| Chinese mitten crab(Eriocheir sinensis),commonly known as river crab,is not only delicious,but also rich in nutrition,so it is widely loved by consumers.The artificial breeding of E.sinensis was realized in the late 1980 s through the technology of artificial preparation of seawater,which made the crab breeding industry step into a new stage after its popularization.Among them,E.sinensis from the Yangtze River has the highest cultivated yield due to its large size,excellent breeding performance and best taste,accounting for more than 90% of the total production of E.sinensis in China.Along with the change of dietary structure,nutrition and quality of food have become the focus of attention of consumers.Therefore,higher requirement is put forward for the quality of E.sinensis.However,at present,there are many brands in the E.sinensis market,and the quality standard evaluation system is not perfect.In order to develop the market specifications and grade standards of commercial E.sinensis as soon as possible,so as to provide more comprehensive information for consumers.Therefore,in this experiment,samples of E.sinensis were collected in the Yangtze River Delta(Shanghai,Suzhou and Taizhou)in September,October and November respectively.The proportion of hepatopanpancreas,gonads and muscles in the edible tissues,the contents of conventional nutrients,free amino acids(FAA)and taste characteristics of the crabs were tested and analyzed in depth,in order to further accumulate basic nutritional data of the E.sinensis,in the hope of providing a scientific reference for the consumption,nutritional evaluation and grading standards of the crab.The main experimental results are as follows:1.Comparison of nutritional quality of female E.sinensis at different market times in Yangtze River DeltaIn order to comprehensively evaluate the nutritional quality of female Chinese mitten crab(Eriocheir sinensis)at different time of market in the Yangtze River Delta region,this study selected female crabs from Shanghai,Suzhou and Taizhou as the research objects,and analyzed the proportion of edible tissue,conventional nutrients,free amino acids and taste characteristics.The results showed that the Condition Factor(CF)of female E.sinensis from Shanghai,Suzhou and Taizhou had no significant change from September to November(P>0.05);The hepatopancreas index(HIS)of female crabs from Shanghai,Suzhou and Taizhou showed a downward trend from September to November.The gonad index(GSI)showed an increasing trend.The meat yield(MY)of female individuals in Shanghai was the highest in November,while that of Suzhou and Taizhou was the highest in September.The moisture content in the gonads of female crabs decreased from September to November.The contents of crude protein and crude lipid in gonad and moisture and crude protein in hepatopancreas were increased.Twenty-one kinds of FAA were detected in the muscle of female crabs.The flavor intensity of sweet and umami amino acids increased from September to November,while the content of bitter amino acids decreased.The results of two-way ANOVA analysis showed that the market time was the main factor affecting the nutritional quality of female crabs in the Yangtze River Delta.2.Comparison of nutritional quality of male E.sinensis at different market times in Yangtze River DeltaIn order to comprehensively evaluate the nutritional quality of male Chinese mitten crab(Eriocheir sinensis)at different time of market in the Yangtze River Delta region,this study selected male crabs from Shanghai,Suzhou and Taizhou as the research objects,and analyzed the proportion of edible tissue,conventional nutrients,free amino acids and taste characteristics.From September to November,the CF of male E.sinensis from Shanghai,Suzhou and Taizhou did not change significantly(P > 0.05);The HSI of Shanghai male crab has been declining,and the HSI in September was significantly higher than that in November(P < 0.05);The HSI of Suzhou male crabs increased significantly first and then decreased significantly(P < 0.05);There was no significant difference in HSI of Taizhou male crabs between September and November(P > 0.05);The GSI of male crabs in Shanghai,Suzhou and Taizhou showed an increasing trend.Male crabs in Shanghai had the highest MY in November,while those in Suzhou and Taizhou both had the highest MY in September.From September to November,the contents of moisture in gonads,crude fat and moisture in hepatopancreas of male crabs in the Yangtze River Delta were decreased.However,the crude protein content in gonads and hepatopancreas showed an increasing trend.Crude protein content in muscle of male crabs was firstly significantly increased and then significantly decreased(P < 0.05).Similarly,a total of 21 FAA were detected in the muscle of male crabs.Sweet and umami intensity values increased from September to November,while bitter intensity values decreased.The market time is the main factor affecting the nutritional quality of male crabs,and the nutritional quality and taste of November are the best.3.Correlation between appearance quality and intrinsic nutritional quality of E.sinensis at different market times in Yangtze River DeltaTo understand the size of Chinese mitten crabs in the Yangtze River Delta region at different market times and the correlation between appearance quality and intrinsic nutritional quality,this study used Pearson correlation analysis to cluster among the indicators.The large-scale size identification of E.sinensis at different time of market in Yangtze River Delta region showed that male and female individuals were mainly M size individuals from September to November.The results of cluster analysis showed that the proportion of edible tissue,the conventional nutrients in the gonads,hepatopanpancreas and muscles,and the free amino acids in the muscles were copolymerized into two groups.Correlation analysis showed that the weight of hepatopancreas,the content of moisture in gonad,moisture and ash in hepatopancreas,the content of moisture in muscle and free amino acids(except ornithine(Orn)and proline(Pro))were positively correlated with CF.However,the contents of HSI,gonad mass,GSI and gonad protein,lipid and ash,protein and lipid in hepatopancreas and protein,lipid and ash in muscle were negatively correlated with individual CF.Therefore,we further found that the nutritional value of Chinese Mitten crab can be preliminarily determined by observing its individual size. |
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