I scrub waxed citrus fruit under hot water with a little washing up liquid added as I have been advised. Can I clean up unwaxed citrus fruit coated with imazalil in a similar way please? I use a lot of citrus zest in my baking so this question is important to have an answer.
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How much is "a lot". Most recipes use less than a single fruits worth of peel in a whole cake – TFD Nov 03 '15 at 19:39
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Imazalil is a suspected carcinogen, so is bacon – TFD Nov 03 '15 at 19:41
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The amount left on a fruit after being on the tree growing etc, in the rain, wind, and lots of sunshine is very small, and way under recommended limits, that why they are allowed to sell it to retail consumers – TFD Nov 03 '15 at 19:42
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Dipped fruit, is usually only late harvest, or long storage fruit, this is easily avoid by only buying in season. Again the amount is very small that is left, especially by the time you buy it. And any containment in pulp is usally regarded as cross-contamination, not organic ingestion – TFD Nov 03 '15 at 19:50
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6@TFD look up a classic lemon bar recipe, you'll be zesting 3 or 4 lemons for a standard batch of 8-12 bars. – Escoce Nov 03 '15 at 20:17
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2@Escoce that's a joke right? With that amount of fat and sugar, you shouldn't be worried about cancer from imazalil, your problem will be diabetes or heart disease – TFD Nov 03 '15 at 21:18
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3I was simply saying there are uses for that much zest in a recipe. I never mentioned anything about anything else. – Escoce Nov 03 '15 at 21:19
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I thought that all edible fruit and veg in the uk were stricter and nothing was allowed in that was carcinogenic – SoniaSpiers May 26 '18 at 14:22
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Could you get organic citrus with no imazalil on them ? – Max Jan 23 '19 at 18:08
5 Answers
No, you can't wash it off. Part of it is probably that washing methods are not fully effective, another part is that there is diffusion into the fruit, and the diffusion is strongest in the uppermost cell layers. In oranges, this is the peel.
From Kruve, A., Lamos, A., Kirillova, J., & Herodes, K. (2007, September). Pesticide residues in commercially available oranges and evaluation of potential washing methods. In Proceedings of the Estonian Academy of Sciences. Chemistry (Vol. 56, No. 3, pp. 134-141).
The same paper found 0.64 mg/kg imazalil content in orange peel and 0.04 mg/kg in orange pulp before washing. The regulatory allowed limit is 5 mg/kg. So if your fruit starts out with more pesticide than theirs - and it can legally be sold with 8 times more - the residue will be even higher.
If you want to follow safe food preparation practices, you have to use organic citrus fruit for zest. Non organic fruit can have pesticide residue from the growing period and still be labelled as "untreated" because it was not treated post-harvest.
If you are eating only the zest, you can happen to stay under the WHO acceptable daily dose, which is 0.05 mg/kg (human weight, not fruit weight). So if you're a 75 kg man1, you can eat a bit over half a kilogram of orange peel (if it doesn't exceed regulatory limits) and stay under the limit. But 1) you're also taking in the pesticide from the pulp, and while there's less in it, you're eating much more pulp than zest, 2) regulatory limits might be laxer where you live than in the EU, and 3) you're still poisoning yourself, even if it's not enough to become alarmed about it. Why consume one more carcinogen when you can avoid it?
