Effects of plasticizer levels (glycerol, 16.7-41.2%, w/w dry basis), temp. (15-40degreesC) and RH (30-85% RH) on the physical properties (including oxygen permeability (OP), gloss, haze and colour) of whey protein isolate (WPI)-coated films were determined, to investigate using the WPI coating as an alternative oxygen barrier for food packaging. LDPE film of 53.7 +/- 0.9 mum thickness was used as a substrate for the whey protein coatings. Corona discharge surface pretreatment improved the ability of the LDPE films to adhere to the whey proteins. Glycerol levels 15% (w/w, dry basis) had good appearance, flexibility and adhesion. OP of the coated films was dependent on both temp. and RH ; as temp. increased from 15-40degreesC the films showed a marked increase in OP, increasing approx. 2x for every 10degreesC temp. rise. WPI coatings and glycerol levels did not markedly affect the gloss, haze or colour values of the films. Results indicated that WPI-coated films had better oxygen-barrier properties than uncoated LDPE films at low to intermediate RH, and have potential for replacing existing synthetic oxygen-barrier coatings on LDPE films.
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