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

and quantity of volatiles formed in heat-treated lipids are governed by the type of
hydroperoxide precursors in the sample (Ulberth and Roubicek, 1993). Volatiles
such as ethanol, pentane, and pentanal have also have been associated with lipid
oxidation (Brown et al., 1977). Furthermore, lipid oxidation products can be linked
through glycosidic linkages or hemiacetal and ketal links to polysaccharides, which
are then released during the roasting process (Vercellotti et al., 1994).
Lipid oxidation can also be identified in a chromatogram by a general rise in
the base line volatiles beyond hexanal, due to the appearance of oxidation by-
products such as aldehydes, ketones, and hydrocarbons. Most of the compounds
with retention times less than hexanal are lost during the roasting process (Ory et
al., 1992). Volatile profiles of roasted peanuts both with and without lipid oxidation
were analyzed using direct GC and an external closed inlet device and
“aromagrams” for different quality peanuts were generated (Vercellotti et al., 1992).
Vercellotti et al. (1992) also published profiles matching flavor peaks identified with
GC-O to retention time, enumerating lipid degradation compounds found in the
rancid peanuts.
Although the flavor and aroma of high quality roasted peanuts is in part due to
oxidized compounds generated during storage (Ahmed and Young, 1982), these
compounds can also have a negative impact at higher concentrations. Oxidation
reactions can result in decrease of desirable peanut flavor by loss of low molecular
weight flavor compounds and generation of undesirable volatile carbonyls such as
nonanal, decadienals, or heptadienals (Sanders et al., 1993). Vercellotti et al.
(1992) found that during lipid oxidation, off-flavor producing volatiles such as
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