The thermal oxidation evolution and relationship of unsaturated fatty acids and characteristic functional groups in blended oils with raspberry seed oil during deep-frying process by low field nuclear magnetic resonance and 1H nuclear magnetic resonance
2020
Han, Zongyuan | Yang, Xiaofei | Li, Xiaojing | Xiao, Zhigang | Wu, Zhaoxia | Shao, Jun-Hua
To demonstrate the oxidation evolution and thermal stability of blended oils during the deep-frying process, the relationship between unsaturated fatty acids, the distribution and migration of H protons and functional groups was investigated. The results showed that blended oils had high onset and peak oxidation temperature, and the peroxide value, p-anisidine value and polar compounds were low due to high tocopherols, which implied that blended oils had better thermal stability. The levels of linoleic and linolenic acids decreased significantly, as well as the ratio of C18:2/C16:0 except sunflower seed oil blended with raspberry seed oil. Moreover, there was also a significant decrease in relaxation times T₂₂ and T₂₃. The ratios of olefinic H, bisallylic CH₂, allylic CH₂ relative to glyceride CH₂ slowly decreased along with the increase of Rab and Rao, except corn oil blended with raspberry seed oil. For corn oil blended with raspberry seed oil, the ratio of olefinic H, bisallylic CH₂, allylic CH₂ increased and then slowly decreased. Rao, Rab and Raa reached the highest value on the forth day, then decreased, and Rab was higher than Rao and Raa. In addition, T₂₂,T₂₃ and functional groups significantly correlated with unsaturated fatty acids.
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