Friday, 27 June 2014

Yeast Experiment

Primarily we are trying to focus on the ester development potential of the various ale yeasts.
Secondarily, we will record the attenuation % for each yeast at a set temperature and wort oxygen level..

Some yeasts are reported to give similar ester profiles, but the attenuation can vary substantially. For
example, WLP002 ESB (used by Fullers) has a reported attenuation of 70%. WLP005 British Ale and
WLP007 Dry English yeasts are supposed to have a similar ester profile, BUT they attenuate at 75% and
80% respectively.
Mash temperature can affect the wort attenuation and we would like to eliminate this variable from the
experiment. As we are trying to measure the attenuation % under standard conditions, it is requested that
you mash at 65degC. Ideally you will also do a batch sparge as outlined in the recipe, so the malt profile in
the original wort is similar.
We have chosen a simple grain bill, that will produce an English Bitter flavour. The ABV% has been kept low
so that alcohol does not affect the aroma and oxygen requirement will be achievable by simply shaking the
fermenter for 5 minutes.
We have chosen a single neutral bittering hop addition, so hop flavours and aromas will not be present,
allowing the yeast flavours and aromas to shine through.
The recipe has been based on 70% mash efficiency which most brewers should be able to achieve. Some
brewers will achieve a higher efficiency. If you do this, please add water to the boil to achieve the target OG.
You will then have a bonus few bottles to keep for yourself.
Once the fermentation is finished, you are to bottle the experiment beer into 30*750ml bottles. You will
bring these to a swap night, where you will swap 25 of them with the other 25 brewers (and keep one of
your own to make up a set of 26). The other 4*750ml bottles will be kept (by me) and used for future club
meetings, where we will make the samples available to all members (including those that did not brew in the
experiment) and discuss the characteristics of the various yeasts.
All bottles will need to be labelled with the brewer number (and optionally the yeast used) so other brewers
can easily identify the yeast from the brewer list.
You will get to keep beer made with 26 different yeasts, and you will be able to record your thoughts (on
the aroma and flavours) on a shared spreadsheet as you drink them. We will compile the feedback from
the tasting and publish this on our web site. This will be able to be used as a resource by members on an
ongoing basis.

Style: English Best Bitter
TYPE: All Grain
Recipe Specifications
Boil Size: 32.13 l
Post Boil Volume: 29.12 l
Batch Size (fermenter): 23.00 l
Bottling Volume: 23.00 l
Estimated OG: 1.046 SG
Estimated Color: 13.3 EBC
Estimated IBU: 34.7 IBUs
Brewhouse Efficiency: 70.00 %
Est Mash Efficiency: 85.2 %
Boil Time: 60 Minutes
Amt Name Type IBU
2.00 g Gypsum (Calcium Sulfate) (Mash 60.0 mins Water Agent
4.50 kg Pale Malt, Maris Otter (Simpsons) (4.4 EBC) Grain
0.25 kg Crystal, Medium (Simpsons) (160.0 EBC) Grain
25.00 g Magnum [14.00 %] - Boil 60.0 min Hop 34.7 IBUs
0.50 Items Whirlfloc Tablet (Boil 15.0 mins) Fining
1.00 tsp Yeast Nutrient (Boil 5.0 mins) Other
1.0 pkg Your yeast Yeast
Mash Schedule: Single Infusion, Medium Body, Batch Sparge
Total Grain Weight: 4.75 kg
Name Description Step Temp Step Time
Mash In Add 12.35 l of water at 73.0 C 65.0 C 60 min
Sparge: Batch sparge with 1 steps (25.0 litres) of 76.0 C water
Gypsum added to accentuate the bitterness and provide Calcium as a yeast nutrient.
Magnum hops are being used for bittering only. We do not want any hop flavour or aroma in this beer, as we
are trying to isolate the yeast character.
Created with BeerSmith 2 -

