83B-1 |
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S.-Y. LIN and J. M. Krochta. Dept. of Food Science & Technology, Univ. of California, Davis, 1 Shields Ave., Davis, CA 95616 Whey protein films are excellent oxygen barriers and thus have potential to be formed as coatings on peanuts to extend their shelf life. However, adhesion of hydrophilic whey protein coatings to hydrophobic foods such as peanuts is inherently poor due to differences in the chemical nature of the two surfaces. To improve the adhesion of whey protein coating on peanuts, this research aimed at two techniques, surfactant adsorption and mechanical interlocking. The objectives were to increase the surface energy of peanuts by modifying the peanut surface by surfactant solution treatment and by mechanical roughening. Peanuts were coated with 10% (w/w) whey protein isolate (WPI) solution with Span 20 addition at 0.05% (w/w) or lecithin addition at concentration of 0.15 or 0.4% (w/w). Coating coverage was measured by analyzing the digital image of coated peanuts with the Image-J program. Peanuts were also tumbled in a customized pharmaceutical friabilator to increase the surface roughness. Roughened peanuts were coated and coating coverage measured. Coating peanuts with WPI coating solution including 0.05% (w/w) Span 20 resulted in 97% coating coverage. A 70% coating coverage of peanuts was achieved with WPI coating solution including 0.15% (W/W) lecithin, a natural food surfactant. A substantial improvement of coating coverage on peanuts was achieved with WPI coating solution including 0.4% (w/w) lecithin due to rapid adsorption of lecithin onto the peanuts and formation of self-assembled structures. The improvement of peanut coating coverage with lecithin-added WPI coating solution should improve the coating durability. Roughening of the peanuts surface should also improve coating adhesion by increased mechanical interlocking between coating and peanut surface. Thus, the oxygen-barrier function of the coating would be maintained. The shelf life of peanuts would be substantially improved due to this improvement of coating adhesion on peanuts.
Session 83B, Food Packaging: Applications of edible coatings, antimicrobial films, and sensors in food packaging
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