The Effect Of Culture Conditions And Cold Storage On The Flavor Quality Of Swimming Crab(Portunus Trituberculatus)

In this paper,the swimming crab?Portunus trituberculatus?was used as the research object,the nucleotide,free amino acid,lactic acid and volatile odor substances were used as indicators,combined with electronic tongue analysis,electronic nose analysis,Equivalent Umami Concentration?EUC?analysis and key odor substances analysis to studied the effects of cultured salinity on the flavor quality of the crab.At the same time,the flavor quality of the swimming crab,which was fed with the compound feed and traditional chilled fish,was compared.Finally,the changes of flavor quality of the swimming crab in the cold storage process were studied.The research results are as follows:?1?Cultured salinity had an important influence on the flavor quality of swimming crab.The results showed that the total free amino acid?TAA?,essential amino acid?EAA?and flavor amino acid?FAA?content of crab meat were the highest when the salinity was 25psu.The free amino acid content of the salinity group was the highest in30psu,and the glycine,proline and valline had great contribution to the taste og crab meat in various taste amino acids.The taste nucleotide content of 20psu and 30psu were significantly higher than that of the 15psu and 25psu groups.The EUC analysis also showed that the umami taste intensity in crab meat of 20psu and 30psu were higher;the organic acid results showed that the lactic acid content in the meat of the four salinity group was significantly different,including 25psu>30psu>20psu>15psu.The four salinity groups contained 28,27,28,and 28 kinds of fatty acids,total fatty acid?TFA?content in the 15psu group was significantly higher than that in?p<0.05?20psu,25psu groups.Among them,palmitic acid(C₁₆:0),stearic acid(C₁₈:0)and trisuccinic acid(C₂₃:0)oleic acid(C₁₈:1N₉C)eicosapentaenoic acid(C₂₀:5N₃)and docosahexaenoic acid(C₂₂:6NS)had higher percent.Four groups of crab meat contain 41,38,40,36 volatile odorants,mainly were aldehydes,alcohols,esters.?E?-2-octenal,nononal,furfural,1-octene-3-ol is a key odor substance of the swimming crab meat.?2?The flavor quality of the swimming crabs fed with the compound feed was significantly better than that of the traditional chilled fish.In the compound feed group,the total content of nucleotides,the total content of taste nucleotides,the total content of free amino acids and flavor amino acids in the crab meat and ovary were significantly higher?p<0.05?than the traditional culture mode.The TAV?Taste activity valiue?with glutamic acid,alanine and arginine was greater than 1 in each group,which contributed a lot to the overall taste of the swimming crab.Secondly,The TAV of glycine of the ovary in the compound feed group was greater than 1,the traditional feed group was less than 1,and the change of methionine in histidine and crab meat was reversed,revealed that the compound feed culture could enhance the sweet,reduce bitterness of the swimming crab.The EUC in ovary of the compound feed and the traditional feed group were 32.43 gMSG/100g and 26.50 gMSG/100g,respectively,and the difference between the hepatopancreas and crab meat groups was small.It can be clearly seen that the compound feed culture can enhance the umami taste of the swimming crab ovary.The lactic acid content was 491.55 mg/100 g and 363.58 mg/100 g,respectively.A total of 162 volatile odorants were detected in the two groups of crabs,including 49aldehydes,49 ketones,36 alcohols,13 hydrocarbons,and 15 sulfur and nitrogen-containing species.There were many aldehydes and alcohols in the ovary,and the content of each substance in the two groups had no signinificant different.The aldehydes in the hepatopancreas dominated.The proportion of alkane and sulfur and nitrogen-containing substances in the two groups was different.The alkane accounted for the highest in crab meat,especially in the compound feed group,accounting for49.79%,followed by Aldehydes and alcohols account for a relatively high proportion.Based on the results of the electronic tongue and electronic nose,it can be concluded that the overall flavor quality of the swimming crab fed under compound fed was better than that of the traditional chilled fish.?3?According to the changes in the process of nucleotide degradation,it is speculated that there were two main ways of nucleotide degradation in crab meat during cold storage:ATP?ADP?AMP?IMP?Hx?HxR,AMP?AdR,and the ovarian degradation pathway was ATP?ADP?AMP?IMP?Hx.Secondly,the content of nucleotides and free amino acids in the crab meat after death was significantly lower than that in the fresh-lived period?p<0.05?.From the change of umami taste,the MSG equivalent in crab meat was 10.86 gMSG/100g in the fresh period,which was significantly?p<0.05?decrease during the cold storage.In the ovary,the EUC increased first and then decreased,and the highest was on the first day after death,reaching135.85 gMSG/100g.In this study,90 volatile odor substances were isolated and identified in crab meat.The main changes substances in the cold storage were hexanal,octanal,nonanal,furfural and undecalaldehyde,4,4-dimethyl-2-one,6-methyl-5-hepten-2-one,2-nonanone,?S?-2,5-dimethyl-2-hexanol,1-octene-3-ol,cedarol,2,2,4-Trimethyl-3-carboxyisopropyl-pentanoicacid-isobutylester,2-ethyl-furan,2-pentylf-uran,trans-2-2-pentenyl-furan.The trimethylamine in crab meat and ovary increased significantly on the fifth day of cold storage.A dipeptide Ala-Gly and peptide L-Ala-L-Ala-L-Ala were detected in the late cold storage,which was detected for the first time in crab meat.The main component analysis of the electronic tongue and electronic nose showed that the taste of the ovary was not obvious after 1 day of cold storage.After 5 days of cold storage,the difference in taste of crab meat was not obvious.The taste of crab meat did not change significantly in the first three days of cold storage.It began to change on the fourth day.On the 5th and 7th day,the odor profile of crab meat partially overlapped.The difference in odor between the two was not obvious,but it was significantly different from the first 4 days of cold storage.