Study On Lipolysis Change On Sufu During The Fermentation Process

Actinomucor elegans (AS) is the representative microbial stains of sufu fermentation. This study focuses on the fermentation process of sufu. AS 3.27 is applied to fermentate sufu and white-sufus are made in laboratory by ourselves. AS 3.27 lipase characteristics were studied by using tritrimetric and pNP methods in order to analyze lipase optimum conditions. We analyzed the chemical changes including fat content,lipase activity and free fatty acids of sufu during the fermentation process, which was to study the relationship of the formation of sufu flavor.. Thus, we can improve the quality and flavor of sufu, provide some theoretic basis for sufu research and promote the development of sufu industry.The conclusions are as follows:(1)Different results are showed by using different substrates to study the characteristics of AS lipase. AS lipase optimum pH,temperature and NaCl concentration is 7.0,40℃and 0.15mol/L, respectively by using PVA-olive oil as substrate. However, when the substrate is pNPC, the optimum pH of lipase is 7.5, temperature is 30℃and NaCl concentration is 0.2mol/L. Applying pNPP as substrate, the optimum pH of lipase is 7.0, temperature is 35℃and NaCl concentration is 0.2mol/L the same as pNPC. But the lipase activity is more stable under alkaline condition and high temperature.(2)Lipase activity of fresh pethze shows the maximum value 0.55U/mL, during the cultivation strains process. With the development of mature process, the lipase activity decreases gradually. But during the period of 20-25 days of mature process, lipase activity increases by a small margin. Using two methods for determination lipase activity (titrimetric and pNP methods), the same trend is displayed.(3)During the fermentation process of sufu, the fat content,pH and moisture decrease gradually while the acid degree value increases.(4)Free fatty acids of the sufu ripening process are determined. Using four kinds of ion exchange resins including D201,D261,D290 and D296 to extract free fatty acids, the results show the same trend the content of free fatty acids(mg/g) increase gradually. The concentration of free fatty acids ranges from large to small is linolenic acid(1103mg/g),oleic acid(680mg/g),palmitic acid (300mg/g),linolenic acid(150mg/g) and stearic acid (120mg/g).(5)Because of the different absorption rate of ion exchange resins, the results show different. The ion-exchange rate of ion exchange resins is D201> D261>D296>.D290.(6)The sensory evaluation of sufu self-made is investigated. The main aroma,color,flavor and texture of sufu are developed during the period of 5-20ds in ripening process. After 30ds, sufu basic is mature. However, the shape of sufu is formed at the beginning of mature process, there is no significant changes thereafter.