Changes of Fat and Fatty Acid Metabolism in Post-fermentation Process of Pixian Soybean Paste

Gas chromatography(GC)internal standard method was used to qualitatively and quantitatively analyze the fatty acids of Pixian soybean paste with eight different post-fermentation stages,which was extracted with petroleum ether and methylated with sulfuric acid-methanol. The results showed that the crude fat contents was 3.46%~4.29%,and the total fatty acid contents was 8.258~18.484 mg/g. There were nine fatty acids detected at different post-fermentation stages,which were linoleic acid(4.963~11.668 mg/g),oleic acid(1.186~2.706 mg/g),palmitic acid(0.751~1.649 mg/g),linoleic acid(0.405~0.886 mg/g),stearic acid(0.296~0.856 mg/g),myristic acid(0.131~0.305 mg/g),transoleic acid(0.126~0.230 mg/g),palmitoleic acid(0.056~0.142 mg/g)and lauric acid(0.030~0.113 mg/g). The results of principal component analysis showed that the contribution rates of the first and second principal components were 75.09% and 15.21% respectively,and the cumulative contribution rate was 90.30%,which could be better reflect the basic information of all fatty acid compositions. Moreover,the fatty acid changes in the post-fermentation period could be roughly divided into three stages(post-fermentation early stage,post-fermentation middle stage and post-fermentation late stage),and the changes of fatty acids in the early stage were far greater than those in the middle and late fermentation stage. The results of the study could provide a scientific basis for Pixian soybean paste industrialized production control product quality and establishment of production quality control system.