Spectroscopic Analysis of Chicken Meat Contaminated with E. coli, Salmonella, and Campylobacter.

The microbiological contamination of food causes concern for public health due to the pathogenic action of microorganisms and the increasing of antimicrobial resistance observed in bacterial strains. This work considers the use of fluorescence spectroscopy to study the effects of the presence of microorganisms in the chicken's meat and therefore, how the detection of this presence can help on food safety. The fluorescence of organic boneless and skinless chicken breast pieces contaminated with variable concentrations of E. coli cells inoculated in meat (10⁴, 10⁵, 10⁶, and 10⁷ cells/mL) was measured with excitations at 340 and 410 nm. Raman spectra were obtained to investigate into conformational changes in the collagen structures, from samples kept for 48 h at 25 °C (non-contaminated and contaminated with E. coli, 10⁵ and 10⁷ cells/mL). Protoporphyrin IX fluorescence lifetime was measured in the function of an increased number of E. coli cells. The obtained results of E. coli were compared to the ones of Salmonella and Campylobacter contaminations (10⁶ cells/mL). Some uncommon aspects were found in the spectra of the contaminated meat: enlargement of the collagen band at 400 nm; increase in free reduced nicotinamide adenine dinucleotide fluorescence intensity around 505 nm; and decrease of flavin emission band. A shortening in the porphyrin emission lifetime (from ~ 10 ns for uncontaminated meat to ~ 5 ns) was observed, showing a quenching process for the meat contaminated with E. coli. The presence of coproporphyrin emission band was observed in the samples contaminated with Salmonella. The singularities observed in PpIX fluorescence spectroscopy for E. coli and Salmonella can be used to obtain a quick detection method of pathogenic bacteria. [ABSTRACT FROM AUTHOR]