Modeling Lactic Fermentation of Gowe Using Lactobacillus Starter Culture

A global model of the lactic fermentation step of gowe was developed by assembling blocks hosting models for bacterial growth, lactic acid production, and the drop of pH during fermentation. Commercial strains of Lactobacillus brevis and of Lactobacillus plantarum were used; their growth was modeled using Rosso's primary model and the gamma concept as a secondary model. The optimum values of pH and temperature were 8.3 +/- 0.3, 44.6 +/- 1.2 degrees C and 8.3 +/- 0.3, 3.2 +/- 37.1 degrees C with p. max values of 1.8 +/- 0.2 and 1.4 +/- 0.1 for L. brevis and L. plantarum respectively. The minimum inhibitory concentration of undissociated lactic acid was 23.7 mM and 35.6 mM for L. brevis and L. plantarum, respectively. The yield of lactic acid was five times higher for L. plantarum than for L. brevis, with a yield of glucose conversion to lactic acid close to 2.0 for the former and 0.8 for the latter. A model was developed to predict the pH drop during gowe fermentation. The global model was partially validated during manufacturing of gowe. The global model could be a tool to aid in the choice of suitable starters and to determine the conditions for the use of the starter.