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ASEAN Food Journal 14 (1): 1-14 (2007) Microencapsulation of Vitamins 1
Review Paper
Microencapsulation of Vitamins
Wilson, N. and *Shah, N.P.
School of Molecular Sciences
Victoria University
PO Box 14428 Melbourne, Victoria 8001, Australia
INTRODUCTION encapsulation technique has been utilised in
the pharmaceutical industry for the past 30
Functional foods are beginning to play a major years to offer controlled release of drugs to
role in what consumers buy and eat. The the body (Rosinski et al., 2002). It is relatively
International Life Science Institute has new to the food industry and is finding use in
defined a functional food as ‘a food which has maximising the retention of the bioactivity of
a beneficial effect on one or more target the components during the processing and
functions of the body, above and beyond the storage of the formulated product and
usual effects of food, such as improving the delivering the desired bioactive components
state of health and well-being or reducing the to the target site of the body (Korhonen,
risk of disease. Examples of these types of food 2002). Microencapsulation has been used to
include folate addition to breakfast cereals to encapsulate fish oil to increase n-3
reduce the risk of neural tube defects in the polyunsaturated fatty acid intake (Higgins et
developing fetus, milk fortification with al., 1999), to encapsulate probiotic bacteria in
calcium to combat osteoporosis and addition frozen dairy foods (Shah and Ravula, 2000)
of omega 3 to breads to aid in reducing heart and among other things, to encapsulate 2-
disease. Currently, health claims are illegal on acetyl-1-pyrroline (ACPY; a major flavour
food packaging in Australia (except for claims component of aromatic rice) to retain this
relating to folate). Food Standards Australia flavour component upon storage
and New Zealand are reviewing this legislation (Apintanapong and Noomhorn, 2003).
to allow general health claims by mid 2006
(Herald Sun, 27/05/05).
Some nutrients do not remain in the food MICROENCAPSULATION
for a significant amount of time or may react
with the other food components causing Microencapsulation is the creation of a barrier
undesirable effects. Microencapsulation is a to avoid chemical reactions and/or to enable
technology that can improve the retention the controlled release of the ingredients
time of the nutrient in the food and allow (Vilstrup, 2001). It involves mass transport
controlled release at specific times, during behaviour in some way between the core (the
food consumption or in the intestinal gut. It ingredient) and the shell (capsule or coating).
is not a new technology and was first The entrapped material is usually a liquid but
commercially applied in 1954 for carbonless may be a solid or a gas. Table 1 outlines the
copy paper (Dziezak, 1988). Micro- reasons why the food industry applies
microencapsulation.
*Corresponding author.
E-mail adress: Nagendra.shah@vu.edu.au (Shah, N.P.)
ASEAN Food Journal Vol. 14, 1-14
2 Wilson, N. and Shah, N.P.
Table 1: Reasons why the food industry applies microencapsulation
1. To reduce the reactivity of the core in relation to the outside environment
(eg, light, oxygen and water)
2. To decrease evaporation rate of the core material to the outside environment.
3. To promote easier handling of the core material to:
- prevent lumping
- give a uniform position of the core material
- convert a liquid to a solid form
- promote easy mixing of the core material.
4. Control the release of the core material to achieve the proper delay for the right stimulus.
5. To mask the core taste.
6. To dilute the core material when it is used in only small amount but still achieve uniform distribution.
Adapted from Shahidi and Han (1993).
Figure 1: Diagram of two representations of microcapsules: (A) continuous core surrounded by
continuous shell; (B) core material dispersed in a matrix of shell material
The capsule is very small in size, and hydrophilic material is protected by a
approximately 5 – 300 micron in diameter hydrophobic shell. The shell can consist of
(Gibbs et al., 1999). It can consist of a one or more materials. The shell of the
continuous core region surrounded by a capsule is designed to prevent diffusion of the
continuous shell or it can have irregular core material into the food until the desired
geometry consisting of small particles of core time. Its functions involve protecting sensitive
material dispersed in a matrix of shell material food components such as flavours, vitamins or
(Vilstrup, 2001). This is shown by a schematic salts from water, oxygen or light, converting
diagram in Figure 1. Generally a hydrophobic liquids that are difficult to handle into free
core is usually protected by a hydrophilic shell, flowing powders, and isolating specific food
ASEAN Food Journal Vol. 14, 1-14
Microencapsulation of Vitamins 3
Table 2: Approved food grade capsule shell material (Vilstrup, 2001)
Polysaccharides Fats and waxes Proteins
Gum Arabic Hydrogenated vegetable oils Gelatins (types A and B)
Modified starches Bees wax Whey proteins
Hydrolysed starches (maltodextrins) Soy proteins
Alginates Sodium caseinates
Pectin
Carrageenan
components from other food components Release Mechanisms
during storage. Some microencapsulated materials are made
for controlled release of the microencapsulant,
Capsule Material perhaps during processing, storage or during
There are a number of commercially approved final preparation prior to consumption. Food
shell materials available to produce various additives which may benefit from controlled
microencapsulated foods. Table 2 outlines release capsules include preservatives, redox
approved food-grade capsule materials. Not agents, colours, sweeteners and enzymes.
all shell materials meet all the properties Commonly used methods for controlled
needed, so they are often used in combination release in foods include temperature and
with other coating materials with other moisture release for hydrophilic encapsulants,
modifiers such as oxygen scavengers, and thermal release for fat capsules (Risch and
antioxidants, chelating agents and surfactants Reineccius, 1995). Other release methods
(Shahidi and Han, 1993). Carbohydrates such include pH control, addition of surfactants,
as starch and cyclodextrins have good ability enzymatic release, ultrasonics, grinding, and
to absorb volatiles from the environment. This photo-release.
makes them good for flavour encapsulation.
