Marlene Parrish - What Einstein Told His Cook 2

(To justify my heading, I am obliged to explain that the blue color of violets and the red color of roses are both due to an anthocyanin that is an acid-base indicator [see “A litmus quest,” chapter 1]. It is red in the slightly acidic rose petals and blue in the slightly alkaline violet petals.)

WHEN GREEN GROWS GRIM

Why do my green vegetables turn a drab color when I cook them?

The green color in plants and algae is a miraculous molecule called chlorophyll that can absorb the energy of sunlight and use it to convert carbon dioxide and water into glucose and oxygen gas. The plants then either use the glucose directly for their own growth energy or polymerize it (connect thousands of glucose molecules together) to form starches, which they store for future use. And because animals derive their vitality from eating those sugar and starch carbohydrates in plants, the chlorophyll molecule can be thought of as the source of most life on Earth.

But chlorophyll is a fickle friend to humans, the only species that cooks its plant foods to tenderize them. For when we do, the green color can become a dreary, unappetizing khaki. What happens is that the chlorophyll turns into chemicals called pheophytins.

A chlorophyll molecule consists of a conglomeration of carbon, hydrogen, oxygen, and nitrogen atoms called a porphyrin (POR-fer-in), with a magnesium atom buried in the center. But chlorophyll isn’t a single chemical compound. There are two main types, which chemists, always eager to demonstrate their literacy, have named chlorophyll a and chlorophyll b . Chlorophyll a is blue-green, while chlorophyll b is a yellowish-green. Different ratios of a ’s to b ’s (most often two or three a ’s to each b ) determine the exact hues of various green plants.

When we cook our green beans, peas, Brussels sprouts, broccoli, or spinach, the heat first changes the shapes of the chlorophyll molecules (they isomerize ), and if the vegetable is slightly acidic, as most vegetables are, the magnesium atoms may be ousted and replaced by a couple of the acid’s many hydrogen atoms. This transforms the chlorophylls into chemicals called pheophytins . Chlorophyll a turns into a grayish-green pheophytin and chlorophyll b turns into an olive-green one. Because chlorophyll a is usually more prevalent and undergoes this change more rapidly than chlorophyll b, the grayish-green color is what we get.

The fact that acids initiate the chlorophyll-conversion reactions has on occasion tempted people to add a pinch of baking soda (sodium bicarbonate) to the cooking water to make it alkaline. But alkalinity attacks the complex carbohydrates that cement the vegetables’ cells together, so one is merely trading ugliness for mushiness—with the dubious bonus of a soapy flavor from the bicarbonate.

Another chemical oddity in cooking green vegetables is that sodium, magnesium, and calcium salts inhibit the chlorophyll-conversion reactions, presumably by making it more difficult for the hydrogen atoms to get through the cell membranes and oust the magnesium atoms. Thus, salted cooking water (containing sodium chloride) and hard water (containing magnesium and calcium salts) help to retain the green color.

The practical message in all this is that the quicker a green vegetable is cooked, the less of its chlorophyll can change to muddy-colored pheophytins. In one study, broccoli lost 17.5 percent of its chlorophyll after being cooked for five minutes and 41.1 percent after ten minutes.

GERM WARFARE

What’s the best way to wash my fruits, vegetables, and produce to make sure there aren’t any germs, pesticides, and insecticides on them?

Nothing personal, but haven’t we become a bit of a paranoid society? Our drugstores and supermarkets cater to our fears (or do they encourage them?) by displaying dozens of antibacterial soaps, sprays, gels, lotions, hand washes, body washes, wipes, deodorants, and mouthwashes. Television commercials strike terror in our hearts by suggesting that there might be a germ or two lurking in our toilet bowls. (Well, for crying out loud, where are those poor little germs supposed to live?) I call it “bacteria hysteria.”

What does this have to do with food? A search of my unanswered reader mail (forgive me; I try) reveals 130 communications bearing the words germs or bacteria and 195 bearing some form of the word danger , referring to food contamination. It sometimes seems as if there are more people who are afraid of their food today than people who are enjoying it. Are we becoming a nation of verminophobes, mysophobes, toxiphobes, and sitophobes? (See definitions below.)

I generally avoid writing about health issues because I’m not a microbiologist, nutritionist, or physician. But I will say a few words about possible pathogens and toxins in or on our foods—in particular, on our fruits and vegetables. After all, they have inevitably been in contact with microorganism-harboring soil, and have possibly been subjected to agricultural chemicals such as weed killers and insecticides, not to mention manure and other “natural” fertilizers used to raise organic foods.

There have been several products on the market intended for washing our lettuce, scallions, tomatoes, apples, and such, presumably to remove both bacteria and toxic chemicals. In the fall of 2000, Procter & Gamble introduced a product called Fit Produce Wash, but they soon discontinued it and sold the formula to HealthPro Brands. At $5 for an 8.5-ounce bottle (no wonder it didn’t sell), it was a mixture of water, oleic acid, glycerol, ethyl alcohol, grapefruit oil, potassium hydroxide, baking soda, and citric acid.

Why these particular ingredients? The glycerol, alcohol, and oleic acid were presumably intended to dissolve and remove chemicals such as pesticides, which are generally insoluble in water. The potassium hydroxide attacked waxes, which are in any event approved by the FDA as harmless coatings for fruits such as cucumbers. As far as I can tell, the baking soda and citric acid were there only to react with each other to emit carbon dioxide gas, producing an Alka-Seltzer-like fizz to give the impression that the product was working hard.

Still on the market at this writing is Bi-O-Kleen Produce Wash, which “contains no animal ingredients” (should we have expected any?) and is “PETA approved” (but does it kill those poor little microorganisms?). It is made of “lime and lemon extracts, grapefruit seed extract, coconut surfactants, cold-pressed orange oil, and pure filtered water.” I don’t know if all those tutti-frutti ingredients do anything besides making the stuff sound yummy, but the “coconut surfactants” happen to be a synthetic (very unnatural) chemical called sodium cocoyl isethionate, a high-sudsing detergent used in soaps and shampoos.

Bi-O-Kleen has a couple of sister products. Veggie Wash claims to be “non-toxic, non-fuming, non-hazardous, non-caustic, and hypoallergenic” (and non-radioactive and non-explosive?). Organiclean contains “an anionic surfactant derived from coconuts”—very likely that same sodium cocoyl isethionate. All three products claim that they are more effective than plain water in cleaning fruits and vegetables.

Most experts, however, say that washing vigorously in running water is still the best bet. Running water will wash soil particles out of leafy greens, and that’s where the harmful bacteria, if any, are most likely to be hiding. Water won’t actually kill them, but neither will the produce-wash products, for that matter. If they did, they might leave residues of toxic (to humans) materials on the food. Moreover, if they claimed that they killed microorganisms, they would have to be tested for human safety and registered with the EPA as pesticides. (What irony!) So the produce washes sold to retail consumers are merely washes, not disinfectants. They’re especially good at washing money out of your pocket.