Yeast is one of the four major ingredients used in brewing along with water, hops and grain. It is technically classed as a fungus and multiplies by the cellular process of mitosis, which is cell splitting where the chromosomes from the original are split to create two new cells. There are several strains of yeast but in brewing the strains convert the sugars from the grains during the mash to alcohol and carbon dioxide.

Yeast is a wonderful microorganism that has many uses, primarily baking and brewing. I wanted to learn more about these little guys and got in touch with Chris Bond the Collection Manager at the National Centre of Yeast Cultures (NCYC) to learn more about them.

Firstly what is the NCYC and what is its role? The NCYC (www.ncyc.co.uk) collects, preserves, characterises, exploits and/or provides the means for others to exploit all kinds of yeast and yeast-like fungi. Their aim is to become the worlds largest, most biodiverse and best characterised yeast collection. The NCYC was originally housed at the Brewing Research Foundation, so a core part of the collection has always been brewing yeast. The oldest brewing strain in the collection is a Carlsberg Laboratory Strain (Strain 21) deposited with the NCYC in 1920, but the earliest brewing strain known for full brewing provenance is NCYC88 deposited in 1943. The NCYC work with both industry and academia supplying a wide range of different yeast species all throughout the world. They also carry out quality control, streak plates, DNA sequencing and DNA fingerprinting and strain identification which can be to either identify contaminants or identify the characterisation and description of completely new yeast species.

Brewing yeast primarily comes as two strains Saccharomyces Cervisiae, ale yeast, which ferments at the top of the fermentation vessel at room temperatures and Saccharomyces Pastorianus, lager yeast, which is also known as Saccharomyces Carlsbergensis which ferments at the bottom of the vessel at a lower temperature. Another type of yeast is used in brewing is Brettanomyces aka Brett. Brett is primarily used in old European style beers particularly lambics. According to Chris 'It is slow to work, generally being used as a secondary yeast after Saccharomyces Cervisiae has finished its primary fermentation and typically imparts an earthy, woody and musty character.' Anyone who has had a Brett beer will know what Chris means by this.

On-going research with the IFR biorefinery centre (www.ifrbiorefinercentre.ifr.ac.uk) aims to screen the entire collection for strain with properties which might be exploited in the future. We know that yeast has an impact on the flavour of the beer and the understanding of what flavours the yeast imparts on the beer is the subject of a lot of research from brewers and companies. NCYC have recently published a paper looking at this effect.

Investigating Flavour Characteristics of British Ale Yeasts: techniques, resources and opportunities for innovation. Parker N., James S. A., Dicks J., Bond C., Nueno Palop C., White C., Roberts I. N. (2014) Yeast 32 281-287.

This paper was a collaboration with White Labs, USA where five different British Ale yeasts where brewed with all other parameters being kept constant and the yeast being the only difference. The results showed that they observed a significant difference in both the timing and quantity of flavour-related chemicals produced. At present there is no strain improvement programme taking place that is looking into the production of new strains to improve certain brewing characteristics. However, they would be willing to discuss the possibility of starting up such a programme. They are though looking for better ways to characterise the properties of yeast in the collection so they could be more precisely used by the brewing industry.

So what trends do they observe from the craft beer industry with regards strain requests? ' We definitely see a trend towards strains that either haven't been used for a long time or are from relatively unusual sources. For example, we have had a great deal of interest in a traditional Norwegian Kveik brewing yeast which has recently been deposited into the collection.'

If you want to see a list of the NCYC brewing strains go and have a look here https://catalogue.ncyc.co.uk/strains/brewing and for more information on their services for industry check this link out. www.ncyc.co.uk/services

Image of Saccharomyces Cervisiae 1026 NCYC courtesy of Kathryn Cross (IFR Microscopist) from the National Centre of Yeast Cultures.

If you want to learn more about yeast then why not purchase the yeast book from brewers publications? You can use the link below.

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