Optimization Of Vacuum Microwave Drying Process And Study On Flavor Composition Changes During Drying Process Of Litopenaeus Vannamei

Litopenaeus vannamei is a large number of shrimp varieties in our country,which is high in protein,low in fat,rich in minerals content and unique in flavor.is a large number of shrimp varieties.Dried shrimps is one of the main processed products of prawns.At present,it is mainly dried by hot air drying.Due to the high temperature of hot air drying and long processing time,the dried shrimp products have some problems such as uneven color,easy cracking of shrimp body and serious loss of nutrients.Vacuum microwave drying is a drying method which combines the advantages of microwave drying and vacuum drying.It has the characteristics of fast drying rate,low energy consumption,fast heat transfer,easy control and strong applicability.In recent years,vacuum microwave drying has been widely used in the field of agricultural products processing,which has the advantages of short time consuming,high efficiency and convenient operation.At present,there are few reports in the field of aquatic products processing.This topic with large farming,achieved as raw material,the vacuum microwave drying,achieved the process parameters,and uses the sensory evaluation,electronic nose and the physical and chemical analysis method for all achieved in the process of dry flavor composition and the change of volatile component content analysis,in order to shore,shrimp dried processing and industrial production to provide scientific basis.The main research contents and results are as follows:1.The sensory evaluation was taken as the main evaluation index,and the sensory evaluation system was established.The effects of loading capacity,heating power and vacuum degree on the drying of Litopenaeus Vannamei were analyzed by the method of orthogonal experiment combined with Modulus and mathematical sensory evaluation,the optimum parameters for vacuum microwave drying of Litopenaeus Vannamei were studied:the best sensory evaluation of different microwave vacuum conditions,the shrimp body center temperature,chewiness were analyzed,the results show that the optimal parameters for shore,prawn vacuum microwave drying with loads of 75g(Shrimp Body mass/effective cavity volume of drying chamber 34cm×32cm×30cm),heating power 400W,0.08MPa,vacuum.There were significant differences in sensory evaluation,central body temperature and masticability of shrimp treated with different vacuum microwave drying parameters.The treatment group with loading capacity of 75g,heating power of 400W and vacuum degree of 0.08MPa had good mastication and high sensory score,and the center temperature of shrimp body tended to be stable.2.Taking the content of flavor components as the index,the change rule of main flavor components during vacuum microwave drying of Litopenaeus vannamei was analyzed by physical and chemical analysis method.The results showed that the flavor components of fresh shrimp changed obviously during the vacuum microwave drying process.With the process of drying,the content of free amino acids in prawn decreased continuously,and the contents of Serine,glycine,tyrosine,glutamic acid,proline and arginine decreased greatly at the end of drying(A₅point,drying for 25min,moisture content of 12.84%).The total amount of flavor nucleotides increased slightly,and the contents of GMP and IMP in umami taste increased significantly,2.98 and 1.87 times,respectively.The total organic acids increased by 2.43 times,the contents of L-hydroxyproline and lactic acid increased by 2.98 and 1.87 times,respectively.The contents of most inorganic ions,glycogen and betaine had little change,while the contents of K⁺and Na⁺increased by 2.24 and 3.56 times,respectively.Taking the traditional hot air drying as a reference,the content of free amino acids in vacuum microwave drying prawn was lower than that in hot air drying prawn,but the content of nucleotides,organic acids and inorganic ions in flavor was significantly higher than that in hot air drying prawn,which indicated that vacuum microwave drying made prawn's fresh,salty and sour taste more full and rich.3.Sensory assessment,electronic nose and GC-MS were used to analyze the variation of volatile components during vacuum microwave drying of Litopenaeus vannamei..The results showed that both sensory evaluation and electronic nose could distinguish the vacuum microwave dried and hot air dried Litopenaeus vannamei significantly.The SPME-GC-MS results showed that the volatile flavor components were complex during the drying process of Litopenaeus vannamei,which mainly included 7 compounds.The number of volatile compounds in Litopenaeus Vannamei during vacuum microwave drying increased from 33 to 42,and the total number of volatile flavor components was 34 after hot air drying.With the process of vacuum microwave drying,the contents of pyrazines,nitrogen-containing compounds and alcohol-phenols increased significantly,increasing by 10.71,9.42 and 4.03 times,respectively.The content of ester compounds decreased by 6.14 times.There were no significant changes in the contents of aldehydes,ketones,hydrocarbons and acids.As a reference to traditional hot air drying,vacuum microwave drying of prawn showed higher levels of alcohol-phenols and esters,but lower levels of pyrazines,nitrogen-containing compounds,aldehydes and ketones,hydrocarbons and acids.These results indicated that the volatile flavor components of Litopenaeus vannamei were gradually enhanced during the vacuum microwave drying process,and the main flavor contributions were nut flavor,roasted flavor,coffee flavor,shrimp flavor,popcorn flavor and flower fruit flavor.Compared with hot air drying,vacuum microwave drying can remove the fishy smell and the bad flavor produced by hydrocarbon compounds.