Abstract:

The effects of food preservatives including nisin, sodium nitrite, sodium benzoate, potassium sorbate, sodium
pyrosulphate and calcium propionate on growth kinetic parameters of Staphylococcus aureus CMCC(B)26003 were
studied. The critical growth concentrations of six preservatives were determined and the growth of Staphylococcus aureus
CMCC(B)26003 treated with each of them was depicted. The growth difference in exponential phase and stationary phase
cells treated with some of these preservatives was clarified by maximum specific growth rate (μmax) or lag time (Lag).
The results showed that nisin had a potent bactericidal effect on Staphylococcus aureus. The cell density dropped from
6.09 lgCFU/mL to 3.68 (lgCFU/mL) during the first 6 h of treatment by nisin, and then recovered to the initial level after
treatment for 15 h. However, the other five preservatives had only an inhibitory effect on Staphylococcus aureus, and growth
parameters were obtained from the established Baranyi Model. The μmax of the cells in the treatment group was much lower
than that in the control group. The μmax of the cells treated with sodium pyrosulphate was the lowest, only 0.45 h-1. The
Lag value indicated irregular changes. Potassium sorbate revealed the longest Lag value up to 2.87 h. In addition, the μmax
during the exponential phase was lower than that during the stationary phase when the cells were treated with either sodium
pyrosulphate or potassium sorbate, especially upon treatment with sodium pyrosulphate, resulting in an almost two-fold
difference (statistically significant at P ＜ 0.001) in the μmax of the cells during the exponential phase and stationary phase,
which were 0.45 h-1 and 0.88 h-1, respectively. However, no obvious differences in the Lag value of the cells were found
during the exponential phase and stationary phase under the action of both preservatives.

Key words: food preservatives, Staphylococcus aureus, growth parameters