| 1. |
- Aronsson, Kristina, et al.
(författare)
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Inactivation of Escherichia coli, Listeria innocua and Saccharomyces cerevisiae in relation to membrane permeabilization and subsequent leakage of intracellular compounds due to pulsed electric field processing
- 2005
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Ingår i: International Journal of Food Microbiology. - : Elsevier BV. - 0168-1605 .- 1879-3460. ; 99:1, s. 19-32
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Tidskriftsartikel (refereegranskat)abstract
- Membrane permeabilization, caused by pulsed electric field (PEF) processing of microbial cells, was investigated by measurement of propidium iodide (PI) uptake with flow cytometry. Inactivation of Escherichia coli, Listeria innocua and Saccharomyces cerevisiae was determined by viable counts, and leakage of intracellular compounds, such as ATP and UV-absorbing substances, was measured in the extracellular environment. Electrical field strength and pulse duration influenced membrane permeabilization of all three tested organisms of which S. cerevisiae was the most PEF sensitive, followed by E. coli and L. innocua. It was shown by viable counts, PI uptake and leakage of intracellular compounds that L. innocua was the most resistant. Increased inactivation corresponded to greater numbers of permeabilized cells, which were reflected by increased PI uptake and larger amounts of intracellular compounds leaking from cells. For E. coli and L. innocua, a linear relationship was observed between the number of inactivated cells (determined as CFU) and cells with permeated membranes (determined by PI uptake), with higher number of inactivated cells than permeated cells. Increased leakage of intracellular compounds with increasing treatment severity provided further evidence that cells were permeabilized. For S. cerevisiae, there was higher PI uptake after PEF treatments, although very little or no inactivation was observed. Results suggest that E. coli and L. innocua cells, which took up PI, lost their ability to multiply, whereas cells of S. cerevisiae, which also took up PI, were not necessarily lethally permeabilized. © 2004 Elsevier B.V. All rights reserved.
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| 2. |
- Borch, Elisabeth, et al.
(författare)
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Influence of long-chain polyphosphate and heat treatment on Clostridium cochlearium and Clostridium sporogenes isolated from processed cheese spread
- 2007
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Ingår i: Journal of Food Protection. - 0362-028X .- 1944-9097. ; 70:3, s. 744-747
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Tidskriftsartikel (refereegranskat)abstract
- The outgrowth of Clostridium spp. spores causes spoilage in processed cheese products due to gas and off-odor formation. The present study focuses on the response of spores of Clostridium sporogenes and Clostridium cochlearium at 25°C to polyphosphate, both alone and in combination with heat treatment. The two strains used were isolated from spoiled cheese spread. The addition of 1.5% polyphosphate but not 0.75% polyphosphate totally inhibited the growth of C. sporogenes SIK4.3; in contrast, 0.75% polyphosphate was sufficient to totally inhibit C. cochlearium CCUG 45978. The highest polyphosphate concentration tested (1.5%) was sporicidal for C. sporogenes SIK4.3 but not for C. cochlearium CCUG 45978. When 0.75% polyphosphate Bekaplus FS was combined with a holding time of 5 min at 98°C, no survival or growth of C. sporogenes SIK4.3 was detected; however, the same effect was not achieved through heating alone or through application of polyphosphate alone. C. cochlearium CCUG 45978 was more heat tolerant, as shown by higher D-values. In conclusion, the results strongly suggest that polyphosphate Bekaplus FS has the potential to restrict the growth of C. sporogenes and C. cochlearium in cheese spread stored at ambient storage temperature. Experiments with cheese are needed in order to verify this effect. Copyright ©, International Association for Food Protection.
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| 3. |
- Kure, C.F., et al.
(författare)
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Use of the selective agar medium CREAD for monitoring the level of airborne spoilage moulds in cheese production
- 2008
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Ingår i: International Journal of Food Microbiology. - : Elsevier BV. - 0168-1605 .- 1879-3460. ; 122:42006, s. 29-34
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Tidskriftsartikel (refereegranskat)abstract
- It was investigated if a selective medium for common cheese spoiling moulds (CREAD) could give more relevant information than a general mould medium in hygienic air-sampling in cheese factories. A total of 126 air-samples were taken in six Nordic cheese factories using the general mould medium DG18 and CREAD. The level and genera of air-borne mould was determined. Identification to species-level was performed for a selection of samples. In five cheese factories the mycobiota was dominated by Penicillium spp. and in one cheese factory by Cladosporium spp. The concentration of air-borne moulds varied between the cheese factories ranging from 1 to 270 cfu/m3 on DG18 with a median value of 17. The number of mould colonies was in general lower at CREAD. Identification indicated that CREAD supported growth of common spoilage moulds for cheese, such as Penicillium palitans and P. commune. The mycobiota on DG18 also consisted of moulds not commonly associated with spoilage of cheese, such as Cladosporium spp., P. brevicompactum and P. chrysogenum. Contamination of cheese with mould is periodically a problem in production of semi-hard cheese and the level of air-borne mould is therefore routinely monitored in cheese factories. A clear correlation between the total number of moulds in air and mould growth on products is not always found. The conclusion from the investigation is that it is recommended to use a selective medium for cheese spoilage moulds, such as CREAD in hygienic monitoring. © 2007 Elsevier B.V. All rights reserved.
