What makes a wine kosher?

Hello there! I'm Dr. Vinifera, but you can call me Vinny. Ask me your toughest wine questions, from the fine points of etiquette to the science of winemaking. And don't worry, I'm no wine snob—you can also ask me those "dumb questions" you're too embarrased to ask your wine geek friends! I hope you find my answers educational, empowering and even amusing. And don't forget to check out my most asked questions and my full archives for all my Q&A classics.
Dear Dr. Vinny,
What makes a wine kosher?
—Glen, Charleston, W.Va.
Dear Glen,
Kosher dietary laws regulate how foods are prepared and served. Kosher wines follow normal winemaking procedures but must adhere to some additional procedures. The most important rules are that it must be made under the supervision of a rabbi, use rabbinically certified equipment, only contain kosher-certified ingredients, and have no added preservatives. That last point about no added preservatives sometimes confuses wine lovers into thinking “kosher” and “organic” are interchangeable terms, but they are not. There are different specifications for organic wines. Here are more details about kosher wines, and Wine Spectator School even offers a class in Kosher ABCs of Wine Tasting.
In the past decade or so, more and more kosher wines have been produced from wine regions all around the world. And they are rapidly improving in quality; today, you couldn’t pick out most kosher wines in a blind tasting because they taste like “regular” wines. There are fine bottlings of kosher Champagnes, Bordeaux and Napa Cabernets, for example. Israel is probably the source of the most kosher wines, and they are worth trying even if you don’t keep kosher.
—Dr. Vinny