The objective of the study was to characterize the effects of preheating of milk and of pasteurization steps during whey processing on the separation of transforming growth factor-beta 2 (TGF-β2) from whey protein concentrates (WPCs). Three heating conditions were applied to skimmed milk: no heating, 63 °C for 20 s and 68 °C for 20 s. The effect of pasteurizing liquid acid whey and liquid WPC was also assessed. Heating milk at 63 or 68 °C decreased TGF-β2 content of whey. A pasteurization treatment of whey at 72 °C for 15 s further decreased their TGF-β2 content. However, an additional pasteurization of WPCs significantly increased TGF-β2 only in samples from unheated milk. Acid precipitation of WPCs showed that cumulative heat treatments increased the amount of precipitate obtained, and that pH 4.5 was found to be optimal in terms of TGF-β2 content of precipitates. The highest TGF-β2 concentrations in acid precipitates (>10,000 pg.mg⁻¹ solids) were obtained with a combination of heating milk at 63 °C for 20 s and pasteurization of whey at 72 °C for 15 s. It was found that, although whey obtained from raw milk represents the best source of TGF-β2, an appropriate selection of heat treatments of liquid whey and WPC improves the recovery of TGF-β2. The presence of casein and minor whey proteins in TGF-β2-enriched fractions underlines the occurrence of complex heat-induced interactions between TGF-β2 and other milk constituents.

摘要 本文研究了牛乳的预热和乳清的巴氏杀菌过程对从乳清浓缩蛋白中提取TGF-β2回收率的影响。脱脂乳分别经过三种不同的热处理, 分别为未加热、63°C加热20s和68°C加热20s; 同时还评定了巴氏杀菌的液态酸乳清和液态乳清浓缩蛋白中TGF-β2的回收率。脱脂乳的63°C和68oC热处理降低了乳清中TGF-β2的含量; 如果这些乳清再经过72°C、15s的巴氏杀菌处理会进一步降低乳清中TGF-β2的含量。然而对未经热处理的乳清浓缩蛋白溶液进行巴氏杀菌, TGF-β2含量则显著地增加。酸沉乳清浓缩蛋白溶液由于经过多次累加的热处理, 若在pH4.5沉淀乳清蛋白可以获得最大量的TGF-β2。如果脱脂乳在63°C加热20s, 。然后乳清在72°C下加热15s, 可在酸沉乳清浓缩蛋白中获得最高浓度的TGF-β2 (10 000 pg mg–1固体)。尽管生乳乳清是TGF-β2的最佳来源, 但是对乳清和乳清浓缩蛋白进行适度的热处理也可以提高TGF-β2的回收率。热处理导致TGF-β2与其他乳成分之间形成复合物, 使得提取的富含TGF-β2的提取物中含有酪蛋白和一些微量的乳清蛋白。