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Research Project: Improvement and Maintenance of Flavor, Shelf Life, Functional Characteristics, and Biochemical/Bioactive Components in Peanuts, Peanut Products and Related Commodities through Improved Handling, ...

Location: Food Science and Market Quality and Handling Research Unit

Title: Effect of kernel characteristics on color and flavor development during peanut roasting: two years of data

item Hendrix, Keith
item Dean, Lisa
item Toomer, Ondulla

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/31/2017
Publication Date: 7/12/2017
Citation: Hendrix, K., Dean, L.L., Toomer, O.T. 2017. Effect of kernel characteristics on color and flavor development during peanut roasting: two years of data. Meeting Abstract. Vol. 49.

Interpretive Summary: Peanuts are harvested, often at varying maturities due to the indeterminate nature of peanut plant flowering. Maturity affects the chemical composition of peanuts and thus, the roastability. Once transported to roasting plants, the peanuts may also be of varying cultivars. Traditionally, peanuts are roasted to a selected color as this is the most consistent way to measure consistency of roast on a large scale. This research investigated a range of factors, including final roast color, final moisture levels and flavor characteristics to determine when different flavor notes are optimized. This research will enable peanut processors to make decisions about roasting using other factors besides final roast color to optimize peanut flavor.

Technical Abstract: Experiments with Crop Year (CY) 2014 samples from the Uniform Peanut Performance Trials (UPPT) revealed that color and flavor profile development were related to kernel moisture content (MC) during dry roasting. That work was repeated with CY 2015 UPPT samples with additional replication. Raw MC, raw oil content, raw kernel color (un-blanched), roast MC%, roast kernel color (blanched) and roast paste color were measured. As for 2015, the 2016 data contained a specific pattern of changes in the flavor descriptors which were invariant with regard to genotype or planting location. The pattern had several parts. Roast peanutty (RP), sweet aromatic (SA) and dark roast (DR) rose above detection threshold together. RP and SA peaked 1 to 4 minutes later. RP and SA then slowly dropped back toward threshold detection levels. DR entered a distinctly different phase in which its rate of upward change was cut in half. This always occurred at the same time RP and SA began dropping. Ashy, an acrid flavor found usually in darker samples, rose above threshold at exactly the same point that DR changed phase. These threshold points and other changes during roasting were highly correlated with MC level in the roasting kernel and not directly proportional to roasting time. For example, roast peanutty was never detectable (crossed threshold) until MC had dropped to between 2.2 and 2.5%ww. Likewise, the eventual drop in RP values at longer roast times began only when MC dropped between 1.2 and 1.5%ww. In contrast, the times at which the appropriate MC levels were reached varied greatly and depended on seed size and oil content. The overall pattern of flavor changes occurred faster as seed size (weight) dropped and/or the oil content rose. This would indicate the crucial importance of MC during flavor development. Although raw moisture content undoubtedly affects roasting, the range of starting raw MC of the samples in this study was small and statistics suggested only a slight effect. Raw peanut skin color had no effect on flavor or color development in the kernel.