By: The OU Kosher Halacha Yomis Team
To what types of flour does the mitzvah of hafrashat challah (separating a piece as challah) apply, when formed into dough?
Shulchan Aruch (YD 324:1-2) lists five species of grain that require hafrashat challah: wheat, barley, spelt, oats, and rye. In addition, if one eats bread made from these grains there is an obligation to recite Birkat Hamazon, and the mitzvah of Matzah at the Seder can be fulfilled with matzah that was kneaded with these five grains.
There are various grains that are included in the wheat family. For example, kamut (Khorasan wheat) and durum (semolina flour) are varieties of wheat. Buckwheat, in spite of its name, is neither a species of wheat nor one of the five grains.
The mitzvah to separate challah only applies when the batter is made with a specific shiur (requisite amount) of flour. (More about the shiur on this page.) The outer husk of the grain does not require separation of challah, and it cannot be counted towards a shiur of flour that is required for the mitzvah. Bran (the outer layer of the grain) can be counted towards the shiur, so long as the bran was milled together with the rest of the grain and was not removed. However, if the bran was separated from the flour, even if it is later reintroduced back into the flour, it can no longer be counted towards the shiur of flour (Shulchan Aruch YD 324:3).