Beer Production Pt. 2 - Fermentation

February 15, 2018

Now we come to yeast. A single celled fungal organism called Saccharomyces Cerevisiae.

It reproduces by budding and although requires oxygen in the early stages of growth, settles down to work anaerobically (without oxygen) to use those fermentable sugars to produce alcohol, carbon dioxide and the many flavours compounds that make each beer unique.

 

Consistency is the key at this point, temperature control of the fermentation. Yeast produces heat as it ferments and warmer fermentation temperatures can produce flavours that may not be wanted in all beers. So, a good thermostatic control linked to a chiller is in order here ensuring a consistent fermentation temperature throughout.

 

There are other types of yeast. Saccharomyces Carlsbergensis, which, will come as no surprise is a lager yeast. In wine making there are other species of yeast that are present on the fruit and although will start a fermentation; require other yeasts adding that will tolerate the higher alcohol levels.

Many brewers are now experimenting with different types of yeast to get different flavours. They include mixtures of wild yeasts that may also contain lactic bacteria.

I have enjoyed some of these beers and admire the innovation but will not go down the same route. The reason? Once wild yeasts or bacteria have been used in your brewery they can become endemic and will affect fermentations whether you want them to or not. I know of breweries that have separate equipment for its beers produced with these yeasts so the core range is unaffected. Brewdog are building a completely separate facility for the purpose of sours and lambics at their Aberdeen facility and planned for their new American brewery in Ohio. Our success has been our consistency and we manage that with good yeast husbandry and hygiene. A separate facility is outwith our bank balance so these yeast only get out to play at home in the airing cupboard.

 

Anyhow, whatever yeast is used, it is there to produce alcohol, carbon dioxide and flavour.

The compounds that make up the flavour profile are too numerous to go into detail. Some are from the malt, some are from the hops and some are from the yeast. Predicting what will come out the other end with the raw materials to hand is only something an experienced brewer can do.

 

So, all that’s left to do is to condition the beer, put it into casks and fine it. Not quite as simple as it sounds. We have to make sure that the yeast count is down to the correct level and that the amount of fermentable material is correct so that the barrels don’t get too lively or, at the other extreme, the beer is not flat.

 

Of course some brewers don’t want to clear their beers and argue that to do so will remove flavour. I think this is a cop out and my view on this is well documented. I would agree to some extent flavour may be removed with fining so, adding extra flavours early in the brewing process can get round this.

Not all beer gets processed this way but is increasingly going into keg. Again sometimes filtered bright and sometimes left cloudy but always carbonated. The choice is there for the consumer.

Small pack beer (cans and bottles) is a different matter. The product has to be stabilised and may have to be stable for several months. If yeast isn’t removed then the amount of fermentable material cannot be above a certain level or the consequences could be dire.

 

Traditionally, to produce a bottle conditioned beer, it would be fermented out and the yeast removed. Then, a suitable priming sugar added with flocculent yeast that would settle readily without finings. These days with haze not being considered a problem you can leave your original yeast strain in although if you don’t ferment out you have to be very aware of the limit of your fermentation.

Most of the Hadrian Border beers are meant to be bright and clear. We do sometimes produce hazy products but will always inform the customer first.

 

We hope you enjoy our finished products and welcome any feedback whether positive or not. There is a lot of choice out there which is good for the consumer and only serves to keep us on our toes. As it should be.

 

Andy.

 

 

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