The capacity for the removal of pyrimethanil and fenhexamid, two fungicides commonly used for the... more The capacity for the removal of pyrimethanil and fenhexamid, two fungicides commonly used for the control of Botrytis cinerea in vineyards, has been evaluated during an alcoholic fermentation process in batch system. Commercial and wild strains of Saccharomyces cerevisiae were used. Batch fermentations were carried out in yeast extract-malt extract medium (YM) with 18.0 % (by mass) glucose, and the fungicides were added separately at three concentrations: 0.1, 1.0 and 10.0 mg/L. The removal capacity of yeast strains was also examined in stationary phase cultures of Saccharomyces cerevisiae. Stationary assays were performed with yeast biomass harvested from the stationary phase of an anaerobic fermentation process, with separate additions of 0.1, 1.0 and 10.0 mg/L of both fungicides. Removal studies with stationary phase cells were performed with viable and non-viable cells inactivated with sodium azide. This study clearly shows that both Saccharomyces cerevisiae strains were able to remove fenhexamid and pyrimethanil in stationary and fermentative assays. The removal potential is shown to be strain dependent in stationary but not in fermentative assays. However, the removal potential is dependent on the type of fungicide in both stationary and fermentative assays. In stationary phase cultures no significant difference in fungicide removal potential between viable and non-viable cells was observed, indicating that both pesticides were not degraded by metabolically active cells. However, the presence of both pesticides influenced fermentation kinetics and only pyrimethanil at 10.0 mg/L increased the production of volatile acidity of both strains.
The most important prerequisite for the application of PCR-based methods, among them the detectio... more The most important prerequisite for the application of PCR-based methods, among them the detection and quantifi cation of genetically modifi ed organisms (GMOs) is the ability to extract signifi cant amounts of DNA of adequate quality from the sample under investigation. The sample of interest in our work was soybean lecithin with expected low DNA content. The aim of this study was to set up a fast and effective HPLC (High Performance Liquid Chromatography) method using CIM ® (Convective Interaction Media, BIA Separations d.o.o., Ljubljana, Slovenia) DEAE (DiEthylAminoEthyl) anion-exchange disk monolithic columns (disks) for the isolation of DNA from soybean lecithin samples. As the reference isolation procedure we used CTAB (CethylTrimethylAmmonium Bromide) method, which is widely used in GMO detection. It was demonstrated, that CIM ® DEAE disks allow effi cient isolation of DNA from soybean lecithin. Furthermore, in comparison with the CTAB method, the method was less time-consuming and reduced the use of some aggressive chemicals. The quality of isolated DNA was tested with spectrophotometric analysis, agarose gel electrophoresis and by amplifi cation of soybean specifi c lectin gene with qualitative and real-time PCR. The isolated soybean DNA was of adequate quantity and quality for PCR analysis, even though mostly degraded, present in small amounts and contaminated with some impurities, among them potential PCR inhibitors. The study expanded the applicability of monolithic columns in the isolation of biomolecules from highly processed food materials and their potential use for nucleic acids detection.
The aim of this study was to assess the potential of bacteria Escherichia coli ATCC 35218, Pseudo... more The aim of this study was to assess the potential of bacteria Escherichia coli ATCC 35218, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923 and yeast Pichia membranifaciens ZIM 2417 to adhere to wooden surfaces such as poplar (Populus sp.), Norway spruce (Picea abies), European beech (Fagus sylvatica), beech coated with the commercial Belinka oil food contact and disinfectant P3-oxonia active 150, and investigate their survival on the beech wood surface under different relative humidities (RH; 65%, 75%, 85%, 98%) and temperatures (10 °C, 20 °C, 27 °C/37 °C). To extend the research goals, the scanning electron microscopy (SEM) analysis was also performed. The adhesion was determined by the number of colony-forming units per mm 2 of sample (CFU/mm 2 ). Results showed that all tested bacteria and yeast were able to adhere to the wooden surfaces, although differences were observed according to strains and type of wood. It was evident that number of adhered cells of S. aureus was lower on spruce (3.62 × 10 3 CFU/mm 2 ) compared to poplar and beech (1.09 × 10 5 and 2.11 × 10 4 CFU/mm 2 , respectively). Furthermore, oil and disinfectant promoted the adhesion of P. aeruginosa (155.93 and 130.50%, respectively) on the beech surfaces, while they had a strong inhibitory effect on the other tested microorganisms E. coli (87.44 and 88.44%, respectively), S. aureus (91.24 and 96.80%, respectively) and P. membranifaciens (92.45 and 87.24%, respectively). These findings are consistent with SEM micrographs. The current data also indicated that relative humidity and temperature significantly affected the adhesion of tested bacteria and yeast. The highest degree of adhesion was observed at a relative humidity of 98% and temperature of 20 and 37 °C for bacteria, or 20 and 27 °C for yeast. Thus, the knowledge of how these microorganisms adhere to wooden surfaces and which factors affect this phenomenon proves to be of great importance in order to avoid their colonization.
