Changes in Runner Peanut Quality Parameters as a Function of Roast Times

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.