Flanders Red–Belgian Sour Ale

We recently moved our homebrewing to a whole new level. We’ve made many ales, a few lagers, but never a sour beer.

To get started we used a recipe for a Flanders Red Ale from Brewing Classic Styles by Jamil Zainasheff. This is basically along the lines of the beers made by Rodenbach in Roeselare in Belgium. The beer is fermented with both yeast and various bacteria strains that give the distinctive sourness and complex flavours.

So what’s different from the way you make a regular ale? Well, firstly you need the right combination of both yeast and bacteria. One of the reasons we chose this recipe is because you can get the whole lot blended in one pack from WYeast, called, funnily enough, “Roeselare Blend”.

What else? Well the fermentation lasts for a year. Initially the yeast ferment most of the sugars, then over the remaining months the bacteria consume what is left. The different types of bacteria produce both lactic acid, which gives a soft sourness, and acetic acid (vinegar), which gives a sharper sourness. It is important to get the balance right – too much acetic acid will make the beer challenging to drink. Both temperature and oxygen levels affect the level of activity of the different bacteria strains. What we need to aim for is a small amount of oxygen, and a moderate temperature (18C – 20C) to give a steady fermentation.

If you ferment the beer in a plastic fermenter (aka bucket) you get oxygen going into the beer: plastic is permeable to oxygen. So you need to ferment in glass rather than plastic. So I invested in a 6 gallon carboy. (This is a bugger to move around – it’s heavy and would smash or chip very easily!)

You’ll see in the photo that we used an oak peg rather than airlock (custom made by Andy’s personal cabinet maker – yes, really, every gentleman should have one!). This, we understand from Mr Zainasheff, will allow just the right amount of oxygen into the beer to emulate the oak barrels used by commercial breweries.

Anything else different? Yes, we also used toasted oak chips, which again emulates the oak barrels used by commercials breweries.

As the beer ferments it is supposed to form a pellicle on the surface. This is a grim-looking white mat produced by the bacteria. Have a look here for the sort of thing I mean. This hasn’t happened yet – at the moment the fermentation is too active and the surface too bubbly (see the last photo below).

Apparently the pellicle sinks back into the beer when the fermentation is done. This is the cue to rack and bottle the beer, but takes a year or so.

Below are a few more photos from brew day. I guess I’ll post again about it, but not any time soon!