 to 6 lb, capacity) with finely chipped ice. Add cold water sufficient to

fill to the top of the sample bottle when it is immersed.

B. Procedure:

1. Filter a sufficient quantity of sample (200 to 300 ml) through filter paper and

then heat the filtered portion. Stir the sample while heating and remove from

the heat source immediately when the temperature reaches 130oC (see Note 1).

2. Fill an oil sample bottle completely full with the sample and insert a cork

tightly. Adjust to 25oC in water bath and then seal with paraffin.

3. Immerse the bottle containing the sample in the ice and water bath so that the

entire bottle is covered with the water and ice.

4. Replenish the ice as often as is necessary to keep the bath solidly packed,

otherwise the bath temperature will not remain at 0oC, as specified. This

temperature is essential.

5. At the end of 5.5 hours, remove the bottle from the bath and examine closely

for fat crystals or cloudiness. Do not mistake small and finely dispersed air

bubbles for fat crystals. To pass the test the sample must be clear, limpid, and

brilliant (see Note 2).

C. Notes:

1. The purpose of the preliminary heat treatment is to remove traces of moisture

and to destroy any crystal nuclei which may be present. Either will interfere

with the test, causing cloudiness or premature crystallization.

Appendix A 67

2. If it is desired, the test may be continued by re-examination of the sample at

hourly intervals after the first 5.5 hours examination. However, in doing this,

the sample should be returned to the bath as promptly as possible after each

inspection so that the temperature will not increase by any significant amount.

Appendix A 68

Table A-1 Cloud point and cold test of PO blended with RBO

Ratio Cloud points Cold test*

PO:RBO (oC) (0oC; 5.5 hours.)

0:100 2.7 Negative

10:90 3.5 Negative

20:80 4.2 Negative

30:70 4.6 Negative

40:60 5.3 Negative

50:50 5.9 Negative

60:40 6.2 Negative

70:30 6.3 Negative

80:20 6.6 Negative

90:10 6.9 Negative

100:0 7.7 Negative

*Negative : Did not pass through cold test according to AOCS Cc 11-53

Appendix A 69

(a) (b)

(c) (d)

(e) (f)

Figure A-1. Cold stability of palm olein blended with rice bran oil stored at various

temperatures at day 10, 20, 30, 40, 50, and day 60.

Appendix A 70

(a1) (a2)

(b1) (b2)

(c1) (c2)

Figure A-2 Cold stability of blends of palm olein with rice bran oil after 5 days at

(a) 15oC (b) 20oC (c) RT

Appendix A 71

(a1) (a2)

(b1) (b2)

(c1) (c2)


(a) 15oC (b) 20oC (c) RT

Appendix A 72

(a1) (a2)

(b1) (b2)

(c1) (c2)


(a) 15oC (b) 20oC (c) RT

Appendix A 73

(a1) (a2)

(b1) (b2)

(c1) (c2)


(a) 15oC (b) 20oC (c) RT

Appendix A 74

(a1) (a2)

(b1) (b2)

(c1) (c2)


(a) 15oC (b) 20oC (c) RT

Appendix A 75

(a1) (a2)

(b1) (b2)

(c1) (c2)


(a) 15oC (b) 20oC (c) RT

76

APPENDIX B

A.O.C.S. Official Method Cc 9a-48

Smoke, Flash, and Fire Points

Definition: These methods determine the temperature at which the sample will

smoke, flash, or burn.

Scope: Applicable to animal, vegetable, and marine fats and oils. Flash point not

applicable to samples which flash point below 300oF. (148.9oC).

A. Apparatus:

1. Cabinet constructed of the materials and in accordance with the dimensions

shown in the illustration.

2. Thermometer, A.O.C.S. specification H 5-40.

3. Cleveland open flash cup, A.S.T.M. Designation D 92-33, constructed of brass

and conforming to the dimensional requirements prescribed in Table 1. The

beveled edge of the cup is at angle of ca 45o. There may be a fillet of ca 5/32

inch (3.97 mm) in radius inside the bottom of the cup.

4. Heating plate, constructed of brass, cast iron, wrought iron, or steel, ¼ inch

(6.35 mm) thick and 6 inches (152.4 mm) in diameter. There is plane

depression 1/32 inch (0.79 mm) deep in the center of the plate with diameter

just sufficient to fit the cup and centered with the circular opening cut through

the plate, 2 3/16 inches (55.0 mm) in diameter. The plate is covered with a

sheet of hard asbestos board 6.35mm thick and of the same shape as the metal

plate.

