Part two in our series lifting the lid on familiar and not so well known beer and brewing terminology.

Esters

More and more breweries are experimenting with fruit flavouring that’s why we are seeing a large range of fruity beers coming onto the market. Fruity flavours are produced by esters. It may be easy to identify many of these on tasting– iso amyl acetate, for example, produces a banana flavour and ethyl hexonate red apples. But brewers who’ve tried to produce fruit beers will know how hard it can be to control flavour levels.

This could be because of differing ester synthesis conditions during the brewing process, the dispensing system used or, believe it or not, fruit flavours can even be influenced by different shaped glasses!

Like in all brewing it’s important to establish general controls during production but even a small change in ingredients or processing can alter a beer’s fruitiness considerably. Making it one of the hardest factors to control.

So what are esters and how can we learn to better control them?

Basically, esters are produced by yeast metabolism, specifically by a reaction between alcohol (plenty of this in a beer) and an acid (also present at lower levels). In very high concentration esters can create a solvent-like flavour. so the key is to get the concentration just right.

The type of yeast used is a major factor in ester levels with some yeasts giving very neutral ester profiles and others a strongly identified fruit flavours. Wheat beer yeasts in particular release high ester levels. Fermentation temperature also has a strong effect with more esters produced in warm fermentations and resulting in more esters in ales than in lagers. Stronger beers tend to have higher levels of esters as, interestingly, do beers brewed in shallow fermenters.

Estery beers tend to receive a more positive response from drinkers. So as a rule of thumb if you are looking to brew a beer with a better fruity flavour go for a stronger ale, fermented at a higher temperature by a high ester producing yeast, and use shallow fermenters.

Foam

Foam is an important characteristic of beer. Flat beer is can be undesirable and make for poor presentation – except, perhaps, in certain parts of the UK. Foam provides visual impact. It easily distinguishes beer from other beverages and drinkers will expect a good head on their beer. Think of all those cool beer ads with close-ups of foam running down the side of a cooled, can, bottle or glass. That’s why it’s important for brewers to ensure that their beer retains its foam when poured.

Good beer foam is the result of two things: high-quality ingredients (particularly malt); and processing. Malt provides the proteins required to achieve foam. While wheat increases foam proteins significantly. That’s why most wheat beers have thick foam.

Too much agitation during fermentation or packaging will reduce foam on serving. As will excessive lipids from unusual ingredients such as sorghum or nuts. Make sure your glasses are clean too as dirty glasses where grease and oil residue remains (from lipstick for example) will collapse foam bubbles on contact.

Is foam essential to a beer’s enjoyment? It comes down to personal taste as drinkers in certain parts of the UK prefer a pint with a small head. Excessive foaming by an agitated pour reduces carbonation so there is a marked taste difference between the same beer with and without a head. There is also some anecdotal evidence that foam also changes the aroma of a beer by limiting some flavours but this needs more detailed investigation. Try it for yourself.

Gluten

Is gluten-free the next big thing or a passing fad? It is certainly a high profile concern for many foods, not least beer. However, are we magnifying what is only an issue for a few into a problem for many?

Gluten intolerance is commonly associated with Celiac disease which now has some fairly clear diagnostic symptoms. Less clear is possible associations with other conditions and it is these which are causing increased interest in the gluten in our diet.

Beer is no stranger to gluten. As it is made with barley which contains high levels of the gluten proteins associated with gluten intolerance. These hordein proteins have some similar structures to the gliadin proteins in cheese and bread so if you are sensitive a ploughman’s lunch would be a bad choice.

Gliadin and hordein are not fully digested and remain in the digestive system causing irritation and immunological responses to the intolerant.

It is, of course, possible to brew gluten-free beer is, using non-barley grains such as sorghum, buckwheat or millet. Protein digesting enzymes can also be used to reduce the gluten in the final beer – although this may only produce low gluten beer (below a certain specified level than zero).

There are even gluten-free beers produced by fermenting mixtures of sugar and hop extracts. Naturally, these treatments will change the features of a beer and it requires good control to achieve standard beer flavours.

One major challenge is to determine whether other conditions than Celiac are stimulated by residual gluten proteins. The standard test for gluten only targets one protein sequence out of a possible twenty so more needs to be done to identify these and develop alternative brewing procedures.

Hoppy

Big hoppy flavours can be found in a range of beers, particularly bitters and IPAs. They inevitably arise from the oils in hops and deliver that characteristic beer aroma. Hoppy aroma can contain a multitude of components, some floral, some citrus, some spicy or even woody. But with so many variables how can you achieve a consistent brew?

There is no magic formula however, each hop variety will have a profile of components and with experience, brewers will be able to select and blend their choice to a target hoppiness. Differences will occur with each yearly crop so a good nose to test the character of the raw hops is essential along with an ability to predict how this will develop in the brew.

This is important as when hops are boiled flavours react in different ways according to their boiling point. Some, such as the general hoppy aroma myrcene, boil away quickly as they are very volatile. Others, such as geraniol and linalool, remain until the end of the boil meaning hoppiness remains at higher levels within in finished beer.

Hops also differ according to their preparation and storage. Many UK hops are used as cones which have been dried and compressed for storage. International breweries often use hop pellets which are produced from crushed hop powder. It is argued that hop cones have the freshest aroma which is probably true soon after harvest. As time goes on, however, cones lose some of their aromas and can be less fresh than pellets.

Hop aroma can also alter on oxidation particularly if stored at high temperatures developing the ‘catty aroma’ of valeric acid. Not a desirable flavour in beer!

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