Organisms Associated with Acetic Acid Bacteria in Vinegar Production

Abstract

Vinegars are the product of scalar fermentations carried out by several groups of microorganisms acting at different moments in time. The initial phase is generally represented by an alcoholic fermentation commonly carried out by yeasts. Lactic acid bacteria (LAB) can also play a role in releasing ethanol and acetic acid from heterofermentative lactic acid fermentations. Depending on the nature of the substrate, the production of ethanol can be preceded by a transformation that induces the release of fermentable sugars from complex substrates. This is the case of rice vinegars, which require the action of some moulds of the genus Aspergillus to break the starch into fermentable sugars. The ethanol originating from the alcoholic fermentation is finally oxidized by acetic acid bacteria (AAB) and the alcoholic beverage is turned into vinegar (see Table 5.1). Even though acetic acid bacteria play the leading role in vinegar production, the metabolic activity of yeasts, moulds and lactic acid bacteria is also crucial for guaranteeing the manufacture of the product. These microorganisms, in fact, modify the fermentative substrates in order to allow the final stage of ethanol oxidation. This chapter provides an overview of their taxonomy, their nutritional requirements, their metabolic activity and their relevance in the vinegar manufacturing process (see Table 5.2). Brief descriptions of vinegar eels and Drosophila are also given to complete the variety of organisms that are involved in vinegar production.