| In early October2009,1080pond-reared female mitten crab (75-85g) and720males(105-115g) were respectively selected and randomly stocked into six small outdoor earthponds (Length×Width×Depth=8m×8m×1.5m) at a density of120and80crabs per pond. After42days feeding with the formulated diet or trash fish for mitten crabs, the following criterias，including hepatosomatic index (HSI), gonadosomatic index (GSI), muscular index (MI),proximate composition, total collagen content, free amino acids, fatty acids and sensoryevaluation, were used to evaluate the nutritional quality for fattening crabs.The results showed that both the trash fish treatment (TF) and Huayi formulated diettreatment (HY) improve the higher HSI, GSI and MI compared to the original crabs.Irrespective of the dietary treatment, the MI of males (25%) was higher than that of females(22%), while the total edible yield of the male crabs was lower than that of the females(P<0.05). The proximate composition of all genders fed different diets were similar (P>0.05).The tissues of males had higher water content but lower lipid compared to femalesindependent of dietary treatments. There was no significant difference on the total collagencontent in the muscle for dietary treatments and genders (P>0.05), with the range of0.23%to0.30%wet weight. there was no significant difference on the total collagen content in thehepatopancreas (0.32-0.35%) between both dietary treatments (P>0.05), while the collagencontent in ovary is dramatically higher than that in testis (P<0.05).19kinds of free aminoacids in the extracts from the muscle of Eriocheir sinensis were found, total content was16.1mg/g (wet weight). The total free amino acids in hepatopancreas, ovary and testis is14.4mg/g,9.6mg/g and7.3mg/g respectively. Diets had no significant effects on freeamino acid content of the meat, hepatopancreas and gonad, while gender significantlyaffected the contents of some amino acids. The total free amino acid content ofhepatopancreas is significantly higher than that of gonad (P<0.05) and that of female is highertoo (P<0.05). The dominant saturated fatty acids of meat were palmitic (16:0) and stearic(18:0), while oleic acid (18:1n9) prevailed among monounsaturated fatty acids (MUFA). The PUFAs were the principal class of fatty acids in the meat and varied between42.9%-46.2%.The dominant saturated fatty acids of hepatopancreas were palmitic (16:0) while palmiticoleic acid (16:1n7) prevailed among monounsaturated fatty acids (MUFA). The MUFAs werethe principal class of fatty acids and varied between45.4%-47.6%. The dominant saturatedfatty acids of gonad were palmitic (16:0) and stearic (18:0), while oleic acid (18:1n9) andpalmitic oleic acid (16:1n7) prevailed among monounsaturated fatty acids (MUFA). TheMUFAs were the principal class of fatty acids of ovary and varied about50%. For crabs fedboth diets TF and HY, male crabs had significantly higher20:4n-6,∑PUFA,∑n-6PUFA andARA/EPA and lower n-3/n-6in the meat than the female crabs (P<0.05). The hepatopancreasand gonad of males had significantly higher DHA,∑HUFA,∑n-3PUFA contents as well asDHA/EPA, n-3/n-6value compared with those of females (P<0.05). According to fullness,shell color, texture, aroma and sweet umami taste, the crabs from both treatments weresubjected to the sensory evaluation via the consumer panel. Except for female fullness, therewere no significant dietary effects on a range of sensory traits evaluated by panelists, neitherin female nor in male crabs.In conclusion, the results indicated that the formulated diet developed by our laboratory couldbe used to totally replace the trash fish for fattening empty mitten crab without affecting meat,hepatopancreas and gonad quality. Various indices measured in the present study also suggestthat the edible parts of Chinese mitten crab are good for human health and also suitable forprocessing into different crab products. |
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