Appendix B 77

Table 1 Dimensional Requirement for Cleveland Open Flash Cup.

Inches Mill

Min. Normal Max. Min. Normal Max.

Inside dia. immediately

below filling mark 2 15/32 2 1/2 2 17/32 62.7 63.4 64.3

Outside dia. below

flange 2 21/32 2 11/16 2 23/32 67.5 68.3 69.1

Inside height from center

of bottom to rim 1 9/32 15/16 1 11/32 32.5 33.3 34.1

Thickness of bottom 7/64 1/8 9/64 2.8 3.2 3.6

Distance from rim to

filling mark 23/64 3/8 25/64 9.1 9.5 9.9

Distance lower surface

flange to bottom of cup 1 7/32 1 ¼ 19/32 31.0 31.8 32.6

Vertical distance upper

surface flange to rim 7/64 1/8 9/64 2.8 3.2 3.6

Thickness of rim 5/64 3/32 7/64 2.0 2.4 2.8

Width of lower surface

of flange 9/16 19/32 5/8 14.3 15.1 15.9

5. Heat source, gas burner, alcohol lamp, or electric heater with rheostat control.

Whatever form of heat is used under no circumstances are the products of

combustion or free flame allowed to come up around the cup. If a flame heater

is used, it may be protected from drafts or excessive radiation with any suitable

shield that does not project above the upper surface of the asbestos board. The

heat source is centered under the plate opening and must not produce local

superheating.

Appendix B 78

6. Metal flame test burner.

Smoke Point Cabinet

B. Procedure:

(a) Smoke Point.

1. Fill the cup (see Note 1) with the oil or melted fat sample so that the top

of the meniscus is exactly at the filling line and adjust the position of

the apparatus so that the beam of light is directed across the center of

the cup. Suspend or secure the thermometer in a vertical position in the

center of the dish with the bottom of the bulb ca 6.35 mm from the

bottom of the cup.

2. Heat the sample rapidly to within ca 75oF (41.7oC) of the smoke point.

Thereafter, regulate the heat so that the temperature of the sample

increases at the rate of 9oF to 11oF (5oC to 6.1oC) per minute. The

smoke point is the temperature indicated by the thermometer when the

sample gives off a thin, continuous stream of bluish smoke. In some

Appendix B 79

cases, a slight puff appears before the sample begins to smoke

continuously. This is disregarded.

(b) Flash Point.

1. The flash and fire points may be conducted without the cabinet but in

room or compartment free from air drafts and darkened sufficiently so

that the flash is readily discernible. Avoid breathing over the surface of

the sample.

2. Fill the cup with the oil or melted fat sample so that the top of the

meniscus is exactly at the filling line. Suspened or secure the

thermometer in a vertical position with the bottom of the bulb ca 6.35

mm from the bottom of the cup and in a position half way between the

center and back of the cup.

3. Heat the sample at a rate not to exceed 30oF (16.7oC) rise per minute to

within ca 100oF (55.6oC) of the flash point. Thereafter regulate the rate

of heating so that the temperature of the sample increases 9oF to 11oF

(5oC to 6.1oC) per minute.

4. Apply the test flame, which is ca 1/8 inch (3.17mm.) in diameter as the

temperature reaches each successive 5oF (2.8oC) mark. Pass the flame

in a straight line or on the circumference of a circle having a radius of at

least 150 mm. (ca 6 inches) across the center of the cup and the right

angles to the diameter passing through the thermometer. The test flame

shall, while passing across the surface of the sample, be in the plane of

the upper edge of the cup. The time for the passage of the test flame

across the cup shall be ca 1 second.

5. The flash point is the temperature indicated by the thermometer when a

flash appears at any point on the surface of the sample. The true flash

must not be confused with a bluish halo that sometimes surrounds the

test flame.

Appendix B 80

(c) Fire Point.

1. Continue the heating, after the flash point determination, as directed in

paragraph 3 and in the manner prescribed for the flash point until the

fire point is reached.

2. The fire point is the temperature indicated by the thermometer when

application of the test flame causes burning for a period of at least 5

seconds.

C. Note:

1. It is imperative that the apparatus, especially the cup, be scrupulously clean and

free from any substance that may cause smoke to appear ahead of the true

smoke point.

