Beer School – Serving Temperature

Try to match these slogans with the beer brand they have been used for: “Cold as the Rockies”, “Cold. Wet. Delicious”, or how about “A hard earned thirst needs a big cold beer and the best cold beer is Victoria Bitter”. Okay, so that last one wasn’t all that challenging, but it illustrates the point that for many people (and advertisers), beer is meant to be drunk as cold as possible. While there is certainly a place for a cold one on a hot day, serving temperature has a profound effect on the perception of aroma, taste and flavour of a wide range of food and drink. This includes our favourite beverage, beer, and in this episode of beer school I’m going to outline some of these effects and give you some guidelines for serving temperature that will enhance your drinking experience.

Temperature and taste

There has been a substantial amount of research on the effect of temperature on taste.  In one set of experiments, scientists at the Monell Taste Center in Philadelphia cooled both the tongue and the test solution and examined the ability of subjects to taste the sweetness of a sucrose solution, the saltiness of a salt solution, the bitterness of caffeine, and the sourness of citric acid.  Interestingly, they noted that the ability to detect both sweetness and bitterness was markedly reduced, while saltiness and sourness were both unaffected.

In a separate study that seems to confirm this qualitative data, another group looked at the effect of temperature on the rate of firing of neurons specific for each type of taste receptor.  Interestingly, they noted that at temperature below 10C, the neurons for sweet perception were virtually non-responsive, showing that the ability to detect sweetness is drastically reduced when the temperature is reduced.  The ability to detect citric acid (sour) however, was also unaffected in this study.  This indicates that although temperature affects our ability to taste, it doesn’t do so equally for all flavours – this means that as temperature drops, the dominant taste in a given beer may change.  More broadly, it provides scientific proof of what we already knew… bringing a cold beer up to room temperature makes it seem substantially sweeter and often less bitter.

In addition to the five senses (umami was recently added to the better-known sweet, salty, bitter and sour) the tongue is also capable of detecting astringency in both beers and wines. Many people describe astringency as bitterness, although there are completely different processes involved in the perception of these compounds.  In beers, astringency comes from components of the barley husk and they can contribute to the body of the brew.  These components are collectively referred to as polyphenols/tannins.  In excess, they are considered a serious brewing fault and this can usually be avoided by sparging at a temperature low enough to prevent tannin extraction.  In some beers, the presence of polyphenols leads to precipitation of other proteins in the beer leading to chill-haze at lower temperature and therefore, they can affect the stability of the finished beer.  If you’ve ever seen an old dusty bottle of pale lager with a thin film at the bottom of the bottle, you’ve seen the effect that time has on phenolic compounds in beer.  It is likely that this time-dependent precipitation of phenolic compounds is a major contributor to the increased smoothness that is observed when some beers are aged.  Polyphenols are fairly interesting chemically and their flavour can be attributed to the same property they have in beer, namely they can bind to and cause proteins to precipitate out of solution – when this happens to salivary proteins on the tongue, it is perceived as a mouth-puckering dryness or astringency.

Temperature and smell

Taste however, is only about 10% of what we call flavour.  The rest comes from aroma components in the glass, and unsurprisingly temperature has a profound effect on our ability to detect smells.  The sense of smell occurs when molecules present in the liquid become vapour and are drawn into specific receptors at the back of our noses.  Since this sense by definition requires compounds to vapourize into the air, increasing the temperature of a given liquid (beer in our case) greatly enhances the ability to perceive different smells.  Different compounds also have different levels of volatility, which will affect how intensely they are perceived.  A fairly simple measure of volatility is the boiling point of the individual compound.  For example, aroma components of hop oils and esters produced by yeast during fermentation tend to have very low boiling points, thereby making it easier for them to leave surface of the beer and enter the air just above it.  Some examples:

yeast-produced esters/phenolics:  ethyl acetate (apple/pear aroma) – 77°C; isobutyl acetate (apple/pear/pineapple aroma) – 115°C; iso-amyl acetate (banana aroma) – 142°C; ethyl caproate (pineapple/banana) – 167°C; 4-vinyl-guaiacol (clove aroma) – 224°C; ethyl phenyl acetate (honey/floral aroma) – 227°C;

hop aroma components:  α-pinene (pine aroma) – 155°C; β-myrcene (pungent herbal aroma) – 165°C; limonene (citrus/grapefruity aroma) – 176°C; linalool (floral/spicy aroma) – 198°C; geraniol (rose/citrus aroma) – 229°C;  geranyl isobutyrate (floral/citrusy aroma) – 240°C; β-carophyllene (woody/spicy aroma) 250°C; β-damascenone (floral aroma) – 274°C;  humulene epoxide (spicy aroma) – 282°C.

