Preparation Of Phosphorylated Trehalose And Its Study On Quality Assurance Of Frozen Shrimp

Litopenaeus vannamei,the scientific name of Litopenaeus vannamei,is a crustacean aquatic product of the prawn family Penaeidae.Because of its unique delicious taste and low-fat high-protein nutritional characteristics,it is very popular among consumers.Frozen storage is widely used as the main storage method for shrimps.In order to reduce the impact on the quality and taste of shrimps during freezing storage,phosphate-based antifreeze agents are widely used in water because of their low price and good antifreeze effect.The antifreeze field of products,but the side effects of the use of such antifreeze agents are increasingly appearing,such as the problem of excessive phosphorus,which has a direct or indirect effect on the quality of shrimp and human health.Therefore,it is necessary to find a new type of low phosphorus effective antifreeze agent to improve the side effects of phosphate.In this experiment,phosphorylation of trehalose was modified to optimize its preparation conditions,and phosphorylated trehalose was prepared to study its effect on the quality characteristics of frozen Penaeus vannamei and explore its low-temperature protection mechanism.The research content is as follows:1.Explore the optimal process parameters for the preparation of phosphorylated trehalose through orthogonal experiments.The optimal phosphorylation conditions are phosphate ratio(sodium tripolyphosphate: sodium trimetaphosphate)6:1,trehalose concentration 6%,reaction Temperature 90 ? and reaction time 7 h.The intensity of phosphorylation conditions on the thawing loss rate of frozen Penaeus vannamei was in order of phosphate ratio=trehalose concentration=reaction temperature>reaction time,and the phosphate content in phosphorylated trehalose was 11.68%.2.To explore the antifreeze protection effect of phosphorylated trehalose on frozen shrimps.The results show that after soaking the phosphorylated trehalose,it can effectively reduce its juice loss rate,and the elastic chewability of shrimps has certain protection.In addition,phosphorylation Trehalose soaking treatment can significantly slow down the decline rate of frozen shrimp myofibrillar protein content,Ca-ATPase activity and total sulfhydryl content,and can inhibit the reduction of ionic bonds,hydrogen bonds and non-disulfide covalent bonds and the increase of hydrophobic bonds.From the microstructural results,the immersion treatment of phosphorylated trehalose can keep the shrimp tissues intact and tightly arranged without deformation;SDS-PAGE electrophoresis results show that phosphorylated trehalose can slow the degradation of shrimp muscle protein to a certain extent.3.Explore the low-temperature protection mechanism of phosphorylated trehalose shrimp.By analyzing the offset distance between pH value and isoelectric point of shrimp whole protein system and myofibrillar protein system,we speculate that pH value can maintain the stability of myofibrillar protein;secondly,explore phosphorylated seaweed from the aspect of frozen shrimp protein functional characteristics The protection mechanism of sugar on myofibrillar protein,and then determine the size and aggregation state of protein molecules by AFM detection and protein particle size distribution.The results showed that the pH value of the shrimp protein system soaked in phosphorylated trehalose deviated far away from its isoelectric point,which was conducive to maintaining the stability of the protein.Secondly,phosphorylated trehalose could effectively inhibit the deterioration of the functional properties of the protein.4.To study the mechanism of phosphorylated trehalose on frozen shrimp protein stability,from mass spectrometry analysis,electrophoresis quality control,protein relative molecular mass distribution,protein isoelectric point distribution,peptide sequence length distribution,peptide sequence coverage,peptide Proteomics analysis was carried out on quantitative distribution,analysis of differential protein GO analysis and KGEE annotation pathway.The results showed that the actin,skeletal actin,myosin heavy chain,myosin light chain and tropomyosin among the differential proteins showed up-regulated expression in the phosphorylated trehalose group,which was important for maintaining tissue structure and muscle Elasticity plays an important role.The analysis of differential protein GO showed that the down-regulated expression of differential protein mainly exists in the non-membrane-bound organelles and cytoplasm of cells.The accumulation of differentialprotein in tricarboxylic acid metabolism process,tricarboxylic acid cycle,transferase activity and citric acid metabolism process is more obvious.Down-regulated expression of protein-like protein will reduce the stability of energy metabolism of shrimp muscle.In the analysis of the KGEE pathway,in the phosphorylated trehalose group and the distilled water group,the differential proteins had 33 up-regulations and 4 down-regulations in the metabolic pathways.The various metabolic pathways involved in these proteins mainly occurred in shrimp muscles,in shrimp processing and The storage process has a greater impact on muscle quality.After the shrimps were frozen,the metabolic pathways of the distilled water group obviously decreased.Compared with the phosphorylated trehalose group,the metabolic pathways were improved,indicating that the metabolic pathways play an important role in maintaining muscle mass during the cold storage of shrimps.The phosphorylated trehalose group has a good anti-freezing protection effect on frozen shrimps.