Expert: Ed Westemeier - 11/14/2011

Question
Hey Ed,

I've been looking into the nutritional breakdown of beer, and have worked out that it's calories come from roughly half ethanol and half carbohydrates (or something like that) with a tiny percentage from protein.

What I'm trying to work out is where exactly the carbohydrates are coming from. Is it residual (unfermented) sugar? or maybe starch or cellulose?


Cheers.

Answer
You have it right.
The starches are mostly (but not completely) broken down into sugars, so there is some starch contribution to the carbohydrate content of the beer.
Most (but not all) of the sugars are fermentable, and they will be the source of the alcohol-derived carbs.
The remainder of the sugars are long-chain molecules that contribute the rest of the carbs. Generally speaking, these are called dextrine by most brewers, although that's kind of a generic name. They are mostly all those big sugar molecules (the ones that end in "-ose" that hold the carbs. Lager yeasts will ferment more of them than ale yeasts (as a general rule), but there are always some left. Don't be confused by the fact that they are called unfermentable sugars -- these molecules don't contribute any perceived sweetness like the simpler sugars, but they certainly contribute to the body and mouthfeel of the beer.
The rest (a small portion) of the carbs come from starches that the enzymes haven't broken down, proteins, and remaining plant matter from the grain.