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Why Beer Gets "Skunked" and Other Scent Science
Episode 6 • 29th April 2024 • Respecting the Beer • McFleshman's Brewing Co
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Gary, Bobby, and Allison explore the complex chemistry of beer's aroma. We figure out why beer gets skunked, the effects of hop and yeast, and why glassware matters for a great beer experience.

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--

CREDITS

Hosts:

Bobby Fleshman

Allison McCoy-Fleshman

Gary Ardnt

Music by Sarah Lynn Huss

Recorded & Produced by David Kalsow

Brought to you by McFleshman's Brewing Co

--

Topics in this episode:

Introduction to Beer Smell

The Role of Barley and Malt

Discovering Hops

Terpenes and Aroma

Importance of Glassware for Beer

Transcripts

Gary Arndt:

Hello everyone.

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And welcome to another episode

of Respecting the Beer.

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My name is Gary Arndt and with me

again, as usual as Alison McCoy and

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Bobby Fleshman Today or in our last

episode, we talked about sight.

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One of the senses that we use to

appreciate beer, how a beer looks it's

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foam, it's carbonation, everything else.

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This episode, we want to talk about smell.

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Smell and taste are closely

related with each other.

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They're kind of interlinked

in a lot of ways.

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Something smells bad and may not

taste very good and vice versa.

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So let me start out with the big question.

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Why does beer smell and where

does the aroma come from?

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Bobby Fleshman: Yeah, last time I

got in the weeds about how, where

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these colors come from and, and

it was related to the malt and the

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barley and the proteins and so on.

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And the, the main flavors of

beer are coming from the sugars

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that are derived from the starch

inside of those, those grains.

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The proteins give you some

mouth feel in the end, which

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is separate from, from flavor.

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then you're getting some aromas that

are driving from like sulfur derived

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compounds like dimethyl sulfide.

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And you guys might recognize that.

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If you open a can of, of raw green

beans or corn, you're actually

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getting that in your, in your malts.

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And that's giving you some, some

dimensionality to the finished beer.

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Allison's giving me a cross.

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Allison McCoy Fleshman: Because

you're going down directly to

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green bean juice when you really

should be talking about hops.

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Bobby Fleshman: Well, yeah, I'm starting

with barley and then I'm moving on.

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I just didn't want to say

that I didn't want to say that

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barley just gives you sugar.

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There's there's a lot more to the story.

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There there are amino acids that

contribute to ester production

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and esters are sort of fruity

aromas that people will associate

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with break baking in the kitchen.

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Dark fruits.

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There's a lot of that going on and it's

being derived from that malting process.

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So that's coming from the

Malt side of things Allison

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points out that at some point.

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a few hundred years ago, hops were

discovered as a nice balance to the

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sweetness in beer and preservative

property are, I think the botanist's

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name was Hildegard von Dingen.

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Now

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Allison McCoy Fleshman: I

can say a hundred years ago,

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Bobby Fleshman: a couple

of hundred years ago,

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Allison McCoy Fleshman:

multiply that by a couple more.

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Gary Arndt: That's almost

a thousand years ago.

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Allison McCoy Fleshman: Exactly.

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Bobby Fleshman: Oh geez.

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So it, but it's been adopted widely

though in the brewing industry as is

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almost the only solely the, the, spice by

which we balance the sweetness in beer.

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But there you have it.

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So in these hops, you have what are

known as hard, the hops look like little

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pine cones, little green pine cones.

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And inside of them, you're going to

find hard and soft resins and the resins

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located inside these little yellow glands.

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You can take these hops and

pick them off the vine and open

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them up, see little glands.

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And you just take that and you roll

that, that yellow gland in your hand.

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You'll smell these aromas come off of it.

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Allison McCoy Fleshman:

Hops are very fragrant.

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Bobby Fleshman: Yeah.

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It's kind of like cutting your lawn.

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You can imagine that that's

actually, some of the terpenes are

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shared with hops across all sorts

of fruits and vegetables and, and,

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Allison McCoy Fleshman:

You said the word terpene.

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Let's chat for a second.

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Bobby Fleshman: Yeah.

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This is where I have to nod to the expert.

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Allison McCoy Fleshman: So the terpenes

are these oils that are in so many

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different plants but the, the reason

that you get grass stains is because

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the terpenes in the grass are an oil.

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And so just like you can't really wash

off your oil off your hands without some

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sort of water or without some sort of

soap or surfactant or something the oils

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that are in grass stain your clothes

and you can't get them out because,

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well, oil likes to stick to fabric.

