Abstract:

The objective of this study was to optimize the conditions for killing Vibrio parahaemolyticus (Vp)
CGMCC1.1997 and Vibrio alginolyticus (Va) CGMC1.1833 in Cyclina sinensis using ultra-high pressure (UHP). Both
Vibrio species were treated in vitro and in vivo under different ultra-high pressure conditions including pressure, holding
temperature and holding time. Results showed that under the in vitro condition, the two strains at an initial concentration
of 108 CFU/mL were completely killed by UHP treatment at 300 MPa and at 20 ℃ for 5 min or more than 3 min at 30 ℃.
But the sterilization of Cyclina sinensis containing 108 CFU/mL of Vibrio was incomplete suggesting the muscle tissue of
Cyclina sinensis can protect against the inactivation of Vibrio by UHP treatment. The optimized UHP conditions for killing
108 CFU/mL of Vibrio present in Cyclina sinensis were determined as follows: 500 MPa and 30 ℃ for 30 min, 400 MPa and
40 ℃ for 30 min, or 600 MPa and 40 ℃ for 20 min. Under these conditions, the quantity of Vibrio in Cyclina sinensis at a
higher order of magnitude (107 CFU/g) was inactivated consistently demonstrating that the muscle tissue of Cyclina sinensis
can only provide limited protection on Vibrio. Therefore, Vibrio in contaminated Cyclina sinensis can be killed using ultrahigh
pressure treatment, although its muscle tissue has only limited protective effects the bacteria.

Key words: Cylcina sinensis, Vibrio parahaemolyticus, Vibrio alginolyticus, ultra-high pressure