Effect Of Free Amino Acids On The Formation Of Aroma Compounds Derived From Chinese Mitten Crab(Eriocheir Sinensis)Meat

Chinese mittern crab(Eriocheir sinensis)is known as river crab,which is a unique crab living in freshwater environment in China.The area along the Yangtze River from Chongming to the eastern part of Hubei has a large output.It is abundant from Chongming in the Yangtze Estuary to the eastern part of Hubei Province.It is one of the major economic crabs in the world.The edible parts of crustacean aquatic animals include crab meat and edible viscera.Crab meat represents foot forceps and body meat.It has unique aroma and rich nutrition.Many scholars have studied the volatile odors of Eriocheir sinensis.However,there are many studies on the flavor of free amino acids,but few on the volatile flavor.In order to study the effect of free amino acids on the formation of aroma compounds derived from Chinese mitten crab(Eriocheir sinensis)meat.In this paper,the soluble flavor compunds of crab meat were detective,and the free amino acids were selected as the research objects.With retaining raw materials' cooking condition,free amino acids in crab meat were extracted.The aroma of free amino acids was studied by sensory technology,electronic sensory and HS-SPME-GC-MS.The results are as follows:(1)The content of flavor precursors in crab meat of male and female was determined.The content of sugar was not be detected,which may be involved in Maillard reaction,resulting in a variety of volatile flavors and intermediates;Thiamine content decreased significantly and fat content increased significantly.The nucleotide content of crab meat decreased significantly.The total amount of amino acids decreased significantly after ripening.Proline,glycine,arginine and alanine are the four amino acids with higher content before and after ripening.(2)The extraction process of free amino acids was optimized.The effect of ultrasonic extraction assisted by trichloroacetic acid and ethanol was compared,and the content of free amino acid was determined.The results showed that ethanol could replace trichloroacetic acid for extraction.The optimum level of male crab was determined to be 1:30(g/m L),3,7 min,40 ?,200 W.Under these conditions,the actual extraction yield of free amino acids for male crab was(26.227 ± 0.244)mg/g.The optimum level of female crab was determined to be 1:40(g/m L),2,5 min,20 ?,200 W.Under these conditions,the actual extraction yield of free amino acids for female crab was(25.101 ± 0.135)mg/g.(3)The extracts of free amino acids were divided into three groups by ion exchange method,which were filtration group(p H less than 2.0),acidic group(p H between 2.0 and 7.0)and alkaline group(p H greater than 7.0).The effects of free amino acid extracts from different p H ranges on crab meat odor were investigated.the fraction of the filter group for fishy smell was lower than that of the acidic group;the meat flavor was strong in the medium-acidic group and the filter group was the weakest;the acidic group and the filter group had more obvious roast odor,while the alkaline group had weaker odor;the oil odor of the three groups was weak.Through SPME-GC-MS analysis,30 kinds of volatile substances were detected in the filtration group,37 kinds of volatile substances were detected in the acidic group and 37 kinds of volatile substances were detected in the alkaline group.