Modelling the effects of lactic acid, sodium benzoate and temperature on the growth of Candida maltosa.

The growth of the oxidatively imperfect yeast Candida maltosa Komagata, Nakase et Katsuya was studied experimentally and modelled mathematically in relation to sodium benzoate and lactic acid concentrations at different temperatures. Application of gamma models for the growth rate resulted in determination of cardinal temperature parameters for the growth environment containing lactic acid or sodium benzoate (Tmin  = 0·7/1·3°C, Tmax  = 45·3/45·0°C, Topt  = 36·1/37·0°C, ?opt  = 0·88/0·96 h-1 ) as well as the maximal lactic acid concentration for growth (1·9%) or sodium benzoate (1397 mg kg-1 ). Based on the model, the times to reach the density of C. maltosa at the level of 105  CFU per ml can be determined at each combination of storage temperature and preservative concentration. The approach used in this study can broaden knowledge of the microbiological quality of fermented milk products during storage as well as the preservation efficacy of mayonnaise dressing for storage and consumption.

SIGNIFICANCE AND IMPACT OF THE STUDY: The strain of Candida maltosaYP1 was originally isolated from air filters that ensured clean air overpressure in yoghurt fermentation tanks. Its growth in contaminated yoghurts manifested outwardly through surface growth, assimilation lactic acid and slight production of carbon dioxide. This was the opportunity to model the effects of lactic acid and sodium benzoate on growth and predict its behaviour in foods. The approach used in this study provides knowledge about microbiological quality development during storage of the fermented milk products as well as some preserved foods for storage and consumption.