dimanche 8 mai 2022

The translation in English of a text that I published first in French, about the rigor in the use of words of chemistry

Rigourous terminology for concepts of chemistry: a base for rational choices.

Hervé This 1

1 INRAE, UMR 0782 SayFood, France.
 Correspondance :
Intae-AgroParisTech International Centre for Molecular and Physical Gastronomy

Translated from  This H. 2021. La rigueur terminologique pour les  concepts de la chimie : une base pour des choix de société rationnels, Notes Académiques de l'Académie d'agriculture de France / Academic Notes from the French Academy of Agriculture, 2021, 1, 1-15.

Food-related decisions that engage communities are often based on chemical concepts. Therefore, the utmost terminological rigour is required. This article considers frequent examples of confusion, and concludes with a call for the introduction of chemistry lessons as early as primary school.

chemistry, human food, public debate, controversies, terminological rigor, molecule, compound, fatty acid, triglyceride, minerals, natural product, chemical denomination


Public debates about food often involve chemical objects: nitrates, nitrites (Pouliquen, 2020), fatty acids (INSERM, 2020), glyphosate (Foodwatch, 2020), acrylamide (Cérou, 2020), iron (Santé Magazine, 2020), curcumin (Lacamp, 2020), DNA (Bru, 2020), mineral salts (Mary, 2020), pesticides (Foodwatch, 2020), micro-plastics (Anses, 2020a), nano-particles (Anses, 2020b)... Unfortunately, some of those who intervene in these debates are ignorant of the exact nature of these compounds and products, or have negative perceptions of them, as the consultation of the references given above shows over and over again! In particular, the belief in a "good nature" - which forgets for example natural poisons such as hemlock or datura - is not new (Mill, 1874), but it continues to rage, while unfounded fears are heard (Kressmann, 2018).
The bad knowledge of the objects of chemistry is deleterious, in the public debates where these objects intervene, because it can lead to irrational positions and choices of the public and the elected officials, then to laws which risk to govern the collective life in an unacceptable way for whoever seeks more rationality and a better use of the public money (Vaulpré et Jaffré, 2020). Already Nicolas de Condorcet wrote, at a time when science was considered as a "natural philosophy": "Any society which is not enlightened by philosophers is deceived by charlatans". (Condorcet, 1791).
It is true that chemistry courses have been introduced in secondary school courses, but they are limited, and recent surveys show the weakness of France, from this point of view (Cabioch, 2020), compared to other countries in the world. Beyond questions of national industrial competitiveness, training in chemistry is essential for citizens to be able to make up their minds in the highly technical world in which they live today. As young people become adults, and eventually elected officials, Parliament has deemed it essential to strengthen the scientific and technological knowledge of elected officials through the Parliamentary Office for the Evaluation of Scientific and Technological Choices, created in the early 1980s (OPECST, 2020): scientific information and training (especially in chemistry) help to avoid erroneous ideas, either resulting from personal preconceptions or propagated by pressure groups... And the issue of insufficient knowledge of science, especially chemistry, is serious enough that it is frequently considered by states and international organizations, including UNESCO, which has been concerned with the popularization of natural sciences in the public service media (Naji, 2006).
In this article, we analyze a series of frequent confusions, with a view to discussing further the reasons why rigorous terminology is needed, especially for the objects of chemistry. We address readers who are trained in the natural sciences, but not all of them chemists, and we also examine presentations to citizens who are not always well educated in science, seeking to show why those who are in a position to abuse language might usefully avoid it in public debate.
We wish to establish that rigor is never excessive when discussing questions that involve chemical objects, at the risk of confusions that would make the bed of ideologues or dishonest people, or that would lead to the unreasoned fears that we have mentioned.

