Monthly Archives: March 2015

Brewing at J’s homebrewery

On Sunday I had the chance to brew beer together with my colleague J at his homebrewery. He has some really cool ‘homemade’ equipment, which allows him to brew up to approximately 140-liter batches of beer. He has been brewing mostly Sahti (which you will notice from the equipment as well), but on Sunday we decided to brew an easy-to-drink Pale Ale hopped with Cascade. We aimed for an ABV around 5% and an IBU of around 35, in order to appeal to as large of an audience as possible (J is planning to serve it at a friend’s party). The malt bill consisted of mainly pale ale malt, together with a small amount of munich malt (to give some strength to the malt backbone) and crystal 10 (to lend some body and a slight hint of caramel). The hop schedule should give the beer plenty of grapefruit and floral tones in the aroma and flavour. We are fermenting with J’s ‘house’ (or shall we say favourite) yeast strain, WLP007, to lend a dry and clear beer, with slight hints of fruity esters. The batch size was 100 liters, so approximately 2.5-5 times bigger than my usual batches. The brewday went really well and we hit most of targets. Hopefully the beer will taste good as well! Thanks J for the opportunity to come and brew with you! Below you will find some pictures I took during the day.

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We began the brewday by crushing the malt, which J had pre-weighed prior to my arrival. He uses a mill that looks quite similar to my Monster Mill MM-2. Crushing 20 kg of malt took about 10 minutes with a cordless drill.

While we were crushing, the mashing water was being pre-heated in the 200-liter brewing kettle. J has modified a 200-liter tiltable kettle (normally used in professional kitchens) with a PID controller, which allows him to precisely control the mash temperature. The kettle is powered by a steam jacket, which allows for rapid and even heating along the whole surface of the kettle (no problems with scorching here). He has mounted a motor-powered mash paddle in the middle of the lid (which was continuously mixing the mash), together with a long thermowell containing the temperature sensor. A really cool set-up! Hopefully will be able to have something similar at some point.



Below is the lautering vessel, which is of the kuurna-type, i.e. one that is traditional used for making sahti. When making Sahti, the vessel can be filled with juniper twigs to help with lautering and to lend some flavour. We instead used sheets of perforated stainless steel to act as a false bottom and uphold the malt bed.


After the 90-minute mash, we transferred the whole content of the kettle into the lautering vessel. We used smaller buckets for the transfer, which took a couple of minutes. The engineer in me would probably want a more automated and less laborious solution, but J was happy with this set-up. When the kettle was empty, it was quickly rinsed with water, after which the sparge water was heated. In the meanwhile we were circulating the wort in order to clear it up. No fear of hot-side oxidation here, with plenty of splashing. I would again probably take an easier way out, with a valve in the end and a pump to recirculate the wort.


Here is a picture of the control panel as we are heating the sparge water up to the target temperature of 75C. It took maybe 10 minutes to heat the 70 liters of sparge water the remaining 30 degrees up to 75C.


Here is a picture of the exhaust system. He uses the same exhaust fan for leading away welding fumes, so it serves several purposes. It was very effective in removing the steam produced during the boil (which you will see a couple of pictures down).


We collected the pre-boil wort in the kettle. We ended up with around 120 liters of wort, with a pre-boil gravity of around 1.042 (so slightly higher efficiency than expected).


After the boil had started, we opened up the hole in the lid, added in the bittering hops, and put on the exhaust fan. As you can see, the fumes are collected nicely into the ventilation tubes.


Here are 150 g of Cascade pellets which are to be added with 15 minutes left in the boil. The remaining 250 g of flame-out hops are still waiting in the black bag.


Below is 175 ml of WLP007 yeast slurry which is to be pitched into the wort after cooling. Slightly on the low side for this big of a batch, but luckily the beer is quite low-gravity.


Here we are cooling through a plate chiller. No pump is used to transfer the wort, only gravity (the kettle is tilted so the valve is lowered below the liquid). Emptying of the kettle took about 15-20 minutes. Before cooling we whirlpooled the hot wort for around 15 minutes, to collect any solid matter at the bottom. The whirlpool was initiated with the same motor-driven mash peddle which stirred the mash.


Here is a picture of the whirlpool cake. Quite a lot of hop debris and trub!


We ended up with around 100 liters of 1.048 wort. This will hopefully become a really refreshing and sessionable Pale Ale for warm spring days!


