Use of edible films based on whey protein isolate to protect foods rich in polyunsaturated fatty acids

Abstract

Whey protein isolate (WPI) films acting as oxygen barriers can be used to delay lipid oxidation in foods with high content in polyunsaturated fatty acids (PUFA). The aim of this work was to study as to what extent WPI films are capable of delaying lipid oxidation in vegetable oil, as an example of a food rich in PUFA. The effect of plasticizer type (glycerol or sorbitol) and content (30, 40, 50 and 60%), as well as film thickness (60, 100 and 180 μm) and relative humidity (50 or 75%) were analyzed. In order to evaluate the film protective capability, specially designed methacrylate cells and an accelerated test of oxidative rancidity were used. Results obtained showed that WPI films delayed the rancidity in vegetable oil. Films with sorbitol were more effective than films with glycerol, providing a protection as effective as aluminum foil. Both plasticizer content and film thickness affected its protective capacity significantly. The thickest films with the lowest plasticizer content provided the greatest protection against lipid oxidation. Plasticizer content affected film protection much more intensively than thickness. WPI films presented a more effective protection at 50% RH than at 75% RH.