Microbial fermentation is used to process the seeds of Coffea.
The skin (exocarp) and pulp (outer mesocarp) are removed from the
coffee cherry mechanically. The two beans are then put in a fermentation
tank to degrade the hygroscopic inner mesocarp. Lactic acid bacteria
initiate acidification of the coffee mass and solubilization of
pectin. The highly methylated pectin is degraded by endogenous coffee
Look at the graph below. What causes the pH to decrease?