SciBar at The Vat & Fiddle: David Quain on Beer Quality

Words: Gav Squires
Friday 06 July 2018
reading time: min, words

David Quain from the University of Nottingham joins us at The Vat & Fiddle, Castle Rock's very own brewery tap to tell us all about why few things are better than a pint of draught beer.


Draught beer accounts for 7% of global sales but beer quality can be variable. In the UK it represents 49% of all beer sold but the beer market here is in long term decline. The way that we drink has also changed as cans and bottles have replaced draught beer. We all know that beer quality can vary but how do we measure it?


Most beer comes in 50 litre kegs, which are pressurised and the beer inside is commercially sterile. This is important as it is when micro-organisms begin to grow in the beer that flavour, aroma and clarity become compromised. The problems can begin when the keg is connected to the dispense line. Most pub cellars in this country are around 12oC, which is a throwback to the days of cask beer. So, our beer is being kept in conditions that are too warm and so it has to be cooled. I’m a lot of pubs there is also a large distance between the cellar and the actual bar.


All of which can lead to the growth of Colony Forming Units in the beer. Where good quality beer has 1000 CFU/ml or less, poor quality beer can have over 50,000 CFU/ml. Of course different beers vary in their spoilage and there are different bugs in different pubs. The old way of testing a beer’s microbiology wasn’t particularly great, instead David and his team begin by looking at how cloudy a beer is as this is a good initial indicator of how many CFUs there are. From there, David and his team have been surreptitiously stealing half-pints of beer from local pubs to take back to the lab and test.


It turns out that lager is generally better quality than ale - this is mainly due to throughput as all keg beer should be turned over every 4-5 days. The pipe that takes beer from the cellar to the bar is called the python, each one has a line in the middle filled with cold water and all of the other beers in their own tubes around it. Lagers are nearest to the middle to ensure they are kept cool by the water. These pythons are usually 25-30 metres long but the one at East Midlands airport is 300 metres. The inside of the lines in the python are coated with nylon to try and prevent bio-films from forming. However, this only works if they are regularly cleaned and this should happen weekly. Of course, for a variety of reasons, this doesn’t always happen. Beer nozzles are also not cleaned properly - if you’re in a pub at closing time, you’ll see that they are all taken off the tap and put into a glass of soda water. This does nothing! Soda water doesn’t have any magical anti-microbial properties!


So how do we assure beer quality? The first thing we need to do is sort out the training - people don’t intentionally do bad things. Once you train people how important regular and effective line cleaning is and how important it is to sanitise beer nozzles properly, they’ll do it. It’s important to use the right line cleaners though - good ones work, the cheap & cheerful ones don’t. Throughput is significant - beer needs to be turned over regularly. Also, beer can find its way back into the keg so the keg coupler has to be sprayed with anti-microbial before it’s put on. The other big problem is that while the industry talks about quality, they have no actual definition for what it is.


While all of might be slightly worrying and even off-putting, it’s important to remember that you don’t get pathogens in beer. So, while it might taste bad, it’s not actually dangerous. It’s also a far bigger problem when it comes to soft drinks served on draught. It’s also different for different beers - Cobra, for example, is very robust but Peroni is very vulnerable. Cider, on the other hand, is very acidic and the industry claim that you don’t need to clean the lines but it can be susceptible to yeast growth. David closes with his tips for building a new bar - keep it simple, keep it close, keep it cold and keep it clean.


SciBar returns to The Vat & Fiddle on the 25th of July at 7:30 where John Brookfield will talk on Jumping Genes In The Genome.


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