An anthology, before taking a step back

1. A first common error, in relation to chemistry, is the abuse of language that consists in speaking of "molecules" to refer to "chemical species", in particular  "compounds" (Myers, 2012). Chemistry hesitated for a long time, before considering -at last- that a molecule is an assembly of atoms, whereas a compound is a category of molecules that are all identical, a particular kind of "chemical species" for which there are atoms of more than one chemical element. To say that water is a molecule, for example, must be avoided, because it is false, in the modern sense of the word "molecule". For the public, water is a liquid, and for chemistry, water is a material, a  "substance" which can be in the vapor phase, or liquid, or solid, for example, depending on temperature and pressure conditions (Lide, 2005); generally, for the samples considered on Earth, this material is made of very many identical molecules: tens of thousands of billions of identical molecules per gram of water (IUPAC, 2004).
A detail that is useless for citizens trained in the natural sciences, but essential for all those who do not have sufficient training and who participate in public debates: each of the water molecules is made of one oxygen atom and two hydrogen atoms, which is conventionally noted H2O (Lower, 2020). Water is a "compound" (since its molecules are made of atoms of two different chemical elements: oxygen and hydrogen).
Finally, above we have made the assumption of an absolute purity of the samples, but we will see later (example 5) that it is interesting to distinguish this pure water (rare on the Earth), made only of water molecules, from the water we drink, which inevitably contains a number of "impurities", i.e. molecules which are not water molecules, or various ions (sodium, magnesium, chloride, nitrate, etc.).
What is said about water obviously applies to other compounds.
In any case, the abuse (or impropriety, depending on the case) of language which consists in speaking of "molecule" to evoke a chemical species has serious consequences: the author of this text can testify to having met a science journalist from a public service television channel who thought (and explained to his audience!) that there were 450 odorant molecules in wines, and this person was thinking of 450 particular objects, of 450 molecules of chemists, and not of 450 odorant compounds (chemical species). Because yes, wine contains a few hundreds of different odorant compounds (depending on the wine), but each of these compounds is present, in a bottle of wine, at a rate of hundreds of thousands of billions of molecules (Pons et al., 2017).
The practice of popularization conferences, as well as the questioning of passers-by in the street, show that this case was very far from being isolated: when the notion of molecules is declared to be known, the idea to which it corresponds is very often erroneous, without even going so far as to hope that the citizens know that the molecules of a liquid are all in movement.
Let us add that the confusions between "compounds" and "molecules"(or  "chemical species"), when they are not abuses of language, can result as much from insufficient knowledge of chemistry, notably of its vocabulary, as from the difficulty of thinking about categories, already discussed by Aristotle, then many others (Van Aubel, 1963), before being, for example, one of the pitfalls of teaching, notably that of "modern mathematics" (Thom, 1970).
This is one reason why the introduction of the modern notion of molecules was such a remarkable achievement of chemistry, due in particular to Amedeo Avogadro (1776-1856), that it remained the object of violent scientific controversy until the first half of the twentieth century: French chemists, notably around Marcellin Berthelot, refused the modern (yet correct) idea of molecule, and their political influence, notably in terms of education and university training, caused French chemistry to lag half a century behind (Jacques, 1987).
In short, there are many reasons to be vigilant about this word "molecule", especially when one is addressing interlocutors or a public who are not aware of the possibilities of confusion.