Appendix B 81

A.O.C.S. Official Method Ca 5a-40

Free Fatty Acids

Definition: This method determines the free fatty acids existing in the sample.

Scope: Applicable to crude and refined vegetable and marine oils and animal fats.

A. Apparatus:

1. Oil sample bottles, 115 or 230 ml (4 or 8 oz) or 250 ml Erlenmeyer flasks.

B. Reagents:

1. Ethyl alcohol, 95% (U.S.S.D. Formulas 30 and 3A are permitted). The alcohol

must give a definite, distinct and sharp end-point with phenolphthalein and

must be neutralized with alkali to a faint but permanent pink color just before

using.

2. Phenolphthalein indicator solutions, 1% in 95% alcohol (see Note 1).

3. Sodium hydroxide solutions, accurately standardized.

C. Procedure:

F.F.A. Range, % Grams of Sample Ml. of Alcohol Strength of Alkali

0.00 to 0.2 56.4 50±0.2 0.1 N

0.2 to 1.0 28.2 50±0.2 0.1 N

1.0 to 30.0 7.05 75±0.05 0.25 .N

30.0 to 50.0 7.05 100±0.05 0.25 or 1.0 N

50.0 to 100 3.525 100±0.001 1.0 N

1. Samples must be well mixed and entirely liquid before weighing.

2. Use the table above to determine quantities to be used with various ranges of

fatty acids. Weight the designated size of sample into an oil-sample bottle or

Erlenmeyer flask (see Note 2).

3. Add the specified amount of hot, neutralized alcohol and 2 ml of indicator.

4. Titrate with alkali shaking vigorously to the appearance of the first permanent

pink color of the same intensity as that of the neutralized alcohol before

addition of the sample. The color must persist for 30 seconds.

Appendix B 82

D. Calculations:

1. The percentage of free fatty acids in most types of fats and oils is calculated as

oleic acid, although in coconut and palm kernel oils it is frequently expressed

as lauric acid and in palm oil in terms of palmitic acid.

a. Free fatty acids as oleic, % =

Ml. of alkali × N × 28.2

Weight of sample

b. Free fatty acids as lauric, % =


Weight of sample

c. Free fatty acids as palmitic, % =


Weight of sample

2. The free fatty acids are frequently expressed in terms of acid value instead of %

free fatty acids. The acid value is defined as the number of mg of KOH necessary

to neutralize 1g of sample. To convert % free fatty acids (as oleic) to acid value,

multiply the former by 1.99.

E. Notes:

1. Isopropanol, 99%, may be used as an alternate solvent with crude and refined

vegetable oils.

2. Cap bottle and shake vigorously for one minute if oil has been blanketed with

carbon dioxide gas.

Appendix B 83

A O. C. S. Official Method Cd 8-53

Peroxide Value

Definition: This method determines all substances, in terms of milli-equavalents of

peroxide per 1000 grams of sample, which oxidize potassium iodide under the

conditions of the test. These are generally assumed to be peroxides or other

similar products of fat oxidation.

Scope: Applicable to all normal fats and oils including margarine. This method is

highly empirical and any variation in procedure may result in variation in

results.

A. Apparatus:

1. Pipet, Mohr, measuring type, 1 ml capacities.

2. Erlenmeyer flasks, glass-stopped, 250 ml.

B. Reagents:

1. Acetic acid-chloroform solution. Mix 3 parts by volume of glacial acetic acid,

reagent grade, with 2 parts volume of chloroform, U.S.P. grade.

2. Potassium iodide solution, saturated solution of KI, A.C.S. grade, in recently

boiled distilled water. Make sure the solution remains saturated as indicated by

the presence of undissolved crystals. Store in the dark. Test daily by adding 2

drops of starch solution to 0.5 ml of potassium iodide solution in 30 ml of

acetic-chloroform solution. If a blue color is formed which requires more than

1 drop of 0.1 N sodium thiosulfate solutions to discharge, discard the iodide

solution and prepare a fresh solution.

3. Sodium thiosulfate solution, 0.1 N, accurately standardized.

4. Sodium thiosulfate solution, 0.01 N, accurately standardized. This solution

may be prepared by accurately pipeting 100 ml of the 0.1 N solution into a

1000 ml volumetric flask and diluting to volume with recently boiled distilled

water.

