Archives for September 2013

To brew a classic hefe-weizen, you need the right yeast strain.

This is the fifth part in a series on German wheat beers. The first part was posted September 3rd.

If you were to follow all of the instructions on making a classic German hefe-weizen, but fermented the beer with an English ale yeast strain, America ale yeast strain or lager strain, you would not yield a beer with the typical wheat beer flavor and aroma. Brewing a hefe-weizen requires a yeast that will produce the spicy, clove-like, phenolic aroma and flavor we all associate with wheat beers.

This flavor comes from 4-vinyl guaiacol (4VG) and other similar phenolic molecules (including 4-vinyl phenol) and these are only produced in detectable quantities by certain yeast strains. These strains contain a variant of a gene (named POF, for phenolic off flavor) that is considered a flaw in most other beer yeast strains.

The POF gene codes for the enzyme ferulic acid decarboxylase. As the name implies, the enzyme catalyses a reaction in which a carboxyl group is removed from ferulic acid, leaving 4-vinyl guaiacol (4VG). So, if you have ferulic acid in your wort, fermenting with a POF+ yeast strain will give you 4VG in your beer. Fermenting with a POF- strain, a strain in which the enzyme is not functional, will yield a “clean” beer, with levels of 4VG below detection (as in most American wheat beers). Lager yeast strains and most “normal” ale strains are POF-, while wheat beer strains are POF+. (Some wine strains are POF+.)

Of course, to brew a hefe-weizen, you don’t need to know the genetics or biochemistry of what is going on— all you need to do is select an appropriate yeast strain. And, this isn’t hard since all the relevant yeast strains have either “hefe-weizen,” “weizen” or “wheat beer” in their names.

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This post is part of a series on German wheat beers.

The clove and banana balance in a hefe-weizen is influenced by the pitching rate and fermentation temperatures.

As I mentioned in the post that began this series, in many ways brewing a German hefe-weizen is similar to brewing any other ale. And conducting the boil is one part of the brewday where this is mostly true.

The Boil

As with the vast majority of beers, you want a vigorous boil to sanitize the wort, coagulate the break material and isomerize the alpha acids from the hops. (There are also a host a minor goals that the boil accomplishes.) There is one minor twist when boiling a hefe-weizen wort.

Two differences between a wheat beer wort and a “regular” ale wort are that a hefeweizen wort contains more protein and fewer tannins. Wheat malt has a higher protein content and the low hopping rate (typically 20 IBUs or less) contributes fewer hop-derived tannins to the wort. Because protein-tannin complexes are part of what you want to precipitate in the boil, you should boil your wort vigorously — at home for at least 90 minutes (and perhaps up to 120 minutes). Commercial brewers, if they employ an external calandria, can cut the time to 70 or 80 minutes. Other than extending the boil longer than some ales, the hefe-weizen boil can be handled as you normally would.

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Wheat can present some problems in the brewhouse, but they are all manageable.

This is the third part in a series on German wheat beers. The first part was posted September 3rd.

German hefe-weizens are made from wheat malt and barley malt. A beer must have at least 50% wheat malt to be called a hefe-weizen and a 70:30 wheat to barley ratio is the classic Munich-style blend. Hefe-weizens are normally 11–13 °Plato (OG 1.044–1.052), with some examples being slightly higher.

Mashing the grains for a German wheat beer differs in two respects from most “normal” ale mashes. First, your wheat malt is large, naked (huskless) and sticky (contains more gluten), compared to barley malts. These differences can cause problems when crushing and when lautering. Secondly, adding a rest — called a ferulic acid rest — to you mash program can influence the yeast-derived character in your beer. (Specifically, the clove aspect of the beer’s aroma will be enhanced.)

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