Effect of oxidized and unoxidized onion extracts on gel strength and antioxidant activity of pangasius surimi gels

抄録

[Objective] Pangasius, a freshwater fish, is used as raw material for surimi preparation due to its availability and low price. However, its gel-forming ability is low compared to the cold-water fish surimi. It has been reported that adding polyphenols could improve the gel strength of surimi. Onion extracts containing abundant polyphenols can be a promising option that can modify the characteristics of the protein gels. Furthermore, oxidized polyphenols have a higher capacity to interact with proteins by cross-linking and strengthening surimi gel. Also, the addition of onion extracts is expected to increase the antioxidant capacity of the surimi gels and prolong shelf life. Therefore, this study aims to improve pangasius surimi gel strength and antioxidant capacity by incorporating onion extracts (OE) and oxidized onion extracts (OEox).

[Method] Surimi gels were prepared using 0-0.150% OE and OEox of surimi by two-step heating at 50°C for 20 min and then 90°C for 20 min. The characteristics of the gel was decided by gel strength, color, protein cross-linking, intrinsic fluorescence, and antioxidant activity.

[Results] The breaking force and deformation of surimi gels increased in OE and OEox gels compared to the control (0% extracts). OEox showed a higher breaking force for all the concentrations than the OE, and the highest gel strength was observed by adding 0.100% OEox. The cross-linking ability evaluated by SDS-PAGE and free amino group content was higher in OEox gels than in the OE gels. The intrinsic fluorescence properties suggested that OEox could induce more conformational changes than the OE. Antioxidant activity in OEox-treated gels was higher than in the OE gels.