Isolation and quantification of highly acid resistant variants of Listeria monocytogenes

Moderate and high intensity pulsed electric fields : Effect on microbial inactivation, shelf life and quality of fruit juices

“…The models presented in this work were evaluated using published data. Inactivation data of proteinase was obtained by digitizing published graphs (Driessen, 1983;Schokker & Van Boekel, 1997) using GraphClick 3.0.3 (Arizona Software 2012), and for L. monocytogenes the original raw data was used (Metselaar et al, 2013 andMetselaar et al, 2016).…”

“…Highly accurate kinetic inactivation data for Listeria monocytogenes at different temperatures and pH, were provided by Metselaar et al (2013), Metselaar et al (2016). Metselaar et al (2013) have studied the inactivation of L. monocytogenes LO28 wild type (WT) and an acid resistant variant 14, at two different growth stages (late exponential and stationary phase) towards combinations of heat and acidification. They have modelled the observed (non-linear) inactivation kinetics piecewise using a biphasic model with a shoulder and a reduced model (Metselaar et al, 2016).…”

“…The Gauss-Eyring model was fitted as a global model to the inactivation data of Metselaar et al (2013), Metselaar et al (2016) using temperature, pH and time as the independent variables and assuming two Gaussian subpopulations (8 parameters) according to:…”

“…Typical line shapes that are used for kinetic modelling are Weibull (Van Boekel, 2002), log-logistic (Anderson et al, 1996) and modifications thereof (Bevilacqua et al, 2015;Metselaar et al, 2013). The choice of a suitable line shape depends on the actual shape of the observed inactivation.…”

“…In case of suspected heterogeneity , e.g., when biphasic inactivation curves are observed both for enzymes (e.g., Van Boekel, 2009c) and microbes (e.g. Metselaar et al, 2013), the choice of a specific line shape or the number of assumed sub-populations may differ for a particular subset of the experimental data series, even though the same initial sample was used that was subjected to similar environmental conditions . Nevertheless, parameter estimates in empirical models are extensively used for statistical analysis of the experimental data and to determine confidence levels for predictions (Bevilacqua et al, 2015).…”