5. Starch indicator solution, 1.0% of soluble starch in distilled water.

C. Procedure for Fats and Oils:

1. Weigh 5.00±0.05 g of sample into a 250 ml . glass-stopped Erlenmeyer flask

and then add 30 ml of the acetic-chloroform solution. Swirl the flask until the

Appendix B 84

sample is dissolved in the solution. Add 0.5 ml of saturated potassium iodide

preferably using Mohr type measuring pipet.

2. Allow the solution to stand with occasional shaking for exactly 1 minute and

then add 30 ml of distilled water.

3. Titrate with 0.1 N sodium thiosulfate adding it gradually and with constant and

vigorous shaking. Continue the titration until the yellow color has almost

disappeared. Add ca 0.5 ml starch indicator solution. Continue the titration,

shaking the flask vigorously near the endpoint to liberate all the iodide from the

chloroform layer. Add the thiosulfate dropwise until the blue color has just

disappeared.

Note: If the titration is less than 0.5 l, repeat the determination using 0.01 N

sodium thiosulfate solutions.

4. Conduct a blank determination of the reagents daily. The blank titration must

not exceed 0.1 ml of the 0.1 N sodium thiosulfate solution.

D. Calculation:

1.Peroxide value as milliequavalents of peroxide per 1000 g of sample =

(S-B) (N) (1000)

weight of sample

B = Titration of blank.

S = Titration of sample.

N = Normality of sodium thiosulfate solution.

E. Procedure for Margarine:

1. Proceed as directed above in paragraphs 1 through 4 after preparation of the

sample as directed below.

2. Melt sample by heating with constant stirring on hot plate set at low heat, or by

heating in air oven at 60-70oC. Avoid excessive heating and particularly

prolonged exposure of oil to temperatures above 40oC.

3. When completely melted, remove the sample from the hot plate or oven and

allow to settle in a warm place until the aqueous portion and most of the milk

solids have settled to the bottom.

Appendix B 85

4. Decant the oil into a clean beaker and filter through a Whatman No. 4 (or

equavalent) into another clean beaker. Do not reheat unless absolutely

necessary for filtration. The sample should be clear and brilliant.

Appendix B 86

Brookfield Viscometer

(Synchro-lectric)

Model LVF100

How to operate

1. Attach spindle to lower shaft. It is best to lift the shaft slightly while it is held

firmly with one hand whole screwing the spindle on with the other. Care

should be taken to avoid putting side thrust on the shaft to protect its alignment.

2. Insert spindle in the test material until the fluid’s level is at the immersion

groove cut in the spindle’s shaft. With a disc type spindle it is sometimes

necessary to tilt the instrument slightly while immersing to avoid trapping air

bubbles on its surface. (You may find it more convenient to immerse the

spindle in this fashion before attaching it to the Viscometer). Care should be

taken not to hit the spindle against the sides of the fluid container while it is

attached to the Viscometer, since this too can damage the shaft alignment.

3. Level the Viscometer. The bubble level on all models will be of help in this

respect.

4. Depress the clutch and turn on the Viscometer’s motor: following the

procedure of having the clutch depressed at this point will prevent unnecessary

wear. Release the clutch and allow the dial to rotate until the pointer stabilizes

at a fixed position on the dial. The time required for stabilization will depend

on the speed at which the spindle rotates: at speeds above 4 rpm this will

generally be about 20-30 seconds, while at lower speeds it may take the time

required for one revolution of the dial. It is possible to observe the pointer’s

position and stability at low speeds while the dial rotates but at higher speeds it

will be necessary to depress the cutch and snap the motor switch to stop the

instrument with the pointer in view. Very little practice is needed to stop the

dial at the right point.

5. If check readings are required, start the Viscometer with the clutch still

depressed, holding the original reading, and then release. This will speed up

readings by reducing oscillation of the pointer. If pointer does not stabilize, the

material may be either thixotropic or its temperature may not be constant.

Appendix B 87

Having the spindle at the temperature of the test material will eliminate the

latter possibility.

6. The viscosity of the test material can easily be obtained by consulting the

Factor Finder supplied with the Viscometer for use with all model

7. To convert viscometer dial reading to centipoises (mPa⋅s): adjust slide until

viscometer model and spindle number being used appear in the window.

Multiply reading noted on viscometer 0-100 scale by factor shown beside

speed at which measurement is being made.

Dial reading × Factor = Viscosity in centipoises (mPa⋅s)

8. Full scale viscosity range for any speed and spindle combination is equal to the

factor × 100

Factor × 100 = Full scale range

Appendix B 88

Table B-1 Overall color difference of palm olein blended with rice bran oil in heating

method.

