Development of fish-based model systems with various microstructures

Verheyen, Davy; Baka, Maria; Glorieux, Seline; Duquenne, Barbara; Fraeye, Ilse; Skåra, Torstein; Impe, Jan Van

doi:10.1016/j.foodres.2017.12.047

Cited by 12 publications

(35 citation statements)

References 44 publications

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“…In general, the growth morphologies of L. monocytogenes in the different model systems, as assumed by Verheyen et al (22,31) for the macroscopic growth experiments, were more simplistic than those observed in the microscopic images in the present study. L. monocytogenes often appeared as a combination of single cells, small aggregates and microcolonies varying in size, in contrast to the more simple classification that was previously assumed, i.e., growth of single cells in the liquid system and submerged microcolony growth in the xanthan, emulsion system, aqueous gel, and gelled emulsion system.…”

Section: Discussioncontrasting

confidence: 43%

“…Growth morphology. Verheyen et al (22,31) made a number of assumptions concerning the growth morphology of the L. monocytogenes strain cocktail (consisting of LMG 23773, LMG 23774, and LMG 26484) in the investigated fish-based model systems with various microstructures, i.e., liquid, xanthan, aqueous gel, emulsion (1% fat), and gelled emulsion (1% fat). First of all, it was assumed that L. monocytogenes grew as single cells in the liquid system, although potential cell sedimentation due to the static nature of the growth experiments was also suggested.…”

Section: Discussionmentioning

confidence: 99%

“…Preferred phase for cell growth. Verheyen et al (22,31) assumed that the aqueous phase was the preferred phase for cell growth in the emulsion and gelled emulsion systems. However, Fig.…”

Section: Discussionmentioning

confidence: 99%

“…One approach that allows inclusion of the food microstructural influence into predictive models, is to conduct microbiological experiments in food model systems with various microstructures (28)(29)(30)(31). Wilson et al (26) defined five categories of food microstructures: liquids, emulsions, aqueous gels, gelled emulsions, and surfaces.…”

mentioning

confidence: 99%

“…These unwanted variations were caused by the presence or absence of fat and gelling agents in some of the systems, a consequence of developing representative model systems for each microstructure. For this reason, Verheyen et al (31) developed model systems with various microstructures, among which the microstructural effect was isolated by means of minimal variation in compositional and physicochemical aspects. The set of model systems consisted of three viscous systems and two gelled systems, i.e., (i) a liquid system; (ii) xanthan, a more viscous liquid system containing a small concentration of xanthan gum; (iii) an emulsion; (iv) an aqueous gel; and (v) a gelled emulsion, respectively.…”

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confidence: 99%

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Food Microstructure and Fat Content Affect Growth Morphology, Growth Kinetics, and Preferred Phase for Cell Growth of Listeria monocytogenes in Fish-Based Model Systems

Verheyen

Govaert

et al. 2019

Appl Environ Microbiol

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Food microstructure significantly affects microbial growth dynamics, but knowledge concerning the exact influencing mechanisms at a microscopic scale is limited. The food microstructural influence on Listeria monocytogenes (green fluorescent protein strain) growth at 10°C in fish-based food model systems was investigated by confocal laser scanning microscopy. The model systems had different microstructures, i.e., liquid, xanthan (high-viscosity liquid), aqueous gel, and emulsion and gelled emulsion systems varying in fat content. Bacteria grew as single cells, small aggregates, and microcolonies of different sizes (based on colony radii [size I, 1.5 to 5.0 μm; size II, 5.0 to 10.0 μm; size III, 10.0 to 15.0 μm; and size IV, ≥15 μm]). In the liquid, small aggregates and size I microcolonies were predominantly present, while size II and III microcolonies were predominant in the xanthan and aqueous gel. Cells in the emulsions and gelled emulsions grew in the aqueous phase and on the fat-water interface. A microbial adhesion to solvent assay demonstrated limited bacterial nonpolar solvent affinities, implying that this behavior was probably not caused by cell surface hydrophobicity. In systems containing 1 and 5% fat, the largest cell volume was mainly represented by size I and II microcolonies, while at 10 and 20% fat a few size IV microcolonies comprised nearly the total cell volume. Microscopic results (concerning, e.g., growth morphology, microcolony size, intercolony distances, and the preferred phase for growth) were related to previously obtained macroscopic growth dynamics in the model systems for an L. monocytogenes strain cocktail, leading to more substantiated explanations for the influence of food microstructural aspects on lag phase duration and growth rate. IMPORTANCE Listeria monocytogenes is one of the most hazardous foodborne pathogens due to the high fatality rate of the disease (i.e., listeriosis). In this study, the growth behavior of L. monocytogenes was investigated at a microscopic scale in food model systems that mimic processed fish products (e.g., fish paté and fish soup), and the results were related to macroscopic growth parameters. Many studies have previously focused on the food microstructural influence on microbial growth. The novelty of this work lies in (i) the microscopic investigation of products with a complex composition and/or structure using confocal laser scanning microscopy and (ii) the direct link to the macroscopic level. Growth behavior (i.e., concerning bacterial growth morphology and preferred phase for growth) was more complex than assumed in common macroscopic studies. Consequently, the effectiveness of industrial antimicrobial food preservation technologies (e.g., thermal processing) might be overestimated for certain products, which may have critical food safety implications.

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Section: Discussioncontrasting

confidence: 43%

Section: Discussionmentioning

confidence: 99%

“…Preferred phase for cell growth. Verheyen et al (22,31) assumed that the aqueous phase was the preferred phase for cell growth in the emulsion and gelled emulsion systems. However, Fig.…”

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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confidence: 99%

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