Hygroscopic properties of whey protein hydrolysates and their effects on water retention in pork patties during repeated freeze–thaw cycles

The hygroscopic properties, water migration properties and micromorphology of native whey protein (NWP) and whey protein hydrolysate (WPH) under different relative humidity (RH) conditions were assessed in this study. Moreover, their effects on water retention in pork patties during freeze–thaw (F–T) cycles were assessed. The results showed that the moisture absorption rate of WPH was 7.45 percentage units higher than that of NWP after the moisture content balance. When the RH reached 97.0%, the equilibrium moisture content of WPH was 1.81 times that of NWP. Combined with low-field nuclear magnetic resonance and microstructure results, WPH exhibited the strongest moisture absorption and moisturising abilities and was more suitable for addition to meat systems. Furthermore, the addition of WPH effectively improved water retention in pork patties during F–T cycles. After seven F–T cycles, the addition of 15% WPH effectively inhibited myofibrillar protein degradation and microstructural damage, reduced the relative content of α-helix and the water holding capacity loss of pork patties and enhanced proton density. These results indicate that WPH has the potential to be used as a water retention agent candidate to reduce the quality loss of meat products during F–T cycles.