Karen Hill

The word rancid is a sort of catchall that comes from the Latin rancidus, meaning rank or stinky. The word has no explicit chemical meaning. It is used loosely to mean bad-smelling and tasting, most often in reference to over-the-hill fats. There are several things you can do to avoid fat rancidity. But first, let’s … Read more

A molecule of any fat (a triglyceride) contains three fatty acid molecules attached to a glycerol (glycerin) base. The three fatty acids can be any combination of saturated, monounsaturated, or polyunsaturated. The health consequences of any given fat are purely those of the fatty acids (I’ll call them FA’s from here on) it contains. The … Read more

There is a lot of confusion surrounding trans fatty acids or “trans fats.” The public’s concern about trans fatty acids was heightened on July 1, 2003, when the FDA issued its final rule on the labeling of foods containing trans fatty acids, to wit: “In this final rule and given the current state of scientific … Read more

Oils are liquids whose molecules don’t stick together very strongly, so they can slide easily past one another. That’s what makes them slippery. But chemically speaking, edible oils and inedible oils are quite different. And thereby hangs an embarrassing tale. A few decades ago I was teaching graduate-level chemistry in Spanish (what chutzpah!) at a university in … Read more

Plantains are tropical fruits closely related to bananas, both members of the genus Musa, but much starchier and containing much less sugar when ripe. They’re also known as cooking bananas, which is a clear tip-off that they’re not meant to be eaten raw. Plantains are a staple in Africa and especially in Latin America, where … Read more

As bananas ripen and get sweeter, that would be creating calories, and calories are energy. Energy can come only from other forms of energy (heat, mechanical, electrical, and so on) or from matter via E = mc2. If a banana knew how to convert matter into energy, as uranium does, we could make atomic “B-bombs” … Read more

If you smashed all the bottles of chemicals in a chemistry lab with a baseball bat, you wouldn’t be surprised at any unusual chemical reactions that occurred as their spilled contents ran together on the floor, would you? Well, plants are made up of remarkably packaged, exquisitely organized little “bottles of chemicals” called cells. When … Read more

The chemical changes that take place in ripening fruits are quite complex, with different fruits differing mainly in the timing of those reactions. For every type of fruit, there comes a time when the ripening reactions reach their peak, after which senescence (deterioration) sets in, ultimately leading to decay. That’s Nature’s dust-to-dust plan, and the … Read more

In the pages of his published works, William Shakespeare used the words fruit or fruits 122 times. On the pages of the King James Bible, the words fruit or fruits appear 361 times. On the ethereal pages of today’s World Wide Web, the words pop up more than 600 million times. In metaphor, we speak … Read more

Always do what your mother says. When I was a kid my mother told me that if I wore my rubber rain boots in the movies it would ruin my eyes. I forgot to take them off once, and today I have to wear glasses. But seriously, your mother’s dictum is somewhat more rational. Garbanzos, … Read more

As the key element in amino acids, the building blocks of proteins, nitrogen is a necessary component of all living things, both plant and animal. On Earth, there is a virtually unlimited supply of nitrogen gas molecules (N2) in the atmosphere; air is about 80 percent nitrogen. But the bond between those two nitrogen atoms … Read more

One thing you can do to prevent farts is to cut down on the amount of alfalfa in your diet. But giving up all those other legumes, including peas, peanuts, lentils, and the dozens of kinds of beans, would be too much to ask. It’s just one of those many times in life when we … Read more

Miso, known as “fermented soybean paste” in English, is one of the most versatile products you can find in Japanese and Korean markets. It’s sold either by itself, to be used in home cooking, or already incorporated into soups, salad dressings, and sauces. Like soy milk and tofu, miso begins with soaked, steamed, and ground … Read more

Tofu is made by curdling soy milk, and then they manipulate the curds in different ways. A variety of acids, enzymes, bacteria, and salts are able to coagulate the proteins in soy milk, that is, to unwind their long, twisted molecules, allowing them to rebind (cross-link) to one another like rungs in ladders, forming a … Read more

