Effects Of Enzymatic Hydrolysis On The Functional Properties And Quality Of Skim Milk

Currently reports on milk enzyme modified mainly by purification of whey protein or casein base makings,studying the characteristics of the enzyme solution,including antigenicity,molecular structure,such as physical and chemical properties,with milk system for the study is less,and milk as a kind of complex system,the molecular structure of enzyme treatment in addition to cause antigenicity,such as the physical and chemical properties change,also causes changes in the interaction between the components,thus affect its sensory,physical properties and nutritional quality,at the same time give it new features,these qualities and characteristics of the scope of application of development and change of milk product research and development is particularly important.Therefore,the experiment took skim milk as the raw material,among which degreasing treatment was beneficial to enzymolysis,alkaline protease,complex protease and flavor protease were selected for enzymolysis treatment,and the emulsification,foaming and solubility of the product of skimmed milk were measured to study its functional characteristics.The physical and chemical quality was studied by rheometer.The sensory quality was analyzed by electronic tongue.Full spectrum free amino acids were analyzed by HPLC-MS/MS technology,and then their nutritional quality was evaluated.The results are as follows:(1)Enzymolysis treatment had no obvious effect on dry matter content of skim milk;The solubility of the three protease treatment groups increased significantly,and the treatment group had better solubility in a wide p H range,among which the flavor-protease treatment group had the highest solubility.Alkaline treatment group and complex protease foamability,emulsification and DPPH · removal ability were higher than skim milk,however,foam and emulsion stability of enzyme treatment group were significantly lower,and in the process of the enzyme were presented significant decline,and DPPH · clearance all showed a trend of decline after rising first,DPPH · clearance minimum flavor protease treatment group.(2)Compared with skim milk,the dispersion index of enzymolysis treatment group was significantly increased,and the particle size distribution range was increased.The centrifugation precipitation rate was significantly increased in both alkaline and complex protease treatment groups.In the protease treatment group,the apparent viscosity increasedand the required shear stress also increased during the process of enzymatic hydrolysis for15-60 min.However,the change trend of flow curve in the enzymatic hydrolysis treatment group was basically consistent with that in the control group.(3)Compared with defatted milk,L* value in enzymatic hydrolysis group decreased significantly,while a*(negative value)increased significantly.The color of defatted milk changed greatly after being treated with flavor protease.At the same time,the sweetness value of the enzymatic hydrolysis products decreased significantly.The taste aftertaste of the alkaline protease treatment group was mainly astringent and astringent,the taste aftertaste of the flavor protease treatment group was mainly salty,bitter and bitter,and the taste taste of the compound protease treatment group was mainly sour,and the taste taste was relatively low,and the proportion of bitter amino acid in the degreased milk would increase after enzymatic hydrolysis.More volatile flavoring substances such as acetone,caprylic acid,decanoic acid,octanol and nonaldehyde were detected in defatted milk,which formed the overall flavor characteristics of the products after enzymatic hydrolysis.Detection of the communist party of China(4)in the control group and treatment group45 kinds of full spectrum of free amino acids,and the treatment group were significantly increased the total free amino acid content,skim milk and alkaline protease treatment group of china-africa essential amino acids as the main component,the flavor protease treatment group of essential amino acids as the main component,compound protease treatment group of proteins encoded amino acid as main components;The score of free amino acid of enzymatic hydrolysis products was higher than that of control group,and the score of free amino acid of savoury protease treatment group was the highest.