Peroxide Value. The method for determination of
peroxide concentration is based on the reduction
of the hydroperoxide group with HI or Fe2+. The
result of the iodometric titration is expressed as
the peroxide value. The Fe2+ method ismore suitable
for determining a low hydroperoxide concentration
since the amount of the resultant Fe3+,
in the form of the ferrithiocyanate (rhodanide)
complex, is determined photometrically with high
sensitivity (Fe-test in Table 14.27). The peroxide
concentration reveals the extent of oxidative
deterioration of the fat, nevertheless, no relationship
exists between the peroxide value and aroma
defects, e. g. rancidity (already existing or anticipated).
This is because hydroperoxide degradation
into odorants is influenced by so many factors
(cf. 3.7.2.1.9) which make its retention by fat
or oil or its further conversion into volatiles unpredictable.