Effect of water activity and temperature on growth of Alternaria alternata on a synthetic tomato medium

• Published in: International journal of food microbiology 2009-09, Vol.135 (1), p.60-63
• Main Authors: Pose, G., Patriarca, A., Kyanko, V., Pardo, A., Fernández Pinto, V.
• Format: Article
• Language: English
• Subjects: Alternaria - growth & development; Alternaria - metabolism; Alternaria alternata; ambient temperature; Argentina; Biological and medical sciences; Colony Count, Microbial; Consumer Product Safety; culture media; Food Contamination - analysis; Food Contamination - prevention & control; Food industries; Food Microbiology; Food Preservation - methods; Fruit and vegetable industries; Fundamental and applied biological sciences. Psychology; fungus physiology; Growth; Kinetics; Lycopersicon esculentum; Lycopersicon esculentum - microbiology; microbial growth; Mycotoxins - biosynthesis; postharvest diseases; spore germination; strain differences; Temperature; Time Factors; Tomato; tomatoes; toxigenic strains; Water - metabolism; Water activity
• ISSN: 0168-1605; 1879-3460
• DOI: 10.1016/j.ijfoodmicro.2009.07.018

Alternaria alternata is a toxigenic fungus, predominantly responsible for Blackmould of ripe tomato fruits, a disease frequently causing substantial losses of tomatoes, especially those used for canning. The objective of this study was to determine the effect of water activity ( a w, 0.904, 0.922, 0.954, 0.982) and temperature (6, 15, 21 and 35 °C) on germination and radial growth rate on a synthetic tomato medium of a cocktail inoculum of five strains of A. alternata isolated from tomato fruits affected by Blackmould. The shortest germination time (1.5 days) was observed at 0.982 a w, both at 21 °C and 35 °C. The germination time increased with a reduction on a w. The fastest growth rate was registered at 0.982 a w and 21 °C (8.31 mm/day). Growth rates were higher when a w increased. No growth or germination was observed at the lowest a w level evaluated (0.904) after 100 days of incubation at 6 °C and 15 °C. A temperature of 6 °C caused a significant reduction in growth rates, even at the optimum a w level. The knowledge on the ecophysiology of the fungus in this substrate is necessary to elaborate future strategies to prevent its development and evaluate the consumer health risk.