Effect of Ohmic Heating on Increasing Guava Juice Yield

Pramoun Srikalong Faculty of Agro-Industry

King Mongkut’s Institute of Technology Ladkrabang, Bangkok 10520, Thailand

kjpramou@kmitl.ac.th, amam60@hotmail.com

Thanit Makrudin, Pongpat Sampavamontri, Ekarin Kovitthaya

Faculty of Agro-Industry King Mongkut’s Institute of Technology Ladkrabang,

Bangkok 10520, Thailand kjpramou@kmitl.ac.th, amam60@hotmail.com

Abstract— The objective of this work was to study effects of ohmic heating application on mechanical extraction and sensory characteristics of guava juice. The AC voltages, 100 150 and 200 volt, were used to treat the whole guava (in 0.05% NaCl solution providing ions as charge carries) and the yield of treated guava juice from mechanical extraction was investigated to determine the optimum of voltage for ohmic heating process base on the change in voltage. This study clearly demonstrated that whole treated guava with 100 voltage was the best treatment. After using 100 volt with varied concentration of NaCl solution from 0.05% to 0.125%, the treatment that used NaCl solution 0.05% was found to more efficient than other treatment. The sensory evaluations of treated guava juice (100 volt with 0.05% NaCl solution) compared with no treated guava juice were not significantly different (p<0.05)

I. INTRODUCTION Alternating Current (AC) treatment of food material,

ohmic heating, is used for rapid thawing of food [1], [6], [13]. Ohmic heating process is used for pasteurization and sterilization of food for preservation and microbial inactivation [4], [11], [14]. Ohmic heating can be used as an blanching system for food [3], [8], [9]. The electrical current through a food that serves as an electrical resistance [2], [7]. Recently there has been research on new application of this technique to food processing. For example, ohmically heated can be used for enhancing expression of juice from plant tissue [5].

The aim of this study was to obtain enhancing mechanical extraction guava juice by using alternating current (AC) treatment, ohmic heating. Effects of voltage and concentration of NaCl solution dissolved in ohmic heating system that provide ions as charge carries and sensory characteristics of treated guava juice were studied.

II. MATERIALS AND METHODS

A. Law material Guavas (variety Pan, 9 oBrix (+2) of total soluble solids)

were the raw materials. Fresh guavas were purchased at the local supermarket and stored at ambient temperature whole

fresh guavas were washed and weighted (200+10 grams). To avoid differences in samples caused by moisture loss during storage, the reserve was refreshed every 2 days

B. Ohmic heating equipment Ohmic heating vessel was made of clear acrylic plastic.

Rectangular acrylic vessel (12x12x12 cm. and 0.5 cm. thickness) was thermostatically controlled to maintain the set heating temperature (+2oC) using a temperature control system (Micro controller model JCS-33A-R/M, Shinko, Japan). The electrodes (stainless steel 316L) of vessel units was connected to a low voltage AC slid up transformer (Model TDGC2-3KVA, UNION, Taiwan), which provide voltage about 0-270 volt.

C. Experimental conditions Of appropriate voltage condition, in sets of experiments,

whole fresh guava was weighted about 200+10 grams and fixed into middle of vessel with PET plastic ring. Ohmic heating vessel was filled with 1.4 l of 0.05% NaCl solution (AR. Grade, Merck), which was a good electrical conductivity solution providing ions as charge carries [10]. The electrodes were installed between the PET plastic ring. The varied voltage (100, 150 and 200 volt) of alternating current AC from slide up transformer was applied to the whole fresh guava through the electrodes and NaCl solution. The system of ohmic heating was shutdown when the guava tissue was treated electrically at a moderate temperature of 50oC. Treated guavas from in sets of experiments were mechanical extracted with juice extractor (extractor model TRK-74, Turbora, Thailand), filtrated using double layer muslin as a filter and pasteurized at 90oC for 50s. The percentage of juice extraction yields was observed which was explained by the voltage effect. The sensory characteristics of treated guava juice were compared with no treated guava juice. The sensory characteristics (taste, flavor, texture and overall acceptation) of treated guava juice was base on 30 panelists (prefer ability in 9-point Hedonic scale scoring test).

