| Squid is an important cephalopod seafood in China.With the increase of people demand for squid,squid production is also increasing year by year.The squid is not only eaten fresh,but also processed into squid silk,squid pieces and other leisure flavor food,the utilization rate of squid is low.The intensive processing of squid is less,so the nutritional value of squid can be improved by further study of squid processing technology.In this study,firstly,squid protein was extracted from Argentine squid by salting out method.Then determined molecular weight by sodium lauryl sulfate polyacrylamide gel electrophoresis(SDS-PAGE).Secondly,squid was hydrolyzed into squid protein polypeptide,and its molecular weight was determined by high performance liquid chromatography(HPLC).Finally,squid peptides reacted with glucose,and studied abilities of scavenging radical.The antioxidant activity of squid peptides with different molecular weight and the effect of Maillard reaction on the antioxidant activity of squid peptides were studied.1.The extraction rate of squid protein by salting out method was 42.35%.The pI of squid protein was 4.3 by isoelectric point analysis,gel column chromatography and SDSPAGE analysis,and the molecular weight of squid protein was mainly distributed near 88 KD and 63 KD.2.The effects of various factors on the hydrolysis of trypsin and alkaline protease were studied.It was found that when the amount of trypsin was 5% and the pH was 8,the content of AAN in the hydrolysate reached the maximum at 40? for 3h.Squid peptides were hydrolyzed again with alkaline protease using trypsin hydrolysate as substrate.The optimum hydrolysis conditions of alkaline protease were as follows: when the solution pH was 9,added 3% aminopeptidase,hydrolysis was 2.5h for 55? in constant temperature water bath.The content of AAN in the hydrolysate reached the maximum.The squid polypeptide obtained by trypsin and alkaline protease hydrolysis was called YJMD squid polypeptide,YJMD squid polypeptide with molecular weight less than 31 KD.3.The influencing factors of aminopeptidase after the response surface were optimized.It was found that when the pH was 9.2,added 5% aminopeptidase,hydrolyzed at 70? for 3h,it showed the highest AAN content in the hydrolysate.Squid protein hydrolyzed by aminopeptidase was called ATMD squid polypeptide.The molecular weight of 85.06% ATMD squid polypeptide was between 1355.37D-17 KD and 14.94% of ATMD squid polypeptide was less than 1355.37 D.The content of free amino acids in ATMD squid polypeptide solution was 2.4 times higher than that in YJMD squid polypeptide solution.The essential amino acid content in YJMD squid polypeptide solution was 1.6 times higher than that in YJMD squid polypeptide solution.4.The results of two squid polypeptide Maillard reaction showed that the browning degree of ATMD squid polypeptide was stronger than that of YJMD squid polypeptide.By measuring the free radical scavenging energy and reduction ability of YJMD squid polypeptide,the antioxidant ability of YJMD squid polypeptide was stronger than that of ATMD squid polypeptide,while the antioxidant ability of YJMD squid Maillard polypeptide was lower than that of ATMD squid Maillard polypeptide. |
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