I have been reading a lot of questions concerning kosher foods, to get a better understanding of what it means for something to be kosher. To an atheist, this site is very helpful.

But as a chemistry student, I find some of the concepts related to kashrut quite surprising, particularly the ones relating to taste transferral.

This led me to wonder how - if - kashrut has been affected by Science?

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    By "science" do you mean the way the world around us works, or do you mean the opinions of scientists over the ages?
    – b a
    Commented Aug 8, 2012 at 4:20
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    @ba I refer to what is described in here. I am concerned about knowledge and scientific facts that have withstood falsification as of yet. There is no absolute, but there's such a thing as a rock solid pile of evidence/experimental data - that's what I'm talking about.
    – CHM
    Commented Aug 8, 2012 at 4:25
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    Still, can you give examples of the issues that you question?
    – YDK
    Commented Aug 8, 2012 at 5:05
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    can you elaborate on "I find some of the concepts related to kashrut quite surprising, particularly the ones relating to taste transferral." -- some examples, perhaps.
    – Menachem
    Commented Aug 8, 2012 at 5:56
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    Something to keep in mind: Judaism works at the level of the perception of a human. Not at the level of absolutes. If you keep this in mind some of the rules will make more sense. (For example taste: What matters is not what happened, but what a human can perceive i.e. taste.)
    – Ariel
    Commented Aug 8, 2012 at 11:03

1 Answer 1


Kashrut has not been affected by science - that is, halakhic rulings issued by recognized kashrut organizations regarding the kashrut of any food have not changed due to scientific discoveries. (Kashrut has been affected in the sense that it needs to react to new ingredients and cooking methods created by science. Individual rabbis have ruled in accordance with science.)

For example, there were kashrut concerns about parasites in fish. Modern biology demonstrated that Chazal's understanding of parasites is incorrect. However, most rabbis ruled that the halachot regarding the kashrut of these fish remain unaffected, and in practice, the kashrut organizations ruled that they remain kosher. (R' Elyashiv is the main dissenter; see article for details.)

For more information, please see:

  • I don't get it. Is it only "most rabbis" who support your opening sentence?
    – Double AA
    Commented Apr 25, 2014 at 4:31
  • Yes. Clarified.
    – Shmuel
    Commented Apr 25, 2014 at 4:52
  • I don't understand why certain major kashrut organizations define "kashrut".
    – Double AA
    Commented Apr 25, 2014 at 13:53
  • Do you eat food that isn't certified? De facto, these organizations define "kashrut" as is practiced by Jewry today. If someone isn't sure if a single particular item isn't kosher, they may ask their LOR, but for issues that affect everyone, such as scientific discoveries, these organizations are the only one with the knowledge and expertise to give a psak, and the LOR will recognize that.
    – Shmuel
    Commented Apr 25, 2014 at 19:41
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    Sometimes. Depends on the food. I see no reason why their decisions are binding. There are foods that are certified which I won't eat and foods which wouldn't be certified which I will eat. Just because there is a monopoly in the supply doesn't create a "minhag" which precludes other possibilities.
    – Double AA
    Commented Apr 25, 2014 at 21:53

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