The milling of grains has been going on for millennia, and in all that time, the process has not changed dramatically. Milling is still done by simply grinding kernels, albeit with rollers instead of stones. Sifting is still done with sifters, although by automated machines instead of by hand. There is another part of milling known as tempering. Tempering refers to spraying grain kernels with water before they are milled. This makes the bran tougher and less brittle. If the wheat kernel has not been tempered, the bran may shatter and leave brown flecks (“ash”) in the flour when the kernel is milled. This is undesirable in regular white flour. Tempering strengthens the bran so that it is removed from the endosperm easily and does not cause brown flecks in the flour.
Tempering has several Halachic implications. First, all tempered grain and any flour made from the grain are possibly Chometz Gamur. Secondly, tempering makes the kernels “Muchshar Likabel Tumah”, capable of becoming tameh. This directly impacts Hafrashas Challah. When one makes a dough and takes off Challah, the Challah, which is considered Terumah, is normally burned. This is because it is considered to be Terumah Timayah, which must be burned. If it had been Terumah Tihorah, it would be forbidden to be burned, and would need to be given to a Cohen who is a minor, or be left to rot until it becomes inedible. The way dough acquires tumah is as follows: A person’s hands are considered tameh. Thus when one’s hands touch dough, the dough is rendered tameh. This is only possible if the dough had previously been Muchshar Likabel Tumah. In order for that to occur, the dough must have come in contact with one of seven liquids which include water. For example, when one is making bread, the water added to the flour makes the dough Muchshar Likabel Tumah. If however one is making a cake where no water is added, then the dough would not be Muchshar Likabel Tumah. Nonetheless, the common thinking is that since our wheat is tempered, the wheat will have become Muchshar Likabel Tumah while it was a kernel. Whether this is in fact true and whether it applies to all grains will be discussed later in this article.
The Gemara (Pesachim 40A) states that it is forbidden to be “Loseis”, which means to temper grain if it is to be used to make Matzos for Pesach. The Liseesah of Talmudic times involved pouring water on grains, mixing them together to help remove the bran, and then grinding it immediately. The Gemara goes on to say that if one was “Loseis” the kernels, they would only be forbidden bidieved if we saw that the wheat kernel had cracked. When a wheat kernel is about to germinate, the top part of it cracks open and soon begins to sprout. Once a kernel sprouts (“Mitzumachos”), it is considered Chometz Gamur. When the kernel has cracked but has not yet sprouted (“Bikuos”), the kernel is considered a Safek Chometz and is forbidden to be eaten on Pesach. If one did not sell it before Pesach and it was owned by a Jew, it would be forbidden even after Pesach as Chometz Shehavar alav haPesach. (The picture shows an uncracked wheat kernel next to a slightly sprouted kernel).
The question raised by the Rishonim is that the Gemara (Pesachim 40B) states that if wheat kernels were on a boat which drowned in a river and were subsequently retrieved, they would be forbidden to be eaten on Pesach. In contrast to the previously mentioned Gemara, there is no qualification here as to whether the kernels were cracked or not. Rabbeinu Ephraim, quoted by the Rosh (Pesachim 2:27) answers this apparent contradiction by suggesting that the reason kernels that have been subjected to Liseesah are only forbidden if they are cracked is that during the Liseesah process, the wheat is constantly worked with and is then milled immediately. In the case of the sunken kernels, they have simply been allowed to sit in water without being worked on. In such a case, the kernels are forbidden even if they did not crack. This view is accepted by The Shulchan Aruch (O.C. 467:2). The Hagahos Maimonis (Hilchos Chometz Umatzah 5:6) suggests an alternate approach. According to him, the difference between the two cases is that Liseesah only involves a relatively small amount of water (“zileefah muetes”) whereas the kernels that drowned in the river were subjected to a very large soaking of water and are therefore forbidden even without any cracks. While, as mentioned, this is not the view of the Shulchan Aruch or Nosei Kaylim (see Taz 467:3), this view is cited by the Biur Halacha (467 D.H. Dagan Zeh). Quoting the Beis Meir, the Biur Halachah says that one could rely on this view to eat such kernels (i.e. non cracked kernels which were exposed to a small amount of water and not worked with) or the flour made from them on Pesach in a case of great loss.
