Encapsulation - Capsul Maltodextrin - Vit c

2nd Mercosur Congress on Chemical Engineering

4th Mercosur Congress on Process Systems Engineering

* To whom all correspondence should be addressed. Address: Escola de Química, UFRJ - Centro de Tecnologia, Bl.E, 21949-900 Rio de Janeiro – Brazil E-mail: [email protected]

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MICROENCAPSULATION OF ASCORBIC ACID IN MALTODEXTRIN

AND CAPSUL USING SPRAY-DRYING

Priscilla V. Finotelli1; Maria H.M. Rocha-Leão2* 1Instituto de Química - Universidade Federal do Rio de Janeiro 2Escola de Química - Universidade Federal do Rio de Janeiro

Abstract. Over the last few years there has been a tendency in the food industry to fortify products with vitamins to cover the intakes recommended by competent organizations. In an attempt to improve its manipulation and distribution within the food and to obtain a product which is more nutritionally complete, the microencapsulation of vitamin C was studied. In this study, we produced microcapsules of ascorbic acid using an economical and simple process (spray drying) and three types of covering materials (derivates of starch). These materials are good substitute of gum Arabic because they cost less and they are available from different sources as potato and manioc. Ascorbic acid microencapsulation was carried out through the use of spray-dryer technique using maltodextrin, Capsul and a mixture of both as covering. Microcapsules containing 10 and 20% of ascorbic acid were produced. The morfology of the microcapsules was observed by a scanning electron microscopy, whose analysis showed a tendency of agglomeration. The outer surfaces of the capsules showed only a few pores or cracks. Particle size analysis showed a multi-modal particle size distribution, but with a main mode in intermediate diameters range (4 – 8 µm). Ascorbic acid stability was studied for particles stored, at both, room temperature and at 45oC showing 100% of retention at the beginning. Microcapsules containing 20% of ascorbic acid recovered by a mixture presented only 7% of ascorbic acid reduction in samples for up to 60 days stored at 28oC temperature.

Keywords: Microencapsulation; Spray Drying and Ascorbic Acid.

1. Introduction

Microencapsulation is defined as a technology of packaging solids, liquids, or gaseous materials in miniature,

sealed capsules that can release their contents at controlled rates under specific conditions (Dziezak 1988, Risch

1995). The miniature packages, called microcapsules, may range from sub-micron to several millimetres in size

and have a multitude of different shapes, depending on the materials and methods used to prepare them (Shahidi

et al 1993). Microencapsulation is also a method of protecting encapsulated material from factors that may cause

its deterioration as temperature, moisture, microorganisms, etc (Pothakamuryans et al 1995, Rosenberg et al

1990). Microencapsulation can reduce off-flavours produced by certain vitamins and minerals, permit time

release of the nutrients, enhance stability to extremes in temperature and moisture, and reduce reactivity of

nutrient with other ingredients (Dziezak 1988, Pszczola 1998).

Spray Drying is the most commonly used encapsulation method in the food industry. The process is

economical and flexible, using equipment that is readily available, and produces particles of good quality

(Rosenberg et al 1990, Reineccius 1988). The process of microencapsulation by spray drying involves 1)



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formation of an emulsion or suspension of coating and core material, and 2) nebulization of the emulsion into a

drying chamber containing circulating hot dry air (Jackson et al 1991). Water-soluble materials may also be

encapsulated. However, instead of having a clearly defined core and coating, the product consists of a

homogeneously blended matrix of polymer entrapping the core and they are also said to be covered with a very

fine film of coating (Dziezak 1988). In the case of solutions, the core and the polymer are co-dissolved in a

common solvent and spray dried. The solution is fed to the spray dryer and atomised. Upon solvent evaporation,

the polymer precipitates and entraps the precipitated crystal (Ré 1998).

Carbohydrates have been used as wall material to microencapsulate food ingredients. The food industry is

currently emphasizing the use of ‘natural’ rather than synthetic ingredients. The formulations are therefore based

on maltodextrins or starch hydrolysis products, on sugar, on polysaccharides derived from plants either terrestrial

or marine, or from microorganisms (Karel 1990). Maltodextrins are non sweet nutritive polysaccharides

consisted of: α(1-4)-linked D-glucose produced by acid or enzymatic hydrolysis of corn starch. Although

maltodextrins do not promote good retention of volatile compounds during the spray drying process, they protect

encapsulated ingredients from oxidation (Reineccius 1991, Ré 1998). Capsul is a chemically modified starch by

incorporation of lipophilic component. This modified starch provides excellent retention of volatiles during spray

drying and it can be used at a high infeed solids level (compared to gum acacia), and affords outstanding

emulsion stability (Shahidi et al 1993, Reineccius 1991, Marchal et al 1999). Other materials can be used to

microencapsulate the ascorbic acid. Esposito and co-workers (Esposito et al 2002) used methacrylate

copolymers called Eudragit for the production of ascorbic acid microcapsules by spray drying. This wall

material is able to offer a controlled delivery in different pH and it exhibits a very low permeability.

