Effects of Extraction Methods on Functional Properties and Antioxidant Activity of Ginkgo biloba Proteins

This paper investigated the effects of water extraction and acid precipitation (WEAP), alkali extraction and acid precipitation (AEAP), and ultrasound-assisted alkali extraction and acid precipitation (UA-AEAP) on the functional properties and antioxidant activity of Ginkgo biloba proteins (GBPs). The functional properties of GBPs were evaluated through solubility, foaming capacity, foam stability, emulsifying capacity and emulsion stability. The DPPH radical scavenging ability, hydroxyl radical scavenging ability and chelated iron assays were employed to assess the effects of extraction methods on antioxidant activity of GBPs. The results showed that the yield and solubility of GBPs were significantly affected by the extraction methods. The UA-AEAP had the highest yield (11.36%±0.10%), and highest solubility in the pH range from 2 to 12. Foaming, foam stability and emulsification of GBPs were significantly influenced by the extraction methods(P<0.05), while the emulsion stability was not notably related to the extraction methods(P>0.05). The foaming, foam stability and emulsification of GBPs prepared by UA-AEAP were better than those of AEAP and WEAP. Moreover, the order of the chelating ferrous ionsability, scavenging 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical ability and scavenging hydroxyl radical ability were UA-AEAP>WEAP>AEAP. UA-AEAP was appropriate for the preparation of GBPs due to its higher yield, stronger antioxidant capacity and better functional properties.