Effect Of Heat-induced ?-lactoglobulin Aggregation On Its Digestion Behavior

The aggregated structure of the protein can affect its digestion behavior and the physicochemical properties of the digested products.In this study,BLG fibril aggregates(BLGF),BLG nanoparticle aggregates(BLGN)and BLG worm-like aggregates(BLGW)were prepared by adjusting the pH,heating time and heating temperature of ?-lactoglobulin(BLG)dispersions.The effects of thermal aggregation on the digestion behavior of BLG and the antioxidant activity of its digested products were analyzed.Furthermore,the effects of electrostatic interaction between protein and polysaccharide on the digestion behavior of protein were also studied.The main conclusions obtained are as follows:(1)BLGF,BLGN and BLGW were treated with DTT,urea and SDS,respectively,to investigate the mechanisms of how internal force and surface hydrophobicity effect the digestion behavior of BLG.On the perspective of internal forces,hydrogen bonds and disulfide bonds inhibit protein digestion,and surface hydrophobicity bonds promote protein digestion.ON the perspective of protein secondary structure analysis,?-helix and random curl are beneficial to protein digestion;?-sheet is not conducive to protein digestion.On the perspective of enzyme action,the stronger the surface hydrophobicity,the more binding sites in the hydrophobic group to pepsin,the more favorable for digestion.(2)The effects of thermal aggregation on the digestion behavior of BLG and the antioxidant activity of digested products were studied.The results showed that the hydrolysis degrees of BLGN,BLGW,BLGF and BLG in simulated gastric juice were 11.86±0.24%,10.55±0.22%,9.08±0.21% and 3.46±0.16%,respectively.DPPH·free radicals of BLG digestion products after heat accumulation.The clearance rate,hydroxyl radical scavenging rate and superoxide anion radical scavenging rate were all decreased,but the reducing ability was increased,and BLGF had the highest reducing ability.(3)The effect of BLG interaction with dextran sulfate on the digestion behavior of BLG thermal aggregates was studied.The results showed that dextran sulfate inhibited the formation of BLGF,BLGN and BLGW,and the digestibility of BLG decreased with the increase of dextran sulfate concentration.The inhibitory effect of dextran sulfate on BLGF was the most obvious.The digestibility of BLGF was 7.71± 0.22%,and when the ratio of added dextran sulfate to BLGF was r=6,the digestibility was reduced to 0.61±0.10%.(4)Based on the theory that dextran sulfate affects protein digestion,dextran sulfate was added in the milk powder production process to prepare milk powder containing different protein structures.The results showed that the surface water hydrophobicity,particle size,oil holding capacity and protein digestibility of the milk powder prepared after the addition of dextran sulfate were decreased,and the solubility and water holding capacity were improved.When the added amount of dextran sulfate added was from 0 to 1.00%,the digestibility of milk powder F decreased from 3.49±0.15% to 1.50±0.10%,and the digestibility of milk powder N decreased from 5.31±0.15% to 3.55±0.18%.The digestibility of milk powder W decreased from 5.58 ± 0.15% to 2.91 ± 0.11%.