While preparing Bava Basra 95, I was struck by how different our view of wine is today as opposed to the time of the gemara.
The mishna on Bava Basra 93b stated that one who contracted to purchase wine was required to accept 10% of the wine as "kossisos." The Rashbam on Bava Basra 95a explains that this was wine which was starting to go sour (but was still drinkable) and was the common wine which was sold by shopkeepers for immediate consumption.
The gemara on 95a contains a discussion as to which type of wine the seller intended to buy which would require that he accept 10% kossissos. As the discussion spills over onto Bava Basra 95, the gemara offers an opinion that when a buyer indicates that he wishes to use the wine to cook with, there is an obligation on the seller to provide him with superior quality wine. The Rashbam explains that wine which was used for cooking needed to last for a significant period of time as it was not rapidly used by the buyer. As such, the seller could not provide kossissos wine since it would go completely sour before the buyer will have exhausted his cooking needs.
In contrast to the gemara, when someone in this era buys cooking wine, the product is usually of the poorest quality since people do not use fine quality wine to cook with.
Still, there was one point made by the gemara which still rings true today. The gemara on the bottom of 95b discusses a dispute as to whether one who consumes wine which is truly going sour must make the heightened brocha of borei pri ha'gafen or only the shehakol. As part of this discussion, the gemara mentions R' Zevid's position that wine which is pressed from grape kernels is of such poor quality that one would recite the shehakol blessing. The Rashbam describes such wine as "extremely bad" which would only be sold in the outer corners of the city. Yes, even in the times of the gemara there was a "thunderbird" wine which you needed to be desperate to drink!
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