In Jewish tradition wine is considered a holy beverage. The blessing over the wine—or Kiddish—is an important part of many religious ceremonies. For this reason, a kosher wine at its most basic level is one handled only by strictly Sabbath-observant Jews. In addition, kosher wine makers are forbidden to use any products, such as unauthorized yeasts or other potentially non-kosher ingredients that might fall outside the parameters of kosher convention.
Aside from the constraints mentioned above, there needn’t be any difference between the techniques used to make a fine kosher wine or a fine non-kosher wine. That is, unless the kosher wine is to be designated mevushal, perhaps the most misunderstood term in kosher wine tradition.
In Hebrew, mevushal means literally, cooked or boiled. However, mevushal wines are not quite heated to a boiling temperature. They are nonetheless flash-pasteurized to a temperature that meets the requirements of an overseeing rabbinical authority. This technique does not necessarily harm the wine. In fact, a few well known non-kosher winemakers believe flash pasteurization may enhance aromatics.
In Jewish tradition, creating a mevushal wine alters its spiritual essence. This makes the wine less susceptible to ritual proscription. That means anyone—whether kosher or not—can open a bottle of mevushal wine without affecting its kosher status. That’s a plus for kosher catering halls and restaurants, where the wait staff may not be kosher or even Jewish. By contrast, non-mevushal, or non-heated wines, are viewed as more sensitive to religious constraints and should be opened and poured by Sabbath-observant Jews.
So what happens when a non-Jew or a Jew who is not kosher opens a kosher wine that’s not mevushal? Well, to be honest, not much. Since non-kosher individuals don’t follow kosher rules anyway, they are not particularly affected by ritual law. However, if they are sharing a non-mevushal wine with friends who keep kosher, then the wine typically should be opened and poured by a Sabbath-observant individual if everyone wishes to partake. Those are the rules; pure and simple. That said, not everyone follows the rules in the same way. Ultimately, mevushal wine is neither more nor less kosher than non-mevushal wine. These are two separate designations for equally kosher wines.