2. More specifically, abuses of language that I believe to be harmful, in food science, technology, and engineering, are to speak of "fatty acids in a triglyceride" or "amino acids in a protein": it is more accurate (and internationally decided) to use the terminologies "fatty acid residues" and "amino acid residues", respectively, for the parts rightly designated as such, in triglycerides or in proteins (IUPAC, 2019).
Why? Because free fatty acids, for example (we are sometimes obliged to add the adjective "free" to make ourselves clear), are quite different compounds from triglycerides. And, often, it is useful to add that there are almost no (free) fatty acids in oils or in other food fats: it was, this time, a contribution of the French chemist Michel-Eugène Chevreul (Angers, 1786 - Paris, 1889) to establish that food fats are mostly composed of "triglycerides", and not fatty acids, recognizing by measurements of great precision (at that time) that the esterification reaction by which we can eventually synthesize a triglyceride does not correspond to a juxtaposition, but a real reaction, which changes the nature of the reactants (Chevreul, 1823). In the case of proteins, it was not until Theodor Svedberg's advances in the 1920s that the difference between a polymer (which proteins are) and a colloidal assembly (of amino acids, in this case) was finally understood (Florkin and Stotz, 1972).
The experience of university teaching shows how widespread is the confusion between fatty acids and triglycerides, or amino acids and proteins; it remains often until the master's degree, and, similarly, the analysis of public discussions shows how confused ideas are often on this subject.
In order to explain things to a public that constantly hears about "the fatty acids of table oils", even in food hygiene documents (PNNS, 2020; Olivier et al., 2014), we can usefully begin by pointing out that oil (like most food fats) is mainly made up of a large number of molecules similar to octopuses with three flexible arms: these molecules are "triglycerides". Note that we could also say "triacylglycerols", but this would unnecessarily increase the complexity (Figures 1 and 2).
Oils, for example, contain other compounds than triglycerides, but they are very much in the minority. For example, in the middle of the triglyceride molecules, oils also contain fatty acid molecules (free, therefore), squalene molecules, terpene acid molecules, sterol molecules, etc., but the total of all these, constituting the oil, is only one percent by mass.
Let's concentrate on these triglycerides which are in the majority. Oil and other fats contain a large number of different triglycerides (several billion for milk fat), the names of which are set by the international rules of the International Union of Pure and Applied Chemistry (IUPAC, 2019): the general rules of chemical naming lead to the recognition, in the center of triglyceride molecules, of a unit of three linked carbon atoms, each one linked to an oxygen atom, which is also the case in the molecules of the compound named glycerol (Figure 3). However, there is no glycerol (the compound) in the molecules of triglycerides; there is only a group of atoms reminiscent of glycerol, by the way, to within three hydrogen atoms (which is no small thing, in chemistry), and so one must speak, for this part identified by thought of "glycerol residue" (IUPAC, 2019).
Starting from this center, which is the  "glycerol residue", after the oxygen atoms that have been mentioned for this residue, the triglyceride molecules carry long chains of atoms that differ little from those of molecules of compounds that would be fatty acids: fatty acid molecules are, in fact, chains of carbon atoms bonded exclusively to hydrogen atoms, with, at one end, a "carboxylic acid" group, the terminal carbon atom being bonded to an oxygen atom by a double bond, and to a hydroxyl group, made of an oxygen atom itself bonded to a hydrogen atom (Figure 4). In triglycerides, this structure is not present as such, but only discernible to a few atoms. One can only recognize, in triglyceride molecules, a glycerol residue and three "fatty acid residues".
Why would some people (chemists or not) hesitate to say the right things? Why would they refuse to be terminologically rigorous? Because triglycerides could be assembled from fatty acids, and degraded to fatty acids? In reality, triglycerides can be constituted and modified in many different ways, and not necessarily by assembling one glycerol molecule and three fatty acid molecules. It depends on the reaction conditions: reagents present, pH, presence of free radicals, catalysts, etc.
Above all, to speak improperly of fatty acids (instead of "fatty acid residues") in fats is to expose oneself to the risk that the public (and even students of food science, technology and engineering) will think that oil is made of fatty acids! The risk even concerns people trained in science: the author of this text testifies that he knows an excellent physicist, a distinguished research director in his discipline, who believed this... because the confusing ambient language made him think so.
A nutritionist colleague who spoke of "triglyceride fatty acids" was questioned in the preparation of this article, and his reasons included (1) habit and (2) the fact that the public might fear "residues"... The first reason is not sufficient, as the history of chemistry has shown, which has progressed with the clarification of terminology, but the second is debatable: is there not a risk of paternalism in believing that the public is incapable of thinking well (This and Panel, 2010), knowing moreover how many charlatans, dishonest people, and ideologues sneak into the slightest intellectual breach to propagate their pernicious ideas?
And then, if the word -accepted inter-nationally- of "residue" seems difficult to use, why not use "fragment", or "group", for example... knowing that, in French, a residue is a part that remains after a main part has been removed, for example by evaporation: the connotation is not necessarily negative.

