Properties of whey protein concentrate powders obtained by spray drying of sweet, salty and acid whey under varying storage conditions

Changes of secondary structure and protein interactions of whey protein (WPs) present in native, sweet, acid and salty-WPCs were analyzed following storage at 4, 25 or 45 degrees C and 22 or 33% relative humidity for a period of 90-days. WPs aggregated predominantly through covalent crosslinking, achieving maximum at 45 degrees C and 33% RH. Greater participation of beta-lactoglobulin in covalent crosslinking was evident in all WPCs, while that of alpha-lactalbumin was significantly (p < 0.05) high in acid-WPC only. Reaction order of beta-LG denaturation in acid and salty-WPCs was approximately 2 while approximately 1 in native and sweet WPCs. Activation energy was significantly (p < 0.05) higher in native and sweet-WPCs, with averages recorded as 97 and 49.8 kJ mol(-1), respectively, than that in acid and salty-WPCs with averages of 27.5 and 33.8 kJ mol(-1), respectively, mainly attributed to inherently high concentrations of lactic acid and salts in these WPCs.