Heat stable whey protein stabilised O/W emulsions : optimisation of the whey protein concentrate dry heat incubation conditions

The industrial application of whey proteins as a food emulsifier is still limited due to its susceptibility towards heating. In this study, dry heat conjugation of whey protein and lactose was investigated to improve the heat stability of WPC-stabilised oil in water (O/W) emulsions. A commercially available whey protein concentrate (WPC), containing 80 % protein and 12 % lactose, was dry heat incubated. Hereby, the effect of incubation temperature (60, 70, and 80 degrees C), relative humidity (64, 74, and 79 %), and preconditioning pH (4, 6, 8, 10) were determined. Temperature variation showed a pronounced effect on the required duration to obtain conjugates with excellent emulsion heat stabilising capacity. Four hours of incubation at 80 degrees C was sufficient to retain the original particle size and consistency after heating the emulsions at 80 degrees C for 20 min. Whereas circular dichroism spectroscopy revealed that this dry heat incubation condition (80 degrees C, 4 h) maintained the secondary structure of WPC, pulsed-field gradient NMR revealed that about 40 % of the lactose present should become protein-bound to generate conjugates with the desired functionality. The results indicated that a heat stable WPC with about 40 % of bound lactose could be obtained by some hours of dry heat treatment at 80 degrees C