Modelling the combined effect of temperature, pH and aw on the growth rate of Monascus ruber, a heat-resistant fungus isolated from green table olives

Authors


P.N. Skandamis, Agricultural University of Athens, Department of Food Science and Technology, Laboratory of Microbiology and Biotechnology of Foods, Iera Odos 75, Athens, Greece, GR-11855 (e-mail: gjn@aua.gr).

Abstract

Aims: Growth modes predicting the effect of pH (3·5–5·0), NaCl (2–10%), i.e. aw (0·937–0·970) and temperature (20–40°C) on the colony growth rate of Monascus ruber, a fungus isolated from thermally-processed olives of the Conservolea variety, were developed on a solid culture medium.

Methods and Results: Fungal growth was measured as colony diameter on a daily basis. The primary predictive model of Baranyi was used to fit the growth data and estimate the maximum specific growth rates. Combined secondary predictive models were developed and comparatively evaluated based on polynomial, Davey, gamma concept and Rosso equations. The data-set was fitted successfully in all models. However, models with biological interpretable parameters (gamma concept and Rosso equation) were highly rated compared with the polynomial equation and Davey model and gave realistic cardinal pHs, temperatures and aw.

Conclusions: The combined effect of temperature, pH and aw on growth responses of M. ruber could be satisfactorily predicted under the current experimental conditions, and the models examined could serve as tools for this purpose.

Significance and Impact of the Study: The results can be successfully employed by the industry to predict the extent of fungal growth on table olives.

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