Many people have often wondered how they milk those little soybeans, haven’t you? Soy milk is made by soaking, boiling, grinding, and pressing the liquid out of soybeans. The liquid is called “milk” because it is white, but it bears as little relationship to cow’s milk as does milk of magnesia. Soy milk is a … Read more

Cucumbers have been cultivated for thousands of years, and like many food plants, they have been improved by cross-breeding to accentuate the better and eliminate the bitter. Old recipes often include a de-bittering step, such as soaking the slices in salt water. (I doubt that that works anyway.) But modern varieties are rarely bitter except … Read more

Vidalias aren’t unique in their mildness. There are several brands of mild onions grown in other parts of the country, including the Maui, Walla Walla, Texas 1015, and OSO. Note that I have called them “mild,” not “sweet.” They don’t necessarily contain more sugar than other onions; they simply contain lesser amounts of both the … Read more

What makes us cry is all the misinformation going around about onions, primarily about what causes the eye irritation and how sweet onions differ from ordinary ones. The tear-producing chemical (the lachrymator) in onions is not pyruvic acid, as has too often been stated in print. Nor does pyruvic acid “come from sulfur in the … Read more

Plants in general are made up almost entirely of compounds of carbon, hydrogen, and oxygen, compounds that chemists refer to as organic, with no relation to the word used to designate foods that conform to the USDA’s National Organic (Foods) Program. Minerals, on the other hand, are the seventeen inorganic chemical elements that are essential … Read more

If you check the “USDA National Nutrient Database for Standard Reference”, you may be surprised to find that spinach does not contain an unusual amount of iron: it has less than most breakfast cereals, about a quarter as much as raw clams, and about the same as canned pork and beans (not counting the can). … Read more

All parts of the rhubarb plant (Rheum rhaponticum) contain various amounts of oxalic acid and its chemical progeny, oxalate salts, ranging from to 1.4 percent. That’s largely what gives rhubarb its prodigious pucker power, which must be tamed with sugar in the pie. Oxalic acid and oxalates are indeed poisonous. During World War I, when … Read more

Yukon Gold potatoes, along with cabbage, onions, and yellow rice, get their yellow color from chemicals called anthoxanthins. Anthoxanthins react with traces of metals such as iron and aluminum, which turn them blue-gray. A carbon steel knife can have that effect, so it’s best to cut and slice these vegetables with stainless-steel knives. Other varieties … Read more

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 … Read more

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 … Read more

The kaleidoscope of brightly colored fruits and vegetables, the red tomatoes, watermelons, strawberries, and beets; the orange carrots, sweet potatoes, pumpkins, apricots, and mangoes; the yellow lemons and squashes; the bluish-purple grapes, plums, and cabbages; and all the green beans and leafy vegetables, are due to a variety of phytochemicals that can be classified into … Read more

Thousand-year-old eggs, called pidans in Chinese, are a tongue in cheek eggsaggeration. Less lyrical Chinese may call them hundred-year-old eggs. Truth be told, however, they’re only about a hundred days old, which may strike you as bad enough. Here’s how they’re made. Take a fresh duck egg in the shell, plaster it all over with … Read more

It may be difficult for any mortal to achieve divinity, but with patience you can do it. Pasteurized-in-the-shell eggs are intended to eliminate the hazards of the food-poisoning bacteria Salmonella enteritidis and other salmonella species that can be found in poultry, meat and meat products, raw milk, and the yolks (usually not the whites) of … Read more

The American Egg Board recommends the following method for making hard-boiled eggs: “Place eggs in single layer in saucepan. Add enough tap water to come at least 1 inch above eggs. Cover. Quickly bring just to boiling. Turn off heat. If necessary, remove pan from burner to prevent further boiling. Let eggs stand, covered, in … Read more

