Muscle nutrition analysis of four snail species of Viviparidae

The snails of Viviparidae, including Cipangopaludina chinensis, C. cathayensis, Bellamya aeruginosa, B. purificata etc., are commonly known as field snails, and widely distributed in freshwater areas in China. Most of the Viviparidae possess certain economic value, and their meat and shells can be used for edible, medicinal use or as feed for livestock, poultry and aquatic animals. B. aeruginosa and B. purificata are the main raw material of Liuzhou river snails rice noodle. With the rapid development of product and sales of river snails rice noodle, the demand for Bellamya is greatly increased. However, there is limited artificial cultivation of Bellamya. Presently, the freshwater snail species in artificial cultivation mainly include C. chinensis and C. cathayensis. Moreover, the facts are largely unclear that the nutritional differences exist among C. chinensis, C. cathayensis, B. aeruginosa, and B. purificata, and whether C. chinensis and C. cathayensis can be used as the main raw materials for river snails rice noodle replacing B. aeruginosa, and B. purificata. In order to examine the differences of muscle nutritional components and evaluate the nutritional values of four snails of Viviparidae, the national standard methods were adopted to determine the nutrition components in the muscle of C. cahayensis, C. chinensis, B. aeruginosa and B. purificata. The results showed that there were significant differences in moisture, crude protein and crude fat in muscle of four snail species (P<0.05), however, the content of ash was similar among the four snail species (P>0.05). The highest muscle moisture was found in C. chinensis (81.28%), which was significantly higher than those of the other three snail species (P<0.05). C. cathayensis had the highest muscle protein (13.11%), which was significantly higher than those of C. chinensis and B. purificata. The highest muscle fat content was found in B. purificata (1.05%), which was significantly higher than the other three snail species (P<0.05). There were 16 common amino acids in four snail species, including 7 essential amino acids and 2 semi-essential amino acids, of which the first limiting amino acids was methionine. In addition, the contents of umami amino acids of the four snail species were higher than 40%, and the content of glutamate was much higher than the other 15 amino acids. The proportion of essential amino acids to total amino acids (EAA/TAA) in the muscle from all four snail species was more than 33%, of which the EAA/TAA in C. chinensis and B. purificata was more than 35%, which was close to the standard recommended by WHO/FAO model (35.38%). However, the EAAI value of all four snail species was lower, less than 80 points, and the EAAI value of B. purificata was the highest, reaching 74.86. The findings of this study suggested that the muscles of the four snails were rich in nutritional composition and balanced in amino acid proportion, and all of them could provide high quality protein sources. In particular, the content of umami amino acids is rich, which has great value for condiment developing and deep processing. In addition, this study clarified the nutritional composition of four snail species, which can provide a basis for their feed preparation, and can also provide an index for the resident’s daily diet.