Biomedical subjects

F Devlieghere

Publications and source records attributed to F Devlieghere.

44 records · Page 3Linked to original sources

PubMed2001

A combination of high oxygen atmosphere and equilibrium modified atmosphere packaging to improve the keeping quality of red fruits.

When high-barrier material is used to package fresh whole fruit in high oxygen atmospheres, shelf life is limited due to the accumulation of its produced CO2 and its creation of an anaerobic atmosphere. In this study, the effect of the combination of High Oxygen Atmosphere and Equilibrium Modified Atmosphere Packaging was tested on the shelf life of two non-climacteric red fruits, particularly strawberries and raspberries, at 7 degrees C. Herefor, the following packaging systems are compared: the conventional method of packaging in a macroperforated high-barrier film (air conditions) (1), Equilibrium Modified Atmosphere (EMA, i.e. 3-5% O2 and 5-10% CO2-balance N2) (2) and two novel modified atmospheres: High Oxygen Atmosphere (HOA, i.e. > 70% O2-balance N2) in a high-barrier film (3) and HOA in a EMA film with an adjusted film permeability (4). The shelf life of the fruits was determined by evaluating the evolution of the internal oxygen, carbon dioxide and ethylene concentrations in the packages, the microbial and sensorial quality during the storage, the loss of weight due to transpiration and respiration of the fruit and the loss of marketable fruit due to visual decay or to Botrytis growth. The High Oxygen Atmosphere in the EMA film re-established after five days to an equilibrium of 3% O2 and 5% CO2. The High Oxygen Atmosphere in the high-barrier film remained high during the first five days of storage, but decreased then rapidly to anaerobic conditions, resulting in off-flavours and odours. To avoid an accumulation of ethylene inside the high-barrier package, an ethylene adsorbing monolayer was added. Shelf life of strawberries and raspberries, packed in air conditions, was limited by growth of moulds and yeasts, rather than by sensorial unacceptance. On the other hand, sensorial properties limited the shelf life of the fruits packed under modified atmosphere. Especially High Oxygen Atmosphere improved the microbial quality, due to the inhibiting effect on yeasts and moulds. However, when oxygen was depleted and carbon dioxide had accumulated, sensorial quality (odour, taste andfirmness) was deteriorated. As this is not the case with high O2 in an EMA film, the latter can be assumed as a promising configuration for respiring fresh produce, combining the beneficial effect of high O2 and EMAP.

Bacteria↗

PubMed2000

Isolation and identification of tetracycline resistant lactic acid bacteria from pre-packed sliced meat products.

In recent years, the food chain has been recognised as one of the main routes for transmission of antibiotic resistant bacteria between the animal and human population. In this regard, the current study aimed to investigate if tetracycline resistant (tetR) lactic acid bacteria (LAB) are present in ready-to-eat modified atmosphere packed (MAP) sliced meat products including fermented dry sausage, cooked chicken breast meat and cooked ham. From population graphs based on doubling tetracycline concentrations between 0 and 256 microg ml(-1), only fermented dry sausage was shown to contain a high-level retR LAB population (5.10(1) - 2,23.10(4) CFU/g), and this in four out of ten examined sausages. From these four positive sausages, a total of 100 strains were isolated on de Man, Rogosa and Sharpe-sorbic acid (MRS-S) agar without tetracycline (n = 45) and on MRS-S agar supplemented with a tetracycline breakpoint concentration of 64 microg ml(-1) (n = 55). Using resistance histograms derived from the disc diffusion method, all these strains were grouped as sensitive to rifampicin, erythromycin and ampicillin. All strains from the tetracycline-containing MRS-S plates were resistant to tetracycline. Identification with whole-cell protein profiling revealed that the total strain set represented four different species: Pediococcus pentosaceus, Lactobacillus plantarum, Lactobacillus sakei subsp. carnosus and Lactobacillus curvatus. All species are commonly associated with fermented dry sausage, either as starter culture or as natural contaminants. The latter three species were found to comprise all tetracycline resistant strains. To our knowledge, this is the first report providing evidence for the presence of tetR LAB in final ready-to-eat pre-packed fermented dry sausages.

