How to deal with pesticides in lemon peel? / Prophylactic self-isolation series. Day 218th.

lemon fruit on a tree with green leaves around

Overture

Sometimes it is important to remove pesticides from lemon peels, because you may use it in baking, or refreshing drinks. And you would like to have your cake or a beverage with a minimized amount pesticides, right?

Last Friday we had a look on a lemon peel – its constituents, biologically active compounds and uses in food, cosmetology and other industrial fields. You may find my post about lemon peel benefits (scientifically proved) by following the link: What is about lemon peel?

Today we will try to deal with pesticides in it! What is known and what could be done to eliminate/reduce the amount of pesticides in lemon peel when using in home-made food and cosmetics.

Pesticides that could be used in lemons

In the scientific study by Lesueur et.al (2007) lemons were tested along with grape, onion and tomatoes to measure the amount of pesticides. In this study, 140 pesticides were used for analysis as they are conventional in farming.

Apolar, middle polar and polar pesticides were used.

Blog author’s notes:

  • Lemon, grape, onion and tomatoes are not the only plants which undergo a treatment with pesticides. For the particular scientific study by Lesueur et. al, 4 plants were selected because the goal was to study 4 different “matrices”:
    • lemon because of high acid content;
    • tomato (high water content),
    • grape (high sugars content) and
    • onion for high sulfur content.
  • There are more than 140 pesticides available on a market – here it is sated as 140 only because one scientific articles was analyzed by the blog’s author
  • The particular study was conducted in 2007, therefore lots of new pesticides are probably to appear within a decade, and some of them are probably no more in use.
  • The terms “apolar“, “middle polar” and “polar” will be explained below so that a common reader would get a general understanding of what we are talking about here. More so, because of this term understanding, one could later perceive the “magic chemistry” of the methods used to remove/partly remove the pesticides from lemon peels.

How to deal with pesticides if turning on the basic understanding of chemistry

Terms apolar, middle polar and polar

These terms are common for all chemistry language, not only for pesticides in lemon peel. So, what is it?

POLAR molecules: water, soda and vinegar

  • Sodium bicarbonate (baking soda), acetic acid (vinegar with water) and water molecules itself are POLAR
  • Polar molecule has “poles” – poles of positive and negative charges, in other words polar molecules have “+” and “-” charges that could react one with each other.
    • So, if we take two polar substances, like water and sodium bicarbonate (soda) – they will react. One could clearly see the reaction between water and soda – soda dissolves in water, right?
Water and sodium bicarbonate (baking soda) both have “poles”: “+” and “-” charges which can interact
  • When the substances react (interact) they exchange their elements. As in the example with soda and water, first water (H2O) had a plain taste, but when soda is dissolved in it – now water has a sour taste, right?

POLAR PESTICIDES in lemon peel

The same principle is valid for other polar substances, like polar pesticides. When polar pesticide reacts with water – it dissolves in water. One may not feel the specific “taste” of pesticide, but it is there and could be detected by using special laboratory equipment.

That is why just washing thoroughly the lemons under running water will partly remove pesticides on it – polar pesticides

Polar pesticides which have charged zones “+’ and “-” react with other polar substances like water. As a result, polar pesticides pass to water

The amount of washed off polar pesticides from lemon peel will increase if adding one more polar substance to water – soda or vinegar.

Now the capacity of the removal grows: more polar pesticide molecules will “jump” into water-soda or water-vinegar mixture because there are more charges “+” and “-” possible to interact

APOLAR PESTICIDES in lemon peel

Contrary, apolar molecules do not have poles, they do not have charges zones with “+” and “-“. That means theoretically that apolar pesticides in lemon peel will not interact with water (which is polar substance).

