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Malt?  What Is this Malt?

Let’s talk about malt.  You might have heard the terms “malt whiskey” or “single malt” without thinking too much about what that really means.  Maybe you already know what that means.  Either way, I’m taking a bit of a deep dive to offer nuggets of wisdom for all.  We’re going headfirst into the malting process to understand what it brings to the table. 

First, let’s think about the grains we’re dealing with: barley, wheat, rye, and corn.  How do you take these whole grains from field to flask?  We need to start by understanding the structures of the grains themselves.  We’ll look at barley for our exploration.  It begins on a grass stalk on a farm:








In the case of barley, there is a two-row and six-row variety, named based on the arrangement of the grains on the head of the stalk.  Because of the extra space allowed for the growth of the kernels in the two-row version, the grains become bigger, leading to a higher starch content.  For reasons we’ll soon understand, this is often preferred for beer brewing and distillation.

So what’s going on inside these barley kernels?  As we’ll see, it’s pretty radical – or I should say radicle!  The barley grain, or seed, is packed full of everything needed to create a new plant.  There is the cotyledon, which is the part of the plant embryo (or germ) that will develop into the leaves.  This is also where the terms “dicot” and “monocot” come from.  Dicots contain two cotyledons and tend to have a bisected appearance, like beans and peas.  Our precious grains?  They are monocots.  Which means we have one part of the seed devoted to the future plant, and the rest packed with a starter energy pack.  But let’s get back to the radicle I mentioned first.  With the cotyledon being the leafy part of the plant in embryonic form, we also need the pre-plant root structure.  That’s the radicle.  And it will play a big role in the determination of when we intercede in the natural process – oh we’ll be playing God, but based on the nectar ultimately produced I think God would approve.

Let’s look at a diagram of the entire kernel (disregard the photoactivation pathway with Pfr - this is for lettuce):








The barley seed shown is a typical monocot.  It has a seed coat, a large endosperm area filled with starch, and an embryo (or germ).  With some seeds, there are barriers to the process of kicking off the growth cycle (germination) that allow a period of dormancy until special conditions are met.  Dormancy is evolution’s way of ensuring the plant doesn’t try to grow in the wrong time or place.  Barley, however, lacks any special dormancy...germination is initiated by water and reasonably warm temperature (34-36 degrees Fahrenheit at minimum for barley, but typically kicked off at elevated temperatures of around 60 degrees Fahrenheit in the presence of carefully controlled moisture levels for the malting process for beer and whiskey). 

Bear with me, we’re about to get very chemical, but it’s all in the name of the fascinating science of creating and managing enzymes and sugar for optimal distillation.  You’re about to learn where the starch meets the sugar, and who introduces them.

The seed takes up water from the environment in the process known as imbibition.  The water passes through the embryo, picking up the germination signal: the hormone Gibberellic Acid. The water moves the hormone from the embryo to the aleurone layer of the endosperm (the big area where all the starch is stored, like little meal kits just waiting for a hungry embryo).  This layer of cells stores much protein and is the "brown" of "brown rice."  When cooked, this protein-rich layer gives brown rice its chewiness.  This is another aspect that differentiates the two-row from the six-row barley – the smaller six-row seeds have a higher ratio of protein to starch than the two-row, lowering the overall efficiency of the alcohol production process while also adding a heavier character through the added protein.  Therefore, the two-row barley is more popular to brewers and distillers.

The water activates hydrolysis enzymes that degrade the storage protein into amino acids.  The gibberellic acid activates the DNA gene coding for the enzyme amylase (remember this one, it’s an important enzyme) in the aleurone cells and begins the amylase manufacturing process via ribosomes.  The amino acids formed when the water degraded the storage protein are then used to ship, sort, package, and export the amylase through the cell membrane (in packages called vesicles through a process called exocytosis).  The amylase is thus dumped into the endosperm interior. 


Here’s where the magic happens!  The amylase is now surrounded by those meal kits we call starch (which is a polymer form of sugar that needs to be broken down to truly become sugar).  The amylase begins catalyzing the hydrolysis reaction that turns starch into sugar.  Here’s an example of what that reaction looks like, using the starch amylose as the base material:











The sugar happens to be maltose, which is transported to the embryo.  The sugar fuels respiration in the embryo so it can grow.  The radicle protrudes from the seed coat (thinking it’s about to become the root of a new barley plant), and germination is accomplished in barley. 


By then raising the temperature to the 120 degree Fahrenheit range, the water is driven off, and germination is halted.  This results in barley grains containing an optimal mix of sugar (to transform into alcohol through fermentation), starch (to further convert to sugars through the catalytic activity of amylase), and the enzyme amylase itself, which can catalyze sugar production in other grains utilized in the distillation process (the degree to which it can accomplish this is known as its diastatic power).

All of this encompasses the malting process.  For barley, the malting process is necessary to achieve a grain capable of being utilized for brewing or distillation.  For other grains, malting might not be critical.  Corn, for instance, can be malted but contains enough sugars naturally that malting is typically not utilized.  Rye is an interesting grain that can create unique aspects to the whiskey in both malted and pure forms.  It is therefore worth noting in rye whiskeys whether or not the term malting is associated with the product.  And wheat is typically utilized in an unmalted form.  One of the powers a malt brings to the table is the catalyzation effect it can create in the rest of the mash.  I’ve heard stories from distillers who talk about adding malted rye to a mash and seeing in short order a still of oatmeal turn to a still of water, such is the transformative power of the malt enzymes.

If a whiskey is a barley variety – as is the case of Scotch whisky - malting is inherent to the process.  In fact, the peaty flavor associated with certain Scotch whiskies comes from the peat fuel utilized to heat the grain to a temperature high enough to halt the germination process.  If it is a bourbon or rye, however, malt might instead refer to either an amount of barley utilized in the mash bill or an amount of malted rye as part of the mix that trades the spicy raw rye flavor for the starch-converting and sweetening power of a malted rye.  And when a good bourbon can hang on the balance of spicy and sweet, a carefully malted rye could become a devastating secret weapon.

Hopefully now you know a little bit more about what “malt” means and how it influences the whiskey you drink.  Having armed you with knowledge, I now challenge you to go forth and conquer the tastings of many a fine rye and Scotch whisky.  Whereas before, every drink was an indulgence, now every drink can become a scientific experience.

I want to specifically thank Ross Koning for his contribution to this article.  Some of his work I have included verbatim, and having obtained his permission to do so, I hope he enjoys the celebration of biology that it inspires within those that absorb its contents.  Thank you, Ross! (5-25-2019).

Barley Seed (2).jpg
Amylose Reaction.png
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