Effect Of Enzyme-ultrasonic Combined Method On Proteolytic And Physicochemical Functions Of Pea

Pea protein has high nutritional value and hypoallergenic.It is considered as high quality plant protein.However,due to the fact that the amino acids that make up pea protein mainly exist in the form of protein polymerization,the low solubility of pea protein limits its application in the production process of China's food industry.In this paper,the pea protein was modified by the method of ultrasound-assisted composite protease.Three methods of enzyme,ultrasound-assisted enzyme and ultrasound-assisted enzyme were analyzed and compared to modify pea protein,and the hydrolysis process of composite enzyme was optimized.The influence of enzyme and ultrasound-assisted treatment on the structure and functional properties of pea protein was further discussed.Specific functional proteins,such as degree of hydrolysis,emulsification,foaming,oxidation resistance and gelation,were obtained respectively.The results of this study are as follows:I.Study on the modification of pea protein complex enzymeTo study the types of protease(including trypsin,neutral protease,papain,acid protease and alkaline protease),and to select the best protease.The results showed that trypsin had the highest degree of hydrolysis,followed by neutral protease,acid protease,papain,and alkaline protease,then combined enzymatic hydrolysis.It was found that the best ratio of trypsin and neutral compound protease was 3:1,the best hydrolysis effect and sensory evaluation.II.Study on the conditions of pea protein pretreatment by ultrasoundBased on the single factor experiments of ultrasonic time,ultrasonic power and p H,the response surface was optimized.The results showed that the optimal conditions of ultrasonic pretreatment were: ultrasonic time 21 min,ultrasonic power 361 W,ultrasonic p H 7.0.The hydrolysis degree of the hydrolysate was 33.8%.III.Study on the function and biological activity of pea protein modified by enzyme ultrasoundUnder the optimized ultrasonic pretreatment conditions,pea protein was hydrolyzed by enzyme,and the functional properties of pea protein under the highest degree of hydrolysis were obtained by response surface design.(1)The optimum conditions for the emulsification of pea protein modified by complex protease(trypsin: neutral protease = 3:1)were: adding 0.15% enzyme,hydrolysis time 31.0 min,p H 8.0,temperature 44.8 ?,substrate concentration 7%.Under the optimized conditions,the emulsification activity of pea protein modified was 29.48 m2 / g,and the emulsification stability was 37.65 min,31.20% and 28.31% higher than before.(2)The optimum conditions of foaming property of pea protein modified by compound protease(trypsin: neutral protease = 3:1)were: adding 50 U / g enzyme,hydrolysis time 42.5min,p H value 8.0,temperature 47.4 ?,substrate concentration 7%.Under the optimized conditions,pea protein foaming capacity(FA)317.69%,foam stability(FS)65.47%,71.18% and 306.56% higher than that before modification,respectively.(3)the hardness of protein gel increased first and then decreased with the addition of protease.When the composite protease dosage was 0.08%,the hardness of protein gel(the counterbalance of destructive force)was 515.88 g,and the hardness of protein gel began to decrease with the increase of enzyme dosage.When the enzyme dosage was 0-100 U/g,the elasticity of protein gel increased first and then decreased with the increase of enzyme dosage.When the enzyme dosage was 75 U / g,the maximum was 1.85 mm,and then began to decline.(4)It was found that the antioxidant activity of pea protein was significantly higher after hydrolysis than before.When the concentration of pea protein solution was 5%,the clearance rate reached 51.67%.With the increase of concentration,the clearance rate increased slowly.When the concentration of pea protein solution increased from 10% to 15%,the scavenging rate of hydroxyl radicals increased significantly.The reducing power also increased with the increase of the mass concentration of the hydrolysate.IV.Study on the relative molecular weight of pea protein modified by enzyme ultrasoundThe SDS-PAGE patterns of pea protein and pea protein hydrolysates with different enzyme addition were studied under the best condition of ultrasonic assisted enzymatic hydrolysis.The higher the amount of enzyme added,the smaller the molecular weight of the product.The addition of 75 u / g enzyme can hydrolyze pea protein into small molecular peptide < 14 kda.In this project,the functional characteristics of pea protein were modified by the method of combination of ultrasound and enzyme.The pea protein was modified by the evaluation indexes of emulsification and foaming.The special functional proteins with better hydrolysis,emulsification and foaming oxidation resistance were obtained,which can be used in food processing and provide a certain amount for the full and reasonable use of pea protein resources Theoretical basis.