The purposes of this review are: 1) to provide insights into how proteins are used for the encapsulation of food ingredients; and 2) evaluate their performance in this role. Proteins possess functional properties that are critical to the successful spray drying and coacervation processes. In spray drying, they serve as excellent emulsifiers. The initial step of any spray drying process is the formation of an emulsion: emulsification serves to distribute a bioactive material throughout the wall material on drying. For complex coacervation, proteins serve as one half of the wall material, that is, serving as a positively charged food polymer which forms ionic bonding to a negatively charged food polymer most commonly a food gum. In terms of performance, high encapsulation efficiency and stability against oxidation on storage are key roles proteins must offer. This review considers encapsulation performance of proteins for flavorings as a separate section from nonvolatile bioactives (e.g. colorants, edible oils, or other bioactives). Due to the chemical reactivity of proteins, they find limited use for the encapsulation of flavorings (by spray drying or coacervation). However, they can be excellent for the encapsulation of other food ingredients. While in spray drying the use of proteins can be effectively avoided by using a modified starch or a gum such as gum acacia for emulsification, coacervation offers little alternative to proteins as a positively charged polymer forming part of the coacervate wall (chitosan is the only alternative). Since proteins cannot easily be avoided in coacervation, this process may be used for the encapsulation of ingredients other than flavorings.
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