A Field Guide to Sugars
Should sugar be a controlled substance? For the love of honey, no! Dietitians can take away my trans fats and feed me one percent milk, but show mercy and leave me my sugar. Sugar is the most basic food there is. As a molecule, it's one of the world's most fundamental. It's the first incarnation of any organic substance, born inside a leaf from carbon dioxide, sunlight, and water. During digestion, it's also the final incarnation of our food (no matter what we had for supper) before our cells burn it for energy.
But if sugar is so simple, why are Twinkie packages so hard to read? Why are snacks, desserts, condiments, and TV dinners stuffed with so many sweetening agents? For that matter, why do those health-store, honey-sweetened cookies have that thin, slightly tinny taste that sugary cookies lack?
The answer, of course, is that sugars come in many varieties. The variations are minute—look at a molecular diagram and you'd be hard pressed to pick one from another—but they impart stark differences in taste and cooking behavior. That's why we need just the right combination to get that Twinkie to taste right.
So here's a breakdown of the common sugars and where you might find them. Use it for reference, or for sweet reflection (many thanks to Harold McGee and Alan Davidson):
Glucose (also called dextrose): The simplest sugar (but weirdly one of the least sweet), this is what your cells burn for energy. When plants or animals need to store glucose, they stack the molecules into long chains to make starch. Like all sugars, glucose contains only carbon, hydrogen, and oxygen. Glucose is shaped more or less like a single hexagonal ring, so it's called a monosaccharide.
Fructose has exactly the same number and type of atoms as glucose, just arranged differently. This slight change makes fructose about twice as sweet as glucose. Fructose is the main sugar you find in honey, giving it its almost jarring sweetness. Some clever people have realized that baking with doubly sweet fructose means you can make treats with half the sugar calories of glucose. Remarkably, though, fructose molecules change shape and lose much of their sweetness when they are hot, so this trick doesn't work in sweetening tea or coffee.
Sucrose is the most common sugar made by plants, and it's the molecule we extract from sugarcane or sugar beets and turn into table sugar. It consists of one fructose molecule joined to one glucose molecule. That's two rings, so sucrose is referred to as a disaccharide. We all love sucrose (if not quite as much as John Travolta did when he played that annoying angel in Michael). And conveniently for our tongues if not our waistlines, it remains delicious even at very high concentrations.
Maltose, found in malt extract, and lactose, found in milk, are two more disaccharides that are much less sweet than sucrose or fructose.
High fructose corn syrup is what we get when we cook down the starches from corn kernels to liberate the sugars they contain. About 75 percent fructose and the rest glucose, it's about as sweet as table sugar. And because American corn is so cheap (artificially, as Michael Pollan has pointed out), it has become ubiquitous as an industrial-scale food sweetener.
Maltodextrin is another variety of processed corn syrup—in some respects another way to sneak sugar onto a wrapper's ingredient list without raising a consumer's eyebrows. A combination of glucose and maltose, maltodextrin is chewy and not particularly sweet.
Oligosaccharides are sugars consisting of more than two hexagonal rings, found in beans and other seeds. The neat thing about oligosaccharides is that animals can't digest them, but the bacteria in our intestines often can—leading to those remarkable intestinal chemistry experiments that sometimes happen after a meal of legumes.
This list doesn't touch the artificial sweeteners—like the Stevia Amanda wrote about. They all contain some non-sugar substance that tricks our tongues into registering sweetness. Other tricksters include artichokes, which briefly disable our sweet receptors so whatever we eat next seems sweet, as well as the really weird miracle berry, which can discombobulate your tongue for a few hours at a time.
Artificial sweeteners promise the impossible: they're hundreds of times sweeter than sucrose but contain negligible calories. If only taste were that simple. I've never had a zero-calorie dessert that could compare to the simple sucrose rush of chewing on a stalk of sugarcane. I'm supporting freedom for sugar in 2009!
(Note to Amanda: a cwt seems to be short for a hundredweight. Which is 100 pounds in the U.S. and 112 pounds in Britain. Can the "c" really be a holdover from the Roman numeral 100? Good old imperial measurement system.)