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| 4. |
- Lycken, L., et al.
(författare)
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Characterization of Clostridium spp. isolated from spoiled processed cheese products
- 2006
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Ingår i: Journal of Food Protection. - 0362-028X .- 1944-9097. ; 69:8, s. 1887-1891
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Tidskriftsartikel (refereegranskat)abstract
- Of 42 spoiled cheese spread products, 35 were Found to harbor Clostridium spp. Typical signs of spoilnge were gas production and off-odor. The identity was determined for about half of the isolates (n = 124) by Analytab Products (API), Biolog, the RiboPrinter System, 16S rDNA sequencing, cellular fatty acid analysis, or some combination of these. The majority of isolates were identified as Clostridium sporogenes (in 33% of products), but Clostridium cochlearium (in 12% of products) and Clostridium tyrobutyricum (in 2% of products) were also retrieved. Similarity analysis of the riboprint patterns for 21 isolates resulted in the identification of 10 ribogroups. A high degree of relatedness was observed between isolates of C. sporogenes originating from products produced 3 years apart, indicating a common and, over time, persistent source of infection. The spoilage potential of 11 well-characterized isolates and two culture collection strains was analyzed by inoculating shrimp cheese spread with single cultures and then storing them at 37°C. Tubes inoculated with C. tyrobutyricum did not show any visible signs of growth (e.g., coagulation, discoloration, gas formation) in the cheese spread. After 2 weeks of incubation, tubes inoculated with C. cochlearium or C. spoprogenes showed gas-holes, syneresis with separation of coagulated casein and liquid, and a change in color of the cheese. The amount of CO2 produced by C. cochlearium strains was approximately one-third that produced by the majority of C. sporogenes strains. To our knowledge, this is the first study to isolate and identify C. cochlearium as a spoilage organism in cheese spread. Copyright ©, International Association for Food Protection.
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| 5. |
- Mjönes, Anna-Britta, et al.
(författare)
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Hoarseness and misdirected swallowing in patients with hiatal hernia
- 2007
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Ingår i: European Archives of Oto-Rhino-Laryngology. - : Springer Science and Business Media LLC. - 0937-4477 .- 1434-4726. ; 264:12, s. 1437-1439
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to elucidate whether misdirected swallowing is an extra-laryngeal cause of hoarseness and investigate whether the prevalence of misdirected swallowing and hoarseness in patients with hiatal hernias differ from those with and without pathological gastroesophageal reflux (GER). One hundred and ninety eight patients with hiatal hernias diagnosed via esophageal manometry and pH-reflux test and 262 subjects in the general population who did not have a hiatal hernia at endoscopy, filled in a questionnaire about symptoms on hoarseness, misdirected swallowing, and heartburn. Hoarseness (35%), misdirected swallowing to the larynx (MSL; 35%), misdirected swallowing to the nose (MSN; 22%) and heartburn (85%) were significantly more common in patients with hiatal hernia than in controls (13, 5, 1, and 6%, respectively, P<0.001). MSL and MSN in the patient group were significantly interrelated (P<0.0001). Hoarseness and MSL were not significantly associated (P<0.076). Hoarseness and MSL were as common in the hernia group with normal GER, as in the group with pathological GER. There is a predisposition for hoarseness and MSL in patients with hiatal hernias, but the cause-and-effect relationship is unclear. Hoarseness does not seem to be caused by pathological GER.
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| 6. |
- Nielsen, Tim, et al.
(författare)
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The origin of off-odours in packaged rucola (Eruca sativa)
- 2008
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Ingår i: Food Chemistry. - : Elsevier BV. - 0308-8146 .- 1873-7072. ; 110:1, s. 96-105
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Tidskriftsartikel (refereegranskat)abstract
- Rucola (Eruca sativa) was decontaminated and then reinoculated with selected microorganisms. The produce was then stored in three different atmospheres and at two temperatures. The accumulation of off-odours in the packaging headspace was analysed. A dozen compounds were detected by olfactometry but only dimethyl sulphide and dimethyl disulphide were considered to have a strong or moderate intensity. Thus, they were identified as the substances causing an unpleasant smell inside the bags. Inoculation with microorganisms resulted in higher production of off-odours. Samples inoculated with Pseudomonadaceae&Xanthamonadaceae were particularly potent in producing the two sulphides. The off-odour problem was much more prominent in samples that were kept in a packaging material that did not allow gas exchange resulting in oxygen levels below 1%. Higher levels of sulphides were detected at 8 °C than at 4 °C. © 2008 Elsevier Ltd. All rights reserved.
