Following on from the recent baguette question (what if the bread kneaders hands were dirty?) French fries cooked in a wire basket in a vat of vegetable oil used only for that purpose.

In a diner with non kosher ingredients, are the main obstacles here: the knife that cut the spuds, and the plate they are served on? If they give me a paper plate... then just the knife? If they tell me it is a single-purpose knife.

  • 6
    That's potentially bishul akum. The bread case is different
    – Double AA
    Jul 26, 2020 at 1:29
  • 2
    There is also an issue of mar'is ayin that would apply even if you only ordered a bottle of soda. Jul 26, 2020 at 2:34
  • 3
    Hard to control the oil. Since it is expensive, it sometimes gets recycled, e.g., the oil for the fries might have been used to cook other (non-kosher) food before.
    – mbloch
    Jul 26, 2020 at 3:08
  • Thanks. מראית עין I sense as an issue, making me uncomfortable, as it is meant to. @mbloch your answer is more at the level I was hoping solutions exist, also relating to trusting what people say. בישול עכו״ם seems enormous. First of all it has to do with my relations with other Jews, and where they want to eat. Jul 26, 2020 at 10:15
  • 1
    Aside from the fact that the restaurant staff have no נאמנות, so you can not trust that they are telling you the truth (regarding the oil, or anything else).
    – Esther
    Aug 4, 2020 at 7:42

1 Answer 1


The cutting board/counter can also be an issue. If it was used to cut, prior to the cutting the potatoes, unkosher food which is sticky/filmy/greasy etc, that residue can get on to the potatoes. The oil it is fried in would need to be 60 times that unkosher taste. Even if it were, at some point the oil would have gotten enough unkosher taste in it that it no longer could be considered kosher itself See Rema 99:6 so unless the owner changed the oil and your fries were in the first batches that were fried when the oil was able to nullify the unkosher taste, the fries can be unkosher.

  • Aside from the extremely far-fetched nature of your case, this doesn't account for all the extra heter of potatoes each time in the oil
    – Double AA
    Jul 27, 2020 at 12:13
  • What do you mean by "this doesn't account for all the extra heter of potatoes each time in the oil "
    – Geltman
    Jul 27, 2020 at 12:43
  • the oil is batel in the potatoes too. Meaning the total heter is increasing with time more than the total issur is.
    – Double AA
    Jul 27, 2020 at 13:07
  • @DoubleAA wouldn't this still be a problem (for ashkenazim at least) because of ChaNaN 'shar issurim? Even if' we'll say that it' b'davar lach, IIRC the rama is still machmir unless it's hefsed merubah or the like (I think it's in YD 105:4 or thereabouts?)
    – Binyomin
    Jul 27, 2020 at 17:47
  • 1
    @Binyomin chanan wouldn't come into play until the first time it's not batel, no?
    – Double AA
    Jul 27, 2020 at 17:49

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