This week I check out fermentation issues when brewing a really excessive gravity beer resembling an Imperial Stout or Barley Wine. Final week in Half 1, I lined a number of strategies for reaching a really excessive beginning gravity.
Choosing Your Yeast
Now that you’ve got a excessive gravity wort, it’s worthwhile to think about how you’ll ferment it in a constant method to realize your goal ending gravity. One of many worst issues that may occur with a excessive gravity brew is a caught fermentation the place the ultimate gravity is simply too excessive and you find yourself with a sickly candy mess as a substitute of the properly balanced beer you have been capturing for.
Step one in that is yeast choice. You wish to choose a yeast pressure that has each a excessive alcohol tolerance and good attenuation. All yeast strains have a restricted alcohol tolerance, and lots of beer yeast strains can solely deal with 8-10% alcohol. That is clearly an issue if you’re making a 12-15% stout or barley wine. So its time to really do a little bit of analysis and pull up the yeast specs on the net.
Ideally you desire a yeast can deal with greater alcohol, one thing within the 15%-18% vary. Many of those yeasts are wine or champagne yeasts, and these yeasts are sometimes fairly appropriate for beer. Nevertheless, some Belgian yeasts in addition to some California ale yeasts can attain into the 13% vary.
Hand in hand with this it’s best to take a look at the attenuation of the yeast pressure. Greater attenuation yeasts will ferment a better proportion of the out there sugars and sometimes achieve this extra cleanly with much less stress.
Pitching and Early Fermentation
While you pitch yeast into a brand new surroundings it takes a while to acclimatize and start to correctly regulate the membrane on the mobile wall. That is significantly true for dry yeast which has to each hydrate and regulate itself in a really quick time period.
At extraordinarily excessive gravities, one other concern is osmotic shock, which I detailed on this article. In very excessive gravity beers the sugar focus of the wort will be so excessive it could truly trigger the cell wall to fail earlier than the cell has time to regulate, leading to a excessive mortality fee on your pitched yeast. The answer as outlined within the linked article is to take time to hydrate dry yeast and likewise slowly introduce wort to your yeast so it has time to regulate to the complete gravity.
One other consideration is aeration. Due to the excessive gravity, the yeast wants as a lot oxygen throughout early fermentation as attainable. I like to recommend aerating your wort utilizing pure oxygen or an oxygen wand earlier than pitching your yeast. As well as, for beers above 1.080 in beginning gravity it is extremely frequent so as to add a second dose of oxygen about 12 hours into the fermentation. The double dose of oxygen aids in fast yeast enlargement in the course of the early development section.
Good temperature management can also be vital, significantly throughout early fermentation. Due to the excessive gravity the fermentation can run scorching and in the event you don’t management the temperature it can lead to greater manufacturing of fusel alcohols, esters and different off-flavors.
Fermentation and Growing old
Assuming your fermentation went properly, the subsequent consideration is getting old your beer as most excessive gravity kinds require in depth getting old. The very first thing you wish to do is be sure your fermentation is actually full with a secure last gravity that doesn’t change over a interval of a number of days. I additionally like to go away my beer within the major fermenter till many of the yeast has fallen out. You may help this precipitation by chilly crashing your beer as soon as you’re sure fermentation exercise has ended.
As soon as the yeast has fallen out you will need to separate the yeast from the beer, as prolonged getting old over a interval of months can result in off flavors if left on the yeast cake. On a conical fermenter this is so simple as drawing the yeast from the underside of the vessel, however if you’re fermenting in a carboy or bucket you will have to switch the beer to a secondary fermenter or barrel if you’re barrel getting old.
HIgh gravity beers usually require in depth getting old. Ideally you wish to keep away from any oxygen throughout getting old and preserve a managed surroundings for the beer. For barrels it’s a good suggestion to periodically prime up the barrels with beer to exchange the “angels share” that evaporates via the barrels.
It is extremely frequent to add spices or mix the completed beer. As a result of very excessive ending gravity, a uncooked Barley Wine or Imperial Stout can usually be too malty or candy. To attain correct stability you want tannins and acids from oak, wooden, spices and darkish malts.
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