Hajime Takahashi

Tokyo University of Marine Science and Technology, Edo, Tōkyō, Japan

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Publications (55)100.73 Total impact

  • Takashi Kuda, Gensui Shibata, Hajime Takahashi, Bon Kimura
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    ABSTRACT: In order to study the effect of food residues on the survival of food-borne pathogens, Salmonella Typhimurium, Staphylococcus aureus, and Listeria monocytogenes were subjected to drying conditions in the presence of small amounts of food such as carrot juice, aqueous solution of nori, milk, and soy-milk. After drying for 2 h at room temperature in the absence of food residue, cell counts of S. Typhimurium, S. aureus, and L. monocytogenes decreased from 8 to 3, 6, and 5 log cfu/dish, respectively. Five milligrams of fresh carrot, 0.05 mg dried nori, and 100 nL milk or soy milk per 10 mm φ surface were sufficient to demonstrate a protective effect on the adhered pathogens, as confirmed by atomic force microscopy. Results from this study suggest that small sediments of food, not only protein rich but also carbohydrate rich, increase the resistance of surface-adherent bacteria to desiccation, rendering sanitization processes ineffective and encouraging cross contamination.
    Food Microbiology. 01/2015; 46:234–238.
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    ABSTRACT: Cases of histamine fish poisoning (HFP) have been reported worldwide. Although most cases of HFP are caused by mesophilic histamine-producing bacteria (HPB) when temperature abuse occurs, HFP could also be caused by psychrophilic HPB when fish are stored at low temperatures. In this study, mesophilic and psychrophilic HPB were isolated from a wide range of fish samples and identified by 16S rRNA and gyrB sequencing. Most of the mesophilic isolates were Photobacterium damselae subsp. damselae (42.7%) and Morganella morganii (24.0%), and most of the psychrophilic HPB were Photobacterium (94.9%). Whereas 76.0% of the mesophilic HPB produced more than 500 mg/kg of histamine (Hm), psychrophilic HPB generally produced lower Hm level, but 43.2% of these isolates still produced more than 500 mg/kg Hm. This study showed the importance of investigating not only mesophilic but psychrophilic HPB as well.
    Food Control 12/2014; 46:338–342. · 2.74 Impact Factor
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    ABSTRACT: Lc. lactis BF3 and Ln. mesenteroide BF7 were isolated from chum salmon intestines.•Compared with type strains, BF3 and BF7 showed tolerance to acid, bile, and salt.•BF3 and BF7 could ferment skimmed milk and soy milk.•Heat-killed BF3 and BF7 protected S. cerevisiae from H2O2 toxicity.•BF3 showed anti-inflammatory properties in macrophage RAW264.7.
    Journal of Functional Foods. 11/2014; 11.
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    ABSTRACT: Clostridium tyrobutyricum is a gram-positive spore-forming anaerobe that is considered as the main causative agent for late blowing in cheese due to butyric acid fermentation. In this study, multilocus variable-number of tandem repeat (VNTR) analysis (MLVA) for C. tyrobutyricum was developed to identify the source of contamination by C. tyrobutyricum spores in the cheese production environment. For each contig constructed from the results of a whole genome draft sequence of C. tyrobutyricum JCM11008(T) based on next-generation sequencing, VNTR loci that were effective for typing were searched using the Tandem Repeat Finder program. Five VNTR loci were amplified by polymerase chain reaction (PCR) to determine their number of repeats by sequencing, and MLVA was conducted. 25 strains of C. tyrobutyricum isolated from the environment, raw milk, and silage were classified into 18 MLVA types (DI=0.963). Of the C. tyrobutyricum strains isolated from raw milk, natural cheese, and blown processed cheese, strains with identical MLVA type were detected, which suggested that these strains might have shifted from natural cheese to blown processed cheese. MLVA could be an effective tool for monitoring contamination of natural cheese with C. tyrobutyricum in the processed cheese production environment because of its high discriminability, thereby allowing the analyst to trace the source of contamination.
    International journal of food microbiology. 08/2014; 190C:61-65.
