Effects of Feeding Ice Fish and Feed on the Flavor of Chinese Crab
Abstract
Eriocheir sinensis is an important aquaculture animal in China. In order to compare the effects of feeding chilled fish and feed on the flavor of Chinese mitten crab, this experiment compared the volatile flavor substances, sensory evaluation and the differences of amino acids (AA), fatty acids (FA) and nucleotides. As a result, the sweet taste, fresh taste and grass flavor of Chinese chelate crab in the feed group were significantly higher than those in the ice fish group (P<0.05). The fishy smell of the feed group was significantly lower than that of the ice fish group (P<0.05). Amino acids in feed group and chilled fish group were not significantly different. Only 5'-adenosyl monophosphate (AMP) was found to be significantly different between the two groups (P<0.05), and the AMP content in feed group was significantly higher than that in ice fish group. The fatty acid composition of feed group and chilled fish group varied greatly. compared with the chilled fish group, saturated fatty acids (SFAs) and monounsaturated fatty acids (MUFAs) in feed group decreased significantly (P<0.05), while high unsaturated fatty acids (PUFAs) increased significantly (P<0.05). Gas chromatography-mass spectrometry (GC-MS) was used to study volatile small molecules in muscle difference, compared with the ice fish group, the content of aldehydes in the feed group increased significantly (P<0.05), and the content of ketones and nitrogen compounds decreased significantly (P<0.05). The enzyme (lipoxygenase) that catalyzes the formation of aldehydes from polyunsaturated fatty acids was further analyzed. Compared with the ice fish group, the expression of LOX 5 genes and proteins and LOX enzyme activity in the feed group were significantly increased (P<0.05).
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Introduction
Chinese mitten crab (Eriocheir sinensis) is favored by consumers because of its rich nutritional value and unique flavor, and is one of the important economically farmed crabs in China [1,2]. In 2015, the total output of river crabs in China reached about 823,000 tons, most of which came from pond culture [3]. For along time, traditional feeds such as chilled miscellaneous fish, corn, wheat, soybeans and cakes have been mainly used for breeding river crabs in ponds. However, these traditional feeds have some shortcomings such as unstable sources, unbalanced nutrient composition, low feed utilization rate and easy to cause water quality deterioration, which easily lead to the disease of river crabs and unstable quality of adult crabs [4-6]. Traditional breeding mode has become one of the important factors restricting the sustainable development of Chinese crab breeding industry [7,8]. Although the artificial compound feed has been gradually applied to the production of river crabs with the continuous improvement of the culture concept and technical level, in the late stage of culture, especially after the reproductive molting of river crabs, farmers still generally use a large number of Iced fish for fattening [9]. At present, there are two kinds of fattening feed on the market: puffed feed has good stability in water,less anti-nutritional factors in raw materials, which is beneficial to digestion and absorption of aquatic animals, and has the advantages of high utilization rate of raw materials, less pollution, safety and hygiene, etc. The processing of hard pellet feed has low requirements on equipment and relatively low manufacturing cost, and can also avoid oxidation loss of vitamins and fatty acids caused by puffing processing technology [10]. At present, Chinese feed manufacturers mostly adopt the processing technology of hard pellet feed. There are few reports on the effect of feed on the flavor of river crabs. In this experiment, hard pellet feed and Iced fish were used to feed river crabs, and their effects on the flavor of river crabs were compared to provide scientific basis and practical reference for the cultivation and quality control of river crabs.
Conclusion
It was found that the Chinese mitten crab in the feed group had higher sweetness, umami taste and grass fragrance, while the fishy smell was lower than that in the ice fish group. There was no significant difference in AAcomponents between the two groups, but the PUFA ratio of Chinese mitten crab fed with feed increased significantly, while the ratio of SFA and MUFA decreased significantly. In addition, AMP and EDU increased significantly in the feed group. Aldehydes are one of the important factors that can produce unique flavor of Chinese mitten crab. Aldehydes increase significantly after feeding Chinese mitten crab with compound feed, which may be related to the activity of lipoxygenase. Feeding feed can completely replace the traditional Iced fish. Feeding feed is easy to operate and store, and Chinese mitten crab has more flavor. ACKNOWLEDGMENT This research was financially supported by “Qing Lan Project of Jiangsu Province” (〔2018〕12)and “311 Talents Project in Taizhou City” (2017Ш−804), College Students' Innovative Entrepreneurial Training Plan Program (202012806019Y).