Spatial pH distribution during ripening of camembert cheese

During the ripening phase, the pH values continually change, which impacts the survival and growth of all microorganisms including Listeria monocytogenes (a foodborne pathogen). Toward this end, distribution and change of pH during ripening of cylindrical (108 mm diameter; 32 mm height) Camembert cheese were measured at 16 locations and three vertical cross-sections 120° apart. The pH at different locations had significant differences (P < 0.05) for each day of ripening. The pH values in the top and bottom regions had higher values than in the top middle and bottom middle regions. In addition, the pH in the surface region was higher than in the center region. The day had a significant effect (P < 0.05) on the pH values during ripening. Overall, the pH values increased gradually and throughout the ripening of Camembert cheese. The pH value was around 4.5 on day 1 and approximately 7.5 on day 35 of ripening. Within a set, the pH values had no significant difference (P > 0.05) for each batch and each section. For across-set comparisons, the set had no significant effect (P > 0.05) on the pH values during ripening. There were similar values for each batch and section on each ripening day. The pH values measured in this research can be the basis for developing a mathematical model to predict the distribution of pH, which when coupled with a dynamic predictive growth model, will enable the prediction of survival and growth of L. monocytogenes during ripening of Camembert cheese.