Open Fermenter Experiment and Other Yeast Experiments


Note the slight foam due to a yeast fermentation.

My apologies for not posting anything for a while. Things are getting busy but I still try to post when I can… surely anyone can understand that!

I have been experimenting with different things lately… starting with trying to capture a wild yeast strain, again!  This time I used some pilsner malt and unmalted wheat as the inoculate. While trying to capture some saccharomyces yeast, I knew I would also get some lacto,pedio, brett, and the dreaded acetobacter. After the “normal” yeast fermentation in the first few days, a pellicle was forming and then the vinegar smell followed.

  • Avoiding acetobacter and mold problems

I flushed the quart jar with co2 but it still didn’t keep the acetobacter at bay as it was probably directly pitched from the malt. In the past I have had issues with mold growth, but this time I acidified the wort to combat that issue and it worked pretty well. Obviously plating the culture would be the only way to pull the sacc yeast out of that conglomerate, but mimicking an acidic environment like beer, will definitely weed out the really undesirables.  I used winemakers Acid Blend, which is a mix of citric, malic, and tartaric acid to lower the PH of the fresh wort. In the future when I decide to plate, in addition to adding agar, I will include some acid blend to lower the PH and avoid a mold problem right off the bat. As I mentioned before, acetobacter took hold of the new culture after about a month, so plating is a must if you decide to actually try to use what you catch.

In case you were unaware…Acetobacter is the main microbe responsible for vinegar. In sour beers it is common to have some vinegar notes, but it will quickly overwhelm. I hate vinegar except for salad dressing and cleaning products and I am of the mind that it has no place in beer whatsoever. It is very dominating and will ruin your beer. Acetobacter can grow in an acidic environment and can lay dormant for a while and will survive an active yeast fermentation….however, it does have an easy weakness. Like us, acetobacter needs oxygen to thrive. That shouldn’t be a problem because brewers are taught from the beginning to avoid oxidation with siphoning and bottle wands etc. Basically cut off the oxygen…no vinegar – simple!  This is the reason as a new brewer you were taught to sanitize thoroughly….acetobacter.

Key points on wild yeast capturing (2.0):

  1. Acidify your wort/plating media. A low PH will help keep out some of the nasties. Lactic acid or winemaker’s acid blend will do the trick. This will help keep away mold and mildew etc.
  2. As if I have to say it….SANITIZE everything! Be sure only the inoculate is the ONLY inoculate source unless you are using an “open” style capturing with no set inoculate  ( I have always had great luck with a closed fermenter w/ fruit or grain as the inoculate.)
  3. Keep the culture warm. Warm temps encourage growth.
  4. Avoid oxidation at all costs post yeast fermentation.

Moving into plating your house strain on agar is the obvious next step that requires a few extra pieces of equipment but once again is very simple to do. Hopefully using these points along with agar plating, you can capture your own “house” culture and then truly make a homebrew…using your own yeast!

  • English Yeast Open Fermentation Experiment
Keep a net over the open mouth of the carboy to keep dust and etc. out while the airlock is off.

I experienced a blow-off nearly 12 hrs after this picture.

You’d be surprised how different yeast behaves with an open fermentation! Depending on the yeast strain, a whole slew of different esters are released. I chose a dry English yeast:  safale S-04 for its excellent sedimentation properties and fruity-ale tendencies. My thoughts were to use an English strain and accentuate the esters using open fermentation. If Samuel Smith can use it in their Yorkshire Squares, than I can too!

The next time I try out this experiment, I will likely use a liquid strain like WLP002. I have never really been a HUGE fan of S-04 for various flavor reasons. WLP002 is a great top cropper and makes awesome tasting ales. It will also floc out pretty easy also so that makes it an easy replacement for the S-04.

I experienced a blow-off nearly 12 hrs after this picture.

Keep a net over the open mouth of the carboy to keep dust and etc. out while the airlock is off.

It was a simple recipe based around the yeast strain:

Recipe: Yorkshire Open Fermentation (brewed)

Brewer: Beaconhills Brewhouse

Style: Extra Special/Strong Bitter (English Pale Ale)



Recipe Specifications


Batch Size: 6.50 gal     

Boil Size: 8.30 gal

Estimated OG: 1.059 SG

Estimated Color: 10.5 SRM

Estimated IBU: 33.3 IBU

Boil Time: 60 Minutes




Amount        Item                                      Type         % or IBU     

8 lbs         Pilsner (Weyermann) (1.7 SRM)             Grain        62.11 %      

3 lbs         Rye Malt (Weyermann) (3.0 SRM)            Grain        23.29 %      

1 lbs         Vienna Malt (Weyermann) (3.0 SRM)         Grain        7.76 %       

8.0 oz        Crystal Malt/English DARK (150.0 SRM)     Grain        3.88 %        

6.1 oz        Victory Malt (biscuit) (Briess) (28.0 SRM)Grain        2.95 %       

0.90 oz       Magnum [14.70 %]  (45 min)                Hops         33.3 IBU     

1 Pkgs        SafAle English Ale (DCL Yeast #S-04)      Yeast-Ale   

I still used a carboy, but did not fit an airlock like normal. Instead I used a pull string muslin bag covering the opening, (just to have something in between the precious wort and the outside world.) That way I still have unrestricted airflow, but still maintaining some protection from dust and other things I don’t want in my brew. If anyone has ever used this dry yeast strain, you will know that this is a top cropping strain that tends to blow-off easily…which a great reason to use an English strain. The blow-off will help protect the beer from foreign microbes and that’s exactly what I was betting on. When anticipating a blow off in this situation, one can’t exactly install a blow off tube….it defeats the purpose right?! No problem, just place the carboy in some sort of overflow pan to keep you floor,fridge,freezer etc. from becoming a mess!

The thing to remember is airflow. Open fermentation must have unrestricted airflow in the early primary fermentation stage to produce those different esters you are looking for. However, you MUST keep a watchful eye on the progression of the fermentation. When the blow-off stops and there is no more fermentation “foam” to protect the beer, you must install an airlock or risk airborne infection. The beer becomes very vulnerable without a krausen to protect it from open air. I left the airlock off during the lag phase that only lasted a day or so ( this is where a correct yeast count and a starter helps greatly), and during the blow off. When the fermentation slowed down and the krausen fell, is when I installed the airlock. I think the airlock was left off for about 4-5 days before I got nervous! I also noted that the fermentation went pretty fast…then again on the other hand; it may have just been the yeast strain as well. I have not had the chance to package this beer but the hydro samples taste very “estery” with a heavy dose of phenolics. I knew that would happen due the safeale 04 that was used. I have heard that this process works very well with Hefeweizen beers too. Wits and other Belgian styles also come to mind also. I think any style that is yeast-driven, flavor-wise, will benefit from those extra esters. Open fermentation….just another skill to use when trying to make that beer flavor in your head come alive!

I have also been experimenting with making Belgian candi syrup. I have used it in a nice Belgian dubbel and an American IPA so far. It’s very easy stuff to make and it tastes good on pancakes and waffles too! I will cover this soon in a future article. Until then keep your glasses and airlocks full, Cheers!


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