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.
