Chemistry for Breakfast by Mai Thi Nguyen-Kim

Author:Mai Thi Nguyen-Kim [Nguyen-Kim, Mai Thi]
Language: eng
Format: azw3, epub
Publisher: Greystone Books
Published: 2021-04-12T16:00:00+00:00

Everybody talks about antioxidants; the word even gets bandied about in cosmetics commercials. The chemical—and literal—definition of an antioxidant is a substance that prevents oxidation because it likes to react with oxygen and does this well. A true martyr, an antioxidant throws itself into the firing line and cries, “Leave the polyphenols alone! Take me instead!”

LEMON JUICE IS also acidic. And acid obstructs many enzymes. Enzymes are huge, complex molecules, ingeniously shaped and folded like some sort of funky origami. Their three-dimensional structure is the secret to their precision. They can bring two specific reaction partners together by, for example, putting one in a perfectly pre-folded pocket and holding it there to provide the other with better access. But acid can unfold enzymes, meaning that they lose their three-dimensional structure and their effect as a chemical catalyst. This is why pickled gherkins last so long. The acetic acid preserves them. There are even bacteria that, with acid, help to preserve foods. I need to emphasize here that not all bacteria are bad, and sometimes there’s a fine line between good and bad. Milk goes sour due to lactic acid, which is produced by bacteria. Lactic acid is specifically used to make yogurt; certain lactic acid bacteria are added to the milk, turning it into acidic yet tasty products that last longer. The same trick is used to make sauerkraut, which is famously long-lasting.

Acetic and lactic acid bacteria aren’t the problem—the problem is the CHEMICAL preservatives!

First, let’s agree to call them “artificial preservatives”—pre-servatives created in a lab. Look at the ingredients listed on a pack of food and you’ll find artificial preservatives indicated by mysterious “E numbers.” The most important are acids such as sorbic acid and its salts, sorbates. You’ll find them listed under E 200, E 202, and E 203. Their chemical structure is a little like that of fatty acids and their salts, which we use as soaps. They are metabolized like natural fatty acids in foods, and you don’t need to worry about toxicity. Sorbates and sorbic acid also have a fairly unobtrusive taste and smell.

Sometimes other acids are needed too, such as benzoic acid and its salts, benzoates. They can be found under numbers E 210 through E 213. They target yeasts and molds that run rampant even at low pH levels (i.e., in the presence of other acids) and are used in acidic foods like mayonnaise, canned fish, pickles, and soft drinks. Benzoic acid isn’t as free from scandal as sorbic acid. There’s a suspicion that benzoic acid may make children hyperactive, but as the European Food Safety Authority has established, there is no scientific evidence to back this up. Benzoic acid and benzoates are officially classed as safe.

As a chemist, I see some objections that particularly annoy me. Again and again, I read that benzoic acid is a naturally occurring substance and therefore harmless, but benzoates are artificial and therefore dangerous. This is nothing more than mindless chemism—benzoic acid and benzoates are two different forms of the same molecule! Like fatty acids, benzoic acid is a carboxylic acid.

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