The gemara asks a question based on a mishna that describes someone tasting a barrel of wine to see if it is still wine and not vinegar. I do not understand how it is permitted to taste this wine, since as I understand it, either what he is tasting is tevel (which he wants to use as teruma on other barrels), or what he is tasting is already terume. In both cases, isn't there a punishment of 'mita bidei shamayim' for drinking it (assumin he is not a kohen)?
Shimon, Iha"k!
1. The Ritva here writes that he tests the barrel by smelling, or alternatively he pours from the barrel into another cup.
2. Tosfos in Bava Basra (96a, DH ha'Bodek) explains further. It is possible to "taste" it by smelling, and if it smells like wine then it certainly is wine. Tosfos cites the alternative way in the name of Rashbam that he takes a small amount of wine from which he separates Terumah and then he tastes it.
3. The Mahari Kurkus (on Rambam Hilchos Terumos 5:24) cites the Talmud Yerushalmi in Gitin (end of Perek 3) which states that there are some people who are capable of knocking on the outside of the barrel and thereby determing whether the contents are wine or vinegar.
4. The author of the footnotes to the Ritva here (note 48) cites the Tosfos Chachmei Angliyah who says that he tests the barrel through a "Kefeila." A similar idea is mentioned by the Gemara in Chulin (97a). This refers to a Nochri who tastes food which may be forbidden in order that a Yisrael should know whether or not the forbidden part has transmitted taste to the permitted part. If it has, the food would be prohibited. In the case of the Gemara here, the Kefeila tests the barrel to decide whether it is wine or vinegar.
5. It is not clear what Rashi's opinion is concerning the above possibilities. Rashi writes that he tastes it, but we saw above (in 2) that Tosfos seems to say that smelling is also considered "tasting" for these purposes, so it is possible either that Rashi learns like his grandson, the Rashbam (mentioned above in 2) or like Tosfos.
Kol Tuv,
Dovid Bloom