3. A third example, concerning "mineral salts", is intended to show the extent to which abuses of language can insidiously induce false ideas, even in scientific circles. We will begin by observing that, very often, the expression "mineral salts" should be replaced by "mineral ions", or "the mineral content of... ".
Let's start by observing that we often hear and read that water contains "mineral salts", or worse, that "calcium" and other mineral ions would be mineral salts (Passport to Health, 2020; Greenfield and Southgate, 2007)... This is incorrect for several reasons. First, calcium is an "element" and is only present in foods as divalent calcium ions. Secondly, a mineral ion, such as the calcium ion, is not a mineral salt, but only a mineral ion, which could be a constituent of a mineral salt if it were in a crystalline structure, with ions of opposite charge (at least in balance). Finally, "mineral salts" are (under ambient conditions) crystallized solids, such as sodium chloride (of which our table salt is mostly composed).
If we place crystals of a salt (for example, sodium chloride) in water, the constituent ions (chloride and sodium) can disperse, surrounding themselves with water molecules, and a solution of this salt can be formed (within the limits of solubility). In this particular case of the dissolution of a single salt, the water does contain a mineral salt, in solution, as long as it has been put in.
However, this is no longer true for ordinary drinking water, which contains various mineral ions: sodium, potassium, magnesium, chlorides, nitrates, sulphates, phosphates... These waters do indeed contain mineral ions, and they therefore have a mineral content, but do they contain mineral salts?
It is with regard to the last question that the difficulty arises, as can be seen from the simple case of an aqueous solution in which two mineral salts, such as sodium chloride and potassium nitrate, for example, have been initially dissolved. This solution would be the same if potassium chloride and sodium nitrate had been dissolved instead, so that, without knowing how the solution was constituted, it is impossible to say which mineral salts it may contain.
More generally, when faced with a solution that has a mineral content, it is impossible to say what "mineral salts" it contains. What is true for an aqueous solution is true for food ingredients and foods, including plant or animal tissues, or culinary preparations made from them: all have a mineral content, all contain mineral ions, but it would be very difficult to identify the mineral salts they contain. Conclusion: food does not contain mineral salts!
4. The fourth example concerns a more subtle - but chemically essential - characteristic of food compounds: their "chirality". To discuss this, let us first recall a tragic episode in pharmacy.
In the 1950s and 1960s, thalidomide was prescribed to pregnant women to relieve morning sickness, but it was overlooked that the compound appears in two mirror-image forms, like a left hand and a right hand. Just as a left hand is not a right hand, a left molecular form has different chemical and biological properties than a right molecular form (Figure 5). Metaphorically, one does not fit the left hand into the right glove or vice versa, and what applies to hands and gloves applies to active ingredients and biological receptors (Jacques, 1981). In the case of thalidomide, its "right" chiral form relieves nausea, while its "left" form causes malformations in the fetus: 10,000 to 20,000 children were born in this way, terribly affected, because of the confusion!
With foods, whether nutrients or bioactive compounds, the same question arises, and so chirality (the left-hand/right-hand difference) has become the daily tool of flavourists and perfumers: for example, (+)-(S)-carvone and (-)-(R)-carvone do not smell the same, like spearmint or dill. Or, (E)-anethole (trans form) is very low in toxicity, while the cis form, synthetic or natural trace, is much more toxic. Both enantiomers of linalool are natural, but while the (+)-(S)-linalol in coriander is very low in toxicity, the (-)-(R)-linalol in basil and lavender is higher. To simply talk about "anethole", for example, is simplistic... not to mention the disasters it can cause!

