Comparison of vanilla-flavored milk protein beverages thermally processed by direct steam injection, retort, and autoclave.

Ready-to-drink protein beverages are a growing product category. The objective of this study was to determine the effects of 3 common thermal processes: UHT pasteurization with direct steam injection (UHT-DSI; 142°C for 3 s), retort (123°C, time to achieve sterilization = 5 min), or autoclave (112°C for 6 min) on the chemical, physical, and sensory properties of reconstituted vanilla-flavored milk protein beverages containing approximately 6.5% protein. Unheated and heated beverages were subjected to composition, minerals, pH, color, apparent viscosity, particle size, trained panel profiling, volatile compound analysis, and furosine analyses. High NPN values in retort and autoclave beverages indicated possible interaction of lactose with whey proteins that increased their solubility in 12% trichloroacetic acid. Heated beverages had higher b* values than unheated beverages. Sulfur-eggy flavor was only detected in the UHT-DSI beverages, and these beverages had the highest relative abundance of hydrogen sulfide and methanethiol. Caramelized flavor was only detected in retort and autoclaved protein beverages. These beverages had higher relative abundances of nearly all aldehydes, alcohols, esters, ketones, and furans than unheated and UHT-DSI beverages, indicative of Maillard reaction and Strecker degradation products that contributed to the characteristic caramel flavor. Furosine was not a good heat indicator for reconstituted milk protein beverages. Furosine values were higher for unheated rehydrated milk protein beverages than for thermally processed beverages.