Existence and Development of Natural Microbial Populations in Wooden Storage Vats Used for Alcoholic Cider Maturation

Abstract

Wooden maturation vats, traditionally used in the fruit-based alcoholic beverage industry, are gradually being superseded by vessels constructed from sterilizable materials, such as stainless steel. However, it is shown that the surfaces of existing vats, even after cleaning, possess a unique, individual microbial profile. One 10,000-gallon oak vat was studied over a nine-week maturation period, and the changing microbial profile within the fermented cider was recorded. Microbial colonization of wood was also examined by suspending cubes of unused oak in the cider vat and visualized using scanning electron microscopy. A variety of microorganisms progressively colonized the porous structure of wood, which once established, would appear to persist throughout emptying, cleaning, and refilling cycles.