Study On Recovery And Properties Of Proteins From Surimi Wash Water

The factories which is producing surimi discharge surimi wash water directly,and the surimi washed water contains a great deal of protein.This behavior not only wasted resources,but also polluted environment.Therefore,recovering proein from surimi wash water can decreases environmental pollution and increases profits of enterprises.This thesis studied the following aspects,and the research contents and results are also included.Proteins were recovered from Grass carp surimi wash water by pH adjustment in the range of 3.5-6.5.The nutrition components,physiochemical and functional properties of proteins were analyzed.The results showed that the protein recovery rate arrive 50.8%when the pH is 5.5.Through nutritional evaluation,the recovered protein was the high quality protein.SDS-PAGE analysis showed that recovered protein from different pH conditions had similar protein strips which displayed mainly from 27 KDa to 97 KDa.Studies of functional properties showed that foaming capacity and emulsifying activity were negatively related to the solubility.Alkaline protease was identified as the most suitable enzyme among 5commonly used enzymes based on simultaneous consideration of trichloroacetic acid nitrogen solubility index(TCA-NSI)and degree of hydrolysis(DH).According to single factor experiments and response surface,the optimal enzyme reaction system was obtained as follow:hydrolysis temperature of 52.51℃,hydrolysis pH of 9.06,enzyme addition amount of 1.42%,hydrolysis time of 60 min and 1 g/100mL substrate concentration.Under the optimal hydrolysis conditions,the TCA-NSI and DH were 73.5%and 20.86%.The functional properties of protein before and after hydrolysis were compared,the results showed that the solubility,emulsifying and foaming of protein increased after enzymatic hydrolysis.However,the emulsifying stability,oilabsorption capacity and foaming stability decreased.Enzymatic hydrolyzate of proteins were recovered from surimi wash water as raw material.Maillard reaction products(MRPs)were prepared by the reaction with four different varieties of sugar(glucose,D-fructose,sucrose and lactose),the impact of Maillard reaction on antioxidant activity were studied in this research.Glucose was identified as the most suitable sugar based on DPPH radical-scavenging activity.According to response surface,the optimal Maillard reaction conditions was obtained as follow:reaction temperature 126.92℃,reaction initial pH of 10.39,reaction time of 3.89 h and glucose concentration of 3 g/100 mL.Under the optimal reaction conditions,the hydroxyl radical scavenging activity increased from 34.83%to61.82%,the DPPH radical scavenging activity,ABTS scavenging activity and reducing power were enhanced.It indicating that the antioxidant activities of fish protein hydrolysates were improved by Maillard reaction.Finally,the structure and flavor compounds of the Hydrolysate and MRPs of Hydrolysate were analyzed by FTIR,fluorescence analysis and SEM.The MRPs of Hydrolysate have the strongest fluorescence intensity when emission was 347 nm and the excitation was 425 nm.It was observed with IR spectrum that MRPs broadened absorption peak compared to the MRPs of Hydrolysate in the 3700-3200 cm~-11 and1110~1050 cm~-11 office.The result comfirmed that the Maillard reaction was occured.SEM of Hydrolysate before and after the Maillard reaction showed that,the surface structure of the Hydrolysate was different from MRPs of Hydrolysate.