2,386. When Wine Can Become Prohibited

Maachalos Assuros 11:10

Regarding Jewish wine into which a little honey or yeast got mixed, the western Geonim ruled that since it’s no longer fit for the altar, it’s the same as boiled wine or beer in that it wouldn’t be used as a libation. It’s therefore permitted to drink it together with a non-Jew.

Maachalos Assuros 11:11

Non-Jewish wine becomes prohibited when the grapes have been crushed and the juice begins to flow, even though it’s still in the wine press and hasn’t yet descended to the vat. Because of this, we may not crush grapes in a press together with a non-Jew out of concern that he might touch it with his hand and offer it as a libation; this would be the case even if he were tied. We likewise don’t buy a press with crushed grapes even though the wine is still mixed with seeds and skins and hasn’t descended to the vat.