A hen’s egg contains a small air pocket just inside the shell at the broad end, the purpose of which is to let the chick breathe while pecking its way out on its birthday. Because the shells are porous and permeable to gases, outside air can diffuse in and exchange with the air inside. As … Read more

The albumen, or white, of an egg is 88 percent water and 12 percent a mixture of about a dozen different proteins. But most (54 percent) of the protein is ovalbumin, each of whose huge molecules contains more than three thousand atoms, including only six atoms of sulfur. Nevertheless, that tiny amount of sulfur can … Read more

First of all, the greenish-black color of hard-cooked egg yolks is harmless. Even if the colored substance were a toxic compound (it’s not), it is present in only trace amounts. As an egg ages, some of the sulfur-containing protein in the egg white slowly decomposes, forming a small amount of evil-smelling hydrogen sulfide gas, H2S. Heat … Read more

When the eggs are done, cool them down quickly in cold running water. That shrinks the albumen away from the shell somewhat and makes an egg easier to peel. It also keeps the yolks from turning green. Very fresh eggs are harder to peel because the albumen tends to stick to the membrane on the … Read more

It’s not true that adding salt to the water before boiling eggs prevents the eggshells from cracking. Salt (sodium chloride) has no effect on eggshells (calcium carbonate), either chemically or physically. An eggshell can crack when there is a sudden temperature difference between a cold shell and hot water. The heat makes the shell expand … Read more

In general, the yolks in double yolk eggs are smaller but the eggs overall are bigger. About 3 to 5 percent of hens’ eggs have two yolks. Some hens, driven by their genes and the conformation of their oviducts, seem to specialize in producing these twins. When you find a double yolker in an otherwise … Read more

Red spots in eggs doesn’t mean that the egg was fertilized, and it will not hatch no matter how long you sit on it. Hens that lay eggs for commercial distribution have never even seen, much less “dated,” a rooster. Layers just aren’t breeders. The red spots are indeed blood, from the rupture of a … Read more

Unfortunately, we agree with every other printed dissertation on eggs to assure you that no differences in flavor or nutrition have been found between brown eggs and white eggs. Just as brown-skinned people produce brown-skinned children, brown-feathered chickens lay brown-shelled eggs. Among the brown-egg layers are the Barred Plymouth Rock and the Red Rock Cross, … Read more

The USDA grades eggs according to quality, not according to freshness, as AA, A, or B. To earn a grade of AA, an egg must have an air cell within the wide end that is less than an eighth of an inch (3 millimeters) deep; a shell that is well shaped and clean, with very … Read more

Calling butter a fat is like calling a truffle a mushroom. Butter’s magic arises from its uniqueness, not only in its history and renowned flavor but in its composition. Butter contains a relatively large amount of water, and it’s the water that gives butter its unfat-like properties, such as being able to bring a sauce … Read more

In addition to the hundreds of classic cheeses developed over more than a thousand years in various parts of the world, we are blessed today with many options for adding cheese flavor, be it natural or artificial, to our snacks and dishes. Dozens of cheesy (often in more ways than one) factory-produced concoctions beckon to … Read more

String cheese is a novelty form of mozzarella, a soft, white, elastic cheese. American mozzarella, made from cow’s milk, is a poor relation to the Italian mozzarella (rnozzarella di bufala) from the region along the shinbone of the Italian boot. Mozzarella di bufala is made from milk of the Asian water buffalo, introduced into Italy … Read more

First, we have to straighten out some terminology: • Penicillin (not penicillium) is the name of the drug. • Penicillium (not penicillin) is the genus of the mold that produces the drug. • Listeriosis and brucellosis are diseases caused by bacteria, not the names of the bacteria themselves. The drug. The oft-told story of the … Read more

The percentage sign on the label of a Brie cheese is the percentage of fat in the cheese, but expressed on what a chemist would call a dry weight basis, which is the percentage of fat in what would remain after all the moisture were removed. The famous and ancient (eighth-century) French soft cheese called Brie, … Read more

