International journal of food microbiology
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Int. J. Food Microbiol. · May 2013
Stuck fermentation: development of a synthetic stuck wine and study of a restart procedure.
Stuck fermentation is a major problem in winemaking, resulting in large losses in the wine industry. Specific starter yeasts are used to restart stuck fermentations in conditions determined essentially on the basis of empirical know-how. We have developed a model synthetic stuck wine and an industrial process-based procedure for restarting fermentations, for studies of the conditions required to restart stuck fermentations. ⋯ However, two strains were ranked differently in the "Gros Manseng" stuck wine. Nutrient content seemed to be a crucial factor in fermentation restart conditions, generating differences between yeast strains. However, the specific sensitivity of yeast strains to the composition of the wine may also have had an effect.
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Int. J. Food Microbiol. · Feb 2013
Spontaneous cocoa bean fermentation carried out in a novel-design stainless steel tank: influence on the dynamics of microbial populations and physical-chemical properties.
Spontaneous cocoa bean fermentations carried out in a novel-design 40-kg-capacity stainless steel tank (SST) was studied in parallel to traditional Brazilian methods of fermentation in wooden boxes (40-kg-capacity wooden boxes (WB1) and 600-kg-capacity wooden boxes (WB2)) using a multiphasic approach that entailed culture-dependent and -independent microbiological analyses of fermenting cocoa bean pulp samples and target metabolite analyses of both cocoa pulp and cotyledons. Both microbiological approaches revealed that the dominant species of major physiological roles were the same for fermentations in SST, relative to boxes. These species consisted of Saccharomyces cerevisiae and Hanseniaspora sp. in the yeast group; Lactobacillus fermentum and L. plantarum in the lactic acid bacteria (LAB) group; Acetobacter tropicalis belonging to the acetic acid bacteria (AAB) group; and Bacillus subtilis in the Bacillaceae family. ⋯ The profile of carbohydrate consumption and fermentation products in the pulp and beans showed similar trends during both fermentation processes. However, the yeast-AAB-mediated conversion of carbohydrates into ethanol, and subsequent conversion of ethanol into acetic acid, was achieved with greater efficiency in SST, while temperatures were generally higher during fermentation in wooden boxes. With further refinements, the SST model may be useful in designing novel bioreactors for the optimisation of cocoa fermentation with starter cultures.
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Int. J. Food Microbiol. · Jul 2012
Peptide nucleic acid fluorescence in situ hybridization for identification of Listeria genus, Listeria monocytogenes and Listeria ivanovii.
A fluorescent in situ hybridization (FISH) method in conjunction with fluorescin-labeled peptide nucleic acid (PNA) probes (PNA-FISH) for detection of Listeria species was developed. In silico analysis showed that three PNA probes Lis-16S-1, Lm-16S-2 and Liv-16S-5 were suitable for specific identification of Listeria genus, Listeria monocytogenes and Listeria ivanovii, respectively. ⋯ Of the 85 Listeria strains, thirty-seven were identified as L. monocytogenes with the probe Lm-16S-2 and two as L. ivanovii with the probe Liv-16S-5 which was in agreement with the results obtained by the API LISTERIA method. Thus, the PNA-FISH protocol has the potential for identification of pathogenic Listeria spp. from food or food-related samples.
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Int. J. Food Microbiol. · Jun 2012
Occurrence and characteristics of methicillin-resistant and -susceptible Staphylococcus aureus and methicillin-resistant coagulase-negative staphylococci from Japanese retail ready-to-eat raw fish.
Staphylococci are not part of the normal fish microflora. The presence of staphylococci on fish is an indication of (a) post-harvest contamination due to poor personnel hygiene, or (b) disease in fish. The aim of this study was to determine the prevalence, molecular genetic characteristics, antibiotic resistance and virulence factors of methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-resistant S. aureus (MRSA) and methicillin-resistant coagulase-negative staphylococci (MR-CoNS) isolated from 200 samples of retail ready-to-eat raw fish (sashimi) collected from the Japanese prefecture of Hiroshima. ⋯ None of the S. aureus isolates carried the Panton-Valentine leucocidin (PVL) encoding genes, lukF-PV and lukS-PV. To the best of our knowledge, this is the first report to show MRSA and MR-CoNS isolated from retail ready-to-eat food in Japan. Our results showed that sashimi is a likely vehicle for transmission of multidrug-resistant and toxigenic staphylococci.
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Int. J. Food Microbiol. · Nov 2011
Microbiological and chemical characterisation of ting, a sorghum-based sourdough product from Botswana.
Ting is a fermented sorghum product of Botswana which is used to prepare porridges of different consistencies. This study aimed to characterise ting with respect to fermentation microbiota and metabolite composition, and to develop starter cultures for ting fermentation. The pH values of 10 ting samples from Botswana ranged between 3.5 and 4.0 and cell counts ranged between 1.2×10(8) and 1.2×10(10)cfu/g lactic acid bacteria. ⋯ Major fermentation products were lactate, acetate and ethanol, additionally, 1,2 propanediol and 1,3 propanediol were produced by some strains. All strains were capable of producing ting, which was accompanied by a decrease in pH from 6.3 to 4 within 8h. Traditionally processed ting requires 2 to 3 days to attain a pH below 4; the starter cultures thus reduced the fermentation time to 8h.