Quantifying variability in growth and thermal inactivation kinetics of Lactobacillus plantarum

<p>The presence and growth of spoilage organisms in food might affect the shelf life. In this study, the effects of experimental, reproduction, and strain variabilities were quantified with respect to growth and thermal inactivation using 20 Lactobacillus plantarum strains. Also, the effect of growth history on thermal resistance was quantified. The strain variability in μ_max was similar (P&gt;0.05) to reproduction variability as a function of pH, a_w, and temperature, while being around half of the reproduction variability (P &lt;0.05) as a function of undissociated lactic acid concentration [HLa]. The cardinal growth parameters were estimated for the L. plantarum strains, and the pH_min was between 3.2 and 3.5, the a_w,min was between 0.936 and 0.953, the [HLa_max], at pH 4.5, was between 29 and 38 mM, and the T_min was between 3.4 and 8.3°C. The average D values ranged from 0.80 min to 19 min at 55°C, 0.22 to 3.9 min at 58°C, 3.1 to 45 s at 60°C, and 1.8 to 19 s at 63°C. In contrast to growth, the strain variability in thermal resistance was on average six times higher than the reproduction variability and more than ten times higher than the experimental variability. The strain variability was also 1.8 times higher (P10 differences in growth between the most and least robust strains and &gt; 10-log₁₀ differences after thermal treatment.