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    ABSTRACT: To clarify the effect of type of foods on the intestinal environment, Far East Asian- (FEA; rich in rice starch, soy protein and soy oil) and Far East Asian marine- (FEAM; rich in rice starch, fish meal, fish oil and brown alga) modelled diets and sucrose, casein and beef tallow-rich (SCB) diet were prepared. After the 2-week administration of diets in rats, caecal organic acids and putrefactive compounds (ammonia, indole, phenol and H2S, which are regarded as putative risk factors for tumours) were determined. The caecal microbiota was also analyzed using denaturing gradient gel electrophoresis and pyrosequencing with bar-coded primers targeting the bacterial 16S rRNA gene. Levels of n-butyrate, acetate, indole and phenol were high in rats fed FEA. On the other hand, H2S was clearly suppressed by both FEA and FEAM comparing with SCB. These results suggest that FEAM is preferable to FEA for optimal intestinal environment and host health. Both microbial analyses showed that the diversity of microbiota in the FEAM group was lower than in the other diet groups. Ratio of Firmicutes, Bacteroidetes and Proteobacteria in the SCB group was about 5:4:1. Firmicutes, particularly Lachnospiraceae, was promoted by FEA and FEAM.
    Applied Microbiology and Biotechnology 02/2014; · 3.81 Impact Factor
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    ABSTRACT: Internalin A (InlA) facilitates the invasion of Listeria monocytogenes into a host cell. Some strains of Listeria monocytogenes express truncated forms of InlA, which reduces invasiveness. However, few virulence-related genes other than inlA have been analyzed in InlA-truncated strains. In the present study, we sequenced the draft genome of strain 36-25-1, an InlA-truncated strain, with pyrosequencing and compared 36 major virulence-related genes in this strain and a clinical wild-type strain. Strain 36-25-1 possessed all of the virulence-related genes analyzed. Of the analyzed genes, only 4 genes (dltA, gtcA, iap, and inlA) differed when the nucleotide sequences of strain 36-25-1 and the clinical wild-type strain were compared. Analysis of the deduced amino acid sequences found no mutations that significantly influenced virulence in genes other than inlA. The virulence-associated genes in strain 36-25-1 differ little from those of the clinical wild-type strain, indicating that a slight mutation in the nucleotide sequence determines the virulence of the InlA-truncated strain. In addition, the results suggest that, aside from InlA-mediated cell invasiveness, there is almost no difference between the virulence of strain 36-25-1 and that of the clinical wild-type strain.
    BMC Microbiology 01/2014; 14(1):15. · 2.98 Impact Factor
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    ABSTRACT: Listeria monocytogenes is the causative bacteria of listeriosis, which has a higher mortality rate than that of other causes of food poisoning. Listeria spp., of which L. monocytogenes is a member, have been isolated from food and manufacturing environments. Several methods have been published for identifying Listeria spp.; however, many of the methods cannot identify newly categorized Listeria spp. Additionally, they are often not suitable for the food industry, owing to their complexity, cost, or time consumption. Recently, high-resolution melting analysis (HRMA), which exploits DNA-sequence differences, has received attention as a simple and quick genomic typing method. In the present study, a new method for the simple, rapid, and low-cost identification of Listeria spp. has been presented using the genes rarA and ldh as targets for HRMA. DNA sequences of 9 Listeria species were first compared, and polymorphisms were identified for each species for primer design. Species specificity of each HRM curve pattern was estimated using type strains of all the species. Among the 9 species, 7 were identified by HRMA using rarA gene, including 3 new species. The remaining 2 species were identified by HRMA of ldh gene. The newly developed HRMA method was then used to assess Listeria isolates from the food industry, and the method efficiency was compared to that of identification by 16S rDNA sequence analysis. The 2 methods were in coherence for 92.6% of the samples, demonstrating the high accuracy of HRMA. The time required for identifying Listeria spp. was substantially low, and the process was considerably simplified, providing a useful and precise method for processing multiple samples per day. Our newly developed method for identifying Listeria spp. is highly valuable; its use is not limited to the food industry, and it can be used for the isolates from the natural environment.
