Hydration effect of whey protein treated by glow discharge plasma

Glow discharge plasma (GP) was used to study the hydration mechanism of whey protein with different moisture content (10%, 20%, 30%). When the moisture content was 20%, the effect was most obvious. Strong hydration effect was confirmed by Fourier transform infrared spectroscopy (FTIR) results with sharper, narrower and blue-shifted from 3283.49 cm−1 to 3286.26 cm−1, indicating the enhanced hydrogen bond. More flexible protein structure with a significant decrease in α-helix content (from 18.50% to 14.62%), β-sheet content (from 29.67% to 19.38%) and crystallinity degree (from 6.18% to 0.81%) was introduced. Whey protein underwent oxidation reactions of CC to C–O–C(H) and further to COOH, C–OH to C–O–C and sulfhydryl to disulfide bonds. The scanning electron microscopy (SEM) results showed that the treated whey protein was highly aggregated (from 55.40 μm to 226.87 μm) and formed porous and rough polymers. Additionally, the treated whey protein exhibited higher anti-oxidation activity, with DPPH, ABTS and OH free radicals increased by 14.55%, 11.08% and 15.56%. The water/oil holding capacity and light transmittance of whey protein was improved by 18.18%, 22.05% and 35.69%, respectively.