Abstract:

The aim of this work was to evaluate the cryoprotective effects and water-holding capacities of trehalose,
alginate and agal oligosaccharides on cooked white shrimp (Litopenaeus vannamei) during frozen storage using sodium
pyrophosphate as the positive control. The results indicated that the thawing and cooking loss of shrimp were significantly
(P < 0.05) decreased by trehalose and alginate-derived oligosaccharides treatments both at 1.0 g/100 mL after 6 weeks
of storage (−18 ℃), showing no significant difference when compared with sodium pyrophosphate treatment at the same
concentration. The a* value of cooked shrimp was maintained significantly (P < 0.05) better by 0.5 and 1.0 g/100 mL
trehalose and alginate-derived oligosaccharides during the whole frozen storage, which indicated that the two saccharides
had good cryoprotective effects on the color of cooked shrimp. In addition, the moisture content, water activity and texture
of cooked shrimp in all treatments gradually fell during 6-week frozen storage, while the moisture and texture properties
of samples treated with trehalose and alginate oligosaccharides were better than those of the other groups, and significantly
higher than those of the distilled water and sodium pyrophosphate treatment (P < 0.05). The microstructure analysis revealed
that the tissue structure of shrimps treated with 1.0 g/100 mL alginate oligosaccharides were compact, and showed no
distortion. Meanwhile there were no large holes on the cross-section, indicating that alginate oligosaccharides restrained ice
crystal growth and completely kept the muscular tissue structure. This study can lay the foundation for developing a safe,
natural and harmless non-phosphate additive suitable for the frozen cooked shrimp.

Key words: Litopenaeus vannamei, cooked, antifreeze, water retention, trehalose, alginate, alginate oligosaccharides