Abstract
A global model of the lactic fermentation step of gowé 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 °C and 8.3 ± 0.3, 3.2 ± 37.1 °C with μmax 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 gowé fermentation. The global model was partially validated during manufacturing of gowé. 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.
Highlights
Fermentation is one of the oldest methods of preserving food and involves microorganisms whose metabolic activity and growth determine both organoleptic properties and shelf-life [1]
This paper reports on the first studies in a global project that aims to provide a global but simple model for optimizing batch fermentations such as the fermentation of gowé, a traditional fermented Beninese beverage made from malted and non-malted sorghum flour that is produced by spontaneous fermentation involving mixed cultures of lactic acid bacteria (LAB) and yeasts [21,22,23]
We focused on the first three blocks linked to LAB growth; starch amylolysis
Summary
Fermentation is one of the oldest methods of preserving food and involves microorganisms whose metabolic activity and growth determine both organoleptic properties and shelf-life [1]. Secondary models predict changes in the bacterial growth rate as a function of environmental factors such as temperature, pH, water activity (aw) oxygen tension, etc. This paper reports on the first studies in a global project that aims to provide a global but simple model for optimizing batch fermentations such as the fermentation of gowé, a traditional fermented Beninese beverage made from malted and non-malted sorghum flour that is produced by spontaneous fermentation involving mixed cultures of lactic acid bacteria (LAB) and yeasts [21,22,23]. During the process of preparing gowé, amylolysis of starch, which gives the product its lightly sugary taste and its light texture, occurs during the fermentation step, but is rapidly inhibited by acidification caused by the growth of the lactic acid bacteria [27,28]. The final pH was measured, and ranged between 4.7 and 4.8
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