Survival of Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes in Cranberry Juice Concentrates at Different °Brix Levels

Abstract

Survival of Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes was evaluated in cranberry juice concentrates to determine if a 5-log reduction could be achieved without any other treatment. Inactivation at 0°C in concentrates with different °Brix levels was determined for a five-strain composite of the individual pathogens in two physiological states. In concentrates at 18 to 46 °Brix (pH 2.2 to 2.5), all three pathogens (stationary-phase or acid-adapted cells) showed at least a 5-log reduction after a 6- or 24-h incubation. At 14 °Brix (pH 2.5), a reduction greater than 5 log was obtained for L. monocytogenes and Salmonella after up to 24 h of incubation, but for E. coli O157:H7, 96 h of incubation was needed to consistently obtain a reduction greater than 5 log. All three pathogens in the stationary phase survived longer than in the acid-adapted phase under the same conditions. The most resistant was stationary-phase E. coli O157:H7, and the most sensitive was acid-adapted L. monocytogenes. The rate of pathogen destruction increased with increasing °Brix level of the juice concentrate, which suggests that concentrated acids and/or some intrinsic compounds may play an important role in the bactericidal effects of cranberry juice concentrates.