Physical properties and sensory evaluation of WPI films of varying thickness

The effect of varying thickness on the water barrier properties, tensile properties and sensory characteristics of glycerol-plasticised whey protein isolate (WPI) films was investigated. Thickness was varied by preparing films with increasingly dilute film forming WPI solutions in the range 9.5-2.3 g protem/100 g. All films had a glycerol to protein ratio of 0.37 (Gly: Pro). Tensile strength (TS), elastic modulus (EM) and film permeance were unaffected by film thickness but maximum load (NIL) and % elongation (E) decreased (P<0.05) with decreasing thickness. In a sensory test with crackers and melted cheese, panelists could readily detect the thickest films (79 mu m) but not the thinnest films (23 mu m) (P < 0.05). The results indicate that reducing the thickness of glycerol plasticised WPI films makes them less perceptible in a food system while maintaining moisture barrier and certain tensile properties. (C) 2003 Published by Elsevier Ltd. on behalf of Swiss Society of Food Science and Technology.