Effects of Treatment with Chitosan on Sensory and Chemical Quality Parameters of Frozen Shrimp

This study was conducted to investigate the effects of chitosan treatment for a long time to preserve the qualities of shrimp during frozen storage. The experiments were performed on deepwater pink shrimp (Parapenaeus longirostris) caught from Marmara Sea. Fresh shrimps were divided into seven groups and immediately were dipped in tap water (control group) and solutions containing sodium metabisulphite (2500 mg/L), 4-hexylresorcinol (50 mg/L), chitosan (5 g/L), citric acid (50 mg/L) and rosemary extract (50 mg/L) for ten minute. After treatment, the shrimps were packaged and stored at -18 degrees C for twelve months. Sensorial characteristics, values of pH, TBA, TVB-N and TMA-N, rate of moisture of shrimp were determined periodically during frozen storage. All samples were palatable according to the panellist evaluation at the end of storage. However control group (untreated) shrimps were received lower scores. No significant changes on chemical parameters were determined during frozen storage and no difference among groups were observed. In particular, the initial TBA value, is already low levels, not elevated level to change the sensorial characteristics of the samples during storage. The results of this study indicated that freezing of raw shelled shrimp insures the acceptability for at least 12 months, and that treatment with chitosan solutions of shrimps did not cause a statistically significant difference.