Apple pomace consists of a press cake resulting from pressing apples for various juices as well a... more Apple pomace consists of a press cake resulting from pressing apples for various juices as well as from other fruit industry wastes. In general it is an acid substrate with a considerably buffering capacity, rich in carbohydrates, and low in protein content. A rapid spoilage caused by microorganisms can start because of a high moisture content of fresh pomace. Suitable preservation methods should be applied, otherwise apple pomace has to be utilized as soon as it is produced. The best approach for disposing of apple pomace is its conversion to some useful products. Such conversion can be done by: — biological methods (solid state fermentation) — non biological methods (pyrolysis, drying, extraction)
PurposeThe main objective of this study is to find out how food handlers in catering establishmen... more PurposeThe main objective of this study is to find out how food handlers in catering establishments perceive ensuring food safety and which problems they meet along the way.Design/methodology/approachUsing a qualitative approach, ten food handlers in Slovenian catering facilities were included in the case study. A semi-structured approach was applied to provide a deeper insight into food safety barriers perceived by respondents. Participants first read short fictitious newspaper news about a foodborne disease at a tourist farm, which served as a starting point.FindingsThe results demonstrate barriers which most often originate in a lack of knowledge (e.g. improper food safety training, incorrect food safety knowledge testing, knowledge and maintaining of CCPs), shortage of food hygiene skills (e.g. handwashing, food defrosting) and weak work satisfaction (e.g. insufficient payment, poor interpersonal relationships and weak motivation). Food safety knowledge and consequently training methods were found to be the biggest barrier for the efficiency of the HACCP system in practice.Research limitations/implicationsDue to the small sample, the results cannot be generalised to the entire population of food handlers in Slovenia.Practical implicationsThe results indicate weaknesses in food safety knowledge among professional food handlers.Originality/valueThe study provides a deeper insight into implicit opinions of ten food handlers in catering facilities regarding barriers in providing food safety, their knowledge and behaviour in their work with food.
A serious global problem with the increasing resistance of microorganisms to currently used antim... more A serious global problem with the increasing resistance of microorganisms to currently used antimicrobials has opened up the promotional research in the identification of new, more effective drugs with a broad spectrum of antimicrobial activities. Plant essential oils, due to the large biological and structural diversity of their components, are known to have many potential benefits. This study aimed to evaluate the antimicrobial and anti-adhesion activity of fifteen essential oils and their compounds against two bacterial and two yeast species responsible for food spoilage and infectious diseases. Antimicrobial activity was determined by testing the minimum inhibitory concentration (MIC), the minimum bactericidal concentration (MBC) and the minimum fungicidal concentration (MFC) of essential oils and compounds. The essential oils of Cinnamomum zeylanicum and Eugenia caryophyllus showed the highest antimicrobial activity with MICs ranging from 0.078 to 1.25 mg/mL, and 0.039 to 1.25 mg/mL, respectively. On the other hand, essential oils of Eucalypti aetheroleum and Salvia officinalis had significantly weaker antimicrobial properties than the others. Further, MICs were used to assess the inhibition of adhesion of bacteria Salmonella Typhimurium ATCC 25923 and Staphylococcus aureus ATCC 14208, and yeasts Candida albicans ATCC 10231 and Saccharomyces cerevisiae ATCC 9763 in a microtiter plate using the crystal violet staining method. Based on the percentage of adhesion inhibition, yeast S. cerevisiae ATCC 9763 showed a high level of antimicrobial resistance. E. caryophyllus had the strongest effect with inhibition up to 73%. Consistent with the antimicrobial susceptibility results, the most active anti-adhesion compounds were carvacrol and thymol. Considering the role of biofilm in food spoilage and clinical diseases, inhibition of the initial phase of biofilm formation by natural antimicrobial agents may be an alternative to commonly used synthetic ones.
