Use of the enzyme transglutaminase to prepare hydrocolloid-based edible films suitable for the food industry

Edible films can be an alternative to chemically synthesized polymeric films that have been assessed not safe for both human health and the environment. The edible film components are usually hydrocolloids and/or lipids. Typical hydrocolloids for edible film production are proteins and polysaccharides, both highly represented in food processing by-products. Films made of these macromolecules, while possess good gas barrier properties towards oxygen and carbon dioxide, exhibit poor mechanical resistance and, due to their hydrophilic features, are somewhat too water-sensitive for applications in foods with high and intermediate moisture (Krochta and Mulder-Johnston, 1997). A strategy to improve hydrocolloid films containing proteins is to create a net structure introducing covalent cross-links. Despite recurring to chemical cross-linkers, it is advisable to use enzymes able to covalently bind proteins. Transglutaminase (TGase), catalyzing the formation of isopeptide bonds between endoprotein glutamine and lysine residues, is an effective tool in reticulating protein component of hydrocolloid-based films as we have recently reviewed (Mariniello et al., 2008). In this work we have obtained edible films recurring to grapefruit albedo homogenates and phaseolin. Films were obtained by casting in the absence and in the presence of the enzyme and characterized for their mechanical and barrier properties. Results indicate that TGase-containing films exhibit features comparable to those of other TGase-made films previously prepared in our laboratories (Mariniello et al., 2008) and of the already commercialized products Ecoflex and MaterBi. Thus albedo-phaseolin films made in the presence of TGase possess features that suggest a wide and healthy use in food industry.