Ratio Time (hours)

PO:RBO 0 8 16 24 32 40

0:100 0.0±0.0 4.4±2.2 10.6±8.0 22.1±9.5 35.5±8.3 47.7±6.7

40:60 0.0±0.0 9.8±0.5 22.4±1.2 34.1±0.3 47.5±0.2 59.0±1.3

45:55 0.0±0.0 19.7±1.0 37.1±1.1 51.4±1.0 63.4±1.8 69.9±2.4

50:50 0.0±0.0 15.7±3.3 31.6±2.7 39.4±4.9 58.1±6.1 69.3±7.8

55:45 0.0±0.0 10.2±0.5 22.4±0.8 32.6±1.9 44.5±1.5 54.7±0.5

60:40 0.0±0.0 11.0±0.5 21.4±0.3 30.7±0.3 41.2±1.3 52.0±2.8

100:0 0.0±0.0 14.9±1.6 22.4±1.4 31.6±2.2 42.9±1.6 53.0±1.5 n = 3

Appendix B 89

Table B-2 Overall color difference of palm olein blended with rice bran oil in frying

method.

Ratio Time (hours)

PO:RBO 0 8 16 24 32 40

0:100 0.0±0.0 5.1±4.3 11.1±6.6 16.4±7.0 24.5±6.9 33.9±7.3

40:60 0.0±0.0 9.4±0.9 16.0±1.2 21.4±1.7 30.5±0.8 42.4±1.7

45:55 0.0±0.0 9.9±5.6 17.3±6.2 24.9±4.1 32.6±4.2 41.1±5.9

50:50 0.0±0.0 14.2±1.5 22.6±1.8 35.7±12.3 40.3±5.6 50.6±6.5

55:45 0.0±0.0 11.3±2.5 16.3±4.9 21.4±5.8 29.9±6.0 42.1±4.9

60:40 0.0±0.0 10.0±4.9 14.2±5.2 19.5±5.9 28.1±4.9 39.8±5.7

100:0 0.0±0.0 9.8±2.7 10.7±3.3 16.1±3.3 22.1±3.1 29.1±3.4 n = 3

Appendix B 90

Table B-3 Viscosity of palm olein blended with rice bran oil in heating method.

Ratio Time (hours)

PO:RBO 0 8 16 24 32 40

0:100 47.5±2.3 53.5±2.3 69.6±2.3 72.0±1.5 86.0±2.3 100.5±6.5

40:60 45.5±7.6 52.5±6.9 59.0±5.7 73.0±13.5 82.0±10.2 92.0±9.8

45:55 45.5±2.3 54.5±0.9 63.0±1.5 78.0±19.9 90.5±6.8 112.5±13.3

50:50 42.0±2.6 47.0±1.7 54.0±2.6 59.5±5.4 72.0±5.2 84.0±10.4

55:45 46.5±3.9 53.5±4.6 59.0±3.1 76.0±11.4 82.5±9.4 94.5±11.7

60:40 45.0±3.9 54.0±10.8 61.5±9.1 71.0±11.1 82.0±10.6 104.5±23.5

100:0 49.5±2.6 53.5±8.8 59.5±4.3 66.5±6.1 76.0±8.3 88.5±9.4 n = 3

Appendix B 91

Table B-4 Viscosity of palm olein blended with rice bran oil in frying method.

Ratio Time (hours)

PO:RBO 0 8 16 24 32 40

0:100 46.0±1.7 53.0±1.7 60.0±1.5 70.5±1.5 83.0±6.2 101.0±13.9

40:60 46.5±6.9 53.2±11.9 64.5±10.5 73.5±11.3 81.5±11.3 100.5±14.8

45:55 45.3±1.6 48.8±1.2 54.3±3.7 63.3±5.5 73.5±6.1 85.0±7.9

50:50 40.8±2.8 47.8±1.6 60.0±0.0 70.8±1.9 78.0±2.3 92.0±10.5

55:45 48.5±9.8 53.0±7.6 69.0±3.2 70.5±15.8 82.0±18.1 101.0±32.1

60:40 46.5±9.1 54.0±13.1 63.5±12.0 73.0±14.6 92.5±13.4 113.5±16.9

100:0 44.0±4.8 60.0±4.8 57.5±5.7 64.5±6.5 73.0±7.4 82.0±8.7 n = 3

Appendix B 92

Table B-5 Smoke point of palm olein blended with rice bran oil in heating method.

