Nisin reduces the thermal resistance of Listeria monocytogenes Scott A in liquid whole egg

D-values (decimal reduction times) and z-values (increase in temperature re quired for a 1-log change in D-value) for Listeria monocytogenes Scott A we re determined in liquid whole egg with nisin (0 or 10 mu g ml(-1)) and NaCl (0 or 10%) by a submerged glass ampoule procedure. Samples were plated ont o nonselective agar at appropriate intervals, and D-values were determined using a modified biphasic logistic equation. Addition of NaCl increased D-v alues at all temperatures tested. The addition of nisin to unsalted liquid whole egg resulted in a rapid 4-log reduction in viable counts within the f irst hour. Nisin significantly (P less than or equal to 0.05) decreased D-v alues at lower (<58 degrees C) temperatures in both unsalted and salted liq uid whole egg but had little effect on the D-values at current minimum U.S, and Canadian pasteurization temperatures (60 degrees C without NaCl; 63 de grees C with NaCl). However, when nisin was added 2 h prior to heat treatme nt, D-values were significantly (P less than or equal to 0.05) reduced at t hese temperatures. Inhibitory levels of nisin were detected in the liquid w hole egg postpasteurization. Nisin could have a favorable impact on the con trol of L. monocytogenes in pasteurized liquid egg products.