Tag Archives: Sour

Brewing split batch sour beers (Sour Blend and Lachancea thermotolerans)

I’m not the biggest fan of sour beer, but I am still very interested in brewing with non-conventional microbes. I brewed a batch of sour beer using Wyeast’s Lambic Blend and some bottle dregs around 3.5 years ago. It turned out surprisingly nice, and it got complements from many of my friends who love sour beer. Together with one of these friends, I brewed up a fresh 30L batch of wort (a couple of weeks ago), which I split into two fermenters. These two sub-batches were pitched with two different cultures: The Yeast Bay’s House Sour Blend, which contains a mixture of several different yeasts and bacteria, and a pure culture of a strain of Lachancea thermotolerans, which we’ve (our lab at VTT) isolated from an oak tree here in Finland.


Lachancea thermotolerans is a very interesting yeast, because of its ability to produce lactic acid. From a brewing perspective, this means it can applied e.g. to sour beer production. This is particularly interesting, because it allows for the production of sour beer without the cross-contamination risks associated with the use of lactic acid bacteria. Lachancea thermotolerans has recently gathered some interest in the brewing science community as well, as last year there were some published studies and conference presentations on the topic.

We haven’t really characterized our isolate of L. thermotolerans yet, so I thought I’d try it out in a homebrew batch. The pre-culture was smelling promising, with a strong fruity aroma combined with a distinct lactic tartness. As I wasn’t sure how the isolate would handle high osmotic stress or high ethanol concentrations, we decide to play it safe by brewing a relatively low-gravity wort. Using a 50/50 blend of pale ale malt and wheat malt, we aimed for a specific gravity of 1.050. As my brew kettle doesn’t fit 30 liters of wort, we decided to dilute the ‘Sour Blend’ portion of the wort with water. Hence we ended up with 15 liters of 1.049 wort for the L. thermotolerans portion, and 15 liters of 1.037 wort for the ‘Sour Blend’ portion.

For hops, we went with some old Saaz hops from 2010 I found in the freezer. We only aimed for a couple of IBUs. The L. thermotolerans portion got an additional handful of Nelson Sauvin hops I also found in the freezer (from 2013, so it had definitely lost some punch) added to it after flameout. We were hoping this would complement the fruity aroma that the yeast seems to produce and add a slight bit of extra bitterness.

After 2 weeks of fermentation (starting from around 19C, rising to around 23C), I transferred the L. thermotolerans portion to a keg for carbonation. The gravity had dropped to 1.011 (for an attenuation of around 78%), suggesting the yeast is capable of using maltotriose. This is quite an important result, as maltotriose is typically the second most abundant sugar in wort. The pH of the beer had dropped to 3.48 and the beer was definitely tasting sour, suggesting that a considerable amount of lactic acid had been produced by the yeast during fermentation.

Overall I’m very happy with the flavour and the aroma. The aroma is very fruity, with hints of stonefruit and tropical fruits. In the flavor there is a nice balance between the fruity and the sour notes. The flavour is also very clean, and with this I mean that there are no strange or off-putting off-flavours. This L. thermotolerans isolate also doesn’t produce any phenolic off-flavours (POF-).

L. thermotolerans is definitely a promising candidate for sour beer production, and I’m sure we will see more acid-producing yeasts pop up in the near future.


Homebrew: Tasting comparison of sour ales

It is finally time to post some tasting impressions of the ‘plain’ and ‘berry’ version of the sour ale I brewed about 1.5 years ago. I’ve had a couple of bottles of both during the winter, and they are interesting beers. I’m not a big fan of sour ale, but I actually like the plain version. The berry version has otherwise been quite nice as well, but it has had a strange aftertaste that really takes away from the drinkability. We’ll see if it is still present in the beer today. I added berries to the majority of the batch (~12 liters), and only bottled six 33cl bottles of the pre-berry version. This was a mistake I’ve now realized, as I’m already down to my last bottle of the plain version. So, note to self: if I ever brew something similar in the future, bottle half the batch before adding any flavorings. All in all it was an interesting experiment, that I hope to repeat at some point. Right now though my priorities are on getting our new homebrewery up and running, so that we can start brewing again. Anyways, let’s see how the sours taste.