Vitamin C is also known as ascorbic acid, ascorbate, or ascorbate monoanion. It is the enolic form of an α-

ketolactone. Vitamin C works physiologically as a water soluble antioxidant by virtue of its high reducing power.

It acts as singlet oxygen quenchers, and it is capable of regenerating vitamin E. Vitamin C is called antioxidant

because of its ability of quenching or stabilizing free radicals that lead over time to degenerative diseases,

including cancer, cardiovascular disease, cataracts, and other diseases (Goodman & Gilman 1996, Rodrigues-

Amaya et al 1997, Hamilton et al 2000, Elliott 1999).

Ascorbic acid properties are impaired by its high reactivity, and hence, poor stability in solution, which can

result in heavy losses during food processing. It can be degraded rapidly in the presence of oxygen, free-radical

mediated oxidative processes. The processes are strongly catalysed by transition metal ions, specially iron and

cooper, leading to rapid destruction of the ascorbate. Oxidation is also accelerated at neutral pH and above.

Destruction can be occurred by presence of enzymes as ascorbate oxidase and a ascorbate peroxidase (Kirby et al

1991).

The food industry will likely employ microencapsulation to produce foods which are more nutritionally

complete. The properties of microencapsulated nutrients will allow the food processor greater flexibility and

control in developing foods with high nutritional value (Jackson 1991). Ascorbic acid is added extensively to

many types of food products for two quite different purposes: as a vitamin supplements to reinforce dietary intake

of vitamin C, and as an antioxidant, to protect the sensory and nutritive quality of the food itself (Kirby 1991).



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Therefore, the objective of this study was to produce microcapsules of antioxidant vitamin (ascorbic acid) by

spray drying using Capsul and maltodextrin for application in the food industry as fortification. Microcapsules of

vitamin C could be potentially incorporated in dry form into cake mixes, puddings, gelatine desserts, chewing

gum, milk powder, jellies, pet foods, breakfast cereals, in short, into products with low water activity. On the

other hand, for application in liquid food systems, the best way to protect water-soluble ingredients is by

encapsulation in lipossomes.

2- Materials and Methods

2.1. Microencapsulation of Ascorbic Acid

Wall solutions consisting of Capsul (National Starch), maltodextrin (MOR-REX 1920, DE=19-22) or a

mixture of maltodextrin with Capsul (1:1) were prepared in deionised water (65oC) and were cooled to 25oC.

Then, the core material, the ascorbic acid (Merck), was mixed with the wall solutions. Ascorbic

acid:carbohydrates weight ratios of 1:9 and 1:4 were used. In all cases, total solids content of feed solution was

10% (w/w). Spray drying of the feed solution was carried out in a BÜCHI 190, Büchi Laboratoriums-Technik

AG spray-dryer, at a feed rate of 20 ml/min, atomisation pressure 6 atm, inlet air temperature 190oC, outlet air

temperature 90oC, and atomizer beak diameter 0.3 mm.

2.2. Scanning Electron Microscopy

The morfology of the microcapsules was observed by a scanning electron microscopy (SEM), Jeol, model

JSM-5310, following methodology described by Sheu et al 1998. Microcapsules were attached to SEM stubs (10

mm) using a two-sided adhesive tape. The specimen was subsequently coated with gold, and analysed using

scanning electron microscopy operated at 15kV.

2.3. Particle Size Distribution Analysis

Particle size analysis was done in Mastersizer 2000 (Malvern Instruments, UK) equipment, following

procedure described into the manual of the equipment. This technique measures the size of particles dispersed in

a medium by the scattering pattern of a traversing laser light. Microcapsules were suspended in ethanol and

submitted to an ultrasound during 1.50 min. During the analysis (in triplicates), the samples were maintained in

constant agitation.

