Effects Of Dietary Replacement Of Fish Oil By Vegetable Oil On The Quality Of Chinese Mitten Crab(Eriocheir Sinensis)

Chinese mitten crab(Eriocheir sinensis)is one of the unique economically farmed crabs in China.It is popular for its high nutritionl value and delicious flavor.The production of farmed crabs in China has increased steadily in recent years.With the development of the times,people have been improving the quality of Chinese mitten crab,not only demanding high nutritional value,but also pursuing the delicious flavor.This experiment is based on the previous research of our research group,using mixed vegetable oil(soy oil: rapeseed oil = 3: 1,W / W)to replace fish oil in fattening feeds,and formulating a whole fish oil feed(F1),50% vegetable oil instead of fish oil feed(F2)and whole vegetable oil feed(F3).These three kinds of feeds with equal fats and nitrogen were fed to female Chinese mitten crab 70 days.After 70 days,the effects of dietary replacement of fish oil by vegetable oil on the quality of Chinese Mitten Crab were studied.First,sensory evaluation was performed,and the basic nutritional components and color of the main edible parts(body meat,gonads,hepatopancreas)were analyzed to determine the feasibility of this experiment.Then,fatty acids composition in each feeds and edible parts were analyzed.Then electronic nose and gas chromatography-mass spectrometer-olfactometry method were used to analyze the odor substances in feeds and edible parts.Finally,using free amino acids and nucleotides as indicators,electronic tongue technology was combined to explore the the effects on taste in edible parts of Chinese mitten crab.Through the analysis and discussion,the most suitable proportion of vegetable oil to replace fish oil was determined,in order to provide a theoretical basis for the scientific cultivation of Chinese mitten crab and to improve the quality of Chinese mitten crab.The specific results are as follows:(1)The results of sensory evaluation showed that using 50% vegetable oil instead of fish oil feed(F2)can reduce the earthy smell of edible parts of Chinese mitten crab and enhance the flavor of meat;Umami and sweetness was also enhanced to varying degrees.The sensory officials had the best overall love for this group of crabs,and the crab shells have the highest hardness;There was no significant difference in the basic nutritional composition of the gonads of the three groups of crabs.Using 50% vegetable oil instead of fish oil feed could increase the crude protein content of the hepatopancreas,while using whole vegetable oil feed(F3)would reduce the crude protein content of body meat;There were differences in the overall color of the three groups of crabs,and the overall color sensory score of the F2 group was the highest.There are also differences in the color of meat,gonads and hepatopancreas.The color of each edible part of the F2 group was more similar to that of the F1 group.(2)The fatty acid composition of the three groups of feeds was different.With the increase of the proportion of vegetable oil in feeds,the contents of Σ MUFA,linoleic acid and linolenic acid and Σ n-6 PUFA were gradually increased,and the contents of Σ SFA,EPA,DHA and Σ n-3 PUFA were gradually decreased;Fatty acids in meat were not significantly affected by the replacement of fish oil with vegetable oil in feeds.Polyunsaturated fatty acids(PUFA)accounted for about 50% in meat,and their contents were not significantly different(P > 0.05);The content of linoleic acid,linolenic acid and n-6 PUFA in the gonads increased with the increase of the level of vegetable oil instead of fish oil in the feeds,which was consistent with the law in the feeds;The hepatopancreas were most affected by the replacement of fish oil with vegetable oil in the feeds,and the contents of Σ MUFA and Σ PUFA were both increased with the increase of vegetable oil replacement level;The meat,gonads and hepatopancreas of F2 group had higher EPA + DHA contents and better fatty acid composition.The use of 50% vegetable oil instead of fish oil feed had a positive effect on the fatty acid composition of the edible parts of Chinese mitten crab.(3)The electronic nose could effectively distinguish the overall odor profiles of 3 groups of feeds and 3 groups of meat,gonads,hepatopancreas.And compared with the F3 group,the odor profiles of the feed and the edible parts of the F2 group were closer to the F1 group;The kinds of volatile substances detected in hepatopancreas were more than that of meat and gonads.Compared with the other two groups,the number of volatile substances kinds in the feed and edible parts of the F2 group were larger;Substances with OAV > 0.1 are mainly aldehydes,while benzaldehyde,nonanal,and decanal are the main odor substances in common,showing mushroom,milky,and raw crab flavor respectively.Their scent intensity values were highest in hepatopancreas;Using 50% vegetable oil instead of fish oil feed could increase the odor intensity of odorous substances with pleasant odor of hepatopancreas,and weaken the odor intensity of odorous substances with unpleasant odor.But the use of the whole vegetable oil feed increased the trimethylamine content in the edible parts.(4)The taste profiles of gonads and hepatopancreas of the three groups of Chinese mitten crab could be well distinguished by the electronic tongue,while the taste profiles of the M-F1 and M-F2 had overlapping parts;The 50% vegetable oil instead of fish oil feed could increase the umami and sweet amino acids of the gonads,hepatopancreas,and increase the EUC of three edible parts,that is the umami was enhanced;The use of whole vegetable oil feed had a certain negative impact on the taste of meat and hepatopancreas.In summary,the use of 50% vegetable oil instead of fish oil feed in the fattening stage not only improved the quality of female Chinese mitten crab,but also reduced the cost of breeding for farmers,which was beneficial to the development of the breeding industry.