Seeing some lovely Krausen on the brew tonight I couldn’t help but harvest some more yeast to add to yesterday’s bounty, which had settled down to a disappointingly paltry film at the bottom of its glass jar since I liberated it yesterday. Dropping the pressure briefly from 5 PSI to zero resulted in some bubbles rising to the top and also out of the dip-tube, so I can only hope the yeast and (more importantly) the Tilt Pro is happy being de- and re-pressurised so rapidly.
On refitting the spunding valve after cropping I took the opportunity to increase pressure to 10 PSI, based on positive feedback from others who have done the same with their Kveik.
With fermentation finally underway I wanted to have a go at top-cropping some yeast for the first time, and also start to apply a little pressure, just in case whatever’s caused my yeast to have such a delayed start might have further impact on the brew by producing off flavours. This is however supposed to be a malt-forward brew and I therefore don’t want to kill those esters altogether, so I’m going to leave it at 5 PSI for now.
On the cropping front I only managed to get a very small amount of yeast. David Heath reckons you’re supposed to steer clear of the FV sides and avoid any foam that’s turning dark brown, so all I managed to do is grab a very small amount from the middle of the Fermzilla’s foam hat. There isn’t enough to even think about using it for a serious brew, but I think I’ll play around a little bit and see how much I can grow it using a starter, maybe then add it to a kit brew instead of the included yeast.
As a parting note for tonight; I hope I haven’t killed fermentation by temporarily adding 10 PSI from the CO2 tank so that I could check the spunding valve was correctly set. Kveik is supposed to be as resistant to pressure as it is to temperature, but as soon as I swapped the airlock for a spunding valve the turbulence below the surface all but stopped. I’m sure it’ll be off again by morning …
The temperature has been increasing steadily with fermentation and sunny weather. I was hoping to keep it around 19℃ which is the optimum for the WLP001 yeast I’m using (range: 19 – 21℃) and really need to get myself a fermentation fridge so that I can control this better. This beer doesn’t really need esters and it certainly doesn’t need fusel alcohols, so I’ve no hesitation in applying some pressure to the fermentation after 24 since kick-off.
Speaking of fermentation, it’s not been a quick starter, with the first signs of life in the airlock showing maybe 4 or 5 hours after pitching both tubes of liquid yeast. I was beginning to get worried; one of the ice packs that accompanied the yeast on its voyage over to us had become punctured by something else in the box, and I had doubts whether or not the yeast had really been kept at 4℃ all the way as intended. Things did start happening that evening, and by morning there was a thin layer of foam on top, maybe ¼ inch thick, with the usual frenzied activity going on underneath.
By noon that had increased to almost an inch, and when we came back from an afternoon walk we swapped out the airlock for a spunding valve set at 10 PSI. This had a dramatic effect on the foam, which transformed into a thick Krausen over the next few hours, almost touching the vessel’s lid by evening. To save the spunding valve I decided to move it to a spare keg and then connect that to the Fermzilla with a blow-off tube, but forgot to pre-pressurise the keg and caused much of the Krausen to head straight down the tube as soon as it was connected. I removed and cleaned the tube just in case, must remember to do the same for the Fermzilla’s PRV once this is done.
Golden Wave has been fermenting for 38 hours now. The wort appears to be very active underneath its blanket of Krausen, which is between 1 and 2 cm thick and a variety of colours, from almost white to a dark beige.
Data from the Tilt tells me that the temperature inside the Fermzilla is 2 ℃ higher than room temperature and still climbing, and since I don’t have a dedicated brew fridge yet I’m switching to pressure fermentation 10 hours earlier than planned in order to limit the production of esters and off flavours. Spunding valve added 09:10, 50 minutes later we’re already at 8 PSI. Capping it at 10 PSI.
After reading an interesting article by Scott Janish I decided to start pressure fermenting a little earlier than originally planned with this brew. Scott also thinks that pressure inhibits the release of esters and fusel flavours and makes a case for pressure fermenting right from the start, but what’s interesting here is that there’s also a suggestion that some of the hops’ oils are lost along with the CO2 in unpressurised fermentation. Keeping that hoppy goodness locked in is one of the main goals for me, so I’m wiling to gamble a little with potential loss of mouth-feel and maltiness (which my brews to date have in abundance) in return for a little more hops. I therefore decided to ditch the airlock just 24 hours into primary and fit my new spunding valve instead.
The whole process was very easy; just unscrew the cap with the airlock, fit a freshly sanitised carbonation cap, click on the spunding valve kit. Rather than letting the pressure build naturally and then knock it back, I decided to add CO2 via the dip tube allowing me to adjust the spunding valve there and then, settling on 10 PSI for now.
I did have some concern about the building Krausen getting into my shiny new valve and briefly toyed with the idea of patching the Fermzilla to a spare keg and then fitting the valve to the keg instead, but I needn’t have worried: within 30 minutes of adding pressure the Krausen has retreated significantly and continues to shrink as I write. I believe this is another expected positive side-effect of pressurised fermentation which allows brewers to get better returns from smaller vessels including Cornelius kegs, since less room is lost to head-space.