As soon as I talk about brewing beer with someone who doesn’t know how the process works, they ask “What makes a beer higher or lower in alcohol?” It’s a great question, but for someone like me, it ends up turning into a long winded answer. Well, the answer is simple, the more sugar there is, the more alcohol there will be. Usually, that doesn’t answer the question though. You have to understand how you get sugar and how you get alcohol. To help explain this further, I will talk about mashing malted barley to make wort, yeast, and how all of this creates alcohol.
Beer is essentially made from one ingredient, wort (pronounced “wert” by some people). You add yeast to the wort to create beer. Wort is a sweet and bitter liquid (depending on how much hops are added to it). Before adding hops to the boil, it is a sweet liquid. The sugars that make the wort sweet almost exclusively come from malted barley, but other adjunct ingredients can be used like rice, wheat, rye, different types of sugar like white and brown sugar, etc… After barley is harvested, it is taken to the malt house to make malted barley. Malted barley is made by spraying the grains with water and encouraging them to sprout. This germination process breaks down the endosperm and produces amylase enzymes (and other enzymes) that start converting the starch into glucose. As soon as the seed sprouts, heat is applied to stop the germination. The malted barley is roasted for a varying amount of time to create varying levels of roast. Base malt, the malt that makes up 80% to 90% of the grain bill, is not roasted very long. The result is a slightly sweet grain of barley packed with starch and enzymes locked in and ready to complete the conversion from starch to sugar. Brewers use this malted barley to create wort in a process called mashing.
Mashing is the process that converts the starches into sugar. The amount of malted barley and the type and efficiency of the mashing process will determine how much sugar is extracted. Mashing is accomplished by cracking the gains to expose the starchy endosperm and steeping them in a volume of hot water to reactivate the alpha-amylase and beta-amylase enzymes and encourage them to convert the starches into glucose sugar. Usually 1.25 – 2 quarts of water per pound of grain is used in the mashing process. Temperatures from 146° to 158° determine the amount of fermentable sugars and non-fermentable sugars are converted by the enzymes. Temperatures on the higher end result in more non-fermentable sugars and a fuller body beer, while lower temperatures result in more fermentable sugars and a lighter body and drier beer. Brewers adjust water amounts and temperatures in their mash profile depending on what characteristics they are looking for in their beer. It can take anywhere from 45 minutes to 90 minutes (or longer) to complete the conversion process depending on how much water is used. More water (higher water to grain ratio) creates more space between the grains and makes it harder for the enzymes to find starch and will take longer to convert. It does create more fermentable sugars though. Less water speeds up the conversion process, but will create less fermentable sugars which result in a sweeter and maltier beer. After the conversion is completed, the wort is drained from the mash tun. Depending on the mashing process used, the grains may be rinsed one or more times. This allows the brewer to get more sugar out of the grains that were left behind after draining. The rinsing process is called sparging. After sparging, the result is the sweet liquid called wort. To complete the process, the wort is boiled with hops to add bittering, flavor, and aroma to the beer. The sweet and bitter wort is rapidly cooled and prepared for pitching yeast. Before pitching the yeast, the amount of sugar is measured by taking a reading of the “specific gravity” with a hygrometer. This is called the original gravity (OG). The amount of sugar extracted from the grains, or the gravity, will determine how much alcohol is ultimately created. This is where yeast comes in.
Yeast, a single celled micro-organism (a type of fungus), is added to the wort, or “pitched”, to convert the glucose (sugar) in the wort into alcohol and co2 (and trace amounts of other stuff). This process is known to brewers as fermentation. Before pitching, the wort should be aerated with oxygen. The oxygen will allow the yeast to multiply before it starts fermenting. When the oxygen is exhausted, the yeast starts the fermenting process.
During fermentation, the yeast uses a process called “anaerobic respiration” to obtain its energy. All cells use respiration to obtain energy. Some use aerobic (oxygen) and others, like the yeast used to make beer, use anaerobic (no-oxygen). Anaerobic respiration is a cellular process in which energy is created in an oxygen free environment. This process, otherwise known as fermentation, is basically how the yeast generates alcohol and co2. For each molecule of glucose, yeast creates two molecules of ethanol and two molecules of co2, as well as ATP (adenosine triphosphate) for energy. From the yeast’s perspective, it needs the energy from the ATP, so alcohol and co2 are just waste products. As far as the glucose, it doesn’t matter where the sugar comes from, adding yeast to any sugary liquid will result in some amount of alcohol and co2, depending on how much fermentable sugar it contains.
Brewers will periodically measure the gravity of their beer during fermentation. You can tell fermentation is occurring because the gravity will slowly go down, indicating less sugar. When the gravity reaches a point it will not get any lower, the beer is done fermenting and the final gravity (FG) reading is recorded. An easy way to measure the amount of alcohol (ABV %) is to find the difference between the original gravity and the final gravity and multiply that number by 131.25. For example, if the OG was 1.065 and the FG was 1.009, the difference is .056. Multiplying that number by 131.25 results in an ABV of 7.35%.
So now you know, in a lot of detail, how alcohol is created and measured in a beer and what makes it higher or lower in alcohol. The basic thing to remember is sugar is extracted from grains in a process called malting and mashing to ultimately create wort. Yeast is added to the wort which converts the sugar into alcohol and co2. The more fermentable sugar there is the more alcohol the beer will contain.
Feel free to comment on this post. I would love to hear what you have to say, happy brewing!