REQUIMTE-Serviço de Bromatologia, Faculdade de Farmácia da Universidade do Porto, Rua Anibal Cunha 164, 4099-030 Porto, Portugal.
J Dairy Sci. 2010 Jan;93(1):27-31. doi: 10.3168/jds.2009-2501.
The effect of kefir grains on the proteolysis of major milk proteins in milk kefir and in a culture of kefir grains in pasteurized cheese whey was followed by reverse phase-HPLC analysis. The reduction of kappa-, alpha-, and beta-caseins (CN), alpha-lactalbumin (alpha-LA), and beta-lactoglobulin (beta-LG) contents during 48 and 90 h of incubation of pasteurized milk (100mL) and respective cheese whey with kefir grains (6 and 12 g) at 20 degrees C was monitored. Significant proteolysis of alpha-LA and kappa-, alpha-, and beta-caseins was observed. The effect of kefir amount (6 and 12 g/100mL) was significant for alpha-LA and alpha- and beta-CN. alpha-Lactalbumin and beta-CN were more easily hydrolyzed than alpha-CN. No significant reduction was observed with respect to beta-LG concentration for 6 and 12 g of kefir in 100mL of milk over 48 h, indicating that no significant proteolysis was carried out. Similar results were observed when the experiment was conducted over 90 h. Regarding the cheese whey kefir samples, similar behavior was observed for the proteolysis of alpha-LA and beta-LG: alpha-LA was hydrolyzed between 60 and 90% after 12h (for 6 and 12 g of kefir) and no significant beta-LG proteolysis occurred. The proteolytic activity of lactic acid bacteria and yeasts in kefir community was evaluated. Kefir milk prepared under normal conditions contained peptides from proteolysis of alpha-LA and kappa-, alpha-, and beta-caseins. Hydrolysis is dependent on the kefir:milk ratio and incubation time. beta-Lactoglobulin is not hydrolyzed even when higher hydrolysis time is used. Kefir grains are not appropriate as adjunct cultures to increase beta-LG digestibility in whey-based or whey-containing foods.
通过反相高效液相色谱分析，研究了酸面团粒对酸面团乳和巴氏杀菌乳清中酸面团粒培养物中主要乳蛋白的水解作用。在 20℃下，监测了巴氏杀菌牛奶（100mL）和各自的乳清（含 6 和 12g 酸面团粒）孵育 48 和 90h 期间κ-、α-和β-酪蛋白（CN）、α-乳白蛋白（α-LA）和β-乳球蛋白（β-LG）含量的降低情况。结果表明，α-LA 和κ-、α-和β-CN 发生了显著的水解。α-LA 和α-和β-CN 的用量（6 和 12g/100mL）对其有显著影响。α-LA 和β-CN 比α-CN 更容易水解。在 48h 内，对于 100mL 牛奶中添加 6 和 12g 酸面团，β-LG 浓度没有明显降低，表明没有发生显著的蛋白水解。90h 时的实验也得到了类似的结果。对于乳清酸面团样品，α-LA 和β-LG 的水解行为相似：在 12h 后（对于 6 和 12g 酸面团），α-LA 被水解 60-90%，而β-LG 没有发生显著的蛋白水解。评估了酸面团菌群中乳酸菌和酵母菌的蛋白水解活性。在正常条件下制备的酸面团乳含有α-LA 和κ-、α-和β-CN 蛋白水解产生的肽。水解取决于酸面团与牛奶的比例和孵育时间。即使使用更长的水解时间，β-LG 也不会水解。酸面团粒不适合作为辅助培养物，以增加乳清或含乳清食品中β-LG 的消化率。
