Application of high hydrostatic pressure for the inactivation of norovirus and quality stability in fresh sea squirt (Halocynthia roretzi).

Sea squirt (Halocynthia roretzi) is considered a potential cause of human norovirus in Korea. This study investigated the effect of high hydrostatic pressure at 100-500 MPa for 5 min at room temperature (23 ± 2 ℃) on the inactivation of murine norovirus-1 (initial inoculum of 6-7 log10 plaque forming units/ml) as a human norovirus surrogate in fresh sea squirt. The effects of high hydrostatic pressure on the Hunter colors and pH were also examined as the main indices of quality. No reductions in murine norovirus-1 titers were observed in sea squirt treated at 100-400 MPa. However, murine norovirus-1 in sea squirt was completely inactivated by 500 MPa of high hydrostatic pressure. Furthermore, the Hunter colors ("L," "a," and "b") and pH values (6.10-6.19) were not significantly (P > 0.05) different between non-high hydrostatic pressure-treated sea squirts and all high hydrostatic pressure-treated sea squirts. Therefore, 500 MPa of high hydrostatic pressure at room temperature may be an optimal treatment for Tunicata meat without altering the food quality (color and pH).

Bactericidal Effect of Calcium Oxide (Scallop-Shell Powder) Against Pseudomonas aeruginosa Biofilm on Quail Egg Shell, Stainless Steel, Plastic, and Rubber.

The aim of this study was to evaluate the bactericidal effect of calcium oxide (CaO) against Pseudomonas aeruginosa biofilms on quail eggshells and major egg contacting surfaces (stainless steel, plastic, and rubber). The samples were subjected to CaO treatments (0%, 0.01%, 0.05%, 0.10%, 0.15%, 0.20%, 0.25%, and 0.30%) for 1 min. All the CaO treatments significantly reduced P. aeruginosa biofilms on all tested surfaces as compared to controls. In comparison of biofilm stability, the strongest and most resistant biofilm was formed on eggshell against the CaO treatment, followed by rubber, stainless steel, and plastic. In evaluation of bactericidal effect, the largest reduction (3.16 log CFU) was observed in plastic even at the lowest concentration of CaO (0.01%), whereas the least reduction was found in eggshells, regardless of CaO concentration. In addition, stainless steel showed a significant reduction in biofilm formation at all concentrations except 0.10% to 0.15% CaO. At 0.30% CaO, the reduction of P. aeruginosa in biofilms on stainless steel, plastic, rubber, and eggshell were 5.48, 6.37, 4.87, and 3.14 log CFU/cm2 (CFU/egg), respectively. Biofilm reduction after CaO treatment was also observed by field emission scanning electron microscopy (FE-SEM). Based on the FE-SEM images, we observed that P. aeruginosa biofilms formed compact aggregations on eggshell surfaces with CaO treatments up to 0.30%. More specifically, a 0.20% CaO treatment resulted in the reductions of 3 to 6 log CFU in all materials.