Commentary for Avodah Zarah 132:2

Rava says that even though the wine smells like vinegar, it is wine and therefore this is a case of two different species being mixed together. In such cases the prohibited substance must impart a taste for the mixture to become prohibited.
I should note that were it not for the Talmud I would have explained the debate in a much simpler way. The taste of vinegar is much more pronounced than wine. So when vinegar falls into wine, we can use the taste test. But when wine falls into vinegar it would require a very large amount to nullify the taste of the vinegar. Therefore the taste test won’t really work. So the amoraim debate whether it should be used in any case.