Lactic acid, in addition to increasing the acidity of fermented foods and beverages and prolonging their shelf life, is responsible for a substantial improvement in the flavor, aroma and texture of the food or drink it ferments.
During lactic acid fermentation, LAB bacteria not only produce lactic acid, but also produce enzymes that break down complex proteins into free amino acids.
This contributes to the development of the some attributes that make up the coffee’s sensory profile such as the “umami” flavor. Although “umami” is not included in the coffee flavor wheel, it is the fifth flavor attribute present. It refers to the sensation of a prolonged and delicious taste.
Lactic acid bacteria also produce some secondary metabolites such as esters, ketones, alcohols and aldehydes. These metabolites have been related to the development of some of coffee’s attributes such as floral, fruity and buttery tastes and textures.
Lactic acid bacteria are not the only ones present in coffee fermentation.
Lactic acid bacteria such as Lactobacillus acidophilus, L. fermentum and L. plantarum participate in the lactic acid fermentation of coffee, but are not the only bacteria present in coffee fermentation.
There are other indigenous bacteria specific to each coffee crop, and there are other fungi, bacteria and yeasts that are responsible for alcoholic and acetic fermentations.
If all the factors that influence the cup quality of coffee are not controlled, undesired microorganisms can also appear. These undesirable organisms will promote fermentations such as formic, propionic, butyric and methanic fermentations that result in very unpleasant coffee flavors.