Chemistry of Beer – Unit 1 – Overview of Brewing

By Brian Lemay 10 comments

>>Beer is one of the oldest beverages known
to man. We have tabulations, written documents, of brewing to the fourth century BC. If we
think about where it came from, it was probably an accident. All we needed was a sugar and
wild yeast, and the yeast could convert that sugar into alcohol, which of course early
man found enjoyable. To make beer as a fermented process we know that that goes back to 4000
BC where we have written documents that actually explain the process. Now, the beer that the
ancients knew was probably not the same beer that we drink today. It had similar components.
Most often it was barley, water, and yeast. But originally there were lots of different
spices that were used. It wasn’t until around the 700s A.D. that we got into using hops
in beer. This became the main definition of beer in 1516 with beer purity laws, which
stated that beer should consist of malted barley, hops, yeast, and water. The malted
barley gives us the sugar that is required to create ethanol plus it gives us the amino
acids and the lipids necessary for healthy yeast growth. The hops adds flavor components
to balance the sugary taste of the malt, but it also adds some essential oils that extends
the life of the beer. The yeast does the heavy lifting. It is there to convert sugar into
ethanol. The ethanol is important because it’s actually antibacterial, which means that
beer will last longer in many cases than the grain might have. And water. Water is often
overlooked, but it turns out that the water is essential to make sure that the yeast will
process the carbohydrates well. This means that we have to have the right pH, and we
have to have the right calcium and magnesium levels. Now the process is not overly difficult, but
there’s a series of steps. Let’s just look at it from the brewing standpoint, and then
we’ll talk about the chemistry of each of those steps. First, malting. We have to take
the barley and turn it into malt. We’re more or less getting it wet so it’ll start to germinate.
We don’t want to germinate fully, so therefore we stop that by kilning. Kilning just means
drying it out. So we’re going to dry out our malted barley, and with this we can also add
some other flavor components. We can heat it up a little bit to get a little caramelization,
or we can really heat it up to get a nice bitter chocolate type taste components. Once we’ve kilned it, we’re going to need
to actually grind it, and then we can start the mashing process. The mashing process is
going to add water so that we can start to hydrolyze our sugars, bringing the temperature
up so that we can get the optimum temperature range so that we can get the starch hydrolysis
enzymes, alpha-amylase and beta-amylase. Now at this point, we don’t want to boil it. It
turns out if we get too hot, we’ll actually deactivate those two enzymes, and we’ll be
left with lots of maltose in the solution and not the ethanol that we’re often looking
for in beer, giving the beer a very sweet flavor. So we leave it there for a while and
let those two enzymes really convert much of the starches into our small fermentationable
sugars. At that point now we’ve converted most of
those. We need to remove the wort, which is going to be our dissolved components, away
from our grain, our husks. Then we’re going to take that wort and bring it up to a boil.
When we bring that wort up to a boil, we’re a doing couple of things. First of all, we’re
making sure that we’re sterilizing the entire wort. This is important because when we introduce
our yeast, we want to make sure it’s the yeast we want and not a wild yeast or any other
bacteria. We also at this point will introduce hops. There’s several places where we can
introduce hops, but at the boil what we’ll be doing is extracting out of the hops the
alpha and beta acids that we need to add flavor components plus some other essential oils
that’ll help stabilize the beer. We then filter out the hops, and we bring that down to a
lower temperature so that we can have the yeast work on the process. Now what is the
yeast doing? The yeast is converting the sugars into ethanol. This is an important role. We
don’t have beer unless we have the ethanol. Now the process starts out as aerobic respiration
and is going to go to anaerobic respiration. It’s this anaerobic respiration that gets
us to the ethanol that is often associated with beer. Once the fermentation is done,
we have something that really resembles beer. But we’re going to let that age, sometimes
just a few days and other cases maybe months, so that we can get different components of
taste to either develop or to be inhibited. At that point we need to do second fermentation
because as we know, beer is carbonated. The second fermentation is focused less on creation
of ethanol and more on the creation of carbon dioxide. The carbon dioxide carbonates the
beer and gives us the mouth feel that we’re used to. If we think about historically, it
turns out the ethanol and the carbon dioxide were important for this to stay stable. The
lack of oxygen and the ethanol were both very important in making beer last longer. Then
we can package it, either bottles, cans, or kegs. This is the overall beer process. We’re
taking a grain, letting it start its germination, stopping it so that we can use enzymes to
convert carbohydrates into simple sugars. Those simple sugars are then converted into
ethanol, and then we finish that out by allowing the fermentation with the yeast to not only
create ethanol but also create carbon dioxide. This is what we know of as beer.


Gino Tarabotto

Mar 3, 2017, 1:17 pm Reply

Dear sir, I think the original purity law require only three ingredients hops, water and barley  yeast was allow later, please correct me if I am wrong, thank you.

Tom DiNapoli

Oct 10, 2017, 1:23 pm Reply

Gino, you are correct. Yeast was not officially discovered until Louis Pasteur. Yeast was added to the list later on.


Nov 11, 2017, 9:17 am Reply

Fermentationable? I believe he means fermentable. I tuned out after that… Michigan State University's beverage science program is one thousand times better than this; they actually offer it as a minor.

Sean Mulroy

Feb 2, 2018, 4:42 pm Reply

Reinheitsgebot is the brewing purity law that includes the four things he mentioned

Rum Ham

May 5, 2018, 3:26 pm Reply

2:36 delicious


May 5, 2018, 1:17 pm Reply

I'm pretty sure they just paid this dude to narrate the video in front of a library without have any idea of what he was reading.

Mr.A VR Freak

Oct 10, 2018, 5:38 pm Reply

Sounds like he read the VLB's – Technology Malting and Brewing

Peter Vautier

Jan 1, 2019, 9:21 am Reply

a lot of haters here, but I think the guy did a good job.

Benson Charles

Feb 2, 2019, 8:42 pm Reply

why this look like TED talk

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Mar 3, 2019, 9:31 am Reply

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