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| 7. |
- Rönner, Anna-Clara, 1971, et al.
(författare)
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Genetic profiling of Campylobacter jejuni strains from humans infected in Sweden or in Thailand, and from healthy Swedish chickens, studied by pulsed-field gel electrophoresis (PFGE).
- 2005
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Ingår i: Scandinavian journal of infectious diseases. - : Informa UK Limited. - 0036-5548 .- 1651-1980. ; 37:8, s. 579-584
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Tidskriftsartikel (refereegranskat)abstract
- The major objective of the study was to explore the genomic diversity between Campylobacter jejuni (C.jejuni) from different sources as a tool for epidemiological considerations. Subtyping was performed using pulsed-field gel electrophoresis (PFGE) and the enzyme used for cleavage was SmaI. Isolates originated from humans infected in Sweden (n=49) and Thailand (n=32) and from healthy Swedish chickens (n=51). Eight PFGE groups were formed in a dendrogram and 48% of the isolates belonged to 1 of these groups. In 2 PFGE groups, strains from humans infected in both Sweden and Thailand were represented. Four of the PFGE groups comprised high frequencies of strains from domestic human infection, as well as from healthy chickens. The PFGE pattern was also compared with the antibiotic resistance pattern in all the above-mentioned isolates. In conclusion, C.jejuni was a diverse group based on PFGE genotyping; about 24% of the clones from Swedish patients and healthy Swedish chickens were similar; and there was no correlation between the antibiotic resistance pattern and the PFGE profiling among the studied strains. Our findings are also in accordance with our hypothesis that there may be similarities between Swedish and Thai strains, which might support a theory of globally occurring C.jejuni.
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| 8. |
- Staack, N., et al.
(författare)
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Effect of infrared heating on quality and microbial decontamination in paprika powder
- 2008
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 86:1, s. 17-24
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Tidskriftsartikel (refereegranskat)abstract
- Infrared radiation (IR) was explored as a technique for decontaminating paprika powder. The effect of water activity (aw) and IR heat flux on paprika temperature and water loss were measured during near- or medium-IR heating. Paprika was evaluated in terms of colour, aw, natural flora, and inoculated Bacillus cereus spores. Surface temperatures were considerably higher than temperatures inside the powder, especially at low aw; greater differences were observed with medium- than with near-IR. Surface darkening was observed, though the overall colour was not considerably affected. IR effectively removed water from paprika, especially at aw 0.5 and 0.8, resulting in unsatisfactory spore reduction. However, at aw 0.8, the load of the natural flora was reduced (P < 0.05). In aw 0.96 powder, areas with high remaining aw displayed a reduction >6 log10 CFU/g for B. cereus (P < 0.05). In addition, no microbial counts of the natural background flora were observed in the paprika. © 2007 Elsevier Ltd. All rights reserved.
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| 9. |
- Staack, N., et al.
(författare)
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Effects of temperature, pH, and controlled water activity on inactivation of spores of Bacillus cereus in paprika powder by near-IR radiation
- 2008
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Ingår i: Journal of Food Engineering. - : Elsevier BV. - 0260-8774 .- 1873-5770. ; 89:3, s. 319-324
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Tidskriftsartikel (refereegranskat)abstract
- A process to decontaminate paprika powder using variable near-infrared (IR) radiation was tested using a closed sample holder allowing water to be retained in the powder. The reduction in the concentration of Bacillus cereus spores and changes in water activity (aw) and colour were measured during IR heating. High heat flux was applied initially to heat the powder rapidly to the desired temperature, followed by low heat flux to maintain the temperature for a given time. The water activity (aw) value of the powder could be maintained within the bulk of the closed sample, but the surface aw value decreased during heating. Due to carotenoid sensitivity to temperature, surface and overall colour values declined, though remaining acceptable values of medium red and red, respectively. For powder with an aw value of 0.88 heated to 95-100 °C, the load of B. cereus spores was reduced by 4.5 log10 CFU/g within 6 min; the final spore concentration remained approximately 2 log10 CFU/g due to tailing. Reducing pH to 4.0 from 4.5 did not significantly affect the reduction of the B. cereus spore concentration. © 2008 Elsevier Ltd. All rights reserved.
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