Flavor Characteristics Of Chinese Mitten Crab(Eriocheir Sinensis) In Gucheng Lake

The Chinese mitten crab(Eriocheir sinensis)is a widespread food in the Changjiang River region,China.Due to its relatively large annual output and consumption rates,the culture and production of the crab is of a great economic importance in region of the Gucheng Lake,Jiangsu Province.In the consumer market,crab muscle,hepatopancreas and gonads are the three edible parts.The same size female crabs price on market are higher than males.Crab consumer market has a distinct sexual orientation.At present,trash fish is the bait which is most commonly utilized in Chinese mitten crab artificial culture.With the increasing production demand,the traditional small trash fish resources have become correspondingly limited.Therefore,an urgent need exists for the study to maintaining or improving the nutrition and flavor quality of crab edible parts.In this study,diet and sex 2×2 factorial design used.From April to December of 2011,experimental crabs were reared in 6 similar intensive crab ponds beside Gaochun county in Jiangsu Province.3 ponds were fed trash fish(MTF),while the other 3 ponds with commercial crab pellet feed(MPF).At the end of November,in each pond,2 male and 2 female crabs of the same size were randomly selected.A total of 24 crabs which consisted of MTF?,MTF?,MPF?and MPF?,6 respectively.This study is divided into 6 parts:1?Effects of sex and diet on crab edible parts fatty acid compositionThe 18 kinds fatty acid was detected in muscle,5 kinds of SFA;25 kinds in hepatopancreas,9 kinds of SFA;22 kinds in gonads,6 kinds of SFA.The 22 kinds in MTF and MPF feed,10 kinds of SFA.Gender differences in muscle was5 kinds of unsaturated fatty acids and C16:0,in hepatopancreas 10 kinds,7 of 18C or more unsaturated fatty acid and C 16:0;gonad differences was 20 kinds.The 8 kinds were high in crab edible parts,C16:0,C18:0,C16:1?C18:1,C18:2,ARA,EPA and DHA.Gender differences,male crab muscle ARA was higher,C16:0 and C18:1 lower than female;male hepatopancreas C16:0 was higher,C18:3,ARA,EPA and DHA lower than female;testis C16:0,C16:1,C18:1,C18:2 and C18:3 was lower,ARA,EPA and DHA higher than ovary.C18:0 and ARA in testis,C16:1 and C18:1 in ovary were enriched.The muscle concentration of ARA in male crabs was higher than those of females,with C16:0 and C18:1 lower.MPF group crab muscle C18:1 and C18:2 were higher than MTF group,DHA lower;hepatopancreas C16:1 higher,ARA,EPA and DHA lower;testis C16:1 and C18:1 higher,ARA,EPA and DHA lower.There were higher C18:2 and lower DHA in the three edible parts of MPF group crab.It was similar with MPF group feed were higher C18:2 and lower DHA than MTF bait.Fatty acid composition in crab edible parts reflected feed fatty acid composition.Analysis SFA:MUFA:PUFA and n-6/n-3,crab muscle quality is better than the gonads,testis superior than ovary,gonads better than hepatopancreas.Crab edible parts fatty acid are good to human health.2?Effects of sex and diet on crab muscle and hepatopancreas amino acid contentThe female crab muscles had an increased amino acid contentin than males,the 13 kinds was greatly influenced by sex,except for Gly,Arg,Val and Pro.Amino acid content of MPF group was higher than MTF group,and the amounts of 10 kinds were significantly affected by feed.Ser,Gly,Thr,Arg,Tyr,Val and Pro remained unaffected.High-protein and high-protein/fat diet can increase muscle protein deposition rate.MPF group male and female crab muscle total amino acid conten were higher than MTF group may be relatedto that MTF bait had lower protein-fat ratio than MPF feed.Sex and diet interaction was significant in hepatopancreas.14 kinds except for Glu,Cys and Pro,MTF male was significantly higher than MTF female,MPF male and MPF female.Feed with fish-origin or higher Met may improve fish hepatopancreas protein content.MTF group male crab hepatopancreas protein was higher than other 3 kinds crab may be related to that MTF bait was fish-origin and higher Met.3?Effects of sex and diet on crab edible parts nitrogenous taste substancesThe 9 nitrogen compounds were with TAV over 1 in crab muscle:betaine,F-Ala,F-Gly,F-Glu,F-Asn,F-Arg,GMP,IMP and AMP.These substances had a major contribution to the sweet and umami tastes of crab muscle.Crab muscle EUC weren't affected by sex.Due to higher F-Ala and betaine,female crab muscle was sweeter than males.The F-Glu and IMP in MPF male crab muscle was significantly improved,resulted higher EUC and an improved umami taste.The