Weizen

Weizen is made from wheat malt, barley malt, hops, water and yeast. The BJCP explicitly calls banana and clove the fermentation profile of the weizen yeast.

The banana comes from esters that the yeast makes, mainly isoamyl acetate. Researchers at KU Leuven call that the compound that gives beer a fruity banana flavour. The clove comes from 4-vinylguaiacol, which yeast with the genes PAD1 and FDC1 makes from ferulic acid in the grain. Many brewing yeasts have lost that ability, and in most styles 4-vinylguaiacol counts as an unwanted off-flavour. Weizen yeasts do make it, and in this style a lot of it is actually desired. A sensory study from Freising found about thirteen times more 4-vinylguaiacol in a typical Bavarian wheat beer than in a wheat beer in which that typical weizen aroma was somewhat lacking.

A small nuance: part of that compound already forms when the wort is boiled, but most of it comes from the yeast during fermentation. Witbier is the counter-example: there, citrus and spiciness do come mainly from added coriander and orange peel.

What the 1516 text really said: the Bavarian ordinance names as raw materials only 'Gersten, Hopfen und Wasser'. It says barley, not expressly malt. Wheat is not in it, and yeast is not either. Wheat beer was forbidden in old Bavaria, apart from a few privileges.

What applies in Germany now is different. The current Bierverordnung refers to § 9 of the Vorläufiges Biergesetz of 1993. For bottom-fermented beer, only 'Gerstenmalz, Hopfen, Hefe und Wasser' may be used there. For top-fermented beer, 'die Verwendung von anderem Malz' is additionally permitted. The implementing regulation to the Vorläufiges Biergesetz says it even more clearly: for top-fermented beer, malt of grain other than barley may be used.

Weizen is top-fermented; the Bavarian food agency LGL also counts Weizen, Hefeweizen, Kristallweizen and Weizenbock among the top-fermented beers. A weizen made from wheat malt, barley malt, hops, yeast and water therefore complies with the current German rules, but not with the literal text of 1516.

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.

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.