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

content has a significant effect. In a study by Singleton and Pattee (1991), as the
moisture level of peanuts exposed to freezing temperatures was increased from 6 to
40%, acetaldehyde and ethanol increased in concentration, to up to 27 times the
control concentration. The high moisture peanuts were more susceptible not only to
freeze damage, but also to heat stress, and also had increased rates of hydrolytic
reactions. Even peanuts at 25% moisture were more susceptible to freeze damage,
and subsequent elevated drying temperatures accentuated the damage (Singleton
and Pattee, 1991). In a study by Osborn et al. (1996), seed moisture content as well
as peanut maturity appeared to influence production rates of acetaldehyde, ethanol,
and ethyl acetate, although ethyl acetate production rate appeared to be proportional
to amounts of ethanol produced.
Time and temperature protocols during processing also have an effect.
During drying of peanuts, formation of acetaldehyde, ethanol, and ethyl acetate did
not begin right away. Instead, volatiles increased after 5-15 hours of processing,
while ethanol concentrations began to decrease after 30-40 hours (Osborn et al.,
1996). Procedures for detection of high temperature off-flavors must take into
account that volatiles diffuse from peanuts during drying. The concentrations of
these volatiles after processing depends on the rate of both formation and diffusion
rates of each volatile, which are affected by seed temperature during drying. Seed
temperature has been related to amount of off-flavor produced in the peanuts as
well. Likewise, the ratio of acetaldehyde to ethanol to ethyl acetate during the drying
process was also related to drying air temperature (Osborn et al., 1996).
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