| The research object of this paper is crab sauce which have been fermented from fresh crab.Flavor of the crab sauce was analyzed and the key flavor active compounds were identified.The main research contents and results are as follows:The proximate composition of the soldier crab was researched and its nutritional value was evaluated.Crab meat was medium in protein content,lower in fat content and higher in mineral composition.It was an ideal food source.Among the amino acid composition of protein,glutamic acid content was the highest(204 mg/g),followed by glycine(162 mg/g),aspartic acid(100 mg/g),lysine(87 mg/g),leucine(87 mg/g)and alanine(82 mg/g).The contents of methionine,histidine,serine and cysteine were lowest.Tryptophan and methionine were the first and second limiting amino acids.In addition to tryptophan and methionine,the composition of other amino acids were very reasonable.So soldier crab was high-quality protein raw materials.Among the 28 fatty acids which have been identified,the content of unsaturated fatty acid(35.88%)was the highest.The main fatty acid composition were DHA,EPA,palmitic acid,stearic acid and oleic acid.The ratio of n-3 unsaturated fatty acids to n-6 unsaturated fatty acids was 3.1,closing to ideal value(4).So this crab was food source which rich in n-3 polyunsaturated fatty acids.The non-volatile flavor substances of soldier crab were researched and evaluate the main flavor substances and flavor contribution of crab by TAV.The total free amino acid in crab meat is 1620 mg/100 g.The highest content of this five free amino acids in soldier crab were:arginine(655.5 mg/100g),glycine(mg/100g),proline(111.8 mg/100g),histidine(mg/100g)and alanine(90.9 mg/100g).These five kinds of amino acids have important contribution to the taste of crab meat.Other free amino acids had no direct effect on the taste of crab meat.The highest content of flavor nucleotides in crab meat was IMP,followed by AMP(38.4 mg/100g)and GMP(29.1 mg/100g).The TAV of IMP and GMP were greater than 1.So they were the direct contributor to the taste of crab meat.The synergistic effect between amino acid and nucleotide was evaluated by EUC methods.The results showed that the EUC of crab wss 6.4 g MSG/100 g.This means that the umami intensity of per 100g crab meat is equivalent to the flavor produced by 100g monosodium glutamate.It explained that the reason of the umami taste of soldier crab meat was very intense.The quality index of crab sauce was studied.The total nitrogen content of crab sauce was 1.86 g/lO0mL.The amino acid nitrogen content of crab sauce was 0.88 g/100mL.These two key index all satisfy the standards of other similar products.The microbial index and heavy metal content of crab sauce also satisfy the government standard.The non-volatile flavor substances of crab sauce were researched and determined the key taste-active compounds by TAV and sensory analysis.The total free amino acid content of crab sauce was 3479 mg/100 mL.Compared with total free amino acid of fresh crab meat,the total free amino acids after fermentation was 2.2 times as much as amino acids before fermentation.Among these free amino acids,glutamic acid content(758.7 mg/100mL)was the highest,followed by glycine(422.9 mg/100mL),aspartic acid(mg/100mL),alanine(340.9 mg/100mL)and arginine(301.3 mg/100mL).In terms of taste intensity,the TAV of glutamic acid(25.29),arginine(6.13),alanine(5.68),lysine(5.18),histidine(4.96),aspartic acid(4.02),glycine(3.25),methionine(1.88)and valine(1.45)were both greater than 1.These materials had a direct impact on the taste of crab sauce.The IPM and GMP content of crab sauce were 29.7 mg/100 mL and 49.1 mg/100 mL,respectively.The TAV of IPM and GMP were 1.2 and 3.9,respectively.So the they were the direct contribution to the taste of crab sauce.EUC of crab sauce was 19.3 g MSG/100 g.It was much higher than the value of fresh crab(6.4 g MSG/100 g).Through the omission test and addition test,the key taste-active compounds were conformed,which were Asp,Glu,Gly,Ala,Lys,His,IMP,GMP,Na+,K+,Cl-,Ser,Ile,and Val.The volatile flavor substances of crab sauce were researched and determined the key odor-active compounds by Detection frequency method(FD)and aroma extraction dilution analysis(AEDA).Then this paper use the OVA to verify the conclusion.The main characteristic flavor of crab sauce was seafood flavor,followed by crab meat flavor,umami,ammoniacal flavor,pickled flavor,flavor and grilled flavor.There were 57 kinds of volatile compounds which have been identified,including 9 kinds of aldehydes,8 kinds of ketones,8 kinds of esters,9 kinds of alcohols,5 kinds of nitrogen compounds,8 kinds of sulfur compounds,2 kinds of acids,7 kinds of hydrocarbons,and 1 other classes.There were also 37 kinds of odor active substances which have been identified by GC-O.They have different degrees of contribution to seafood flavor,fishy smell,meat flavor and grilled flavor of crab sauce.The compounds which DF were greater than 7 were Trimethylamine,2,5-Dimethyl Pyrazine,Methyl sulfide,2,3-Butanedione,2-Methylbutyraldehyde and other unknown compounds.They are most likely to have an important contribution to the crab suace.There were 7 active flavor substances which have been identified by aroma extraction dilution analysis,including 2,3-Butanedione,2,5-Dimethyl Pyrazine,1-Octen-3-O1,2-Acetylthiazole,Trimethylamine,Methyl sulfide and 2-Methylthiophene.The result of OAV showed that trimethylamine had the highest odor active value.So it had the greatest contribution to the flavor of crab sauce.In addition,the OAV of 2,3-Butanedione,1-Octen-3-O1,2-Acetylthiazole,and Dimethyl trisulfide were both greater than 1.So these four substances also wer the direct contributor the flavor of crab sauce.2,3-Butanedione,Trimethylamine and Methyl sulfide were found to significantly enhance the intensity of the umami aftertaste by sensory evaluation. |
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