© 2003 CDRF
Comment or suggestion to Site Editor
Modeling Shelf-life of Whey-protein-coated Peanuts Analyzed by Static-Headspace Gas-chromatography
By,
S.-Y.LEE and J.M.Krochta
Department of Food Science & Technology
University of California, Davis
Lipid oxidation in peanuts results in 'flavor-fade' and off-flavor development. Whey-protein-isolate (WPI)-based films have been found to be excellent oxygen barriers. Thus, we hypothesized that WPI films formed as coatings on peanuts would reduce peanut lipid oxidation. The objectives of this study were to determine coated and uncoated peanut oxidation at three accelerated shelf-life test temperatures and then use this information to model the shelf-life of the coated, control and reference peanuts at ambient conditions. Four different formulations of WPI-based coatings were used to coat the peanuts. Four controls were used to investigate the effects of other ingredients in the coating formulation. The peanut samples were stored in duplicate at 40, 50 and 60°C for up to 31 weeks and then analyzed using static-headspace gas-chromatography analysis of hexanal. Shelf-life at each higher temperature was determined by designating the initiation step of oxidation as the x-value of the intercept of the two linear curves that best fit the initial and later times in the hexanal level vs. storage time plot, respectively. Arrhenius model was used to fit the shelf-life for the three temperatures to predict the shelf-life at the ambient conditions. The results indicated that the coated samples were oxidized significantly slower than the reference; hence, the predicted shelf-life was longer for the coated samples. However, the investigation of the control ingredients revealed that even when only water was applied onto the peanuts the oxidation was delayed. The predicted shelf-life of this study will be compared with the actual shelf-life of the peanut samples stored in ambient conditions to test the validity of the model. The water treatment needs to be investigated further to clarify the mechanism of its inhibiting effect on oxidation in 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.