The shrimp in the PPE group and chitosan group were dipped into the 1.5% of PPE and 1% of chitosan solutions at a shrimp/solution ratio of 1:2 (w/v) at 4 °C for 30 min, respectively. After dipping, the shrimp were drained at ambient temperature for 3 min. The shrimp in the chitosan coating + PPE group were immersed into the 1.5% of PPE at a shrimp/solution ratio of 1:2 (w/v) at 4 °C for 30 min. After that, they were dipped into 1% of chitosan solutions at a shrimp/solution ratio of 1:2 (w/v) at 4 °C for 30 min, and then were drained at ambient temperature for 3 min. Another portion of shrimp was treated in 1.25% of SMS dissolved in distilled water at a ratio of 1:2 (w/v) for 1 min at 4 °C. The samples from each treatment were covered in plastic bags and stored in ice using a shrimp/ice ratio of 1:2 (w/w). To maintain the shrimp/ice ratio, molten ice was removed and replaced with an equal amount of ice every 2 d.