Food Microbiology↗

PubMed1999

Shelf life of modified atmosphere packed cooked meat products: a predictive model.

The effect of temperature, concentration of dissolved CO2 and water activity on the growth of Lactobacillus sake was investigated by developing predictive models for the lag phase and the maximum specific growth rate of this specific spoilage organism for gas-packed cooked meat products. Two types of predictive model were compared: an extended Ratkowsky model and a response surface model. In general, response surface models showed a slightly better correlation, but the response surface model for the maximum specific growth rate showed illogical predictions at low water activities. The concentration of dissolved CO2 proved to be a significant independent variable for the maximum specific growth rate as well as for the lag phase of L. sake. Synergistic actions on the shelf life-extending effect were noticed between temperature and dissolved CO2, as well as between water activity and dissolved CO2. The developed models were validated by comparison with the existing model of Kant-Muermans et al. (1997) and by means of experiments in gas-packed cooked meat products. Both developed models proved to be useful in the prediction of the microbial shelf life of gas-packed cooked meat products.

Animals↗

PubMed1999

Behavior of Listeria monocytogenes and Aeromonas spp. on fresh-cut produce packaged under equilibrium-modified atmosphere.

Storage experiments were conducted to follow the behavior of pathogens on fresh-cut vegetables (trimmed brussels sprouts, grated carrots, shredded iceberg lettuce, and shredded chicory endives) packaged under an equilibrium-modified atmosphere (EMA) (2 to 3% O2, 2 to 3% CO2, and 94 to 96% N2) and stored at 7 degrees C. As a comparison, fresh-cut vegetables were also packaged in a perforated high-barrier film (air conditions) and stored at 7 degrees C. In a first step, the shelf life of the vegetables in the two kinds of packages was determined by evaluating the microbiological quality as well as the sensorial quality (appearance, taste, and odor). In general, sensorial properties were faster in limiting the shelf life than microbiological criteria. The shelf life of the vegetables stored under an EMA was extended by 50% or more, compared with the air-stored vegetables. In a second storage experiment, the four fresh-cut vegetables were inoculated with a cocktail of psychrotrophic pathogens (Listeria monocytogenes, Aeromonas caviae [HG4]) and A. bestiarum (HG2) before packaging under an EMA and air at 7 degrees C. The inoculated pathogens were more influenced by the type of vegetable than by the type of atmosphere. No growth was detected on the brussels sprouts or on carrots (L. monocytogenes). Aeromonas spp. had a higher growth rate than L. monocytogenes on the shredded chicory endives and shredded iceberg lettuce at 7 degrees C.

Aeromonas↗

PubMed1998

Concentration of carbon dioxide in the water-phase as a parameter to model the effect of a modified atmosphere on microorganisms.

The effect of modified atmosphere packaging can mainly be attributed to the bacteriostatic action of CO2. The dissolved CO2 in the water-phase of a food product is strongly dependent on several intrinsic and extrinsic parameters and will determine the effectiveness of a modified atmosphere packaging configuration. The effect of pH, gas/product ratio, initial %CO2 in the gas-phase, lard content and storage temperature on the amount of dissolved CO2 was screened in a preliminary experiment. The initial CO2-concentration in the gas-phase and the gas/product ratio turned out to be the two major factors determining the amount of dissolved CO2. The initial pH also determined significantly the final CO2-concentration in the broth. Temperature and lard content were shown to have only a minor effect on the amount of dissolved CO2 compared to the above mentioned parameters. This demonstrates the importance of the packaging configuration in the effectiveness of a modified atmosphere. In a second step, a model was constructed to predict the amount of dissolved carbon dioxide in modified BHI-broth as a function of the gas/product ratio, the initial CO2-concentration and the temperature by means of Response Surface Methodology (RSM). A second equation was also derived based on Henry's law and was shown to be a powerful tool in the quantification of the effect of intrinsic and extrinsic parameters on the CO2-solubility in food products. The possibility of the use of the concentration of dissolved CO2 in the water-phase as a determinative factor for the inhibitory effect of modified atmospheres was examined on Pseudomonas fluorescens. Growth curves at 7 degrees C of P. fluorescens in different packaging configurations (initial %CO2 and gas/product ratio) resulting in equal amounts of dissolved CO2 were compared. P. fluorescens was shown to be similarly inhibited by equal amounts of dissolved CO2-concentrations, independent of the packaging configuration. This demonstrates the potential of the application of the concentration of dissolved CO2 in the water-phase as a parameter to characterise a modified atmosphere and its inhibition of certain microorganisms.

