It is known that the oxidation products of oils display
characteristic spectra in the ultraviolet region. The
increase of the conjugated dienes values of the walnut oil
(absorbance, 232 nm) during the first days was
insignificant (Table 2). Extremely large increase of the
diene conjugation rate began during the eighth day, and
reached the level of 1.25. The vegetable oils with a
concentration of polyenic fatty acids above 30% (walnut
oil contains 61.1%) and the absorbance at 232 nm in the
rage of 1-1.25 were considered to be oxidative (Popov
and Yanishlieva, 1976). The proportional increase of the
conjugated dienes showed significant correlation with the
accumulation of hydroperoxides during the initial
oxidation period. Hydroperoxides were measured to
determine the initial rate of oxidation, because they are
accepted to be the first product formed by oxidation