Use of exogenous volatile organic compounds to detect Salmonella in milk

Rapid, sensitive, and selective detection and identification of pathogenic bacteria is required in terms of food security. In this study, exogenous VOCs liberated by Salmonella strains have been identified and quantified via head space-solid phase microextraction gas chromatography mass spectrometry (HS-SPME-GC-MS) in milk samples. The specific enzymes targeted for detection and/or differentiation of Salmonella were C8 esterase, α-galactosidase and pyrrolidonyl peptidase using the following enzyme substrates: 2-chlorophenyl octanoate, phenyl α-d-galactopyranoside and L-pyrrollidonyl fluoroanilide, respectively. Detection of the exogenous VOCs, 2-chlorophenol, phenol and 3-fluoraniline was possible with typical limits of detection of 0.014, 0.045 and 0.005 μg/mL, respectively and correlation coefficients >0.99. The developed methodology was able to detect and identify Salmonella species within a 5 h incubation at 37 °C by the detection of the liberated VOCs. It was found that the milk samples tested were Salmonella free.