content of F-Ala and betaine inthe MPF female crab muscle was considerably reduced,leading to a decrease sweet taste.The 11 nitrogen compounds were with TAV over 1 in crab hepatopancreas:betaine and F-Arg,F-Glu,F-Al,F-Lys,F-Val,F-His,F-Gln,F-Asn and F-Met.These substances had a major contribution to the tastes of crab hepatopancreas.In addition to male crabs hepatopancreas AMP was significantly higher than females,hepatopancreas taste was not significant affected by gender.MPF group crabs F-Ser,F-Gln,F-Thr,F-Arg,F-Pro and total FAAs and GMP,IMP were significantly lower than MTF group.Therefore MPF group crab bitterness from F-Arg and umami by EUC decreased.Lecithin,L-carnitine and AMP of gonads was not significantly different between two diets.Gonads betaine and TMAO of MPF group were higher,GMP and IMP were lower than MTF group.Gonads TMAO was no significantdifference between sex,but testis IMP,GMP,AMP and lethcine was lower,betaine,L-carnitine was higher than ovary.4.Effects of sex and diet on crab muscle and hepatopancreas volatile compoundsThe 37 volatile compounds was detected in crab muscle,including 10 kinds of acid,5 kinds of sulfide and 8 kinds sulfur-nitrogen heterocycles;the 47 kinds in crab hepatopancreas inclding 15 kinds of aldehydes,10 kinds of alcohol.Rich sulfide and sulfur-nitrogen heterocyclic compounds were mainly from nitrogen-containing substances such as amino acids and nucleotides,rich aldehydes and alcohols mainly from lipid oxidation.Hepatopancreas was lipid-rich,while muscle nitrogen-rich but lipid-poor.Muscle and hepatopancreas volatile aroma type related to its nutrition composition.The 11 volatile compounds were with OAV over 1 and 7 kinds were between 0.5-1 in crab muscle.These 18 volatile compounds had a foremost influence on the flavor of crab muscle.In the18 kinds,dimethyl sulfide with shellfish and 2,6-dimethyl pyrazine with roasted nuts in female crab muscle was higher.Methyl mercaptan with meat shallot,dimethyl sulfide with shellfish,DMSO with oyster and trimethylpyrazine with roasted nuts in MPF group crab meat were lower.The total amino acid content of the female crab muscle and Met were higher,the total nucleotide content of MTF group crab muscle was higher.This result showed that muscle volatile substances were echo to muscle nutrients.The 20 kinds of volatile compounds were with OAV over 1 and 4 kinds were between 0.5-1 in crab hepatopancreas.These 24 volatile compounds had a foremost influence on the (?)or of the crab hepatopancreas.In the 24 kinds,nonanal with green incense,hexan(?).at green,cis-4-decenal with green butter and 1-octene-3-ol with mushroom in female crab hepatopancreas were higher.Benzaldehyde with almond,benzene acetaldehyde with floral,methyl-3-butyraldehyde with apple,heptaldehyde with green fishy,heptanol with lignans and octanal with orange in MPF group crab hepatopancreas were higher.PUFA of the female crab was higher,MDA levels of MPF group crab was higher,This result showed that hepatopancreas volatile compounds were echo to its nutrients.5.Effects of sex and diet on crab hepatopancreas and gonad oxidation/antioxidantsHepatopancreas CP and L-CN of MPF group crab was significantly lower,MDA and SOD were significantly higher than the MTF group.Male crab gonads L-CN,GSH,GPx,CAT,and MDH were significantly higher than female crabs.Hepatopancreas SOD was positively correlated with MDA,gonads CAT and GPx were positively correlated with L-CN.Compared with the MTF group,the MPF group crab hepatopancreas and gonads showed a high CP,MDA and SOD.Compared with the female crab ovary,male crab testis showed a low CP,TQ Chol and high L-CN,GSH,CAT and GPx.6.Principal component analysis and cluster analysis of detected dataPrincipal component analysis showed that,EPA,DHA,ARA,C18:0,C18:1,C18:2,crude protein and Met different between two feed caused differences of crab edible parts DHA,ARA,C18:0,C18:1,the total free amino acids,the total volatiles,nonanal,1-octen-3-ol,3-methyl butanal,benzaldehyde,2-acetyl thiazole,2,6,10,15-tetramethyl pentadecane,dimethyl sulfide,2-butanone,3-hydroxy-2-butanone,IMP,betaine,TMAO,MDA,L-carnitine and Met.These substances reflected some relevance between feed nutrition and crab edible parts nutrition and flavor.Cluster analysis showed that there were a clearly visible different of nutrient and flavor between sex and diet.The conclusion can provide reference to in-depth study on the mechanism of crab flavor and the development of Chinese mitten crab farming in Jiangsu province.