Table 1 shows Infrared band assignments and modifications
observed throughout oxidation process.
When a compound in a mixture is at a very low concentration,
unless it has a very characteristic band of high absorptivity, it will
produce a very weak band in the IR spectrum and will be hardly
detectable. This phenomenon is observed in the band associated
with OH stretching vibration of the hydroperoxide group, located
around 3444 cm1
, which is not observable in non-oxidized oil
samples, but it can be seen as increases in intensity as oxidative
process progresses (Innawong et al., 2004). This band should not
be confused with the band present around 3470 cm1
, assigned
to an overtone of the glyceride ester carbonyl absorption (Guillén
and Cabo, 2002).