The Effects of Chitosan Hydrocolloid and Its Oligosaccharides in Comparision with Sodium Pyrophosphate on Some Quality Properties of Vannamei shrimp (Litopenaeus vannamei) During Frozen Storage

In this study, the effects of the coating by chitosan (Cs) and its oligosaccharides (CsO) on some quality properties of peeled vannamei shrimp (Litopenaeus vannamei) during 3 months of frozen storage were compared with sodium pyrophosphate (SPP) (1 and 2%), Cs-SPP (1 and 2%) and CsO-SPP (1 and 2%). The moisture content, conjugated dienes (CD), thiobarbituric acid (TBA), color and texture properties of the samples were analyzed. The results showed that coating of shrimp by chitosan and its oligosaccharides, alone or in combination with SPP showed significant effects on the texture characteristics (springiness and chewiness) compared with the control and SPP-treated batches (P<0.05). The CD and TBA indices showed an increasing trend during storage (P<0.05). In the immersed treatments at CS 1% and in combination treatment with SPP, the TBA value was increased of 0.28 to 0.58 and 0.82 mg malondialdehyde/kg. This index was increased in the control and SPP (1 and 2%) to the 0.92 to 0.97 mg malondialdehyde/kg. According to the results, the treatments coated by chitosan and its oligosaccharide alone or in combination with sodium pyrophosphate had an effective role in inhibiting lipid oxidation and preventing its undesirable effects on frozen shrimp. In addition, color parameters (L*, a*, b*) in the treated samples by chitosan showed positive effects on stabilizing and improving the color of frozen shrimp during storage. Overall, the coating by chitosan and its oligosaccharides could maintain the quality of peeled frozen shrimp.