Differentiation and detection of microorganisms using Fourier transform infrared photoacoustic spectroscopy

Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) was used to differentiate and identify microorganisms on a food (apple) surface. Microorganisms considered include bacteria (Lactobacillus casei, Bacillus cereus, and Escherichia coli), yeast (Saccharomyces cerevisiae), and fungi (Aspergillus niger and Fusarium verticilliodes). Discriminant analysis was used to differentiate apples contaminated with the different microorganisms from uncontaminated apple. Mahalanobis distances were calculated to quantify the differences. The higher the value of the Mahalanobis distance metric between different microorganisms, the greater is their difference. Additionally, pathogenic (O157:H7) E. coli was successfully differentiated from non-pathogenic strains. Results demonstrate that FTIR-PAS spectroscopy has the potential to become a non-destructive analysis tool in food safety related research. (C) 2002 Elsevier Science B.V. All rights reserved.