关键词: 12-羟基硬脂酸；凝胶化油脂；热氧化；官能团；凝胶结构；核磁共振氢谱法

Abstract: The effect of 12-hydroxystearic acid (12-HSA) as an organogelator on oxidation indices of soybean oil organogels prepared with it was investigated together with the role of the functional groups of 12-HSA in promoting lipid oxidation. Further, the mechanism of the effect of the thermal processing of 12-HSA on the oxidation of soybean oil organogels was studied based on the difference between the state of organogels at room temperature and that during thermal processing, and the thermal oxidation of organogels was analyzed by 1H-nuclear magnetic resonance (1H-NMR). The results showed that 12-HSA reacted with the titrating alkaline solution, increasing the measured acid value. The true acid value reflected by free fatty acids in the oil should be calculated by subtracting the measured acid value with the acid value caused by 12-HSA. 12-HSA had a promoting effect on the oxidation. Under the same condition, the headspace oxygen consumption was in the descending order of stearic acid > stearyl alcohol > 12-HSA > octadecane, implying that the oxidation-promoting effect of hydroxyl and carboxyl group alone was stronger than that of 12-HSA containing both groups. The rheological results showed that at 25 ℃, 12-HSA with 2% addition enabled soybean oil to form a stable gel structure and to be less susceptible to oxidation. When the temperature was greater than 60 ℃, the gel structure was gradually destroyed, and the oxidation-promoting effect of 12-HSA was gradually enhanced. Compared with the blank control group, the headspace oxygen consumption in the 12-HSA group at 90 and 120 ℃ increased by 0.65% and 1.78%, respectively. The results of 1H-NMR showed that the integral peak area ratio of protons between aliphatics and olefins (Rao) and that between aliphatics and diallylmethylenes (Rad) increased with the degree of oxidation, both having a good positive correlation with the total oxidation value of oleogels.

Key words: 12-hydroxystearic acid; oleogels; thermal oxidation; functional group; gel structure; 1H-nuclear magnetic resonance