Encapsulation Applications in Food Industry

Introduction:

Encapsulation is a key process of trapping components (active) into a secondary material (encapsulant), resulting in small solid particles which will be able to release the active component at specific condition. This process is used commonly in the FMCG industry for masking unwanted flavours or to protect healthy ingredient during the shelf life of the product during new product development. Encapsulation process or encapsulated ingredients are used in every food product category such as confectionery, beverages, dairy, ready to eat snacks or mainly in convenience foods. Encapsulation in the food industry is projected to grow at a CAGR rate of 13.1% from 2017 to 2022. In the food ingredient market, the functional ingredients market has the largest share as the biomolecules are highly reactive. The encapsulation technology is implemented for ingredients such as vitamins, minerals, sweeteners, phytonutrients, antioxidants, enzymes, probiotics and essential oils, which are highly volatile. 

Purpose of Encapsulation:

In general, food scientist and food development companies are employing encapsulation process for specific purposes and used for volatile flavours, fortified ingredients with masked odour and taste, in ingredients to prevent oxidation and in products such as chewing gums which contains flavours for long-lasting effects. For instance, ingredients that are encapsulated include vitamins that need protection from the external atmosphere, moisture and flavourings that need to be released during mastication. Some researchers are experimenting with protein isolates, gums and carrageenan to protect cardamom essential oils in a dry powder, enhancing its hand ability and storability. There are other examples of encapsulation technology ingredients in consumer packaged goods. NutraShield™ caffeine technology was used to improve the taste of the caffeine. Proprietary consultation technologies to make Season-ettes™ granules less prone to moisture migration have shown better temperature stability. FlavorCell encapsulated liquid and solid flavourings where the flavour matrix was protected from heat, oxidation and more importantly moisture. A positive outlook for nutraceuticals is achieved and accompanied by encapsulation and market growth. 

Process in-detail:

The very first stage in the encapsulation process is the mixing of the active material with an encapsulant to form an emulsion. This emulsion is then dried to produce microcapsules of various sizes based on the preparation method.

Under the physiochemical method, there are simple or a complex coacervation method, splitting of organic and liposomal wrapping could be done. Under the Physical method, the commonly done method is spray drying, fluidized bed, extrusion and lyophilization. Finally, chemical methods are also available which will create interfacial polymerization and inclusion for the microencapsulation to be done.

Table 1 Methods used for encapsulation

Methods for encapsulation	Encapsulated materials
Physical methods
Stationary extrusion	Liquid/solid/gas
Submerged nozzle	Liquid/solid/gas
Centrifugal extrusion	Liquid/solid/gas
Vibrant nozzle	Liquid/solid/gas
Spray-drying	Liquid/solid
Rotating disc	Liquid/solid
Pan coating	Solid
Air suspension	Solid
Spray chilling and spray cooling	Liquid/solid
Fluidized bed	Solid
Co-crystallization	Liquid/solid
Lyophilization	Liquid
Chemical methods
Interfacial polymerization	Liquid/solid
Molecular inclusion	Liquid
In situ polymerization	Liquid/solid
Physical-chemical methods
Simple coacervation	Liquid/solid
Complex coacervation	Liquid/solid
Liposomes	Liquid/solid
Evaporation of the solvent	Liquid/solid

Coacervation:

This method is achieved when the encapsulant material is made from polymeric chain units, which reacts with other chains in the vicinity and results in aggregates forming high-intensity attraction forces. Then the aggregated polymer chains are deposited around the droplets of the hydrophobic phase dispersed in the emulsion to form a protective film. Key things to understand in this method are that these particles are irregular in structure as the encapsulant is not equally distributed over the active component. The diameter size range expected in complex coacervation is 1 to 500 μm and for simple coacervation is from 20 to 500 μm.

Spray drying:

This method is widely used in the industry for products such as juice, pulp, vegetal extracts, due to the low cost and easy application. During this process, a homogenous mixture of the active component and the encapsulant in a water-based or organic solvent is made. This wet mixture is subjected to a hot airstream which will evaporate the outer solvent and dry the microcapsules and leaves no solvent residue. Since a washing step is not required, it is highly recommended for fish oils and expensive bioactive components, which otherwise may compromise the integrity of the materials. Spray drying has a high-efficiency rate which is usually factored by the concentration of the encapsulant, speed of the system and the temperature. On the contrary, some researchers have indicated that spray drying results in porous particles and might increase the susceptibility of oxidation. Moreover, irregular microcapsules are also criticized. 

Fluidized bed:

In this food encapsulation technology the active component is suspended and the encapsulant is atomized into the chamber which gets deposited on the core. When the particles reach the top of the column, they are released into a column of air, reaching the fluidized bed once again. This time the microcapsules are coated gain, dried and allowed to harden ensuring a uniform coating. The fluidized bed encapsulation technique allows active components to be encapsulated with any wall materials, ranging from proteins, emulsifier, proteins and even fat.

Molecular inclusion is considered to be a promising possibility for flavour stabilization in the formation of an inclusion complex with β-cyclodextrin. Studies have shown that β-cyclodextrin is thermally destroyed at 260 ℃ and to achieve thermal stability it is included with γ-cyclodextrins. For instance, essential oils of lemon orange and chamomile have used a combination of both cyclodextrins. 

The release of the active component from the wall material regardless of the method of encapsulation will depend on factors such as pH, temperature, solubility, and biodegradation. Moreover, the final thickness of the wall material also affected the solubility and stability of microcapsules. 

Molecular inclusion:

Molecular inclusion is considered to be a promising possibility for flavour stabilization in the formation of an inclusion complex with β-cyclodextrin. Studies have shown that β-cyclodextrin is thermally destroyed at 260 ℃ and to achieve thermal stability it is included with γ-cyclodextrins. For instance, essential oils of lemon orange and chamomile have used a combination of both cyclodextrins. 

The release of the active component from the wall material regardless of the method of encapsulation will depend on factors such as pH, temperature, solubility, and biodegradation. Moreover, the final thickness of the wall material also affected the solubility and stability of microcapsules. 

Innovative Applications research in encapsulation developments:

1. Building wide ingredient options to build encapsulation shells
2. Preventing flavour and aroma loss for volatile compounds
3. Nutrient enhances ingredients
4. Improved flavour stability
   1. a. Fish oil without the fishy taste
5. Functional encapsulated ingredients
   1. a. Reduced bitterness in caffeine
6. Controlled ingredient release 
7. Better leavening and baking is achieved
8. Better matrices are built using starches
9. Protecting multi nutrients from thermal and biochemical degradation
10. Fighting food adulteration

References:

1. Mwangi, W. W., Lim, H. P., Low, L. E., Tey, B. T., & Chan, E. S. (2020). Food-grade Pickering emulsions for encapsulation and delivery of bioactives. Trends in Food Science & Technology.
2. Akbari-Alavijeh, S., Shaddel, R., & Jafari, S. M. (2020). Encapsulation of food bioactives and nutraceuticals by various chitosan-based nanocarriers. Food hydrocolloids, 105, 105774.