Daf ha-kashrus

CHaNaN Lach B’Lach

Vol. 23 / No. 1

by Rabbi Eli Gersten

The Mordechai (Chulin 697) writes that we do not say Chaticha na’ases neveila regarding sha’rissurim lach b’lach. Only when a chaticha (solid) absorbs issur, do we say that because of its chashivus, the entire mass is transformed into issur. But if liquid heter and issur are combined, the issur will remain proportional. The Ra’avad also agrees that we do not say CHaNaN lach b’lach, but for a slightly different reason. When issur is absorbed in a solid, it will not be absorbed and expelled uniformly; therefore once issur is absorbed the chaticha remains assur forever. However when liquids are combined, they form a homogenous mixture. The Rema (Y.D. 92:4) says that one may rely on the opinion of the Mordechai and Ra’avad in cases of hefsed mirubah, One should contact the office before making any decisions regarding what is considered a hefsed mirubah.


Pri Migadim (Kellalim B’hora’as Issur V’heter s.k. 6) writes that whenever Rema permits something b’hefsed mirubah and there are additional sfeikos to be maikel, then one can be maikel even when it is not a hefsed mirubah. Maharsham (6:91) and V’yan Yosef (Y.D. 37) write this explicitly regarding CHaNaN lach b’lach.

Lach b’lach b’issur d’rabbanan

Igeros Moshe (Y.D. II:36) writes that there is room to be maikel not to say ChaNaN by an issur d’rabbanan lach b’lach. However, he cautions against relying on this heter unless there is a tzorech. Likewise, the policy of the OU has been to use this only as a tziruf, or in cases of shas hadchak.


Regarding chalav akum lach b’lach, the OU does not say CHaNaN. This is because, in addition to the sevara of Rav Moshe zt”l, that we do not say CHaNaN lach b’lach b’issurim d’rabbanan, there is an additional tzad kula here as well. Pri Migadim (S.D. 97:1) proves that regarding chalav akum, we do not say CHaNaN lach b’lach. He explains that this is because regarding ChaNaN, we are also mitztaref those poskim that held that chalav akum is batel b’rov, and because chalav tamei is not common. This is even without taking into account modern-day sevaros of pikuach ha’memshalah, as discussed by Igeros Moshe (Y.D. I:47) and Chazon Ish.(Y.D. 41:4)


Rebbi Akiva Eiger (commentary on Shach 92:14) points out that there is a halachic difference between the position of Mordechai and that of Ra’avad, regarding a solid that absorbed issur and subsequently melted into a batter. According to Mordechai, once the chaticha became assur, it will remain that way forever, even if it eventually melts. However, according to Ra’avad, once the solid melts, it becomes evenly dispersed, so this will revert back to lach b’lach, which is mutar b’hefsed mirubah.

How should we consider kosher margarine that contains chalav stam (10%) that is melted into a batter, and the dairy component will be less than shishim? Is margarine considered a chaticha, or since it melts, should it be viewed as lach b’lach, and not require kashering (as per Pri Migadim). Rav Belsky has said that in this case, one could rely on the Ra’avad. Especially since in this case, the margarine started out as a liquid, so even according to Mordechai it is not clear that he would view this as having chashivus of a chaticha1. If the margarine contained animal fat, and it was a situation of hefsed mirubah, one should contact the office.

Cold mixtures

Taz (Y.D. 92:15) says that Maharshal held that one could only be lenient for lach b’lach when the mixture is cold, but if the items were cooked then the ordinary rules of CHaNaN would apply. However, Pri Migadim shows that Rema was lenient both by cooked and by cold, to consider this ChaNaN lach b’lach and be maikel b’hefsed mirubah2.

Pieces mixed in cold that can be removed

If two cold liquids that do not mix, such as oil and wine, are combined together, we do not say CHaNaN, since there is no transfer of ta’am and it can be separated. Likewise, if cold solids of issur are mixed into a cold liquid, since the solids can be removed, we would not say CHaNaN.

 A salad dressing factory produces a bacon flavored dressing that contains slightly less than 2% real bacon bits. The process is all cold. Although the bacon is not batel b’shishim, still in this case, we do not say ChaNaN, since everything is cold, and the bacon pieces can be separated and removed from the dressing. The equipment is cleaned with at least 300 gallons of plain hot water (no caustic) at about 140-145 F. Does this cleaning make the equipment non-kosher? Although it is estimated that approximately 12 gallons of dressing remain in the lines, less than ¼ gallon of this dressing is bacon bits. In this case, the wash water would be about 1200 times more than the bacon bits, so the bacon bits would be batel in the hot water and will not assur the tanks.

Dry blending of various powders

Mishnah Berurah (447:32 and 453:17) paskens that kemach b’kemach (mixtures of powders) is considered a complete mixture similar to lach b’lach. The Pri Migadim (M.Z. 447:19) says that the rules of CHaNaN lach b’lach would apply to mixtures of flour as well. Therefore, if chametz flour is mixed with Pesach flour and is not batel b’shishim, then after the fourth hour on erev Pesach, the entire mixture becomes neveila. Even if more Pesach flour would get mixed in, the chametz flour would no longer become batel. However, Pri Migadim is referring to two identical powders, which cannot be separated. However in practice, when we are dealing with dry blends of various powders, the powders will have different sizes and densities, and theoretically it would be possible to centrifuge apart the various powders. Since this mixture can be undone, we do not say CHaNaN. Even if one is not certain if the powders can be separated, we are lenient, since there are poskim who do not consider powders to be lach b’lach, and when there are additional sfeikos, as noted above, one may be maikel3.

Example: A company adds a stabilizer to their yogurt that contains a blend of various powders including gelatin. The gelatin is 14% of the blend (by weight). The stabilizer is added to the yogurt at 5%. Because we do not say CHaNaN on this mixture of powders, the issur will be less than shishim (.7%) in the yogurt, and even after converting from weight into volume, the gelatin will still be batel.  Therefore, there will be no need to kasher the kettles.


1. See Noda B’Yehuda Tinyana Y.D. 50 that perhaps one can be maikel not to say CHaNaN, if the mixture was liquid and later congealed.

2.  See also Shach 134:16 that we say ChaNaN even lach b’lach cold.

3  See Pleisi Y.D. 109:1