Effect Of Water-soluble Precursors On The Formation Of Aroma Compounds In Steamed Chinese Mitten Crab (Eriocheir Sinensis) Abdominal Meat

Chinese mitten crab(Eriocheir sinensis)is a kind of unique freshwater crab in China,it is welcomed by consumer due to its unique flavor quality and rich in nutrients.Many studies have focused on its aroma components and abdominal meat is one of the main edible parts of Eriocheir sinensis.In addition to moisture,19% of the protein content makes the small molecule water-soluble flavor precursor a possible source of its meat aroma with seafood feature.However,the current research on water-soluble precursor is mainly focused on it's contribute to taste,its contribution to aroma components formation is rarely been studied.In this study,the effect of water-soluble precursor on aroma formation was evaluated by removal method.Under the condition with raw material matrix,combined with sensory technology and mass spectrometry identification techniques,possible aroma volatile compounds produced by water-soluble precursor in steamed Chinese mitten crab meat are identified.The conclusions are as follows:(1)Changes of water-soluble flavor precursor content after steaming was determined.The contents of Pro,Gly,Arg and Ala were four main kinds of free amino acids,accounting for more than 80% of the total amount of free amino acids.The total amount of nucleotides decreased significantly.Nucleotides and its degradation products meets the transformation rule: ATP ? ADP ? AMP ? IMP ? HxR ? Hx.The content of reducing sugar in steamed meat is less than the detection limit of 0.25 g / 100 g,it is possible to generate a variety of volatile flavor compounds and their intermediates through the Maillard reaction.The content of thiamine is also significantly decreased after steaming,and meat samples between male and female showed significant differences in content.(2)Three enrichment methods of volatile compounds,solvent extraction-solvent-assisted flavor evaporation(SE-SAFE),microwave-assisted extraction-solvent-assisted flavor evaporation(MAE-SAFE),headspace solid-phase microextraction(HS-SPME),were used to determine the volatile compounds in steamed Chinese mitten crab meat with GC × GC/TOFMS.The results showed that 160 volatile compounds were detected with HS-SPME enrichment method,which were significantly better than that of SE-SAFE method and MAE-SAFE method,which detected 68 compounds and 81 compounds separately.The HS-SPME method was suitable for aldehydes,ketones,oxygen heterocyclic compounds,sulfur-containing and nitrogen-containing compounds enrichment.We set HS-SPME-GC×GC/TOFMS method as the best method for volatile compounds identification.(3)Effect of steaming on the formation of meat aroma was studied by artificial sensory analysis,combined with electronic sensory technique and GC×GC/TOFMS.Overall odor profile changes significantly after steaming,fresh meat with a strong intensity of seafood flavor,accompanied by weak soil flavor,steamed meat perform with a more diverse flavor profile,with a strong meat flavor,strong sweet and mellow flavor and roasted cereal flavor.Principal component analysis and discriminant factor model showed significantly flavor difference in sample before and after steaming.The main volatile compounds in steamed meat are aldehydes,ketones,alcohols and nitrogen-containing sulfur-containing compounds,however,volatile compounds in fresh sample are mainly alcohols,hydrocarbons and ketones.94 volatile compounds were found only in steameded samples,and four kinds of compounds with the largest difference from fresh samples were aldehydes,ketones and nitrogen-containing sulfur-containing compounds and oxygen-containing heterocyclic compounds,which are the main contributors to flavor difference between fresh meat and steamed meat.(4)Effects of the removal of water-soluble flavor precursors on the formation of volatile compounds in crab meat were studied.The optimized process of the water-soluble flavor compound were: extracting at 0? with 12 m L/g of water for 20 min,repeat extract for 3 times.The total nitrogen extraction rate with optimized process was 76.531%.In the artificial sensory level,there was no significant difference between the control group and the removal water-soluble group(DW group)of fresh meat.However,there was significant difference between the DW group and the control group of steamed sample,the meat flavor,sweet flavor,roasted cereal flavor of the DW group was significantly lower than the control group showed a strong sea-like flavor,a completely different overall flavor profile.The lack of water-soluble precursor will result in the meat flavor with aquatic product feature in steamed crab meat no longer exist.Principal component analysis and soft independent modeling classification model showed that meat samples of DW group and the control group were significantly different,fresh samples of male and female showed no significant difference between DW group and the control group,for steamed samples,DW group meat of male and female crab can not be distinguished while the control group meat of male and female crab can be completely distinguished,showing that the removal of the water-soluble flavor precursor resulting in volatile compounds causing differences between male and female steamed meat substances disappear.The rejection rate of the DW group was 100% in the SIMCA model with the control group as the standard.53 volatile compounds were only detected in the control group meat samples.These compounds,which can be produced by water-soluble flavor precursors in the steaming process,are responsible for differences of the overall aroma profile between the DW group and the control group,including 2(3H)-5-heptyl dihydrofuranone,3-thiophene formaldehyde,3-methyl-2-thiophenecarboxaldehyde,trans-2(2-pentenyl)furan,2,5-octanedione,dimethyl disulfide,3-methylthiophene,dimethyltrisulfide,pyrrole,pyridine,2,6-dimethylpyrazine,2-acetyl-3-methylpyrazine,N,N-dibutylacetamide,3-acetyl-2,5-dimethylthiophene,3-methylbutanamide,pyrazine,el.In conclusion,water-soluble flavor precursors-amino acids,nucleotides,reducing sugar,thiamine participate in the formation of crab meat characteristics aroma through steaming process,the relationship between the two locked to the following kinds of volatiles: nitrogen-containing compounds,sulfur-containing compounds,aldehydes and ketones and oxygen-containing heterocyclic compounds.N,N-dibutylacetamide,2,5-octanedione,dimethyl disulfide,2,6-dimethylpyrazine,dimethyltrisulfide and are the main relative compounds.