    PLoS ONE 01/2014; 9(6):e99223. · 3.53 Impact Factor
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    ABSTRACT: The Ministry of the Environment, Government of Japan, defines a Satoumi as a coastal area where biological productivity and biodiversity has increased through human interaction. As a way to identify new starters and probiotics, we isolated and screened lactic acid bacteria (LAB) with acid, bile, and salt resistance from the intestines of 23 fish and 11 fermented fish samples obtained from the northeastern (Sanriku) Satoumi region of Japan. Of the 301 isolates, 75 strains were selected as LAB, 6 of which clearly showed increased antioxidant activities (DPPH and O2− radical scavenging and Fe-reducing power) in their cultured broth. Four isolates (S-SU1, 3–5) were identified as Lactobacillus plantarum. The two other strains (S-SU2, 6) identified were Lactococcus lactis and Pediococcus pentosaceus. In these in vitro assays, Lc. lactis S-SU2, isolated from sea pineapple kimchi showed the highest radical scavenging capacity. Moreover, the protective effect of heat-killed cells against the toxicity of 3 mM H2O2 on Saccharomyces cerevisiae was the highest for Lb. plantarum S-SU1 isolated from a salted squid product, followed by P. pentosaceus S-SU6 isolated from the intestines of blue mackerel. Furthermore, Lb. plantarum S-SU5 showed inhibitory effect against the toxicity of 3 mM H2O2 in human enterocyte-like HT-29-luc cells and on nitrite (NO) production in mouse RAW264.7 macrophage cells, which was induced by Escherichia coli O111 lipopolysaccharide (LPS). These results suggest that the selected LAB strains are potential starters and/or functional components with antioxidant and anti-inflammatory properties.
    Food Research International. 01/2014; 64:248–255.
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    ABSTRACT: Listeria innocua is an important hygiene indicator bacterium in food industries because it behaves similar to Listeria monocytogenes, which is pathogenic to humans. PFGE is often used to characterize bacterial strains and to track contamination source. However, because PFGE is an expensive, complicated, time-consuming protocol, and poses difficulty in data sharing, development of a new typing method is necessary. MLVA is a technique that identifies bacterial strains on the basis of the number of tandem repeats present in the genome varies depending on the strains. MLVA has gained attention due to its high reproducibility and ease of data sharing. In this study, we developed a MLVA protocol to assess L. innocua and evaluated it by tracking the contamination source of L. innocua in an actual food manufacturing factory by typing the bacterial strains isolated from the factory. Three VNTR regions of the L. innocua genome were chosen for use in the MLVA. The number of repeat units in each VNTR region was calculated based on the results of PCR product analysis using capillary electrophoresis (CE). The calculated number of repetitions was compared with the results of the gene sequence analysis to demonstrate the accuracy of the CE repeat number analysis. The developed technique was evaluated using 60 L. innocua strains isolated from a food factory. These 60 strains were classified into 11 patterns using MLVA. Many of the strains were classified into ST-6, revealing that this MLVA strain type can contaminate each manufacturing process in the factory. The MLVA protocol developed in this study for L. innocua allowed rapid and easy analysis through the use of CE. This technique was found to be very useful in hygiene control in factories because it allowed us to track contamination sources and provided information regarding whether the bacteria were present in the factories.
    PLoS ONE 01/2014; 9(9):e105803. · 3.53 Impact Factor
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    ABSTRACT: To clarify the effect of soy protein (SP) and fish meal (FM), compared to milk casein (MC), on the intestinal environment, we examined caecal environment of rats fed the test diets. Four-week-old rats were fed AIN-76-based diet containing 20 %, w/w MC, SP or FM for 16 days. Caecal organic acids were analysed by HPLC. Caecal putrefactive compounds (indole, phenol, H2S and ammonia) were analysed by colorimetric assays. Caecal microflora was determined by 16S rRNA gene-DGGE and pyrosequencing with bar-coded primers targeting the bacterial 16S rRNA gene. n-Butyric and lactic acid levels were high in rats fed SP and FM, respectively. Butyrate-producing bacteria, such as Oscillibacter, and lactate-producing bacteria, such as Lactobacillus, were detected in each diet group. Also, the putrefactive compound contents were high in rats fed SP and FM. In this study, both DGGE and pyrosequencing analyses were able to evaluate the dynamics of the intestinal microbiota. The results indicate that dietary proteins can alter the intestinal environment, affecting fermentation by the intestinal microbiota and the generation of putrefactive compounds.
