Growth/no-growth models of in-vitro growth of Penicillium paneum as a function of thyme essential oil, pH, aw, temperature

Els Debonne; An Vermeulen; Filip Van Bockstaele; Irena Soljic; Mia Eeckhout; Frank Devlieghere

doi:10.1016/j.fm.2019.04.003

Growth/no-growth models of in-vitro growth of Penicillium paneum as a function of thyme essential oil, pH, a_w, temperature

Food Microbiol. 2019 Oct:83:9-17. doi: 10.1016/j.fm.2019.04.003. Epub 2019 Apr 8.

Authors

Els Debonne¹, An Vermeulen², Filip Van Bockstaele³, Irena Soljic², Mia Eeckhout⁴, Frank Devlieghere⁵

Affiliations

¹ Laboratory of Applied Mycology (MYCOLAB), Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Valentin Vaerwyckweg 1, 9000 Ghent, Belgium; Research Unit of Cereal and Feed Technology, Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Valentin Vaerwyckweg 1, 9000 Ghent, Belgium. Electronic address: els.debonne@ugent.be.
² Research Unit Food Microbiology and Food Preservation, Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium.
³ Research Unit of Cereal and Feed Technology, Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Valentin Vaerwyckweg 1, 9000 Ghent, Belgium; Laboratory of Food Technology and Engineering, Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium.
⁴ Laboratory of Applied Mycology (MYCOLAB), Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Valentin Vaerwyckweg 1, 9000 Ghent, Belgium; Research Unit of Cereal and Feed Technology, Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Valentin Vaerwyckweg 1, 9000 Ghent, Belgium.
⁵ Laboratory of Applied Mycology (MYCOLAB), Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Valentin Vaerwyckweg 1, 9000 Ghent, Belgium; Research Unit Food Microbiology and Food Preservation, Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium.

PMID: 31202423
DOI: 10.1016/j.fm.2019.04.003

Abstract

The aims of this study were (i) screening of antifungal activity of thyme essential oil on Penicillium paneum; (ii) development of growth/no-growth models (G/NG); and (iii) validation of the G/NG models by performing bread baking trials. The screening method was based on the measurement of fungal growth in a semi-solid medium through optical density. The combined influence of a_w (0.88-0.97), pH (4.8-7.0), temperature (22 and 30 °C), time (0-144 h) and varying concentrations of thyme oil (0-2 μL/mL YES) were assessed. Growth of P. paneum at a_w 0.88 was significantly reduced compared to a_w 0.93-0.97. A slight pH effect was observed at a_w 0.93; growth was delayed at pH 6 compared to pH 4.8. The lowest concentration of thyme oil preventing growth during 144 h of incubation was 1 μL/mL medium. According to the results of the shelf-life test of par-baked bread, fungal growth was inhibited for more than 45 days using 0.3 mL thyme oil/100 g dough. To conclude, this study recognized the potential of using G/NG models to develop better product formulations and to facilitate product innovation.

Keywords: Growth/no-growth; MIC; Penicillium paneum; Predictive modelling; Thyme essential oil.

MeSH terms

Antifungal Agents / pharmacology*
Bread / microbiology
Food Microbiology
Food Preservation / methods
Hydrogen-Ion Concentration
Microbial Sensitivity Tests
Oils, Volatile / pharmacology*
Penicillium / drug effects*
Penicillium / growth & development*
Temperature*
Thymus Plant / chemistry*
Water

Substances

Antifungal Agents
Oils, Volatile
Water