Author Topic: Bottle Conditioning Issue: Acetaldehyde and CBC-1  (Read 1488 times)

Offline jamesablum

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Bottle Conditioning Issue: Acetaldehyde and CBC-1
« on: January 24, 2018, 06:46:40 PM »
Over the last year I've been having a peculiar issue with acetaldehyde and bottle conditioning. After extensive research--both in my print library and online--I remain flummoxed. Perhaps, the community can help.

Here is a bit of background:

I have been homebrewing for about twelve years. I rely solely on force carbonation for many of my lagers and American-style brews, but for certain classic European styles (such as Belgian ales, mixed-fermentaiton beers, and German wheat beers) and big beers I like to bottle condition--to obtain very high carbonation levels for the former example and to help promote the longevity of the beer for the latter example.

In order to really dial in my carbonation, here is how I typically bottle condition. After fermentation, I will keg the beer, chill it, and carbonate it to 2 volumes. A couple of days before the beer has finished carbonating to that level, I will make an acclimation starter consisting of 50% DME-based wort (~1.035), 50% of the base beer, and two grams of rehydrated dry yeast. After approximately 24 hours, the acclimation starter will be chilled. When it is time to bottle, I decant the acclimation starter and add the yeast slurry along with an appropriate dosage of cane sugar (which has been dissolved in water, boiled, and chilled) to provide enough sucrose to reach my final target carbonation level (usually 3.25-4.25 volumes).

I realize that my method is relatively laborious, but I use this method because it allows me to laser target my carbonation level (since I know exactly the carbonation level of my beer before bottle conditioning), reach very high carbonation levels, and take advantage of the oxygen-scavenging benefits of bottle conditioning. And, with the exception of what I will describe below, it has worked like a charm, reliably and rapidly carbonating very alcoholic and/or acidic beers.

So, here comes the rub.

About a year ago, based on positive online reviews, I started using CBC-1 as part of the above protocol. At first, I bottle conditioned a number of Belgian saisons, and everything worked like a charm and the taste was spot on. The CBC-1 led to bottles being fully carbonated in a week or less, and the lees formed a thin, compact layer on the bottom of the bottles. The primary-fermentation strain that I was using for those Belgian saisons was WLP 566 Saison II. I bottle conditioned (a) lower-alcohol, quick turnaround table saisons (~1.048 O.G., primary fermented for about ten days); (b) moderate-alcohol, moderate turnaround saisons (~1.062 O.G., primary fermented for between fourteen and twenty-one days); and (c) higher-alcohol, long turnaround bieres de garde (~1.072 O.G., primary fermented for approximately twenty-one days, and lagered for approximately two months).

Based on my success with bottle conditioning those saisons with CBC-1, I turned to some other beers.

In a line of lagers fermented with WLP 833 German Bock Lager, I decided to bottle condition a tropical stout and Baltic porter. Those beers were fermented in line with my normal lager protocol (healthy pitch of a proper amount of lager yeast, step fermented with a rising temperature over three weeks, diacetyl rested at the end), and checked for diacetyl (via a forced test), acetaldehyde, and terminal gravity before crashing and lagering. Both beers tasted as expected before and after their 14-week lagering periods. However, after bottle conditioning as per the above method with CBC-1, the beers developed a marked acetaldehyde character--underripe apple, somewhat acetic and solvent, and almost plastic-like on the finish--that completely overwhelmed the other flavors. All other lagers that I made in this series with WLP 833--German-style pilsner, rauchbier, Vienna lager, pale doppelbock, dunkles bock, schwartzbier, and Munich dunkel--were solely force carbonated and never developed acetaldehyde in the bottle.

Finally, in a line of German-style wheat beers fermented with WLP 380 Hefeweizen IV, I had a similarly bad experience. I brewed a hefeweizen, dunkelweizen, and weizenbock, again ensuring that all had proper time to primary ferment. They too were bottle conditioned using the above procedure with CBC-1. And, once again, all three batches developed acetaldehyde in the bottle. As a control, re-made the dunkelweizen and solely force carbonated it to a high (though not as high, given the limits of bottling beer force carbonated above about 3.25 volumes) level. That batch showed no acetaldehyde.

