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This study determined the effect of acid, alkaline, chlorine, and ethanol stresses on the thermal inactivation of Enterobacter sakazakii in infant milk formula. Unstressed or stressed cells were mixed with reconstituted powdered infant milk formula (PIMF) at temperatures between 52 and 58 °C for various time periods or mixed with PIMF prior to reconstitution with hot water between 50 and 100 °C. D- and z-values were determined using liner regression analysis. In general, detergent and sanitizer stresses decreased the thermal resistance of E. sakazakii in infant milk formula. The results of this study may be of use to regulatory agencies, manufacturers, and infant caregivers to design heating processes to eliminate E. sakazakii. [ABSTRACT FROM AUTHOR]

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 D60 °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 log10 CFU/mL [ L. monocytogenes]), indicating that the degree of heat injury could be predicted. [ABSTRACT FROM AUTHOR]

The article presents a study which determined the thermal resistance of Clostridium sporogenes using aluminum thermal-death-time (TDT) tubes at 115 degree Celsius, 118.3 degree Celsius, and 121.1 degree Celsius. Results of the tests revealed that the aluminum TDT tubes are useful in the determination of thermal resistance at high temperatures, and that safe and shelf-stable packaged foods can be produced using thermal processes based on radio frequency (RF) energy.

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 D60 °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 log10 CFU/mL [ L. monocytogenes]), indicating that the degree of heat injury could be predicted. [ABSTRACT FROM AUTHOR]