Ok, fully lubricated.
Anywho, I had a question for you GF. How do the make light beer? With soda it is pretty clear, no sugar, use sugar substitute = diet (or light) cola or whatever. But with beer the yeast needs sugar to convert to alcohol so how do they make light beer?
TIA.
Light beer is made with less ingredients.
Alcohol itself contains a lot of calories. There is simply no way to get fewer calories and keep the alcohol content high.
So, in practice this pretty much means that, say, you were going to make 5 gallons of "regular" beer. You'd use around 10lbs of malted barley. To make that beer a "light" beer you'd keep everything else the same* but use 6lbs of grain instead. From that grain you'd get less sugar and therefore less alcohol.
To get a little more complicated, some beers have higher finishing gravities** while having the same alcohol content. There are several ways to increase the finishing gravity, which is desirable for certain styles of beer (American light lager not being one of them). The first has to do with yeast strain. Some yeast "attenuates" better than others. The second way is to mash at a higher temperature. It's during the mash that the starch in grain is converted into sugar. At higher temps more of the starch converts to more complex sugars. Some of these complex sugars are inedible for the yeast (or as a brewer would say, non-fermentable). The third way would be to use specialty grains that provide caramelized (non-fermentable) sugars to the wort. These specialty grains are malted like typical base grain but then kilned at various temps and for various times and with various amounts of moisture to attain the desired qualities. One of the most basic types of specialty grains are crystal malts (in England these are called caramel malts) and they're typically referred to by the amount of color they add per a specific amount of grain to water. So on the lighter side you have C10 and on the higher side you have C120. The higher the number the darker the grain and the less fermentable the sugar it provides. These are used for color adjustment as well as to provide the desired amount of body/mouthfeel as well as to aid in head retention.
To get the lowest possible gravity with the highest possible alcohol content you can ferment simple sugars, like table sugar, dextrose (corn sugar) or honey. But if that's all you use the end result would be nothing like beer.
*you might also adjust the amount of hops used to maintain proper balance
**Brewers use "standard gravity" (water = 1) to determine how much sugar is in the wort and then compare the "original gravity," taken before fermentation, to "final gravity" to figure out how much alcohol the beer contains.
