How hot is hot food?

[zevabe]

According to Rabbi Mordechai Willig of YU, a liquid which has cooled on Shabbat beyond the point of being served as hot food may not be reheated.  He admits this is contrary to the opinion of his contemporaries, who say that as long as it has not cooled completely, usually understood to mean that it is still above room temperature, it may be returned to the heat, subject to all of the other conditions of returning food.  (Perhaps another time I'll discuss all of that more fully, but not just now).

So how hot must liquid foods you enjoy eating be to be considered hot enough to eat as such?  For example, iced coffee is very nice, but if i ordered coffee and they brought be coffee at room temperature, I'd object in some way. Temperatures may vary for different foods, which is fine.

Foods of particular interest:

1. Coffee/Tea
2. Soup
3. Cholent/Stew
4. Gravy/Sauce on something else
5. Anything else you think Yeshiva University students are likely to eat on Shabbat

I know that food must be kept for safety reasons at 140 F or above for hot-holding.  However, it need not be served at this temperature, especially by the home chef, because it will not sit at the serving temperature for an extended period.  Also, the temperature at which coffee or tea are brewed need not be the temperature at which they are served.

"Accordingly, I have no doubt that tea and coffee served at between 55 C and 60 C would not have been acceptable to McDonald's customers. Indeed, on the evidence, I find that the public want to be able to buy tea and coffee served hot, that is to say at a temperature of at least 65 C, even though they know (as I think they must be taken to do for the purposes of answering issues (1) and (2)) that there is a risk of a scalding injury if the drink is spilled."["^ a b Bogle & Ors v McDonald’s Restaurants Ltd. [2002] EWHC 490, at 33 from http://en.wikipedia.org/wiki/Liebeck_v._McDonald's_Restaurants

Answers.com reports the temperature for hot tea as 60-90 C.