Sanitation of wooden barrels for ageing beer – a review

Abstract

YEAST SPECIAL

The use of wooden barrels is a traditional technique for fermentation and maturation of beer, most prominently present in the production of traditional sour beers like Belgian lambic beer and red-brown acidic ales. In recent years, barrel ageing of beer is also gaining an increased interest to add notes of wood or aromas from the previously matured beverage to the beer. However, insufficient cleaning and sanitation of barrels can result in microbial spoilage which may have a detrimental impact on beer quality, e.g. caused by wild yeasts like Brettanomyces, acetic acid bacteria and lactic acid bacteria. Therefore, in order to control the microbial load of the barrel, it is important to properly clean and sanitise the barrels. To date, to our knowledge no systematic review has been published on the available sanitation techniques for wooden beer barrels. Here, we provide a comprehensive overview of various chemical and physical cleaning and sanitation methods that are commonly applied in breweries like sulphur dioxide, steam and hot water. In addition, we discuss a number of alternative methods that are gaining interest and popularity such as ozone and high-power ultrasound. We address their advantages and drawbacks, emphasising their ability to eradicate spoilage microorganisms and influences on the extraction of typical wood associated flavours from the barrels. Finally, limitations in existing knowledge are discussed and areas that merit further study are identified, including combinations of different treatments.