Question: This past Shabbat, my daughter brought a tray of hot soufflés to the table and because it was so hot, someone told her to put it down on the pitas so as not to ruin the table. Was this permissible?
Answer: The Gemara (Berachot 50b) and Bet Yosef (Chapter 171) state that one may not use bread if it may get ruined as a result of this usage. However, one may use bread in a way that will not ruin it. Indeed, the Shulchan Aruch rules: “One may use bread for one’s own purposes as long as this does not cause the bread to become repulsive. However, if it does, one may not use the bread.”
Thus, the Shulchan Aruch adds, “One may not place raw meat onto bread and one may likewise not pass a cup completely full of any beverage over bread. One may also not support a dish of food with bread if it is filled with something that will make the bread repulsive if it spills onto it.”
Thus, regarding our question above, if the tray is clean which will not ruin the bread when placed on it, it will be permissible to do so. However, if the tray is dirty and this will ruin the bread when placed on it such that people will not eat it anymore, the tray may not be placed on the bread.
However, all this applies only to a tray containing cakes and other items which, even if they fall on the bread, will not ruin the cake or make it repulsive. However, if the tray or dish contains a food that will make the bread inedible or ruined if spilled onto it, such a tray may not be placed on the bread, even if it is clean. One must be exceedingly careful not to ruin the food Hashem has given us.
Summary: One must take care not to ruin bread. However, if one wishes to use bread in a way that does not ruin it, such as placing a clean tray containing cake onto it, one may do so.