>>If we think about the brewing process, we have four main ingredients: water, malt, hops,
and yeast. If we think about our malt, it comes from barley, and it gives us our main
constituents that we're going to use in the brewing process. It has carbohydrates, proteins,
and some lipids. Let's focus on the carbohydrates. If we think about carbohydrate, this is going
to be our main source for the sugar that's going to be converted into alcohol, ethanol.
What is a carbohydrate? Well, a carbohydrate, from its name, is a carbon hydrated, so it's
going to be a carbon with water added. So therefore, if we think about the structure,
we have a very simple formula: CnH2nOn. So most of our sugars are going to be C6H12O6.
Now let's look at the structure of our simple carbohydrates. If we look at our carbohydrate—such
as glucose, which is going to be our main carbohydrate—it's usually shown in a few
different forms. The first structure we see here is actually in a three-dimensional form
that organic chemists are very comfortable with, because it gives accurately what the
structure will look like energetically in solution. But notice that it is a straight
chain. The other structure that we're going to use quite often is the Fischer projection.
A Fischer projection doesn't give us the correct information as far as how the molecule will
look in three dimensions, but it gives us a very easy way to draw structure and tell
the difference between different sugars. Now, both of these are what we call acyclic. They
both have an aldehyde group, and we can see that they have five hydroxide groups. Every
carbon in the structure has at least one oxygen bond. Now, this is the acyclic form; we can
also have the cyclic form. If we look at the cyclic form, we have a possibility of the
rings coming around, so instead of being a straight chain we now are forming these rings.
Notice when we do this that we have one position that has two possibilities. So how this occurs
is that one of those alcohols comes around and attacks our carbonyl position. When it
attacks that carbon's initial position, that hydroxide that's formed can either go up or
can go down. So we can either end up with an alpha or a beta. This is going be important
as we look at the functionality of larger carbohydrates. So here we have simple glucose.
The other thing to realize about glucose is that all of the hydroxide groups are in the
most stable formation, and in fact, if we look at beta D-glucose, you'll see that all
of our hydroxide groups are in the equatorial plane, which is the most stable confirmation.
Now, these were monosaccharides. When we go to disaccharides, this is when we have two
sugars together. The one that we're most concerned with is maltose. If we look at maltose, we
have two glucose molecules. It differs from sucrose, another disaccharide you're probably
familiar with, because sucrose has a glucose and a fructose molecule. In maltose we have
two glucose molecules. The connection between these we refer to as as a 1,4 alpha linkage.
This 1,4 alpha linkage is the type of linkage we're going to see in amylose and amylopectin.
It is the type of linkage that can be easily divided or broken when we look at different
sugars. As we can see here, here's amylose. If we think about amylose the sugar, it is
a long-chain carbohydrate. So instead of a mono- or disaccharide here, we have lots of
glucose molecules connected and in amylose by 1,4 alpha linkages. These 1,4 alpha linkages
can be broken by amylase, the enzyme, into smaller carbohydrates. In malt what we're
looking for is maltose, so the amylose, the carbohydrate, is being converted with amylase,
the enzyme, into maltose. When we think about these structures, we also have amylopectin.
Amylose, as you can see here, is just a straight chain with all 1,4 alpha linkages. When we
look at amylopectin, we still have alpha-type linkages but we also have 1,6 connections
as well as 1,4. If we look at this structure here, you'll see that we have our normal 1,4
alpha linkages, but then up here we have a 1,6 alpha linkage. That's what makes amylopectin
a little bit different, and why we need not only alpha amylase, the enzyme, but also beta
amylase enzyme to break down—to fully break down—our carbohydrates. Now we talked mostly
about amylose and amylopectin with alpha linkages. That's because these are the ones that are
going to be broken down into fermentable sugars. The other structures we have is cellulose.
The malt has cellulose because we have cell walls and we have the plant structure. These
are actually useful in the filtering process and to settle out the mash at the end of the
mashing process. Notice that in cellulose, we don't have alpha linkages like we would
in starch or amylose, but we have a beta linkage. So we can see carbohydrates is where we're
going to get our sugar for the yeast to convert it into alcohol. We start with long-chain
carbohydrates and then, through enzymes, we break that down into smaller maltose and glucose
molecules. We start that in the malting process by activating those enzymes; then we're going
to finish that process during the mashing process, where we allow that enzyme and water
to work on those long carbohydrates to convert them into small disaccharides, maltose, and
monosaccharides, glucose.