The Digestibility Of Nanofibrils Aggregates In Vitro And The Improving Its Properties By Limited Hydrolysis

Whey protein and soy protein are high-quality natural proteins in nature. Recent studies have shown that these two proteins can be formed nanofibrils aggreagetes at low pH, low ionic strength and high temperature for a long time under heating. Currently, the formation conditions and formation mechanism of amyloid fibril structure had attracted widely attention, while, researching on the properties of nanofibers was less. Therefore,in order to develop new functional properties of the nanofibrils aggregates, broaden the applying in the food industry, compared the difference of structure and function of animal and plant protein nanofibrils aggregates and normal aggregates.This experiment using two kinds of materials, namely whey concentrate protein(WPC) and ?- conglycinin(7S) to prepare nanofibrils aggregates. Comparison and analysis the change of surface hydrophobicity,turbidity and free thiol groups during heating。Disscussed the effect of the amounts of pepsin and trypsin on in vitro digestion.At the same time, exploring the effect of hydrolysates of nanofibrils aggregates on antioxidant activity and emulsification. The results are as follows:Basic properties compared with normal aggregates, nanofibrils aggregates had the characteristics of high surface hydrophobicity, small sample turbidity, the heating process a small amount of free sulfhydryl groups of variation.The surface hydrophobicity of 7S nanofibrils aggregates was significantly higher than those of WPC nanofibrils aggregates.In vitro digestion of WPC In the gastric environment, Compared with normal aggregates, WPC nanofribrils were easily hydrolyzed by pepsin, and the changing of the added amounts of the enzyme will not affect the changing in the law. In three stages polymer nanofibers formed, nanofibrils aggregates had the maximum degree of hydrolysis in nucleation(the first stage),however,the degree of hydrolysis had slightly decrease after stable(the third stage). In the intestinal environment, nanofibrils aggregates had the maximum degree of hydrolysis in stable stage.When the E/S=1/30(5966U/g protein), Compared with normal aggregates, WPC nanofribrils were easily hydrolyzed by trypsin; Increasing the amounts of enzymes, the changing of DH% of the nanofibrils is very little, so the degree of hydrolysis of normal aggregates was higher than nanofibrils aggregates.In vitro digestion of 7S In the gastric environment, compared with normal aggregates, 7S nanofribrils are difficult hydrolyzed by pepsin, and the changing of the added amounts of the enzyme will not affect the trend in the law. In three stages polymer nanofibers formed, 7S nanofibrils aggregates had the maximum degree of hydrolysis in nucleation stage(the first stage),however,the degree of hydrolysis had slightly decrease after stable stage(the third stage). In the intestinal environment, compared with normal aggregates, the degree of hydrolysis of nanofibrils aggregates was larger and easily hydrolyzed by trypsin. Simultaneously, increasing the amounts of enzyme only changed the degree of hydrolysis, does not change the trend.7S nanofibrils aggregates had the maximum degree of hydrolysis in stable stage.Antioxidant activity Nanofibrils aggregates has good antioxidation activity, significantly higher than conventional polymers. Compared with normal aggregates, for example, the rate of increase of DPPH radical scavenging of WPC nanofibril aggregates was 94.91%, the rate of increase of DPPH radical scavenging of 7S nanofibril aggregates was 271.70%. Limited eneyze can improve the increasing of antioxidation activity. Pepsin is the most beneficial to improve the antioxidation activity of WPC and 7S nanofibrils. So,this paper finally selected the best hydrolysis conditions:protein concentration 2wt%, pepsin(E/S=1/3,17998U/g protein), hydrolysis 1h, hydrolysis temperature 37℃,the degree of hydrolysis of WPC nanofibril aggregates was17.06%, the degree of hydrolysis of 7S WPC nanofibril aggregates was 12.19%. Among them,after hydrolazed,the DPPH radical scavenging of WPC nanofibril aggregates was 1.48 times than those WPC normal aggregates; the DPPH radical scavenging of 7S nanofibril aggregates was 1.82 times than those WPC normal aggregates.The improvement of emulsification properties by limited hydrolysis compared with normal aggregates, WPC nanofibrils aggregates had good emulsification properties,7S nanofibrils aggregates had slightly lower emulsification properties. Limited eneyze can improve the increasing of emulsification properties. Compared with trypsin, Pepsin is the most beneficial to improve the emulsification properties of WPC and 7S nanofibrils.Then, this paper finally selected the best hydrolysis conditions of WPC nanofibrils aggregates:protein concentration 2wt%, pepsin(E / S = 1/3, 17998U/g protein)), hydrolysis 25 min, hydrolysis temperature 37℃,the degree of hydrolysis of WPC nanofibril aggregates was13.64%.For 7S, the best hydrolysis conditions: protein concentration 2wt%, pepsin(E/S =1/30,1799U/g protein), hydrolysis 1.42 h, hydrolysis temperature 37℃,the degree of hydrolysis of WPC nanofibril aggregates was 5.57%. After hydrolazed,the the emulsion stability of WPC nanofibril aggregates was 13.15 times than those WPC normal aggregates; the emulsion stability of 7S nanofibril aggregates was 22.42 times than those 7S normal aggregates.