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The quality changes of Litopenaeus vannamei stressed by acute hypoxia and stored under chilled conditions were studied. The stressed group was exposed to hypoxia (~0.5 mg L-1 DO/5h), whereas the control group to normoxia (5.0 mg L-1 DO). pH was significantly higher in stressed shrimp and increased throughout storage time. Total Volatile Bases (TVB-N) increased (p <0.05) during storage for both, control (70%) and stressed shrimp (87%). Maximum permissible limits of TVB-N were reached on day 9 and 6 for control and stressed shrimp respectively. In addition, higher Trimethylamine (TMA) concentrations were detected in control shrimp. No pathogens were detected for both shrimp, and the permissible limits of the monitored microorganisms were not exceeded. Ante mortem hypoxia had an effect on pH, but not on the microbiological quality, TVB-N and TMA-N values. [ABSTRACT FROM AUTHOR]

The influence of ante-mortem hypoxia on physicochemical stability of white shrimp ( Litopenaeus vannamei) muscle exposed to multiple freeze-thaw (F/T) cycles was evaluated. Results showed 5.7 and 10.8% decrements in water-holding capacity and myofibrillar protein solubility, respectively, for stressed shrimp during the first F/T cycle compared to control. Significant differences ( P ≤ 0.05) on myosin T were found comparing stressed and control fresh shrimp with a 1.4 °C increased on stressed fresh shrimp; however, no differences were found on Δ H values. With regard to stressed fresh shrimp actin, T increased ( P ≤ 0.05) 0.8 °C, while Δ H decreased ( P ≤ 0.05) by 0.12 J g, respectively. Regardless of the results found in fresh shrimp, no differences were found for myosin T and Δ H between stressed and control during the F/T cycles. SDS-PAGE showed no relevant changes induced by autolysis during the experiment. Histological analysis showed an increase of 257% in blank area of stressed fresh shrimp when comparing to control. Results showed the influence of ante-mortem hypoxia on the stability of fresh shrimp myofibrillar proteins, affecting its physicochemical properties. In contrast, for shrimp exposed to F/T cycles, the hypoxia effect was not relevant . [ABSTRACT FROM AUTHOR]