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How do you fix diacetyl and astringency off-flavors?

I entered a homebrew competition recently with the 8th beer I have made and the judges found off-flavors of diacetyl, astringency, and slight warmth of aclohol in a low gravity, 1.040 OG, beer. This was a shock to me because I entered the second homebrew I ever made back in January in a homebrew competition and got 3rd place out of 8 people. I know my methods have only gotten better since then so I am having a hard time figuring out where these recent off-flavors are coming from. The two beers which had off-flavors were an extract Little Bear Session CDA and a partial mash RyePA.

I have been keeping notes of my beers and have not noticed the off-flavors until the beers have been bottled. Now that the off-flavor has been brought to my attention I do taste a slick or oily mouthfeel with my two most recent beers and a harsh astringent taste which I thought were the bittering hops. My thought is the issue could be from my bottling tubing, which came with my starter kit, because the tubing does have a light brown, sticky looking film on the inside; however, I do thouroughly sanitize everything with Star San. Could dirty tubing be the issue creating my off-flavors? If so, how long do people usually use their buckets, tubing, and other equipment before getting replacements?

Any advice is greatly appreciated!

What were your fermentation temps? How long did your beer sit in primary? How long in bottles before you entered the competition?

I think a lot of people use their buckets and tubing a pretty long time. But when in doubt, it’s a cheap fix to replace some tubing. The bottling bucket should have the spout removed, taken apart and cleaned somewhat often. Nasties and lurk in there.

Below is taken from How to Brew.

Diacetyl is most often described as a butter or butterscotch flavor. Smell an unpopped bag of butter flavor microwave popcorn for a good example. It is desired to a degree in many ales, but in some styles (mainly lagers) and circumstances it is unwanted and may even take on rancid overtones. Diacetyl can be the result of the normal fermentation process or the result of a bacterial infection. Diacetyl is produced early in the fermentation cycle by the yeast and is gradually reassimilated towards the end of the fermentation. A brew that experiences a long lag time due to weak yeast or insufficient aeration will produce a lot of diacetyl before the main fermentation begins. In this case there is often more diacetyl than the yeast can consume at the end of fermentation and it can dominate the flavor of the beer.

Astringency differs from bitterness by having a puckering quality, like sucking on a tea bag. It is dry, kind of powdery and is often the result of steeping grains too long or when the pH of the mash exceeds the range of 5.2 - 5.6. Oversparging the mash or using water that is too hot are common causes for exceeding the mash pH range. It can also be caused by over-hopping during either the bittering or finishing stages. Bacterial infections can also cause astringency, i.e. vinegar tones from aceto bacteria.

The brown scum that forms during fermentation and clings to the side of the fermentor is intensely bitter and if it is stirred back into the beer it will cause very astringent tastes. The scum should be removed from the beer, either by letting it cling undisturbed to the sides of an oversize fermentor, or by skimming it off the krausen, or blowing off the krausen itself from a 5 gallon carboy. I have never had any problems by simply letting it cling to the sides of the fermentor.

Can you answer me the following (some asked above) about the beers you submitted?

-OG/FG, how long in primary fermenter?

-How do you / Do you control fermentation temps, and what yeast did you use? (I had some similar notes from judges on a summer blonde and saison I brewed where I let temperatures run wild…pithy, astringent, etc.)

-how long in bottles?

-how do you clean your bottles (for years, I would just soak in sanitizer and not use the utility sink water blaster…outside chance they got a few infected bottles?)

Long story short, the answers above are true. Trying to pinpoint the point in your process where it happens is another story.

Thanks for the responses!

I have been thinking about where the issue may have come from and for the Little Bear Session CDA, I am sure it was a yeast issue. I rinsed yeast from a high gravity Black IPA, which I know you are not suppose to use yeast from a high gravity beer, and had it in my fridge for months before making a starter for the CDA. I would guess this rinsed Wyeast 1272 was at a pretty low viatality when I used it for my CDA. Therefore, the yeast was likely unable to clean up all of the diacetyl produced. My fermentation temp was 65 for the CDA and the fermentation process seemed typical nothing stalled or strange.
Also I always leave my beers in the primary on the yeast until I bottle (usually 3 weeks in primary then I bottle). I dry-hopped the CDA while in primary.

