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

methylpropanoate, ethyl 2-methylbutanoate and ethyl 3-methylbutanoate as well as
increased levels of short chain organic acids such as butanoic acid, hexanoic acid,
and 3-methylbutanoic acid were found in immature peanuts cured at high
temperatures, which had the fruity fermented off-flavor. By adding these compounds
back to a model system, the short chain organic acids were shown to be responsible
for the cheesy fermented aroma, while the esters added fruity, apple-like aromas.
Subsequent processing, such as roasting, increased the levels of short chain
organic acids by 10- to 40-fold in fruity fermented peanuts (Didzbalis et al., 2004).
In addition to the off-flavor, fruity fermented peanuts have been associated
with lower levels of the desirable roasted peanutty flavor and sweet aromatic notes.
Pattee et al. (1989) first noted the impact of the fruity character in suppressing
roasted peanut flavor. An inverse linear relationship was found between roasted
peanut flavor and fruity off-flavor in roasted peanut paste, with a 1:2 decrease /
increase ratio, respectively. The fruity off-flavor in peanuts may suppress roasted
peanut flavor perception, or production of the roasted peanut attribute may be
reduced due to high-temperature curing (Pattee et al., 1990).
Immature peanuts may be more susceptible to fruity fermented off-flavor
formation due to the incomplete biosynthesis of primary metabolites. Furthermore,
these metabolites will mix and react during cell damage caused by temperature
stress (Didzbalis et al., 2004). Threonine, tyrosine, and lysine have been found in
high concentrations in immature peanuts with high levels of off-flavors, and as a
result were associated with the production of atypical flavors (Newell et al., 1967).
Didzbalis et al. (2004) found that while immature peanuts cured at high temperatures
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