If I use a mortar and pestle for working with candlenuts (who are considered mildly toxic when raw), to make a paste that is later cooked, how thoroughly and how does that mortar (not dishwasher proof, using soap is also best avoided) need to be cleaned before you can safely use it for raw preparations like pesto?

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    A quick search doesn't show up a necessary cooking temperature. Do you have a reference giving such a temperature? What material are you thinking of? How much heat can it take? Rinsing with boiling water may be sufficient, for example.
    – Chris H
    Jan 30, 2017 at 15:01
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    Why not just use a mortar and pestle that will take soap? I would want to clean it even if the prior use was not mildly toxic.
    – paparazzo
    Jan 30, 2017 at 16:46
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    Non-porous mortars that are rough and large enough to deal with making spice pastes are quite the exception :) Jan 30, 2017 at 16:47
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    @rackandboneman: It's actually a challenge to find a decent sized mortar. For some reason, the manufacturers seem to produce for apothecaries, rather than cooks... Jan 30, 2017 at 16:50
  • And btw, with mortars with an untreated stone surface, the common method seems to be to just rinse with water and leave some residual oil where it is. Jan 31, 2017 at 14:17

1 Answer 1


Didn't even know they were toxic uncooked, and survived 40+ years of home cooking (both by me and my parents) without any ill effect, I would say 99% of the times ground uncooked.

That is, however, not an answer, so I will just explain my point of view, and why I won't bother with extraordinary cleansing after grinding candlenuts.

  • I can't find anything on the toxicity levels, other than "mildly", and never saw any warning on any bag of candlenuts. I did find it on some other "exotic" ingredients, most notably mustard oil.
  • Not a very strong argument, but: Usually, somewhere between 5 and 10 nuts are used, tops. For a mildly toxic ingredient, this seems quite a low number to make it dangerously toxic.
  • It seems unlikely to me that after grinding you end up with 99% of the stuff going in to the dish, and yet somehow, a significant, if not most of the amount of toxins remaining in the mortar.
  • Recipes sometimes do tell to toast the candlenuts first. None of the ones I know of say it is because of the toxicity. All of the ones I know of, tell to toast them lightly, a few minutes max. Given the size of a candlenut, it seems unlikely to me (but I'm not chemist) that toasting it for around 2-3 minutes will kill the toxins. Come to think of it: None of the books, recipes, or sources otherwise ever even mentioned their toxicity.
  • Lastly, and completely irrelevant, I may be the lucky one of course: I'm still here breathing.

All in all, I personally group it into the "Tomatoes and potatoes are toxic" category. Both nightshades, but you'll have to eat a ton of them in one sitting before you'll have to start worrying.

  • This is a satisfying answer for a home cooking situation (except the edge case of feeding someone else pesto from the same mortar), it wouldn't be in a pro context (which isn't mine currently), however in pro context one could play it safe by using two mortars :) Jan 31, 2017 at 14:15
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    @rackandboneman: True. Never have been a pro, never will be. I assume I'm writing for a non-pro audience. I always assume/hope professionals are already up to speed, especially when it comes to customer safety, and only visit and participate here to help people like me on the way :) Jan 31, 2017 at 16:08

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