Ultra high temperature (UHT) stability of casein-whey protein mixtures at high protein content: Heat induced protein interactions.

Although whey proteins have high biological value, their application to UHT processed high protein neutral beverages is limited due to their low heat stability. This research aimed to exploit the chaperone activity of caseins to improve UHT stability of whey proteins. UHT stability of reconstituted milk protein concentrate (RMPC), reconstituted whey protein concentrate (RWPC) and samples with various casein to whey protein ratios (C:W) (80:20 to 40:60) was studied. A 2% protein RWPC caused severe fouling suggesting its poor UHT stability. However, 10% protein RMPC was very stable (UHT run-time > 120 min). Inclusion of caseins caused stabilization of whey proteins to UHT processing and 10% protein C:W-50:50 was successfully processed for >120 min. Further increase in whey proteins proportion in milk protein dispersions caused a drop in run-times (below 120 min) and overall heat transfer co-efficient (OHTC), corresponding with increase in particle size and apparent viscosity. Presence of higher amounts of casein in the serum phase of samples caused formation of smaller protein aggregates (D(4,3) was 0.23 and 0.16 μm for supernatants of C:W-40:60 and RMPC, respectively) after heating. These results can help to increase the whey protein content of neutral pH, UHT processed high protein ready to drink beverages.