Submitted to: Journal of Food Process Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/28/2007
Publication Date: 9/7/2007
Citation: Schirack, A.V., Sanders, T.H., Sandeep, K.P. 2007. Effect of processing parameters on the temperature and moisture content of microwave-blanched peanuts. Journal of Food Process Engineering 30(2)225-240. Interpretive Summary: The results of this study will enable peanut processors to assess the feasibility of using a microwave unit to blanch their peanuts. Previous studies indicated that microwave blanched peanuts could possibly have off-flavors. This study provides guidelines on the appropriate process parameters that will ensure rapid blanching and adequate quality (absence of off-flavors) of the peanuts. Thus, microwave energy can be used to decrease the total time of processing, thereby increasing throughtput. It also paves the way for the possibility of using microwaves for roasting of peanuts.
Technical Abstract: Peanut blanching consists of heat application followed by abrasive removal of the seed coat. The use of a continuous microwave system for the blanching of peanuts has been proposed as a means of reducing processing time and energy costs compared to the traditional hot-air, multizone oven. The purpose of this research was to characterize effective processing parameters for microwave blanching. The factors examined were the time of exposure in the microwave, use of increased airflow in the microwave applicator during processing and the initial moisture content (MC) of the peanuts. Processing treatments were differentiated by energy absorbed during processing, average and maximum internal temperature, loss in MC and blanchability. High blanchability resulted from higher process temperatures and greater loss in MC. Treatments exceeding 110C resulting in a final MC of 5.5% or below yielded blanchability percentages greater than the 85% industry standard. The time required to generate sufficient heat to dry peanuts for acceptable blanchability is greatly reduced by the use of microwave technology.