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Brewing a Wheat Beer with Intensive Banana Aroma
Michael Eder
A European Perspective
Producing a German-style wheat beer may not be as difficult as brewers might think. The most important factors are ingredients and technical knowledge. A little bit of historical background might help, too.
Around 400 years ago during the regency of Lord Maximilian I in Bavaria, wheat beer or weissbier was only allowed to be brewed by aristocrats. This type of beer was therefore very desirable for common people. Until then, production and commerce of wheat beer was only done by the aristocratic family Degenberger, who originated from a small town called Bogen in lower Bavaria.
By heritage, the right to produce wheat beer, the so-called weissbierregal, was passed on to Maximilian I. He foresaw great financial success in producing wheat beer and founded ducal wheat beer brewhouses across the country. The first one was built in 1607 in Kehlheim, a small town on the Danube River. From that time on until the 18th century, wheat beer dominated the Bavarian beer market.
At the turn of the 18th century, tastes began to change and consumers gravitated toward dark or amber beers. Though production declined, the monopoly was still in effect: common people were still not allowed to brew wheat beers.
During the same time period, Georg Schneider, an ordinary citizen of Munich, was the leaseholder of the royal wheat beer brew house (1855-1873) in Munich. As bottom fermenting beers became more and more popular, the royal office wanted Schneider to stop the production of wheat beers in the Weisses Brauhaus in Munich and produce bottom fermenting beers instead. However, Schneider still believed in the potential of wheat beer production and negotiated successfully with the royal office (Regency of King Ludwig II) to be allowed to brew wheat beer. Simultaneously, he seized the opportunity to purchase the Maderbrau brewery in Munich. He then went on to found, together with his son Georg II, the famous brewery G. Schneider & Sohn in 1872. After the Munich brewery was destroyed by allied bombing in 1944, production moved to Kehlheim, where it is still located (Georg VI has been working in the brewery since 1982).
Since the sale of the Weissbierregal to Schneider, the consumption of wheat beer became popular again and still represents a stable market share today.
The wheat beers brewed in medieval time were different than those brewed today. The main reason was the low carbonation due to the lack of pressure-resistant vessels; additionally the raw materials were very different. However, the general character would have been similar to the wheat beers we drink todaya fruity beer, refreshing, easy to drink, and very tasty!
Crafting a Wheat Beer
The choice of raw materials is essential to a good wheat beer. A mix of barley malt, wheat malt (German brewers are forced by law to use at least 50 percent wheat malt for the beer to be labeled wheat beer and also achieve at least 11 percent original gravity) and caramel malt deliver the great malty body typical of this style. The hops should be carefully selected to avoid the presence of too much aroma or bitterness to the beer. Finally the yeast strain used must produce typical wheat beer flavors like clove (4-vinyl guaiacol) and banana (isoamyl acetate). In order to produce sufficient amount of isoamyl acetate ester and therefore increase the banana aroma in the beer, the following recipe is suggested.
The ideal malt ratio for a typical German/ Bavarian wheat beer would be 70 percent wheat malt, 27 percent Pilsner malt and 3 percent dark caramel malt to obtain the typical amber color. Any hops can be used as long as they are dosed carefully to keep the bitterness units below 14; this will allow the estery character of the beer to come through. Finally, an authentic German/Bavarian wheat beer yeast strain, such as Munich yeast available in the U.S. in dry form from Lallemand (this strain was selected at the Doemens Institute in Munich), should be used to maximize flavors. However, this is only realistic if the yeast has access to the right wort composition, which is dependent on the mashing regime.
At the beginning of the mashing process, the temperature should be kept low at 30° C (86° F) to increase the activity of the maltase enzyme in a decoction mash system and increase the glucose concentration (Figure 1). The greater the difference between the glucose and maltose in the wort, the more ethyl- and isoamyl acetate will be produced by the yeast. One part of the mash (25-30 percent) is then separated (thick mash) and heated to a temperature where the ß-amylase is active (62° C or 144° F), whereas the second part (thin mash) remains at 30º C, both for a 30-minute time period. After that time, they should be mixed back together to achieve a wort temperature of 40° C (104° F). This is the most critical step of the mashing process with the maltase being active and producing glucose for the next 30 minutes. Skipping the ß-amylase rest, the wort should be heated directly to a temperature of 72° C (162° F) to activate the a-amylase. After checking for a negative iodine reaction, the mash is reheated to the transfer temperature of 78° C (172° F).
Such a mashing recipe is based on the knowledge of enzymatic activity (Table 1) and yeast metabolism. By using a mash water-to-grist load ratio of 5:1 (by weight), a higher pH in the mash is achieved to optimize working conditions of the maltase. The lower mashing temperature of 40° C (104° F) allows for increased glucose production. Glucose level is around 8 g/l in a standard mash compared to 17 g/l with such a decoction mash system. As a result, yeast will demonstrate a so-called diauxia phenomenon: reduced maltose metabolism, reduced cell growth, and acetyl CoA will be transferred to higher alcohols coming from amino acid metabolism, resulting in an increased ester production compared to a standard fermentation, similar to the process of high gravity brewing.
The pitching rate is 15 million cells per milliliter, with the temperature held between 18-26° C (62-78° F). The higher the temperature, the more esters will be produced.
This specific mashing procedure was designed and developed by Dr. Bertram Sacher of the Doemens Institute to increase ethyl- and isoamyl acetate from 1 mg/l to 3 mg/l and produce wheat beers with intensive banana notes. This method has been successfully tested many times in commercial breweries in Germany.
There is the decoction chart in a previous post and a table on enzyme activity, but it's not important.
