First, a little bit about wheat beers. Wheat beer (Weizen) is beer brewed with a portion of malted wheat replacing malted barley. Weizen can be split into a couple additional categories, Hefeweizen and Kristallweizen, along with styles like dunkelweizen and weizenbock. Kristallwezien is wheat beer that has been filtered to remove the yeast and any haze from the beer. Hefeweizen ("yeast wheat") is unfiltered Weizen that contains haze from the yeast.
To make matters even more complicated there are multiple forms of Kristallweizen and Hefeweizen. I will be writing today about just Hefeweizen, as it is the focus of this post. Hefeweizen in Germany can be sub-categorized by region, either North, Middle, or South (Bavarian). What sets these areas apart are the aromas of the Hefeweizen. In Northern Germany Hefeweizen most often shows clove like aroma along with nutmeg and other phenolics. In Bavaria banana esters are emphasized along with apple. While in central parts of Germany a Blanche is often seen between the two (clove and banana). While this is not a hard and fast rule it gives a good generalization of Hefeweizen in Germany.
The focus today is to make a Bavarian Hefeweizen (a banana bomb). To do that we need to create as much isoamylacetate (which smells like banana) as we can. There are several things we can manipulate to do this, (1) the yeast and (2) the grain bill.
To create as much isoamylacetate (banana) as possible we want to pick the correct yeast strain. In the example below I will be using a proprietary strain from the Brewing Science Institute. Your best bet to obtain this strain is to culture it from a growler of Prost beer. If you do not have this option available to you I would recommend Wyeast 3068.
Yeast produces isoamylacetate in response to stress. So in order to stress the yeast out you can do several things, under pitch and under aerate. You should pitch only 25 % of the cells you would normally use and only aerate half of what you normally do. These two factors in combination will produce a very banana like beer.
You also want to manipulate the fermentation temperature and ferment the beer at > 68 F.
Some of the precusors for the phenolic compound that smells like clove are created while mashing. In particular a step mash that has a rest at 111 F and 125 F produces ferulic acid which will result in an increase in clove in the finished beer. To prevent this and create more isoamlyacetate a single step mash to create a highly fermentable wort is suggested. I have also heard it recommended that 3 % glucose added to the boil will increase the level of isoamylacetate.
Using all of the above knowledge I decided to brew a simple Bavarian Hefeweizen.
I used a very simple grain bill with 50% malted wheat and 50% malted barley. I added a single hop addition for about 12 IBUs.
50% Malted Wheat
50% Malted Barley
Single step mash at 148 F
60 minute addition of Hallertau for 12 IBUs
Propriertaty yeast strain at <8 million cells/mL
Fermented 70 F
Apperance: The beer is straw yellow with an intense and sticky head. A little cloudy from the yeast but not too much.
Aroma: The beer is a banana bomb, I also detect a little bubblegum and some wheat aromas.
Taste: Wheat beer! Very simple, a little bit on the sweet side but very very drinkable.
Overall: This was a great success. I was able to produce loads of isoamylacetate and create an incredible refreshing wheat beer.