Beer Brain

Off-Flavor Analysis

With my recent endeavor to become a Certified Beer Server (the first certification level of the Cicerone Program), part of the study before the exam was to know and analyze off flavors in beer. Now we’ve all had beers that we didn’t enjoy. Maybe just a “Yuck!” or “Gross!” Besides crying about it, do we know exactly what we didn’t like about them when we tried them? Was it a skunky beer? Was it contaminated in some way? Could it be a brewing mistake? Or was it simply just a weird flavor about the beer that you didn’t like? There are many things that can affect the flavor of the beer, and understanding the different off-flavors can help you determine what should be present and what shouldn’t.

My study partner and I decided to put together a few experiments to help hone in our off-flavor senses. We also added a few raw spices in the testing samples to improve our senses of those as well. 

Acetaldehyde:

Tastes and smells like green apples. For this one, we just sliced up a fresh apple and sipped a light commercial beer along with eating the apples. It’s very contrasting to the normal flavor of the beer, so it’s pretty easy to pick up. If your beer’s profile doesn’t have this flavor listed, then it’s not supposed to be there.

Alcoholic:

This flavor and aroma is exactly how it sounds. It can be compared to an acetone, or paint thinner, and can sometimes be characterized as “boozy.”  You know that warm fuzzy feeling after you’ve taken a shot of Tequila? Yeah, this is the same thing.

Astringent:

A harsh flavor that can make your face pucker. Can leave a dry or a grainy aftertaste. I tend to think of rubbing alcohol or a soapy flavor or smell with this one.

Diacetyl:

Buttery or toffee aroma and flavor. Some people say there can be a “slickness” in the mouth. We compared two glasses of a light commercial beer, one with a couple drops of melted “I Can’t Believe it’s Not Butter!”

DMS (Dimethyl Sulfide):

Creamed corn or canned vegetables; reminiscent of Thanksgiving dinner, but in a bad way.  In some rare cases it can also resemble a shellfish or oyster-type smell (eeeewww). For this experiment we just cracked open a can of creamed corn, and put a few drops into a glass of light beer and compared it to one that hadn’t been contaminated. We, unfortunately, didn’t have any spare shellfish to sniff.

Estery:

Fruity!  Citrus, flowery……

Grassy:

Does your beer taste like a leafy green salad? This aroma resembles the smell of fresh cut grass; We obtained some from the lawn.

Metallic:

Have you ever pricked or cut your finger and started sucking on the wound so you don’t bleed all over the place. That tinny/iron taste that blood has is a good example. Since we didn’t want to go that far, we decided to get some spare pennies, and soak them in water. Yep, smelled like wet money!

Oxidized:
Mmm…wet cardboard! That what oxidized beer may smell like. Also, can be characterized as papery or stale. For this one we did the obvious, soaked a piece of cardboard.

Phenolic:

I love spicy food and even spicy beer (when it’s supposed to be). When it’s not, this off flavor can be compared to a peppery or smoky flavor. Sometimes it even comes off as “medicinal,” or band-aid like. Yuck.

Solvent:

Acetone or paint thinner. We decided against the idea of sniffing paint thinner for this experiment, but we all know what it smells like.

Sour/Acid:

Vinegar and tart are the most common ways to describe this type of flavor/smell. Just picture drinking the beer and then puckering your face. We dumped some vinegar and lemon juice in a glass to taste and smell. Pucker face away…….

Sulfur:

We all did experiments with sulfur in grade school science and remember how it smelled: like rotten eggs. Can also be described as sewer or burning matches. Since no one really keeps eggs in their fridge long enough for them to become rotten, we just burned a couple of matches.

Yeasty:

Bready. My study partner happened to have some bread yeast in her cabinets that helped us isolate this flavor/smell.

The Evil Skunk Beer

We have all had a skunked beer probably way more times that we ever should. It’s so common because it can happen so quickly; in as little as a few minutes. It happens when beer is exposed to light, and is the reason why many brewers prefer to use brown bottles, or even cans to prevent this from happening. When light is exposed to a beer, it reacts with the hops to create a skunk-like flavor or smell. Therefore, skunking tends to be worse in beers with more hops.

For this experiment we grabbed two Heineken Lights, and put one out in the sun all day (then chilled it right before serving), and kept the other in a closed refrigerator away from any light. We poured them both into individual glasses, and tasted the “non-skunked” one first.  When comparing the two, only a slight skunky smell and flavor was detected in the sun-baked beer. For the most part, they tasted relatively the same. Heineken is pretty much known for its “skunky” flavor and it has become an acceptable identity for the beer. Given that they are bottled in light green bottles that provide little protection from light, it’s possible that they had already been skunked at some point. It would be interesting to do this experiment with a hoppier beer that’s in a darker bottle to really compare skunk vs. non-skunk.

Summary:

These expiriments were pretty simple, but very helpful in isolating these common off flavors.

However, really understanding off-flavors in beer also requires a more in-depth knowledge about beer styles. Some specific flavors may be acceptable in one style of beer but not in another. For example, the “buttery” flavor of Diacetyl may be acceptable in a beer such as a Bohemian Pilsener, but not acceptable in a Traditional Bock. It’s common for ales have the presence of a fruity (esthery) smell or flavor but it’s important to know when it’s appropriate for the style.

These off-flavors can be one of many culprits. It can be contamination while brewing, storing, or bottling. Possibly even from using dirty equipment that wasn’t cleaned entirely. They can happen with bad transporting or storage practices. But before we go and generalize every beer we don’t like as a “bad” beer, we need to do the research. Know the beer style, and know the beer profile; and know that sensory evaluation is left to human interpretation that differs from one beer drinker to the next.