Food industry applications of spray coating

The use of encapsulated substances has been present in the industry since almost five decades, and is widely used in the pharmaceutical industry for time-release drugs and flavor masking [1]. In this process, the entrapped material –the carrier-, usually a liquid but also solids and gases, can be protected from heat and moisture by the outer material –the capsule-, increasing its stability. The main goal of this technique is to preserve the content from the environment while allowing small molecules pass through the capsule. In the last years, these techniques have become increasingly important also in food industry.

Capsules used in food industry are usually water-soluble in order to protect the properties of ingredients such as enzymes for long periods of time. Most common encapsulated compounds are oils, spices, seasonings, sweeteners, pH buffers, enzymes, antioxidants, vitamins or colorants [2], that are encapsulated in starch, cellulose, waxes, gelatins or soy proteins capsules. A complete review of all these edible coatings can be found in Kester, J. J., & Fennema, O. R. (1986). [3]

Food industry

Image: encapsulated particles formation via spray coating

There are various procedures to obtain encapsulated compounds for food industry, but most of them include spray techniques [1]:

  • Spray drying: Commonly used for flavors and for dehydrated compounds such as powdered milk encapsulated by starch, maltodextrinor gum. The encapsulation material is homogenized with the carrier usually at a proportion of 1:4. The mixture introduced into a spray device with hot air supply and atomized with the nozzle. The hot air in contact with the materials evaporates water and the resulting capsules are collected on the bottom of the drier.

 

  • Spray cooling: The procedure is analogous to spray drying, but in this case, the compounds are atomized by cooled air. This process allows to encapsulate frozen liquids and heat sensitive compounds that cannot be atomized by hot air, such as ferrous sulfate, minerals and vitamins. The carriers are eventually released as the encapsulating material is melted.

 

  • Fluidized bed: fluidized bed or air-suspension coating allows to apply thin coatings to powder particles by the atomization of the coating material into a bed of fluidized particles. The coating fluid impinges and spreads on the particle surface and the air evaporates the solvent. [4,5]. Many dry foods and dry nutritional mixes contain fluidized bed encapsulated compounds. Citric and lactic acid, vitamin C and sodium bicarbonate in baked foods, or salt added to meats are encapsulated through this technique [1].

Fluidized bed

Image: fluidized bed

 

[1] F. Gibbs, Selim Kermasha, Inteaz Alli, Catherine N. Mulligan, B. (1999). Encapsulation in the food industry: a review. International journal of food sciences and nutrition, 50(3), 213-224.

[2] Kirby CJ (1991): Microencapsulation and controlled delivery of food ingredients. Food Sci. Technol. 5, 74-78.

[3] Kester, J. J., & Fennema, O. R. (1986). Edible films and coatings: a review. Food technology (USA).

[4] Werner, S. R., Jones, J. R., Paterson, A. H., Archer, R. H., & Pearce, D. L. (2007). Air-suspension particle coating in the food industry: Part I—State of the art. Powder Technology, 171(1), 25-33.

[5] Dewettinck, K., & Huyghebaert, A. (1999). Fluidized bed coating in food technology. Trends in Food Science & Technology, 10(4), 163-168.

© Nadetech Innovations 2017

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