We report an evaluation of the effect of various combinations of pressures and times on the inact... more We report an evaluation of the effect of various combinations of pressures and times on the inactivation of norovirus (NoV) in two types of matrices that are important in NoV transmission: water and soft fruits. The human NoV surrogate murine norovirus was used as the model virus. The effect of HHP on the viral genome was evaluated by using RT real-time PCR (RT-qPCR), and infectivity assay was used to assess effects on the ability of the virus to attach to and replicate in cells. HHP treatments of 400 MPa for 2.5 min proved to be sufficient for efficient inactivation of NoV (>99.9% reduction). The efficacy of viral inactivation was highly dependent on the matrix in which the virus was present. Therefore, the effect of HHP should be carefully studied in all matrices to which HHP could potentially be applied. Finally, we found no consistent correlation between RT-qPCR and virus infectivity results, and consequently RT-qPCR is not a satisfactory tool for predicting risks to human health.
Celotna skupina genov za biosinteze oksitetraciklina (OTC) iz S. rimosus je že klonirana. Eden od... more Celotna skupina genov za biosinteze oksitetraciklina (OTC) iz S. rimosus je že klonirana. Eden od nacinov, da sa doloci vloga dolocenega gena is skupine genov za biosintezo OTC je, da se identificira metabolit ali metaboliti, katere producira rekombinantni sev, ki ima ta gen prekinjen (neaktiven). Procedura prekinitve otcD-ORF1 gena, domnevne ciklaze je bila izvedena v kromosomu bakterije S. rimosus. Predpostavljalo se je, da je domnevna ciklaza (otcD-ORF1) vpletena v zlaganje, ciklizacijo in aromatizacijo domnevne poliketidne verige v biosintezi OTC. Rekombinantni sev vec ni produciral OTC. Sev s prekinjenim otcD-ORF1 genom je produciral vecje stevilo novih spojin, ki jih prej ni bilo mogoce zaznati. Izkazalo se je, da posedujejo izolirane spojine 9, 15 in 17 namesto 19 ugljikovih atomov. Poznano je, da je funkcionalna enota PKS razreda II sestavljena iz treh do cestih enodelnih ali dvodelnih encimov, ki v ponavljajocih se ciklih katalizirajo sintezo poliketidne verige. Tako imenovani "chain length factor (CLF)" doloca dolžino verige poliketidne molekule. Nasi rezultati kažejo, da to le ni popolnoma tocno. Namrec, medsebojno delovanje encimov znotraj multi-encimskega kompleksa lahko bistveno vpliva na obliko konacnega produkta.
The capacity for the removal of pyrimethanil and fenhexamid, two fungicides commonly used for the... more The capacity for the removal of pyrimethanil and fenhexamid, two fungicides commonly used for the control of Botrytis cinerea in vineyards, has been evaluated during an alcoholic fermentation process in batch system. Commercial and wild strains of Saccharomyces cerevisiae were used. Batch fermentations were carried out in yeast extract-malt extract medium (YM) with 18.0 % (by mass) glucose, and the fungicides were added separately at three concentrations: 0.1, 1.0 and 10.0 mg/L. The removal capacity of yeast strains was also examined in stationary phase cultures of Saccharomyces cerevisiae. Stationary assays were performed with yeast biomass harvested from the stationary phase of an anaerobic fermentation process, with separate additions of 0.1, 1.0 and 10.0 mg/L of both fungicides. Removal studies with stationary phase cells were performed with viable and non-viable cells inactivated with sodium azide. This study clearly shows that both Saccharomyces cerevisiae strains were able to remove fenhexamid and pyrimethanil in stationary and fermentative assays. The removal potential is shown to be strain dependent in stationary but not in fermentative assays. However, the removal potential is dependent on the type of fungicide in both stationary and fermentative assays. In stationary phase cultures no significant difference in fungicide removal potential between viable and non-viable cells was observed, indicating that both pesticides were not degraded by metabolically active cells. However, the presence of both pesticides influenced fermentation kinetics and only pyrimethanil at 10.0 mg/L increased the production of volatile acidity of both strains.
The most important prerequisite for the application of PCR-based methods, among them the detectio... more The most important prerequisite for the application of PCR-based methods, among them the detection and quantifi cation of genetically modifi ed organisms (GMOs) is the ability to extract signifi cant amounts of DNA of adequate quality from the sample under investigation. The sample of interest in our work was soybean lecithin with expected low DNA content. The aim of this study was to set up a fast and effective HPLC (High Performance Liquid Chromatography) method using CIM ® (Convective Interaction Media, BIA Separations d.o.o., Ljubljana, Slovenia) DEAE (DiEthylAminoEthyl) anion-exchange disk monolithic columns (disks) for the isolation of DNA from soybean lecithin samples. As the reference isolation procedure we used CTAB (CethylTrimethylAmmonium Bromide) method, which is widely used in GMO detection. It was demonstrated, that CIM ® DEAE disks allow effi cient isolation of DNA from soybean lecithin. Furthermore, in comparison with the CTAB method, the method was less time-consuming and reduced the use of some aggressive chemicals. The quality of isolated DNA was tested with spectrophotometric analysis, agarose gel electrophoresis and by amplifi cation of soybean specifi c lectin gene with qualitative and real-time PCR. The isolated soybean DNA was of adequate quantity and quality for PCR analysis, even though mostly degraded, present in small amounts and contaminated with some impurities, among them potential PCR inhibitors. The study expanded the applicability of monolithic columns in the isolation of biomolecules from highly processed food materials and their potential use for nucleic acids detection.
