Beginning with the Mishnah on daf (page) 55a, Masechet Avodah Zarah begins to focus on the laws of yayin nesekh – wine forbidden to Jews because it has been sacrificed as a libation to pagan idols. Due to this concern, the Sages forbid all wine with which non-Jews come in contact. The Mishnah teaches that as long as the grapes are still in the process of being squeezed in the wine press – even if there are non-Jews who are touching the grapes and placing them in the press to be tread upon – they will not be considered to have become yayin nesekh. The juice is only considered to have become wine when it flows out of the press and into the collection vats.
In the Gemara, Rav Huna argues that the ruling of the Mishnah is not final, and that it is the teaching of Mishnah rishonah– “the first Mishnah.” A later rendition of the Mishnah prohibits use of the wine as soon as it is squeezed and has begun flowing, even if it remains in the press.
In the continuation of the Gemara on today’s daf (=page) Rav Huna is quoted as teaching that the juice in the press remains permitted only if the basket that strains out the pits and sediment is not returned to the press. If the straining basket is put back into the press, then all of the juice in the press will become forbidden.
Many of the commentators argue that in this ruling, Rav Huna is explaining the position of the Mishnah rishonah, according to which the juice in the press would ordinarily remain permitted. The Ramban, however, understands Rav Huna’s original ruling differently, and the juice in the press, which is not yet considered to be wine, will not become forbidden simply because it flows into the wine in the collection vat. Adding wine from the straining basket to the juice in the press will prohibit all of the juice.