19. When making sourdough bread, it is common to prepare a separate dough for each loaf or two in a separate dish. E.g., 1000 grams of flour are placed in each dish together with the starter, and then two loaves are formed. The same is done in a second dish. In other words, in the dough stage, no one dish contained enough flour to require hafrashas challah. However, when they are all subsequently baked simultaneously in one oven, the bread might combine for a chiyuv hafrasha inside the oven, which is a container that can combine them. Similarly, perhaps they all combine for the shiur after baking if they are all placed into one bag or box, or into the freezer, which is a כלי if it does not have a capacity of forty sa’ah (above, 8). Then, all the loaves combine to require hafrasha.
20. Combine them. Due to these concerns, it is advisable to combine the loaves at some stage so that they all require hafrashas challah and will not get into shailos about combining.
21. Dough stage. One way to combine them for hafrashas challah is via נשיכה , i.e., stretching some dough from one dish and attaching it to the dough in another dish so that the two are connected. If there are three or four separate dishes, all the doughs are connected through a piece of dough between them. Then, challah is separated from one loaf to make all the loaves potur.
22. After baking. Another way to combine the loaves can be done after baking. I.e., the loaves are placed together in one box or bag such that they are all completely contained within the box’s interior, and then challah is separated from one of them. When one intends to do this from the outset, he can set aside a small piece of dough before the baking to be the hafrashas challah after the loaves are baked. This way, instead of cutting into any of the challos, one can use the small piece he set aside ahead of time for the hafrasha.
23. Bracha on hafrasha after baking. When doing hafrasha after the loaves are baked, the regular wording, “להפריש חלה מן העיסה,” is not said, as the loaves are no longer dough [עיסה]. Instead, the bracha is “להפריש חלה.”