Sour Ale
The beer pours crystal-clear (quite a difference to the extremely cloudy wort resulting from the turbid mash) and with a deep golden-amber color (reminds me of apple juice). The aroma is quite tart, with (what I guess is) lactic acid lending the sour tones. There are some fruity tones present as well, which again bring my thoughts to apple juice and cider. A slight funkiness in the aroma as well, but overall it is very ‘clean’ for a (pseudo-)lambic. The flavour is also tart, but by no means as sour as many commercial examples of the style. This one clocked in at a pH of 3.7, which is relatively high for a sour ale. This suits me fine though, as I really don’t like the mouth-drying sourness of some lambics. Tones of apple, grains and slight citrus are present in the flavour. The finish is surprisingly sweet (the FG was 1.010), but it goes well with the mild sourness. This reminded me a lot of a tart apple cider, and I’m actually positively surprised over how this one turned out. A real shame this was my last bottle. How does the Berry version compare then?


Berry Sour
The beer pours clear and with a pretty red color and a pink foam head. While the plain version had a very clean aroma, this one is much more funky. The aroma is more aggressively sour and funky, with a slight cellary/musty twang to it. Behind this, there are very evident tones of raspberry as well. The blueberries are more hidden, even thought I added three times as much compared to the raspberries. The berries are nice, but I think I prefer the clean cider-like tones of the original. The flavour is slightly more sour than the original, perhaps as a result of the added fermentables and the acids in the berries. Raspberry is dominating the flavour, but there are some tones of apple, blueberries and cherry in the background. The aftertaste is drier than the original, and it is unfortunately plagued by a slightly sharp and musty aftertaste. Not really sure what has caused it, maybe mold or the berries themselves? Would be interesting to hear opinions from somehow who actually loves sour beer. Anyways, not a bad beer, but I would find it more enjoyable if it was a little less sour and funky, and the berry flavors were cleaner.

If I were to brew another sour, I would also be more careful with introducing oxygen. The beer had a thick pellicle the whole one-year fermentation (sign of oxygen), and I think especially the berry version might have some tones of acetic acid.

Homebrew: Sour Ale – Bottling and addition of berries

Yesterday, the Sour Ale I brewed in October 2013 had been in the primary fermenter for almost 11 months. I didn’t have enough patience to wait the full year, so yesterday I also decided to add berries to the beer. I had originally planned to only use blueberries, but I ended up adding 2.2 kg of blueberries and 0.8 kg of raspberries. Before adding the berries, I bottled 5 bottles of the plain base beer, so I can use it for later comparisons. The gravity of the base beer had fallen to 1.010, while its ABV% was 4.2%, and its pH was 3.74. Compared to the pH of other commercial sour ales, this beer had a slightly higher pH (I’ve read that first generation homebrewed sours typically don’t get very acidic). This was reflected in the flavour as well, which was acidic and tart, but quite mild compared to the 3 Fonteinen Oude Geuze I had during the bottling session (I pitched the dregs of the bottle into the homebrew as well). Otherwise the flavour was quite clean (i.e. no major off-flavours such as solvents, higher alcohols, diacetyl, chlorophenolics, etc.) and quite cider-like, with hints of apple and funk. It will be interesting to follow how this one evolves and compares with the ‘berry version’. I was quite surprised at the high FG and hopefully I won’t get any bottle bombs (the beer had been untouched in the fermenter for so long that one would think that fermentation would have ‘finished’). I ended up adding around 300 g berries / liter of beer, so they will hopefully contribute with a lot of flavour! I plan to bottle the ‘berry version’ in around 3 months time.