When the optimum voltage of ohmic heating application on fresh guava was shown : that condition was operated at moderate NaCl solution concentration (0.05, 0.075, 0.10 and 0.125%) again for defining optimum concentration of NaCl

122

Ohmic heating; guava; juice; extraction Keywords -

2011 2nd International Conference on Biotechnology and Food Science IPCBEE vol.7 (2011) © (2011) IACSIT Press, Singapore

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III. RESU

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ULTS AND DISU

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Table 1 pre

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TABLE 1 THE SENSALTERNATING CU

Voltage Tas

0 4.50+1

100 5.00+1

150 5.00+2

200 5.13+2 Values in th

gnificantly dif

Optimum ccarrirs

The optimurst stage expeercentage of goncentration ohows the tempeatment (100 aCl solution re

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uice yield (62

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sent the sensochanical extrant at 100, 150verall acceptaom 100-200 v

05)

SORY CHARACTERURRENT (AC) TREA

Sen

ste Flav

1.961a 4.50+1

1.983a 5.27+1

2.068a 5.17+1

2.177a 4.90+1

he same columfferent (p<0.05

concentration

um voltage oferiment was guava juice eof NaCl solutperature of guvolt) by usingespectively.ime of the el0.1 and 0.125

s respectively00 volt and 0temperature tor long times .05% yield)

for the ohmicallywith 100, 150 an

ory evaluationactor by using0 and 200 voltation of panevolt were also

RISTICS OF TREATATMENT WITH 10

nsory evaluations

vor Textu

.943a

4.77+1.7

.929a

5.20+1.9

.895a

5.07+1.4

.882a

5.37+1.9

mn with differe5) as determin

of NaCl solut

f ohmic heatishown (100

extraction yieltion might be uava, ohmicag 0.05, 0.075,

lectric treatm5% NaCl solut. The guava

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ns of treated gg ohmically ht. The taste flelists with tro not signific

TED GUAVA JUICE00, 150 AND 200 V

s

ure Overal

acceptati

794a 4.47+1.8

901a 5.37+1.8

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938a 5.17+1.8

ent superscriptned by ANOV

tion as charge

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ally heated by, 0.10 and 0.1

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123

A.

B.

(2002) from extracting with mechanical extractor which was shown in figure 4 but they were not significantly different (p<0.05) as determined by ANOVA

Figure 3. Temperature change in guava during ohmically heated by alternating current (AC) treatment with 100 volt at 0.05, 0.075, 0.10 and

0.125% NaCl solution

Figure 4. Final guava juice yield for the ohmically heated followed by parameter concentration of NaCl solution (0.05, 0.075, 0.10 and 0.125%)

Table 2 show the sensory characteristics of extracted guava juice from mechanical extractor by using ohmically heated by alternating AC treatment at 100 volt at 0.05%-0.125% NaCl solution. The taste, texture and overall acceptation of 30 panelists were also not significantly different (p<0.05) excepted for flavor

TABLE 2 THE SENSORY CHARACTERISTICS OF TREATED GUAVA JUICES BY ALTERNATING CURRENT (AC) TREATMENT WITH 100 VOLT AT 0.05, 0.075,

0.10 AND 0.125% NACL SOLUTION

%NaCl

Solution

Sensory evaluations

Taste Flavor Texture Overall

acceptation

0.05

5.00+1.983a

5.27+1.929ab

5.70+1.901a 5.37+1.829a

0.075

5.10+1.668a

4.73+1.982a

5.13+1.456a 5.30+1.466a

0.10

4.63+2.109a

1.87+1.852ab

5.23+1.547a 5.13+1.795a

0.125

5.60+1.129a

5.87+1.676b

5.30+1.685a 5.67+1.322a

Values in the same column with different superscripts are significantly different (p<0.05) as determined by ANOVA

IV. CONCLUSIONS The obtained data from using ohmically heated

alternating current (AC) treatment varied voltage from 100-200 volt and varied concentration of NaCl solution from 0.05, 0.075, 0.10 and 0.125% on whole fresh guava before extracting guava juice by mechanical extractor was showed that the 100 volt of alternating current (AC) treatment and 0.05% NaCl solution was the best treatment for damaging the whole fresh guava tissue which increased the guava juice from optimum ohmically treatment (100 volt, 0.05% NaCl solution ) were also not significantly different (p<0.05) in taste texture and over all acceptation excepted for flavor (less difference) compared with fresh guava juice.