2.4. Stability Evaluation of Ascorbic Acid Microencapsulated

The stability of the encapsulated material was also studied for particles stored at both 28oC and at 45oC. The

samples were stored in a plastic bag, protected against gas and light. The analysis of ascorbic acid were made in

triplicate periodically up to 60 days using an UV spectrophotometric (λ=265 nm) method. The equipment used

was Perkin-Elmer Hitachi 2000. The ascorbic acid was released from the microcapsule by dissolution in

phosphate buffer (Na2HPO4 (Merck); KH2PO4 (Merck)) (pH=6.4), in order to that, 0,05g of sample was

dissolved into 50 ml of phosphate buffer with stirring. Then, this solution was diluted (400 µl/10 ml) and

analysed.



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2.5. Statistics Analysis

Analysis of variance (ANOVA) and LSD test procedures were evaluated to determine the differences between

the microcapsules in different times and between different samples under the same storage time, for that it was

used the STATISTICA 5.5 software.

3- Results and Discussion

3.1. Scanning Electron Microscopy

The morphology of microcapsules can be observed in Figure 1. One reason for using SEM in the research of

microencapsulation is the need to determine the encapsulating ability of various polymers. Indication of this

ability is given by the degree of integrity and porosity of the microcapusles (Rosenberg et al 1990).

(A) (B) (C)

(D) (E) (F)

Fig. 1. Structure of microcapsules: (A) Capsul + 10% Ascorbic Acid; Bar = 1 µm (B) Capsul + 20% Ascorbic Acid; Bar = 5

µm (C) Capsul/Maltodextrin + 10% Ascorbic Acid; Bar = 5 µm (D) Maltodextrin + 10% Ascorbic Acid; Bar = 1 µm (E)

Maltodextrin + 10% Ascorbic Acid; Bar = 5 µm (F) Capsul/Maltodextrin + 20% Ascorbic Acid. Bar = 5 µm.

Morphologic analysis showed the size, the shape and common aspects of the microcapsules made from

different wall materials and a tendency of agglomeration of the smallest particles between themselves and the

biggest ones was observed. Although the outer surfaces of the capsules had irregularities (some dents), they

showed only a few pores or cracks and they were predominant in microcapsules of ascorbic acid and Capsul. The



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presence of these dents has an adverse effect on the flow proprieties of microencapsulated product powders, but

they do not affect ascorbic acid stability. Many properties of a microencapsulated system result from its structure.

Retention and protection in a microencapsulated product are related to the porosity and degree of integrity of

microcapsules (Rosenberg et al 1990).

The outer surfaces of the spray-dried microcapsules are characterized by the presence of dents and these dents

are formed by shrinkage of the particles during drying and cooling, similar dents were observed in the study of

milk powder (Rosenberg et al 1985). Sheu et al 1998 have reported the morphological variations (size, structure

and appearance) of the droplets during the drying process. In many cases, these droplets, spherical in the

beginning, form particles with irregular surfaces (folds) due to internal formation of vacuoles and dents,

depression and external fracture.

According to Sheu et al 1998 spray-dried microcapsules with wall material consisting of polysaccharides

exhibit notable surface indentations and the formation of indentations has been attributed to effects of wall

composition, atomisation and drying parameters, uneven shrinkage at early stages of drying, and to the effect of a

surface tension-driven viscous flow. The thermal expansion of air or water vapour inside the drying particles

(‘ballooning’, associated with high drying rates) can smooth out dents (to a varying extent). The effectiveness of

dent smoothing is dependent of the drying rate and on viscoelastic properties of the wall matrix.

3.2. Particle Size Distribution Analysis

Particle size analysis showed a multi-modal particle size distribution for all samples, but with a main mode in

intermediate diameters range (4 – 8 µm). The graphics can be observed in Figure 2. The Table 1 shows the

particle size distribution.

(A) (B)

(C) (D)

(

E) (F)



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Fig. 2. Particle Size Distribution: (A) Capsul + 10% Ascorbic Acid; (B) Capsul + 20% Ascorbic Acid; (C)

Capsul/Maltodextrin + 10% Ascorbic Acid; (D) Maltodextrin + 10% Ascorbic Acid; (E) Maltodextrin + 10% Ascorbic Acid;

(F) Capsul/Maltodextrin + 20% Ascorbic Acid.