The CDA was in the bottle for one month before the homebrew competition so the beers should have been fine.

I will have to make sure I remove and sanitize the spigot on my bottling bucket more, I have only done that a few times and it could be part of the issue.

After I finish a homebrew, I rinse out the bottle with the faucet a couple times to get all of the yeast out and then store the bottles until bottling day. On bottling day I will soak each bottle in Star San for 2 minutes. Are bottles suppose to be cleaned more than just a two minute Star San soak?

Lastly, I will have to drink another RyePA to see if I really am tasting/smelling diacetyl and astringency. I am not very good at detecting off-flavors so I may just be paranoid and it could be the Summit hops which give off the semi-harsh bitterness which lingers on the tongue (or it might be astringency).

Thanks again; cheers!

What are you using for brewing water?

This was basically my ‘process’ for years. maintaining clean equipment regularly saves time in the long run, and a few aggressive rinses (like with some water, then your thumb over the nozzle of the bottle) typically does remove all of the yeast sediment in homebrew bottles.

HOWEVER, this is a bit of Russian roulette. The old saying is, “You can’t sanitize a turd”, so if you don’t CLEAN AND SANITIZE all cold-side equipment each time you use it, you do risk the chance of having some gunk in a bottle that can spoil it.

My recommendation: buy one of the brass utility sink-fitted bottle/carboy spraying pieces that will blast the inside of your bottles, and do that each time before you sanitize. This may be overkill, but its one thing I know is not going to be an issue.

Do NOT buy a bottle brush, because it is a pain in the A, and if you are like me, it will sit in your gear chest and collect dust.

I use my tap water for brewing but I add campden tablets to get rid of the cholrine.

I am drinking a RyePA now and it tastes great and I do not smell any diacetyl. My thought is my use of unhealthy yeast in my Little Bear Session CDA caused the off-flavors and then I began to worry my other beers have gone bad too. Thankfully I feel this is not the case and it is just a case of paranoia and one bad batch of beer due to poor yeast health.

Thanks for making me feel I am doing a good job sanitizing my bottles. However, I may still look into getting a bottle washer to help alleviate future worry and not harm any upcoming batches.

I plan to start all-grain brewing this Fall and get a keg system from Santa!


I think you have gotten a number of good suggestions above, and I second those. I would emphasize some of the sanitation issues you brought up. Replace the tubing - it is cheap and better safe than sorry. Take your spigots apart every time you clean and sanitize - it is easy and takes very little time. Get the bottle washer.

In regard to the astringency - water could be an issue. Depending on what your water is, it can really cause problems with your hoppy and lighter beers. Don’t remember if I saw it in there anywhere, but if you are doing extract beers, try using all reverse osmosis water from the store - cheap if you fill your own jugs. Extract has minerals in it you need already. If your tap water is really hard or high in mineral content, you may be adding even more, causing some problems. Also, Rye can be a pretty strong grain… I entered a “ryebock” in a recent competition and all the comments focused on the overpowering bitterness that the rye added and to cut back on how much I used - I used 3 pounds in a 6 gallon batch.

Ferm. temps can cause problems with the “hot” alcohol flavors. Ferment in the low 60’s to avoid this.

Thanks Braufessor! The Little Bear Session CDA was an extract beer but the RyePA was a partial mash. I will replace my tubing to be safe.

I will have to get my water analyzed by Ward Labs because I only have information on my water from an individual at the city hall. According to the guy at the city hall, my water is:

Calcium in ppm 62.5

Magnesium in ppm 23.3

Alkalinity as CaC03 202

Chloride in ppm 10.6

Sodium in ppm 2.7

Sulfate in ppm 21.5

pH 7.7

I only treat my water by using campden tablets to get rid of chlorine. For partial mash and all-grain brewing, it is better to use tap water than reverse osmosis (store bought) water, correct?

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