'Flavor-fade' and off-flavors in ground roasted peanuts as related to selected pyrazines and aldehydes

Headspace volatiles from ground roasted Florunner medium peanuts, stored at 65°C for 1-68 days, were separated and identified by GC/MS. Selected pyrazines, resulting from Maillard browning and selected aldehydes from autoxidation were evaluated to determine their mechanistic contributions to peanut 'flavor-fade.' The 2,6-dimethylpyrazine, 2-methylpyrazine, 2-ethyl-5-methyl or 6-methylpyrazine, 2,3,5-trimethylpyrazine, and pentanal remained constant during storage (p < 0.05). Flavor scores for 'roasted peanut' decreased slightly, then leveled off and hexanal, heptanal, octanal and nonanal increased during storage (p < 0.05). Oxidative 'rancid' flavor scores and thiobarbituric acid values also increased during storage (p < 0.05). Based on results, the 'flavor-fade' of stored roasted peanuts is due to masking of pyrazines and other 'roasted peanut' flavor compounds by large quantities of low-molecular weight aldehydes from lipid autoxidation, and not due to polymerization and/or degradation of the pyrazines.