德氏乳杆菌保加利亚亚种发酵对牛乳中β-酪蛋白抗原性的影响

Effect of fermentation with Lactobacillus delbrueckii subsp.Bulgaricus on the antigenicity of β-casein in cow's milk

复原脱脂牛乳经德氏乳杆菌保加利亚亚种发酵至凝乳,然后在4℃下冷藏5 d。用间接竞争ELISA法测定了其中β-酪蛋白(β-CN)的抗原残留量,并且对发酵样品的蛋白水解程度与滴定酸度进行了分析。结果表明,复原脱脂乳经90～95℃处理5 min后,β-CN的抗原残留量为60.25%,发酵过程中其抗原残留量持续下降,凝乳时下降到55.46%,而冷藏1 d后降到了最低值54.03%,随后又缓慢上升,冷藏3 d后为55.87%,继续冷藏至5 d,β-CN的抗原残留量基本没有变化,维持在55.5%与55.9%之间。因此采用德氏乳杆菌保加利亚亚种发酵能够在一定程度上降低牛乳中β-CN的抗原性,但是在冷藏5 d的过程中其抗原性又有一定程度的升高。

Reconstituted skimmed milk was fermented to form into curd with Lactobacillus delbrueckii subsp. Bulgaticus, then stored at 4 ℃ for 5 days. The residual antigenicity ofβ-casein q3-CN） in it was estimated by indirect competitive ELISA method, the hydrolysis degree of milk proteins and titratable acidity were analysed as well. The results indicated that, after processing in 90-95 ℃ for 5 rain, the residual antigenicity ofβ-CN was 60.25%, and it decreased throughout the fermentation, to 55.46% when the milk formed into curd. The lowest antigenicity 54.03% appeared when the milk was stored at 4 ℃ for 1 day, then it went up slightly to 55.87% when the storage time extended to 3 days. Followed by storage in 4 ℃（2 to 5 days, the residual antigenicity ofβ-CN remained between 55.5% and 55.9%. It was proved that fermenta- tion with Lactobacillus delbrueekii subsp. Bulgaricus could reduce the antigenicity of^-casein in cow＇s milk to some extent, but it goes up a little when the ferment product is stored in 4 qC for 5 days.