Thermal inactivation of stationary-phase and acid-adapted Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes in fruit juices.
The heat resistance of stationary-phase and acid-adapted Escherichia coli O157:H7, Salmonella enterica (serotypes Typhimurium, Enteritidis, Gaminara, Rubislaw, and Hartford), and Listeria monocytogenes was evaluated in single-strength apple. orange, and white grape juices adjusted to pH 3.9. The heat resistance increased significantly (P < 0.05) after acid adaptation. Salmonella had an overall lower heat resistance than the other pathogens. Acid-adapted E. coli O157:H7 presented the highest heat resistance in all juices at the temperatures tested, with lower z-values than Salmonella and L. monocytogenes. The heat resistance (D(60 degrees C)-values) of all three pathogens, assessed in tryptic soy broth adjusted to different pH values, increased above pH 4.0. From the results obtained in this study, one example of a treatment that will inactivate 5 logs of vegetative pathogens was calculated as 3 s at 71.1 degrees C (z-value of 5.3 degrees C). Normal processing conditions calculated for hot-filled, shelf-stable juices achieve a lethality in excess of 50,000 D for all three pathogens.
Center for the Development of Research Policy & New Technologies, National Food Processors Association, Washington, DC 20005, USA. amazzotta@pillsbury.com
A S
AS
Mazzotta
D001628:Beverages / Q000382:microbiology*; D015169:Colony Count, Microbial; D019453:Escherichia coli O157 / Q000254:growth & development*; D005638:Fruit / Q000382:microbiology*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008089:Listeria monocytogenes / Q000254:growth & development*; D012475:Salmonella / Q000254:growth & development*; D013997:Time Factors