Radio-frequency treatment for stabilization of wheat germ: Storage stability and physicochemical properties

Abstract

Abstract Wheat germ (WG) is a nutritional valuable by-product of wheat milling. However, presences of high lipase (LA) activity and high content of unsaturated fatty acids induce rapid lipid rancidity in WG during storage. The aim of this study was to inactivate LA activity and improve the lipid stability of WG using radio-frequency (RF) heating treatment. Meanwhile, the color, functional, structure and antioxidant properties of WG samples stabilized by effective RF and conventional steaming treatments were also compared. Results indicated that WG stabilized by RF heating to 100 °C with holding for 15 min in hot air or heating to 110 °C with holding for 5 min could effectively inactivate LA activity to 18.2% or 22.5% of their original values. Under these conditions, the WG can be maintained with the acceptable oil quality for >90 d at controlled room condition in zip-lock PE bags. The color values and water/oil absorption capacity of WG were improved by RF stabilization treatments, but the protein solubility (PS) and foaming properties were reduced. RF stabilized WG also showed comparable emulsifying properties, total phenolic content (TPC) and antioxidant capacity (AC) to those of control. Compared with steam treatments, RF stabilized samples exhibited a brighter color, higher PS, TPC, or AC, better foaming/emulsifying properties, and clearer outline presence with intact starch granules in microstructure. RF treatments could be a promising stabilization method and improve some physiochemical properties of WG, which are important for industrial applications.