Standardization of sodium metabisulfite solution concentrations and immersion time for farmed shrimp Litopenaeus vannamei

Sodium metabisulfite is the main additive used in the prevention of melanosis in shrimp; however, it has currently been employed with great variation in concentration by producers. Thus, the aim of the present study was to determine the correlation between the concentration of the sodium metabisulfite solution and immersion time of the whole shrimp to obtain the concentration of sulfur dioxide (SO2) in the edible muscle of farmed shrimp (Litopenaeus vannamei) in accordance with the limit established by law. For this, solutions of sodium metabisulfite at different concentrations (1%, 2%, 3%, 4% and 5%) were prepared and samples of Litopenaeus vannamei shrimp (100g) were immersed during 10, 20 or 30 minutes at temperature of 7 degrees C. For all treatment assayed the concentration of SO2 was determined in the edible muscle of farmed shrimp (Litopenaeus vannamei). The results show that for the conditions used in this study, the correlations were linear, with significant increase (P<0.05) in the SO2 concentration in the edible muscle of shrimps both increasing sodium metabisulfite concentration as increasing immersion times, suggesting the immersion of shrimps in a 3% solution for a time of 13 minutes in order to obtain SO2 concentration of 100ppm in its edible muscle in accordance with Brazilian legislation.