Effects Of Different Processing Ways On The Antigenicity And Allergenicity Of Main Bovine Milk Proteins

Milk protein concentrate(MPC)is a concentrated skim milk protein powder,it has a widespread application as the skim milk.This present thesis is mainly foucused on the antigenicity and allergenicity of a-lactalbumin(α-LA),β-lactoglobulin(β-LG),α-casein(α-CN)and β-casein(P-CN)from the MPC.which were treated by heating,DHPM,fermentation,culture supernatants of lactic acid bacteria.To discover the change trends of the antigenicity and the allergenicity of four proteins under different processing methods,the value of pH,titratable acidity,hydrolysis degree of protein,free amino acid concentration and protein profile analysis by SDS-PAGE were detected.The main results were as follows:1.The effects of combination of different heat time and temperatures on the antigenicity and potential allergenicity of α-LA,β-LG,α-CN and β-CN in MPC were investigated.The antigenicity and potential allergenicity of α-LA decreased significantly.The antigenicity of α-LG increased sharply throughout the heat treatment.The potential allergenicity of β-LG increased firstly and then decreased under heating treatment,and the lowest value allergenicity occurred at 85℃.The antigenicity of a-CN and β-CN showed fluctuated changes,but were all lower than untreated sample.The allergenicity of a-CN decreased when heated at 65℃ and 70℃ for 25 min.Compared with untreated sample,the allergenicity of β-CN increased sharply under heat treatment.Therefore,heating treatment is not an effective way to reduce the antigenicity and allergenicity of four proteins in MPC.2.The MPC were treated by dynamic high-pressure microfluidization(DHPM)alone and DHPM combined with heat treatment(65℃,95℃ for 30min).The result indicated that DHPM treatment significantly increased the antigenicity of α-LA,β-LG,α-CN and β-CN in MPC.Compared with DHPM group,the antigenicity of α-LA,a-CN and β-CN antigenicity was significantly lower under DHPM combined with heat treatment.The high temperature and high pressure(140MPa,9℃)can significantly reduce the allergenicity of α-LA and β-LG,but there is no significant effect on allergenicity of α-CN and β-CN.3.The antigenicity and allergenicity of α-LA,β-LG,α-CN and β-CN in MPC which was fermented by Lactobacillus paracasei H9 were investigated during the fermentation and chilled storage.The results were as follows:(1)During fermentation,the antigenicity of α-LA,β-LG,α-CN and β-CN decreased significantly and then increased slightly with the prolonging of fermentation time.(2)The allergenicicity of α-LA and β-LG in the fermented MPC declined at the end of fermentation.The allergenicity of a-CN fluctuated during the fementation,and the lowest allergenicity were occurred at fermentation for 4h and 20h.The allergenicity of β-CN decreased firstly with the prolonging of fermentation time,and then increased,but it was always lower than the control group.In the fermentation process,the reduction of antigenicity and allergenicity for α-CN and β-CN in MPC fermentated by L.paracasei H9 is greater than that of α-LA and β-LG.(3)The antigenicity increased for a-LA but fluctuating declined for a-CN,and there was almost no changes for allergenicity of α-LA and α-CN.The antigencity and allergenicty of β-LG are decreased with the increase of storage time.The antigenicity of β-CN also decreased,but the allergenicity increased significantly.4.The MPC was treated by both fermentation using L.paracasei H9 and L.plantarum P8 and 120MPa DHPM,and the antigenicity and allergenicity of four milk proteins in the fermentation process were evluated.The results were as follows:(1)The antigenicity of α-LA,β-LG,α-CN and β-CN in MPC decreased significantly under fermentation and 120MPa DHPM.There was no significant difference between the antigenicity of a-LA fermentated by L.paracasei H9 and L.plantarum P8.The antigenicity of β-LG fermentated by L.plantarum P8 was reduced more effectively than L.paracasei H9.In contrast,the antigenicity of a-CN and β-CN fermentated by L.paracasei H9 were reduced more effectively than L.plantarum P8.(2)After the 120MPa DHPM treatment and fermentated by L.paracasei H9 and L.plantarum P8,the allergenicity of α-LA,β-LG in MPC did not change significantly.The allergenicity of α-CN andβ-CN decreased significantly.The allergenicity of β-CN fermentated by L.paracasei H9 was reduced more effectively than L.plantarum P8.The allergenicity of a-CN fermentated by L.plantarum P8 was reduced more effectively than L.paracasei H9.5.The culture supernatant of L.paracasei H9 and L.plantarum P8 were used to hydrolyze to evaluate the changes of the antigenicity and allergenicity for four proteins during hydrolysis.The main results were as follows:The effect of two lactic acid bacteria hydrolysate on the antigenicity of allergenic was better than that of allergenicity.The antigenicity and allergenicity of a-LA and P-LG were reduced more effectively by the culture supernatant of L.paracasei H9 than L.plantarum P8.The antigenicity and allergenicity of α-CN and β-CN were reduced more effectively by the culture supernatant of L.plantarum P8 than L.paracasei H9.