1 it's less for women of childbearing age and children
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5Nothing is safe. You are more likely to get killed driving to the organic fruit store, or die from lung diseases from the fumes from your VW car, than get cancer from imazalil – TFD Nov 03 '15 at 19:54
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2@TFD and agliogia if you define "safe" as "zero risk", then of course nothing is safe, ever. This is why specialists are paid a lot of money to calculate an amount of risk which is seen as acceptable (a very difficult calculation) and this is labelled "safe" **Safety is a matter of expert opinion and regulation**, not a promise that nothing can happen. And people don't get cancer "from carcinogens", but the exposure to each of them increases their total risk. If you, personally, decide to expose yourself to a preventable risk, it's your right to do so. – rumtscho Nov 03 '15 at 20:12
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5@algiogia what!? `you can eat a bit over half a kilogram of orange peel` - do you have any plans to eat _over a pound of orange zest in a day?_ Let's have some [perspective](https://en.wikipedia.org/wiki/Banana_equivalent_dose) please. – Mike G Nov 03 '15 at 20:25
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2@mikeTheLiar but it's also in the pulp. I know I won't die eating oranges, I not that stupid. But if you add everything up the future doesn't look bright – algiogia Nov 04 '15 at 12:58
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Those two solid `0.00` values in the table are strange. Especially that thyabendazole was not considered washable off by the articles I saw previously. Also, it thermally decomposes somewhere above 200'C, AFAIK. Did the text have any explanation? – Sz. Jan 05 '19 at 16:54
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1@Sz. they just take it at face value. To quote from the paper: "As can be seen for thiabendazole all washing methods decrease the concentration. Washing with cold water is the least effective method of washing. Washing with soap and in ultrasonic bath decrease the concentration twice. Hot water and dishwashing soap are able to totally remove thiabendazole residues from the orange peel." – rumtscho Jan 24 '19 at 11:40
Imazalil is a systemic fungizide that surpresses mold and bacterial growth, for example on the skin of citrus fruits.
As it is a known carcinogen, the consumption of citrus peels treated with it is not advisable, as stated here (in German, sorry) for example by the German a.i.d. (Governement supported agency).
I could not (yet) find a reliable source giving good information on the solubility of imazalil and the effectiveness of washing, so I stick to the official warning of "do not consume".
Without contrary proof, a variation of the basic food safety rule applies:
When in doubt, throw it out - that is, do not use the zest of treated citrus fruits.

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Here in Germany, practically all Citrus fruit treated with any artificial coating (usually any combination of Thiabendazol, Orthophenylphenol, Imazalil) comes with a clear statement "Schale nicht zum Verzehr geeignet" - "Peel unsuitable for consumption". One should assume there is a reason behind that very unconditional statement.
Most supermarkets here will carry both treated and organic (I asked a clerk at an organic store about it, they definitely are not allowed to do wax or treat them in any way) varieties probably for exactly that reason; the interesting thing is that neither of them are immune to getting moldy, nor do any of them mold quickly when stored under normal pantry conditions. Also, citrus fruit that come without an organic label but with an explicit label of "Schale ist verzehrbar" - "Peel is edible","Unbehandelt - Schale nach der Ernte" - "Untreated (Peel, post-harvest)" are becoming common. Not 100% sure if there are waxed products around that state their peel is edible.

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1Many waxes are edible, and organic fruit is allowed to be waxed with beeswax but not petroleum derived products. So, it is possible that a waxed product states that its peel is edible - but then, the peel shouldn't be toxic. I'm not entirely sure about the regulations about the "peel is edible" label, what kind of pre-harvest treatment it allows, and what are the toxin limits for it. – rumtscho Nov 03 '15 at 20:15
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So you are implying it might be more store/sourcing policy than law? – rackandboneman Dec 09 '15 at 13:01
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There is a law, I'm pretty certain of that. But I can't really tell how much of what you describe is prescribed by law and how much of it happens to be how a single store does it. Separately, even for things which are covered in the law, the matter isn't as straightforward as it seems on first glance. If the law says "only fruit which has not been waxed after harvest can be labelled as 'untreated'", it is entirely possible that all organic farms have switched to waxing before harvest. – rumtscho Dec 09 '15 at 14:07
Imazalil has a limited shelf life (after application) I guess one should keep the fruit (citrus) in the fridge for a while (maybe a week? considering that it has been already stored for a week before you got to buy it from the store...) please read "Degradation of imazalil, orthophenylphenol and pyrimethanil in Clementine mandarins under conventional postharvest industrial conditions at 4 °C" Washing will not help much but like any fruit/product to be consumed should be thoroughly cleaned; I use warm soapy water & baking soda for mine in hope I remove most of the wax as well as possible germs.
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3What does it degrade into? Expired poison doesn't mean harmless :) – rackandboneman Feb 17 '17 at 09:56
How long do fungicides in wax on oranges take to degrade? That may solve a problem. Or just wash wax off hands after peeling. Our bodies are very good at getting rid of bad things.
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1This is already mentioned in [Mark's answer](https://cooking.stackexchange.com/a/78481/34961), with a source instead of a question. The question is also not about wax on the hands. – Jan 30 '19 at 14:01