I read the article about challah in the Tishrei edition and found it very informative. I own a small start-up bakery and I often have some leftover dough from previous dough mixes (from which I have already taken challah) and I would like to mix it in to my new batch of dough. Do I have to wait until we take challah from the new dough in order to mix it in, or can I mix it in before I take challah? What should I do if we mistakenly added the dough before taking challah?
Rabbi Chanowitz responds:
You are correct. One should only add the leftover dough after you have taken challah from the new batch of dough.
If you inadvertently mixed in the old dough before taking challah, the concern is that if you take challah from this mixture, the piece of challah dough may have been from the old dough (from which you already took challah). This is problematic since it is “min hapotur al hachiyuv” (using something not obligated to perform the obligation). Therefore, it is best to take challah from a totally new batch of dough for this one “min hamukaf” (from the immediate area). If this is not possible, you can take challah from the dough in question, and rely on the opinion that the two dough mixes blended well together so that the challah dough has some of the new dough which is obligated in challah.
The same applies to those bakeries that use live yeast from sour dough of old dough mixes. One should make sure that the yeast comes from dough that has not had challah taken. This is most difficult after Pesach, since the yeast was sold to a non-Jew, and non-Jewish dough does not require that challah is taken. The solution is the same as the above. One should make a new batch of dough without yeast and take challah from it. If this is not possible, then one can take challah from the dough in question. In this case, the size of the challah should be larger than the amount of sour dough used. (See Shulchan Oruch, Yoreh De’ah 324:11 and commentary for details.)