Q&A from the Bais HaVaad Halacha Hotline

An Acquired Taste

May 14, 2026

Q I cut a raw onion with a meat knife and then chopped it in a pareve food processor. Is the processor now fleishig?

A Three basic conditions are generally required for blios (absorbed tastes) to transfer from one item to another and impact its status:

1. Typically, heat is required.
2. Only tastes absorbed within the past 24 hours (ben yomo) are significant; older blios are pagum (stale).
3. It isn’t na”t bar na”t: A permitted taste weakens after being transferred twice, so that is usually treated leniently. For example (Chulin 111b): If hot meat was put on a plate and then removed, and hot fish was put on the plate within 24 hours, the fish may be eaten with dairy, because the blios got to the fish via two transfers: Meat taste migrated first from the meat to the plate and then from the plate to the fish.

Davar charif (a sharp food) is an important exception: Transfer can occur without heat, stale taste can be reactivated, and taste does not weaken if it is na”t bar na”t (Shulchan Aruch Y.D. 96:1).

As onions are a davar charif, your food processor did become fleishig—but only the blade, not the container. Although davar charif enables transfer even without heat, it still requires duchka desakina (the pressure of the blade). The container just contacted the onion, so it remains pareve, but the blade applied pressure to the onion, so the onion absorbed its meat taste and became fleishig.

This ruling is explicit in the Magein Avraham (451:31), cited b y the Mishnah Brurah (ibid. 90), who warns against grinding ginger (a davar charif) that was cut with a fleishig knife in a pareve mortar, as the mortar would become fleishig and unfit for pareve use.

The Even Ha’ozer (Y.D. 96:3), followed by the Chavas Da’as (ibid. 6), disagrees with the Magein Avraham. While they agree that the ginger (or onion) should not be used with dairy, they maintain that when the davar charif transfers taste into the next utensil (the food processor blade), that is already considered na”t bar na”t, so the utensil might remain pareve.

Lechat’chilah, one should be stringent and consider the blade fleishig and in need of kashering, as per the Mishnah Brurah. Bedi’eved, if kashering (in boiling water) is difficult, one may rely on the Even Ha’ozer, as many poskim side with him (see list in Piskei Teshuvos 451 fn. 209).