Posts Tagged ‘liquid yeast’

Ok, I’ll apologise straight up for the blog title, but surely it’s better than “Fenomenal Fermentations”?  I suppose I could have gone with “Fabulous Fermentations”, but as an adjective it does seem to have been somewhat hijacked these days…

Perhaps as a subtitle I could use “You can ferment a lager in only 5 days!”, as that’s pretty much the driving reason behind this update.  I have been enjoying the success of my fermentations lately, probably for the last 4 months or so.  My lag times have been significantly reduced, with most of my brews showing activity and producing krausen only 6-8 hours after pitching.  And I’m reaching final gravity in 3-5 days, depending on the strain of yeast I’m using and the original gravity of the wort.

And most importantly, I believe the quality of my beer has noticeably improved as a result.  I’m convinced there’s a number of different factors at play here, each of which is playing their part in the success.  I’ll list each component in detail;

Dry v Liquid Yeast:

I’ll discuss this in more detail below, but basically dry yeast has a significantly longer lag time than liquid yeast…as long as they’re both pitched at the correct rate (again see below).

Aerating the Wort:

This is not something I did much (if any) of early on in my brewing.  I didn’t even know it was a “thing” until I’d made quite a few batches, and even once I did, all I started doing was to splash my cooled wort as much as possible when transferring it into my primary fermenter.  I’d also read that you didn’t need to aerate when using dry yeast, as they were manufactured in such a way that they had all the oxygen they needed already.  To quote Fermentis: “As the yeast is grown aerobically, the yeast is less sensitive on first pitch“.  And Danstar: ” Most commercially produced Active Dry Beer yeast actually require no O2 addition for a successful average gravity wort fermentation

But then I started to move to liquid yeast, and around the same time I started no-chilling a lot of my beers.  And I realised that I could use the no-chill cube to vigorously shake the wort (after pouring off the first few litres) and add some oxygen that way.  And then it struck me that I could also use my power drill and mash paddle to agitate the wort even further, so I started doing exactly that.  Power drill on its highest speed, mash paddle sprayed down with Starsan, and have at it!  It does a surprisingly good job of frothing everything up, and while I’m sure it’s not as effective as using an oxygen stone, it has definitely helped.

Yeast Pitch Rate:

I guess in hindsight this one should be pretty obvious, but it’s definitely something that’s hard for new brewers to get right.  Especially when using dry yeast, as nobody seems to pay much attention as to how many viable cells are contained in a pack of dry yeast…it’s rarely even written on the pack, and of course packs come in varying sizes too.  And then there’s the whole argument about hydrating yeast vs sprinkling it dry….I’ve done both and couldn’t really tell any difference in lag time or fermentation quality.

I understand that the ‘normal’ 11.5gm packs of dry yeast from places such as Fermentis and Danstar have 200b cells at the time of packaging, and if they’ve been handled correctly (i.e. refrigerated) they should have lost very little viability by the time you pitch it.  So because the “average” 19 litres of 1.048 gravity wort needs about 170b cells, pitching a pack of dry yeast on that means you should be getting it pretty right.  Of course that all changes when you decide to make 23 litres of 6.5% IPA, which would need something like 250b cells for an ‘optimal’ fermentation.  Conversely you might decide to make a small 10 litre batch of something as an experiment, it seems most brewers elect to pitch an entire pack regardless, as you can’t easily (and hygienically) measure out portions of dry yeast…and what would you do with the leftovers anyway?

This is one of the reasons I moved to liquid yeast…once I’d become more comfortable with yeast handling, after a few top cropping and yeast rinsing experiments, I realised that liquid yeast would give me the opportunity to start a bit of a yeast bank.  Despite the fact that liquid yeast is roughly twice as expensive, for half the amount ($10 for 100b liquid cells vs $5 for 200b dry cells), you can use the “yeast starter” process to grow your yeast into more than what you need for your batch, and save the extra for another brew down the track.  For example, if I need 160b cells of 3068 for a hefe, then I make a starter with my pack of 3068 that results in 260b cells, then pitch 60% of that into my hefe, and store the remaining 40% (~100b) away for next time (labelling the container with the amount and date the starter was complete).  Then I can repeat that process many more times, spreading the cost of the original packet over many batches ( I’ll probably stop after 4 or 5 batches and start again with a brand new pack).

