ORIGINAL ARTICLE Detection and differentiation of live and heat-treated Salmonella enterica serovars inoculated onto chicken breast using Fourier transform infrared (FT-IR) spectroscopy R. Davis 1 , Y. Burgula 1 , A. Deering 1 , J. Irudayaraj 2 , B.L. Reuhs 1 and L.J. Mauer 1 1 Department of Food Science, Purdue University, West Lafayette, IN, USA 2 Department of Agriculture and Biological Engineering, Purdue University, West Lafayette, IN, USA Introduction Salmonellosis caused by different serovars of Salmonella enterica is one of the most common intestinal infections that occurs worldwide. The incidence of Salmonellosis appears to be rising both in the United States and in other industrialized nations (FDA 2008), resulting in an estimate of 1Æ4 million infections and 400 deaths annually in the United States (Voetsch et al. 2004; CDC 2007). Approximately 36 000 laboratory confirmed cases of Salmonella infection are reported in the United States each year (CDC 2007). Recent outbreaks of Salmonellosis have been linked to raw produce items (MMWR 2008b), frozen pot pies (MMWR 2008a), and peanut butter (MMWR 2009). A considerable number of human Salmo- nellosis outbreaks have also been associated with meat consumption, in particular contaminated or undercooked meats, of which poultry has been implicated as a vehicle (MMWR 2008a). The Food Safety and Inspection Service (FSIS) announced a sustained increase in chicken-broiler carcasses testing positive for Salmonella during 2002–2005 (USDA 2006). Keywords chicken breast, filtration, FT-IR, live dead differentiation, pathogen detection, Salmonella enterica. Correspondence Lisa J. Mauer, Department of Food Science, Purdue University, 745 Agriculture Mall Drive, West Lafayette, IN 47907, USA. E-mail: mauer@purdue.edu 2009 ⁄ 2000: received 18 November 2009, revised and accepted 23 July 2010 doi:10.1111/j.1365-2672.2010.04832.x Abstract Aims: To evaluate Fourier transform infrared (FT-IR) techniques for detecting, quantifying, and differentiating viable and heat-treated cells of Salmonella enterica serovars from chicken breast. Methods and Results: Salmonella enterica serovars were captured from inocu- lated chicken breast by filtration and immunomagnetic separation (IMS) prior to spectral collection using an FT-IR spectrometer and IR microscopy. The detection limits, based on amide II peak area (1589 to 1493 cm )1 ), for the Filtration-FT-IR and IMS-FT-IR methods were 10 6 and 10 4 CFU g )1 , respectively. The bacteria were detectable after 6 h of culture enrichment during a sensitivity experiment with lower initial inoculum of 10 1 CFU g )1 . Canonical variate anal- ysis differentiated experimental from control spectra at a level of 10 3 CFU g )1 . Partial least squares models were established for the quantification of Salm. enterica from chicken breast using Filtration-FT-IR (R 2 ‡ 0Æ95, RMSEC £ 0Æ62) and IMS-FT-IR (R 2 ‡ 0Æ80, RMSEC £ 1Æ61) methods. Filtration-FT-IR was also used to detect and quantify live Salm. enterica in the presence of heat-treated cells with R 2 =0Æ996, and this approach was comparable to the results of a commercial stain (BacLightÔ; R 2 =0Æ998). Discriminant and canonical variate analyses of the spectra differentiated live and dead cells of different serovars of Salm. enterica. Conclusions: FT-IR analysis coupled with separation methods is useful for the rapid detection and differentiation of Salm. enterica separated from chicken. Significance and Impact of the Study: FT-IR-based methods are faster than tra- ditional microbiological methods and can be used for the detection of live and dead bacteria from complex foods. Journal of Applied Microbiology ISSN 1364-5072 ª 2010 The Authors Journal of Applied Microbiology 109, 2019–2031 ª 2010 The Society for Applied Microbiology 2019