Effect of milk thermal history on the recovery of TGF-β2 by acid precipitation of whey protein concentrates
2011
Rocafi, Adil | Lamiot, Éric | Moroni, Olivier | Turgeon, Sylvie L. | Gauthier, Sylvie F. | Pouliot, Yves
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.
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