Study Of Freeze-dried And Ready-to-eat Shrimp (Penaeus Vannamei)

The demand for ready-to-eat convenient food items is rising due to changing lifestyle. Although white shrimps (Penaeus vannamei) are one prawn with the largestharvest in China, its process is still backward. Freeze-dried and RTE shrimp are twoof processing methods that could satisfy the present demand of high-quality productsin the food market and provide new way for the shrimp industry. However, researchabout color and rehydration characteristic changes of freeze-dried shrimp duringstorage is gap. It’s necessary to investigate the mechanism of quality change andimprove it. In order to resolve the problem of short shelf life and bad taste, studyabout key processing technology and quality change of RTE shrimp during storagewas discussed, and new product with long shelf life and good taste was developed. Allthese research would benefit for the development of shrimp industry.Based on the above reason, this paper studied the key processing technologiesand effect of storage time, storage temperature, manner of packing and antioxidant onstorage characteristic of freeze-dried shrimp. Prediction model of shelf life andmechanism of quality change were investigated. Moreover, this paper discussedstorage change of RTE shrimp and developed a new RTE shrimp’s product with longshelf life and high moisture content. Conclusion summarized as follows:1. Freeze-dried shrimps with best rehydrated quality could be obtained using thiscondition: blanched at100℃,1min, rehydrated at60℃for5min. Compositephosphate and algin increased its rehydrated rate and water holding capacity,improved its chewiness. During storage, sensorial acceptability of shrimp decreasebecause of color fading. CIE a value was related with astaxanthin degradation andTBAvalue increase. After long storage, rehydrated shrimp had bad water holdingcapacity and chewiness. CIE a*had the highest Pearson’s coefficient with sensorialacceptability and could be considered as key factor.2. The result indicated that effect of temperature on storage characteristic was obvious. The prediction model could be used to predict shelf life of freeze-dried shrimp atdifferent temperature. Nitrogen-filled and aluminium foil packaging extend shelf lifeobviously. Tea polyphenol had beneficial effect on the storage characteristic offreeze-dried shrimp.3. The rehydration characteristic decrease of freeze-dried shrimp caused by reduce ofwater holding capacity of shrimp meat. This change was caused by two factor: shrimpprotein denaturated further and perssad changed, causing the decrease of salt solubleprotein and water holding capacity; range of muscle fiber and structure of myofibrilwere destroyed. This change of microstructure lead to missing of space that waterexists. The result was that moisture status changed and intermediate water transferredto be free water during storage.4. RTE shrimp that was pickled and sterilized at115℃could be stored at40℃for30d. This way avoided be broken when sterilized at high temperature and pressure.During storage, degradation of protein led to deterioration of microstructure andtexture. Astaxanthin degradation led to color fading.5. Composite phosphate of0.22%, sorbitol of3.12%and glycerol of2.51%werefound to be the optimal condition to obtain the lowest water activity of0.884. Aw ofproducts was reduced, but moisture content kept at high level, maintaining sensorialacceptability of RTE shrimps at a high level. Water-activity-lowering agent reducedAw by means of increasing content of intermediate water and decreasing free watercontent. And this restrained texture and color change of RTE shrimp during storage.