Abstract SCHIRACK, ANDRIANA VAIS. The Effect of Microwave ...

Precursors to Roasted Notes
Initial attempts to identify precursors of roasted peanut flavor led to the
conclusion that roasted flavor arose from low molecular weight compounds such as
aleurone grains and protein bodies in the peanut (Mason and Waller, 1964).
Flavor precursors were believed to form flavors through intracompartmental
pyrrolysis and degradation of the precursors at temperatures exceeding 132 °C
(Mason and Waller, 1964). Then Mason et al. (1969) found that raw defatted
peanuts would develop typical roasted peanut aroma, no matter if heated in peanut
oil or oil from another source. Flavor development has been shown to be sensitive to
peanut maturity, and Mason et al. (1969) correlated the concentration increase of a
specific peptide to increase in maturity, suggesting that this peptide is a
characteristic precursor of typical roasted peanut flavor. Newell et al. (1967) also
postulated a mechanism for the conversion of amino acids and sugars into volatile
flavor compounds, with the ultimate product of 2,5-dimethylpyrazine. The same
group found that aspartic acid, glutamic acid, glutamine, asparagine, histidine, and
phenylalanine were associated with the production of typical peanut flavor. These
amino acid concentrations initially represent a majority of free amino acids present,
and decrease as they are degraded during roasting (Newell et al., 1967).
Moisture content also plays a part in flavor development. During roasting,
hydrolysis can occur in higher moisture peanuts, increasing the amounts of free
amino acids and monosaccharides, and as a result, the original content of flavor
precursors in raw peanuts may not be a final indicator of flavor quality (Chiou et al.,
1991). In fact, Chiou et al. (1991) found that the amino acid content of peanuts
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