I wrote “theoretically” because nothing is 100% and one could understand what I mean from the following example:

Example of water in a plastic bottle

Bottle material – plastic -is nonpolar (or apolar) and does not dissolve in water which is polar, right? But have you noticed, if leaving plastic bottle in a car on a hot sunny day and later try water – it has a specific “plastic” taste. Have you noticed it? That is the chemical experiment, the chemical reaction. Now you may understand that those molecules of plastic, despite the fact that they are not soluble in water, go into water if favorable conditions like higher temperature are present. That is why everything is 99% and 1% could determine the whole thing. If you still use it (plastic bottles) – keep it away from sunlight and higher temperatures! No need to poison yourself slowly.

While apolar molecules do not have “poles” to interact with polar substances like water, they could interact with other apolar molecules. What kind of materials do you know which do not dissolve (interact) with water? That would be the apolar (or middle polar) substances!

Seems difficult to guess? No:) Apolar substances are, for example, vegetable oils, coconut oil. Apolar parts in coconut oil structure could therefore interact with apolar pesticides and remove them.

Apolar pesticides from lemon peel could be removed by apolar substances like coconut oil, or vegetable oil

MIDDLE POLAR PESTICIDES in lemon peel

Middle polar pesticides are something in the middle: they have and charged areas in their molecules, as well as non-charged areas. That means polar solvents like water will affect it partly – will dissolve only “polar” parts of the pesticide.

Now, how to apply the chemistry into practice?

Now when we know what is polar and apolar substances, one could understand how a simply methods work.

Home methods to wash-out pesticides from lemon peel

First of all, take a whole (not cut) lemons. The methods could be applied for other citrus fruits like oranges, lime or grapefruit too.

“WATER” METHODS to remove polar pesticides

removerproceduretime
waterwash the lemons thoroughly under running water1-2 min
waterwash the lemons under running water and then soak in a bowl with water10-15 min
water + soda1. put soda into a bowl
2. pour a small amount of hot boiling water on soda so that the bubbles of carbon dioxide would come out
3. add water (room temperature) and then soak lemons in it
10-15 min
water + vinegarwash the lemons under running water and then soak in a bowl with water (200-300 ml / 6-10 oz) and vinegar (1 Tbsp)10- 15 min

“OIL” METHOD to remove apolar pesticides

removerproceduretime
coconut oil or odorless vegetable oil (like sunflower oil)lubricate the lemon with oil and then wipe thoroughly with paper napkin1-2 min

COMBINED METHODS to remove both polar and apolar pesticides

removerproceduretime
water + coconut oil; water/vinegar + coconut oil, etccombination of one “water” method with “oil” method, but “water” method always before “oil” method10-15 min

Duration and temperature are important

One could think now, as longer soaking as better, but it is not. 10-15 minutes is enough, because keeping the lemons in water or water solution longer will facilitate other, beneficial components (like vitamin C) of lemons to dissolve in water too.

The temperature is important too. Wash the lemons in lukewarm water. Because hot water will facilitate beneficial aroma substances (essential oils) of lemon to evaporate, while too cold water will slow down the reaction between water and polar pesticide, so less will be removed.

Coconut oil to remove pesticides? What???

I guess you will not find this info anywhere else. I have not seen anyone in web to offer it, but it is obvious: to deal with apolar pesticides one may need an apolar remover! So, wipe your lemons with oil and clean it thoroughly afterwards with paper napkin.

Important moment here is, if one would think to deal both with apolar and polar pesticides in lemons – use “water” method first and “oil” method after. Because if otherwise, what ever well you will clean the oil after application – some of it, a thin film, would remain and that could interfere the dissolution of polar pesticides in polar water later!

GMO in lemons

Well, let keep this topic for another time, maybe next Friday?:) Stay tuned!

Where to use lemon peel?

I know some people (including me:)) love just to chew lemon peel. You may also use it in baking, and I use it in making my Original tablets and Lemony water – the recipe will come soon in Wednesday’s rubric Tasty Wednesday.

You may find more applications of lemon peel in my previous post What is about lemon peel?

References:

  1. Analysis of 140 pesticides from conventional farming foodstuff samples after extraction with the modified QuECheRS method. C. Lesueur et al. Food Control 19 (2008) 906–914

Images are created by using BioRender.com. Text © Dr. A. Palatronis / www.z-antenna.com

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