Research On The Key Technologies Of Litopenaeus Vannamei Instant Shrimp Processing

Litopenaeus vannamei is delicious seafood who has rich nutrition, it is not only one ofthe world’s largest yield shrimp species, but also was loved by domestic and foreignconsumers. But the form of shrimp products is single and small amount, the dried product haslow moisture content, poor taste and quality. In order to improve the level of deep processingof shrimp, solve the bottleneck issues that restricting the development of shrimp industry, andmeet the market demand, in this study, the key technologies of instant shrimp processing ofLitopenaeus vannamei were studied, to obtain the instant shrimp products that with highermoisture content, soft texture, good flavor, edible and convenient carried. Mainly includingthe effects of instant shrimp processing conditions on product quality were analyzed, tooptimize the various process parameters; the influence of infrared drying on the productquality was investigated, combined with the optimization of process parameters aboutreducing water activity of instant shrimp, to get the instant products which have high moisturecontent and low water activity, to achieve the purpose of prolonging the shelf life; the sensoryquality, microorganism and physicochemical indexes of instant shrimp during storage wereanalyzed, a dynamic model about the shelf life of instant shrimp was established. Not only theproblems were solved, like improving product quality, prolonging storage period and so on, tomeet consumer demand, to make shrimp resources of Litopenaeus vannamei can be fully used,but also provide theoretical and practical basis for industrial production. The results showedthat:1. The suitable processing conditions of instant shrimp were determined. In this study,the processing conditions of instant shrimp of Litopenaeus vannamei was optimize bysingle-factor test and orthogonal test, also the changes in texture properties, moisture content,salt content and sensory evaluation were acted as analytic indexes. The optimal conditions ofinstant shrimp processing were as follows: after raw materials were cleaned, the material weresteamed5min, dipped in flavoring liquid for1.5h and then dried in infrared oven for35min.The best formulation of flavoring liquid was that the ratio between material and water is1:3,salt2%, sugar3%, cooking wine2%, white vinegar0.2%and monosodium glutamate0.1%for per100g water. And then, vacuum packaging by9.0×104Pa vacuum degree,121℃sterilization15min, natural cooling and finished products. The products have ruddy color, richseafood flavor, moderate resilience and hardness and tastes good which were producedaccording to the above formulation and process technology. The amino acid composition and content of instant shrimp which are processed bydifferent methods were tested by HPLC, and fresh shrimp was used as contrast, amino acidscontent of the shrimps which are processed by various methods have significant increase,and so do the respective processing method of shrimps. Those showed that processingmethods have remarkable effects on amino acid content of instant shrimp. Amino acidcompsition of instant shrimp in different processing methods is fairly complete and has highlevel of eight of the essential amino acid (TEAA) and flavor amino acid (DAA). It illustratedthat the instant shrimp protein is a kind of high quality protein, taste delicious, contains acertain amount of valuable nutrient such as flavor amino acid and functional amino acids, thisproduction can be considered to increasing its comprehensive utilization in the future, it willhas good prospects for market development.2. The effects of infrared drying on the quality of instant shrimp were studied and themathematical model was established. In this experiment, moisture content, water activity,color parameters and texture parameters of instant shrimp treated by different infrared dryingtime were measured and analyzed. The results showed that infrared drying have ansignificantly influence on the moisture content, water activity, color parameters and textureparameters of the instant shrimp. Through the further research and analysis, hardness,resilience, chew and color parameters can be a certain show product quality, correlationanalysis between sensory evaluation scores and texture parameters was carried out, theregression model between sensory evaluation scores and texture parameters is Y（sensoryevaluation scores）=0.260X1（Hardness）+2.800X2（Resilience）+5.425X3（Cohesion）+0.218X（4a*）-10.744，R2=0.972. The feasibility of using hardness, resilience, cohesion and a*valueof color parameter can be objectively used to estimate product quality instead of sensoryevaluation was proved.3. The process parameters of reducing instant shrimp water activity were optimized. Inorder to obtain the instant shrimp with high moisture content and low water activity, toprolonging product storage period, the effect of the applications of constant temperature waterbath oscillator and water activity lowering agent that on product’s water activity was studied,the optimum technological conditions to reduce the water activity of instant shrimp were asfollows: use constant temperature water bath oscillator and water activity lowering agent,shrimp was oscillated for3h, the temperature control in35℃, oscillation speed is120rpm;the optimum formulation of composite water activity lowering agent is:1,2propylene glycol1.95%, glycerol4.58%, and citric acid0.77%; under these conditions, the minimum Aw valueof model predicted was0.875. Use the water activity (Y) of instant shrimp as response value,1,2-propylene glycol (X1), glycerol (X2) and citric acid (X3) as dependent variables, theregression model between the Aw and factors was established, and it isY=0.88+2.500×10-3X1-0.010X2+1.875×10-3X3+0.018X12+0.019X22+0.015X32-3.250×10-3X1X2-2.250×10-3X1X3+7.500×10-3X2X3，R2=0.9940. Through the verification testing, under the optimal conditions for constant temperature water bath oscillator, the actual Aw value measured is0.879. The actual test value and the model prediction value are consistent, which shows that the model can better predict the effect of composite water activity lowering agent on Aw of instant shrimp.4. Vacuum-packaged instant shrimp stored at25,35and40℃were studied in the current study. Sensory evaluation, pH, moisture content, water activity, hardness, elasticity, chewiness, color, total volatile base nitrogen (TVB-N) and the total number of colonies were investigated during storage. The results showed that the higher storage temperature, the quality of instant shrimp decrease faster, and a shorter shelf life. The shelf lives of instant shrimp stored at25℃35℃and40℃were110,56and35days, respectively.5. The first order kinetic equation between TVB-N and storage time (t) is Shelf life dynamics prediction model of instant shrimp is on the basis of this model, the theoretical value of instant shrimp shelf life can be predicted, with the known conditions of storage temperature, TVB-N value of the final and initial storage period, respectively.