    Applied Microbiology and Biotechnology 10/2013; · 3.81 Impact Factor
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    ABSTRACT: In this study, we investigated the use of ferulic acid, a type of phenolic acid, as a novel method for growth inhibition of Listeria monocytogenes, the causative agent of foodborne disease listeriosis. Ferulic acid showed an inhibitory effect against L. monocytogenes, with MIC values that did not differ among strains. In addition, when L. monocytogenes was inoculated onto cheese and smoked salmon, which are typical RTE food products, effective growth inhibition was achieved. Ferulic acid, a natural product extracted from plants, has been already used as a safe additive with antioxidant activity. This is the first report in which the bacterial growth inhibition by ferulic acid was studied in foods. Despite the relative ineffectiveness of ferulic acid at concentration of 1500 ppm against Escherichia coli O157:H7, Salmonella enterica, and Pseudomonas fluorescens, its ability to selectively inhibit L. monocytogenes makes it useful to control this bacterium in RTE foods, since most of the other bacteria don't grow or survive for long at low storage temperatures. Therefore, the use of ferulic acid is promising as a novel control method against L. monocytogenes in food industries dealing with RTE food products.
    Food Control. 09/2013; 33(1):244–248.
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    ABSTRACT: In 2011, a severe flood occurred in Thailand, covering nearly half the country in water for several months. The contamination of floodwater and subsequent contamination of water for human consumption could have potentially led to a widespread health crisis. However, to date, no study has been conducted to determine the safety of the waters used for human consumption in Thailand during the severe flood. Therefore, we conducted microbiological analysis of 4 kinds of water (floodwater, river water, tap water, and filtered tap water) collected from industrial and residential areas that were damaged due to flooding. Higher net levels of bacteria were found in water with a higher turbidity. No clear trend was observed in the pH value of all 4 water samples. The level of total bacterial contamination in the water samples was estimated by real-time quantitative polymerase chain reaction (PCR). Eleven of the 12 tap water samples and all of the filtered tap water samples had a total bacterial load that exceeded the Thai water quality standards. One of the tap water samples and one of the filtered tap water samples were found to be positive for Shigella sp., although none of the floodwater samples showed detectable levels of this pathogen as determined by PCR analysis. One of the samples of floodwater was also found to be positive for Leptospira sp., but none of the tap water or filtered tap water samples were positive. Most of the tap water samples and all filtered tap water samples were found to be contaminated with Vibriocholerae. Bacterial contamination in water samples was also analyzed by denaturing gradient gel electrophoresis (DGGE) analysis. These results revealed that several microorganisms were transferred via floodwater to different areas in the central part of Thailand and cross-contaminated between floodwater and water for human consumption.
    Science of The Total Environment 07/2013; 463-464C:959-967. · 3.16 Impact Factor
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    ABSTRACT: To examine the risk of food poisoning due to the consumption of contaminated processed squid products, we investigated the effects of selected low water activity, aw (about 0.55), and low pH (about 4.3) squid products on Salmonella Typhimurium and Staphylococcus aureus acid resistance in culture broth adjusted to pH 2.5 and 3.0. Pieces (0.3 g) of both squid products protected S. Typhimurium in 10 ml of acidified BHI broth adjusted to pH 3.0 and pH 2.5. S. aureus was also protected by the products in BHI broth adjusted to pH 3.0. Interestingly, S. aureus cell survival when spot inoculated on the low pH squid and transferred to broth was greater than for cells inoculated in the broth with pre-added low pH squid. These rapid protective effects on pathogens might result in longer survival in foods and allow introduction to the intestine through gastric acid resistance.
    Food Control. 04/2013; 30(2):569–574.
