Tuesday, February 15, 2011

(an) English Yeast Off-Flavor

With all the recent discussions over at 'homebrewtalk' about fermenting English yeast strains, I thought I would say a few words about a two yeast derived off-flavors that frequently pop up in some commerical and homebrewed English style ales. The two English yeasts I think people most often have off-flavors with are wy1968/wlp002 and Whitbread/Safale S-04.


My first experience with the "twang"
The primary off-flavor that I have run into with wlp002/1968 is a particularly tart-ciderish flavor that comes up quite frequently in bottle conditioned examples. Some people have described it as acetaldehyde tasting, though I find it a little more dry-cidery tasting than green apple. In my experience, the beer tastes fine or even great at racking but soon after develops this off-flavor around 3 weeks in the bottle and is typically accompanied by a drop in gravity or rise in carbonation. Now while that would seemingly point to an infection somewhere along the line, I do not think this is often the case as it does not typically occur with beers that have been force carbonated in the bottle or keg. Instead I believe it has something to do with the yeast becoming reactivated once it comes into contact with the priming sugar, resulting in off flavors and excess carbonation. I have had this happen to a few of my beers and have tried lots of other homebrews that had the same problem. Often people were completely unaware of the off-flavor or had assumed it was just part of the yeast's flavor profile. I have even encountered this off-flavor in a few commercial products, most notably from Portsmouth, McNeils, and a few other small breweries I frequent in the Northeast. What exactly causes this, I'd really like to know.

The other English yeast off flavor that I frequently come across is something I call the Whitbread "twang." By this I mean the beer has a definite tangy, bready-yogurt-estery quality that renders the beer nearly undrinkable for my tastes. I first encountered this off flavor when I started brewing and found myself using S-04, wy1098 & 1099 quite frequently. I am pretty sure this off-flavor is caused by too warm of a fermentation and/or under pitching. Whatever causes this flavor, it seems to pop up in many homebrewed examples and with some frequency in small brewpubs and the occasional microbrewery that uses those yeasts. Yet, some people don't seem to mind this flavor too much and a few crazy people have gone far enough to tell me this character is normal. I don't agree with that, but hey, some people are content drinking crappy beer.


14 comments:

  1. I followed the link from your signature on HBT. Nice blog you got here. Regarding the off flavor in English bottle conditioned beers, I've always attributed this to infection. I've come across the same thing a few times with a drop in gravity resulting in increased carbonation. This eventually led me to kegging. While this has eliminated this off flavor, I believe it has done so because the beer, once racked, is immediately chilled in the keg thus stopping the potential infection. Bottle conditioned beers, on the other hand, have to risk infection in a bottling bucket after racking and sit on a shelf at 70F for 3 weeks.

    Now, on the flip side, I've only noticed this with English yeasts. Why? My guess is that English beers I've made have all been lower alcohol than my 1056 or Belgian beers. Another idea is the strain's tolerance to wild yeasts. I'm no microbiologist, but I understand there are different types of yeasts such as killer, positive, and negative. These traits allow some yeasts to be able to be blended while others simply overtake the fermentation. I've read that 1187 cannot be blended because it overpowers all other yeasts. So 1968 could be weaker, I'm guessing, than 1056 or 1187 against certain wild yeasts.

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  2. Thanks for the comment! You may very well be correct about it being some form of infection, I was under the same impression as I only encountered this problem with bottle conditioned examples. However, I did some research on this off flavor and got a few responses from pro-brewers and BJCP types that mentioned similar problems with bottle carbonating with this particular yeast strain. What the exact cause it I never found out. Could be bacteria or yeast? I'll have to do some more research on the topic, though luckily I have not encountered this problem in my bottled/kegged beers in a long while.

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  3. What kind of yeast do you use, than, to get that english bready/fruity character, solid attenuation, but without these off flavors? Likewise, have you ever re-pitched a proper amount of yeast from your primary into another batch and seen how the resultant beer tastes?

    I'm also curious if you are typically using secondary fermentation for something like S-04 as well. This strain seems to flocculate so well that I've seen it suggested that the yeast may need to be be roused at times, which may also be why you notice a notworthy drop in gravity after adding carbonation sugar and re-activating the yeast.

    That said, bottling is a fermentation of it's own, as you know. If you transfer from primary to secondary, and then later rack off of the secondary to prime/bottle, it's not inconceivable that so much yeast has dropped out of suspension, that it's as if you are 'under pitching' for the carbonation, and underpitching can make for increased esters and off flavors. I'm shooting from the hip here of course, but that does seem to be the major difference between your kegging and bottled examples, as the yeast are not re-activated in the keg with forced carbonation.

    I'm actually experimenting with S-04 after using Nottingham for quite a few brews. The Nottingham is really clean and fast and attenuative. But it's hard to say it's got much flavor character at all, for better or worse.

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  4. Matt,

    We are very lucky that there are dozens of excellent English strains available to us that all have unique flavors, characteristics, and so on. It really depends on what flavors I want in a beer that determines the yeast I use. If you are looking for a balanced, dry character, s-04 and the Whitbread strains (wy1098/99/wlp007)is a good choice, so long as you have a control over your fermentation temps. Notty is another great strain, fast fermenting, high attenuation, ect... but it is much to bland for most of my uses. Many beginners like these strains due that they are easy to use and make consistently drinkable beer when fermented correctly.

