I have searched a number or sources for this, and have asked people involved in kashrus, and can't quite get a straight answer. This is a series of compound questions:

  1. If a meat pot is completely clean but a ben yomo, why don't we rely on batel beshishim? Wouldn't there be a miniscule amount of meat left in the pot?

  2. Depending on the answer to above, why then does it matter if its a ben yomo or not?

  3. This raises the general question, does the notion of batel beshishim apply at all when speaking of utensils and the status of the food cooked in them?

  4. I see the "DE" symbol on some foods. The only definition I can find is that its nat bar nat. But no mention is made of ben yomo or not. Does DE imply ben yomo or non ben yomo?


  • "Wouldn't there be a miniscule amount of meat left in the pot?" How could one possibly know how much meat flavor is left?
    – Double AA
    Sep 12 '17 at 0:27
  • "How could one possibly know how much meat flavor is left??" - my assumption for the sake of this question is that clean means completely spotlessly clean. Are you saying clean is a separate issue from flavor? If so, that get us closer to the answer.
    – Bob Barr
    Sep 12 '17 at 0:35
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    There's really no way to know how much meat is left quantitatively so you have to assume the worst case: the volume of the pot of meat is left (or the total volume of meat cooked in the pot ever, whichever is less). Then you can apply Batel beShishim as usual.
    – Double AA
    Sep 12 '17 at 0:36

The Shulchan Aruch addresses all of this. The point is that some taste particles may have wound up in the walls of the pot. As shishim is measured by volume, not mass, and volumes aren't necessarily additive (1 gallon water + 1 gallon alcohol = 1.96 gallons total), we can only play it safe if we assume there was a volume of milk/meat/non-kosher taste particles in the pot walls equivalent to the total volume of the metal of the pot. It is thus very rare to have 60 against such a volume.

(The one exception would be if I take a brand-new pot, pour in 1 cup of beef broth, and boil; then I pour it out and clean out the pot. Now I pour 62 cups of milk into the pot and boil. In this case, I know that there is no more than 1 cup total of meaty particles contained in the walls of this pot, so it is in fact batel. [Bonus points for discussion of other opinions on chan"an in this case.] But generally, pots have been used a lot, so we assume the volume of the walls to be entirely filled with flavor particles.)

This is why we have to resort to nat bar nat when cooking pareve soup in a dairy pot (for Sephardim anyway), as bitul beshishim is unlikely.

To answer your second question: In industrial applications we generally assume ben yomo; a company could easily do a dairy run and a non-dairy run in the same day. (If anything, they're very unlikely to let their machinery sit unused for a whole 24 hours!) So the "DE" potato soup is the industrial equivalent of if you boiled milk in a pot, washed it out, then an hour later boiled pareve potato soup -- the general guidance from kashrus agencies is you don't have to wait six hours, but don't eat it with meat!; this is exactly how the Ramah and Shach come out in this case.

(A true case of nat bar nat means the food is completely pareve; i.e. you can mix it with meat or milk.)

  • "...equivalent to the total volume of the metal of the pot."- Are you essentially saying surface area? Also, if the taste particles are so abundant, how is the parve food cooked in the dairy pot considered parve at all? Or is this perhaps is essence of nar bar nat, that its a way of creating this parve food despite it not being batel beshishim (or rov?)
    – Bob Barr
    Sep 12 '17 at 0:55
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    @BobBarr surface area multiplied by the thickness of the metal. (Volume; it's three-dimensional; go from square inches to cubic inches.) And you're correct; nat bar nat says even if it's not batel beshishim, the taste of those milky particles is so weak at this point that the Torah didn't prohibit them if mixed with meat -- no matter how abundant.
    – Shalom
    Sep 12 '17 at 1:02
  • Another aspect of this question I forgot to ask is about ovens (where the food does not touch the cooking vessel directly). Do these same concepts apply?
    – Bob Barr
    Sep 12 '17 at 3:48
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    @BobBarr please ask ovens as its own question.
    – Shalom
    Sep 12 '17 at 8:09

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