91C-29 |
Effect of peanut moisture content on roast quality of microwave-blanched peanuts |
K. M. Lochman, Dept. of Food Science, North Carolina State University, Box 7624, Raleigh, NC 27695-7624, T. H. SANDERS, USDA/ARS, North Carolina State University, Box 7624, Raleigh, NC 27695-7624, and J. M. Drozd, Industrial Microwave Systems, Inc., 3000 Perimeter Park Dr., Bldg. I, Morrisville, NC 27560. Peanut blanching consists of heating to remove limited moisture followed by an abrasive process to remove seed coats. New microwave technology producing uniform energy has the potential to significantly reduce energy cost, decrease heating time, and improve moisture uniformity. The objective of this study was to examine the effect of initial moisture content on blanching efficiency, shelf- life and flavor quality of microwave heated peanuts. Shelled peanuts at moisture contents of 9.3%, 7.2%, 5.7%, and 4.7% were heated using unique microwave technology (7.65 kW for 5.77 min) as part of the blanching process. Exit temperatures were determined by infrared thermometry. Bulk and single seed moisture contents were determined before peanuts were roasted and stored at 31° C for 12 wk. Peroxide value, oxidative stability index, and descriptive sensory were determined weekly. Control samples for each moisture content were oven-heated (87° C for 1 hr) blanched and raw. Mean exit temperatures ranged from 104.3° C at moisture treatment 9.3%, to 118.57° C at moisture treatment 4.7%. All lipid quality analyses uniformly indicated that microwave-blanching, at each moisture content, reduced lipid oxidation compared to controls. Descriptive sensory analysis revealed that painty flavor intensity increased in all control samples from week 4 but intensity was less for microwave treated peanuts. A new off-flavor term, dark soured aromatic, evident in all microwave treated samples, was more intense in lower moisture (higher temperature) samples. Although microwave heating at this power setting resulted in high blanching efficiency and increased shelf-life, the resulting temperatures were probably too high to maintain peanut flavor quality. These data suggest that uniform energy microwave heating may be utilized to reduce moisture for high blanching efficiency, but microwave power and exposure time protocols must result in lower temperatures to maintain flavor quality.
Session 91C, Food Engineering: Food process engineering
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