Cream cheese and cottage cheese are not purely American, but primarily so. What cream cheese and cottage cheese have in common, along with French Neufchatel and a few others, is that they are not aged or ripened. The milk or milk-and-cream mixture is curdled by an acid (usually lactic acid), and the curds are ready … Read more

Ice cream shrinks when it’s melted because it is half air. Federal regulations specify that the amount of “overrun” in ice cream must be less than t00 percent. Overrun is the increase in volume between the product’s ingredients and the final, air-whipped product. A doubling of volume, known as t00 percent overrun, means that the … Read more

Most people seem to think so that eating ice cream in hot weather cools you off. At the local Dairy Queen there is always a long line of people seeking cool after-dinner desserts in the summer, but starting the day after Labor Day, the place is virtually “desserted.” The answer to the question is in … Read more

As (chocolate) Dairy Queen aficionado myself, we conducted an investigation. I bought a quart container of soft-serve ice cream and measured its temperature by plunging an instant-read thermometer into the middle and waiting for a couple of dozen “instants” until it reached its final reading. On the two occasions it measured 14 and 16°F (-10 … Read more

In principle, and in many countries of the world, yogurt is very simple. It is made by adding certain strains of beneficial living bacteria to the milk from a cow, goat, or sheep. The bacteria feed on the lactose (milk sugar) in the milk, metabolizing it into lactic acid and other interestingly flavored chemicals, some … Read more

Cream is made from milk by boosting the percentage of milk fat (also called butterfat, because it is made into butter) beyond the percentage the cow put into it. That is, some of the watery, non-fatty part of the original milk (the “skim milk”) is removed to increase its “richness”: its smooth, unctuous mouth feel. … Read more

Remember when true skim milk was blue-white, and the edge around the glass was translucent? Why can’t we have good old skim milk back again? When a billboard asks, “Got milk?,” we may be tempted to reply, “Can you be more specific, please? Are you asking about raw milk, pasteurized milk, homogenized milk, aseptically packaged … Read more

I have heard about all sorts of treatments for removing red wine stains from tablecloths and clothing. The things I hear about most often are club soda and salt, but I’ve tried both without success. There must be a way that really works. Many people have asked my expert advice on this profound scientific question. … Read more

Having spent decades on a university campus (no, it didn’t take me that long to graduate; I was on the faculty), I have heard more than a little about what the students call “hearty parties.” Translation: binge drinking. But the college crowd doesn’t have a monopoly on binging, whether deliberate or accidental. For us in … Read more

First, the colder the ice the better. Colder ice will cool the liquid faster, just as colder rocks would do. And melting is not necessary for cooling; cold rocks would do the job as well. If two substances are in contact, heat will flow automatically from the warmer one into the cooler one. In this … Read more

Any dyed-in-the-cotton Southerner knows there is “plenty” in mint juleps. When sipped at the speed of a Southern drawl on a hot summer’s eve beneath a fragrant, blooming magnolia, few beverages are more refreshing than a mint julep, or more insidiously intoxicating, because its seductive sweetness masks the fact that it is virtually straight bourbon. … Read more

What sets Kentucky bourbon and Tennessee sour mash whiskey apart is largely local pride, but virtually identical whiskey can be made anywhere. They just can’t use those state names if they were made, for example, in North Dakota. First, what is it that makes bourbon bourbon? Bourbon is officially defined by the federal Alcohol and Tobacco … Read more

When planted in the bottle, champagne corks were just as cylindrical as the corks used in still wine bottles, only bigger. A normal-sized wine cork is 24 mm (about 0.94 in.) in diameter; it is compressed and inserted into an 18 mm (o.71 in.) bottle neck by a “corker” machine. Cork is quite compressible. Champagne … Read more