5. From compounds, let us now turn to "products" used in food. For the former, we have mentioned the common difficulty of thinking in terms of categories, but we have not gone into the details of the philosophical difficulties, namely that "the horse" is a very heterogeneous category: ponies, percherons, bay horses, grey horses, piebalds... This question is encountered with food ingredients.
Here again, public debates are hasty: "the" flour, for example... Which flour? What kind? With what composition? Bakers and confectioners are well aware of the variability of this product, even when only wheat flour is considered, to the point that it complicates recipes considerably (Inbp, 1990): the amount of water that must be added to a dough depends on the year, the origin, the grinding, the temperature of use... This same type of observation is valid for most of the food ingredients: "gelatine", "lecithin", etc.
Here for "products" as about the chirality of compounds, the question is terminological, and the consequences are sometimes serious. We recall the terrible episode of 2019, when a pharmaceutical company changed the formulation of its drug against hypothyroidism: the change in formulation, which was not accompanied by a change in name, had terrible consequences for many patients who used "the" product (Ansm, 2017). For food, this issue must be analyzed in the light of the 1905 law on the food trade, which must be "fair" (horse is not beef): this fairness requires fair designations (French Academy of Agriculture, 2011) and, in particular, fair chemical designations. Hence the importance of IUPAC, mentioned earlier.
This observation finds its full importance in relation to food additives: there is certainly a need for better designation (Anses, 2016). For example, the additive designated by the European code E140 corresponds to what is sometimes called chlorophyllin, or sometimes chlorophyll (Efsa, 2015), but, ultimately, what is it?
Let us first observe that "the" chlorophyll is an outdated terminology, introduced in 1818 by the French pharmacists Joseph Bienaimé Caventou (1795-1877) and Pierre Joseph Pelletier (1788-1842) to designate what cooks called "spinach green" (This, 2019); today, we know "chlorophylls", with different light absorptions: a, a', b, b', c, d, e, etc. On the other hand, the preparations made from chlorophylls and metals, such as zinc or copper, are no longer chlorophylls (in the center of which there is naturally a divalent magnesium ion), but chlorophyllines, zinciques or cuivriques, for example.
Similarly, we find the question about "lecithin" (IUPAC, 1979), a term that still suffers from the hesitations of chemistry, when it was young and more imperfect than today. Here, the story begins in 1845, when the French chemist and pharmacist Theodore Gobley isolated "lecithin" from egg yolk (lekithos means "egg yolk" in Greek); in 1874, he established the complete chemical formula of "lecithin phosphatidylcholine" (Gobley, 1874). Between 1850 and 1874, he had demonstrated the presence of "lecithin" in a variety of biological materials, including venous blood, human lungs, bile, human brain tissue, fish eggs, and chicken and sheep brains.
How to admit that, today, "lecithin" designates preparations (mixtures of compounds, therefore), with different properties according to the producers? The differences in functionality of the various preparations expose users to problems. Of course, one could say that no material is constant: "gelatin" can have a lot or little gelling power, depending on the batch; the same goes for "pectin", of which there are various varieties... even for "egg white powder", which is sold under this name, whether it is cooked and dehydrated egg white or fresh dehydrated egg white, with considerable differences in functionality for the two products (one does not coagulate, and the other can coagulate). Wouldn't it be in our interest, in the interest of fair trade, to better designate the food ingredients that are traded?

6. The same question is found with the products called - unfortunately - "flavors" (Dgccrf, 2006), and for which I propose to analyze that the terminological vagueness has undermined social cohesion. Indeed, we all know that, on the one hand, these products are widely used by the food industry, and, on the other hand, they are widely criticized - for a long time - by a part of the population (60 Millions de consommateurs, 2016). Could it not be interpreted that the public fears deception? In fact, the food industry and regulatory authorities have warped the word "aroma", which in French means the smell of an aromatic plant, an aromatic (TLFi, 2020). It would have been wiser not to use this term to designate flavoring compositions or extracts!
Because that is what it is all about: these compositions or extracts (which are never "natural", stricto sensu, since they are produced by craftsmen or industrialists) are either "compositions", obtained by mixing odorant compounds, by a technical and artistic work which is similar to that of the perfumer ; or "extracts", obtained by methods that resemble the production of table sugar from beet, or the production of eaux-de-vie from wines, with, in this case, processes that range from cold pressing to distillation, possibly with solvents (Sniaa, 2020). Since the public is right to think that compositions or extracts are not "flavors", in the sense of the common language, but rather flavoring agents, wouldn't the food industry, if it wants to show its loyalty, and the regulatory authorities, if they aim for more social cohesion, have an interest in taking the measure of the error initially made and changing the terminology?
Let us add two points:  (1) the English language distinguishes flavour from flavourings; (2) some of these flavourings are so remarkable, from an olfactory point of view, that there is hardly any reason not to make them available to the public, so that they can use them in their daily cooking... provided that they have a correct perception of them.