Table 1. Particle Size Distribution

Samples Diameter* (µµµµm)

d (0.1) d (0.5) d (0.9)

Capsul + 10% Ascorbic Acid 1.096 ± 0.003 6.267 ± 0.003 14.14 ± 0.01

Capsul + 20% Ascorbic Acid 1.38 ± 0.02 7.6 ± 0.1 24 ± 2

Capsul/Maltodextrin + 10% Ascorbic Acid 1.021 ± 0.002 5.83 ± 0.03 12.82 ± 0.07

Capsul/Maltodextrin + 20% Ascorbic Acid 0.967 ± 0.000 4.811 ± 0.004 10.89 ± 0.03

Maltodextrin + 10% Ascorbic Acid 0,971 ± 0,005 4.75 ± 0.08 10.30 ± 0.02

Maltodextrin + 20% Ascorbic Acid 1.030 ± 0.005 6.95 ± 0.06 18.1 ± 0.2

* Triplicates average

The smallest particles were produced by microcapsules containing maltodextrin and 10% of ascorbic acid

with diameter in the range 0.971 – 10.30 µm, and the main diameter was 4.75 µm. The biggest particles were

produced by microcapsules containing Capsul and 20% of ascorbic acid, the diameter ranging from 1.38 to 24

µm, and the main diameter was 7.6 µm.

Microcapsules whose wall material was Capsul/maltodextrin showed the narrowest size distribution, exactly

what we wished, because the narrower is the distribution the more homogenous are the particles so, this way, we

can obtain better stability and accuracy release.

3.3. Stability Evaluation of Ascorbic Acid Microencapsulated

Efficiency of encapsulation of ascorbic acid was determined by measuring the total amount of ascorbic acid

actually present in each 50 mg sample, i.e. core loading experimental, and comparing this value with the total

amount of ascorbic acid expected in each of the samples, i.e. core loading theoretical. The microcapsules showed

100% retention of ascorbic acid and this result agreed with Trindade et al 2000 that microencapsulated ascorbic

acid with arabic gum and starch. Esposito and others 2002 using Eudragit for microencapsulation ascorbic acid



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by spray drying obtained high encapsulation efficiencies, comprised between 98 – 100%. The retention obtained

in this work evidences the efficiency of microencapsulation with the wall materials tested, and it confirms that the

permanence time into drying chamber is short (5-30s) or at least, it is not the necessary time for ascorbic acid

degradation. Ascorbic acid was encapsulated inside liposomes by dehydration/rehydration procedure of Kirby

and others 1991. Although they got good ascorbic acid stability, the efficiency of encapsulation was less (53 e

58%) than the efficiency obtained in this work. Pure ascorbic acid was studied by Trindade et al 2000 and they

confirmed its instability in contact with the environmental. Margolis et al 2001 observed a significant decrease in

the concentration of ascorbic acid not microencapsulated when they tested it in different conditions. Pure ascorbic

acid was stored at room temperature and same conditions and it presented a significant decrease in the

concentration of ascorbic acid. In 30 days, 10% of ascorbic acid was degradated, 15% in 45 days and 20% in 60

days. Due to poor ascorbic acid stability it confirms the importance of microencapsulates this vitamin.

Table 2 shows the results of microcapsules analysis containing 10% of ascorbic acid stored at room

temperature, relating the percentages of retention. The three different wall materials offered the same stability for

ascorbic acid during the storage time (p<0.05).

Table 2. Retention of ascorbic acid at room temperature (1,2,3)

Wall Material % Tzero % T30 days % T45 days % T60 days

Capsul a100A a100

A b87A b81

A

Maltodextrin/Capsul a100A a100

A a91A b84

A

Maltodextrin a100A a100

A a90A b85

A

1. Microcapsules containing 10% of ascorbic acid

2. Average with different capital letter in the same column has significant difference (p<0.05)

3. Average with different small letter in the same row has significant difference (p<0.05)

The microcapsules of ascorbic acid and Capsul showed some reduction for 45 days storage (around 15%),

and they maintained constant until 60 days. The microcapsules whose wall material was Capsul and maltodextrin

showed reduction after 60 days storage (around 15%). The same results were found for microcapsules of ascorbic

acid and maltodextrin.

The results found for microcapsules containing 20% of ascorbic acid and stored at room temperature can be

observed in the Table 3. Statistically, differences (p<0.05) between microcapsules recovered by the mixture of

Capsul/maltodextrin and microcapsules recovered by Capsul and maltodextrin individually were observed.

