Food Lipids: Chemistry, Nutrition, and Biotechnology

Figure 10 1 H Nuclear magnetic resonance spectrum of oxidized canola oil (peak at � 0.00
and 7.26 are for tetramethylsilane (TMS) and CHCl 3 protons as impurities in CDCl 3,
respectively).
d, hydrogens in the three CH 2 groups alpha to the carboxyl groups (�-CH 2; � 2.2–
2.4); e, hydrogens in the CH 2 groups attached to saturated carbons and doublebonded
carbon atoms (—CH 2 —C—; � 1.8–2.2); f; hydrogens in the CH 2 groups
attached to the saturated carbon atoms (—C—CH 2—CH2; � 1.45–1.8); g, hydrogens
in the CH 2 groups bonded to two saturated carbon atoms ([CH 2] n; � 1.1–1.45); and
h, hydrogens in the three terminal CH 3 groups (� 0.7–1.0). The relative number of
protons in each group is calculated based on the integration of methylene protons of
the glyceryl moiety (� 4.0–4.4) of the TAG (four protons in the two methylene
groups of the TAG moiety) molecules. The area per proton is obtained as:
Area per each proton = area of b-type protons/4
Since area per proton is known, one may calculate the number of protons belonging
to each and every individual signal by dividing the integration number of individual
signals by the area per proton. As an example, the total number of diallylmethylene
protons equals the area of c-type protons/(the area of b-type protons/4).
The total number of aliphatic, olefinic, and diallylmethylene protons are calculated,
from which ratios of aliphatic to olefinic protons (R ao) and aliphatic to diallylmethylene
(R ad) protons may be obtained. These ratios increase steadily during the
storage and oxidation of oils. Shahidi [79] and Wanasundara and Shahidi [80] have
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