Comparison of the effects of temperature and water activity on growth rate of food spoilage moulds
2002
Sautour, M | Soares Mansur, C | Divies, C | Bensoussan, M | Dantigny, P
: The influence of temperature (T) and water activity (a w) on the growth rate (μ) of seven moulds (Alternaria alternata, Aspergillus flavus, Cladosporium cladosporioides, Mucor racemosus, Penicillium chrysogenum, Rhizopus oryzae and Trichoderma harzianum) was assessed in suboptimal conditions. Firstly, the dependence of fungal growth on temperature, at a w 0.99, was modelled through an approach described previously for bacteria. A dimensionless growth rate variable: μ dᵢₘα=μ/μ ₒₚₜα depended on the following normalised temperature: T dᵢₘ=(T−T ₘᵢₙ)/(T ₒₚₜ− T ₘᵢₙ) according to a power function: μ dᵢₘα=[T dᵢₘ] ᵅ , where α was an exponent to be estimated. Secondly, the same approach was used to describe the influence of a w on fungal growth, at the respective optimum temperatures for each mould. Similarly, μ dᵢₘᵦ=μ/μ ₒₚₜᵦ depended on the following normalised water activity: a wdᵢₘ=(a w−a wₘᵢₙ)/(a wₒₚₜ−a wₘᵢₙ) according to a power function: μ dᵢₘᵦ=[a wdᵢₘ]ᵝ. Results show: (i) for each mould, the α-value is significantly less than the β-value, confirming that water activity has a greater influence than temperature on fungal development; (ii) the α-values and the β-values depend on the mould; (iii) the α-value is less than 1 for the mesophilic mould A. flavus, whereas the other moulds are characterised by higher α-values ranging from 1.10 to 1.54; (iv) the mesophilic A. flavus exhibits a low β-value, 1.50, compared to the hydrophilic T. harzianum, β=2.44, while β-values are within the range (1.71–2.37) for the other moulds. Journal of Industrial Microbiology & Biotechnology (2002) 28, 311–315 DOI: 10.1038/sj/jim/7000248
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