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Frank Devlieghere

Publications and source records attributed to Frank Devlieghere.

16 recordsLinked to original sources
PubMed2006

Growth kinetics of cultures from single spores of Aspergillus flavus and Fusarium verticillioides on yellow dent corn meal.

A dilution protocol originally developed for the isolation of single bacterial cells was modified to suite the specificities of fungal growth. The modified protocol was used to study the growth kinetics of single spores of Aspergillus flavus and Fusarium verticillioides on yellow dent corn meal. Both a(w) and temperature significantly influenced the distributions of the colony growth rates and lag phases and the rate at which individual spores of both isolates completed the lag period. An interaction between a(w) and temperature was noted on the spread of the distributions of these growth parameters. The histograms of the single spore colony growth rates and lag phases generally became wider the more compromising the conditions for growth became, indicating a greater variation in growth ability at these conditions. The rate at which the single spores passed through the lag phases generally decreased with decrease in temperature and/or a(w), with an interaction again noted between these two factors on the rate. These results show the potential range and variability in growth of individual fungal spores at the lowest inoculum level possible.

Aspergillus flavus↗
PubMed2006

Standardisation of methods for assessing mould germination: a workshop report.

The first workshop on predictive mycology was held in Marseille, France, 2--4 February 2005 under the auspices of the French Microbiological society. The purpose of the workshop was to list the different techniques and definitions used by scientists for assessing mould germination and to evaluate the influence of the different techniques on the experimental results. Recommendations were made when a large consensus was obtained. In order to facilitate the study of germination, alternative methods to microscopic examination were examined.

Food Microbiology↗
PubMed2006

The efficacy of electrolysed oxidising water for inactivating spoilage microorganisms in process water and on minimally processed vegetables.

The efficacy of Electrolysed Oxidising Water (EOW) for inactivating spoilage microorganisms in process water and on minimally processed vegetables was investigated. The direct effect of EOW on three important spoilage bacteria namely; Pseudomonas fluorescens, Pantoea agglomerans or Rahnella aquatilis was determined by inoculating tap water or "artificial process water" with approximately 8 log CFU/ml pure culture and electrolysing the resultant solutions. The three bacteria were each reduced to undetectable levels at low (0.5 A) and relatively higher levels (1.0 A) of current in tap water and "artificial process water", respectively. The residual effect of EOW on P. fluorescens, P. agglomerans or R. aquatilis was determined by incubating at room temperature 1 ml (approximately 9 log CFU/ml) pure culture suspensions in 9 ml of EOW-T (EOW produced from tap water), EOW-A (EOW produced from "artificial process water" supplemented with approximately 60.7 mg Cl(-)/l and 39.3 mg Na(+)/l) or deionised water (control) for 0, 15, 45 or 90 min. The bactericidal activity of both EOW-T and EOW-A increased with the concentration of free oxidants and incubation period and the three bacteria were completely reduced at free oxidants-incubation period combinations of 3.88 mg/l-45 min and 5.1 mg/l-90 min in EOW-T and EOW-A, respectively. Two types of industrial vegetable process water; salad-mix and soup process water, which had each a total psychrotrophic count of approximately 8 log CFU/ml were then electrolysed. Without any NaCl addition, only 1.2 and 2.1 log reductions of the psychrotrophs in soup and salad-mix process water was attained respectively. Supplementation of the process water with approximately 60.7 mg Cl(-)/l and 39.3 mg Na(+)/l afterwards resulted in complete reduction of the psychrotrophic count in both process waters, but soup process water required relatively higher levels of current compared to salad-mix water. Finally, fresh-cut lettuce was washed in EOW-T containing 3.62 mg free oxidants/l, EOW-IP (EOW produced from industrial process water) containing 2.8 mg free oxidants/l or tap water (control) for 1 or 5 min. Washing the vegetables for 1 min in EOW-T resulted in 1.9, 1.2, and 1.3 log reductions of psychrotrophs, lactic acid bacteria and Enterobacteriacae, respectively, which increased to 3.3, 2.6, and 1.9 log reductions after washing for 5 min instead. EOW-IP tested in this work had no bactericidal effect on the microflora of fresh-cut lettuce. Electrolysis could therefore be used to decontaminate process water for vegetable pre-washing and to sanitise tap water for final rinsing of vegetables, respectively.

Colony Count, Microbial↗
PubMed2006

Influence of experimental parameters on the fluorescence response and recovery of the high-performance liquid chromatography analysis of fumonisin B1.

