Why can't we have challah in the oven with other food?

Question

I am talking about halachic challah -- the portion taken for the offering. I was taught several times that these days, what to do with it is to burn it to a char in the oven. I also learned that this should be done separately from other foods (source: Halacha section of the Bais Yaakov Cookbook). This is actually a big challenge erev Shabbos, when one is short on time and has a lot of food to cook.

1) Is it true that mitzvah challah must be put in the oven alone?

2) If so, why?

I had thought that the reason for this was that the challah is treyf, but on second thought, that wouldn't make much sense (since we cover it completely anyway; plus, if there were in fact a problem of trefus, cooking it without other foods in the oven wouldn't help much for the kashrus of the kitchen--although there may be some nuance in that matter, possibly related to steam). But a rabbi at my seminary mentioned that it actually may be because we can't derive benefit from the challah, and if we kept it in the oven with other foods, it could be fuel for their cooking.

I understand how that could be true if challah were put in a fire with other foods being cooked above. But how could it possibly be true in an oven? If it couldn't, and that's not true, then what is the explanation for why the challah must be in the oven alone?

Answer 1

According to the OUKosher.org website if the Challa is completely wrapped up one may bake other items in the same oven. This is based on Shach (Yoreh Deah 108:1) who quotes from the Issur V’heter that one may bake bread in the oven while the challah (even uncovered) is burning. However, the Aruch Ha’shulchan (108:9) and others disagree and feel that the oven should not be used at all if the challah is uncovered.

May I use my oven while the Challah is burning? If the challah is completely wrapped up, one may bake other items in the oven while the challah is burning. However, if the challah is uncovered, it is best to avoid baking anything else in the oven while the challah is burning. If one accidentally did use the oven while the challah was burning, one may eat the food.

Answer 2

Challah is one of the matnas kehuna - gifts given to the Kohanim in recognition of their holy, dedicated service; while this is a mitzvah d'oraysa within the borders of Eretz Yisrael (considered to be a mitzvah talui ba'aretz) there is a rabbinic extension to chutz l'aretz as well. Additionally, kohanim as well as foodstuffs are assumed to be tamei nowadays which is why we burn the challah entirely rather than giving it to the Kohen (Rambam Hilchos Yom Tov 3:8).

interestingly, the Kitzur Shulchan Aruch (35:1) actually records the practice of destroying the challah in the same oven that the bread is baking! I have to check again to see if that meaas covered or uncovered.

However, the concern is that even while destroying the challah there will be some transfer of taste from the separated challah dough to the other foods in the oven. hence, the suggestion is to be cautious and either burn it alone in the oven entirely or to cover it up very well and leave it in there long enough for it to be rendered completely inedible.

A practical suggestion: if you own a toaster oven, double wrap your lump of dough and place it in there at the highest setting until it's destroyed. This will free you from logistical issues of using your oven to prepare other foods while discharging your challah obligation.