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 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 microg 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 < or = 0.05) decreased D-values at lower (< 58 degrees 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 degrees C without NaCl; 63 degrees C with NaCl). However, when nisin was added 2 h prior to heat treatment, D-values were significantly (P < or = 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.
Knight
K P
KP
Department of Food Science, University of Guelph, Ontario, Canada.
Bartlett
F M
FM
McKellar
R C
RC
Harris
L J
LJ
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002645:Chickens; D003470:Culture Media; D004531:Eggs / Q000382:microbiology*; D005516:Food Microbiology; D005520:Food Preservatives / Q000494:pharmacology; D006358:Hot Temperature; D008089:Listeria monocytogenes / Q000187:drug effects* / Q000254:growth & development; D009561:Nisin / Q000494:pharmacology*; D012965:Sodium Chloride / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D003470:Culture Media; D005520:Food Preservatives; D009561:Nisin; D012965:Sodium Chloride