Study On Ono-phosphate Additive Of Frozen Litopenaeus Flesh

In recent years, maricultured Litopenaeus vannamei have developed rapidly in China.The main way of taking the fresh or live sale can not adapt to the condition that the yeild ofshrimp quickly increase. It is very important to keep the freshness of the mariculturedshrimp by frozen storage. The water retention of frozen shrimp products are closely relatedto the water quality. However, the freezing and thawing processes have a profound effecton muscle physicochemical characteristic, such as the bonding-type of water withdraw andthe mobility of water freeze out. This may lead to loss of water holding capacity, which canresult in denaturation of the muscle proteins as well as the nutrient loss. Therefore, how toimprove the water retention of frozen shrimp products and prevent protein freezingdenaturation are always the hot topics of aquatic product processing. The objectives of thisstudy were to select non-phosphate additives, optimize the water-holding process andexplore the mechanism of water retention of Penaeus vannamei, which providing thetheory basis for exploitation of a newtype and safety water-holding agent, in order to solvethe problem of phosphate abuse and ensure the product quality and safety in shrimpprocessing.The research of this paper with Penaeus vannamei as main starting material. In orderto improve the water retention of shrimp frozen, focusing on the development ofno-phosphate, raw material dipping conditions, thawing method,freezing method, and thefrozen storage time. Try to explore the mechanism of water retention of no-phosphate.1. Fractionation of the refined Konjak powder to preparation water retention agent.With six different kinds of enzyme preparation to enzymolysis the refined Konjak powderto preparation different molecular oligosaccharides as water retention agent by hydrolysistime control. Sensory evaluationas, texture properties and water retention rate are the indexto determine the optimal enzyme preparation and hydrolysis time, determinating thereducing-rate by DNS method.The results show that: with hemicellulasee hydrolysis of therefined Konjak powder two hours has good effect of water retention, soak weight increaserate was9.28%, thawing loss down to1.88%, cooking loss rate is17.04%, product yield is 82%, konjac purified powder reduction rate was49%, at the same time improved textureproperties of shrimp, prevent the shrimps become harden and coarse after cooked.2. The screening of better water retaining agent, and the formula of the compound todetermine aquasorb. As an indicator of sensory evaluation, texture and water retentionproperties,conducted a trial comparing with anhydrous sodium acetate,maltodextrin,polyde-xtrose,sodium citrate, trehalose, carboxymethyl chitosan material. The results showed thatsodium citrate, trehalose, and carboxymethyl chitosan have good water retention effect.Then compound the three kinds of water retaining agent that were screened out with konjacenzymatic hydrolyzate. By orthogonal experiment to determine the optimal formula ofsodium citrate6g/L, trehalose4g/L, and carboxymethyl chitosan6g/L. Using theinsurance agent handling, the result is the frozen shrimp thaw weight loss rate of1.49%;heating weight loss rate of21%; production rate of79.01%. By the comparison with theblank control, the non-phosphorus aquasorb has obvious advantage.3. Under different processing conditions, study the hold water quality of the frozenshrimp. Investigated different soaking time (1、1.5、2、2.5、3h), different frozen storagetime (0、20、40、60d), different thawing methods (quietly placed there to thaw at0-5℃,5-10℃, room temperature24℃a nd constant temperature water bath to thaw at35℃) onthe impact of water quality of shrimp respectively. The results showed that soaking1.5hand5-10℃stalling thaw, shrimpshave good water retention, as the frozen storage thelonger the L*value of shrimps was bigger, frozen storage60d shrimp product rate alsoabove the80%.4. The mechanism of phosphate-free water retaining agent to improve the waterretention of frozen shrimp have several possibilities: First, aquasorb get into the shrimp’sinternal by osmosis, using its own expansion to increase the space between the myofibrilsand muscle bundle, and forming the network structure on the space, thereby enhancing thestabilityof the structure. Second, carboxymethyl chitosan, trehalose and konjac glucom-annan oligosaccharides binded with myofibrillar protein, enhance the stability of theprotein and prevent the denaturation of myosin. Third, carboxymethyl chitosan, trehaloseand konjac glucomannan oligosaccharides can absorb and hold large amounts of water andform a gel film on the shrimp surface.