Study On The Properties Of Digestive Enzymes From Marine Products And The Effects Of Which On The Product Quality During Processing

Penaeus chinensis, Scylla serrata, Dalian trepang, Hatiotis disws hannai Ino, Chlamys Farreri, Sea snail and Clam were chosed as experimental raw materials. The activities of digestive enzymes extracted from digestive gland of fresh marine products were compared, and the properties of digestive enzymes were studied. Through the research on the changes of digestive enzymes activities, soluble protein content, reducing sugar content, TVB-N content in low temperature processing, normal temperature processing and natural thawing processing, it could be analysised the way how the digestive enzymes influence product quality during processing.The results showed that the activities of digestive enzymes from marine products:Penaeus chinensis> Scylla serrata> Dalian trepang perisome> Dalian trepang bowel> Hatiotis disws hannai Ino, Chlamys Farreri> Sea snail, Clam.The properties of digestive enzymes from marine products were studied, and the results indicated that:The optimal temperature of protease for Penaeus chinensis was60℃and the optimal pH was9.0. The protease was stable at temperature lower than over50℃and over a broad pH range(7.0～10.0). With casein as the substrate, the optimal substrate concentration for protease was3%. When60℃, the half-life period of the protease was22min, and it was7min for70℃. Low concentration of EDTA could inhibite the protease. Mn2+, Ca2+and Mg2+could activate the protease, but Zn, Cu, Fe, Pb2+inhibite the enzymes to different extents depending on the ions used. The optimal temperature of amylase for Penaeus chinensis was60℃and the optimal pH was7.0. The optimal temperature of protease for Scylla serrata was60℃and the optimal pH was9.0. The enzymes were stable at temperature lower than over40℃and over a broad pH range(8.0～10.0). With casein as the substrate, the optimal substrate concentration for protease was2%. When60℃, the half-life period of the enzyme was17min, compared with5min for70℃. Low concentration of EDTA could inhibite the enzymes. Mg2+and Pb2+could activate the protease, but Zn2+, Cu2+, Fe2+, Ca2+and Mn2+inhibite the enzymes to different extents depending on the ions used. The optimal temperature of amylase for Scylla serrata was40℃and the optimal pH was6.0.Through the research on the effects of digestive enzymes on products quality during processing, the results showed that:In low temperature processing, Penaeus chinensis and Scylla serrata were both not suitable for processing in the conditions of10℃. The processing time in4℃would be controlled within2days. The quality guarantee period of0℃was5days. In normal temperature processing, the processing time of Penaeus chinensis should not be more than3hours. The processing time of Scylla serrata was controlled in less than2hours. Relatively in low temperature, processing time of normal temperature was too short to control the changes of the quality, and it had a direct impact on the quality of raw materials. In natural thawing processing, with frozen Penaeus chinensis as raw material, the thawing effect reached to the state of micro-ice and the thawing time should not be more than3h, so the fresh materials were suggessted to be used in the low temperature processing.