"What's a Carbohydrate And What's It Doing In My Drink?" by Mike Sherlock

Diet beers are a not a new fad. They've been around for a long time. They were called "low carb" beers while the Atkins and South Beach diets were all the rage. Now "ultra light" beers (such as MGD 64, Michelob Ultra, Budweiser Select 55) push their low-caloric content, but they're also low-carb. So what is a carbohydrate anyway?

Break down the word: carbo and hydrate. "Carbo" refers to carbon and "hydrate" refers to Oxygen and Hydrogen. When you are dehydrated, your body needs water; two Hydrogen atoms bonded to a single Oxygen atom (H2O). A hydrate is any molecule formed with Hydrogen and Oxygen in this proportion of 2 to 1, respectively.

Carbohydrates are categorized as saccharides; mono-, di-, oligo-, and polysaccharides. Monosaccharides are referred to as "simple sugars." When you spoon sugar into your coffee, you're adding the monosaccharide sucrose. Polysaccharides are commonly called "complex carbohydrates." Brewers are concerned with the complex carbohydrate called starch.

Starch is a fundamental compound required for life. Plants store energy in starch and human beings require it in their diet to live. Oddly enough, low-carb dieting seeks to remove nearly all starch sources from one's diet (pasta, potatoes, bread, etc.). Beer was traditionally seen as a healthful drink since it was cleaner than water (it gets boiled) and drinking it allowed hard-working guys to toil longer (since calories = energy).

Barley contains lots of starch (as do all grains). But yeast can't eat starch and produce ethanol and carbon dioxide. So, a brewer has to perform a process called mashing in order to break the complex carbohydrate down into simpler monosaccharide or disaccharide structures in order to actually make beer. Luckily, the enzyme amylase (the same enzyme found in saliva) also lives in barley. A brewer just needs to mill the malted barley, add hot water, and let the enzymes go to work for an hour or two. The process is only slightly more complicated than making tea.

The resulting liquid is called wort. That's nothing more than unfermented beer. It tastes and smells sweet (after all, it's loaded with sugar). The mashing process doesn't convert every last drop of starch into simpler sugars for the yeast to eat. Even if it did, yeast can't eat all the sugar anyway.

Some sugars are unfermentable and sometimes the yeast just dies off before consuming all the ones that are fermentable. These are called residual sugars. Residual sugars are carbohydrates left in the finished product and result in what's known as a "beer belly."

Controlling the amount of sugar in the wort allows a brewer to also control how many calories/carbohydrates are in the finished product. There are a couple of ways to do this. One could use less or different kinds of grain to affect how much sugar is available for the yeast to eat. Or, one could break down the unfermentable complex carbohydrates into simpler, fermentable ones. But how does that happen?

Ever use Beano? Beans and legumes contain complex carbohydrates which ferment in your intestines and cause flatulence (this is a different kind of fermentation than brewers perform). Beano works by introducing an enzyme called alpha galactosidase to your system, breaking down the complex sugars into simpler ones your body can't ferment. Interestingly, this enzyme can be added to wort, breaking down complex carbohydrates into simple sugars which brewer's yeast CAN digest resulting in less residual sugar and, thus, a low-carb, low-calorie beer.

Of course the presence of more fermentable sugars also means the beer is going to have more alcohol. I'll leave it up to the reader to decide if that is a good or a bad thing.

Beer snobs tend to shun these lighter beers as they sometimes taste "watery" or may have a "hot" alcohol flavor. Some brewers joke that they can replicate one of these beers by pouring a shot of vodka into a glass of seltzer. But things that are better for you don't have to taste bad.