The Anti-Freeze And Water-holding Capacity Of Algae Carbohydrate On Litopenaeus Vannamei

Litopenaeus Vannamei has the thin shell, fresh meat, and high content of protein, amino acids and vitamins, but the moisture content reduced, and protein denaturation happened during the frozen storage, when the shrimp treated by thawing or heating, the juice became more, and the texture characters went worse, the appearance became darker, which affecting the quality of products. The aim of this work was evaluate the antifreeze and water holding capacity of trehalose, alginate and its oligosaccharides on Litopenaeus Vannamei, and the anti-frozen effect of algae carbohydrate compound additives was optimized by response surface methodology, and then investigated the mechanism of water retention of algae carbohydrate, which providing the theory basis for the application of a new anti-frozen agent to accelerate the industrial applications of phosphate substitutes and ensure the product quality and safety in shrimp processing.The main research contents and conclusions of this paper are as follows:1. The aim of this part was to evaluate the inhibition of algae carbohydrates on the freeze-denaturation of protein in Litopenaeus vannamei. The results indicated that the thawing loss of shrimp were significantly decreased by trehalose and alginate oligosaccharides treatment after 6 weeks’ storage(-20°C), the L* values of shrimp were also better than others treatment, which indicated the good protective effect on the lightness of the shrimp. In addition, the content of myofibrillar and salt-soluble proteins in shrimp were also decreased in all treated-groups after 6 week’s storage, while the samples treated with trehalose/alginate oligosaccharides were significantly higher than the other groups.2. The aim of this part was to evaluate the antifreeze and water holding capacity of trehalose, alginate and its oligosaccharides on cooked Litopenaeus Vannamei. The results indicated that the defrosting loss rate and the cooking loss rate were significantly decreased by 1% trehalose and alginate oligosaccharides treatment after 6 weeks’ storage(-20℃). The a* values of cooked shrimp were significantly(P<0.05) affected by 0.5%, 1.0% trehalose and alginate oligosaccharides during the whole storage, which indicated their good protective effects on the color of the cooked shrimp. In addition, the moisture content, water activity and texture property were also decreased in all treatments after 6 weeks’ storage, while the samples treated with trehalose and alginate oligosaccharides were better than other groups.3. The aim of this part was to evaluate the mechanism of algae carbohydrates on the anti-freeze and water-holding capacity in Litopenaeus vannamei. The results indicated that the downtrend of total sulfhydryl content and Ca2+-ATPase activity was significantly decreased after 6 weeks’ storage(20 ℃), and the indexes were both higer than other groups. The SDS-PAGE showed that the degradation of protein was decreased by 1.0% trehalose and alginate oligosaccharides treatment, which indicated the good inhibition of protein freeze-denaturation. The microstructure study revealed that shrimp treated by 1.0% trehalose and alginate oligosaccharides, the muscle tissue structure was compact, and had no distortion or no large holes, which indicated the good protection of muscular tissue structure.4. The mechanism of algae carbohydrate was presumed as follows:(i) penetrated into shrimp, swelled and expanded the space of myofibrils or fascicles;(ii) combined with protein and prevented myosin frozen denaturation;(iii) adsorbed and retained entrapped water; formed a film and prevented frozen drip loss.5. In this part the anti-frozen effect of algae carbohydrate compound additives was optimized by response surface methodology(RSM). Experimental factors and their levels were determined by one-factor tests. Subsequently, the Box-Behnken experimental design with 4 factors and 3 levels was performed, and the factors influencing the immersion weight gain rate and defrosting loss rate were estimated by means of regression analysis. The optimum scheme of compound additives was obtained, which the trehalose mass concentration was 0.8%, the alginate oligosaccharide mass concentration was 0.8%, the sodium lactate mass concentration was 0.7%, the sodium citrate mass concentration was 1.2%, and the immersion weight gain rate was 14.62%, the defrosting loss rate was 2.41%, which were almost accorded with the predicted data.