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But those oils are really what

give hops their kind of superpower.

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But the kicker is that the oils don't

really mix with water that well.

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So the hops have to go through several

chemical reactions in order to get them

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to stay in the water and that's what

makes hops one of the hardest things I

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think in the brewing industry to handle

because they're quite finicky when it

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comes to the chemistry that they can do.

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Bobby Fleshman: Right.

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I did misspeak.

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Terpenes are found

throughout the hop plant.

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The, that resin is where you get these,

these bittering compounds that I spoke

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about, but, Allison, you could speak

on that there with these terpenes, you

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have some that are, she'll, she'll give

you the, okay, I'm going to give her,

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she's going to expand a little more.

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Allison McCoy Fleshman: Oh my God.

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Okay.

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So Gary, you asked the question

of what gives a bearded smell.

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Well the kicker is in order to smell

anything, a little bitty molecule has

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to leave the thing and come to your nose

and go into you somehow and trigger your

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brain to think, oh, that's that smell.

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And hopefully it triggers a memory and

it's a lovely memory and you're happy.

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But in some cases it's not so happy,

especially with not so great odors.

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But the hops have, they have these

oils and those are volatile compounds.

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And anytime you've walked past a nail

salon, like in the grocery store or

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whatever and you smell that acetone,

acetone is incredibly volatile,

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that's the nail polish remover.

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These are kind of the same.

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They do not, those molecules do

not want to stay, in the beer.

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And so they are going to, what we call,

be aromatic, they are going to float

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away from the beer and come to your nose.

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And that's really the

first, so you see the beer.

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And you're about to taste it, but

as you bring it closer to your nose,

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those molecules are going to start

to escape and come into your nose.

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And then you're going to smell them.

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Hops contribute more of those kinds

of molecules than the malts do.

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So if there's more hops in the beer,

you're going to get more of that

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experience before you even take a sip

because those molecules are coming to you.

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Bobby Fleshman: And getting out,

getting out of my wheelhouse, I

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can say that there's a difference

between tasting wine and beer.

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And that you should, if your, if

your goal is to taste the beer, you

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should actually swallow it and then,

and then breathe back out to get the,

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the retronasal, attribute where I

don't think that's required in wine.

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I think you can get most of that

inside of your mouth and you don't

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have to consume it to, to get it.

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I think the CO2 is part of

that is why that's true.

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It's evolving those aromas back.

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out of your system

through your nasal cavity.

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Gary Arndt: I know when someone drinks

wine, you see them, you know, they

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swirl it around and they smell it and

there's, Oh, it's, you know, you know,

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they have this, description for it.

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You seldom see people

drink beer that way, right?

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Maybe because it's carbonated.

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You're not going to,

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Allison McCoy Fleshman: that's true.

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The carbon dioxide is going to be

bringing those molecules to you much

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faster because the carbon dioxide

also doesn't want to stay in the,

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Gary Arndt: but I've

also noted what you said.

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the double IPA that you guys

make, 547 has a very strong aroma.

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That's one of the first things

I ever noticed about it.

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And I don't notice that

on most beers at all.

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Yeah.

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it, you know, it has this very strong

orange peel scent that I noticed.

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citronol,

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Allison McCoy Fleshman: I

believe is what that is.

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Bobby Fleshman: Citronol.

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Yeah.

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Brought about by a few different

hops that are high in that oil.

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Mm hmm.

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Gary Arndt: But I've never noticed a

wine that had that strong of an aroma.

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Whereas I don't know if it's just a

unique thing with that, but I've just

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Like nothing, you know, you, you get

hints of things in wine, but with

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certain beers, it's very noticeable.

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Yeah,

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Bobby Fleshman: the, the

double IPA is very American.

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It's, it's a very American style.

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It's nuanced.

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It can be nuanced and it should

be, it should be balanced.

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It's never nuanced.

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So

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Allison McCoy Fleshman: I just

had to do a quick Google search.

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I just looked up the chemical structure

of vanillin, which is the molecule

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that gives you the vanilla flavor.

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And I know that there's a lot of, at

least in chardonnays and stuff, there's

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a lot of vanilla character in wines.

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I'm looking to Gary to

be like, is that true?

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I don't even know.

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Bobby Fleshman: You barrel

derived mostly for that.

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Yeah.

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Allison McCoy Fleshman: So

the vanillin molecule has many

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more, what we call polar groups.

