The influence of pH and sodium chloride (NaCl) on survival and growth of Listeria monocytogenes in carrot juice was determined. Lethal and inhibitory effect over a 48-h period were greatest in a pH range of 5.0 to 6.4. The order of lethality and inhibition was 10% > 1% > 100% > 0.1% juice concentrations and increased as the incubation temperature was reduced from 20 to l2°C, and again from 12 to 5°C. At concentrations up to 5%, NaCl protected against inactivation of L. monocytogenes in carrot juice. This effect was most pronounced in 10% juice incubated at 5 or l2°C. Populations of naturally occurring aerobic mesophiles in carrot juice were generally unaffected by pH or NaCl content. The effectiveness of carrot juice as an antilisterial ingredient in food has yet to be determined.
Keywords: pH; sodium chloride; temperature.