Carbon Dioxide↗

PubMed1998

Effect of dissolved carbon dioxide and temperature on the growth of Lactobacillus sake in modified atmospheres.

Carbon dioxide is known to be the active gas in modified atmosphere packaging. However, only the dissolved part of the CO2 will be active in the inhibition of microorganisms. When the effect of a modified atmosphere on the growth of microorganisms is modeled, the amount of dissolved CO2 should be the parameter to evaluate the effect of CO2 in modified atmospheres. Lactobacillus sake was isolated from cooked ham, identified and was chosen as a representative organism for the spoilage of modified atmosphere packed cooked meat products. In a first step a suitable liquid simulation medium for cooked meat products was selected. The growth rate of L. sake was significantly higher in modified MRS than in cooked ham, while no significant difference was observed between the growth parameters of L. sake in modified BHI and in cooked ham. Careful evaluation of the applied simulation medium was shown to be essential before application to the development of predictive models for nutrient demanding microorganisms such as lactic acid bacteria. In a second step, the influence of dissolved CO2 and the storage temperature on the growth parameters of L. sake was modeled. Temperature was shown to have a major effect on the growth rate and lag phase of L. sake. Carbon dioxide negatively influenced the growth rate of L. sake. A negative, linear relationship was observed between the growth rate and the amount of dissolved carbon dioxide. Carbon dioxide was shown, however, to have no significant effect on the lag phase of L. sake. A significant interaction term between temperature and dissolved CO2 on the growth rate of L. sake was established.

Carbon Dioxide↗

PubMed1998

Evaluation of recycled HDPE milk bottles for food applications.

The possibilities of recycling milk-contaminated HDPE were investigated. Bottles were blown of respectively untreated, caustic-washed and caustic-washed/steam-stripped/air-dried recycled material. The migration characteristics of the different bottles were compared using various food simulants, as well as their sensorial and mechanical properties. From the analytical and sensorial experiments, it was shown that the untreated and caustic-washed recycled material could not be considered as a food packaging material. A high number of compounds able to migrate were detected, causing an off-flavour which could easily be recognized. The steam-stripped recycled material however, seemed to perform almost as well as its corresponding virgin material. Only low amounts of compounds able to migrate could be detected, resulting in a packaging material characterized by excellent sensorial properties which could not be distinguished from its virgin material. Furthermore it was proved that the mechanical properties of the recycled material did not change during the recycling process.

Air↗

PubMedDate not supplied

Evaluation, modelling and optimization of the cleaning process of contaminated plastic food refillables.

In this study several types of bottle materials (glass, PET (polyethylene terephthalate), PC (polycarbonate), HDPE (high density polyethylene), PP (polypropylene) and PVC (polyvinyl chloride)) were evaluated in order to be used as food refillables, comparing the residual chemical contamination after classical caustic washing. Bottles were contaminated with model chemicals (chloroxylenol and d-limonene) and caustic washed with varied process parameters using a simulated laboratory-scale washing procedure. After washing, the chemical-contaminated bottles were filled with water and stored for 28 days at 37 degrees C. The concentrations of the model chemicals in the water after storage were taken as a measure of chemical contamination. The influence of the cleaning parameters (temperature, caustic and commercial additive concentration) was studied using response surface methodology. Washing temperature showed a significant influence on the removal of absorbed chemicals from surfaces compared with the effect of the caustic and especially the additive concentration. Optimization of caustic cleaning for the cleaning process in question led to better cleaning effectiveness, although none of the different washing conditions were able to remove all absorbed chemicals out of the polymeric resins. Commercially available plastic refillables (PET and PC) showed the best chemical rinsability. Glass bottles, however, had in every case the best rinsing characteristics.

Conservation of Natural Resources↗