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And so chemists like to use the

phrase, like dissolves, like, so

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if, if the two molecules are more

similar they're going to mix better

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and this is actually true with humans.

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You can anthropomorphize

molecules really well.

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So the more things you have in common

with someone else, more likely you're

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going to hang out with them longer.

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You have nothing in common, you're

like, nope, going to go somewhere else.

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So the wine compounds, I think, have

many more similarities to the water that

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they're in or the wine that they're in,

so they're going to stay there longer.

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So I'm guessing that the Sommelier

folks are swirling their wines to kind

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of coke some of those molecules to

come to their nose, whereas the hops

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are like, I'm not like water at all.

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And they just come up freely.

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Bobby Fleshman: And you'll often pour a

wine through a breather to open it, right?

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Allison McCoy Fleshman: That makes sense.

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Yeah.

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Bobby Fleshman: Yeah.

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Before you drink it.

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Allison McCoy Fleshman: so Gary, you

mentioned our five, four, seven, one of

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the things, I think we have it written

on the can too, is please drink me fresh.

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folks will store our 547, which

is a bad idea because the longer

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it stays in the can, the more of

those hop volatile molecules have

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escaped into the little headspace.

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Bobby Fleshman: We have about 10 mils

of space in each can for them to escape.

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Allison McCoy Fleshman: Yeah.

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And so as soon as you

crack it open, it's like.

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Bobby Fleshman: It smells great!

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Allison McCoy Fleshman: Instantly

and then it's all gone, but

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it's still not in the beer.

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And so you want to drink those

hoppy beers as fast as well.

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Not as fast in one sitting, but you

want to make sure that they don't,

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they don't have a long shelf life.

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Bobby Fleshman: And no shaking the can up.

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Doesn't re introduce the oils.

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Allison McCoy Fleshman: Don't do that.

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Gary Arndt: Not like that.

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This freshness.

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I was here once and I remember, there

was discussion of like, you were going

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to submit it for an award and some of

the people that work here were like,

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They were actually going to take a

road trip to take a batch of it and

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drive it as quickly as possible.

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Allison McCoy Fleshman: To Colorado.

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Yeah.

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Bobby Fleshman: Yeah.

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And keep a webcam moving as they went.

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Yeah.

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Gary Arndt: And I was always kind

of, again, I'm always kind of

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skeptical of a lot of these things.

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Like, yeah, it really

doesn't make a difference.

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It's just sort of a marketing thing,

but you're saying, no, it really does.

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Even if it's in a can, that's

going to make a huge difference.

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If it's just canned versus something

that's been sitting around just

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Allison McCoy Fleshman:

for, well, more for beers.

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Like you said, our five, four,

seven is the one that's like.

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You don't get that with

any of the other beers.

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That's the one that's the most

susceptible to that aging.

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The others I think would be fine.

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Bobby Fleshman: Correlation is not

causation, but to Gary's point, the

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winners of these competitions generally

are within a 150 miles of the competition.

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Now that that's because Denver

has a lot of good breweries.

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yes, that's part of it.

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Allison McCoy Fleshman: But it's also

because chemistry still holds and

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those molecules don't like each other.

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So they escape.

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Bobby Fleshman: So you gotta

get your beer there quick.

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Gary Arndt: Okay.

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Would it be possible to fly it?

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Or was it with the change in pressure?

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Bobby Fleshman: Oh no,

there's a whole thing.

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I never thought of that.

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Oh my god.

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Never thought of that.

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Allison McCoy Fleshman:

I have so many thoughts.

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Well, this is one of the good things about

the fact that our, in our brewery, we've

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got it set up to where the kegs and the

casks are located immediately behind.

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Where we pull them from.

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So where the taps are at our house, we

also have a tap system, but we've got

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our kegs are in the, the, the freezers

and the kegs are in the basement

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and then we've got it drilled up.

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There's a hole through our living

room floor and then we've got

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a nice little tap system there.

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But the pressure differential

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Gary Arndt: You have taps in your house?

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Bobby Fleshman: Oh, they're

really a Belgian tower.

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I got from a museum and it was, it's

not a brag that I spent the money.

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I just found this thing.

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Gary Arndt: That's hardcore.

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Allison McCoy Fleshman:

You've got it separated.

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We've got an ale cooler and

a logger cooler as well.

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Yeah.

