Changes in runner peanut quality parameters as a function of roast times

Authors: WEISSBURG, JACY - North Carolina State University; Dean, Lisa; Hendrix, Keith

Submitted to: Peanut Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/14/2024
Publication Date: 6/13/2024
Citation: Weissburg, J.R., Dean, L.L., Hendrix, K. 2024. Changes in runner peanut quality parameters as a function of roast times. Peanut Science. 51(1):45-58. https://doi.org/10.3146/0095-3679-51-PS23-8.
DOI: https://doi.org/10.3146/0095-3679-51-PS23-8

Interpretive Summary: Peanuts are roasted to enhance their flavor, digestibility and to make them microbiologically safe for human consumption. The characteristic roasted peanut flavor is a result of the formation of a large number of compounds, many of which are unidentified. Currently, peanuts are roasted to a specific exterior darkness which does not always created the best flavored products. This research examined the changes that occur in different components of peanuts over a wide range of roasting times. In addition, the flavor of the roasted peanuts was evaluated by a trained sensory panel that was highly experience in the evaluation of peanuts and related food products. The peanuts used were of the runner market type which is the most common type used to make peanut butter. It was found that the best flavor was developed in the peanuts that were considered slightly over roasted by industry standards because the exterior and the interior of the peanuts were at the same darkness and the moisture content had dropped to a constant level where the formation of rancid flavors was inhibited. This study will serve as guide for industrial roasters of runner-type peanuts trying to optimize roast peanut flavor in their products. The peanut roasting industry may find it beneficial to use other factors besides surface color to guide their roasting practices.

Technical Abstract: Physical and chemical changes in runner peanuts were evaluated after roasting for various times up to 24 minutes. The seed size, color, moisture content, total oil content, sugar content, free amino acid content and flavor attributes were determined on raw and roasted peanuts from each subsample. Moisture declined from 6.5% to 0.4% (DW) after 24-min. Drying curves were constructed and the critical moisture content (CMC=2.41% (DW)) was determined at 6-min. Roast peanutty rose rapidly between 6- and 12-min of roasting followed by a steep decline. Other sensory descriptors exhibited changes in their response curves at 6- and 12- min. Color analysis showed that kernels and pastes darkened (L values) during roasting and became redder (a value) and yellower (b value). Nearly all amino acids, sucrose and stachyose concentrations dropped rapidly after 6-min. Sensory, color, sugars, and amino acid data plotted against time and moisture content exhibited specific patterns with threshold points, maxima and inflection points occurring at the same times and moisture contents. The data were discussed in terms of developing a more mechanistic view of the roasting process. Proper roasting is required for everything from genotype evaluation to mass product production. A more complete understanding of the physical and chemical effects of roasting times can guide practices to better optimize peanut quality.