[lupulus]

What does clean beer/ fermentation mean to you?

Some seem to use "clean" as an absolute descriptor. Eg, lager yeasts are clean, as long as they don't have sulfur dioxide or off aromas; ale yeasts are not clean because they produce esters by design; some more than others.

Some seem to use "clean" as relative descriptor. Eg, a yeast is clean as long as it produces the expected flavors and aromas for the style and no off flavors.
For example, a Kölsch yeast can be clean and more estery than a lager yeast at the same time.

For some, it may be something else.

What's a clean beer/ fermentation to you?

For me? I don't use the word because I am not sure of what it means as a descriptor.

"It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts." - Sherlock Holmes (A. Conan Doyle)

[BrewBama]

One of the problems I believe we have as homebrewers is settling on common terminology definitions.

The term ‘efficiency’ comes quickly to mind. It can mean different things to different brewers. Even the more narrow ‘Brewhaus efficiency’ can create confusion when the formula to calculate it is questioned.

To me, ‘clean yeast’ is absence of yeast flavor and/or aroma contribution to include esters, sulfur, etc. Bry-97 is clean to me. Windor contributes flavor. W34/70 produces sulfur during fermentation. NovaLager doesn’t.

[ynotbrusum]

Inherent language limitations are difficult, but we muddle onward with descriptors.  I use "clean" in the context of a beer exhibiting little to none yeast-derived flavors or aromas; typically, it is in the context of lager beers, but some ales are made with ale yeasts that exhibit an almost lager-like flavor and aroma, so they can be included in the "clean" description category, too.  Kolsch and BRY-97 and similar yeasts are what I would consider to be clean.  I am sure we can dicker over the level of precision in the word choice of "clean", but that is true of anything subjective and used outside of an objective testing environment.

Good question, though.  Cheers.

[Andy Farke]

To me, "clean" means that you don't know the yeast is there--all you get is the malt and hop character. No fruitiness, no phenols, no sulfur, or any of the other things that yeast might throw off. It is somewhat strain dependent (e.g., a Belgian ale vs. a Chico strain), but also technique dependent (e.g., a lager yeast fermented at 50 degrees versus 75 degrees).


My "stereotype" of a clean yeast strain would be Diamond Lager fermented at 50 degrees and given the appropriate amount of lagering afterwards. A non-clean example would be Belgian Abbaye fermented at 80 degrees.

[lupulus]

To me, "clean" means that you don't know the yeast is there--all you get is the malt and hop character. No fruitiness, no phenols, no sulfur, or any of the other things that yeast might throw off. It is somewhat strain dependent (e.g., a Belgian ale vs. a Chico strain), but also technique dependent (e.g., a lager yeast fermented at 50 degrees versus 75 degrees).


My "stereotype" of a clean yeast strain would be Diamond Lager fermented at 50 degrees and given the appropriate amount of lagering afterwards. A non-clean example would be Belgian Abbaye fermented at 80 degrees.

By your definition, no ale yeast is clean, right?
Because, all of them will show a yeast character vs. a lager yeast.
Not disagreeing but confirming :-)

"It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts." - Sherlock Holmes (A. Conan Doyle)

[Andy Farke]

To me, "clean" means that you don't know the yeast is there--all you get is the malt and hop character. No fruitiness, no phenols, no sulfur, or any of the other things that yeast might throw off. It is somewhat strain dependent (e.g., a Belgian ale vs. a Chico strain), but also technique dependent (e.g., a lager yeast fermented at 50 degrees versus 75 degrees).

My "stereotype" of a clean yeast strain would be Diamond Lager fermented at 50 degrees and given the appropriate amount of lagering afterwards. A non-clean example would be Belgian Abbaye fermented at 80 degrees.

By your definition, no ale yeast is clean, right?
Because, all of them will show a yeast character vs. a lager yeast.
Not disagreeing but confirming :-)


I think there is a big degree of subjectivity there. I do find some ale yeasts to be quite clean in the right conditions and recipe. My palate probably isn't the most refined, of course, but I find BRY-97 in an American IPA fermented at 66 degrees to be very clean.


