Kinetic study of the thermal inactivation of <i>Lactobacillus plantarum</i> during bread baking

Live probiotics can be supplemented to bread as functional ingredients. The viability of probiotics in bread needs to be sufficient to exert a beneficial effect on human health. To maximize the viability, a kinetic study on the inactivation of probiotics during baking was carried out. The thermal inactivation of Lactobacillus plantarum P8 during bread baking was evaluated with rate-dependent kinetic models. The influences of temperature, moisture content, drying rate, and temperature variation rate on the inactivation kinetics were studied explicitly. A kinetic model kd=ko1+adTdtexp⁡bX−EdRT, which included temperature (T), moisture content (X), and temperature variation rate (dT/dt) as variables, was found to best describe the concave and sigmoidal survival curves of probiotics in bread crust and in crumb during baking, respectively. The drying rate (dX/dt) was of little influence on the kinetics. The application of the proposed model is limited to baking processes, but could be used to maximize the survival of probiotics in bread products.