Abstract
To investigate the multiplication of soft-rot bacteria during the processing and storage of 'Asazuke' of Chinese cabbage, the bacteria transformed with plasmid pBR325 to acquire a resistance to three antibiotics, were used for quantification based on both antibiotic resistance and growth on selective medium. The soft-rot bacteria readily multiplied in the 2 xTY medium modified with a concentration of 2-3 % NaCl, in which 'Asazuke' of Chinese cabbage was usually prepared. When the medium with a pH of less than pH 4.5 was used, soft-rot bacteria could not multiply although they multiplied in a medium with a pH of more than 6.0. The pathogenicity of the transformed bacteria to Chinese cabbage was similar to that of the non-transformations. The addition of the antibiotics to the medium suppressed almost completely the formation of colonies of the leaf surface bacteria prepared from healthy Chinese cabbage. The use of a modified crystalviolet-pectate medium combined with antibiotic resistance was more suitable for the suppression of the multiplication of the leaf surface bacteria, suggesting that the transformed bacteria could be quantitatively assayed under contaminants. During the storage of 'Asazuke' of Chinese cabbage at 5°C, the concentration of the soft-rot bacteria in the soaked fluid for 'Asazuke' did not change for 15 days. However, upon storage at 10°C, the bacteria multiplied gradually, and the pH of the solutions decreased along with the appearance of turbidity.