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But the, the, the, the, the pressure

differential that you have from

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the basement to the first floor

makes it hellaciously hard to

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pour the beers because of that

off gassing that it goes through.

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Bobby Fleshman: Well, since I

built that, I've learned a lot.

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That's been 12 years or

whatever since I built that.

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And now I've learned a lot more

about partial pressures, which we can

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Allison McCoy Fleshman: Not

go into that later date.

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Don't give away all the fun stuff.

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Gary Arndt: In a previous

episode, when we talked about

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color, we talked about glassware.

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And I also remember having this discussion

where I was skeptical that glassware

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could have anything to do with aroma.

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And so you literally did a test where

you poured, I think it was the 547

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double IPA in two different glasses.

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Allison McCoy Fleshman:

Were you blindfolded?

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Gary Arndt: No, but it was,

I could tell the difference.

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I think one was like a tulip

shaped glass and one was a

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more open mouth glass that it.

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Concentrated the aroma for lack of a

better word in that it had a small the,

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in the glass that had a smaller opening.

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Is that something that, I mean, how, how,

how deep into the weeds are you going

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to go into when selecting glassware?

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I mean, you're also selecting aroma

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Bobby Fleshman: okay, when you go

to Belgium, you'll see that every

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brewer has their own glass, and you

can't have their beer at any bar.

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Unless one of those glasses are available.

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And I think that that's because they have

been meticulously designed, partially

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just marketing and the way they look,

but partially because they are meant to

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enhance the aroma and the whole experience

of that, of their, of their beer.

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And I'd like to see more of that.

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I like to see us, I mentioned us

designing our own glass at some point.

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I'd like to do more of that.

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It, the, the trick is we, we cover

so a gamut of styles here and

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it's hard for us to pick one, but

yeah, it's, it plays into that.

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We have to usually make one

work for about three styles.

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Yeah.

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We can't have one for every single beer.

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Allison McCoy Fleshman: During

the pandemic we switched over to

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single use plastic cups because.

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in pandemic times, we

did different things.

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Anyway, so when we went back to

glassware, we decided to just reduce

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it down to just four glasses that we

could get to match as much as possible

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and optimize the glassware to all

the different styles that we serve.

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But one of them is our Hildegard Pilsner.

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So the Hildy, she's a, Czech

Pilsner gorgeous glass.

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that's like a really tall one so you can

see how clear it is it's got a really

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nice foam on the top, but Hildy has really

subtle hop aromas and Bobby figured out

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that the more traditional style would be

this bigger, wide open mouth dimple mug.

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And I think the experience of the beer

is so much different, even though it is

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to style more in line with the checks

to do the bigger, thick dimple mug.

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That's got a really wide mouth because

of the subtle hop aromas in the Hildi.

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I really like her having the

more closed concentrated.

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Hop glass.

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Bobby Fleshman: Which was kind of

confusing because that enhances the,

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the hop aroma, which I wouldn't expect

from Allison to be into as much.

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Allison McCoy Fleshman:

Well, I, well, it, I mean,

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Bobby Fleshman: yep.

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Allison McCoy Fleshman:

I'm being objective here.

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You know.

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That's true.

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Gary asked, does the glass matter?

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It does.

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I was like, I think it does.

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Bobby Fleshman: I wanted to

get to one little anecdote

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about glassware very quickly.

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Miller Lite was created, When was that?

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In the late 60s, early 70s, it

launched the light beer revolution.

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True.

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Gary Arndt: I think I

want to say late 70s.

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Bobby Fleshman: It was late 70s.

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Okay.

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So, so Miller light was created, but it

couldn't be created and packaged in a

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light glass, a clear glass because that

would have gone skunky and then we can

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go into the science as to why Sunstriking

a beer makes it smell like a skunk but

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needless to say the ingredient that...

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it's a hop acid basically that turns into

that same aroma you get from a skunk from

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a skunk, and, it happens in the sunlight.

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The only way they were able to do

that in mass at the scale they were,

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they had to invent a new hop acid

and they had the patent on that acid.

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They created it synthetically.

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they, they reduced an existing one by

adding protons and boom, they created

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what was a more of a, it was a more

stable hop acid and it didn't go skunky.

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B.

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As a side effect, it made magnificent

foam, and so they named it the

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Champagne of Beer and so on and so on.

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Allison McCoy Fleshman: Is

that where that came from?

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Bobby Fleshman: It was not planned, but as

they made this want to solve one problem,

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they solved two, or they created another

benefit, and they led the charge in the

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light beer revolution for a good while,

and they, they named it L I T E, and I

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think that was from the very beginning.

