Diagnose apple taste and smell

[Roukedou]

I have a brewer friend that has a big apple taste and smell problem in his beers, and I can't figure out where the problem is coming from. He made many good beers before, but since last year, all his beers got this problem. He's doing a good aeration, tried many yeast strain, used complete different gear setup, fermentation temperatures are not super controlled, but nothing alarming, at least not enough to make 6 batches taste like that... There seems to be no visual signs of infection.

He tells me the problem appears at the start of fermentation, maybe 3-4 days in. He has an all grain setup.

 

[Biobrewer]

This could be a result of either lack of fermentation temperature control and/or by under pitching yeast. Check out this guide to off flavors. This may help your friend with their problem:

http://morebeer.com/themes/morewinepro/mmpdfs/mb/off_flavor.pdf

Cheers!

 

[Roukedou]

Temperatures are not really controlled, but decent, and the thing is the problem appears year-long, so I don't think that's the source of it.

As for pitching, he uses White Labs yeast vial directly into 5 gal batches. That's slightly underpitched, but this issue shoudn't appear on every brew...

He keeps the beer in primary for 3 weeks, so it's not from separating the yeast and the beer early. Also, since the problem appears only after 3-4 days, I don't think it's ethanol going back into acetaldehyde from oxydation.

 

[Trail]

As for pitching, he uses White Labs yeast vial directly into 5 gal batches. That's slightly underpitched, but this issue shoudn't appear on every brew...

He's underpitching every time, and you don't think that every brew should taste underpitched?

Temperatures are not really controlled, but decent, and the thing is the problem appears year-long, so I don't think that's the source of it.

He's not controlling temperatures, and you don't think that every brew should taste like they are not temperature controlled?

 

[Roukedou]

He's underpitching every time, and you don't think that every brew should taste underpitched?

One vial of yeast for a 5 gal regular brew is slightly underpitched, but is usually more than enough to get a good tasting beer. Yes with some strain you're looking for trouble by not making a starter, and there's a chance that your good old regular yeast crap on you because your mash was different this one time, but most of the time for a 1.045-1.050 OG beer, you'll be fine with straight pitching the vial. I'm not saying there's no consequences with underpitching, but I don't think that a slight underpitch will cause massive acetaldehyde in each beer for a year with many different yeast strains.

He's not controlling temperatures, and you don't think that every brew should taste like they are not temperature controlled

He's not controlling temps, but he's still using good practices... Cooling it just below target temperature before pitching, let it warm up a bit during growth phase, then in the basement during high krausen and then to a bit warmer room for the rest of the primary. Yes this might also cause some off flavors, but I don't think this is the cause of year long acetaldehyde, regardless of winter or summertime...

 

[Brewskii]

Anyone suspect AA? I do.

http://www.howtobrew.com/section4/chapter21-2.html

 

[Trail]

I apologize if I came across as brusque before, but I must maintain my insistence on these two points:

One vial of yeast for a 5 gal regular brew is slightly underpitched, but is usually more than enough to get a good tasting beer.

Slightly underpitched, assuming that viability is high. You don't know what's going on here - maybe he changed suppliers, maybe his existing supplier started storing the yeast on the other side of the warehouse away from the cooling duct, maybe they've started ordering it from a different warehouse entirely that moves product more slowly. You can't know how viable your cell count is without a lab assay (or a good microscope and a competent biologist buddy), which is why a starter is ALWAYS a good idea.

He's not controlling temps, but he's still using good practices... Cooling it just below target temperature before pitching, let it warm up a bit during growth phase, then in the basement during high krausen and then to a bit warmer room for the rest of the primary. Yes this might also cause some off flavors, but I don't think this is the cause of year long acetaldehyde, regardless of winter or summertime...

What you just described is not good practices for temp control. If "target temperature" is somewhere safe - say, the middle of the range - you don't want to let it warm up during growth. Sticking it in the basement does not control temperature... at the very least, use a swamp cooler. You only want to raise the temperature once fermentation slows down - once there's only 20-35% of your total attenuation left, and there isn't enough sugar to support rapid consumption and growth.

Note that I said if target temperature is somewhere safe. What I mean by this is: if the target temp is at the top end of the spectrum, this can result in inadvertently overshooting your temp. Even if it isn't, a bad (or simply miscalibrated) thermometer can result in overshooting temps. My brewing thermometer is one of the best available, and it's consistently two degrees high... played hell with my first few all grain batches, I can tell you.

Keeping it cold before fermentation starts means that you're controlling temperature when it matters least. Have your buddy grab a rope-handle bucket at Lowe's for $5, chuck in a couple two liters and add some water, and see what happens. Though I'm concerned about your pitch rate* I'd bet temps are where the real issue is.


