We compared the desoxycholate agar (DOA) media method to investigate the presence of coliforms at milk plants and its proposed substitute, the ISO Enterobacteriaceae test. In raw milk samples with only coliforms or Enterobacteriaceae, there was a good correlation (r≧0.98) between the number of bacteria on DOA and violet red bile glucose (VRBG) agar. In raw milk samples that contained Pseudomonas, which is a psychrotrophic bacteria, as well as coliforms or Enterobacteriaceae, the correlation between the number of bacteria on DOA at 30℃ and VRBG agar at 37℃ was weak. It was assumed that this was because the capability of supporting the growth of psychrotrophic bacteria by VRBG agar is inferior to that demonstrated by DOA; the difference in incubation temperatures greatly influenced this effect. The ratio of the bacteria grown on VRBG/DOA agar plates (VRBG/DOA) using the coliforms such as E. aerogenes NBRC 13534T and K. oxytoca JCM 1665 was 0.67–1.09 and 0.95–1.31, respectively. Because the bacterial count of Pseudomonas grown on VRBG agar was not suitably counted, the count differed depending on the strains used, incubation temperature, and layering conditions. For tests verifying the suitability of raw milk for shipment, if the purpose is to detect the presence of Enterobacteriaceae only, then the ISO Enterobacteriaceae test can be used. However, if psychrotrophic bacteria are also to be detected, then using the ISO Enterobacteriaceae test may not be suitable.
In 1999 and 2001, the Ministry of Health, Labour and Welfare of Japan notified the prefectural governors of the guidelines on sanitary controls such as the recommendation on the use of sterilized seawater for washing fishes and the use of refrigerated transport for the prevention of Vibrio parahaemolyticus food poisoning. Therefore, we examined how these national policies have impacted levels of V. parahaemolyticus in raw fishes in the market. We investigated the levels of V. parahaemolyticus in raw fishes and in seawater in Toyama Prefecture from July to October during 1979–1995 and 2008–2012. The isolation rate and geometric mean±S.D. (log10/100 ml) in V. parahaemolyticus-positive samples by the most probable number method from fishes collected during 1979–1995 (66.3%, 2.73±1.27) were significantly higher than in those collected during 2008–2012 (50.6%, 1.89±0.44; p<0.05). The isolation rate and geometric mean±S.D. (log10/100 ml) of V. parahaemolyticus-positive samples from seawater collected during 2008–2012 were 86.9% and 1.07±0.53, respectively. The gene encoding thermostable direct hemolysin (tdh) was detected by PCR in 20.5% of samples examined, and the O3 : K6 (tdh+) strain was isolated in 2 samples. These results reveal that V. parahaemolyticus was ubiquitous in seawater at fishing ports during the warm season. Furthermore, our findings suggest that adherence to the guidelines on sanitary controls has brought about a reduction of cases of V. parahaemolyticus food poisoning in recent years.
The optimization of hand washing in a meat processing plant was evaluated using total viable count and the amount of fat present on hands. The degree of contamination of workers' hands was also investigated. Fat amounts were evaluated using the easy quantitative stamp spread method. This method detected up to 10.0 mg of fat simply and quickly. Results showed increases in total viable count from 2.9 to 4.2 log cfu (p<0.05) and fat from 0.1 mg or less to up to 10.0 mg after meat handling. Furthermore, total viable count was associated with the amount of fat detected on workers' hands after meat handling. The results suggest that fat can be an effective indicator for hand washing in the meat processing plants. We verified the effectiveness of hand washing in the meat processing plant by measuring the reduction in bacterial counts and fat amounts. Results showed that hand washing by the 10 sec 2 times method most effectively decreased both the bacterial counts and fat amounts. We conclude that the 10 sec 2 times method was the quickest and most effective method of hand washing for the meat processing plants.
The purpose of this study is to examine availability of allylisothiocyanate (AIT) that prevent histamine producing in fish meat. Histamine poisoning by fish having red fresh (e.g., bigeye or skipjack tuna) is caused by histamine formed by bacteria. Histamine poisoning can be prevented by basic hygienic control, especially storing and handling fish at low temperatures using. However, there is a possibility of histamine poisoning induced by human error such as unsanitary handling or deficiency of management cold chain distribution. Previous study reported that AIT, essential oil of wasabi (Wasabia japonica), inhibited histidine decarboxylase activity and the growth of bacteria. Therefore, we checked up if AIT is available for one of the hurdle of histamine poisoning in the case of arising human error. We initially searched histamine producing conditions by inoculating with histamine forming bacteria in red fish. Subsequently, we performed experiments that fish were inoculated with AIT. We observed that it containing large amount of histamine forming bacteria without using AIT. In the case of AIT treating, we observed that it inhibited the growth of bacteria and the histamine production in bigeye tuna and skipjack tuna. In conclusion, AIT is suggested for one of the hurdle for preventing histamine poisoning.
Gluconacetobacter xylinus is transmitted by the fly which belongs to the genus Drosophila and grows without agitation in vinegar. In private households, a serious problem that a thick cellulose pellicle is formed frequently happens with vinegar. Therefore, we investigated to design the rice vinegar which has difficulty in growth of thick pellicle forming G. xylinus. On commercial products (rice vinegar in Japan) contained 4.2–4.6% acetic acid, the pellicle formation was observed at 24℃ in 6–9 days at a inoculum size of about 103cfu/ml. When the model medium containing ethanol, acetic acid, glucose, gluconic acid, yeast extract and polypeptone was used as a model of rice vinegar, the deletion of ethanol and a high concentration of glucose resulted in an increase of the lag phase. To apply this method to rice vinegar, the active carbon treatment was effective because of the deletion of nutrient from the degradation products of rice. In active carbon treated rice vinegar containing 4.4% acetic acid, 10.1% glucose and 0.30% gluconic acid (0% ethanol), and 2.8% acetic acid, 9.7% glucose and 5.2% gluconic acid (0% ethanol), the pellicle formation was observed in 14 days and 9 days, respectively, and satisfactory result was obtained as a prototype rice vinegar. The latter rice vinegar is very mild, and it is expected as a new type of vinegar.