Characterization of peanuts after dry roasting, oil roasting, and blister frying

Authors: SHI, XIAOLEI - North Carolina State University; Davis, Jack; XIA, ZHOUTONG - North Carolina State University; SANDEEP, K - North Carolina State University; Sanders, Timothy; Dean, Lisa

Submitted to: LWT - Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2016
Publication Date: 10/27/2016
Citation: Shi, X., Davis, J.P., Xia, Z., Sandeep, K.P., Sanders, T.H., Dean, L.L. 2016. Characterization of peanuts after dry roasting, oil roasting, and blister frying. LWT - Food Science and Technology. 75:520-528.

Interpretive Summary: Peanuts must be cooked in some way before they are consumed. The three most common preparation techniques are dry or oven roasting, deep frying or oil roasting, and blister frying which is oil roasting after the raw peanuts have been soaked in water. Each process results in a unique final product. This research evaluated the final products after cooking for their color, texture, microstructure and flavor. The change in flavor due to onset of staleness was also evaluated to determine which process results in peanuts staying fresh longer. It was found that oil roasted peanuts retained fresh flavor longer than dry roasted ones. This was attributed to the different changes in water content with cooking.

Technical Abstract: Peanuts were systematically deep fried, blister fried, or dry roasted at 177°C to Hunter L-values of 53 ± 1, 48.5 ± 1, and 43 ± 1, corresponding to light, medium, and dark roasting, respectively. Thermal modifications of the epidermal and parenchyma cells were observed in the scanning electron microscopic images for processed peanuts, compared to raw peanuts. Peanut microstructure was most extensively damaged by blister frying, followed by deep frying, and then dry roasting. The moisture content decreased with increased surface color, due to more moisture loss with longer heat processing time. For light roasting, blister fried peanuts had significantly higher moisture contents than the deep fried and dry roasted peanuts, while for medium and dark roasting, blister fried had lower moistures than the other two. Descriptive sensory analysis was able to distinguish the flavor and texture profiles of peanuts prepared by different roasting methods. In storage testing throughout 16 weeks, peroxide value measurements indicated the blister fried peanuts had the longest shelf life, followed by the dry roasted, and then the deep fried. Descriptive sensory analysis proved that the rate of the loss of roast peanut flavor during storage was faster in dry roasted peanuts followed by blister fried and deep fried.