Viability of Lactobacillus plantarum in Orange Juice under Low pH and Temperature Conditions

Abstract

ABSTRACTA strain of Lactobacillus plantarum, isolated from fermenting orange juice (OJ), was inoculated into unpasteurized or reconstituted OJ and held under low pH/low temperature conditions. Viability decreased more rapidly at subfreezing temperatures near – 5°C than at lower or higher temperatures. Viability decreased 0.37 log CFU/mL/hr at ‐ 6.6°C and 0.05 log CFU/mL/hr at ‐ 18°C. Rates of population decrease in frozen samples at ‐ 5°C were about three times greater than in unfrozen samples at the same temperature. An inverse linear relationship existed between rate of population decrease (log CFU/mL/day) at ‐ 7°C and OJ pH, with the rate of decrease at pH 4.1, about 1 log cycle lower than at pH 3.5 (0.024 and 0.60, respectively).