Effects of carrageenan oligosaccharides prepared by electron beam irradiation on frozen shrimps during storage

1% carrageenan oligosaccharide solutions obtained by electron beam irradiation at the radiation doses of 9 kGy (CO-9) and 30 kGy (CO-30) were applied for shrimps before frozen, and their effects on quality of frozen shrimps were investigated by observing the microstructure of shrimp's muscle tissue, measuring their weight loss (%), hardness and pH after thawing. Comparison with the shrimps treated by 1% tetrasodium pyrophosphate solution (Na₄P₂O₇, positive control) and distilled water (negative control), the shrimp samples soaked in CO before frozen kept their initial properties, and the shrimps treated by CO-30 solution showed better quality than others after 3 weeks of frozen storage. Specifically, the mean distances of muscle bundles and muscle fibers in the shrimps soaked in CO-30 solution were 23.9 µm and 11.1 µm, respectively, much smaller than 37.9 µm and 14.8 µm in the shrimps treated by Na₄P₂O₇, and 46.7 µm and 19.8 µm in the shrimps soaked in distilled water only. Our results also revealed that the weight loss after thawing and pH of the shrimps soaked in CO-30 solution were 1.55% and 6.40, much lower than that of the positive control sample (2.59% and 6.82) and negative control sample (4.83% and 6.58), respectively. In contrast, the mean of hardness of the sample soaked in CO-30 solution was 20.4, about 20.7 and 36.0% higher than those of positive control (16.9) and negative control (15.0). These results suggested that CO-30 is effective to inhibit the denaturation of shrimp during frozen storage and can be applied to prolong the shelf life and keep the quality of frozen shrimp products. (author)