Influence of temperature, water activity and pH on growth of some xerophilic fungi

The combined effects of water activity ( a w), pH and temperature on the germination and growth of seven xerophilic fungi important in the spoilage of baked goods and confectionery were examined. Eurotium rubrum, E. repens, Wallemia sebi, Aspergillus penicillioides, Penicillium roqueforti, Chrysospo...

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Bibliographic Details
Published in:International journal of food microbiology 2003-02, Vol.81 (1), p.11-19
Main Authors: Gock, Melissa A, Hocking, Ailsa D, Pitt, John I, Poulos, Peter G
Format: Article
Language:English
Subjects:
Biological and medical sciences
Culture Media
Food industries
Food Microbiology
Food Preservation
Fructose - metabolism
Fundamental and applied biological sciences. Psychology
Fungi - growth & development
Fungi - physiology
Germination
Glucose - metabolism
Growth
Hydrogen-Ion Concentration
Kinetics
Temperature
Water
Water activity
Water relations
Xerophilic fungi
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Summary:The combined effects of water activity ( a w), pH and temperature on the germination and growth of seven xerophilic fungi important in the spoilage of baked goods and confectionery were examined. Eurotium rubrum, E. repens, Wallemia sebi, Aspergillus penicillioides, Penicillium roqueforti, Chrysosporium xerophilum and Xeromyces bisporus were grown at 25, 30 and 37 °C on media with pH values of 4.5, 5.5, 6.5 and 7.5 and a range of water activities ( a w) from 0.92 to 0.70. The a w of the media was controlled with a mixture of equal parts of glucose and fructose. Temperature affected the minimum a w for germination for most species. For example, P. roqueforti germinated at 0.82 a w at 25 °C, 0.86 a w at 30 °C and was unable to germinate at 37 °C. E. repens germinated at 0.70 a w at 30 °C, but at 25 and 37 °C, its minimum a w for germination was 0.74. C. xerophilum and X. bisporus germinated at 0.70 a w at all three temperatures. The optimum growth occurred at 25 °C for P. roqueforti and W. sebi, at 30 °C for Eurotium species, A. penicillioides and X. bisporus and at 37 °C for C. xerophilum. These fungi all grew faster under acidic than neutral pH conditions. The data presented here provide a matrix that will be used in the development of a mathematical model for the prediction of the shelf life of baked goods and confectionery.
ISSN:0168-1605
1879-3460
DOI:10.1016/S0168-1605(02)00166-6