Effects of vitamin c on inhibition of polyphenoloxidase and quality changes of white shrimp (litopenaus vannamei) during cold storage

Abstract

Effects of vitamin C (vit C) on inhibition of polyphenoloxidase (PPO) and quality changes of pacific white shrimp (Litopenaus vannamei) during cold storage of 7 days were investigated and compared to shrimps treated with an additive in commerce (sodium metabisulfide, SMS) and control sample (treated by water). Vit C was able to inhibit the activity of PPO enzyme that extracted from cephalothoraxes of shrimps with average molecular weight of 3.5 kDa and PPO activity of 1.25 (unit/mg enzyme). At 100 mM vit C, PPO relative activities were 21.43 %. In addition, shrimp treated with vit C exhibited lower melanosis score and TBARs value than those in the control sample (p<0.05). These results suggested that vit C was able to slow down the oxidation process of fat and melanosis development in white shrimp during the cold processing. Besides, the quality of shrimps was evaluated base on microbiological analysis and pH measurement. After 5 days of storage at 2^oC, the effectiveness of preventing bacterial formation in shrimp samples was higher in vit C sample, SMS sample, and control sample.