irrespective of NaCl. Further increase in pH to 6.8 and low concentration
of NaCl (0.4e0.8%), the growth rate of L. monocytogenes
in meat will increase to 0.30 Ln CFU/g/day (Fig. 3). Thus, the pH of
meat should be around 5.4 to 5.8 to ensure the maximum of food
safety during storage at 4 C.
Fig. 4 presents the interaction effects between NaCl and sodium
nitrite while fixing other factors such as pH (6.1), sodium acetate
(0.38%), potassium lactate syrup (1.5%), and calcium propionate
(0.1%) on the growth rate of L. monocytogenes in meat. We can see
that nitrite is the most important factor in this case since at highest
nitrite concentration of 200e220 ppm, even at low concentration
of NaCl of 0.4e0.6%, there is no growth (0.04 Ln CFU/g/day) of
L. monocytogenes in meat during 90 days of storage. Further, if NaCl
is at high concentration of 2.0e2.6% and even at low concentration
of nitrite (0e60 ppm), the growth rate of L. monocytogenes will be
approximately 0.01 Ln CFU/g/day which is also not very important.