Here is a picture of the pellicle prior to bottling around 1.7 liters of the base beer:


The beer had cleared really nicely under the pellicle. Unfortunately it was lacking carbonation and was warm for the taste sampling, but despite this it was tasting promising.


I used frozen Finnish berries. I added them frozen directly to the beer.


Here is the 3 Fonteinen Oude Geuze I had while bottling. I added the dregs from the bottle to the homebrew.


Here I am adding the berries through a sanitized funnel.


This is how it looked once all the berries had been added.


Homebrew: Sour Ale Update

I brewed a turbid mashed Sour Ale about 8 months ago, and it has been in the fermenting vessel untouched ever since. I still haven’t taken any samples from it, as I am afraid to introduce oxygen into the vessel (which could result in the production of acetic acid). Two months after brewing, a nice pellicle had already formed. Six months later, the appearance hasn’t changed much. The biofilm has taken on a slightly whiter appearance, and the size of the bubbles has decreased. After summer, I will add some blueberries and raspberries together with some dregs from a couple of 3 Fonteinen bottles. Will be interesting to try it (even though I’m not a large fan of sour beer)!


Homebrew: Blueberry Sour

Today I brewed a small batch of something a bit different. I made an attempt of brewing a sour ale / pseudo-lambic. The malt bill was simple, containing 2 kg of pilsner malt and 1 kg of raw wheat. The mashing was however a bit more complicated, as I attempted a turbid mash. The turbid mash results in a starch-rich wort, leaving some food for the pitched bacteria once the yeast has consumed all the simpler sugars. The mash procedure was as follows (12 liters of mash water and 3 kg of grain):

  • 2.4 liters of 65C water was added to the grain, resulting in a mash temperature of 45C. The temperature was held for 15 minutes.
  • 2.4 liters of 85C water was added to the mash, resulting in a mash temperature of 52C. The temperature was held for 15 minutes.
  • 1.6 liters of wort was transferred to an empty kettle, and temperature was raised to 88C.
  • 3.6 liters of 100C water was added to the mash, resulting in a mash temperature of 65C. The temperature was held for 15 minutes.
  • 3.4 liters of wort was transferred to the kettle already containing wort, and the temperature was again raised to 88C. Total volume in kettle now 5 liters.
  • 3.6 liters of 100C water was added to the mash, resulting in a mash temperature of 72C. The temperature was held for 30 minutes.
  • The mash tun was drained, and the wort (~7 liters) was transferred to the kettle, and the temperature was again raised to 88C.
  • The grains are rinsed with the 88C wort, resulting in a mash-out temperature of 78C. The temperature is held for 20 minutes.
  • The wort was transferred to the boil kettle, and the grains were batch sparged with 10 liters of 78C water.
  • The sparged wort was then added to the boil kettle, resulting in a pre-boil volume of around 22 liters.

After the mash I boiled the wort for 2.5 hours (in order to reduce the 22 liters of ~1.025 pre-boil wort, into 15 liters of 1.040 post-boil wort) together with 20 grams of old Saaz hops. The hops (2010 harvest) have been in an opened package in the freezer for over a year, so their alpha acid content is presumably below the 3.1% stated on the package. In a sour ale you want to keep the iso-alpha acid concentrations on the low side, since they inhibit the growth of lactic acid bacteria. After the boil I chilled the wort and pitched a pack of Wyeast’s Lambic Blend. I will leave the wort in the fermenter for around 9 to 12 months, after which I will add 2 kg of blueberries and bottle dregs from two bottles of 3 Fonteinen Oude Geuze. I’m expecting to bottle this one in around 12 to 15 months.

I was mashing in my 21 liter kettle and a BIAB-bag (this helped when pulling the liquor from the mash).


The yeast and the hops. Hopefully I haven’t overdone the hopping.


I’m using a glass carboy for fermentation, in order to reduce the amount of oxygen that comes into contact with the wort/beer during the long fermentation.


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