EFFECTS OF TEMPERATURE, PH, GLUCOSE, AND CITRIC-ACID ON THE INACTIVATION OF SALMONELLA-TYPHIMURIUM IN REDUCED CALORIE MAYONNAISE

A Salmonella typhimurium strain was inoculated in reduced calorie mayo nnaise. A central composite design was implemented to assess the effec ts of temperature (15 to 35 degrees C), pH (4.5 to 6.5), glucose (1 to 4% [wt/vol]), and citric acid (0.05 to 0.1% [wt/vol]) on the inactiva tion of Salmonella. Whatever the conditions, an inhibition of the stra in was obtained, but only after a long period of time, from 11 to 85 d ays. In this study, as the survival curves obtained did not follow typ ical first-order destruction kinetics, the primary model chosen was ex ponential. A second-order polynomial linear regression was then used t o study the effects of the various factors on the inhibition of S. typ himurium. Estimated values of the k parameter, which represented the s hape of the destruction curves, were well correlated with the predicte d ones (R-2 = 0.94). Generally, the higher the temperature with a low pH, the greater the inactivation. With a citric acid concentration of 0.09% (wt/vol), no glucose effect could be seen. In contrast, a lower acid concentration, 0.06% (wt/vol), enabled the higher level of destru ction to be reached with a 3.5% (wt/vol) glucose concentration. This s tudy documented that reduced calorie mayonnaise containing citric acid can represent a nonnegligible consumer safety risk and indicated that a well-fitted model is of interest to correctly predict this risk.