| Every autumn and winter season,a large number of Chinese mitten crabs are listed,causing a backlog of the market and affecting economic benefits.In order to improve economic efficiency,prolong the length of sales,improve their quality,and hoarding it to achieve support benefits.Therefore,this paper selected the female,Chinese mitten crab(SC(80±5.00 g)?MC(100±5.00 g)?LC(120±5.00 g)),which was small,medium and large in size from December 1,2017 to January 24,2018.They divided into two test groups,by feeding two feeds(combined feed,natural bait),after a period of 56 days of hoarding.Samples were taken every two weeks,and the body meat,hepatopancreas and gonads of the Chinese mitten crabs in the four hoarding stages were selected as experimental materials.Sensory evaluation,conventional quality,fatty acids,free amino acids and taste nucleotides were used as indicators to study the effects of different feeds on the quality of Chinese mitten crabs.The main research contents and results are as follows:1.Effects of two kinds of fodder on sensory and conventional qualities of three sizes of Chinese mitten crab.(1)the body weight increased gradually with the extension of hoarding time,and the most obvious weight gain was SC crab(The weight gain rate of the fourth-stage natural diet group was 14.1%,and that of the formulated diet group was 16.4%.).The weight gain rate of the three sizes of crab was the formulated diet group>natural diet group.(2)With the extension of the hoarding time,the color of Chinese mitten crab is more and more bright,the hardness is getting harder,the color and hardness scores are all LC>MC>SC,and the color score is natural diet group>formulated diet group.There is no relationship between the hardness score and the bait.(3)The three sizes of crab meat and gonadal index reached the maximum in the second stage of hoarding,while the hepatopancreatic index decreased in the second stage,and the body meat and gonadal index were higher than the control group during the maintenance period.In addition,the body meat and gonadal index on formulated diet were higher than natural bait in the second stage.2.Effects of two feeds on the nutritional quality of three sizes of Chinese mitten crab.(1)The three types of crabs in the gonads and hepatopancreas under the two feeds had the highest moisture,protein and crude fat in the second stage of maintenance,and higher than the control group,the moisture and protein in the body meat were the same as the gonads and hepatopancreas.The trend of change was the same,while the crude fat showed a downward trend in the hoarding stage,which was significantly lower than that of the control group(p<0.05);the ash showed a decreasing trend in the hoarding stage;the change between the basic nutrients and the feed was not obvious relationship.(2)The total fatty acid content and EPA+DHA value of the edible parts of the crabs of the three specifications reached the maximum in the second stage of hoarding.Except for the MC gonads,total fatty acid content and EPA+DHA values in MC crab meat and hepatopancreas,SC and LC crab meat,hepatopancreas and gonads were significantly higher than those in the control group.In body meat,in addition to LC crab,SC and MC crabs fed with formulated diet in the second stage of hoarding,the ?3/?6 values were higher than those of natural diets;In the second stage of storage,the value of ?3/?6 in hepatopancreas of LC was less than that in the control group,and the value of ?3/?6 in SC and MC was higher than that in the control group.The ?3/?6 value of LC crabs fed with formulated diet was lower than that of natural diets in the second stage of feeding,and the SC and MC crabs were better for formulated diet.In the gonads,the three sizes of crabs ?3/?6 were significant higher than the ratio of ?3/?6 in the recommended diet of FAO/WHO.In addition to the formulated diet-fed SC.crab,the ?3/?6 value is less than that of natural diet in the second stage of feeding,and the MC and LC crabs are better for formulated diet.3.Effect of two feeds on the taste quality of three sizes of Chinese mitten crabs.(1)After one month of hoarding,the Free Amino acids(FAA)of the three sizes of Chinese mitten crabs in body meat had no significant difference between the hoarding group and the control group.Compared with the control group,FAA in hepatopancreas and gonads of hoarding group were more than three times higher than that of the control group(p<0.05).The total amount of FAA in the three edible crab parts was consistent,and there was no significant difference between the total FAA and the crab size.(2)After one month of feeding,the umami and sweet taste increased,and the changes in the hoarding group were more obvious.The amino acids that contribute significantly to the taste of crab are glutamate(Glu),glycine(Gly),alanine(Ala),arginine(Arg),threonine(Thr),lysine(Lys),Leucine(Leu)and proline(Pro).The number of amino acids with Taste Activity Value(TAV)>1 increased,the TAV value increased significantly,and the TAV value was formulated diet group>natural diet group>control group.(3)After the hoarding,the total amount of nucleotides and the Equivalent Umami Concentration(EUC)in the body meat of the Chinese mitten crabs decreased;The total amount of nucleotides in the hepatopancreas and the EUC were formulated diet group>natural diet group>control group;the EUC value in the gonads increased significantly(p<0.05).Except that the EUC of the MC crab supplemented with formulated diet was lower than the natural diet group,the SC and LC crabs were better in the fresh-keeping effect of the formulated diet.The taste nucleotides have no contribution to the body meat and hepatopancreas of the crab.According to the review,the three sizes of Chinese mitten crabs,which are fed by two kinds of feeds,are in the second stage,that is,the hoarding of Chinese mitten crab for one month has the best quality,and the effect of feeding with formulated diet is better,and the quality has no obvious relationship with the size of crab. |
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