ACKNOWLEDGEMENTS The Authors appreciate the financial support received

through Faculty of Agro-Industry, King Mongkut’s Institute of Technology Ladkrabang.

REFERENCES Article in a journal: [1] B. Li and D.W. Su, “Novel methods for rapid freezing and thawing of

foods-a review,” Journal of Food Engineering, vol. 54, 2001, pp. 175-182.

[2] F. Icier and C. Ilicali, “Temperature dependent electrical conductivities of fruit purees during ohmic heating,” Food Research International, vol. 38, 2005, pp. 1135-1142.

[3] F. Icier , H. Yildiz and T. Baysal, “Peroxidase inactivation and colour changes during ohmic blanching of pea puree,” Journal of Food Engineering, vol. 74, 2005, pp. 424-429.

[4] H. Sun, S. Kawamura, J.I. Himato, K. Itoh, T. Wada and T. Kimura, “Effects of Ohmic heating on microbial counts and denaturation of proteins in milk,” Food Science and Technology Research, vol.14(2), 2007, pp. 117-123.

[5] I. Praporscic, N.I. Lebovka, S. Ghnimi and E. Vorobiev, “Ohmically heated, enhanced expression of juice from apple and potato tissues,” Biosystems Engineering, vol. 93(2), 2006, pp. 199-204.

[6] J.S. Roberts, M.O. Balaban, R. Zimmerman and D. Luzuriaga, “Design and testing of a prototype ohmic thawing unit Computers and Electronic in Agriculature,” vol. 19, 1997, pp. 211-222.

[7] S.K. Sastry and S. Salengke, “Ohmic heating of solid-liquid mixtures: a comparison of mathematical models under worst-case heating conditions,” Journal of Food Process Engieering, vol. 21, 1998, pp. 441-458.

[8] S. Mizarahi, “Leaching of soluble solids during blanching of vegetables by ohmic heating,” Journal of Food Engineering, vol. 29, 1996, pp. 153-166.

[9] S. Sarang, S.K. Sastry, J. Gaines, T.C.S. Yang and P. Dunne, “Product formulation for ohmic heating: Blanching as a pretreatment method to improve uniformity in heating of solid- liquid food mixtures,” Journal of Food Science, vol.6, 2007, pp. E227-E234.

[10] S. Ghnimi, N. Flach-Malaspina, M. Dresch, G. Delaplace and J.F. Maingonnat, “Design and performance evaluation of an ohmic heating unit for thermal processing of highly viscous liquids,” Chemical engneering research and design, vol. 86, 2008, pp. 626-632.

[11] U. Kunihiko, “Electrical heating and sterilization of food. Thermophys Prop”, vol. 20, 1999, pp. 30-33.

62.05 59.09 58.10 59.77

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

100.00

0.5 0.75 0.1 0.125

% NaCl solution

% Yield

% Yield

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[12] W. C. Wang and S.K. Sastry, “Effects of moderate electrothermal treatments on juice yield from cellular tissue. Innovation,” Food Science & Emerging Technologies, vol. 3, 2002, pp. 371-377.

[13] Y. Miao, J.Y. Chen and A. Noguchi, “Studies on the ohmic thawing of frozen surimi,” Food Science and Technology Research, vol. 13(4), 2006, pp. 296-300.

Article in a conference proceedings: [14] H. Sun, S. Kawamura, J.I. Himoto and T. Wada, “Ohmic heating for

pasteurization,” Society of Agricultural and Biological Engineers, 2006, ASAE Annual Meeting

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