If the sages were so concerned that interaction between Jew and Gentiles over a glass of wine could lead to inter-marriage, why did they not interpret the law to prohibit all consumption of wine in any situation where Gentiles were present? Clearly the intoxicating effects of the wine do not depend on who produced it or who owns it or whether it is mevushal.
Also, if a Nochri visits a Jew and takes a glass of Kosher, non-mevushal wine from the hand of Jew who is shomer shabbat etc., will all of the wine loose its kashrut, or will only that portion in the glass (actually touched by the Nochri) be affected?
The practical implication of this question has developed from the fact that many Kosher wines today are not mevushal. Will the non-mevushal wine of an observant Jew who invites a Gentile to his home for dinner loose its Kashrut simply because the Gentile handles that portion that is given to him for his dinner?
(Assume the host is observant and knowledgable enough to pour the wine for the guest and to cork the bottle before giving the guest the glass of wine. Perhaps the host even washes his hands before serving any more wine from the bottle.)
Scott S. Widitor (Shalom Shmuel), Beverly Hills, CA, USA
[This response should not be construed as a Halachic ruling on the question. Rather, it is an exploration of the topic to help our readers become more familiar with the issues involved.]
The intoxicating effects of the wine are not what Chazal were concerned about. They were concerned about a certain closeness that is wont to develop towards hosts who serve wine. Additionally, a wine that is Mevushal was not known to generally be a fine wine, and in the time of the Gemara was not used to develop closeness. This is changing in today's day and age, which is part of the reason that R' Elyashiv shlit"a holds that the Mevushal process in today's wine plants does not change the Halachic status of the wine (something held by many Poskim in Eretz Yisrael, unlike many Poskim in America).
If the Nochri touches the actual wine it is forbidden. There are definitely Halachic complications for a host to pour wine into a glass being held by a Nochri. He may pour the wine into a glass and then give the glass to the Nochri (though that wine promptly becomes forbidden as it now belongs to the Nochri, the rest of the bottle definitely does not).
[I hope this response has clarified the issue. For all practical questions on the issue, please consult your local Orthodox rabbi.]
All the best,
Yaakov Montrose