The aim of this study was to assess the potential of bacteria Escherichia coli ATCC 35218, Pseudo... more The aim of this study was to assess the potential of bacteria Escherichia coli ATCC 35218, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923 and yeast Pichia membranifaciens ZIM 2417 to adhere to wooden surfaces such as poplar (Populus sp.), Norway spruce (Picea abies), European beech (Fagus sylvatica), beech coated with the commercial Belinka oil food contact and disinfectant P3-oxonia active 150, and investigate their survival on the beech wood surface under different relative humidities (RH; 65%, 75%, 85%, 98%) and temperatures (10 °C, 20 °C, 27 °C/37 °C). To extend the research goals, the scanning electron microscopy (SEM) analysis was also performed. The adhesion was determined by the number of colony-forming units per mm 2 of sample (CFU/mm 2 ). Results showed that all tested bacteria and yeast were able to adhere to the wooden surfaces, although differences were observed according to strains and type of wood. It was evident that number of adhered cells of S. aureus was lower on spruce (3.62 × 10 3 CFU/mm 2 ) compared to poplar and beech (1.09 × 10 5 and 2.11 × 10 4 CFU/mm 2 , respectively). Furthermore, oil and disinfectant promoted the adhesion of P. aeruginosa (155.93 and 130.50%, respectively) on the beech surfaces, while they had a strong inhibitory effect on the other tested microorganisms E. coli (87.44 and 88.44%, respectively), S. aureus (91.24 and 96.80%, respectively) and P. membranifaciens (92.45 and 87.24%, respectively). These findings are consistent with SEM micrographs. The current data also indicated that relative humidity and temperature significantly affected the adhesion of tested bacteria and yeast. The highest degree of adhesion was observed at a relative humidity of 98% and temperature of 20 and 37 °C for bacteria, or 20 and 27 °C for yeast. Thus, the knowledge of how these microorganisms adhere to wooden surfaces and which factors affect this phenomenon proves to be of great importance in order to avoid their colonization.
Apple pomace consists of a press cake resulting from pressing apples for various juices as well a... more Apple pomace consists of a press cake resulting from pressing apples for various juices as well as from other fruit industry wastes. In general it is an acid substrate with a considerably buffering capacity, rich in carbohydrates, and low in protein content. A rapid spoilage caused by microorganisms can start because of a high moisture content of fresh pomace. Suitable preservation methods should be applied, otherwise apple pomace has to be utilized as soon as it is produced. The best approach for disposing of apple pomace is its conversion to some useful products. Such conversion can be done by: — biological methods (solid state fermentation) — non biological methods (pyrolysis, drying, extraction)
PurposeThe main objective of this study is to find out how food handlers in catering establishmen... more PurposeThe main objective of this study is to find out how food handlers in catering establishments perceive ensuring food safety and which problems they meet along the way.Design/methodology/approachUsing a qualitative approach, ten food handlers in Slovenian catering facilities were included in the case study. A semi-structured approach was applied to provide a deeper insight into food safety barriers perceived by respondents. Participants first read short fictitious newspaper news about a foodborne disease at a tourist farm, which served as a starting point.FindingsThe results demonstrate barriers which most often originate in a lack of knowledge (e.g. improper food safety training, incorrect food safety knowledge testing, knowledge and maintaining of CCPs), shortage of food hygiene skills (e.g. handwashing, food defrosting) and weak work satisfaction (e.g. insufficient payment, poor interpersonal relationships and weak motivation). Food safety knowledge and consequently training methods were found to be the biggest barrier for the efficiency of the HACCP system in practice.Research limitations/implicationsDue to the small sample, the results cannot be generalised to the entire population of food handlers in Slovenia.Practical implicationsThe results indicate weaknesses in food safety knowledge among professional food handlers.Originality/valueThe study provides a deeper insight into implicit opinions of ten food handlers in catering facilities regarding barriers in providing food safety, their knowledge and behaviour in their work with food.
