Beer School

The colour of beer comes mainly from the grain. The more caramelised, roasted or darkly kilned malt the brewer uses, the darker the beer. CraftBeer.com of the Brewers Association expressly adds that colour does not equal alcohol content or mouthfeel. A quality guide of the Brewers Association for the trade also writes that colour sometimes suggests strength, but often wrongly.

The style guidelines show it in black and white. An Irish stout is black from dark roasted malt or barley, but according to the BJCP has 3.8–5.0% alcohol. A Belgian tripel is deep yellow to light amber and has 7.5–9.5%. The Brewers Association gives the same picture: a dry Irish stout has 4.1–5.3% at a colour of 80+ EBC (black), a tripel 7.1–10.1% at 8–18 EBC (pale). Such a stout does not have to be heavy either: the BJCP calls it remarkably smooth, with a medium-light to medium-full body.

Of course there are also dark beers that are strong, such as imperial stout (8–12% according to the BJCP). That is due to the amount of sugar that was fermented, not to the colour.

According to the American Homebrewers Association (part of the Brewers Association), the biggest problem with beer that is too cold is that the cold masks many aromas and flavours. Cold slows the release of aroma compounds, so they stay in the beer. The quality guide of the Brewers Association also names serving temperature as a factor in how much aroma is released.

The advice differs per style. The AHA gives a table based on Randy Mosher (Tasting Beer). A few examples, converted to degrees Celsius: light American mass-market lagers approx. 1–4 °C, pilsner and other pale lagers approx. 3–7 °C, pale ale and IPA approx. 7–10 °C, and strong lagers approx. 10–13 °C.

The rules of thumb from the same source: lagers colder than ales, strong beer warmer than light beer, dark beer warmer than blond. And pour a few degrees colder than the target, because beer warms up in the glass.

These are recommendations, not laws: the AHA itself calls them general suggestions, from which some styles deviate. If the brewer gives its own serving advice, go by that. If you drink an ordinary pilsner ice cold, you are doing nothing wrong. The myth is that all beer must be that cold.

The 'skunky' or 'lightstruck' smell is a well-known beer defect with a chemical cause. According to research by, among others, Ghent University (Huvaere et al., 2006), it comes mainly from the compound 3-methylbut-2-ene-1-thiol (MBT), which stinks at just a few nanograms per litre. MBT forms because light breaks down the bitter compounds from hops (iso-alpha acids). Riboflavin (vitamin B2) in the beer absorbs the light and starts the reaction; a sulphur fragment, from amino acids among other things, completes the compound. Blue light (350–500 nm) proved the most effective.

That is why the packaging matters. According to the Brewers Association (BA), brown glass protects somewhat, green glass less and clear glass hardly at all. A Molson patent from 1981 confirms with measurements that clear glass lets through the most harmful light and brown glass the least. But even brown bottles do not belong in bright light according to the BA, and according to a guide from CraftBeer.com (also from the Brewers Association) the skunk smell can then form within a few seconds. The BA calls cans 'mini kegs' that protect beer from light.

Heat is bad for beer, but it causes other defects. According to the Brewers Association, lagers stored at 25 °C tended towards caramel-like notes, and at 30–37 °C towards a cardboard taste (ageing through oxidation). A skunk smell is not part of that.

The Voedingscentrum (Netherlands Nutrition Centre) explains that THT ('ten minste houdbaar tot', best before) indicates until when a product is guaranteed to keep its proper quality. The advice: also use your senses after that date to judge whether something is still good. That is different from TGT ('te gebruiken tot', use by), which is about safety. The European labelling rules (Regulation 1169/2011) prescribe the wording 'best before …' (in Dutch 'Ten minste houdbaar tot …'), and drinks with 10 percent by volume of alcohol or more, according to those same rules, need not carry a durability date at all.

That the date is not a spoilage limit does not mean that beer does not change. According to the Brewers Association, beer begins to age after packaging: the bitterness declines, fruity and floral aromas can disappear and notes of cardboard, honey or sherry come in. The vast majority of beer is meant to be drunk as fresh as possible. Of weizen, for example, the BJCP writes that you drink it best young and fresh.

