食品防腐剤に関する研究-VII

Abstract

The organisms causing a type of deterioration of fish sausage by forming spots on the surface of fish sausage during storage were found to be B. coagulans by YOKOZEKI3) of the Tokai Regional Fisheries Research Station. It was also disclosed by the present authors4) that these organisms were highly resistant to nitrofurazone (NFS), a food preservative being permitted legally in Japan for keeping the quality of fish paste products such as “kamaboko”. According to OKA6), 7), the mechanism of growth inhibitory action of NFS to the NFS susceptible organisms might be due to the reduction of nitro-group in the NFS molecule, whereas, certain resistant organisms seemed to be poor or sometimes lacking in reducing ability for the furan compound. On the other hand, AMANO2) has reported that Pseudomonas fluo-rescens, one of the principal putrefactive organisms of raw fish, has a character to reduce nitro-group in the NFS molecule actively, and he concluded that the insensitivity of Pseudo-monas to NFS might be attributable to the rapid reduction of NFS in the medium. In the present study, comparison in the mode of destruction of NFS was carried out with 3 different types of organisms; the aforementioned NFS resistant strains of B. coagulans, NFS resistant strains of B. coagulans, NFS susceptible spore forming bacilli including sensitive B. coagulans, and naturally occurring NFS resistant strains of Pseudomonas and and Micrococcus. Results obtained may be summarized as follows: 1. In a peptone medium containing NFS, the fish sausage deteriorating organisms of B. coagulans kept a high level of residual NFS in the medium even after 1 week of incubation (Fig. 1), to the contrary, the susceptible bacilli and resistant Pseudomonas and Micrococcus decomposed NFS completely within a period of 2 to 3 days (Figs. 2 and 3). 2. This tendency has become more valid when the experiments using washed cells sus-pension of these organisms were conducted, viz., no appreciable reduction of NFS occurred in the cells of resistant B. coagulans, while rapid reduction was noted either in the suscep-tible B. coagulans or in the resistant Pseudomonas (Table 1). 3. These findings mentioned above may suggest the necessity of further detailed studies on the mechanism of nitrofurazone resistance by certain type of bacteria.