I should note that some of the batches that showed acetaldehyde were given as much as two months in the bottle. The acetaldehyde never disappeared, let alone reduced at any appreciable level.

I'm stumped about what's going on here. It appears that the bottle-conditioning step is the common factor among all of the acetaldehyde beers. However, I'm having difficulty attributing it solely to my use of CBC-1 since none of the saisons--again, all of which were bottle-conditioned using CBC-1 and the identical procedure as the lagers and wheat beers--showed the acetaldehyde fault in bottle. Also, I'm largely convinced that other possible contributors of acetaldehyde are not at play since none of the beers showed acetaldehyde before bottling and, in any event, if factors such as over oxygenation at pitching, early removal of beer from the yeast cake, and/or oxidation at packaging was the culprit, then the other beers (i.e., the purely force-carbonated beers and/or the bottle-conditioned saisons) would have been expected to show the acetaldehyde fault.

Does anyone have any guess at what's going on or have any similar experiences? If, indeed, CBC-1 is the cause, then it appears that it is throwing off acetaldehyde during bottle re-fermentation and not cleaning up after itself. If that's the case, then for some reason in the WLP 566 saisons the primary yeast seems to be cleaning up in its place, which is particularly odd in the bieres de garde since they had been lagering for two months, and, therefore, it seems strange that they would have enough viable yeast to do the clean up, never mind doing it so quickly (read: in under a week). Could there be some other factor at play--some interaction between beers fermented with WLP 833 or WLP 380 and then bottle conditioned with CBC-1 that does not arise where the primary strain is WLP 566?

Practically speaking, I will probably be turning to some other dry yeast for bottle conditioning--perhaps returning to T-58 or trying out EC-1118. But, I'm really just interested in ferreting out what's going on here (since I otherwise really like CBC-1's performance), not to mention that if this issue is not specific to CBC-1 then it might crop up again with a different strain. Also, after throwing out so much beer, I'd like to learn something concrete!

Thanks for reading, and sorry for the book-like post!

Offline dmtaylor

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Re: Bottle Conditioning Issue: Acetaldehyde and CBC-1
« Reply #1 on: January 24, 2018, 06:52:26 PM »
Sorry I can't help.  I've bottled about 140 batches over the past 19 years, but never have I used CBC-1 or the method you describe.  In all those batches, I only experienced acetaldehyde one time, and that was when I was newbie and severely underpitched an old dead vial like 10 months old with no starter into 5 gallons or something like that.  Perhaps try using more than 2 grams yeast, and give the yeast more time to get acclimated?  I'm not sure.

The world will become a much more pleasant place to live when each and every one of us realizes that we are all idiots.

Offline FermentedCulture

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Re: Bottle Conditioning Issue: Acetaldehyde and CBC-1
« Reply #2 on: January 25, 2018, 06:27:27 PM »
White labs have their acetaldehyde testing results on their wlp833 page btw, maybe compare it to the other ones. Just throwing these out there since it's impossible to pinpoint without testing:

It might be ethyl hexanoate.

It could be something like: If you have any bottles left you could plate for contaminants.

It could be cross contamination at the plant with a different yeast/bacteria (sour pitch).

It might be an interaction of the yeast with the compounds left in the beer, while these bottling yeasts are supposed to be neutral (they are just champagne yeast) they do effect the final flavour of the beer.

The increased time to the heightened temperature might have influenced the ester profile in which the acetaldehyde or ethyl hexanoate became more prominent. Yeast esterase continues to break down the esters while it ages, isoamyl acetate being one of the main ones to be broken down. You could force age a forced carb'd bottle if you have any left to see if it arises without the seeded yeast.