At the same time, a guide from CraftBeer.com (Brewers Association) names three groups that lend themselves to being laid down, a classification by Patrick Dawson, author of the book Vintage Beer: strong (in general from 8% alcohol), sour and smoked. Of Flanders oud bruin, a tart brown beer (not to be confused with the sweet Dutch oud bruin), the BJCP writes that the style is traditionally meant to be kept, and that examples with some age are considered better.

In short: after the THT, beer is usually not spoiled, but it is different. With hoppy beers often less fresh, with some strong or sour beers sometimes actually better.

With bottle refermentation, some sugar or wort is added to the beer at bottling. The yeast then makes the carbon dioxide in the bottle. The BJCP calls bottle refermentation a common characteristic of the Belgian monastic beer styles, and under the HORAL rules Oude Geuze and Oude Kriek must referment in the bottle. That yeast then sinks to the bottom is normal. A guide from CraftBeer.com (Brewers Association) even recommends storing speciality beer upright, so that the yeast sinks to the bottom.

Whether you pour the layer along differs per style. With weizen the brewer may, according to the BJCP, indicate whether the yeast should be swirled up. Australian Sparkling Ale is, according to the BJCP, usually poured with the yeast. Witbier is, according to the Brewers Association, traditionally poured cloudy. With tripel the BA, on the contrary, writes that you are not supposed to swirl up the yeast on purpose.

One caveat. Contamination with wild yeasts or bacteria can, according to the Brewers Association, cause cloudiness and flakes, and in addition off-aromas and off-flavours, sourness or a bottle that foams over when opened ('gushing'). But in a beer that has been refermented in the bottle, a layer of yeast at the bottom is not in itself a sign of spoilage.

The American institute NIDCD (part of the National Institutes of Health) explains that smells reach your sense of smell in two ways: through your nostrils, and through a connection between your throat and your nose. When you chew, smells are released along that second route. Without a sense of smell, food tastes bland or of almost nothing, according to the NIDCD; smell and taste work closely together.

The quality guide of the Brewers Association says that the right glass, the serving temperature and the amount of carbonation all determine how much aroma is released and how you perceive the beer. The head also holds on to aroma compounds and thus enhances the flavour experience. From a glass those aromas are released at your nose, and you immediately see colour, clarity and head.

Drinking from the bottle is not forbidden by that. It only means that with aromatic beers you miss part of the experience. The often-cited figure '80% of taste is smell' we deliberately do not adopt: we found no hard measurement for it.

IBU (International Bitterness Units) is, according to CraftBeer.com, a measure of the bitter compounds in beer, determined in the lab as milligrams of iso-alpha acids (converted bitter compounds from hops) per litre. The Brewers Association writes in its style guidelines that this figure measures one specific hop compound and does not consistently match how bitter someone perceives the beer. It gives three reasons for that: sensitivity to bitterness differs per person (partly through genetic make-up), other ingredients also contribute to bitterness, and hop aroma and flavour can strongly change the perceived bitterness.

The guidelines themselves give examples. For Export-Style Stout the BA writes that the bitterness can turn out high in the lab, but that the sweetness of the malt dampens the perception. Conversely the BJCP says of kölsch that drier versions can seem hoppier or more bitter than the IBU suggests. And in hazy IPA the bitterness is, according to the BJCP, often masked by the fuller body and the soft finish.

For orientation: CraftBeer.com gives 5–10 IBU for light lagers and 50–70 for robust, bitter IPAs. So use IBU as a rough indication, not as a flavour promise.

The rule was in the Bavarian Landesordnung (a general state ordinance) of the dukes Wilhelm IV and Ludwig X, dated April 1516. The Historisches Lexikon Bayerns gives 24 April; the beer writer Jeff Alworth gives 23 April. Only barley, hops and water were allowed in beer, but the same provision began with maximum prices for beer. Yeast is not mentioned.

As motives for such purity rules, the Lexikon names quality control and consumer protection, but also food supply, price control and tax revenue. Alworth stresses that the decree was much more about money than about health, and that prescribing barley left the wheat free for the bakers. Wheat beer was therefore in principle forbidden; according to the Lexikon it could only be brewed all the same with a ducal privilege.

