91C-28 |
The effect of microwave energy level on roast quality of blanched peanuts |
T. A. KATZ, Dept. of Food Science, North Carolina State University, Box 7624, Raleigh, NC 27695-7624, T. H. Sanders, USDA/ARS, North Carolina State University, and J. M. Drozd, Industrial Microwave Systems, Inc., 3000 Perimeter Park Dr., Bldg. I, Morrisville, NC 27560. Seed coat removal, or blanching, consists of heating peanuts to remove a minimal amount of moisture followed by gentle abrasion. A novel microwave system, utilizing uniform energy, has the potential to significantly reduce energy costs while decreasing heating times. This study evaluated the effect of various power and time protocols, expressed as energy level, on blanching, flavor quality, and shelf-life of roasted peanuts. A unique microwave technology was used to provide heat necessary for blanching. Energy levels were varied by adjusting power and exposure time to create five treatments ranging from 803 KJ to 1627 KJ. Following the microwave treatment, peanuts were blanched and roasted at 350° F in a gas-fired pilot scale roaster. All treatments were stored in sealed glass containers at 30° C for 12 wk. The temperature of peanuts for the highest and lowest energy levels reached 110° C and 85° C, respectively. Blanching efficiency of 95% was achieved for the highest power while the lowest power resulted in 58% efficiency. The peroxide value (PV) for peanuts exposed to 1627 KJ increased from 1.28 meq/kg at roasting to 30.7 meq/kg at week 12 while the oven blanched control was 71.1 meq/kg at 12 wk. Oxidative Stability Indices (OSI) for the two highest energy treatments at week 12 were 6.62 and 6.00 hr, respectively. Comparatively, OSI for the control was 1.79 hr at week 12. Sensory analysis indicated that roast peanutty intensity steadily declined from ca. 5.0 to 4.0 for all samples. The lipid degradation related off-note, painty, was stable at <0.75 for all samples until week 4, but increased more rapidly for the control and lower power treatments. These results demonstrate that peanuts exposed to more microwave energy had increased blanching efficiency and longer shelf-life. Additionally, the results suggest flavor quality is not compromised by microwave heating.
Session 91C, Food Engineering: Food process engineering
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