Thermal denaturation kinetics of whey proteins in reverse osmosis and nanofiltration sweet whey concentrates

Shelf-stable whey concentrates produced by membrane filtration represent an energy efficient alternative to whey powder. However, to obtain products with sufficient microbiological shelf-life, preservation of concentrates is necessary. The idea of this study was, therefore, to investigate the influence of ionic composition and dry matter (DM) of whey concentrates on thermal stability of the major whey proteins. Taking the thermal impact of heating up into account, denaturation kinetics of β-lactoglobulin and α-lactalbumin were determined in reverse osmosis (RO) and nanofiltration (NF) whey concentrates with DM contents of 12–30% at heating temperatures of 90 and 125 °C. Denaturation caused by heating up was strongly increased with increasing DM of both types of concentrates. During holding at 90 °C, whey proteins showed a higher thermal stability in RO concentrates as compared with NF concentrates. However, denaturation rates at 125 °C of whey proteins were lower in NF than in RO concentrates.