Quality indices
The temperature effect of roasting promotes lipid oxidation, which in
turn influences the quality of a peanut oil (Al Juhaimi et al., 2018).
The result 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 at roasting
temperatures. 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
O2/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 O2/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 UFA/SFA 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).