Yeast: Brasserie de la Senne

A few weeks back I was lucky to spend a great deal of time in Brussels. The city is fantastic if you have never been. It embodies many of my favourite things – beautiful shopfronts, cultural diversity and fantastic beer.

On the latter, I found it surprisingly easy to locate beers from Brasserie de la Senne, another one of my large inspirations.

If you have never heard of Yvan de Beats & Bernard Leboucq or their brewery, then I would take a second to google their story. Bernard is an established brewer and the creator of the Brussels favourite Zinnebir. Yvan is known to many brewers around the world not only for his beers but also his historical work. In the book Farmhouse Ales by Phil Marowski, Yvan wrote an essay on the history of saisons. He has written and spoken on this and related subjects around the world. Just by googling his name you get a sense of his impact. Brewers like Chad Yakobson from Crooked Stave cite Yvan as the source on all things yeast and saison. Basically, Yvan wrote the book on saison, and he also wrote the book. For more information on them or their brewery, this article is a good place to start.

Very impressive head retention!

For me, walking into Brasserie de la Senne a few Mondays back was like an art history student visiting the Prado. On that day I was lucky to catch Yvan in-between meetings and get a quick tour of the space and chat about yeast for a bit. These were precious moments for me and there is one stand-out differentiating factor that I learned worth sharing here. Yvan and Bernard have designed their entire brewery around yeast. From the smaller, sometimes common things such as having equipment set up for step mashing and bottling conditioning to the larger and completely unique fermentation vessels.

Their wide, shallow fermentors

Pictured above, these custom vessels are designed specifically to keep excessive hydrostatic pressure off of their yeast. Hydrostatic pressure is similar the pressure felt at the bottom of the ocean. In brewing, it describes the pressure felt by the yeast and beer at the bottom of a tank in respect to that at the top.

This pressure has negative effects on the long term health and viability of the yeast as well as ester production (see this). In very tall cylindroconical fermenters the yeast at the bottom experiences huge pressures that can rupture the yeast cell walls and rapidly decrease cell viability. In order to combat this in long term yeast harvesting and repitching, a brewer must collect his yeast as soon as they can. This is a relative description because each brewer has a different reason to collect at the time they do as their own balance between the amount of yeast to collect and its viability.

Not only does a premature collection of yeast pull out cells still working on attenuating a beer, but also it biases the lower attenuators who do their work and drop out. Within each strain there are certain cells that get eating away and once they are done fall to the bottom. Others work slower on the wort gradually consuming available sugars and don’t flocculate to the bottom until there is nothing else left. By cropping your yeast early, you select the faster working ones that are more reluctant to stick around and make that beer nice and dry.

These tanks, as you can see, are pretty space costly and would be difficult to fit a whole bunch of them in any area to meet a larger production demand; however, de la Senne solves this problem in a rather clever yet traditional way. Instead of allowing primary fermentation in a single vessel and then moving to a conditioning tank for a few days, they carry out their primary ferment for 4-6 day in their custom tanks and then move the beer to a colder storage area into their garde (storage) tanks for two to three weeks. While it sounds more like a lager approach, recall brasserie Thiriez had a similar approach to allow for the continual fermentation of their beers creating drier and more balanced flavours.

Its a slow process and one certainly born of respect for their yeast as the maker of their beer. If you get the chance to visit Belgium, de la Senne is a worthy stop. If not, word on the street is they are increasing brewing capacity in a big way in the next 18 months so hopefully that means a little more for the rest of us!

I loved this sticker