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Improved Whey Protein Coating Efficiency on Surfactant-Modified Hydrophobic Surface
By,
D. S. Lin and J. M. Krochta
Department of Food Science and Technology
University of California, Davis
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.
For more information on Dr. Krochta’s work and the Food Science and Technology Department at UC Davis, please visit Dr. Krochta's Web site - http://foodscience.ucdavis.edu/fst/faculty/KrochtaWeb/index.htm.