The Study Of Manufacture Of Sufu By Enzymatic Accelerated Maturation And Its Quality

Sufu, a kind of Chinese traditional fermented soybean food, is rich of nutrition. It has some disadvantages in competition at modern market due to its traditional processing methods. The paper was aimed to improve the traditional sufu production and develop a new kind of sufu by adding enzymes. The process of enzyme modify sufu(EMS), the changes of chemicophysical properties and the volatile compounds contributed to the flavor were investigated. The physical and chemical properties and mode identification of enzyme modify sufu were studied, which could provide theory to producing sufu.Research of manufacture of EMS showed that using soybean milk as raw materials and adding the lactobacilli R704to produce soybean curd not only mixed enzymes with soybean milk fully, but also assured the shape of soybean curd after pressing.Through experiment design from response surface methodology (RSM), the hydrolysis conditions were optimized as following:enzyme I and II enzymes were combined at the ratio of2:1and added into the substrate of soya milk of8.0%at the amount of15g/100L; the enzymolysis took place at50℃and pH6.9for6.4hours, then inactivated at75℃for20min to denature the enzyme activity.Results of changes by proteolysis of sufu showed that the contents of total acid, amino nitrogen and total water soluble protein reaching higher, and the contents of amino nitrogen and that of total water soluble protein were high significant positive correlation. The DPPH radical-scavenging of sufu was reaching higher and then lower. The highest activity was reached at92.3%when at5.Oh. The microstructure of EMS after30days post-fermentation was similar to the traditional sufu after6months ripening. The chromatogram characteristic of EMS and the traditional sufu was coincident evaluated by normalized mid-infrared spectra.Results of changes by volatile compounds showed that the volatile compounds of EMS had5.13%hydrocarbon,7.69%alcohols,5.13%aldehydes,10.26%acids,51.28%esters and20.51%other compounds.Results of physical and chemical properties and mode identification of sufu suggested that the five physical and chemical index could be replaced by two principal components. Total acid, amino nitrogen and the DPPH radical-scavenging were related to proteolysis and they had a high relative coefficiency. There was a close relationship between moisture content and DH. According to principal component analysis, total acid, DH and the DPPH radical-scavenging were predominate in most EMS, which conformed to the results of chemicophysical properties and sensory evaluation.