|(Yoon S. Byun/Globe Staff)|
About kegs and kegging
Small stainless steel barrels have long been used by wineries to store small lots of wine. They are also used in the process of “topping off’’ wooden barrels, the technique of adding a little wine to each barrel to keep oxygen from occupying the space created by evaporation. The current trend for tapping kegs may have gotten its start in a few Northern California restaurants where proximity to wineries made the logistics relatively simple.
Kegs used in wine service are typically made of high-grade stainless steel, although reusable food-grade plastic is becoming more common. All connections must also be stainless. Hardware used to provide draft beer is not suitable for wine. A full-size wine keg typically has a capacity of 19.5 liters, the equivalent of 26 standard-size bottles. As wine is drawn off, the system injects a shot of odorless, tasteless gas (usually nitrogen) which fills the vacated space and seals the wine off from the destructive influence of air. Kegs must be very carefully cleaned and sanitized between uses. The latest development: single-use kegs made of recyclable plastic.
The system has long been in wide use in European bars, and wine shops there provide fill-your-own-jug service. These wine stations often pump three grades: the equivalent of regular, plus, and premium.