Of course, I think there are far more clean lager strains than clean ale strains!

[erockrph]

To me, "clean" means that you don't know the yeast is there--all you get is the malt and hop character. No fruitiness, no phenols, no sulfur, or any of the other things that yeast might throw off. It is somewhat strain dependent (e.g., a Belgian ale vs. a Chico strain), but also technique dependent (e.g., a lager yeast fermented at 50 degrees versus 75 degrees).

My "stereotype" of a clean yeast strain would be Diamond Lager fermented at 50 degrees and given the appropriate amount of lagering afterwards. A non-clean example would be Belgian Abbaye fermented at 80 degrees.

By your definition, no ale yeast is clean, right?
Because, all of them will show a yeast character vs. a lager yeast.
Not disagreeing but confirming :-)


I think there is a big degree of subjectivity there. I do find some ale yeasts to be quite clean in the right conditions and recipe. My palate probably isn't the most refined, of course, but I find BRY-97 in an American IPA fermented at 66 degrees to be very clean.


Of course, I think there are far more clean lager strains than clean ale strains!

I can't speak for Andy, but since the rabbit hole opened up I'm going to jump in...

How are we defining a lager yeast versus an ale yeast? Even now that the yeast genome has been sequenced, there is still a lot of gray area here. Yeasts that have long been considered (and are still marketed as) lager yeasts have mapped as ale yeasts. If they produce beer that tastes like one would expect a lager to taste, is it now no longer a lager just because of the genome?

Is it the presence of specific compounds? Is it only if they appear above a certain threshold?

To me, it is the overall impression of the beer. I have brewed my pilsner recipe using WY1762 (Abby II - widely assumed to be the Rochefort strain) a couple of times now. When I pitch at my usual lager rates, ferment cold, then cold-condition, it produces a beer that tastes like a Pilsner. I don't know what spikes you'd see under HPLC analysis, and I don't think that strain would sequence as S. pastorianus, but the beer it makes under those conditions tastes like a lager to me.

To me, a clean beer is one that has a low ester character, no detectable phenolics, and no noticeable fusels. My tolerance for "low ester" may indeed vary depending on the style. It's definitely subjective, but when it comes to beer I prefer to define things by how its tastes & smells, rather than process/ingredients. It's about what's in the glass to me, in the end.

[Drewch]

Clean, to me, indicates a lack of microbe/fermentation-derived flavors --- no discernable phenols, strong esters, etc., from the Sacc., but also no Brett. funk and no bacterial contributions. The flavor and aroma are driven by the malt and traditional hop bitterness.

I'm of two minds on how other variables play ... Is a rauchbier clean? Is a hazy NEIPA clean? I'm not sure ... but I want to say no. But I also want to say that a comparatively estery English ale would be.

[Megary]

Clean - no obvious yeast derived flavors/characteristics.  Lager or Ale (another hat tip to BRY-97j.

Of course most ales have far more interesting things going on in the beer and will often mask an ester here or there. 

[Homebrew_kev]

Bud Light is a clean beer

I like yeast to give some character, czech strains have diacetyl, 34/70 gives off acetaldehyde, every Hazy IPA has some very good yeast characteristics.

Off flavors are only off when they over power the beer.

Pilsner Urquell is delicious because of diacetyl.

[Drewch]

Off flavors are only off when they over power the beer

It's only an off flavor if you don't want it there; or conversely, anything can be an off flavor if it's out of place.

[Cliffs]

To me, "clean" means that you don't know the yeast is there--all you get is the malt and hop character. No fruitiness, no phenols, no sulfur, or any of the other things that yeast might throw off. It is somewhat strain dependent (e.g., a Belgian ale vs. a Chico strain), but also technique dependent (e.g., a lager yeast fermented at 50 degrees versus 75 degrees).


My "stereotype" of a clean yeast strain would be Diamond Lager fermented at 50 degrees and given the appropriate amount of lagering afterwards. A non-clean example would be Belgian Abbaye fermented at 80 degrees.

the caveat to the bolded statement is that some "clean" yeasts emphasize malt sweetness and character, while other clean yeasts help empasize hop flavors.