E-beam Irradiated Freeze-Dried Whey Fractions and Skimmed Camel and Cow Milk: Solubility, Water Holding Capacity, Microstructure and In Vitro α-amylase and α-glucosidase Inhibitory Activities

Ionizing radiation, as electron beam (E-beam), is regarded as an environmentally friendly food preserving technology with potential to enhance the bioactive content and bioactivity of food products. This study evaluated the rehydration properties, solubility, microstructure, and bioactivities (antioxidant and in vitro α-amylase and α-glucosidase inhibitory activities) of freeze-dried whey, and corresponding skimmed cow and camel milk, using or not electron beam (E-beam) irradiation at doses of 5, 10, and 20 kGy. E-beam irradiation generally caused a notable decrease in water holding capacity (from 20 to 66%) and affected solubility, with significant decline (14—77%) followed by a partial restoration at 20 kGy. Microstructure analysis suggested protein denaturation including disaggregation at 5 and 10 kGy and aggregation at 20 kGy along with a disruption of the protein network. E-beam irradiation generally increased the total phenolic content in freeze-dried cow milk but had variable effects on freeze-dried camel milk. Freeze-dried camel milk demonstrated heightened sensitivity to irradiation doses in terms of antioxidant activity, whereas cow milk exhibited resilience. Freeze-dried skimmed cow and camel milk showed dose-dependent changes in α-amylase inhibitory activity, while α-glucosidase inhibition either increased or remained stable. These findings underscore the significant effect of E-beam irradiation on the bioactivity and micro-structural properties of freeze-dried whey and milk, revealing distinct responses between cow and camel milk.