2 nd Mercosur Congress on Chemical Engineering 4 th 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]1 MICROENCAPSULATION OF ASCORBIC ACID IN MALTODEXTRIN AND CAPSUL USING SPRAY-DRYING Priscilla V. Finotelli 1 ; Maria H.M. Rocha-Leão 2 * 1 Instituto de Química - Universidade Federal do Rio de Janeiro 2 Escola 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 45 o C 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 28 o C 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)
Spray drying of vitamin c by using Capsul & Maltodextrin as filler
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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]
1
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)
2nd Mercosur Congress on Chemical Engineering
4th Mercosur Congress on Process Systems Engineering
2
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