    However, my preference for English strains favors those yeast that produce a beer with a complex, rich malt profile with medium esters, high flocc, and are generally top croppers. WY1968, 1318, bedford bitter, thames valley II, 1469, and 1187 are the strains I like best for my English ales.

    You are right about some British strains needing to be roused. I've done this for years, though only when necessary, and usually with 1968 and 1187.

    Lastly, the only time I use secondaries are when I am either dry-hopping, bulk aging for more than a month, or adding souring bugs/brett.

    Thanks for your comment!

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  5. Any experience or opinions on Wyeast 1275 / Thames Valley?

    I found the s-04 didn't attenuate well with the cooler temps that Nottingham does well with, though the s-04 flavor profile is quite nice so far. It's easier for me to maintain cool temps (water bath) than warmer temps (space heater in a small space), and I'd generally rather raise my FG via my mash temp than yeast strains that attenuate 'poorly' anyhow.

    The Dry Nottingham unleashes a 'cherry pie filling' flavor when I've over-pitched it. While kind of an interesting attribute in a beer with residual sweetness, not something I'm shooting for! I'm not sure what fermentation temperature this might start becoming noticeable, but I try to keep it cool in fear of finding out.

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  6. Matt,

    I have mixed feelings about 1275. On one hand it can make a very nice malty beer, but it can also give off some 'mineral' flavors and it is not the best flocculator. I've had some very nice milds made with it.

    I really should go back and try it again. I would suggest fermenting it in the mid 60's as it can get a bit estery.

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  7. I just recently brewed an english brown ale with S-04 and just wasn't impressed. I had also read on HBT about the S-04 Twant and purposely fermented in the low 60s (about 63 for the first 4 days and then let it rise to 66-67). Although the twang as subsided after 2 months in the keg I find the yeast derived character just too much for my tastes. I don't think I will be using dry S-04 in the future as I just find the beer almost undrinkable

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  8. I was amazed at how many brewers liked the Yorkshire strain as I got a strong flavor and aroma that I call "dry yeast from the 90's",you call it yougurt like, I call it similarly "sour milk". I've never gotten that character from Samuel Smith beers or Timothy Taylor beers.

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  9. hmmm... Interresting. Several years ago I wanted to try a couple beers from samuel smith. I encountered the acetaldehyde aroma you descibed. I did not like it at all and I really thought it was a caracteristic of their yeast. I probably should give Samuel Smith a try again.

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  10. I own a nano and I've been open one month. I use 1968 for all my English and American style beers. When I was homebrewing, I used 1968 extensively, always with fantastic results. Now, I've had to dump one batch of my English IPA and I may have to dump my latest batch of red IPA due to an apple-ish, strange off-flavor. I pay very close attention to pitching rates, I oxygenate, and I can usually brew some very good beer. If this continues to happen, I am going to have to ditch the 1968, which makes me very sad, because I have yet to use a yeast that produces such a great malt profile. Any suggestions?

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    1. Ouch, so sorry to hear that! As per the off flavor, the best answer I got was that it is caused by the yeast reactivating due to 02 exposure during bottling/transfering the beer.

      Case in point, a few months ago I brewed an ordinary bitter with 1968 - oxygenated well, healthy pitch, temp control, ect - but when it came time to kegging, I didn't have any open kegs left, so I racked the beer into a (C02 purged) carboy and let it sit for about 2 weeks. During this time, I noticed a steady stream of very fine bubbles rising to the top. When I finally kegged it, sure enough the beer had that same appley-cidery flavor. There was a slight drop in gravity too. Even after kegging and a few weeks of aging in the cold, the flavor did not improve.

      In contrast, I haven't had problems using 1968 when I've cold crashed and kegged from the primary and not let the beer warm back up prior to serving. In your case, the issue may be due to some 02 pickup (post fermentation) somewhere in your system; so long as it is not a fermentation/sanitation issue. How are these affected beers being stored/transferred? Is there a drop in graviy from leaving the bright tank to when you serve it out of the tap?

      Also, you might want to check the seals on your pumps and insure that they are throughly flooded with beer before you transer. The slightest hole in transfer hoses will pull in air during transfer. Hope you get this issue resolved.

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    2. J, did you ever come to a resolution on this?

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  11. Since you're a nano, the yeast co's might have some tips on replacement....

    But I'd try the scottish strain in a 5 gallon homebrew batch and see what you think about what it does t oyour recipies, for starters...thought there may well be closer...

    I think some breweries and homebrewers I know who have clear ability to control temp use the German Ale strain which is really clean...if I 'm thinking of the right one. That said...your anticipated actual and apparent dryness, hoppiness, and subtler characteristics may all be affected, suffer, and/or seem to take what was just what you wanted to slightly below par. Might be worth it if you're dumping batches. Might not, depending upon how critical it is.

    Some podcasts on the brewing network interview breweries, and the 1968, if I'm not mistaken, is a handful of big breweries go-to strain. Listening to some of those podcasts might offer tips that go beyond the homebrew level and into the larger-scale level.

    Jamil might even have some tips now that he is both an award winning homebrewer, and has transition to the commercial side of things not too long ago...

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  12. Hi Will! Let me first thank you for your interesting blog and the work you're doing!
    I know this is an old post but have you come to any new insight? I encountered that ciderish flavor (in combination with overcarbed bottles) now for the third time unsing #1968 and that realy sucks!

    Cheers,
    Simon

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