D-values (decimal reduction times) and z-values (increase in temperature required for a 1-log change in D-value) for Listeria monocytogenes Scott A were determined in liquid whole egg with nisin (0 or 10 μg ml−1) and NaCl (0 or 10%) by a submerged glass ampoule procedure. Samples were plated onto nonselective agar at appropriate intervals, and D-values were determined using a modified biphasic logistic equation. Addition of NaCl increased D-values 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 first hour. Nisin significantly (P ≤ 0.05) decreased D-values at lower (<58°C) temperatures in both unsalted and salted liquid whole egg but had little effect on the D-values at current minimum U.S. and Canadian pasteurization temperatures (60°C without NaCl; 63°C with NaCl). However, when nisin was added 2 h prior to heat treatment, D-values were significantly (P ≤ 0.05) reduced at these temperatures. Inhibitory levels of nisin were detected in the liquid whole egg postpasteurization. Nisin could have a favorable impact on the control of L. monocytogenes in pasteurized liquid egg products.
Nisin Reduces the Thermal Resistance of Listeria monocytogenes Scott A in Liquid Whole Egg
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KELLEY P. KNIGHT, FRANCIS M. BARTLETT, ROBIN C. McKELLAR, LINDA J. HARRIS; Nisin Reduces the Thermal Resistance of Listeria monocytogenes Scott A in Liquid Whole Egg. J Food Prot 1 September 1999; 62 (9): 999–1003. doi: https://doi.org/10.4315/0362-028X-62.9.999
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