To ferment 23 litres of this beer, you will need 200 billion live active yeast cells. A good way to measure this
is that it is 50ml of clean very thick slurry that you produce from a starter. The live yeast part of the yeast
slurry is the pink layer. You should exclude any dark yeast layers from your calculations, as these are most
likely dead yeast or trub (yes even DME creates some trub if you boil it). So, IMPORTANTLY you need 50ml of the thick pink stuff.
If you slightly underpitch, you will force more esters to be produced, BUT if you pitch too few yeasts (approx < 160 billion cells) you run the risk of generating off flavours during the fermentation, which we do NOT want.
Pitching 200 billion active yeast cells is particularly important for this experiment, as we want you to pitch at
17degC and allow the wort to increase to 20degC (for most yeasts, but some yeasts will require a different
temperature regime)..
Pitch yeast at 17degC and then raise to 20degC. If you increase the set point of your temperature controller
to 20degC and you have a low wattage (20-40W) heating pad or belt in the fermenting fridge, it should take 8 hours for the temperature to steady out at 20degC. This is ideal.
Hold at 20degC for 5-6 days until fermentation slows and then rise to 22degC for diacetyl rest for 2 days.
Then slowly decrease the temperature to 5degC (over 2-3 days) which will force most of the yeast to
flocculate out and settle on the bottom of the fermenter. Bottle once the beer is fairly clear.
Saison yeasts
The objective of the Saison Ale experiment is to determine which of these yeasts produces an ester profile
that you prefer and to give feedback on how well these yeasts ferment out. Some Saison yeasts are
infamous for stalling during fermentation, only to start up again after a few days (or weeks) of slumber.
Increasing the temperature during fermentation should alleviate this problem, but if the yeast stalls, you can
add 100g of dextrose in 100ml of boiling water. I have done this before and after the yeast stalling at 1.020, it took off and fermented down to 1.005 in 2-3 days.
These are special ale yeasts that need a higher ferment temperature to push the Belgian Saison ester profile
which is supposed to be prominent according to the BJCP style giudelines. Pitch at 17degC and raise to
20degC and hold for 1 day. Then raise 1degC per day to 24degC over 4 days and hold. Once fermentation is finished, chill and bottle as per standard ale yeast option.
German Ale yeasts
The objective of the German Ale experiment is to determine which of these yeasts produces an ester profile
that you prefer.
For German ale yeasts (Kolsch, Altbier etc) we are looking for a subtle yeast profile and a lager like finish.
So, pitch at 17degC and hold it there until fermentation is nearly finished, then raise to 22degC for diacetyl
rest. If you push the fermentation temperature to high, you will increase the ester profile, which would make
an Altbier or Kolsch out of style.
Liquid yeasts
These contain 100 billion live cells WHEN they were packaged. This is well short of the 200 billion cells you
need, so you are going to need to make a starter.
You also need to take into account that the yeast will die in the package, even if it is kept in a fridge.
For example, 77%, 55% and 35% remain alive after 1, 2 and 3 months respectively. You can use to work out the required starter regime.
Ideally you will make a 2 step starter, with the final step being in a 2 litre flask (on a stir plate). The following
figures were calculated using
Dry yeasts
Most of the packets say that they have enough yeast to ferment out 25 litres of wort as long as it is <1.050
OG. They also report that the yeast has a density of > 5 billion yeast cells per gram. Again this was the cell
count at packaging, and this can decrease substantially if it was incorrectly treated on its journey to you.
[Note: Beersmith report that dry yeast has a density of 18 billion cells per gram. This would mean a 10g
packet would have 180 billion cells (when packed), close to the 200 billion cells required for this beer. I have read a lot of reports on AHB (and Phil Britain confirmed this at the last meeting) that Mangrove Jack dry yeasts had a long lag time (Phil reported up to 4 days for one of the yeasts) which points to a much lower density than 18 billion cells per gram. I strongly recommend a starter for the dry yeast, to ensure that you have enough active yeast to get an excellent fermentation.
Some of the dry yeast are 10g and others are 11g. Based on the stated density, there WAS a minimum of
50-55 billion cells in each packet. This is WELL SHORT of the 200 billion cells you need for a clean ferment. In fact the yeast count is likely to be similar to a 2-3 month old liquid yeast and so IT WILL NEED a similar starter.
To create a starter for the dry yeasts, first rehydrate the yeast in 100ml of warm water (boil it first and cool it) and then pitch it into a 1 litre starter. Once this is fermented out, chill the starter to drop out the yeast. Then step it up to a 2 litre starter. Ultimately you are trying to grow enough yeast to pitch 50ml of the very thick pink yeast slurry (see above).

Wort Aeration
To reduce the potential variable of initial oxygen level on the beer flavour, aroma and attenuation rate, it
is important that all brewers shake their fermenter for 5 minutes to ensure that the wort is saturated with
oxygen. This will give the initial wort an oxygen level of 8ppm, which is the saturation point of oxygen from air in wort. This oxygen level is more than adequate for this beer with its low OG.
It is important that brewers do NOT use bottled oxygen for wort aeration for this beer. If the 8ppm oxygen
level turns out to be inadequate for the yeast, then this will be a valuable result for the experiment. This will
flag to all brewers that this yeast should only be used IF the brewer can use bottled oxygen, which is not
possible by most brewers.

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