Ratio Time (hours)

PO:RBO 0 8 16 24 32 40

0:100 212.0±2.0 208.7±1.2 199.3±4.2 196.3±3.2 190.7±3.1 186.0±2.6

40:60 212.7±4.2 207.0±1.0 198.7±2.9 194.0±2.0 186.0±2.6 184.0±3.6

45:55 205.3±3.5 196.7±1.5 191.0±1.0 181.3±8.1 180.7±1.2 175.7±2.1

50:50 205.7±3.1 199.0±4.4 193.3±4.2 184.7±2.5 180.0±4.0 179.7±6.7

55:45 210.0±4.6 204.0±1.0 196.3±5.0 192.7±2.3 188.7±2.1 183.7±1.5

60:40 209.7±4.5 205.7±3.2 194.7±4.2 190.0±6.1 188.0±2.0 186.0±4.0

100:0 201.0±1.0 196.0±1.0 190.7±2.5 184.0±1.0 179.7±1.5 176.7±2.3 n = 3

Appendix B 93

Table B-6 Smoke point of palm olein blended with rice bran oil in frying method.

Ratio Time (hours)

PO:RBO 0 8 16 24 32 40

0:100 213.0±1.0 203.3±3.2 199.7±2.5 191.0±5.6 186.7±4.7 182.0±5.3

40:60 208.0±3.6 203.3±0.6 191.0±1.0 182.0±2.0 177.3±2.5 172.0±3.6

45:55 209.2±3.3 203.0±6.6 191.7±6.0 185.2±5.8 174.7±2.3 170.0±2.0

50:50 207.7±8.0 199.5±5.6 188.0±2.6 181.2±6.5 173.0±1.7 168.3±1.5

55:45 208.0±1.0 200.3±4.0 191.7±0.6 182.0±2.6 174.3±2.1 172.3±3.8

60:40 206.0±1.0 200.7±3.2 191.3±4.6 178.0±2.0 173.0±1.7 168.0±1.7

100:0 202.0±1.7 195.0±3.0 187.7±2.3 181.0±1.0 176.3±1.2 169.7±3.5 n = 3

Appendix B 94

Table B-7 Free fatty acid content of palm olein blended with rice bran oil in heating

method.

Ratio Time (hours)

PO:RBO 0 8 16 24 32 40

0:100 0.09±0.01 0.16±0.05 0.21±0.02 0.32±0.09 0.42±0.09 0.55±0.15

40:60 0.11±0.03 0.16±0.05 0.33±0.05 0.49±0.08 0.58±0.03 0.80±0.06

45:55 0.06±0.01 0.14±0.01 0.24±0.04 0.37±0.10 0.45±0.07 0.57±0.03

50:50 0.06±0.01 0.13±0.02 0.22±0.04 0.25±0.02 0.33±0.13 0.47±0.03

55:45 0.12±0.02 0.22±0.06 0.33±0.03 0.53±0.10 0.67±0.03 0.76±0.22

60:40 0.11±0.01 0.22±0.03 0.31±0.03 0.55±0.01 0.71±0.08 0.81±0.09

100:0 0.08±0.00 0.20±0.05 0.31±0.11 0.43±0.14 0.53±0.06 0.74±0.22 n = 3

Appendix B 95

Table B-8 Free fatty acid content of palm olein blended with rice bran oil in frying

method.

Ratio Time (hours)

PO:RBO 0 8 16 24 32 40

0:100 0.10±0.01 0.18±0.07 0.27±0.02 0.44±0.12 0.62±0.16 0.72±0.22

40:60 0.12±0.03 0.27±0.02 0.48±0.09 0.78±0.13 0.96±0.12 1.36±0.24

45:55 0.07±0.02 0.17±0.09 0.28±0.16 0.49±0.24 0.69±0.40 0.83±0.49

50:50 0.08±0.03 0.17±0.06 0.34±0.10 0.38±0.11 0.53±0.04 0.60±0.12

55:45 0.12±0.04 0.26±0.03 0.47±0.05 0.75±0.08 1.05±0.08 1.25±0.07

60:40 0.11±0.02 0.25±0.03 0.49±0.04 0.70±0.05 1.02±0.03 1.15±0.17

100:0 0.07±0.00 0.16±0.03 0.30±0.02 0.54±0.03 0.67±0.04 0.88±0.10 n = 3

Appendix B 96

Table B-9 Peroxide value of palm olein blended with rice bran oil on heating method.

