This is a follow up on my last post about the health
benefits of beer. We have learned how wine is made, we have even learned about
grappa, but we have yet to learn about the process of brewing beer. This makes
complete sense because we are in the land of wine… not beer. However, I am here
to educate everyone on the process of brewing beer. I have personally brewed
beer with my roommates but we just followed the instructions in the kit. Here,
I will discuss the chemistry of the brewing process.
First and foremost, we need water, malts, hops, and brewing
yeast. Different combinations of various malts and hops give beer its unique
flavor. These two ingredients distinguish malts from ales, light beers from
heavy beers, and all other beer varieties.
Malts
- Malts come from grains, often times barley or wheat. Malts are produced by the initiation of germination (or grain growth) by hydrogenation and then kilning arrests grain growth in order to preserve sugars and proteins. The temperature at which the grain is kilned influences the ultimate flavor of the beer. Low temperature kilning produces light malts in which the grain’s enzymes retain their enzymatic power. These low-temperature malts produce light beers such as pale ales and pilsners. On the other hand, high temperature kilning denatures the enzymes and slightly degrades the complex starches in the malt. The monomers of proteins and starches, amino acids and sugars, undergo condensation reactions known as the Maillard reaction to form dark heavy molecules. These high-temperature malts are used to produce darker beers such as malts, porters, and stouts.
- Malts are then sent to breweries. Here they are used is a step called “mashing,” in which the malts are ground into small granular pieces and then mixed with water and heated to 150 degrees Fahrenheit. At this temperature the malt’s enzymes are activated. Amylases break down complex starches into simple fermentable sugars. Proteases break down the proteins into amino acids. Lighter malts have higher enzymatic power and break down almost all complex starches into simple sugars. Darker malts have lower enzymatic power and thus leave complex sugars in the mixture. The difference in enzymatic power is a result of the temperature of kilning of the malts, higher temperatures denature the enzymes, which would break down complex compounds. The mixture of hot water and malts is then filtered and results in “wort”
Hops
- Hops come from the Humulus Lupulus flower. They are often times dried and compressed into pellets for beer brewing. Additionally, these pellets must be stored carefully because heat and oxygen can ruin them.
- The oils of hops give beer its bitterness and rich aroma. They are added to the “wort.” The main ingredients of hops are its alpha acids, which isomerize at boiling temperatures to give beer its bitter flavor and overall aroma (fruity to spicy). The isomerization of alpha acids produces the bitter flavor; therefore, adding the hops early on in the boiling process produces darker, more bitter beers. On the other hand, adding hops after the boil makes lighter beers. This prevents the isomerization of alpha acids.
- Nowadays, the bitterness of hops is rated by its alpha acid units (AAU). The higher the AAU, the more bitter the hops.
Yeast
- Often times, two types of yeast are used Saccharomyces cerevisiae and Saccharomyces uvarum. The S. cerevisiae are known as top-fermenting yeast because they tend to gather at the surface of the beer and they prefer hotter temperatures at the top of the mixture. The S. uvarum are known as bottom-fermenting yeast because they aggregate at the bottom of the mixture and prefer the lower temperatures at the bottom of the mixture.
- The “wort”, which now contains the hops, is then mixed with yeast. “Wort” contains essential nutrients for the survival of the yeast such as amino acids and sugars. The yeast breaks down the fermentable sugars into glucose, which is then made into ethanol and carbon dioxide.
Once the mixture is complete, it may be monitored. Larger
breweries often use gas chromatography to measure beer’s volatile components. They
also use HPLC to detect and identify carbs and other similar compounds. However,
when we brewed beer, we did not test it. We bottled, let it sit for two weeks
so the yeast could finish carbonating and fermenting the beer. Then we popped
open a few and shared them with our friends and family! And don’t forget beer
is indeed healthy in moderation!
And remember: “Beer is proof that God loves us and wants us
to be happy”
-Benjamin Franklin
Beer Brewing:
Tapping Chemistry – The Brewer’s Art:
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