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But now you've seen many other brewers

step in and use the same sort of hop

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ingredient, but they, but they didn't have

access to that for a long time, if ever.

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So they had brown glass

for their light beers.

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So they were the only ones with

that presentation because they had

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the monopoly on that chemistry.

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Gary Arndt: When you

say they added protons.

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Bobby Fleshman: Yes, it's, it's

called reducing in chemistry.

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So you just hydrogen?

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Yeah, yeah, yeah.

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Sorry.

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Yeah.

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I am a physicist, so

sometimes I slip into that.

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Allison McCoy Fleshman: Oh no,

chemists use that too, but technically

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we would call it hydronium as well.

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Bobby Fleshman: Hydronium.

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Let's go with that.

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Sounds even better.

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No, that's H3O plus.

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Gary Arndt: Cause I'm also thinking,

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Bobby Fleshman: what

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Gary Arndt: did they transmute to

a different element or something,

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Bobby Fleshman: right?

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:

That's high level.

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:

So they added four hydrogen

atoms to, an ISO alpha acid.

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Which we can talk a lot about

late in future episodes, but acid

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is what makes the beer bitter.

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And they made it stable.

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And then there, there've been

various other ones created since

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:

then, but that was the one that

really launched Miller Lite.

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Allison McCoy Fleshman: You know,

there's a picture of the, oh,

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it's, it's one of the primary,

advertisements of Miller High Life.

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There's this 1960s woman and

she's looks like she's the

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:

housewife and she's so excited.

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And she's like, Miller High Life,

you have the champagne of beers.

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I'd really like to think that

she's the scientist behind it all.

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And she's like, I had developed

this isomerized alpha acid

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and no one else knows.

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And it's patented.

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Yay.

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Just saying that's how I'm going to

interpret that picture from here on out.

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Bobby Fleshman: Right.

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We can't finish this episode, Gary,

without talking about yeast, can we?

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There's, they, they give aromas too.

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:

Bananas!

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:

Yeah.

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:

It's gotta be about yeast as

much as it does hops and malt.

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Allison McCoy Fleshman: Let's

talk about the hefeweizen.

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Just, that's

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Bobby Fleshman: the extreme.

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That's one of the extremes.

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Hefeweizen tastes, or smells and

tastes like, bananas and clove.

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Sometimes bubblegum, and all that

stuff is derived from some, some

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Allison McCoy Fleshman: So no bananas

were used in the making of this.

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No,

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Bobby Fleshman: but you can put

strawberry into it and it's awesome.

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:

So that, that's just a contrast that we've

come to love, a complimentary flavor.

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So, yeah, that, that's one extreme

and then you get cleaner ones.

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Lager yeast tend to be cleaner, although

they kick off some sulfur and, and

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:

I think that's quintessential for a

good lager at a very, very low level.

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:

Allison McCoy Fleshman: When you say the

yeast are cleaner, does that allude to

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:

the fact that other yeasts are dirtier?

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:

Bobby Fleshman: They, yeah.

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:

They don't make as many of those

fermentation derived aromas and

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:

flavors as do, say, a Belgian yeast,

which you can put in the same box

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:

as that, a half a bite of yeast.

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:

And those are going

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:

Allison McCoy Fleshman: to make

a lot more esters, aren't they?

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:

Bobby Fleshman: Yeah.

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:

Phenols is another one.

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And sometimes we'll say a phenol in the

extreme case is plasticky or bandaid like.

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I was about

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:

Allison McCoy Fleshman: to say esters.

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So

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Bobby Fleshman: you want to stay away from

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:

Allison McCoy Fleshman:

that to some extent.

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:

Chain up a bunch of ester molecules,

you're going to get polyester, which

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:

I'm sure many of you know what that is.

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:

Bobby Fleshman: We're not

making polyester in our beers.

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:

That's not yet a thing.

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:

Yeah.

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But then in the English, in the English,

yeast are kind of in the middle there.

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They have some really good, I would

say complimentary flavors esters that

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they produce that plays well with

the malts that are made in England.

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Some of the best malts in the world

are made in England they've discovered

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their best yeast that work with those.

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Gary Arndt: All right.

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Well, I think that concludes another

episode of Respecting the Beer.

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Join us next week for another episode.

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And until then, you can go to our Patreon

page or our Facebook group, the links

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to which can be found in the show notes.

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