Effects Of Chitosan On The Gelling Properties Of Fresh Water Fish Surimi

Chitosan is a safe,non-toxic and easily degradable food additive,which has been widely used in occident,Japan,South Korea and other international markets as food additive, nutritional supplements.Chitosan has also been approved in China for food additive,but its application in food is still in the initial stage.Effects of chitosan on the gelling properties of fresh water fish sufimi was studied in this study.The above research could provide theoretical guidance for the application of chitosan in food.Rheological properties of chitosan solution was studied and the effects of viscosity average molecular weight,shear rate,chitosan concentration,temperature,pH and salt ion concentration on chitosan solution were measured.Chitosan solution was pseudoplastic fluid and its viscosity decresed with increasing shear rate,salt ion concentration and temperature. When the chitosan solution concentration was higher than 0.4%(w/v),the effect of chitosan concentration on viscosity become very significant.Chitosan soluton showed the maximum viscosity when the pH value of chitosan solution was 4.2.Chitosan was applied to fresh water fish surimi,the effects of chitosan with different degrees of deacetylation(DD),molecular weights(Mw) and adding amount on the texture and qualities of surimi-based products were investigated and gel strength,TPA,water loss rate and color were measured.The results showed that addition of chitosan with 64%DD resulted in significant increases in both texture properties and water-binding capacity.The gel strength increased approximately by 34%and water loss rate decreased by 29.1%.Different molecular of chitosan had no marked difference on surimi-based products gelling properties.The gelling properties of surimi-based products increased proportionally to the amount of chitosan added up to 1%(P＜0.05).Sense evaluation indicated that silver carp surimi with 1.0%chitosan had higher springiness.The same results could also be found in grass carp surimi.Surimi adding 1.0%chitosan had similar sensory level with that adding 4.0%starches.Effects of chitosan mixed with CaCl₂ and rinsing times on surimi-based products gelling properties and interaction between chitosan and protein were discussed.Scanning electron microscopy was used to observe the microstructure of the gels.Also,SDS-polyacrylamide gel electrophoresis(SDS-PAGE) was used to analyze the relevant mechanisms.The experiment of adsorption of chitosan on salt-soluble protein was also conducted.The results showed that synergistic effect of CaCI2 and chitosan could not be found.The gel strength of three times rinsing surimi with 1.0%chitosan equaled one time rising surimi.It was feasible to add 1.0% chitosan to surimi which was rinsed one time.Scanning electron microscopy indicated that chitosan could facilitate surimi forming gel network.It showed that adsorption of chitosan on salt-soluble protein at 30℃was very rapid in the first 10 minutes,the absorbency(OD value) reduced from 0.125 to 0.075,after 10 minutes,adsorption of chitosan on salt-soluble protein reached equilibrium.The combination between chitosan and protein was very weak.The above study suggested that chitosan is effective in improving surimi texture and qualities.It is promising to apply chitosan to food.