Gum Arabic is a commonly used capsule
material due to its viscosity, solubility and MANUFACTURING TECHNIQUES
emulsification characteristics but its cost is a
major disadvantage. Alginates and There are numerous methods for micro-
hydrocolloids are extracted from kelp and encapsulation of food ingredients but no
react with calcium ions to form a stable gel. single encapsulation process is adaptable to all
They can then be used to entrap flavour oils core materials or product applications. Table
at ambient temperatures. 3 outlines common methods used to
Protein based materials are able to form encapsulate food ingredients.
stable emulsions with volatile flavour Three steps are generally involved
components but their solubilities in cold water, including formation of the wall around the
potential to react with carbonyls and high cost material, ensuring that leakage does not occur,
limit their application. Ethyl cellulose is a good and ensuring that undesired materials are kept
material to encapsulate water soluble vitamins out.
because it is water soluble itself and as the shell
thickness increases, the water permeability of Spray Drying
the core vitamin is reduced (Shahidi and Han, Spray drying is the most common methods
1993). used for microencapsulation because it is
economical. It is also one of the oldest
ASEAN Food Journal Vol. 14, 1-14
4 Wilson, N. and Shah, N.P.
Table 3: Methods for encapsulating food ingredients
Encapsulating method Food ingredients
Spray drying Vitamins, flavours, starter cultures carotenoids, fats and oils,
clouding agents.
Spray cooling and spray chilling Ferrous sulphate, vitamins, minerals, acidulents.
Extrusion Vitamin C, visible flavour pieces, colours and extension of shelf life.
Fluidised bed coating Vitamin C, citric acid, lactic acid, sorbic acid, sodium bicarbonate
in baked goods.
Liposome entrapment Delivery of vaccines, hormones, enzymes and vitamins in to the
body.
Coacervation Vitamin A
encapsulation methods used originally in the established with 15% wall material and air
o
1930’s to encapsulate flavours using gum entry temperature of 150 C. Uddin et al.
acacia (Shahidi and Han, 1993). The basic (2001) found that the loss of ascorbic acid
steps involved in spray drying include during encapsulation by spray drying was only
preparation of the dispersion or emulsion to 2%.
be processed, homogenisation of the
dispersion, and atomisation of the mass into Spray Chilling and Spray Cooling
the drying chamber. It is a challenge to encapsulate water-soluble
The materials used for the capsule are food ingredients for protection during the
food grade hydrocolloids such as modified shelf life of the food. It is often difficult to
starch, maltodextrin and gums (Gibbs et al., find a good food grade barrier that will prevent
1999). The material should have good leaching of its water into the food. Spray
emulsifying properties, be a good film former, chilling and cooling are ideal methods for such
have low viscosity and provide good protection cheeses. Schrooyen et al. (2001) encapsulated
to the encapsulated ingredient. vitamin C for applications in solid foods such
The carrier is hydrated in water. The as cereal bars, biscuits and bread. The methods
ingredient to be encapsulated is added to the are similar to spray drying in that they disperse
carrier and homogenised. An emulsifier may a core material into a liquified coating and
also be added at this stage. The ratio of then atomised. However, the air temperature
encapsulant to carrier is usually 1:4 (Gibbs et is cooler than that for spray drying, and
al., 1999) but this can be optimised for each ambient temperatures are used for spray
individual ingredient. This mixture is then fed cooling and refrigeration temperature for
into the spray dryer and atomised with a nozzle spray chilling. The wall material is a molten
or spinning wheel. Water is evaporated by the fat or wax. Spray cooling uses a vegetable oil
o o
hot air (100-160 C) and the small particles are with a melting point in the range of 45-122 C.
deposited to the bottom of the spray dryer Spray chilling uses a fractionated or
where they are collected. The air temperature hydrogenated vegetable oil with a melting
o
can be optimised to produce the maximum point in the range of 32-42 C (Risch and
retention of encapsulant. Dib Taxi et al. (2003) Reineccius, 1995). The microcapsules
studied the microencapsulation of camu-camu produced are insoluble in water due to the
juice. It is a fruit from the Amazon with high lipid coatings.
vitamin C content. The optimum conditions Frozen liquids, heat-sensitive materials and
for juice yield and vitamin C retention were those not soluble in the usual solvents can be
ASEAN Food Journal Vol. 14, 1-14
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