| Chinese mitten crab(Eriocheir sinensis),also called river crab,was one of the most important aquaculture species in China.Generally,it has high economic value because of its unique flavor and good nutritional quality.However,due to the differences in culture conditions and methods,the quality of river crabs from different eco-environment modes was not identical,but these differences were not well understood.At the same time,with the sustainable and healthy development of the river crab industry,it is urgently required to make people have a deeper understanding of the quality of river crabs,which might provide basic information for the establishment of quality evaluation criteria of river crabs.In addition,river crabs were currently mainly sold in the form of fresh or pre-cooked food products domestically,which limits the sales market of river crabs.Therefore,the research and optimization of deep-processed ready-to-eat crab products can not only improve the added value of river crab products,but also open up a new way for the production,processing and comprehensive utilization of river crab products.Firstly,the nutritive components of three edible tissues(i.e.hepatopancreas,gonads and muscles)of female and male river crabs under four eco-environment modes(i.e.rice-field,lake,Yangtze River and pond)were analyzed and compared.Secondly,the volatile flavor compounds produced by crabs from four different eco-environment modes were qualitatively and quantitatively analyzed by using electronic nose(E-nose)and headspace solid phase microextraction-gas chromatography-mass spectrometry(HS-SPME-GC-MS).Thirdly,retort pouch processed steamed-whole-crab,a type of ready-to-eat(RTE)food,was developed with small sized river crab as raw material.At the same time,the changes of product quality during storage were monitored and the shelf life was predicted.Finally,the traditional drunken crab technology was optimized by reducing its salt content,monitoring the quality changes of low-salt and traditional drunken crabs during storage,and predicting their shelf life.The main results of the present study were summarized as follows:(1)There was no significant difference in the proximate composition among the three edible tissues of crabs from four different eco-environment modes.The protein in the gonads of crabs was the highest,especially in female crabs,and the lipid inthe hepatopancreas of crabs was the lowest.The total amount of minerals in the hepatopancreas of river crabs was the highest,followed by gonads and muscles.Yangtze River crab was rich in copper,and pond crab was rich in iron,while lake female crab was rich in phosphorus.The rule of total amino acid contents in three edible tissues of river crabs was consistent with that of protein,and the quality of amino acid in muscles was the best,and the nutritional value of amino acid in the muscles of Yangtze River crab was the highest.In general,the contents of UFA and PUFA in crab muscles were the highest,followed by gonads and hepatopancreas.Alpha-linolenic acid played a dominant role in the total fatty acids of three edible tissues.The nutritive value of fatty acids in crab muscles and gonads of Yangtze River was the highest,and that of hepatopancreas of lake crab was the highest.(2)Among the three edible tissues of river crabs from four different eco-environment modes,the total volatile components of male crabs from the same eco-environment mode were generally higher than those of female crabs,and the total volatile components of hepatopancreas from the same eco-environment mode were higher than those of muscles and gonads.Aldehydes were the main volatile flavor compounds of river crabs.A total of 57 compounds were detected in crab muscles from four eco-environment modes: 14 aldehydes,5 ketones,5 esters,20 hydrocarbon aromatics,8 alcohols and 5 oxygenous compounds,among which nonanal,decanal and hexadecimal contributed significantly to the aroma profiles of river crab muscles.The flavor of female Yangtze crab muscles was unique,while the others showed certain similarities.A total of 77 compounds were detected in the gonads of river crabs from four eco-environment modes: 23 aldehydes,4 ketones,7esters,32 hydrocarbon aromatics,7 alcohols,and 4 oxygenous compounds,among which nonanal,decanal,hexadecimal and 2-pentanylfuran contributed significantly to the aroma profiles of river crab gonads.The flavor of male crab gonads from rice-field and lake was similar.The flavor of crab gonads from Yangtze River was unique,and the flavor of male crab gonads in Yangtze River was relatively good.A total of 71 compounds were detected in the hepatopancreas of crabs from four eco-environment modes: 22 aldehydes,3 ketones,5 esters,26 hydrocarbon aromatics,8 alcohols and 7oxygenous compounds.Benzaldehyde,benzaldehyde,2-acetaldehyde,nonanal,and2,4-decadienal contributed significantly to the aroma profiles of river crab hepatopancreas.The flavor of Yangtze River crab hepatopancreas and pond female crab hepatopancreas were unique,and the flavor of Yangtze River male crabhepatopancreas was relatively superior.(3)The technological process of retort pouch processed steamed-whole-crab was designed,and the technological process was further optimized by single factor test and orthogonal experiments.The optimum component proportion of broth was determined as 3:1 solid-liquid ratio,2% salt,4:1 salt-sugar ratio,0.0045% freshener,0.06% monosodium glutamate,0.5% green onion,1% garlic,and 1% edible oil.The national and hygienic standards of retort pouch processed steamed-whole-crab were preliminarily developed,and the product was eligible by correlative analysis.During storage at 37?,the pH value and the acrobic bacterial count of retort pouch processed steamed-whole-crab did not exceed the limit value.The sensory score was close to the sensory acceptability limit on the 21 st day,but TVB-N had exceeded the limit value on the 21 st day.Therefore,the shelf life of retort pouch processed steamed-whole-crab was determined to be 18 days.Retort pouch processed steamed-whole-crab produced by this process had qualities such as bright red color and strong natural cooking crab flavor,which had the prospect of good sales in market.(4)Using the acrobic bacterial count as the index,the processing technology of traditional drunken crab was optimized,and the optimum processing technology of low-salt drunken crab was determined as follows: 1)Choosing fresh and alive crabs with clean intestinal tract as raw materials for pickling drunken crabs;2)Sterilizing raw crabs with 75% edible alcohol for 1 hour;3)Pickling drunken crabs with 9% salt content in brine and storing the products at 4?.The national and hygienic standards of low-salt drunken crab were preliminarily developed,and the product was eligible by correlative analysis.During storage,the quality changes of low-salt drunken crab were similar to those of traditional drunken crab,both pH and TVB-N did not exceed the limit value,while the sensory score approached the sensory acceptability limit on the 21 st day,and the change of acrobic bacterial count was consistent with sensory evaluation results.The shelf life of two kinds of drunken crabs was determined to be21 days.The low-salt drunken crab's technology greatly reduces the amount of salt used in pickling,overcomes the shortcomings of traditional drunken crab technology,which relies on adding much salt to prevent microbial nourishment and meat spoilage.The salt content of low-salt drunken crab was only 5.6%,which was lower than that of traditional drunken crab by 29.1%. |
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