Study On The High-efficiency Preparation And Functional Properties Of Papeseed Protein Hydrolyaste Formed By Microwave-assisted Technique

Rapeseed protein is one of the plant protein resources. But because of the existence of toxic substances and anti-nutritional factors in rapeseed meal, the application of rapeseed meal was limited. Some researches show that it is an effective method to modify the functional properties through hydrolyzing protein to get peptide. So the purpose of this subject is establishing a high efficiency peptide preparation technology using microwave technology on the base of previous study and studying the functional properties and antioxidative characteristic of the rapeseed peptide. The method is microwave assisted hydrolyzing the rapeseed protein by Alcalase, Flavourzyme and the two enzymes respectively. Through optimizing the important process parameters, the optimal microwave assisted enzyme hydrolysis condition is established. And then in the optimal condition the rapeseed peptide is prepared and study their functional properties and antioxidative characteristic. The research result is showing as following:1 By the analysis of response surface methodology (RSM), the optimal microwave assisted Alcalase hydrolysis condition is: microwave temperature 46℃, microwave power 500 W and microwave time 7 min. And in this condition the degree of hydrolysis (the DH) is 12.57% which is equal to the hydrolysis degree of hydrolysis in common water bath for about 4 hours (the DH is 14.14%). And because of the suitable heating pretreatment can make unfold of protein structure and make more hydrolysis sites contact with the enzyme, the reaction can process easily. Hence, it is very necessary to pretreat the rapeseed meal before the hydrolysis reaction. In this experiment, the water bath pretreatment of rapeseed meal is substituted by microwave heating and the result show that several minutes pretreatment using this method can achieve to the effect of 30 minutes water bath pretreatment. And the optimal pretreatment condition is microwave power 600 W, microwave temperature 75℃and microwave pretreatment time 3 min.2 The optimal microwave assisted Flavourzyme hydrolysis condition for rapeseed protein is microwave temperature 50℃, microwave power 500 W, microwave hydrolysis time 13 min, and the DH is 25.64%. The rapeseed peptide obtained from the rapeseed meal protein has good functional properties: the solubility can reach 55% when the DH is 25%; fat absorption and water absorption of the hydrolysate reach peak when the DH is 15% and 5%, respectively; the emulsifying activity and emulsifying stability could reach maximum when the DH was 10%; the foaming capacity of the hydrolysate is better than the rapeseed protein and the foaming capacity increase with the accelerate of the DH. And the study of antioxidative characteristic displayed that hydrolysate of different DH all had a certain extent antioxidative characteristic, which was determined by the molecular weight and the species of peptide in the hydrolysate.3 In this part experiment, the microwave assisted technology is used and the step enzymatic hydrolysis process of defatted rapeseed meal protein is studied. After the Alcalase hydrolysis, the Flavourzyme is used to hydrolyze the rapeseed meal protein continuously. The optimal dosage ratio of enzyme and rapeseed meal is 0.225 g/g, the ratio of the two enzyme is 2/1 (Alcalase 9 000 U/g, Flavourzyme 37.5 LAPU/g), the hydrolysis time is just 3 min for Alcalase and 13 min for Flavourzyme, and in this condition the DH is 53.67%. The verification test for the optimal condition show the DH and the nitrogen recovery ratio is 50.94% and 96%. And the molecular weight of mainly hydrolysate was 1000 Da.