Growth/no growth models were developed based on optical density data gathered in Sabouraud broth during 90 days. The medium was modified mimicking intermediate moisture food by adding high amounts of sugar (50% (w/w), glucose and fructose in a 1:1 ratio). The media were varying in: (i) aw (0.76 – 0.88, by adding glycerol); (ii) pH (5.0 – 6.2, by adding HCl); (iii) ethanol (0 - 4.5 % [w/w] on total medium basis); and (iv)temperature (8 - 25°C)
For osmophilic yeast, three different models were included: (i) without organic acids, (ii) with acetic acid (1% on product basis), or (iii) with sorbic acid (1500 ppm on product basis) added as potassium sorbate. The model predicted the growth probability for yeast and molds at discrete time points: 30, 60, and 90 days of incubation.
References
Deschuyffeleer, N., et. al. 2015. Modelling of the growth/no growth interface of mimicking Wallemia sebi and Eurotium herbariorumas a function of pH, a(W) and ethanol concentration. International Journal of Food Microbiology. 192:77-85.
Vermeulen, A., et. al. 2012. Screening of different stress factors and development of growth/no growth models for Zygosaccharomyces rouxii in modified Sabouraud medium, mimicking intermediate moisture foods (IMF). Food Microbiology. 32:389-396.
Vermeulen, A., et. al. 2015. Strategies to increase the stability of intermediate moisture foods towards Zygosaccharomyces rouxii: The effect of temperature, ethanol, pH and water activity, with or without the influence of organic acids. Food Microbiology. 45:119-125.