The name is also younger than the rule. 'Reinheitsgebot' is a 20th-century invention: the Lexikon gives 1909, an article of Ohio State University 1918 and Alworth 1919. Before that people spoke of a 'Surrogatverbot', a ban on substitute raw materials. For the whole German Empire the rule was, according to the Lexikon, only laid down in 1906, in the beer tax law and only for bottom-fermented beer; Alworth also gives 1906. In 1987 the Court of Justice of the European Communities ruled that Germany could not keep out beer that had been lawfully made and sold in another member state because it did not comply with these rules.

Conclusion: it is a rule about permitted raw materials, and originally also about prices. Not a quality mark that says something about flavour or craftsmanship.

The American Brewers Association (BA) calls a 'craft brewer' small and independent. Small means: at most 6 million barrels per year. An American barrel is 31 gallons, so converted that is just over 7 million hectolitres. Independent means: less than 25% owned by a beverage company that is not itself a craft brewer. In addition it must have an American brewing licence, or, as the owner of a beer brand, have that brand brewed in the United States.

Note: the BA thereby defines the brewer, not 'craft beer' as a product. And it is the definition of a trade association for the American market, not a law.

A scientific review article (Morgan, Lane & Styles, Food Reviews International, 2022) establishes that there is a demand for clarification of what craft beer is, and compares the definitions of various national trade associations. It also points out that many small, independent breweries have been taken over by large brewers.

Small scale and independence are thus often part of a definition. But the word 'craft' on a label guarantees nothing in itself about the size or the owner of the brewer.

According to the quality guide of the Brewers Association, most drinkers expect a nice, firm head that lasts a long time and clings to the glass. More important: foam prevents aroma compounds from escaping quickly, and thus enhances the overall flavour experience.

Good pouring and clean, suitable glasses help, according to the same guide, to get the right head. Dirty or poorly rinsed glasses can actually destroy the foam. The BJCP calls the lasting lace pattern that foam leaves on the glass ('Belgian lace') a valued sign of quality in Belgium.

How thick the head should be differs per style and per country. We give no fixed measure for that, because we found no unambiguous source for it.

Researchers at Witten/Herdecke University and the University of Cambridge tested the saying in a randomised crossover study (Köchling et al., American Journal of Clinical Nutrition, 2019). Ninety volunteers aged 19 to 40 first drank pilsner and then white wine, or the other way round. A control group drank only beer or only wine. A week later they swapped.

None of the groups had a significantly different hangover score because of the order. What was related to a worse hangover: vomiting and the feeling of being drunk. The first author summarised it: drinking too much of whichever drink probably leads to a hangover.

A caveat: it is one study, with adults aged 19 to 40, in a study design in which people drank quite heavily.

The International Trappist Association (ITA) writes that the name Trappist is first of all a designation of origin. Three conditions apply for the logo 'Authentic Trappist Product'. The product is made in the immediate surroundings of the abbey. The production takes place under the supervision of the monks or nuns. And the profit is intended for the monastic community itself, for solidarity within the Trappist order, or for development projects and charities.

Every Trappist beer has, according to the ITA, its own recipe and its own yeast. The BJCP also writes of the Belgian monastic beers that many of those names are protected designations, which say something about the origin of the beer and not about a style. Monasteries can brew any style they want.

Words such as dubbel, tripel and quadrupel are style names. 'Trappist' is a label of origin: it tells where and under whose supervision a beer is made, not how it tastes.

The quality guide of the Brewers Association calls cans 'mini kegs' that protect beer from light. And light is precisely the cause of the skunk smell in beer from green and clear bottles (see the myth about 'skunky' beer).

According to beer historian Travis Rupp (University of Colorado Boulder), modern cans have a protective layer on the inside, so that no metallic taste leaches into the beer. They also let in neither sunlight nor oxygen, according to him. With the early steel and aluminium cans that may, according to Rupp, have been different.

Anyone who drinks from the can itself does smell less of the aroma (see the myth about drinking from the bottle). We found no good source on flavour differences in blind tastings, so we say nothing about that.