Inactivation of Salmonella Typhimurium in Orange Juice Containing Antimicrobial Agents by Pulsed Electric Field
Combinations of different hurdles, including moderately high temperatures (<60°C), antimicrobial compounds, and pulsed electric field (PEF) treatment, to reduce Salmonella in pasteurized and
freshly squeezed orange juices (with and without pulp) were explored. Populations of Salmonella Typhimurium were found to decrease with an increase in pulse number and treatment temperature. At a
field strength of 90 kV/cm, a pulse number of 20, and a temperature of 45°C, PEF treatment did not have a notable effect on cell viability or injury. At and above 46°C, however, cell death and injury
were greatly increased. Salmonella numbers were reduced by 5.9 log cycles in freshly squeezed orange juice (without pulp) treated at 90 kV/cm, 50 pulses, and 55°C. When PEF treatment was carried
out in the presence of nisin (100 U/ml of orange juice), lysozyme (2,400 U/ml), or a mixture of nisin (27.5 U/ml) and lysozyme (690 U/ml), cell viability loss was increased by an additional 0.04 to 2.75
log cycles. The combination of nisin and lysozyme had a more pronounced bactericidal effect than did either nisin or lysozyme alone. An additional Salmonella count reduction of at least 1.37 log
cycles was achieved when the two antimicrobial agents were used in combination. No significant difference (P > 0.05) in cell death was attained by lowering the pH value; only cell injury increased.
Inactivation by PEF was significantly more extensive (P < 0.05) in pasteurized orange juice than in freshly squeezed orange juice under the same treatment conditions. This increase might be due
to the effect of the chemical composition of the juices.
Document Type: Research Article
School of Engineering, University of Guelph, Ontario, Canada N1G 2W1
School of Engineering and Canadian Research Institute for Food Safety, University of Guelph, Ontario, Canada N1G 2W1
Canadian Research Institute for Food Safety and Department of Food Science, University of Guelph, Ontario, Canada N1G 2W1
Publication date: July 1, 2002
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