A serious global problem with the increasing resistance of microorganisms to currently used antim... more A serious global problem with the increasing resistance of microorganisms to currently used antimicrobials has opened up the promotional research in the identification of new, more effective drugs with a broad spectrum of antimicrobial activities. Plant essential oils, due to the large biological and structural diversity of their components, are known to have many potential benefits. This study aimed to evaluate the antimicrobial and anti-adhesion activity of fifteen essential oils and their compounds against two bacterial and two yeast species responsible for food spoilage and infectious diseases. Antimicrobial activity was determined by testing the minimum inhibitory concentration (MIC), the minimum bactericidal concentration (MBC) and the minimum fungicidal concentration (MFC) of essential oils and compounds. The essential oils of Cinnamomum zeylanicum and Eugenia caryophyllus showed the highest antimicrobial activity with MICs ranging from 0.078 to 1.25 mg/mL, and 0.039 to 1.25 mg/mL, respectively. On the other hand, essential oils of Eucalypti aetheroleum and Salvia officinalis had significantly weaker antimicrobial properties than the others. Further, MICs were used to assess the inhibition of adhesion of bacteria Salmonella Typhimurium ATCC 25923 and Staphylococcus aureus ATCC 14208, and yeasts Candida albicans ATCC 10231 and Saccharomyces cerevisiae ATCC 9763 in a microtiter plate using the crystal violet staining method. Based on the percentage of adhesion inhibition, yeast S. cerevisiae ATCC 9763 showed a high level of antimicrobial resistance. E. caryophyllus had the strongest effect with inhibition up to 73%. Consistent with the antimicrobial susceptibility results, the most active anti-adhesion compounds were carvacrol and thymol. Considering the role of biofilm in food spoilage and clinical diseases, inhibition of the initial phase of biofilm formation by natural antimicrobial agents may be an alternative to commonly used synthetic ones.
We report an evaluation of the effect of various combinations of pressures and times on the inact... more We report an evaluation of the effect of various combinations of pressures and times on the inactivation of norovirus (NoV) in two types of matrices that are important in NoV transmission: water and soft fruits. The human NoV surrogate murine norovirus was used as the model virus. The effect of HHP on the viral genome was evaluated by using RT real-time PCR (RT-qPCR), and infectivity assay was used to assess effects on the ability of the virus to attach to and replicate in cells. HHP treatments of 400 MPa for 2.5 min proved to be sufficient for efficient inactivation of NoV (>99.9% reduction). The efficacy of viral inactivation was highly dependent on the matrix in which the virus was present. Therefore, the effect of HHP should be carefully studied in all matrices to which HHP could potentially be applied. Finally, we found no consistent correlation between RT-qPCR and virus infectivity results, and consequently RT-qPCR is not a satisfactory tool for predicting risks to human health.
Celotna skupina genov za biosinteze oksitetraciklina (OTC) iz S. rimosus je že klonirana. Eden od... more Celotna skupina genov za biosinteze oksitetraciklina (OTC) iz S. rimosus je že klonirana. Eden od nacinov, da sa doloci vloga dolocenega gena is skupine genov za biosintezo OTC je, da se identificira metabolit ali metaboliti, katere producira rekombinantni sev, ki ima ta gen prekinjen (neaktiven). Procedura prekinitve otcD-ORF1 gena, domnevne ciklaze je bila izvedena v kromosomu bakterije S. rimosus. Predpostavljalo se je, da je domnevna ciklaza (otcD-ORF1) vpletena v zlaganje, ciklizacijo in aromatizacijo domnevne poliketidne verige v biosintezi OTC. Rekombinantni sev vec ni produciral OTC. Sev s prekinjenim otcD-ORF1 genom je produciral vecje stevilo novih spojin, ki jih prej ni bilo mogoce zaznati. Izkazalo se je, da posedujejo izolirane spojine 9, 15 in 17 namesto 19 ugljikovih atomov. Poznano je, da je funkcionalna enota PKS razreda II sestavljena iz treh do cestih enodelnih ali dvodelnih encimov, ki v ponavljajocih se ciklih katalizirajo sintezo poliketidne verige. Tako imenovani "chain length factor (CLF)" doloca dolžino verige poliketidne molekule. Nasi rezultati kažejo, da to le ni popolnoma tocno. Namrec, medsebojno delovanje encimov znotraj multi-encimskega kompleksa lahko bistveno vpliva na obliko konacnega produkta.
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