| In the aquaculture industry,due to high-density intensive farming and feeding of artificial compound feeds,the aquatic products are thick and have a strong fishy smell,as well as poor taste.At present,starvation and aquaculture with flowing water are often used to improve the quality of fish meat,but they are all relatively extensive.In order to obtain better parameters for improving the quality of fish under controllable conditions,we designed a set of indoor circulating water aquaculture track for this research work.Triploid crucian carp was bred by the combination of cell engineering technology and sexual hybridization.And it was created by a research group headed by academician Liu Yun of life sciences school of Hunan Normal University.With the advantages of fast growth,omnivorous,strong feeding power,easy fishing and so on,it is widely cultivated in China’s aquaculture industry.However,due to high-density intensive culture,triploid crucian carp has thick abdomen,heavy fishy smell and poor taste.Therefore,we chose triploid crucian carp as the experimental object to study how to improve the muscle quality and increase economic benefits through the self-designed indoor circulating water aquaculture track.We focused on solving three problems.Firstly,we explored the starvation time and water flow speed to improve the muscle quality under starvation.Secondly,we tried to find a physical index to correlate with muscle quality.Finally,we wanted to know how to raise high-quality commercial fish in order to maintain a good taste.1.Using the self-designed and constructed indoor circulating water aquaculture track,100 healthy triploid crucian carp,with an initial weight of 513.5 ± 173.5 g were selected as the experimental subjects for starvation experiment.And the starvation experiment was randomly divided into 5 groups.The flow velocity of each group was as follows: group A was 0.11 m/s,group B was 0.09 m/s,group C was 0.07 m/s,group D was 0.05 m/s,group E was 0.03 m/s,for 4 weeks starvation in the circulating water breeding track.The body length and body weight of all fish were measured every week,and the survival rate(SR),weight loss rate(WLR)and relative fatness(RF)were calculated.Three fish in each group was dissected every week,and the weight of visceral mass and liver were measured,and the visceral ratio(VR),hepatopancreas index(HI)were calculated.The hydraulic and texture characteristics of the muscles were measured,and the conventional nutritional components,amino acid,fatty acid and geosmin(GSM)composition of the muscles were detected.The results showed that the SR of triploid crucian carp in each group was above95%,with no significant difference between groups(P > 0.05).With the prolonged starvation time,the weight in each group decreased significantly,the WLR of group C was the largest,and it was significantly different from the other four groups(P < 0.05).The VR and HI showed a downward trend with the increase of starvation time,and there was no significant difference between the groups(P > 0.05),both VR and HI were linearly positively correlated with RF.The drop loss rate,flesh leaching loss rate and liquid loss rate all showed an increase after 14 days of starvation.There was no significant difference in the texture characteristics in each group during the whole starvation(P > 0.05).The content of conventional nutrients such as moisture,crude protein and fat,was basically the same,with no significant difference between groups(P > 0.05).The amino acid composition of triploid crucian carp in each group was similar,and with the increase of starvation time,EAA/NEAA kept increasing,EAA/TAA ≈ 0.4.The content of flavor amino acids increased after 21 and 28 days of starvation.The essential amino acid index(EAAI)was the highest in the group B after7,14 and 21 days of starvation,and the highest in group C after 28 days of starvation,with no significant difference between groups(P > 0.05).The muscles of triploid crucian carp contained 27 fatty acids,the main fatty acids were palmitic acid,stearic acid and linoleic acid.The above results indicate that the starvation treatment under running water has an effect on shape,muscle quality and nutritional components of triploid crucian carp.Using a flow velocity of 0.07 m/s can quickly reduce the weight of triploid crucian carp.2.Relative fatness was divided into 5 groups equidistantly from 2.0 to 3.0.The RF of group A was 2.0 ≤ A< 2.2,the RF of group B was 2.2 ≤ B < 2.4,the RF of group C was 2.4 ≤ C < 2.6,the RF of group D was 2.6 ≤ D < 2.8,the RF of group E was 2.8 ≤ E<3.0.Through comprehensive analysis of muscle characteristics,composition determination and sensory evaluation of the fish in each group,it was found that the hardness,chewiness,gumminess,springiness,cohesiveness and resilience showed a downward trend with the decrease of relative fatness,the content of flavor amino acids,DHA and EPA in triploid crucian carp muscle increased with the decrease of RF.And the geosmin in muscle decreased sharply with the decrease of RF.The result showed that RF could be used as an indirect criterion for the improvement of muscle quality.When the RF drops to 2.4 or below,triploid crucian carp has higher nutritional value,less fishy smell and more delicious taste,and can be marketed as a high-quality product.3.A total of 75 healthy triploid crucian carp,with an initial weight of 398.6 ± 81.8g were selected and randomly divided into 5 groups.The feeding mode was as follows:group a was 0.1% PF,group b was 0.2%,group c was 0.3%,group d was 0.4% and group e was 0.5%,for 2 weeks of rearing in the circulating water aquaculture track.The body length and body weight of all fish were measured,and weight gain rate was(WGR)calculated.WGR kept increasing with the increase of compound feed,group a was the smallest,group e was the largest,there were significant differences between the two groups a and b and the other three groups(P < 0.05),and there was also a significant difference between group c and group e(P < 0.05).The results showed that when the daily feed is 0.1% of body weight,the high quality of triploid crucian carp meat can be maintained.In summary,the muscle quality of triploid crucian carp can be improved through breeding in indoor circulating water aquaculture track.It was found that under the condition of a flow velocity of 0.07 m/s,starvation can quickly reduce the weight of triploid crucian carp.When the fatness is 2.4 and below,the meat quality of triploid crucian carp is the most ideal.At this time,0.1% of its body weight can be fed with compound feed to maintain good muscle quality of triploid crucian carp. |
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