As homebrewers, we are faced with a multitude of potential conflicts and schedule changes that can affect our brewing plans. How often have you had everything ready for a Saturday afternoon brew session with your grain bill milled, your yeast starter ready and even your brew day music picked out and then, out of nowhere, your spouse, work, weather or a child’s ball game changes your plans? If you use dry yeast, that doesn’t require a starter, that isn’t a problem but if you use liquid strains you need to ask yourself some questions. When will I be able to reschedule? What about my active yeast starter? How long can I wait before my yeast goes dormant? What happens if my brewday gets interrupted yet again? While you can’t control the weather, the kids, or work conflicts, you can eliminate the worry about your starters going dormant by using a German yeast propagation technique called drauflassen.
With the drauflassen technique you can use liquid yeast, without having to make a starter several days in advance and still pitch at a healthy rate. You can even have impromptu brewing sessions and not have to plan your brew day around your starter or even use a stir plate. Sounds perfect doesn’t it? Well, many breweries do just that and are often forced to use this technique to make big lager pitches. Here’s how you do it.
Drauflassen means “to flow onto”. In a commercial brewery setting, when new yeast is introduced into the brewery, it may take many gallons of yeast slurry to achieve the proper pitching rate. It might take 5 gallons of slurry to make a 3 barrel(90 gallon) batch. Imagine how much yeast it takes to ferment 50 barrels(1500 gallons)! Yeast can be expensive and the brewery may simply not have the capacity to propagate yeast in-house. What do they do?
The process begins by making a small, pilot batch(20%-30% of the total fermenter volume) and then pitching the new yeast at the proper fermentation temps for that strain. While that process is underway, they immediately brew another batch of the same beer but this time they are brewing a full capacity batch. Sometimes this is called double batch brewing. As soon as the pilot batch reaches the peak of the yeast growth phase(krausen just forming), they add the full capacity batch and allow it to “flow onto” the pilot batch, just before it begins to attenuate. The result is a healthy pitching rate and a very active fermentation for the entire batch volume. You say, that’s great, but I only make 5 gallons, not 5 barrels. Well, this technique works equally well for homebrewers.
You can apply the same principles to any 5 gallon batch, including lagers. Lagers require very large starters and this method is similar to making a small beer just for the purpose of yeast propagation. No changes are needed to your recipe. The only additional equipment you will need is a separate vessel to ferment your “pilot batch” such as a carboy, erlenmeyer flask, plastic fementation bucket or even a gallon pickle jar. You are going to brew your batch just as you normally would and chill to pitching temps. When you arrive at pitching temps, you want to drain about 20% of your batch volume into your, meticulously cleaned and sanitized, pilot batch vessel. Extra attention should be paid to your sanitation regimen when using this technique. The pilot batch should then be handled just as you would any other batch. Aerate, pitch your yeast and control the fermentation temperature. The remaining wort should be drained into your regular, carefully sanitized, fermenter. Again, sanitation is critical because the remaining wort will be sitting, without the benefit of yeast to out-compete bacteria and other organisms, for up to 24 hours. Keep this wort at your desired fermentation temperature as well since you’ll be adding the contents of the pilot batch to the main wort within a few hours. When you first begin to see signs of krausen forming in the pilot batch and bubbles start to break the surface, gently swirl the pilot batch and carefully pour the entire contents into the main wort. You can now aerate the entire wort with pure oxygen or a mechanical aeration device. Beyond that, the process is the same as any other batch and you should achieve the same results as if you had made a starter prior to brewing.
It’s that easy. No starter, no planning, no worries- no problem!