Comparison of edible yield, carotenoid content and nutritional composition between the white carapace strain and green carapace strain of adult Eriochier sinensis

Chinese mitten crab (Eriocheir sinensis) is an important aquaculture species in China, with annual culture production of around 800, 000 tons. Although more than 90% of adult E. sinensis have green carapace and limbs, there are a very small percentage of crabs with uncommon carapace color in wild or domesticated populations, including purple, yellow, red and white ones. Color is an important economic trait for customer acceptance and economic value of Chinese mitten crab, making it a potential target trait for the genetic breeding of this species. E. sinensis with white carapace is a new strain introduced by genetic breeding programs, which has several characteristics including heritable white color and fast growth rate. However, it remains unclear how the white strain compares to the normal green strain of adult E. sinensis in total edible yield and nutritional quality. Therefore, juvenile crabs of the two strains were reared in the same pond until the commercial size, and their edible yield, carotenoid content and nutritional composition were compared. The study showed the following. ① There were no significant differences in tissue coefficient, edible yield, and conditional factor between white and green E. sinensis. (P>0.05). ② The lightness (L^*) value in wet and dry samples of the white strain was significantly higher than that of the green strain, but the redness (a ^*) value was significantly lower in the white strain (P>0.05). No significant differences were found in color parameters in hepatopancreas and ovaries (P>0.05). ③ The contents of total carotenoid and astaxanthin in the carapace of the white strain were significantly lower than those of the green strain (P<0.05), but there were no significant differences in hepatopancreas and ovaries between the two strains (P>0.05). ④ There was no significant difference in the content of proximate composition in edible tissue while some differences existed in fatty acid composition between the two strains. The C20:4n6 in the muscle of white females was significantly higher than that of green strain (P<0.05). However, 18:0, 18:2n6 and docosahexaenoic acid (DHA) / eicosapentaenoic acid (EPA) ratios in hepatopancreas of green females were significantly higher than those of white females (P<0.05). ⑤ Irrespective of sex, there were no significant differences in the composition of most amino acids and essential amino acid scores between the two strains (P>0.05), and white females had significantly lower levels of isoleucine and tyrosine in muscle than green females (P<0.05). In conclusion, although the white carapace strain ofE. sinensis had the lower color parameter and carotenoids content in the carapace than the green strain, the two strains had similar level of edible yields, proximate composition, the contents of major carotenoids, fatty acid composition and amino acid contents in their edible tissues, which suggested the white carapace strain of adult E. sinensis has similar nutritional quality with green strain and potential value for the farming industry of this species.