Study On Effects Of Different Treatments On Silver Carp Protein

The structure and properties of fish protein affect its processing and qualities directly, and the research on effects of different treatments on fish protein can lay the theoretical and experimental basis of its processing and application. This work used silver carp as raw material and mainly studied on effects of ultrasonic treatment, microwave treatment, heating and glycosylation on physical and structural properties of silver carp protein on the basis of investigating its optimum extraction process. The results were gotten as follows.The optimun extraction process conditions of silver carp were:solid-liquid ratio was1:9, pH was10, extraction time was60min.Solubility (S), emulsification activity (EA) and emulsification stability (ES), foaming activity (FA) and foaming stability (FS), hydrophobicity (Ho) tendency increased firstly and then showed a decreasing trend with the rise of ultrasonic power when fish protein was treated for15min with ultrasonic (160W-320W). When fish protein was treated with160W ultrasonic power between5min and25min, its S, EA, ES, FA and FS tendency increased firstly and then decreased with the ultrasonic treatment time going on while Ho tendency was increasing gradually from beginning to end.When fish protein was treated for30s with100-500W microwave, its S, EA, ES, FA, FS and Ho tendency increased firstly and then showed a decreasing trend with the rise of microwave power. When fish protein was treated with100W microwave power between10s and50s, its S, EA, ES, FA and FS tendency increased firstly and then decreased with the microwave treatment time going on. The tendency of Ho was increasing with the extension of microwave time.S, EA and ES, FA and FS tendency increased firstly and then showed a decreasing trend with the rise of heating temperature when fish protein was heated for5min with25℃-65℃. But Ho and amount of SSH showed a tendency of decreasing. When fish protein was heated with35℃(3min-llmin), S, EA, ES, FA, FS and H0tendency all increased firstly and then decreased with the heating time going on.The SDS-PAGE results were as follows:after being treated by three physical methods, compared with untreated samples, only the molecular size of fish protein treated by heating were changed. Results analyzed by IR showed that the content of α-helix and β-turn in fish protein both decreased while the amount of β-sheet increased all the time. The content of free curl increased in the ultrasonic group, but in the other two groups, free curl was not found.The best conditions of preparing fish protein-lactose conjugates were as follows:reaction temperature was70℃, reaction time was2h, the concentration of fish protein was5%. the ratio of fish protein to lactose was1:1, pH was7. The S of fish protein-lactose conjugates increased1.8times compared with that of untreated samples. Moreover, EA increased not obviously and ES increased10.2%. FA increased41.7%and FS decreased31.9%compared with those of the untreated. Results of SDS-PAGE showed that bands of fish protein decreased because of the covalent access of lactose molecules.