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Recreating the perfect British Pint

20 December
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What the “flocculation” are you talking about?

Hopefully the title of this blog post grabbed your “attenuation”.  For those who don’t get the joke, this is a post about yeast.  We provided a 101 background in the “Getting Started Series” post but now its time to dig in a little deeper into this magical little fungus.

Top fermenting yeast in an open fermenter, smells yummy

Top fermenting yeast in an open fermenter, smells yummy

Yeast is truly a magical mould, there were times in our past, before purification systems, when water was unsafe to drink. Ale and wine were seen as staples and a safe form of nutrition (I would argue that with the quality of our food today homebrewed ale remains a safe form of nutrition). Yeast is still considered a powerful nutrient, rich in both B-complex vitamins and an anti-bacterial being the basis of penicillium notatum, the foundation of modern antibiotics. But to beer drinkers around the world yeast is know as the magical fungus responsible for converting sugar into alcohol and putting bubbles in our beer.

God made yeast, as well as dough, and loves fermentation just as dearly as he loves vegetation. – Ralph Waldo Emerson

Types of Yeast

First it is important to differentiate between the two styles of yeast used to brew.  The first is saccharomyces uvarum, often called lager yeast, in which the yeast settles and ferments on the bottom of fermenter.  This type of yeast works at much lower temperatures and ferments more of the sugar leaving a drier, crisper beer.  This yeast is typically used to brew Pilsners and Lagers. It is believed there are very few strains of lager yeast with all lager yeast descending from only 2 primary strains.

The second type of yeast is saccharomyces cerevisiae, often called ale yeast, in which the yeast rises to the surface of the fermenter causing a thick layer of foam called krausen.  This is the type of yeast used to brew all British and most European beers.  There are numerous strains of this type of yeast, each providing very distinctive characteristics you should consider when planning a recipe of which I have highlighted 5 important ones below:

1) Flavour – Ale yeast strains work by synthesizing the sugars and other enzymes derived from the malt. The flavours most commonly associated with ale are esters, resulting in an “ale taste,” as well as more-easily-described flavours such as apple, banana, and pineapple. Combinations of yeast strain, malt, and temperature can be responsible for chemicals causing other flavours, such as a cidery taste or butterscotch.

2) Attenuation – Is a percentage that measures the amount of sugar converted into alcohol during the fermentation process. Lower attenuating yeasts will leave more sugars behind leading to a sweeter taste.  Higher levels lead to a drier taste with alcohol notes.  Most yeast manufactures provide an observed attenuation level for each yeast strain which a brewer can then use when considering the target ABV and taste of a recipe.  I find it helpful to keep your own chart of observed attenuation for the yeast strains you use.  The ranges provided by the suppliers are fairly accurate but will vary depending on your own brewing conditions.  No one wants a yeast to under-perform.

3) Flocculation – Refers to the clumping together of yeast cells once the sugar has been fermented into alcohol.  As the yeast cells clump they begin to fall pulling down other matter suspended in the beer. Larger clumps tend to pull down other particulates suspended in the beer and lead to brighter, clear ales without the need for filtration or additives, know as “high” flocculation. Lower levels or “low” flocculation yeast might need additions such as Isinglass during the secondary fermentation phase to help pull down some of the suspended yeast or proteins left behind.

4) Alcohol Tolerance – Most yeast suppliers supply an ABV tolerance level yeast can reproduce under.  Ales with a high ABV such as Imperial, Barleywine or Old Ales need to be fermented with yeast strains with a high ABV tolerance say 10%. Some varieties of Barleywine that are bottle conditioned will require the use of Champagne yeast to ensure carbonation is successful in the bottle.  Remember to check the tolerance of your chosen yeast is higher than the target ABV.

5) Fermentation Temperature – Refers to the recommended temperature the yeast will perform optimally.  Too warm can lead to off flavours in the ale, too cold and the yeast head on top of the fermenter can fall prematurely and cause a stalled fermentation.

The most important stage for yeast in the brewing process is being pitched into the primary fermenter to begin its work.  Make sure the temperature of the wort is optimal at around 75-80°F, the wort is well aerated to provide the yeast cells the oxygen they need.  Most important make sure the yeast is working.  This can be done by creating a yeast starter.  Bring a pint of water to boil, add some DME, and boil for 15 mins.  Place in a jug, cool, and pitch the yeast. Insert and airlock and watch the yeast go to work.  A healthy yeast will be fully active within 24 hours.

Remember you can replace a yeast but you cannot replace a brew gone bad.  Hope this information helps, I find it most useful when selecting the right yeast to use for a specific recipe. Next up in our deeper dive into ingredients will be the water.

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