7. In the previous paragraph, we sketched out a discussion of the term "natural", but we did not insist enough to point out that the regulations also contradict the dictionary when they accept this adjective for products, flavourings (Sniaa, 2020) or others. Insofar as naturalness excludes the intervention of a human being (TLFi, 2020b), this use of the term "natural" is unwarranted, even dishonest: the "products" have indeed been produced, by human beings, so that they are strictly speaking "artificial".
If one were too lax, one would go as far as to speak of "natural food", and this is quite impossible since our food is cooked. Even "raw vegetables" are subject to culinary preparation, with trimming, washing, cutting, addition of a sauce, etc. (Bocuse, 1976). (Bocuse, 1976). So no: there is nothing natural in our food, and the regulations should absolutely refuse the demagogic temptation to accept this term of naturalness about food products, because there is the source of conflicts about it.

8. Let's end this anthology with nitrates and nitrites, of which it will be observed that very few of those who speak of them have ever seen them (this is true for most of the compounds or products mentioned in this text). However, it is not difficult to go and scrape some walls to recover saltpetre (Guyon, 2006): it is a nitrate, which was once added to saltings (Anonymous, 1826) and which prevented botulism (Pascal, 2020)!
While nitrates and nitrites are denounced by some (National Assembly, 2020; Ligue contre le cancer, 2019), the food industry, which is threatened in its practices, has learned to cook hams in vegetable broths, where naturally present nitrates (truly naturally, this time) are transformed into nitrites by fermentation (Ifip, 2020). Thus, hams (for example) obtained in this way contain nitrates and nitrites like pieces to which nitrite salt, commonly used by pork butchers, has been added.
In other words, the ban on nitrates and nitrites in charcuterie leads to propose the banning of ham cooked with vegetables, which would be quite an achievement, especially since the micro-organisms that transform nitrates into nitrites are naturally present in the environment!

Excessive rigor?