Thanks again J!

How new yeast species are inspiring a revolution in brewing

Note, this is a repost of an article I wrote for VTT’s Industrial Biotechnology Blog.

Lager beers – sometimes crisp & light pilsners, sometimes dark & malty doppelbocks, have a common denominator: They are all produced using the lager yeast Saccharomyces pastorianus, the workhorse of the lager brewing industry. This yeast is known for its tolerance to lower temperatures, and brewers take advantage of this when producing lager beers.

These beers typically have a ‘clean’ flavour profile (i.e. lack of yeast character) you see, and by fermenting the beer at colder temperatures, the yeast produces less flavour-active by-products.


Recent analysis of lager brewing yeast genomes has revealed that the many hundreds of strains used in the brewing industry are, in fact, all closely related – more like multiple variants of the same strain than individual strains. Brewers have essentially been using the same strain to brew lager beers for probably 500 years. This is in stark contrast to the other fermented beverage industries, ale, whiskey, wine, cider and so on, where a rich and diverse collection of individual yeast strains is taken for granted.

Therefore, there is huge potential for introducing diversity into the lager brewing industry by generating new strains of lager yeast.

But before one can create new lager yeast it is important to understand what exactly the lager yeast is…

It has been known for some time that lager yeast is actually a hybrid species – more like a mule than the proverbial workhorse. It was clear that one parent was the well-known ale yeast Saccharomyces cerevisiae. It wasn’t until recently that the other side of the family, Saccharomyces eubayanus, was discovered. This discovery has allowed for the improved characterization of lager yeasts, and also opened up the possibility to create new tailor-made lager yeast strains. This is possible through mating of selected strains from the two parent species. These new strains could, e.g. produce unique flavours or ferment the beer more efficiently.

This is exactly what has been the focus of our ongoing research projects at VTT.


The research team. From left to right: Brian Gibson, Kristoffer Krogerus, Virve Vidgren and Frederico Magalhães in VTT’s pilot brewery.

Screening perfect parents to mate

There are four main challenges in generating new lager yeasts: To select suitable parent strains. To get the parents to mate. To separate the hybrid cells from the parents. And finally, to confirm that they actually are hybrids.

We began by screening a range of ale yeast strains, from both VTT’s Culture Collection and commercial yeast suppliers, for beneficial fermentation properties. Once suitable parent ale yeast strains had been identified, the next step was to try to mate them with a strain of S. eubayanus, the other parent of lager yeast.

Before mating, the parent strains still had to be modified with selection markers, so that any hybrid cells could be isolated from the population. We did this by selecting spontaneous auxotrophic mutants of the parent strains, i.e. cells that weren’t able to grow on media lacking certain amino acids. This meant the hybrid cells could be selected by their ability to grow on media lacking these certain amino acids. Mating was then attempted by simply mixing populations of both parent strains, and letting them grow for a couple of days.

Seub_cells© VTT/Ulla Holopainen

After isolating some potential hybrid cells, their hybrid status was confirmed through various PCR tests, which showed whether DNA from both parent strains was present in them. After confirmation that we had produced our own lager yeast hybrids, we wanted to compare them to the parent strains in an actual wort fermentation.

To our pleasant surprise, all hybrid strains performed better than both parent strains, fermenting faster and reaching higher ethanol contents!

The hybrid strains also inherited beneficial properties from both parent strains, such as strong flocculation, cold tolerance and maltotriose utilization.

These first results suggest that this technique is suitable for producing new lager yeast strains with unique properties. These new strains also have the benefit of being non-GMO, which currently at least remains a necessity for brewers.

We are continuing our attempts to find and create perfect lager yeast hybrids at VTT. Our research will especially pay attention to flavour formation and determining how their genetic composition is reflected in their physiology.

Our work will show, for the first time, that such hybrids can be created and how they can be applied in the brewing industry. The results will appear shortly in the Journal of Industrial Microbiology and Biotechology:

Krogerus, K., Magalhães, F., Vidgren, V. & Gibson, B. (2015) New lager yeast strains generated by interspecific hybridization. Journal of Industrial Microbiology and Biotechnology, in press. DOI:10.1007/s10295-015-1597-6.

Maybe someday also you have an opportunity to enjoy these new tasty lager beers in your local pub. Cheers!