Research On The Flavor Of Steamed Qinhu Crab And Its Freezing Processing Technology

Qin Lake Duan Crab belongs to a river crab,especially referring to the crab in Qin Lake,Jiangyan District,Taizhou City,Jiangsu Province.On the aspect of industrial demand,in this paper the volatile and non-volatile taste components of steamed Qin Lake Duan Crab were systematically analyzed,the frozen processing technology more suitable for steaming Qin Lake Duan Crab was explored and studied,in order to better ensure the crab taste,to serve the market,and to provide delicious,fresh steamed frozen crabs..The main findings are as follows:(1)The non-volatile taste components and contents,for example,soluble sugar,free amino acid and nucleotide,etc.in the Duan Crab were tested,and the effects of such components on the taste of the Duan Crab meat were explained clearly through the taste active value and umami taste intensity.The soluble sugar in the Duan Crab meat was low in content and the concentration,when the taste active value was only 0.071,that was not related with the crab's taste.In the Duan Crab meat,the total amount of free amino acids inclued was equivalent to 17.22 mg/g crab meat,where arginine(4.23 mg/g),glycine(4.53 mg/g)and alanine(3.64 mg/g)accounted for 72%of the total free amino acids,composing the major amino acid in crab meat.There were 4 kinds of amino acids whose taste active value was more than 1 in the crab meat.They were glutamate(1.37),glycine(3.48),alanine(6.07)and arginine(8.46),respectively.Although the arginine content ranked the second,its taste active value was as high as 8.46 and ranked the first.(2)Extraction was conducted by microwave-assisted extraction and analysis was conducted by gas chromatography-mass spectrometry,when 63 volatile taste materials were detected,including 10 aldehydes,13 ketones,2 furans,11 alcohols and 8 hydrocarbons,etc.Combined with sensory analysis and GC-O,the reasons for the formation of special aroma of Duan Crab was explored,and it was found that the forced meaty smell and astringency were important odor characteristics of fresh Duan Crab meat.In addition to the meat taste,there was a reletively milder grassy and sweet taste,a light earthy and oily taste,and a quite light ammonia smell,where the acidity scarcely existed.The main odor characteristics of fresh crab cream were strong astringency,salted egg yolk and oily smell,where the odor between light and strong was mainly sweet,earthy and grassy smell.Like crab meat,it was quite thin ammonia smell and sourness scarcely existed.The volatile compounds with the highest strength values in steamed Duan Crab meat were trimethylamine(ammonia and fishy smell)and 3-methylthiopropanal(mellow sauce,onion and braised meat smell).(3)The texture characteristics,pH value,water content,volatile base nitrogen content,malondialdehyde content,etc.of the steamed Duan Crab were tested under 3 different freezing conditions(slow freezing,-45? blow freezing,-70? blow freezing),storing temperature and thawing method(microwave thawing,low temperature thawing,steamed thawing).Combined with sensory evaluation,it could be known that when the Duan Crab was steamed,frozen through-70? blow,stored at-45? and thawed by low temperature before eating,higher quality would be obtained.