In Japan, 13 kinds of food preservatives are approved for use by Food Sanitation Law, of which nitrofurazone (NFS), nitrofuryl acrylic amide (NFA), sorbic acid and sodium sorbate are permitted for such fish products as “kamaboko” (fish cake), fish sausage and whale meat products. Recently, chlortetracycline (CTC)-ice was permitted as an aid in keeping the freshness of fish hauls by trawlers.
The purpose of this study was to investigate the effect of incubation temperature, pH value of the medium or the addition of glucose upon the inhibitory action of all of the 13 food preservatives, as well as CTC and oxytetracyline (OTC) upon some species of cocci and bacilliincluding spore bearing organisms. In addition, a possibility of preventing allergy-like food poisoning due to consumption of some kind of fish products was studied by the aid of such preservatives as nitrofurazone, CTC or OTC.
Results obtained may be summarized as follows:
1. NFA and NFS were found to have the highest antibacterial action among the legally approved food preservatives and methyl-naphthoquinone (MNQ) and
p-hydroxy benzoic acidbutyl-ester (POBB) were the next.
At pH 7.0 and 20°C, growth of
Pseudomonas fluorescens was not inhibited by almost all of the preservatives. At the optimum growth condition,
Proteus morganii, the causative organism of allergy-like food poisoning, was inhibited only by NFA within the legally permissibleconcentration.
2. Minimum growth inhibitory concentrations of some agents in a medium of pH 7.0 were determined at 24, 48, and 72 hours of incubation.
As for NFS and NFA, the values did not change markedly in 72 hours. On the other hand, with CTC or OTC, the values tended to become larger as incubation period proceeded, indicating the decomposition of the antibiotics.
3. The antibiotic activity of CTC or OTC in nutrient broth at pH 7.0 markedly decreased during incubation at 37°C, the tendency was more conspicuous with CTC.
4. No marked difference was observed in the minimal growth inhibitory concentration of the food preservatives in the broth by changing hydrogen ion concentration within a range of pH from 6.0 to 7.5, or by the addition of 1 per cent of glucose. However, in the case of CTC, the value varied markedly in response to pH of the growth medium.
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