Some precursor might be made during the aeration of the 50% beer in the starter.

I might post some more things later once I think about it more.

edit1: How long did you age the beer? I had a notably lactic, yeasty character with k-97 which aged out over time. Maybe due to a pH raise with the yeast autolysis I don't know.

BTW I like your procedure, it's a good way to minimise sediment. Do you accilimatise the beer to re-fermentation temperature? You can cut off some bottle carbonation time there if you fill cold (also the yeast will be a better scavenger of oxygen since they won't be cold!).

edit2: from a quick search it does look like ec-1118 is reasonably good at making ethyl hexanoate.

edit3: has anyone else tasted it?

edit: if you don't have access to a microscope or plates this might work -
« Last Edit: January 25, 2018, 08:01:28 PM by FermentedCulture »

Offline jamesablum

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Re: Bottle Conditioning Issue: Acetaldehyde and CBC-1
« Reply #3 on: January 26, 2018, 01:34:59 AM »
Thank you both for the feedback.

As far as ethyl hexanoate, I honestly haven't done any sensory training on that off flavor. From reading the description, though, it sounds like it presents mostly as a sharp spice and underripe fruit character. There's an acetic, almost aseptic edge mingling with the underripe apple flavor in my "off" beers, so acetaldehyde seems the most likely culprit, and I'm fairly familiar with the flavor of acetaldehyde (and this just tastes of it).

Regarding Zymomonas Mobilis, that's certainly possible. Since I am priming with cane sugar (rather than DME) and that bacteria is rather hard to eradicate once an infection sets in, I could see that being a problem. The thing that doesn't line up, however, is that the saisons, which were bottle conditioned with the same equipment and process, never showed the acetaldehyde biproduct. If anything, WLP 566's and WLP 833's abilities to ferment higher-than-average levels of maltotriose would actually seem to encourage an environment for Zymomonas Mobilis, which again leaves the saisons as the mystery (or proverbial "wrench" in the theory).

Age-wise, it varied. The two bottle-conditioned lagers sat for at least two months before I gave up on them, and the hefeweizen probably sat for nearly the same amount of time. The other beers showed the off characteristic within a week of packaging, and given my experiences with the lagers and hefeweizen I just cut my losses early. I probably should have saved a bottle of each, but I just considered the batches failures and wanted to be rid of them.

I'm tending to think that there is something going on with CBC-1 and my bottle-conditioning regimen. Assuming there is not a contamination and that my beers are properly finished fermenting, residual cells of WLP 566 seem to somehow correct for the acetaldehyde being generated by CBC-1 during the refermentation process (something that, apparently, WLP833 and WLP380 cells are unable or unwilling to do).

Tomorrow, I'm going to bottle another WLP380 batch, but with an acclimation starter using EC-1118. I tasted this WLP380 batch, which spent three weeks in primary, when I drew the 50% portion for the acclimation starter, and it tasted 100% free of acetaldehyde (or whatever that off-flavor actually is). I'll report back next week after I have a chance to taste this batch.

A small handful of others tasted one of the "bad" batches, but none of those individuals really had much beer-palate training. They liked the beer, actually. Honestly, a large portion of the off flavor comes retronasally (particularly with burps), so unless you drink a lot of beer and are paying attention, you could easily miss the off flavor.

Lastly, as far as acclimating the beer, are you referring to the starter or the main batch? The acclimation starter is grown at approximately 70F for about a day, chilled to 35F for another day, decanted, and pitched into the main batch, which I immediately bottle at around 40F. The bottles of beer are then allowed to increase to approximately 70F to referment. Even with beers over 9% abv where I am adding around 2 volumes of additional CO2 via bottle conditioning, the referementation process never takes more than a week.

Offline FermentedCulture

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Re: Bottle Conditioning Issue: Acetaldehyde and CBC-1
« Reply #4 on: January 29, 2018, 09:15:40 PM »
Ethyl hexanoate is an ester, it is commonly referred to as smelling of red apples and some descriptions have aniseed. There's other esters like ethyl octanoate which is described as having an apple smell (some sources note sour apple) and other sources have fruity.

