© 2003 CDRF
Comment or suggestion to Site Editor
Crystallization Inhibitor Effect on the Rate of Gloss Fade of Whey Protein Coatings
By,
K.L. Dangaran, J. Renner-Nantz and J. M. Krochta
Department of Food Science and Technology
University of California, Davis
Edible coatings protect food from chemical, biological and physical
damage. Water-based whey protein isolate (WPI) coatings plasticized with
sucrose are high-gloss, durable oxygen barriers that could be an
alternative to ethanol-based shellac. However, during long-term storage
the gloss of WPI/sucrose coating fades. It is hypothesized that
amorphous sucrose transforming to the crystalline state causes the loss
of gloss. Preventing sucrose crystallization in WPI/sucrose coatings
would hinder gloss fade and keep desirable mechanical properties.
The objective of this study was to determine the effect of sucrose
crystallization inhibitors on gloss and rate of gloss fade of WPI/sucrose
coatings. The studied inhibitors were lactose, raffinose, modified
starch and polyvinylpyrollidone. WPI/sucrose-without-inhibitor coating
and shellac coating were also applied to the chocolates as controls.
The six different coatings were applied to chocolate-covered peanuts.
The WPI/sucrose-coated chocolates were divided and transferred to 23%,
33% and 44% relative humidity environments held at constant temperature.
Gloss of the chocolates was measured periodically with a Tricor Gloss
Analysis System model 801.
Collected gloss data show that the initial gloss level of WPI/sucrose
coatings containing raffinose was higher than all other coatings except
shellac. WPI/sucrose-raffinose coating had an average initial gloss
value of approximately 200, 25 units higher than the WPI/sucrose control
and only 15 units lower than shellac (on scale from 0 to 274). For all
WPI/sucrose coatings, it was found that as relative humidity of storage
conditions increased, the rate of gloss fade increased.
Results indicate raffinose may be a good inhibitor of gloss fade caused
by sucrose crystallization in WPI/sucrose coatings. Storing WPI/sucrose
coated foods in relative humidity lower than 44% would also further
hinder gloss fade. This information could be used to develop high gloss,
water-based WPI coatings that do not experience loss of gloss and
durability over time.
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.