Study On The Soft-shell Dry Litopenaeus Vannamei

Shrimp Penaeus vannamei is deeply favored by domestic and abroad markets for its fast growth, suitability for intensive cultivation, tender meat and high nutrition value.However, for the benefit of eating, the hard shell of Penaeus vannamei needs to be removed in the process of converting to products, which leads to a series of problems, such as low rate of processed products, and low economic efficiency. Moreover, the shell waste would cause the environmental pollution. In order to make full use of Shrimp Penaeus vannamei, shell softening technology has been adopted on the condition that the flavor of the shrimp will be retained. This technology not only can soften the hard shell, but also can make the rich nutrition substance of the shrimp more easily to be absorbed. Because the above mentioned benefits, shell softening technology has become the new concept of developing the dry shrimp products. In order to achieve this goal, the following researches has been done:(1)The shell softening technology study;(2)Drying technology study of the softened shell;(3)Shelf-life study of the softened shell shrimp. These researches has contributed the following results:(1) With the goal of keeping the Shrimp Penaeus vannamei's shell eatable and with the usage of compound organic acid as the softening agent, and through the study of the decalcification rate, protein loss rate and texture variation law, the best compound organic acid and the best acid softening time has been made out. It shows that when the decalcification rate has reached to 55 percent, the calcium of the shell retains 8.28 percent,and this softened shell is easy to eat; when the volume fraction keeps 5 percent, the compound organic acid made of acetic acid and lactic acid in proportion of 1:1 can achieve the best softening effect with the softening time of 30 minutes. Shrimp Penaeus vannamei in this case is with the loss of 5.53 percent protein, 55. 69 percent decalcification and with satisfying nutrition and flavor;(2) Dry the shell with hot air to 30 percent, with the temperature perspective as 50 degree, 60 degree, 70 degree and 80 degree, then study the drying curve under different temperature, and the influence towards product's contraction percentage, rehydration rate,texture and sensory scores. It shows that though the time is in short need under the high temperature, the quality of product would be damaged under the high temperature, and the phenomenon of volume reduction and back cracking would appear. Then it has been decided that the best hot air temperature is 60 degree and the best drying time is 8 hours,which can retain the quality and shape of the shrimp to the better degree;(3) Do the storage experiment towards the products under the temperature of 30, 35,40 degree perspectively, and evaluate the sensory quality, pH value, colony total number and TVB-N value of the dry softened shrimp in the process of storage. It shows that the sensory quality has great relationship with TVB-N value, which means that the TVB-N value is the key indicator of the quality and shelf life of the softened dry shrimp. By setting the TVB-N value to 18.0mg/100 g as the decision point of the shelf life, constructing dynamic model of the soft shell dry shrimp and adopting the Arrhenius equation, it can be predicted out that under the temperature of 20 degree and 25 degree, the theoretic shelf life of the soft dry shrimp is 153 d and 95 d.