期刊
INTERNATIONAL JOURNAL OF FOOD MICROBIOLOGY
卷 208, 期 -, 页码 75-83出版社
ELSEVIER
DOI: 10.1016/j.ijfoodmicro.2015.05.011
关键词
Refrigeration temperature; Growth morphology; Surface colony; Immersed colony; Planktonic cells; Solid food structure; Microbial interaction
资金
- (Center of Excellence OPTEC-Optimization in Engineering) of the KU Leuven Research Council [PFV/10/002]
- Fund for Scientific Research-Flanders [G093013N]
- Belgian Program on Interuniversity Poles of Attraction (IAP Phase VII - 19 DYSCO)
- Belgian Federation for Chemistry and Life Sciences Industries (essenscia)
Predictive microbiology has recently acknowledged the impact of the solid(like) food structure on microbial behavior. The presence of this solid(like) structure causes microorganisms to grow as colonies and no longer planktonically as in liquid. In this paper, the growth dynamics of Salmonella Typhimurium and Escherichia coli were studied as a function of temperature, considering different growth morphologies, i.e., (i) planktonic cells, (ii) immersed colonies and (iii) surface colonies. For all three growth morphologies, both microorganisms were grown in petri dishes. While Escherichia coli was grown under optimal pH and water activity (a(w)), for S. Typhimurium pH and a(w) were adapted to 5.5 and 0.990. In order to mimic a solid(like) environment, 5% (w/v) gelatin was added. All petri dishes were incubated under static conditions at temperatures in the range [8.0 degrees C-22.0 degrees C]. Cell density was determined via viable plate counting. This work demonstrates that the growth morphology (planktonic vs. colony) has a negligible effect on the growth dynamics as a function of temperature. The observation of almost equal growth rates for planktonic cultures and colonies is in contrast to literature where, mostly, a difference is observed, i.e., mu(planktonic) (cells) >= mu(immersed) (colonies) >= mu(surface) (colonies). This difference might be due to shaking of the liquid culture in these studies, which results in a nutrient and oxygen rich environment, in contrast to the diffusion-limited gel system. Experiments also indicate that lag phases for solid(like) systems are similar to those for the planktonic cultures, as can be found in literature for similar growth conditions. Considering the maximum cell density, no clear trend was deducted for either of the microorganisms. This study indicates that the growth parameters in the suboptimal temperature range do not depend on the growth morphology. For the considered experimental conditions, models previously developed for liquid environments can be used for solid(like) systems. (C) 2015 Elsevier B.V. All rights reserved.
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