Let's stop here, because we could fill volumes, and concentrate on the question initially asked: is it excessive, unnecessary rigor to be concerned with exact terminology when we talk about chemical species in public debates or in teaching? Is it a waste of time to ask for a precise terminology? Is it really necessary to avoid abuses of language and imprecision? And is it right to annoy your interlocutors by repeating in a nagging, even intrusive way that proteins are not "made of amino acids", but of "amino acid residues", for example? Should we accept to appear fastidious by recommending to our interlocutors to speak about D-glucose rather than glucose (we will not forget thalidomide)? Should we accept talking about "iron", when we know that the bioavailability of ionic iron (and not just any iron ion) is very different from that of heme iron in the blood (in the heme group of certain proteins), to the point that doctors who prescribe "iron" to combat deficiencies have to add the prescription of ascorbic acid, to increase this absorption (Cismef, 2020).
Let us first answer the question posed with an authoritative argument, by quoting Antoine-Laurent de Lavoisier: "It is while I was occupied with this work that I felt more clearly than I had done until then, the evidence of the principles that were laid down by the Abbé de Condillac in his logic, and in some of his other works. He establishes that we can only think with the help of words; that languages are true analytical methods; that the simplest, most exact algebra, best adapted to its object of all the ways of expressing itself, is at the same time a language and an analytical method; finally that the art of reasoning is reduced to a well-made language.  [...] The impossibility of isolating nomenclature from science, and science from nomenclature, is due to the fact that all physical science is necessarily founded on three things: the series of facts that constitute science, the ideas that recall them, and the words that express them [...] As it is words that preserve ideas, and transmit them, it follows that one cannot perfect languages without perfecting science, nor science without language" (Lavoisier, 1789).
As we can see, the idea of the brilliant creator of modern chemistry was clear... and who among us would dare to contradict him, on a point of thought? Who among us has done so much for science that he could feel superior to Lavoisier? Come on, a little modesty.
Then let's ask our interlocutors the question: why should we be embarrassed to use the right terms? After all, a botanist does not confuse a carrot with a turnip, and a forester does not confuse a fir with a spruce, and those who are neither botanist nor forester conform to the uses defined by these professionals, since it is up to them to initially make the difference. No disadvantage, finally, except to have to work to eradicate our own inaccuracies... but many advantages to precision in chemistry: whether it is a question of substance or form, the objective is to avoid empty speeches, to invite to go and see more closely, and to avoid that ideologists seize confusions to arrive at their masked and, sometimes, nauseating ends.
Yes, the rigor of terminology for chemical terms, as well as the coherence of units of measurement (Lavoisier also participated in their harmonization and in the creation of the Metric System), are the foundation on which sound collective decisions can be taken. It is therefore a condition of democracy.
In addition, the examination of words avoids unnecessary fears. For example, a few years ago, a consumer magazine headlined that some products contained "traces of potentially carcinogenic pesticide residues". The word "potentially" should already put us on the track of healthy doubt, because potentially carcinogenic does not mean carcinogenic. And exposure to the product is essential, because without exposure to a hazard, there is no risk (Pascal, 2020). The word "pesticide"? There are synthesized pesticides, on the one hand, but there are also compounds with which plants naturally protect themselves (Ames et al., 1990). We will not discuss here the relative merits and dangers of the two categories, especially since it would be better to consider the various "pesticides", natural or artificial, one by one, but let us insist: an apple, a carrot, a potato, protect themselves against aggressors by natural compounds... which are sometimes synthesized to use them as pesticides.
Residues of these pesticides? Let us suppose that a pesticide is carcinogenic, and that it is degraded: nothing proves that its "residues" (we would more correctly speak of degradation products) are also carcinogenic, and, even better, why couldn't residues of synthetic pesticides be beneficial? Basically, we are back to the question of triglycerides... but the word "residue" is used in a different sense... very vague!
Finally, the consumer magazine did not mention pesticides or pesticide residues... but traces of pesticide residues! Knowing that our chemical analysis equipment detects compounds at amounts as low as 10-15 mol/L (Kawai et al., 2020), we should first ask the question "how much? ", and to relate the amounts to toxicological values (tolerable daily intake, for example).
Finally, let us make a useful observation: often the mistakes that students of food science and technology make are the result of a misuse of terms, an imprecise use of words that they use without sufficient understanding. The corollary of this is that wishes for good terminology use must be accompanied by efforts at instruction: chemistry must be introduced as early as elementary school. After all, is it so difficult to think that water, for example, is made of many small moving objects (water molecules)? And then, to speak about what one does not know, to use words of which one is unaware of the meaning, to show one's ignorance by silly sentences... Still, we have our dignity, don't we?


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Edité par
Nicole Moreau, Membre de la Société chimique de France et ancien Président de l'IUPAC. Président du Comité scientifique du Programme International pour les Sciences fondamentales (PISF) de l'UNESCO.

Nicole Moreau, Membre de la Société chimique de France et ancien Président de l'IUPAC. Président du Comité scientifique du Programme International pour les Sciences fondamentales (PISF) de l'UNESCO.

Jean-Pierre Foulon, ancien professeur de chimie en Spéciales au Lycée Henri IV à Paris. Membre du Comité de rédaction de l'Actualité Chimique (SCF).

Cet article a été publié dans la rubrique « Opinions » des Notes Académiques de l'Académie d'agriculture de France.

17 novembre 2019

3 janvier 2021

13 janvier 2021

This H. 2021. La rigueur terminologique pour les concepts de la chimie : une base pour des choix de société rationnels, Notes Académiques de l'Académie d'agriculture de France / Academic Notes from the French Academy of Agriculture, 2021, 1, 1-15.

Hervé This est physico-chimiste dans l'UMR 0782 SayFood INRAE - AgroParisTech, professeur consultant à AgroParisTech, membre de l'Académie d'agriculture de France, membre correspondant de l'Académie royale des sciences, arts et lettres de Belgique et de l'Académie de Stanislas, membre de l'Académie d'Alsace, sciences, lettres et arts.

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