Grain-derived aroma components:  maltol (caramel/butterscotch aroma) – 85°C; 2, 5 dimethyl pyrazine (chocolate aroma) – 155°C; furfuryl alcohol (burnt sugar aroma) – 170°C; 5-methyl furfural (caramel/coffee aroma) – 187°C; furaneol (burnt fruit aroma) – 2 acetylthiophene (burnt onion aroma) – 217°C; 2-acetyl-2-thiazoline (toasted popcorn) – 223°C; 2-furoic acid (heavy fruity aroma) – 230°C; ethyl furaneol (caramel/coffee aroma) -248°C; benzopyrene (roast/tarry aroma) – 495°C;

Examples

So, with all of this information in mind, lets imagine a series of hypothetical beers.  The first is a German Hefeweizen.  This style tends to be yeast dominated, with a large amount of ethyl acetate and isoamyl acetate from the yeast fermentation.  Straight out of the refrigerator this pronounced fruitiness will be immediately noticeable.  As the temperature rises, the intensity of these esters will rise and you may start to notice another clove-like aroma.  This comes from a yeast-derived phenolic called 4-vinyl guaiacol that is typically produced by the yeast strains used for hefeweizen fermentation.  It has a higher boiling point than the lighter esters which is why it only becomes apparent as the temperature rises.  As it starts to warm you’ll also start to taste the malt derived sweetness due to the sensitivity of sweet receptors on the tongue to temperatures over 10°C.

The next is a classic… Guinness stout.  It provides a good case in point since it can often be found in bars served at two different temperatures.  The regular tap serves at around 12°C while the Guinness Extra Cold tap serves at a near-freezing 2°C.  As with the hefeweizen, when it’s out of the cold tap, very little in flavour will be notable.  Unlike the hefeweizen though, the yeast used to ferment Guinness doesn’t tend to produce a whole lot of esters.  This means that at cold temperatures, the beer is almost odorless and flavourless (something I know from experience).  Stouts in general tend to be dominated by dark malt components, which as pointed out above have higher boiling points than esters and need to be drunk at a higher temperature in order to be able to smell them.

Finally, we’ll look at a typical American IPA.  These beers also tend to evolve substantially as the temperature increases.  Initially, the hop bitterness will be quite pronounced due to the inability to taste balancing sweetness.  Even cool though, some of the lighter hop aromatics can usually be smelled.  What does change markedly though is that depending on the hop variety used different aromas will be smelled as the temperature changes.  Cool, we tend to smell pine and citrus while woodier/spicier character becomes more pronounced as the temperature comes up.  This is mostly due to the different boiling temperatures of the components that give these smells off.  The lighter malt sweetness will also become apparent once it warms up a bit.  In general, beers like this improve greatly with a little bit of warming.

Serving temperature recommendations

So where does this leave us?  I hope I’ve managed to convince you of the importance of serving temperature on what you actually taste and smell in a pint of beer.  Temperature affects both the ability of aroma compounds to actually leave the beer as well as our ability to smell them once they get to our nose.  The sense of taste is even more profoundly affected by temperature with receptors for sweet sensation being nearly completely inactive below a certain threshold temperature.  Balancing the contribution of each of these can be accomplished by changing the temperature.

Cold temperatures are usually not really good for much of anything.  Below 4°C (40°F) we don’t detect much of anything on the palate and aromatic compounds have a tough time getting out of the beers.  Very light lager styles like helles, heller bock or koelsch (I know it’s not really a lager, but it works) can be appreciated at this temperature since they tend to not have very much in the way of esters, but even these styles can benefit from a little bit of warming in order to appreciate the light malt character and any hops aroma that may have been used.  For macro-style lager, drinking it cold will certainly make the beer seems refreshing, but you won’t taste or smell very much… which might be the point anyway.

Cool temperatures (7-10°C or 42-52°F) are suited for detecting yeast derived aroma of fruit and spice in beers where toasted/roasted malts don’t make much of a contribution.  That makes it work well lighter-style Belgian pale ale, Abbey Tripel, Saison, Witbiers, as well as German Hefeweizen.  Many lager styles also work well at this temperature, particularly hoppy ones like pilsners.

A little warmer is probably where most beers taste the best.  The cool side of the cellar temperature range (9-13°C or 50-58°F) is ideal for a wide variety of styles including (but not limited to) UK-style bitters, mild ales, brown ales and ESB, India pale ale and American pale ale.  Of course, the Brits have known this for years, and most cask ale is served around these temperature which lets you taste them in all of their elegant complexity.  Darker Belgian and German style ales work well at this temperature letting the dark malts and the fruity/spicy esters make their presence known.  A large number of darker lagers are also perfect at this temperature.  With little yeast contribution, the slight warming lets the toasty malt character of viennas, marzen, dunkel and doppelbock really shine through.

For the darkest and most flavourful ales and lagers, these are best enjoyed even warmer (12-16°C or 54-61°F).  Think of your porters, stouts and imperial stouts at this temperature where the heavier dark roasted flavour from the malts and the malt-derived sweetness can be best appreciated.  Although barleywine doesn’t typically have roasted components, they often have contributions of malt, yeast and hops in them and the warmer temperature allows you to appreciate the balance of all of these in the finished product.

The bottom line

Although I’ve offered guidelines here for serving temperature that I consider the best, the best way to figure these things out is to try it yourself.  It is truly amazing how much the aroma and flavour of a beer will change coming from the typical 38-40°F of the refrigerator all the way up to room temperature.  I encourage you try this yourself with a number of styles of beer and see what works for you.  In the end, preferences are personal and you should always see what works best for you… if nothing else you’ll learn exactly what you like and why you like it… and that is kind of the point, isn’t it?

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