Avodah Zarah 30 - Cooked Wine and Wine Left Uncovered
If wine is cooked by a Jew, then it never becomes prohibited as "wine of libation." The possible explanations of this are that cooked wine was not used in religious rites, or that cooked wine is an unusual case, and Sages did not promulgate decrees in unusual cases, or that it simply is not wine, but "cooked wine."
The Sages prohibited the consumption of wine, water, or milk that was left uncovered, for fear that a snake may have drunk from the liquid and cast its venom into it. The prohibition is based on the requirement to take great care of one's health and well-being . Today, when snakes are not prevalent, the prohibition does not apply, though some say that it has additional mystical connotations. In any case, it does not apply to cooked wine, because a snake would never drink such wine.
Art: Heinrich Stelzner - The Winetaster