Effects Of High Hydrostatic Pressure And Seaweed Polysaccharide Treatment On Quality Of Freezing White Shrimp Litopenaeus Vannamei

Frozen storage is a preservation method that commonly used in white shrimp Litopenaeus vannamei for long-term storage,whereas shrimp would turn to be dark during frozen storage or defrosting process,which is a hard problem that troubles aquarists of shirmp in china.There are some effective,green and safe methods,for example,thermal processing and nonthermal methods such as high hydrostatic pressure treatment,which are the main physical methods to passivate polyphenol oxidase.In view of this,this current study selected white shrimp Litopenaeus vannamei as the research object to analyze the influence of thermal processing treatment and high hydrostatic pressure treatment on the quality of the white shrimp Litopenaeus vannamei through the determination of the polyphenol antioxidant activity,microorganism,hardness,yield loss etc,and a research on the quality change during freezing storage was conducted.For seaweed polysaccharides has a certain ability of oxidation and water retention,through conducting a study on cooked shrimp that were treated by seaweed polysaccharides during freezing storage quality change,which may provide a method to produce water retention and color protection agents without phosphorus that applied in frozen cooked shrimp.In this paper,the main conclusions are as follows:(1)High hydrostatic pressure treatment have some advantages as follows:compared with thermal processing,the apparent quality of prawns were much closer to that of raw shrimp;It might reduce the loss rate of shrimp;enzyme would be deactivated under the condition of 500 MPa/20 min;The hardness of shrimp changed more obviously when pressure got 300 MPa.thermal processing treatment and high hydrostatic pressure treatment can both have the effect of sterilization.The inactivation of samples with thermal processing treatment experiences a phase from fast to slow:the microbes were quickly inactivated in the early stage and in the later stage,a part of microorganism seem to be more heat-resisting.At same exposure time,the log reduction of total plate count increased with the increasing of power at all pressure level tested high hydrostatic pressure treatment.(2)Though the bacteriological index of frozen shrimp was not out of limit,the apparent quality(texture and color)declined.The results showed that when compared with the control group,the shrimp that holding 10 min and 20 min would be brighter during freezing storage,and water loss rate had decreased when samples were treated at the beginning of storage period.During storage,the hardness of the control samples was on the rise and the treatment groups on the contrary entirely.The springiness changes in controls and the pressure-holding 10 min group experienced a period from increased to decreased,whereas the pressure-holding 5 min and the pressure-holding 20 min group presented a downward trend.TVB-N values of each sample did not exceed 30 mg N/100g.The transversal section of muscle fibers arrangement of controls and the pressure-holding 20 min group increased obviously while pressure-holding 5min and 10min groups were still relatively dense.(3)Generally,cooked shrimps would lose moisture gradually during frozen storage,and after defrosting,exterior lustre of shrimps became dim and taste got poor.During the process of freezing storage,the color of the control group and groups with polysaccharides both dimmed and appeared a fade phenomenon,at the same time,hardness and elasticity were on the decline,among which groups with polysaccharides were better than that of control groups.Though TBA value and TVB-N value appeared a increasing trend,the values were both not out of limit.In addition,myofibril interval got bigger whereas myofibril in groups with polysaccharides didn't break.The total amino acid content of both two groups declined whereas the flavor amino acid of the experimental group with seaweed polysaccharides was higher than that of the control group,which showed that composite seaweed polysaccharides can effectively keep frozen cooked white shrimp Litopenaeus vannamei freshness during preservation.