小麦胚芽贮藏期内脂质水解酸败机理解析

Mechanism of lipid hydrolytic rancidity in wheat germ during storage

以小麦胚芽为研究对象,构建脂质水解酸败的模拟体系以及原位体系,解析小麦胚芽贮藏期内脂质水解酸败的机理。结果表明:光照、氧气和脂肪氧合酶未对小麦胚芽模拟体系中的游离脂肪酸含量产生明显影响,而脂肪酶则显著提升游离脂肪酸生成量;此外,游离脂肪酸生成量随水分活度增加而增加,于水分活度为0.75时达峰值,且小麦胚芽内部结合水和不易流动水含量也呈显著增加趋势,水分以及脂质流动性增加;小麦胚芽原位体系中游离脂肪酸含量随贮藏时间延长而逐渐增加,磷脂酰胆碱含量恰相反,且小麦胚芽脂质体膜遭到破坏,游离出的甘油三酯聚集形成油滴。由此可见,小麦胚芽脂质水解酸败模式主要表现为其脂质体膜中的磷脂酰胆碱降解而释放甘油三酯,而后甘油三酯经由脂肪酶催化水解生成大量的游离脂肪酸,从而产生水解酸败现象。

Wheat germ was adopted to establish the model and in-situ systems for exploring the mechanism of lipid hydrolytic rancidity during storage. The results showed that light,oxygen and lipoxygenase had slight influences on the contents of free fatty acids in the model system,while lipase could significantly promote the formation of free fatty acids. In addition,the formation of free fatty acids increased with the increase of water activity,reaching a peak at water activity of 0. 75,and the contents of bound water and non-flowing water inside the wheat germ also showed significant increase trend,and fluidity of water and lipid increased. Besides,the content of free fatty acids in the in-situ system gradually elevated with storage time prolonging, while the phosphatidylcholine content decreased gradually. The lipid body membrane of wheat germ was also destroyed,accompanying with the release of triglycerides and their aggregation into oil droplets. Therefore,the wheat germ lipid hydrolytic rancidity model was mainly manifested in that the phosphatidylcholine in lipid body membrane was degraded to release triglycerides,following by the hydrolysis of triglycerides catalyzed by lipase to produce large amount of free fatty acids,thereby leading to the hydrolytic rancidity.