We now need to describe the contemporary tempering process in slightly greater detail. When wheat kernels are received by the mills, they are cleaned with air, and then sent to a temper machine. The temper machine has rotating paddles which throw the kernels around while a nozzle sprays them with water. The paddles turn at great speed, allowing the water to penetrate the kernels as quickly and efficiently as possible. Any given kernel will stay in the machine for about 10 seconds. After it exits the machine, the kernel is damp, but barely so (I personally felt the kernels immediately following their exit from the tempering machine. They were damp but just barely. No moisture droplets were visible.) The wheat is then sent to empty temper bins where they simply sit for 8-32 hours to give the water time to evenly penetrate the endosperm. At this point in the process no water is added. The kernels do not generally crack as a result of tempering.
In light of the above, it would seem that these kernels should not be consumed on Pesach. They are, according to Rabbeinu Ephraim and the way the Shulchan Aruch has ruled, a question of Chometz even if they are not cracked since they had been exposed to water and had not been worked with but rather left to sit. However, for those who do not wish to sell chometz gamur, selling flour would still be permissible as the kernels do not crack, and are therefore just a safek chometz. Moreover, even if one did not sell their flour at all, there is room to permit using the flour after Pesach. This is because the water is only exposed to a “Zileefah Muetes” such as that done by liseesah. As such, according to the Hagahos Maimonis, it could even be consumed on Pesach. While we do not follow this view, the Biur Halachah allowed its use in a case of great loss on Pesach itself. As such, in regards to the Rabbinic penalty of Chametz Sheavar alav haPesach, it would seem that there would be room to permit use of the flour. Rabbi Belsky agreed that we could permit the flour after Pesach.
Our discussion until this point has focused on wheat kernels being milled for regular white flour. Whole wheat flour may also have been tempered to keep the bran from becoming brittle, although with less water and for a shorter period of time (this is because brown flecks are not as undesirable in whole wheat flour, though there are other benefits to tempering.) Rye and spelt kernels, however, are not tempered at all. In fact, they are not exposed to moisture of any kind. As such, they could be purchased after Pesach without question from someone who did not sell their chometz. (We generally require kernels to be milled with “shemira” if they are to be used for Pesach, so regular non shmura rye and spelt flour should not be consumed on Pesach itself.) The exception to this is flakes. Rye and spelt made into flakes (not flour) are exposed to moisture and must be sold for Pesach.
While the lack of moisture on rye and spelt is good for Pesach, it is more problematic for Challah. If one were to make a spelt cake where no water was used, the Challah taken from that would not be allowed to be burned since it was not Muchshar Likabel Tumah. In such cases, a small amount of water should be added to the dough to avoid this issue. As mentioned previously, wheat kernels used for making regular flour are always tempered (wheat kernels used for making whole wheat flour may not have been tempered). The moisture applied during the tempering process is sufficient to render the wheat kernels and flour Muchshar Likabel Tumah.
Oats and barley are not tempered either (except when they are made into flakes). However, oats, and sometimes barley, are steamed before being milled. This process prevents the oats from going rancid due to their high fat content. It also effectively eliminates the possibility of germination. This process would render the oats Muchsar Likabel Tumah, and thus would not require the addition of water to be able to burn Challah taken from oat dough. Further, it would seem that this process would be similar to the process of Chalitah which renders wheat incapable of becoming chometz. While we normally do not allow Chalitah (Shulchan Arcuh 453:5), if Chalitah was done, the flour would be permissible after Pesach.However, upon further research, it was determined that although the steam temperature is 212F, the oats themselves only reach a temperature of 180F before they are dried. Consequently, Rabbi Belsky felt that even though the steaming itself negated any possibility of germination, it would not be considered a form of Chalitah and would not prevent the kernels from being considered Chometz.