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Process Parameter Effects on Pan-Coating of Peanuts With Whey Protein Film

By,
 S.C. Schlake and J.M. Krochta
Department of Food Science and Technology
University of California, Davis

2004 IFT Poster Presentation

Peanuts are high in polyunsaturated fats, which make them susceptible to oxidative rancidity. Studies with whey protein films have determined that they are excellent oxygen barriers. Forming whey protein films as coatings on peanuts could reduce oxygen uptake and, thus, preserve peanut quality.

The objective of this study was to investigate the effects of coating-process parameters on whey-protein film-coating continuity and uniformity. These parameters included temperature, relative humidity, air velocity, pan rotation rate, rate of coating-solution addition, amount of solution added, pan scraping rate, and means of solution application (ladling vs. spraying).

Batches of peanuts were coated with a whey protein solution containing a food grade blue dye. Coating of each set of batches was done at various combinations of room temperature from 17-26C and relative humidity from 27-44%. After drying coated peanuts to a water activity of 0.2, the peanuts in each batch were sampled and photographed. The peanut images were analyzed with a program that quantifies the blue regions of the peanut, providing a value for percent coated.

Coating-coverage data shows that the combination of temperature between 17-20C with an average relative humidity between 33-38% gave the highest coating coverage (80-82%). For the rate of coating-solution addition used, the drying rate for other combinations of temperature and relative humidity appears to be too fast to yield an efficient coating. Further investigation of coating-process parameters, including increasing the rate of coating solution addition, is aimed at improving coverage to 100%.

In coating situations in industry in which one or more process parameters is fixed or is likely to vary, having multiple combinations of optimized coating parameters will allow for reproducible continuous and uniform coatings.

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.

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