I brought ethyl hexanoate up because I thought I remembered it being one of the main esters in lager fermentation. Also one of the memes which used be to touted was that budweiser used to smell of acetaldehyde, this was corrected by Mitch Steele explaining that it is the ester profile of their beer. There was also a big thread a while back about homebrewing judges deducting marks off beers which had these esters as they thought it was acetaldehyde.

In terms of lager yeast the saaz and frohberg type strains produce different levels of acetaldehyde; with saaz being more cryotolerant and producing more acetaldehyde. I'm unsure what type wlp833 is but it should be typed in a few months time. Comparing it with the other strains in the whitelabs line up it is cold tolerant, slightly on the lower side of the attenuative range and slightly more alcohol tolerant. This might hint it is saaz but like I said you could look on their website and compare all of their acetaldehyde levels for their lager yeast with wlp833 to see where it fits on the range.

I found an interesting presentation that states at concentrations of 20-25mg/L acetaldehyde makes the green apple flavours. The whitelabs website has it's test beer of wlp833 at 25.31ppm. So it might be a case of the refermentation process changing the aroma profile of the beer, perhaps even the heightened carbonation after refermentation increased the expression of it. Weirdly, for comparison wlp830/[w34/70] had 38.88ppm.

Maybe I'm misinterpreting this but I'm confused with your comment on wlp833 fermenting a higher than average level of maltotriose as the attenuation range has been listed on the whitelabs website and it is on the lower end. Also it appears that Z mobilis doesn't ferment maltotriose so I'm confused as low residual maltriose would help it. Either way it looks like it's unimportant as from the description of your beer and process it doesn't sound like it's contaminated.

There is a possibility that because CBC-1 is a killer strain it is effecting some yeast strains but not others. As you say, maybe the residual yeast would then be changing the flavour profile while the effected strains are not. Milkthefunk states on it that "One study in wine found that the use of killer strains to out compete sensitive strains resulted in off-flavors from yeast autolysis", however I'd need to look at the study to find out the percentages. That page also says that one of the commercial saison strains which is diastaticus is killer neutral so maybe wlp566 which looks like it is diastaticus, is also neutral to the champagne yeast while the lager strains are affected. There are flavours which are like plastic caused by autolysis which might be what you tasted. Leaving beer - depending on the strain, the temperature, alcohol percentage and pressure - for weeks on end can also make these flavours.

Maybe try SN9? I think it's a different less flavour neutral champagne yeast, I've only refermented 3-4 beers with it and it gave a subtle hint of rhubarb.

In terms of acclimatising the beer I meant bringing the beer which is in the keg up to the same temperature as you are going to referment at. While it does shorten carbonation times it also makes sure the yeast are active, ready to consume oxygen in the packaging process.

One of the other things which I don't think was mentioned is whether or not you are changing the seeding rate of yeast for recarbonation of different beers - I don't know how this effects the beer but I wouldn't be surprised if it is similar to normal fermentation (albeit under pressure). Speaking of which maybe the temperature of refermentation is effecting the ester levels also. So many parameters!

Anyways I wish you the best for the wlp380, it's a frustrating process having to throw away good beer! Cheers.

Offline 802Chris

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Re: Bottle Conditioning Issue: Acetaldehyde and CBC-1
« Reply #5 on: February 02, 2018, 05:20:44 PM »
I'm gonna take a stab and say that maybe the saison yeast was carrying a bug and it eventually took root in your bottling equipment . I have heard but never verified that some saison/Belgian yeasts have been shown to carry bugs that don't play so nice and can be quite hard to eradicate. In looking over all your posts, the common variable seems to be the bottling equipment (not the CBC-1), since the forced carb beers are not displaying symptoms, nor did the original saisons.