The effect of mobile phase pH, column temperature, extraction method and derivatisation time on the fluorescence response and recovery of fumonisin B1 in corn was investigated. Column temperature and mobile phase pH were negatively and positively correlated with the fluorescence response, respectively. Use of an Ultraturrax blender for extraction resulted in higher FB1 recoveries compared to a rotary shaker. In contrast to other reports, maximum fluorescence response occurred after a derivatisation time of 8 min. These results reflect on the absolute requirement for standardisation of the aforementioned parameters.

Chromatography, High Pressure Liquid↗
PubMed2006

Occurrence of patulin in organic, conventional, and handcrafted apple juices marketed in Belgium.

The aim of this research was to compare the occurrence of patulin in a large group of organic, conventional, and handcrafted apple juices marketed in Belgium. An analytical procedure based on high-performance liquid chromatography with UV detection was validated and used to analyze 177 apple juice samples: 65 organic, 90 conventional, and 22 handcrafted. Patulin was detected in 22 samples (12%), and quantification was possible in 10 (6%) of these samples. The patulin content was higher than the European legal limit of 50 microg/liter in two samples of organic apple juice. Although, the incidence of patulin in organic (12%), conventional (13%), and handcrafted (10%) apple juices was not significantly different (P = 0.863), the mean concentration of patulin in contaminated samples was significantly higher in organic (43.1 microg/liter) than in conventional (10.2 microg/liter) (P = 0.02) and handcrafted (10.5 microg/liter) (P = 0.037) apple juice. The highest patulin concentrations were found in the most expensive apple juices because of the higher price of organic apple juice. This relation was not observed when only conventional apple juices were analyzed.

Agriculture↗
PubMed2004

Concepts and tools for predictive modeling of microbial dynamics.

Description of microbial cell (population) behavior as influenced by dynamically changing environmental conditions intrinsically needs dynamic mathematical models. In the past, major effort has been put into the modeling of microbial growth and inactivation within a constant environment (static models). In the early 1990s, differential equation models (dynamic models) were introduced in the field of predictive microbiology. Here, we present a general dynamic model-building concept describing microbial evolution under dynamic conditions. Starting from an elementary model building block, the model structure can be gradually complexified to incorporate increasing numbers of influencing factors. Based on two case studies, the fundamentals of both macroscopic (population) and microscopic (individual) modeling approaches are revisited. These illustrations deal with the modeling of (i) microbial lag under variable temperature conditions and (ii) interspecies microbial interactions mediated by lactic acid production (product inhibition). Current and future research trends should address the need for (i) more specific measurements at the cell and/or population level, (ii) measurements under dynamic conditions, and (iii) more comprehensive (mechanistically inspired) model structures. In the context of quantitative microbial risk assessment, complexity of the mathematical model must be kept under control. An important challenge for the future is determination of a satisfactory trade-off between predictive power and manageability of predictive microbiology models.

Bacteria↗
PubMed2002

Effect of superatmospheric oxygen packaging on sensorial quality, spoilage, and Listeria monocytogenes and Aeromonas caviae growth in fresh processed mixed salads.

Atmospheres with O2 levels higher than 70 kPa have recently been suggested as an innovation to modified atmosphere packaging (MAP) for fresh processed vegetables to maintain sensory quality and safety. In the present work, mixed vegetable salad collected from a commercial processing plant and stored with the MAP technique was studied. Two gas mixtures were actively generated by using an initial O2 concentration of 95 kPa and combined with two plastic films. The low-barrier film permeability for O2 was 1,629 mlO2/m2 x 24 h x atm with 30 microm of thickness (Hyplast, Hoogstraten, Belgium) and the O2 permeability of the high-barrier film was 2 mlO2/m2 x 24h x atm with 150 microm of thickness (Euralpack, Wommelgen, Belgium) at 23 degrees C. As control, active conventional MAP with application of 3 to 5 kPa of O2 and 6 to 8 kPa of CO2 was used. Packaged salads were stored up to 8 days at 4 degrees C and at temperatures simulating chilled distribution chain conditions. Microbial safety and sensory quality, as well as the survival of inoculated Listeria monocytogenes and Aeromonas caviae, were monitored. The effect of superatmospheric O2 on the growth of aerobic microflora was variable. Under superatmospheric conditions, lactic acid bacteria and members of Enterobacteriaceae were inhibited. Nevertheless, growth of yeast and A. caviae seem to be stimulated by superatmospheric O2, whereas growth of psychrotrophic bacteria and L monocytogenes was not affected. The overall visual appearance (mainly color) of the mixed vegetable salads was better maintained and the shelf life prolonged when packaged under O2 concentrations greater than 50 kPa.

Aeromonas↗