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58 P R A C T I C A L W I N E R Y & V I N E YA R D April 2015 R E S E A R C H F O C U S Sanitation of wine cooperage with five different treatment methods O ak barrels are a particularly challenging part of winery sanitation. While there are many sanitizing options avail- able, rigorous, side-by-side comparisons are required to know which treatments are more or less effective. In a recent study, we compared five sanitizers: sulfur dioxide, peroxyacetic acid (PAA), steam, chlorine dioxide and ozone at varying times or concentrations. The sulfur dioxide, steam, ozone and PAA at higher concentrations were all found to be effective sanitizers, but the lower concentration of PAA and chlorine dioxide did not significantly reduce the number of spoilage organisms. As with any sanitizing treatment, it is important first to have an effective cleaning step to remove dirt and debris. Introduction Oak barrels are a source of significant cost and effort in wineries where they are employed. Expensive to procure and challenging to maintain, barrels have some significant disadvantages when it comes to sanitation. First, it is impos- sible to "sanitize" a barrel the way one sanitizes a stainless steel tank. It harbors large amounts of microorganisms the day it arrives at the winery, and it will continue to do so when it is turned into a planter. Oak is a living organism, and the wood is naturally porous and layered. There are nooks and crannies that can- not be penetrated without destroying the wood and/or trapping residues of the cleaning agent. The implications of such limits are fairly serious, because barrels that get beyond management will most likely have to be discarded, and the only thing more costly than buying a new bar- rel is tossing one. Cleaning versus sanitizing When thinking about barrels and sanita- tion programs, it is important to remem- ber the difference between cleaning and sanitizing. Cleaning is the removal of dirt and debris, while sanitizing is reducing the number of microorganisms. Cleaning is a physical act, such as scrubbing with a brush or spraying with a hose, while sanitizing involves introducing a chemi- cal agent that will kill yeast, bacteria and mold. It is important to remember that without thorough cleaning, no sanitizer will be effective (see photo above). The Environmental Protection Agency defines sanitizing as a 99.9% or 3 log reduction in the number of microorgan- isms. Barrels are a challenge to both clean and sanitize because of the small access point (the bung hole), the porous surface and the risk of ruining the wood. Tartrates are the most abundant KEY CONCEPTS • Cleaning is removing dirt and debris, while sanitizing is a 99.9% reduction in microorganisms. Cleaning is an essential first step before any sanitizing can occur. • Sanitizers have different charac- teristics and perform differently. Carefully monitor concentrations and/or contact times to ensure effi- cacy. • Proper protective equipment and ventilation is required when using any sanitizer An In Vivo Study Oak barrels are expensive, made of porous, layered wood, and inevitably harbor microorganisms. Sanitizing them can be a challenge. PHOTOS BY CHELSEA GALLUP Maria de Lourdes Alejandra Aguilar Solis, Chris Gerling and Randy Worobo, Department of Food Science, New York State Agricultural Experiment Station, Cornell University, Geneva, N.Y. BY Barrel interior before treatment. Note the obvious tartrate accumulation, indicating insufficient cleaning. Environmental Bre anomyces isolated from "naturally" contaminated barrels. PHOTO BY MARIA DE LOURDES ALEJANDRA AGUILAR SOLIS