The Magen Avraham (s.k. 1), Elyah Rabbah (s.k. 3) and Shulchan Aruch HaRav (sif 1) all bring that if the wine is left uncovered לשעה מועטת - for a short amount of time, and the taste and smell has not been ruined then the wine may be used for kiddush. The question is, how long is this short amount of time, and is it lechatchilah or bedieved?
The Shu”t Divrei Malkiel (4:1) understands that שעה מועטת is anything up until twenty minutes, and anything less than that is perfectly lechatchilah.
However, R’ Elyashiv understands (Kovetz Teshuvos 3:45) that leaving the wine uncovered even for a few seconds is already a problem.
When the Mishnah Berurah (272, s.k, 3) brings this halachah he writes: If the wine was left uncovered for a שעה מועטת nowadays, we aren’t concerned if the taste and smell hasn’t been ruined. However, he then cites the Chayei Adam which says: This is only in a place where wine is expensive, and since wine is expensive we aren’t worried if the wine was left uncovered for a few moments, however, if one would make kiddush on beer which is cheap then one should be more careful. The fact that the Mishnah Berurah quotes the Chayei Adam, and says that the only reason we are lenient is because wine is expensive, nowadays, I think it’s safe to say that wine can be purchased relatively cheaply (in most places), therefore, according to the Mishnah Berurah one would need to concerned for leaving the wine uncovered even for a short amount of time. This is also how R’ Binyomin Zilber zt”l understands the Mishnah Berurah in Shu”t Oz Nidberu (1:7).
The Mishnah Berurah adds that if one has nothing else to use for kiddush, then one shouldn’t be makpid [particular] even if he is using beer. So, if one only has one bottle of wine, it seems he can be lenient. If, however, one has another bottle of covered wine at home, it would seem that since nowadays wine is relatively cheap one should make sure to use the covered wine.
Dayan Gavriel Kraus shlita (Manchester) disagrees with this and holds even today leaving wine uncovered for a short amount of time is lechatchilah. The Teshuvah of R’ Binyomin Zilber where he agrees to my understanding of the Mishnah Berurah was written to Dayan Kraus about this exact point. I spoke to Dayan Kraus to see if he still stands with his opinion, and he told me very clearly that he still considers wine to be expensive today and that leaving it uncovered for a short amount of time would be ok.
It's unclear why he disagrees and understands that wine is still considered expensive today, but from what I understood, I think he held that since people are still careful to cover their bottles of wine and not leave them uncovered like they would by water, it is still considered expensive.
Alternatively, it could just be that the value people give to things in todays day and age has significantly dropped. For example, R’ Moshe Feinstein rules that a blank piece of paper is considered muktzeh machmas chisoran kis, as no one with any da’as would waste such a thing. In today’s day and age, I don’t think many people understand this. Therefore, perhaps the same thing is with wine, although here in Eretz Yisroel one can purchase a bottle of wine for 15 – 20 shekel, it is still very valuable and expensive.
