Chagiga 25b at the top
Rashi explains that the chover who yarshens his father, can take the tohor wheat in exchange for the huchshar lekabel tumah wheat. But what does the mishna mean in the following line: "he can take wine kneged wine" there is no such thing as wine which is not yet huchshar lekabel tumah. So all the wine is the same for this chover, its all treif??
Avrumi Hersh, London england
The sefer Menachem Meshiv Nefesh writes that the chover knows that the wine from the place which he wants to receive from was prepared by chaverim who are careful about taharah, and was in their reshuis and is still pure. So the wine is Glatt Kosher.
A freilicher Purim
Dovid Bloom
Alternative answer:-
1) It may also be possible to answer according to what the Mefarshim on the Mishnah in Demai 6:8 and 6:9 write that even though the Mishnah states "wine" this may in fact mean grapes. Mishnah 6:8 states that he can say " you take the wine in such and such a place..." and the Bartenura writes that this means grapes. The Tosfos Yomtov on Mishnah 9 DH Tol writes that the Mishnah cited here in Chagigah is referring to grapes. It seems that the words wine and grapes can sometimes be interchangeable. According to this possibly there is such a thing as "wine" which is not yet huchshar lekabel tumah; namely grapes.
2) I want to suggest a source that the use of the word "grapes" and the use of the word "wine" can sometimes switch around. This is from the 1st Mishnah in the 3rd chapter of Bava Basra (Bava Basra 28a). The Mishnah describes ways of receiving a Chazoka by doing 3 harvests. One of the examples is "Konas Es Tevuoso"; "he brought in his produce". Rashi writes that "tevuoso"; "his produce"; means the wine from the vine. It seems that he only reaped grapes; and did not necessarily make wine yet from them; but nevertheless is it called wine because of the end product. [see also Rashash there]
KOL TUV
Dovid Bloom
Some do not have this girsa:
1) The Meiri here does not have the text at all that mentions wine. In addition, the Dikdukei Sofrim here, which brings down different texts, writes that in some versions the girsa about wine does not appear at all.
2) So, basically, it appears that because of the problems raised by your question, some versions erased this text. The answer of the Menachem Meshiv Nefesh is probelmatic because one has to say that even though the wine belonged to an Am HaAretz, it was continuosly guarded by Chaverim, which is somewhat forced. In addition, there is clearly a problem in saying that wine means grapes, and in addition the Bartenura etc, that I cited above write the grapes are still attached to the ground, which is obviously surprising.
This may be why some changed the girsa.
Dovid Bloom