EFFECTS OF HEATING, PH AND THERMORADIATION ON INACTIVATION OF VIBRIO-VULNIFICUS

The effects of heating, thermoradiation and pH (5·5 to 7·0) on inactivation of V. vulnificus cells in buffers, oyster and fish homogenates were studied. Cells were more sensitive to thermoradiation than heating or radiation alone. Synergistic effects were observed during thermoradiation of V. vulnificus (107 cells ml-1) at 40°C in buffer (pH 5·5), in fresh oyster (pH 6·2) and in fresh fish (pH 6·7). This synergistic effect was also noted when the same number of cells in fresh fish homogenates were irradiated at 45°C. Inactivation of cells varied depending on the environment and were more pronounced in buffers than in oyster or fish homogenates. The D10 (dose in kGy inactivating 90% of cells) at 25·C was 0·078 in buffer (pH 7·0), 0·125 in oyster (pH 6·2) and 0·187 in fish (pH 6·7), but at 35°C, the D10 values were 0·054, 0·093 and 0·125 kGy, respectively. Low initial numbers of cells (10 ml-1) in pH 7·0 buffer were rapidly inactivated by thermoradiation (40·C) compared to high cell number (107 ml-1) and the D10 (kGy) was 0·024 for the former and 0·047 latter. These D10 values (kGy) were 0·046 and 0·093 in fresh oysters (pH 6·2), 0·093 and 0·109 kGy in fresh fish (pH 6·7), for the low and the high cell numbers, respectively following thermoradiation at 40°C. © 1994 Academic Press. All rights reserved.