In the mid 1990s a new beer took the brewing world by storm but in doing so was perceived as the antithesis of good beer by lovers of and campaigners for ‘real’ (ie. cask) ale. The beer that created all this commotion was Caffrey’s Irish Ale brewed by Bass in the United Kingdom. Launched in March 1994 Caffreys rapidly gained market share and spawned a number of imitators and in doing so created a new ale category.

Interestingly, the thing that set it aside from other ales was not the way it was brewed but the way it was served. Nitrokeg beer had arrived.

Kegged beer, where the beer is dispensed with carbon dioxide (CO2) gas, has been with us for a long time. There is a story that during World War II the men of the US Army Air Corps stationed in Britain could not come to terms with the cask beer that was being served in the local pubs.

Traditional cask beer, as you know, is beer that is unpasteurised and still retains yeast which carbonates the beer during secondary fermentation. Once this conditioning is complete the yeast settles out from the beer aided by the use of isinglass finings and it is essential that the beer is handled carefully to avoid disturbing the sediment which would render the beer cloudy.

It has been suggested that the American airmen, returning tired and thirsty from their missions over occupied Europe did not care to wait for their beer to drop clear and bright and when they did drink, if it had not been handled properly, they found it to be flat and cloudy. To further compound the problem a shortage of glass meant that bottled beer was out of the question. This was not good for morale, to have a large number of thirsty airmen clamouring for beer, so a solution needed to be found.

The weighty problem was placed in the hands of Air Force General Curtis LeMay who approached Greens, a local brewer based in Luton, to see if it could help. After spending more than $150,000 the process of putting beer that was carbonated and sediment free into metal barrels was developed. The beer did not have to be left to condition or settle, the barrel could be immediately connected up to the dispense tap and the beer dispensed using CO2 counter pressure. Kegged beer was born.

Although derided by ‘real ale’ fans, for brewers, putting beer into kegs was a fantastic way of improving the quality of the beer that was being served in pubs. Because cask conditioned ale placed a heavy reliance on the skills of the landlord, the brewers lacked control over the final quality of the beer that was served. By removing the yeast in the brewery, carbonating the beer and filling it into barrels that could be immediately used in the pub, brewers felt that the consistency and quality of their beer could be improved.

However, the kegging process pioneered by Greens did not really take off until the 1960s when lager became popular in the UK.

Interestingly at the same time that Greens was experimenting with keg beer Guinness were experimenting with the use of nitrogen (N2) gas in the packaging of its stout. Again it was looking to fill barrels with beer that was free of yeast thus gaining a greater degree of control over quality. But rather than using CO2 as the gas used to dispense beer from the keg Guinness thought that N2 might be a better candidate.

N2 is attractive to the brewer as a dispense gas for a number of reasons. It is not reactive chemically and in brewing terms it is colourless, odourless and tasteless. N2 is relatively insoluble in water, especially when compared with CO2 which is around 100 times more soluble and it is also cheaper than CO2.

But more importantly N2 has a number of interesting effects on beer that the brewers at Guinness saw as being highly attractive to the consumer.

In their trials with nitrogen, the brewers noticed that small amounts of the gas gave the beer a creamier flavour and fuller mouthfeel, and also helped to create a more stable foam that remained until the glass was drained. This had clear benefits for Guinness; a stout, with a full and robust flavour, which some consumers found a little challenging. By creating a more creamy flavour some of the challenging flavour notes were softened, making Guinness more acceptable to a wider audience.

Introduced in 1964, draught Guinness was a huge success and the method by which the beer is dispensed using N2 has been a central feature of the beer ever since.

Bass tapped, if you can pardon the pun, into this idea with its Caffrey’s Irish Ale.

The idea was to open up the ale market to a younger audience by introducing a beer that drank like cask ale i.e with a low carbonation, but it benefited from the quality and consistency associated with keg beer. Furthermore the N2 gas helped to soften the more challenging flavours associated with ales.

So how does N2 gas have this effect on beer? When we drink carbonated drinks the presence of CO2 creates a prickly, tingling feeling on the tongue and for some this can be quite painful and undesirable. The sensations are associated with the trigeminal nerve endings in the tongue and appear to be partially related to the size of bubbles and temperature of the drink, with the sensations being more pronounced at colder temperatures. It is clear that if you reduce the level of CO2 in the beer you will reduce the amount of that gas that comes into contact with the tongue and thereby reduce the prickly sensations.

By using a higher proportion of N2 to CO2 (typically 70 per cent N2 to 30 per cent CO2 but there are other mixtures used) it is possible to get a smoother, creamier mouthfeel with no prickling sensations on the tongue.

Nitrogen is an excellent gas for creating stable, long-lasting foam for a number of reasons. When a nitro-keg beer is dispensed it is passed through a creamer plate. The pressure under which the beer is forced through the creamer plate, created by the dispense gas, rips the N2 gas out of solution creating very small bubbles in the beer. These smaller bubbles are more stable, due to their size, but also because they are filled with N2 gas.

In last issue’s article on beer foam, we explained how disproportionation is an important process responsible for foam collapse. In foam generated with CO2 the gas in the bubble dissolves through the bubble wall from smaller into bigger bubbles creating instability and eventually foam collapse. N2, which is much less soluble in water than CO2, does not dissolve through the bubble walls and therefore remains in the bubble helping to maintain a stable foam. Furthermore as the air we breathe is rich in N2 the gas in the bubbles does not dissolve out and into the surrounding atmosphere, as readily as CO2.

Since their inception, nitro-keg ales have been extremely successful but also courted controversy. Critics say that because of their easy drinking characteristics they were specifically targeted at the younger drinker. Others state that they represent everything that is bad about beer. However, they have, for many consumers, become an accepted beer style. Because of their easy drinking qualities and the sheer theatre that forms the dispense, nitro-keg beers look set to stay.