Encapsulation:- an essential technology for functional foodapplications

By Denis Poncelet, ENITIAA, UMR CNRS 6144, 44322 Nantes cedex,France

poncelet@enitiaa-nantes.fr

Since the last world war more than 60 years ago, we assisted in a

revolution on the improvement of production methods leading to an

abundance of food in our occidental countries unknown to mankind before.

Our fridge is full! This abundance is also associated with a diversification

of the foodstuffs. Some products formerly considered as "luxury" find their

place in our quasi daily food (salmon, duck fillet …); fruits and vegetables

reach us from all over the world.

The abundance has driven people to request more from the food they eat

over and above energy supply; for example, to provide safety, health, and

why not--- fun.

‘Food mutation’

However, there is another equally important revolution in our society.

From traditional and familial "cuisine", we have moved to industrial

cooking, to consume as catering (fast food) or to bring back home.

Recomposed powders, mixes, storage period extension, and the need for

innovation have fundamentally modified the handling foodstuffs. It is

simpler and less costly for industry to transport, store and rehydrate dried

powders than to transport hydrated food products. Unfortunately,

dehydratation often has negative effects on the texture, flavour and

solubility of the rehydrated food. It is frequently necessary to supply food

powders with their inherent aromas, vitamins, and other properties. In

this context and application microencapsulation has become a highly

important tool for food process engineers. Protection during storage or

processing, released at the right time and place (e.g. during cooking), the

encapsulated additive will provide all its potential to the food.

Vitamin A

Vitamin is deficient in Asian foods and has to be supplied. The initial

proposal was to incorporate vitamin A into glutamate, a taste enhancer

used in these countries. However, Vitamin A is yellow and turns brown on

oxidation while glutamate salt must be white to be appreciated by

customers. Coating Place (USA) has developed a process for coating

particles of vitamin A, colorizing them in white, while offering protection

against oxygen, humidity and light.

Pro- and prebiotics

Traditional foods contain many different bacteria beneficial for health.

However, the pasteurization and long-term storage leads to food with a

reduced concentration of these bacteria. It was then proposed to

supplement food with selected health-support bacteria, i.e. probiotics.

However, the most efficient ones are generally fragile cells and need

protection, for example, by microencapsulation. In the frame of a

European project (MEPPHAC), we have demonstrated that coating

probiotics can enhance their survival by a factor 20 during warm pellet

extrusion. Microencapsulation allows the mixing of probiotics with

materials promoting their growth and attachment in the intestine (i.e.

prebiotics). It is then possible to develop optimum cocktails of probiotics

and prebiotics in a single formulation called synbiotics.

Spices and herbs

Aromas, spices and herbs constitute the core of pleasure-linked cuisine

and eating. However, they also represent the first natural functional foods.

They interact with the other food ingredients during storage, freezing, and

pre-cooking resulting, sometimes, in off flavours and loss of health

potential properties. Microencapsulation protects them during these stages

while releasing them, for example, during cooking. Microencapsulation

offers, therefore, a unique approach for maintaining optimum quality and

nutritive status in a range of foodstuffs.

New properties and functions

Encapsulation is a performing tool that confers new properties to normal

materials. Obtaining a stable functional ingredient is inadequate if it

cannot be easily integrated in the food.

Many vitamins, plant extracts and unsaturated acids are hydrophobic and

dispersing them in hydrophilic food powders is a real challenge. In

addition to protecting them, microencapsulation allows their conversion to

suitable and managable powders. Similary, by encapsulation, brown sugar

can be converted to a free flowing powder, suspended with hydrophobic

vitamins in juice, or dispersed in cocoa or in cold milk.

Unsaturated fatty acids are recognized as beneficial for health. However,

they sometimes have an unpleasant taste, which can become

unacceptable when they are oxidized. Encapsulation largely overcomes

this problem by taste masking. Moreover, incorporating flavours in the

coating helps to make the functional food pleasant to consume. This is

application is used extensively in pet food supply as animals will refuse

off-flavored ingredients.

