Effects of feed protein levels on digestive proteolytic activity, texture, and thermal denaturation of muscle protein in reared blue shrimp

Feeds containing 25, 35, and 40% protein were fed to blue shrimp (Litopenaeus stylirostris). The rate of growth, proteolytic activity of the hepatopancreas, instrumental texture and thermal denaturation of muscle protein, during three months of frozen storage at -20°C were determined. Shrimp fed with 40% protein feed had a significantly higher rate of growth, trypsin activity, and firmer texture. Thermograms of shrimp muscle proteins studied with differential scanning calorimetry showed three typical transition peaks. Whole muscle from shrimp fed 40% protein showed the lowest enthalpy of transition in the myosin peak. Shrimp fed 40% protein lost more texture, whereas organisms fed with 35% protein had a higher decrease of enthalpy during three months of frozen storage. The results indicate that feeding system influenced the texture characteristics in shrimp tail meat as well as growth rate.