A silver fork would work just as well to prevent champagne from going flat. So would a railroad spike. Or a magic wand, for that matter, because the spoon does absolutely nothing. The spoon dodge is pure bunk. Or, in British terms, humbug and poppycock. Champagne simply doesn’t go flat as fast as beer and … Read more

There are some five thousand varieties of wine grapes that could be used in almost one hundred appellations d’origine in France alone, plus seventy-four appellations in California, not to mention Australia, Chile, and dozens of other wine-producing countries. Multiplied by perhaps ten years of vintages, that amounts to over 37 million possible bottles of decent … Read more

Sulfites, not to be confused with sulfates, are a family of chemical salts derived from sulfur dioxide (SO2). They are formed during the fermentation of wine from sulfur compounds naturally present in the grapes, so a certain small amount is indeed natural and unavoidable. In addition, sulfites (or sulfur dioxide gas from burning sulfur) have … Read more

Hops are the dried flowers of the hop plant, known to botanists as Humulus lupulus. It’s a tall, climbing vine of the hemp family, and its flowers impart that mellow bitterness to beers and ales, balancing the sweetness of the malt. They also contribute a grassy flavor note and a pleasant aroma, depending on when … Read more

Even though they are members of the same chemical family, there are vast and crucial differences among the alcohols, and it can be a matter of life and death to be aware of them. Alcohols are a large family of organic (carbon-containing) chemicals that are related in two ways: their molecules contain one or more … Read more

There is a difference between what a chemist calls a calorie and what a nutritionist calls a calorie. The chemist’s calorie is the amount of heat energy required to raise the temperature of one gram of water by one degree Celsius, whereas the nutritionist’s calorie, the calorie you see in diet books and on food … Read more

I doubt that the ancient Greek philosophers spent much time on this (especially since they didn’t have coffee), but it’s a challenging question, if not an earthshaking one. You could settle it with an accurate thermometer, but you’d have to measure out exactly the same amounts of coffee and cream into exactly the same type … Read more

Most connoisseurs agree that in order to extract the proper amount of flavor from black or oolong tea leaves, the water must be as hot as possible. But no matter how much you heat it, water will never get hotter than boiling: 212°F (100°C), minus a degree or two, depending on the altitude and weather. … Read more

Caffeine is very soluble in water; as much as 150 grams of caffeine could dissolve in a cup of boiling-hot water. But there isn’t anywhere near that much caffeine in a tea bag. Typically, it’s less than a thousandth of that. What caffeine there is is extracted out of the tea bag almost completely in … Read more

Here’s what was going on in the tea when you add baking soda. You’ve heard people talk about a “litmus test,” to show whether a politician is on one side of an issue or the other? Well, litmus is a dye obtained from lichens; it is pink when in an acidic environment and blue when … Read more

Enzymes have been misunderstood almost as much as instruction manuals for VCRs. Everyone know that enzymes play essential roles in all living things, but what exactly are they? Are they alive, like bacteria? No. They’re chemicals, almost all of them proteins, that accelerate the complex chemical reactions essential to living things, both plant and animal. … Read more

All tea comes from the same, one-and-only tea plant, Camellia sinensis, whose leaves certainly were chlorophyll-green on the living plant. But based upon how the leaves are processed, there are three types of tea: green, which is consumed mostly in the Far East; black, the favorite of the British and other Westerners; and oolong (“black … Read more

Tea leaves contain tannins, a loose collection of chemicals that give tea much of its flavor and body, and especially that astringent, puckering effect in the mouth. They dissolve in water to form a clear solution, as long as the water isn’t too cold or slightly alkaline. Your cloudiness occurs when some of the tannins … Read more

Let’s follow the fate of the soda from the time that rascal put it in the freezer, probably with the misguided intention of keeping it nice and fizzy till the next attack of thirst. All liquids turn into solids, that is, they freeze, when they get cold enough. Pure water freezes at 32°F (0°C), but … Read more