Experimental Study On Controlled Freezing-point Storage And Numerical Simulation Of Sous Vide Cooked Penaeus Vannamei

The Penaeus vannamei has a high nutritional value,and its production is huge in China,and it has been deeply loved by people.However,P.vannamei is highly susceptible to spoilage and severely affects the sale and circulation of products.As people's requirements for food safety and flavor are getting higher and higher,it is extremely important to find a suitable treatment method for P.vannamei.Sous vide is a method of cooking in vacuumized plastic pouches at precisely controlled temperatures.Compared with traditional cooking methods,vacuum packaging and cooking at a constant temperature not only prolong the storage period of the food,but also increase the flavor and nutrition of the food.The focus of this paper will be developed in two ways: on the one hand,a three-dimensional numerical model was established for cylindrical P.vannamei to simulate the time which required for the center temperature of P.vannamei to reach the set temperature,and the accuracy of the model was verified by experiments.On the other hand,the optimum temperature and time combination of sous vide cooked P.vannamei was studied,and the effects of ice-temperature vacuum dehydration,salt addition and ice-temperature storage on sous vide cooked were studied.The main results in this paper as follows:(1)The three-dimensional heat transfer model of constant temperature heating of P.vannamei was established to perform three-dimensional unsteady numerical simulation.The temperature rising characteristics of the P.vannamei heating process were obtained by analyzing the temperature field when heated at 70 °C.When the heating time reaches 450 s,the internal and external temperature of P.vannamei is basically same,and it is infinitely close to the set value,the heating simulation ends.The P.vannamei heating experiment was carried out in the actual super constanttemperature bath,the experimental results were analyzed and the accuracy of the model was verified.The relative errors between the experimental values and the simulated values of the heating time at which the P.vannamei center temperature reached the set value at three temperatures of 60°C,70°C and 80°C were found to be 6.5%,4.2% and5.1%,respectively.The results show that the model has certain accuracy.(2)The quality of sous vide cooked P.vannamei in nine treatment groups was studied by heating in 60°C,70°C and 80 °C water baths for 15 min,20min and 25 min respectively.The experimental results showed that the total plate count in all treatment groups was not detected.The higher the cooking temperature,the longer the cooking time,the greater the cooking loss and TBA value.PH values of all treatment groups were around 6.4.The coupling effect of cooking temperature and cooking time determines the color and texture characteristics of the P.vannamei,According to the comprehensive consideration of quality indicators,the optimum temperature and time combination is selected by heating in a 70°C water bath for 20 min.(3)In order to prolong the storage period of sous vide cooked P.vannamei,two groups of P.vannamei were subjected to controlled freezing-point storage experiments,namely fresh P.vannamei SV treatment group(group B)and dehydrated P.vannamei SV treatment group(group BT),at the same time,the corresponding cold storage control group,namely fresh P.vannamei SV treatment group(group A)and dehydrated P.vannamei SV treatment group(AT group)were set up.The sensory evaluation,total plate count,p H value,drip loss,TBA value,color,texture were measured during storage period,and the quality changes of P.vannamei during storage were analyzed.The results showed that the microbial content of the four groups of P.vannamei was very low(1.1?2.7lg cfu/g),and the lightness,TBA content,cohesiveness and drip loss rate fluctuated less.Hardness,springiness and chewiness first increased and then decreased,p H and yellowness increased slowly,redness decreased,the sensory spoilage preceded microbiological and physical chemical spoilage.The best quality of P.vannamei was achieved by the ice temperature vacuum dehydration,SV and controlled freezing-point storage and the storage period was 52 d.(4)In order to prolong the storage period of sous vide cooked P.vannamei.The sous vide cooked P.vannamei which were marinated in 2% salt solution for 8 h,then stored at ice temperature.The changes in quality of P.vannamei during storage wereanalyzed by the sensory evaluation,total plate count,p H value,drip loss,TBA value,color,texture.The results showed that the marinated P.vannamei maintained better freshness and higher sensory scores and longer storage time than the control group.Pickling can slow down the increase of microbial quantity and TBA value,reduce the rate of drip loss,reduce the lightness of P.vannamei,inhibit the decline rate of the redness of P.vannamei,and increase the hardness,chewiness and cohesiveness of P.vannamei.After salting,and then sous vide cooking,the quality of the P.vannamei stored at ice temperature is better,and its storage period is extended by 6 days,its storage period is 40 d.(5)The storage period of P.vannamei was studied after adding salt,dehydrating,sous vide cooking and controlled freezing-point storage.The changes in quality of P.vannamei during storage were analyzed by the sensory evaluation,total plate count,p H value,drip loss,TBA value,color,texture.This treatment may very well inhibit microbial growth.There were no relevant changes in p H value,drip loss,TBA value,color associated with cooked P.vannamei spoilage,texture data were contradictory.the smell and flavor of the P.vannamei are severely lost,the softness is moderate,and the chewiness is lost.No acidification,putrefaction or relevant rancidity was detected.The sensory spoilage preceded microbiological and physical-chemical spoilage,the storage period of P.vannamei is 64 d.