Another bit of information from wine guru, Karen MacNeil:
Dear Karen: Why do zinfandels always seem to be high in alcohol? I often see zinfandel labels indicating an alcohol content of 15% or more.
Dear Reader: There are two reasons for zinfandel’s higher alcohol level. First is the current (and, in my opinion, unfortunate) trend across the board toward higher-alcohol wines. Wines with high alcohol have a full body and feel powerful in the mouth—traits that often win high scores.
The second reason, however, is perhaps even more important. Zinfandel has a genetic proclivity to ripen unevenly. On the same cluster, some grapes will be perfectly ripe, others will be underripe, and still others will be so ripe that they’re virtually raisins. If a winemaker picks clusters like this, there’s a chance the wine will taste discombobulated, both unripe (green) and overripe (pruny). To avoid this unevenness, most winemakers let zinfandel clusters hang on the vine until all the unripe grapes become perfectly ripe, at which point some of the perfectly ripe grapes have become raisins. During fermentation, yeasts convert this abundant sweetness into considerable amounts of alcohol. Thus many zinfandels can’t help their potency.
Previous tips from the Page-A-Day calendar by Karen: One, Two, Three, Four, Five