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    ABSTRACT: Brown algae contain soluble polysaccharides, such as alginic acid, fucoidan and laminaran. To assess the induction of dietary fiber-fermenting bacteria in the intestine, rats were fed diet containing no dietary fiber (control) or 2% w/w of the polysaccharides for 2 weeks. The levels of dietary fiber-fermenting bacteria in caecal contents were determined using decimal dilution culture containing 1% w/v of the fibers. Caecal microbiota in the rats was analyzed using polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE). In the culture method, 4–9 log viable cells/g caecal content of alginate-fermenting bacteria was detected in rats fed alginate, while this was not detected in rats fed the control diet. Although laminaran-fermenting bacteria were detected in control rats (4–9 log viable cells/g), the level observed in rats fed laminaran was 8 or 9 log viable cells/g. On the other hand, fucoidan-fermenting bacteria were not detected in rats fed fucoidan. DGGE analysis showed laminaran administration increased the diversity of bacterial bands. Clostridium spp. and Parabacteroides distasonis were detected as typical species in rats fed alginate and laminaran. The results indicate that the intake of soluble fermentable fibers in edible brown algae can alter the intestinal microbiota and its fermentation capacity.
    Journal of Functional Foods. 01/2013; 5(1):389–394.
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    ABSTRACT: The anti-inflammatory bowel disease (anti-IBD) activity of Leuconostoc mesenteroides 1RM3 isolated from saba-narezushi, which has known antioxidant properties, was examined by monitoring its immune and anti-inflammatory activities on murine macrophage RAW264.7 and dextran sodium sulphate (DSS)-induced IBD model mice. Heat-killed Ln. mesenteroides 1RM3 cells promoted nitric oxide (NO) generation in intact RAW264.7 cells. Ln. mesenteroides 1RM3 cells suppressed Escherichia coli O111 lipopolysaccharide (LPS)-induced NO generation. This bacterium also significantly protected RAW264.7 cells from cytotoxicity due to exposure to H2O2. In the case of mice administered with drinking water containing 5% (w/v) DSS, Ln. mesenteroides 1RM3 (about 9.7 log CFU/ml) suppressed colon inflammation, atrophy, diarrheal and bloody bowl discharge. These results suggest that Ln. mesenteroides 1RM3 could be used as probiotics to improve IBD.
    Journal of Functional Foods 01/2013; · 2.63 Impact Factor
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    ABSTRACT: Edible brown algae are a major food material in Far East Asian countries, particularly in Korea and Japan. They contain fermentable dietary fibers, alginic acid (uronic acid polymer) and laminaran (β-1, 3-glucan), that are fermented into organic acids by intestinal bacteria. To clarify the effect of edible algae on intestinal environment, the cecal microbiota of rats fed diets containing no dietary fiber (control), 2% w/w sodium alginate or laminaran for 2 weeks was analyzed using FLX amplicon pyrosequencing with barcoded primers targeting the bacterial 16S rRNA gene. The most abundant phylum was Firmicutes in all groups. Specifically, Allobaculum was dominant in all diet groups. In addition, Bacteroides capillosus (37.1%) was abundant in the alginate group, while Clostridium ramosum (3.14%) and Parabacteroides distasonis (1.36%) were only detected in the laminaran group. Furthermore, rats fed alginate showed simplified microbiota phylotypes compared with others. With respect to cecal chemical compounds, laminaran increased cecal organic acid levels, particularly propionic acid. Alginate increased total cecal organic acids. Cecal putrefactive compounds, such as indole, H(2)S and phenol, were decreased by both alginate and laminaran. These results indicate that edible brown algae can alter the intestinal environment, with the fermentation by intestinal microbiota.
    Applied and Environmental Microbiology 11/2012; · 3.95 Impact Factor
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    ABSTRACT: Listeria monocytogenes causes listeriosis in humans, mainly through the consumption of ready-to-eat foods such as cheese. Immunocompromised persons, the elderly, and pregnant women and their fetuses or newborns are at the highest risk for the infection. We examined the effects of dietary milk-casein (MC) and soy-protein (SP), and their digested compounds tryptone (TP) and phytone peptone (PP), respectively, on L. monocytogenes invasion and infection in human enterocyte-like Caco-2 cells and A/J mice. Invasion into Caco-2 cells tended to be high with TP. In A/J mice orally infected with L. monocytogenes, viable numbers in the liver and spleen showed a tendency of decreasing with the 20% SP diet compared to the 20% MC diet. SP suppressed the inflammation marker tumour necrosis factor-α in spleen tissue. Furthermore, bacteria lipopolysaccharide (LPS)-stimulated nitric oxide (NO) secretion from murine macrophage RAW 264.7 cells was suppressed by PP more than TP. These results suggest that major dietary proteins might affect infection and inflammation by L. monocytogenes.
