عنوان مقاله [English]
Harvesting, transporting, packaging, and storing the farmed shrimp Litopenaeus vannamei are factors that affect the quality of the shrimp Litopenaeus vannamei. The physical stress of the harvest leads to red hepatopancreas and eventually reddish color of the shrimp’s head. Vibriosis and stressful factors such as high pH of the pool and an increase in the organic load of the pool are also effective in causing the redhead syndrome. Redhead syndrome is a negative factor in the shrimp market. The aim of the study was redhead syndrome reduction strategies in the shrimp farm.
Material and methods:
Two farms were selected, each having three pools with different treatments. In the last month leading to the capture of shrimps, water parameters were measured. Different methods and speeds of transport were also measured. Transport temperature and percentage of redhead syndrome after freezing were measured and results were analyzed.
Results and discussion:
The results of different treatments showed that 2 to 5% of the harvested shrimps were redheaded, which was directly correlated with the total organic matter (TOM). The harvesting method and using supplementation and metabisulfite had no significant effect on the percentage of redheaded (P <0.05). Using styrofoam for transportation, the redhead syndrome was significantly less observed than the other treatments. Shrimp with redhead syndrome decreased from 16.47 in normal baskets to 3.5 in styrofoam. The normal transport temperature of shrimp was 11.77 °C, which decreased to -1.38°C in styrofoam transportation. In layered ice treatment, 7.67% redheaded shrimps were observed, which was less than the normal transport. The role of processing was more effective in causing redhead syndrome than the methods of culture and harvesting. The percent of shrimp with redhead syndrome were recorded in two farms 67.50±3.12 to 64.06±2.57 % in different treatments. The post-freezing temperature of shrimps at the two processing centers showed a significant difference (P <0.05). At center one, the temperature of frozen shrimp was -10.11±0.63 °C and the mean shrimps with redhead syndrome was 64.06±2.57. The mean temperature of frozen shrimp in the second processing centers was - 15.03±0.25° C and the mean number of shrimps with redhead syndrome was 67.50±3.12%.
According to the results, transport and harvest management were effective in the percentage of shrimps with redhead syndrome. The best way of transport was by using styrofoam that reduced the percent of redheaded shrimps to 3.5%. Harvest management was less effective in the percentage of redhead syndrome. In other words, with good management of harvest, transport with styrofoam, and good processing, we could reduce the redheaded shrimps by 3%, 8 to 11%, and 27 to 36%, respectively, and in total 38 to 50% after freezing.