Posts Tagged ‘fermentation’

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.