*White Labs used to only ship 30-50bil cells per vial, and even today they retain a reputation for insufficiency compared to Wyeast. Comparatively, Wyeast has larger packaging, and the gimmicky crush-capsule proofing wins a lot of hearts. Volume-wise, I don't think there's much difference between the brands, but Wyeast users are much more willing to pitch sans starter... to their eminent peril.

That said, from the White Labs website:

How long can I wait to use White Labs Pure Brewers Yeast?
White Labs Pure Brewers Yeast leave our lab at 95%+ viability. We suggest you use it the day after you receive it. Do not try to brew on the same day of receipt of the yeast. We have great success with our shipping companies getting you the yeast on time but we would hate to have you knocking out and the yeast has not arrived. If you need to wait longer than the day after receipt we suggest using it within 7 days. The fresher the better.

The manufacturer is pretty insistent that it get used immediately. How long does your homebrew supplier have it before you get it?

 

[Battles4Seattle]

I have to agree if he's not making a starter every beer that is a consistent issue. What types of beer is he brewing too? Anything with higher alcohol content will make things worse.

Have him put a carboy/bucket thermometer on his fermenter and use a swamp cooler and see if the off taste continues.

Both of these things are easy and cheap to correct. If he really does not want to make a starter (So easy!), just pinch more vials or use dry yeast according to Mr. Malty.

 

[aiptasia]

Acetylaldehyde, from a young "green" beer is quite common.

 

[Beernik]

I got bad Acetylaldehyde from pitching too warm.

 

[Roukedou]

It's alright Kerin, I asked him the same questions. I just wanted to walk you through my though. I'm quite confused, because although it's not excellent, his protocol should give some good beers, which could use some improvement of course, but still good beer.

As for the yeast and the supplier, I use the same and he's the main distributor in the province, and he handles 22 tons of grain per week, the yeast is well stored and the turn around is quick. On a couple batches he made a starter, for many styles of beer but generally of 1.050 OG or less, but this had no impact on the problem.

The temperature control could be a source of the problem, but I find it strange that a setup, recipe and yeast that worked fine for a couple of years now seems to be not working anymore... Anyhow I told him to put a strip thermometer on his fermentor to gather some more substantial data, but I don't think I'll find something extra suprising there.

 

[Trail]

There are three major causes of acetaldehyde: fermentation temperature, pitch rate, and green beer. We have strong reason to suspect at least one of those. He might also be oxidizing or infecting his beer, though it's a stretch.

I'm at a loss for what to suggest, beyond that. One might as well ask why buddy never falls up instead of down when he trips, because he's really sure it isn't that gravity thing.

I would be very concerned if it isn't one of the issues we've discussed tonight, which would mean you're having problems no homebrewer has ever had before. Spooky business.

 

[knifewine]

Sorry for necroposting --

I ran into this exact problem a while back, never did figure out exactly the cause. Presumably a slow-going infection.

It happened to two beers that were (obviously) isolated from one another. I dipped a sterilized carafe into each one to grab a hydrometer sample, but sterilized it between each sample so that I wouldn't cross-contaminate yeast. It's possible this is how I moved the contaminant from one fermenter to the other.

At any rate I assumed the problem was acetylaldehyde and I think the contamination may have actually come from my tap system. Either a skunky cobra tap backflowing into my corny or perhaps even something that managed to survive in my co2 hose.

It definitely tainted my serving hoses and even many gallons later I can still taste green apples if I haven't poured a beer in a while.

I'd encourage your friend to sanitize any kegging/serving equipment that touches the finished product and check the hose to see if it's holding the funky flavor.

 

[mkeckjr]

In addition to checking your lines, I think there are a couple of other reasons acetaldehyde may consistently show up that are fairly common:

• Removing the beer from the yeast cake too early. I think of this as slightly different than green beer, which simply indicates the beer is young.
• Under-oxygenation before pitching.

These have the exact same effect as not properly controlling fermentation temperature and pitch rate. Acetaldehyde is an intermediate product in the fermentation process and is eventually consumed by the yeast and turned into ethanol. If you either under pitch, fail to properly control fermentation temperature (each of which Trail pointed out), or have too little oxygen in the wort before pitching the yeast may get too stressed out and not finish their job, and thus leave more acetaldehyde and less ethanol than they usually would. Same thing happens if you did all of those things correctly, but you pull the beer off the yeast too early. You will have incomplete conversion of the acetaldehyde into ethanol, and the green apple taste will come out.

I would look into any of these if you're having consistent acetaldehyde problems.