Kosher wine is wine that is produced according to Jewish laws regarding dietary practices. The body of Jewish laws that govern the production of kosher foods is known as Kashrut, meaning fit for ritual use. Jewish rabbis do not typically bless foods such as kosher wine to make them acceptable, though they will often examine food and its source to determine this. Though many foods such as kosher wine are accepted to be used for daily, year-round consumption, on Jewish holidays such as Passover, only certain accepted foods must be consumed and this includes special wines made kosher specifically for Passover.
Simply put, kosher wine only receives the label if the entire production process for the wine has been handled by Orthodox Sabbath observant Jews. As well, the wine must only contain recognized kosher ingredients. Therefore, kosher wine production has to encompass everything from the vineyard itself and its laborers, including Jewish laws as to the proper use of land for vineyards, to the ingredients added to the wine and the process of making it.
Where the special case of Passover comes into play, Jewish law states that leavened products cannot be consumed on Passover, and, since most wines employ yeast in the manufacturing process, they are not considered kosher wines suitable for Passover consumption. Other ingredients that would make a typical kosher wine not suitable for Passover include acids such as citric acid and tartaric acid. There are, however, kosher versions of all these ingredients to overcome this limitation.
Several American organizations exist to establish the kosher nature of foods in the United States. These include the Orthodox Union (OU), OK certification led by Rabbi Don Yoel Levy, and Star-K certification led by Rabbi Moshe Heinemann. Authoritative rabbis who are poseks, decisors of Jewish law, are also allowed to determine if a food is kosher.
Restrictions on kosher groceries, in particular kosher wine, is tied to cultural elements in Jewish history. Since fermented grape products have commonly been used throughout history by many cultures, which, from Jewish perspective, were practitioners of idolatry and pagan sacrifice, it receives unique attention. These kosher restrictions also include grapes used to make grape juice, and fruit juices in general, which are often sweetened with grape juice. As well, cream of tartar, which is a by-product of wine making, is often added to baking soda and therefore must be certified as kosher before being used in Jewish baking. Additional alcohol products that now contain fruit juices, such as fruit-flavored beers, must also come under inspection to be classified as kosher.