THE EFFECT OF PH, ACIDULANT AND TEMPERATURE ON THE SURVIVAL OF YERSINIA-ENTEROCOLITICA

The survival of Yersinia enterocolitica at sub-optimal temperatures (0-23-degrees-C) and growth inhibitory pH values, achieved using a range of acidulants, was investigated. At a given pH, survival was greater the lower the temperature. Sulphuric and citric acids had lower bactericidal activity than acetic and lactic acids and in nearly all cases where the four acids could be compared at the same pH the order of bactericidal activity was acetic > lactic > citric > sulphuric. Attempts to model this behaviour by a negative square root relationship gave good correlation coefficients for plots of the square root of death rate against temperature at different combinations of pH and acidulant but so too did several other functions of death rate. The high coefficient of variation for T0 determined from square root plots prevented construction of a combined temperature/pH model similar to that already described for growth.