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Detection of Sublethal Thermal Injury in Salmonella enterica Serotype Typhimurium and Listeria monocytogenes Using Fourier Transform Infrared (FT‐IR) Spectroscopy (4000 to 600 cm −1 )
Author(s) -
AlQadiri H.M.,
Lin M.,
AlHoly M.A.,
Cavinato A.G.,
Rasco B.A.
Publication year - 2008
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1750-3841.2007.00640.x
Subject(s) - salmonella enterica , listeria monocytogenes , serotype , salmonella , chemistry , microbiology and biotechnology , fourier transform infrared spectroscopy , bacteria , food science , biology , physics , genetics , quantum mechanics
Fourier transform infrared (FT‐IR) spectroscopy (4000 to 600 cm −1 ) was utilized to detect sublethally heat‐injured microorganisms: Salmonella enterica serotype Typhimurium ATCC 14028, a Gram‐negative bacterium, and Listeria monocytogenes ATCC 19113, a Gram‐positive bacterium. A range of heat treatments ( N = 2) at 60 °C were evaluated: 0 D (control), 2 D , 4 D , 6 D , and 8 D using a D 60 °C ( S . enterica serotype Typhimurium ATCC 14028 = 0.30 min, L . monocytogenes ATCC 19113 = 0.43 min). The mechanism of cell injury appeared to be different for Gram‐negative and Gram‐positive microbes as observed from differences in the 2nd derivative transformations and loadings plot of bacterial spectra following heat treatment. The loadings for PC1 and PC2 confirmed that the amide I and amide II bands were the major contribution to spectral variation, with relatively small contributions from C‐H deformations, the antisymmetric P==O stretching modes of the phosphodiester nucleic acid backbone, and the C‐O‐C stretching modes of polysaccharides. Using soft independent modeling of class analogy (SIMCA), the extent of injury could be predicted correctly at least 83% of the time. Partial least squares (PLS) calibration analysis was constructed using 5 latent variables for predicting the bacterial counts for survivors of the different heat treatments and yielded a high correlation coefficient ( R = 0.97 [ S . enterica serotype Typhimurium] and 0.98 [ L. monocytogenes ]) and a standard error of prediction ( SEP = 0.51 [ S . enterica serotype Typhimurium] and 0.39 log 10 CFU/mL [ L. monocytogenes ]), indicating that the degree of heat injury could be predicted.