Table 3. Retention of ascorbic acid at room temperature (1,2,3)



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Capsul a100A a100

A b91A b88

A

Maltodextrin/Capsul a100A a,b100

A b95B c93

B

Maltodextrin a100A a100

A b92A b88

A




During 45 days of storage, microcapsules of ascorbic acid recovered by Capsul and maltodextrin individually

presented reduction about 10%, meanwhile microcapsules of ascorbic acid recovered by the mixture

(Capsul/maltodextrin) presented reduction about 5%. Until 60 days, these last microcapsules had more 2% of

reduction, resulting in 7% of total loss and the other kept constant.

The Table 4 shows the results of stability analysis for microcapsules containing 10% of ascorbic acid stored

at 45oC. The statistical analysis showed again that there were no differences between the samples from the

different wall materials in relation to loss of stability.

Table 4. Retention of ascorbic acid at 45oC (1,2,3)


Capsul a100A b80

A b76A c61

A

Maltodextrin/Capsul a100A b77

A b76A c64

A

Maltodextrin a100A b77

A b72A b69

A




Microcapsules of ascorbic acid and Capsul had some reduction after 30 days (around 25%), keeping constant

in 45 days with a increase (35%) in 60 days. The same behaviour was identified for microcapsules of ascorbic

acid and Capsul/maltodextrin. It was observed some reduction for the microcapsules of ascorbic acid and

maltodextrin after 30 days (around 25%) and keeping constant until 60 days.

Finally, the Table 5 shows the results obtained for microcapsules containing 20% of ascorbic acid stored at

45oC. The statistics analysis confirmed that there was difference between microcapsules of ascorbic acid

recovered by Capsul and by maltodextrin after 45 days of storage.

Table 5. Retention of ascorbic acid at 45oC (1,2,3)



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Capsul a100A b83

A b81A c72

A

Maltodextrin/Capsul a100A b83

A b76A,C c65

A

Maltodextrin a100A b82

A c74B,C c70

A




All microcapsules presented reduction after 30 days of storage (around 20%). The ascorbic acid content was

kept constant from 30th to 45th day for microcapsules whose wall material was the Capsul and the mixture,

meanwhile microcapsules recovered by maltodextrin had a reduction (around 10%). After 60 days, microcapsules

recovered by maltodextrin kept its ascorbic acid content (30% loss) and the other had more reduction, resulted in

30% of loss.

The microcapsules that were stored at 45oC had more ascorbic acid content reduction than the microcapsules

that were stored at room temperature, and this confirms once more time that ascorbic acid can be destroyed by

high temperatures.

It was observed that microcapsules containing 20% of ascorbic acid showed better stability than

microcapsules containing 10% of it, that means that the sample with higher concentration was less susceptible to

degradation because the big amount of ascorbic acid created a resistance to the penetration (action) of oxygen

and light.

Trindade et al 2000 produced microcapsules of ascorbic acid (8 and 10%) with starch and arabic gum by

spray drying and evaluated its stability. He observed a good stability for microcapsules recovered by arabic gum

stored at room temperature, on the other hand, microcapsules recovered by starch suffered ascorbic acid

reduction (10-15%). In 30 days of storage at 45oC, the microcapsules had reduction from 20 to 55%.

4- Conclusion Based on the results obtained in the present studied, it can be recommended the use of microcapsules

containing 20% of ascorbic acid recovered by the mixture of Capsul/maltodextrin 1:1 for incorporation into some

food as cereals, bread, cookies, etc. This sample presented the best results. It was observed one of the highest

yields (52%), the smallest particles (4.8 µm), and only 7% of ascorbic acid reduction in samples for up to 60 days

stored at 28oC. Studies have confirmed that little particles offer better stability. The particle size analysis showed

a narrow particle size distribution for this sample, so the particles are more homogenous.

It could be observed some synergistic effect between Capsul and maltodextrin to encapsulate ascorbic acid,

and it is probably due to some structure interactions between the involved materials. The stability and

morphology results that presented by microcapsules whose wall material was the mixture had not much influence

from ascorbic acid content, differently for the others.



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Acknowledgements

This study was supported by the Brazilian Council for Scientific and Technological Development

(CNPq/Pronex). The first author is grateful to CAPES for the financial support. The authors also thank Humberto



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B. Novaes and Delmo S. Vaitsman from Laboratory of Analytical Development (LaDA-IQ/UFRJ), Laboratory

of Microscopy from Biophysics Institute (CCS/UFRJ) and Félix Cornejo from Empresa Brasileira de Pesquisa

Agropecuária (EMBRAPA) for their collaboration.

Documents

Encapsulation - Capsul Maltodextrin - Vit c