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Evaluation of indirect impedance for measuring microbial growth in complex food matrices

Johnson, N., Chang, Z., Bravo Almeida, C., Michel, M., Iversen, C., Callanan, M.
Food microbiology 2014 v.42 pp. 8-13
Bacillus cereus, Candida tropicalis, Escherichia coli, Lactobacillus plantarum, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella, Staphylococcus aureus, Zygosaccharomyces rouxii, carbon dioxide production, food matrix, foods, impedance, inoculum, microbial growth, models, specific growth rate
The suitability of indirect impedance to accurately measure microbial growth in real food matrices was investigated. A variety of semi-solid and liquid food products were inoculated with Bacillus cereus, Listeria monocytogenes, Staphylococcus aureus, Lactobacillus plantarum, Pseudomonas aeruginosa, Escherichia coli, Salmonella enteriditis, Candida tropicalis or Zygosaccharomyces rouxii and CO2 production was monitored using a conductimetric (Don Whitely R.A.B.I.T.) system. The majority (80%) of food and microbe combinations produced a detectable growth signal. The linearity of conductance responses in selected food products was investigated and a good correlation (R2 ≥ 0.84) was observed between inoculum levels and times to detection. Specific growth rate estimations from the data were sufficiently accurate for predictive modeling in some cases. This initial evaluation of the suitability of indirect impedance to generate microbial growth data in complex food matrices indicates significant potential for the technology as an alternative to plating methods.