So the use of liquid yeast now allows me to more accurately control how much yeast I’m pitching on each batch, with the help of my favourite yeast pitch rate calculator.  This is important not just for ensuring optimal fermentation, but also allows you to control the flavours driven by some yeast strains.  The perfect example is the 3068 I mentioned above, Wyeast’s “Weihenstephan Weizen“.  I have found deliberately underpitching this yeast by around 20%, in combination with fermenting at 17C, leads to the exact flavour profile I get from my favourite commercial weizens.

Fermentation Temperature:

This is one of the first things serious home brewers discover on their journey to make better beer, and I’ve discussed it on this blog before, so I won’t go into much detail.  Just a reminder that the ability to temperature control your fermentation is a critical part of the process.  An old fridge coupled with an STC-1000 and a 100w floodlight (or some other heat source) is all it takes.

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My fascination with Bavarian wheat beer styles continues, and after a few goes using Fermentis’ WB-06 dried yeast, I decided to give liquid yeast a run.  There are literally hundreds of strains of liquid yeast available to home brewers, compared to perhaps a dozen or so dry yeast strains.  The one that seems most popular for weizen brews seems to be Wyeast’s 3068 (Weihenstephan Weizen).  So this is where I started.  I was looking to produce a beer with the smooth taste you get from a commercial hefe, such as the Weihenstephan & Paulaner weizen range.  My WB-06 brews, while good, were coming out more ‘tart’ than I was expecting, even at the higher ferment temperatures.

I decided to make my first batch with liquid yeast a dunkelweizen, as my first dunkel is nearly all gone anyway.  My plan was to make two small batches of the same dunkel, changing only the fermentation temperature.  This is because I’ve read various reports on the web regarding the flavours imparted by 3068 at different temperatures.  Some swear a higher temp such as 23C will give solid banana esters, while others say 3068 is (surprisingly) best fermented at 17C.  Having now read Chris White’s “Yeast” book cover to cover, it also pointed out that under-pitching yeast into wheat beers can produce desirable results, as the stress this puts the yeast under (to reproduce quickly and significantly) can also produce these esters.

Yeastcalc showed me that the “optimal pitch rate” for 11 litres of 1.050 ale was 102 billion cells.  I decided to underpitch around 80 billion into this dunkelweizen.  My smack pack of 3068 was a couple of months old, so around 70% viability, and I was splitting the pack across the two batches, so starting with roughly 35b live cells.  Yeastcalc told me I’d need a 1.5l starter to achieve 80 billion cells.  So a couple of days before I was planning to brew, I smacked the pack and waited for it to swell, then poured it into a sanitised jar.  I boiled up 1.5 litres of starter using some DME, and after cooling, pitched it and half the yeast into a 2 litre mason jar, covering it loosely with sanitised foil (gotta love that Starsan).  I let it sit for 24 hours, swirling it occasionally.  Then I put it in the fridge for 24 hours to allow the yeast to settle out to the bottom of the jar.

On brew day, I brewed the dunkel then took out the yeast starter from the fridge.  You could see a thin white layer of yeast at the bottom of the jar.  I decanted the wort off the yeast, leaving just a little in the bottom, which I swirled to make a slurry.   Once at room temp, I pitched it into my dunkel, and put it in the brew-fridge at 23 degrees.  After a couple of days the smell was pretty impressive, plenty of banana aroma as I’d hoped.  It was similar a week or so later at bottling time, so I was looking forward to the first tasting after a couple weeks of bottle priming.

However, upon first tasting, it has a very similar tartness to my WB-06 brews!  I was surprised by this, thinking it would be a lot more like the commercial weizen beers.  The beer was good, marginally better than my first dunkel, but nothing like a Weihenstephan hefe.  I had read on the web where some brewers thought wb-06 was just a dried version of 3068, but it seemed to have been disproved.  Now I’m not so sure.  However, I will continue the experimentation and put another dunkel down soon, this time fermenting at 17C to see what, if any difference that will make.