Effect of chitosan on gelling properties, lipid oxidation, and microbial load of surimi gel from African catfish (Clarias gariepinus)

Abstract

In this study, the effect of addition of different concentration of chitosan (0%, 0.25%, 0.5%, 0.75%, 1.0%, 1.25%, 1.5%, 1.75% and 2.0% w/w) to surimi gels made from African catfish on gelling properties, lipid oxidation and microbiological changes during 20 days storage at 4 C were evaluated. In general, surimi gels added with 1.5% (w/w) chitosan showed the highest improvement in gel strength (58.92%), whiteness (13.18%), and water holding capacity (36.8%). Incorporation of 2% (w/w) chitosan treated gels also resulted in lowest pH (6.84) and TVB-N value of 36.63 mgN/1 OOg at the end of 20 days storage period. The lipid oxidation of catfish surimi gel were evaluated through measurement of primary (peroxide value) and secondary (malonaldehyde) oxidation products. Both PV and TBA value of chitosan treated gels increased slower than the control gel during the storage period. Chitosan with concentration of 1.75% and 2.0% (w/w) showed the best antioxidant effect on catfish surimi gels. A significant reduction was also observed in aerobic plate count of catfish surimi gels added with chitosan of concentration 1.75% and 2.0% (w/w). Based on microbiological acceptability limit (10 ° cfu/g), the shelf life of surimi gels with level of 1.75% and 2.0% (w/w) were estimated to be 4 to 12 days compared to the control samples which last only 8 days in refrigerated storage at 4 6 C. Hence, the addition of 1.5 % to 2.0 % (w/w) concentration of chitosan can be considered as a promising approach in the preparation of catfish surimi gels by improving texture, preventing lipid oxidation and inhibiting microbial growth.