    Food Chemistry 10/2012; 134(4):1719-23. · 3.33 Impact Factor
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    ABSTRACT: Listeria monocytogenes (Lm) causes food poisoning in humans mainly through consumption of ready-to-eat foods. Immunocompromised persons are at the highest risk for infection. We investigated effects of crude soluble polysaccharides (SPS) and ethanolic extract (EE) fractions of frond (kombu) and holdfast (ganiashi) parts of Laminaria japonica on Lm invasion into human enterocyte-like Caco-2 cells and immune and/or inflammatory reactions of murine macrophage RAW 264.7 cells. Recovery and viscosity were high in kombu SPS. Total phenolic content and antioxidant activities (2,2-diphenyl-1-picrylhydrazyl radical scavenging capacity and Fe-reducing power) were higher in ganiashi EE. EE of ganiashi, rather than kombu, suppressed the Lm invasion into the differentiated Caco-2 cells, though the inhibitory effect of SPS was not significant. Ganiashi SPS increased the nitric oxide (NO) production of intact RAW 264.7 cells. On the other hand, the NO production from Escherichia coli O111 lipopolysaccharide-activated cells was suppressed by kombu SPS and ganiashi EE. These results suggest that L. japonica, particularly ganiashi, might suppress the invasion and infection of Lm and also the inflammation.
    Applied biochemistry and biotechnology 08/2012; 168(4):928-35. · 1.94 Impact Factor
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    ABSTRACT: Listeria monocytogenes causes foodborne illnesses through consumption of ready-to-eat (RTE) foods. In this study, the synergistic effect of paired antimicrobial combinations against L. monocytogenes growth in RTE seafood was tested. 102 CFU/g of L. monocytogenes and a mixture of two different antimicrobials (nisin and lysozyme, nisin and ε-polylysine) were inoculated into minced tuna and salmon roe, and incubated at 10 °C or 25 °C for 7 days and 12 h, respectively. Among four different combinations tested, two combinations including nisin showed strong antilisterial effect in RTE seafood. These two combinations (nisin and ε-polylysine, nisin and lysozyme) reduced L. monocytogenes in number first and maintained the low cell number for a long period of time. This growth control method towards L. monocytogenes is useful in RTE seafood where heating or controlling pH or water activity is not practical.
    Food Control. 08/2012; 26(2):397–400.
  • Yuko Torido, Hajime Takahashi, Takashi Kuda, Bon Kimura
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    ABSTRACT: We have previously isolated psychrophilic histamine (Hm)-producing bacteria from fresh fish at low temperatures. Among these were strains that produce high levels of Hm even under low temperatures. In the present study, we inoculated 2 strains of psychrophilic Hm-producing bacteria into swordfish (104 cfu/g), and examined their behavior during storage at low temperatures (4 °C, 10 °C, and 15 °C). The average counts of normal viable bacteria and Hm-producing bacteria, and cumulative Hm levels in the fish were measured over time and analyzed. We detected Hm levels of 300 mg/kg or more in 5 days, and 800 mg/kg or more in 7 days, during storage at 4 °C. At 10 °C, we detected Hm levels of more than 150 mg/kg in 3 days, while at 15 °C, we detected Hm production of ≥200 mg/kg after 36 h. These data indicate that Hm accumulates in fresh fish during storage at low temperatures when psychrophilic Hm-producing bacteria are present. Further, we observe that inadequate storage temperatures cause the accumulation of Hm within a short time.
    Food Control. 07/2012; 26(1):174–177.

Publication Stats

231 Citations
100.73 Total Impact Points

Institutions

  • 2004–2014
    • Tokyo University of Marine Science and Technology
      • • Department of Food Science and Technology
      • • Faculty of Marine Science
      Edo, Tōkyō, Japan
  • 2011
    • National Food Research Institute
      Ibaragi, Ōsaka, Japan
    • Tokyo Kasei University
      Tōkyō, Japan
  • 2007
    • Hokusei Gakuen University
      Edo, Tōkyō, Japan
  • 2003
    • Tokyo University of Fisheries
      Edo, Tōkyō, Japan