Edible coatings with food additives

Semi-permeable membranes, such as those used in ultrafiltration, have many potential applications in the food industry. Ishikawa and Nara (1992) pointed out, however that the main problem with these systems was the permeation of the solute used in osmosis into the foodstuff. This could be controlled by the use of a semi-permeable membrane placed in intimate contact with the food, that is, with no free space between the membrane and the food. They investigated the use of a membrane made from a chitosan gel. Chitosan is prepared from chitin, a glycan separated commercially from the shells of crustaceans. Chitosan is both semi-permeable and edible. They postulated that food could, therefore, be coated with a chitosan membrane, thereby eliminating any free space. As yet, chitosan is not permitted as an additive in foods, but this technique may find wide applications in the food industry if chitosan were to be accepted as a processing aid for foodstuffs. 

Edible films and coatings are produced from edible biopolymers and food-grade additives. Film-forming biopolymers can be proteins, polysaccharides (carbohydrates and gums) or lipids. Plasticizers and other additives are combined with the film-forming biopolymers to modify the physical properties or functionality of films. The composition of the film must be chosen according to specific food applications, the type of food products and the major mechanisms of quality deterioration. 

The protective function of edible films and coatings may be enhanced with addition of antioxidants or antimicrobials to the films or coating. Depending on the nature of the food, food additives, such as, flavors, nutrients or colors can be incorporated into edible films and used to control location or rate of release of these additives in a food. 

The substituted phenols and cresols constitute about half the total volume of this group. Para-t-butylphenol is produced by the alkylation of phenol with isobutylene. The principal applications for this derivative are in the manufacture of modified phenolic resins for the rubber industry and in surface coatings. BHT is obtained from isobutylene and p-cresol. Technical-grade BHT is an antioxidant for plastics and elastomers, and is a gum inhibitor in gasoline. Food-grade BHT is an antioxidant in edible oils, preserves, and many other foods. 2,6-Di-t-butylphenol is used to produce a wide range of plastics additives, antioxidants, and gasoline additives. 

---