Ratio Time (hours)

PO:RBO 0 8 16 24 32 40

0:100 1.58±0.62 3.16±1.39 3.62±1.39 2.65±0.60 3.21±1.11 3.00±0.66

40:60 1.31±0.54 2.46±0.31 2.30±0.26 2.39±0.32 2.34±0.38 2.55±0.40

45:55 1.82±0.78 3.80±0.47 4.13±0.17 5.15±0.12 3.41±1.78 4.48±0.66

50:50 1.35±0.38 3.06±0.33 3.00±0.82 3.95±0.92 4.11±0.81 2.71±0.60

55:45 1.20±0.08 2.39±0.46 2.44±0.34 3.07±0.81 2.61±0.42 2.38±0.43

60:40 1.10±0.15 2.73±0.13 2.44±0.39 2.35±0.23 2.13±0.09 2.50±0.42

100:0 1.56±0.62 3.87±1.87 3.39±0.99 3.28±0.23 3.52±1.31 2.83±0.19 n = 3

Appendix B 97

Table B-10 Peroxide value of palm olein blended with rice bran oil in frying method.

Ratio Time (hours)

PO:RBO 0 8 16 24 32 40

0:100 1.87±0.35 5.62±2.52 5.69±1.08 6.69±0.91 6.20±1.48 5.23±1.71

40:60 1.45±0.49 3.59±0.36 3.96±0.40 4.31±0.60 3.79±0.54 3.69±0.70

45:55 1.61±0.22 4.36±2.33 4.93±1.17 5.56±1.67 6.37±1.75 4.89±1.98

50:50 1.49±0.81 6.26±2.64 4.23±1.24 4.03±1.76 4.50±1.69 2.96±1.10

55:45 1.52±0.39 4.34±0.22 4.85±0.67 4.78±0.27 4.97±0.76 4.06±0.23

60:40 1.23±0.28 4.91±0.17 4.02±0.74 4.16±0.56 4.35±0.40 4.49±0.61

100:0 1.68±0.65 6.79±2.77 6.98±1.32 7.71±2.78 7.33±1.66 6.84±1.78 n = 3

Appendix B 98

70.000

80.000

90.000

100 .000

0 8 16 24 32 40

Heating Time (hours)

L*

valu

e

100 PO 100 RBO 40 PO:60 RBO 45 PO:55 RBO50 PO:50 RBO 55 PO:45 RBO 60 PO:40 RBO

Figure B-1 Changes in L* value of palm olein blended with rice bran oil in heating

method

Appendix B 99

80.000

85.000

90.000

95.000

100 .000

0 8 16 24 32 40

Frying Time (hours)

L*

valu

e


Figure B-2 Changes in L* value of palm olein blended with rice bran oil in frying

method

Appendix B 100

-10.000

-9.000

-8.000

-7.000

-6.000

-5.000

-4.000

-3.000

-2.000

-1.000

0.0000 8 16 24 32 40


a* v

alue


Figure B-3 Changes in a* value of palm olein blended with rice bran oil in heating

method

Appendix B 101

-10.000

-9.500

-9.000

-8.500

-8.000

-7.500

-7.000

-6.500

-6.000

-5.500

-5.0000 8 16 24 32 40

Frying Time (hours)

a* v

alue


Figure B-4 Changes in a* value of palm olein blended with rice bran oil in frying

method

Appendix B 102

10.000

20.000

30.000

40.000

50.000

60.000

70.000

80.000

90.000

100 .000

0 8 16 24 32 40


b* v

alue


Figure B-5 Changes in b* value of palm olein blended with rice bran oil in heating

method

Appendix B 103

10 .000

20 .000

30 .000

40 .000

50 .000

60 .000

70 .000

0 8 16 24 32 40

Frying Time (hours)

b* v

alue


Figure B-6 Changes in b* value of palm olein blended with rice bran oil in frying

Method

104

VITA

Name Mr. Surin Watanapoon

Date of birth 11 May 1968

Pace of birth Chiangmai, Thailand

Institution attened King Mongkut’s Institute of Technology,

Chaokunthaharn Ladkrabang, 1988-1990:

Bachelor of Science (Agricultural Industrial)

Office Pamola Co., Ltd.

Krathumbean, Samutsakorn

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