Functional food ingredients may be incorporated into food or may be

consumed independently as pills or fine powder. This does not require a

prescription from a doctor. However, consumers must be advised to limit

their daily dose. This can be assisted by coating particles with a colouring

material thus differentiating the nutraceutics from a drug or a food.

Listeria represents a high risk in processed meat. We have developed an

encapsulation system consisting in a core containing two substrates

(glucose and thiocyanate), coated with two enzymes, and then protection

polymers. In the dry form, the mix is stable for long periods, but on

contact with moisture releases an end-product with high bacteriostatic

properties against listeria.

Innovation tool

Encapsulation can also be used as a tool for innovation. For example,

Orbitz (Canada) sells a drink containing a suspension of coloured capsules

containing different aromas and/or some vitamins, thus making functional

food consumption a ‘fun experience’. Salvona (USA) has developed

encapsulation technologies allowing sequential release of aromas and

sensory ingredients in functional foods.

Finally, microencapsulation can be used as a biocatalyst immobilization

system to process food in a safer and more efficient manner. For example,

reduction of ripening time and increased shelf life of cheese by processing

with an encapsulated enzyme.

The number of applications for microencapsulation technologies in foods,

and especially functional food, is increasing. However, many challenges

still remain. For example, incorporation of water sensitive ingredients in

high moisture foods is not solved because most capsules impermeable to

water are not soft and will be detected by consumers. In January 2008,

BRG (see below) organized a workshop in Switzerland on flavour

encapsulation. A consensus between the one hundred participants was

that 83% of applications relate to one single technology (spray drying)

and so there is a need for innovation.

Developing encapsulated functional foods

The principle of most technologies of encapsulation is quite simple:

Active ingredient is mixed within a polymer solution; dispersed as

fine droplets (spraying, dripping, emulsification); droplets solidified

by gelation; drying; cooling; coacervation …

Or, when a solid powder, particles are mixed in a fluid bed or a

pan; coating solution spray applied to them; solidify by drying or

cooling.

However, several constraints make the development of the encapsulation

process difficult. Firstly, encapsulation is an extra cost, which has to be

minimized. This applies to materials used to build the capsules but also to

equipment or processing conditions. We have computed that continuous

coating processes reduce the running cost by a factor 3 in comparison to

equivalent batch processes.

Materials used for encapsulation in the food domain are very limited

(some polysaccharides, a few lipids…). In pharmaceutical industries,

despite the strict rules to be respected for approval, they have access to

many more materials. In food, the engineer has to play finely with the

formulation to achieve adequate properties in the membrane of the

coating.

Most functional ingredients are sensible to water, oxygen, light and

temperature. Materials must, therefore, offer barriers to water

(hydrophilic) and oxygen. Careful temperature control during processing is

a major requirement. Moving from the so-called Wurster coating process

to a spouted bed process reduces temperature gradients (15ºC) in the

reactor, thus increasing probiotic surviving by a factor two.

Developing an encapsulated product is, therefore, a challenge, requiring a

multi-disciplinary and integrated approach. Many encapsulation

technologies currently exist, but many of are still at the development

stage. Finding the most suitable partners for such development and

production is a hard task.

Finding support for developing encapsulated functional foods

Fortunately, the scientific and industrial community are organizing

themselves in this regard. The Bioencapsulation Research Group (BRG)

(http://bioencapsulation.net) is probably one of the largest non-profit

associations on applied microencapsulation with 2000 members over 80

countries. It organizes conferences, industrial workshops and provides

information through its web site and news. Its next international

conference (http://bioencapsulation.net/XVI_ICB) will take place in Dublin

in September 2008. BRG will organize in the beginning of 2009 the largest

industrial symposium and trade fair in the encapsulation field. The COST

865 programme/project (http://COST865.bioencapsulation.net) is a

European platform for exchanges between researchers and industrialists

on developing collaborative projects in the microencapsulation area and

for publishing thematic books on encapsulation.