Submitted to: American Peanut Research and Education Society Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 7/19/2002
Publication Date: 7/20/2002
Citation: Sanders, T.H., Hendrix, K., Rausch, T.D., Katz, T.A., Drozd, J.M. 2002. Effect of microwave energy on blanchability, shelf-life and roast quality of peanuts. American Peanut Research and Education Society Proceedings 34:112.
Technical Abstract: Novel microwave technology that creates a uniform distribution of microwave energy was utilized to examine the effect of microwave energy on blanchability and quality of peanuts. Preliminary studies indicated that the time for reduction of peanut moisture content by approximately 2 percentage points was less than 6 min utilizing microwave energy compared to 60 min for conventional blanching technology with heated air. Raw, runner-type peanuts were subjected to a total of 9 treatment combinations of 5, 7.5, or 10 kW of microwave power for 1.47, 2.85, 4.2 or 5.78 min duration. After treatment, samples were examined for total moisture content, single seed moisture distribution, and blanchability before being stored at 30 C for 28 wk. Peroxide value, oxidative stability index, hexanal, and pentanal were determined as measures of shelf-life of the treated samples. Samples with the highest moisture after blanching had the longest shelf life. From these data five treatment protocols were selected for use in additional blanching tests with subsequent roasting and storage of samples. Following the five microwave treatments, peanuts were blanched and roasted at 350 F in a gas-fired pilot scale roaster then stored in sealed glass containers at 30 C for 12 wk. Blanching efficiency of 95% was achieved for the highest energy input while the lowest energy input resulted in 58% efficiency. Samples with the highest moisture content before roasting had the shortest shelf-life during storage. 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, then increased more rapidly for the control and lower power treatments. These data suggest strong potential for advancements in peanut moisture removal technology using this novel microwave technology.