Rapid diagnosis of Enterobacteriaceae in vegetable soups by a metal oxide sensor based electronic nose

• Vegetable soups contaminated by Enterobacter hormaechei and Escherichia coli were screened by electronic nose.
• We report excellent classification performance of contaminated samples.
• Diagnosis was demonstrated in less than 24 h of growth time.
• Sensor responses are significantly correlated with inocula concentrations.
• Results were replicated and confirmed over two different experimental campaigns.

A rapid protocol for the early diagnosis of microbial contamination of commercial food products by Electronic Nose is presented. Mixed vegetable soup samples are artificially contaminated by Enterobacter hormaechei and Escherichia coli and a large dataset of 584 samples, over two experimental campaigns, was analyzed by the electronic nose EOS507C based on a four metal oxide sensors array. Diagnosis of the contamination is obtained after 21 h and 18 h from the inoculation of E. hormaechei and E. coli respectively. EOS detection thresholds at 24 h were as little as 8 cells/100 ml for E. hormaechei and 3 cells/100 ml for E. coli. The achieved LDA classification performance of contaminated samples was 98%. Also a significant correlation between the sensors responses and the inocula concentrations was obtained. Good long-term repeatability and reliability was demonstrated by comparing the results of the two experimental campaigns spanning for 14 months. The EOS resulted to fulfill all the main requirements of an ideal industrial screening system: specificity, sensitivity, early diagnosis, operational simplicity, reproducibility and cost effectiveness.