The DSC melting profiles of SFO and samples of SFO contaminated with BT, CF,
and LD are displayed in Figs. 1a–1c in the respective order. The curve A in Fig. 1a, representing
the uncontaminated sample of SFO, is found to display two distinct endothermic
transitions at −39.0 and −25.1◦C. The transition at −25.1◦C was associated with a smaller
shoulder peak appearing at −8◦C. It could be very clear that the temperature region from
−5.5 to 50◦C of the heating curve A is found to exist without any significant thermal
transitions. According to previous reports, the DSC melting cure of canola oil (CLO) was
also found to have a similar feature—the temperature region from −5.5 to 50◦C remained
without any thermal transitions. Non existence of a significant proportion of higher melting
TAG molecules in CLO was attributed as a probable reason for this phenomenon.[8]
Likewise, SFO is also ‘soft’ oil without much higher melting saturated TAG molecular
species. According to Table 1, it is largely composed of TAG molecules that are esterified
with oleic, linoleic, and linolenic acids. Once it was contaminated with different animal
fats, SFO experienced a significant change in its TAG composition as shown in Table 1.
As a consequence, the thermal behavior of the resulting oil mixture as monitored by DSC
would be different from that of the original sample. The way each animal fat influences
the melting curve of the original sample could differ based on the differences in their TAG
compositions. As it can be seen from Figs. 1a–1c, the changes caused by each animal fat
in the melting profile of SFO varied significantly. Among the thermal transitions of the
uncontaminated sample of SFO, the shoulder peak at −8.0◦C was found to be sensitive
to compositional changes caused by animal fats contamination. The addition of BT into
SFO has increased this peak only slightly (Fig. 1a) while the addition of both LD and CF
increased this peak more strongly (Figs. 1c and 1b).