Quality indices
The high temperature used in roasting can promote lipid oxidation, which
in turn influences the quality of a peanut oil (Al Juhaimiet al., 2018).
The results show that the BIs of the peanut oils generated by different
roasting temperatures in this study ranged from
37.94~195.71(Table 1). Simultaneously, the color of
peanut oil changes from a dark yellow to red brown as roasting
temperature increased. Furthermore, the AVs of the peanut oils generated
by different roasting temperatures ranged from
1.12~1.94mg KOH/g, while the POVs of the peanut oils
generated by different roasting temperatures ranged from
5.48~8.67 meq peroxide/kg. These values meet the Chinese
National Standard criteria for peanut oil. AV and POV determinations are
often used as general indications of the condition and edibility of
oils. When an oil has a POV>10 meq peroxide/kg, it is less
stable and to have a short shelf life (Madhujith and Sivakanthan, 2018).
Relatedly, oxidation products can cause undesirable health problems. The
result show that the p–AVs of the peanut oils were generated by
different roasting temperatures in this study ranged from
5.47~10.42 meq/kg. We further found that the TOTOX
values of the peanut oils generated by roasting at 120℃, 140℃, and 160℃
were 16.43, 26.70, and 27.76, respectively. The quality standards of the
European Pharmacopoeia require specific levels of TOTOX ≦30(Xu et al.,
2015).
Various fatty acids influence the nature of an oil’s physicochemical and
nutritional performance. Regarding the fatty acid compositions of the
peanut oils generated after roasting in this study, we found out 8 kinds
fatty acids. The obtained data further showed that no significant
differences in fatty acid composition for the oils generated by
different roasting temperatures (Table 2, p<0.05). Oleic acid
(36.67~38.44%) is an important nutritional component of
peanut oil. Compared with PUFA, oleic acid is more resistant to thermal
oxidation, both at ambient storage temperatures and the high
temperatures that prevail during cooking and frying of food (Penget al.,
2017). Relatedly, vegetable oils with higher U/S ratios are more
precious in terms of nutritional quality, as they may contribute to a
greater extent to lowering the LDL cholesterol and total cholesterol of
people, while not affecting their levels of beneficial HDL cholesterol
(Hashempour–Baltork et al., 2016; Cicero et al., 2018). We found that
the UFA/SFA values of the peanut oils generated by roasting in this
study ranged from 3.58~3.68. Other studies have
indicated that the U/S values of camellia seed oils ranged from
3.23~3.31(Yang et al., 2018).