Wheat beers are one of my favourite types of beer! In particular Bavarian Hefeweizen! I don’t think there is a better beer for lazy, summer days in the garden, beer garden, well anywhere actually!
There was a thread recently on JBK regarding wheat beers that divided opinion! A little bit like marmite, some people love them, others can’t stand them! I fall very much in the former!
One of the main reasons I love a good hefe is because they are so much more than the sum of their parts, yet it is this simplicity that makes them so good!
In my eyes a great hefe doesn’t need a lot of ingredients! Wheat malt (at least 50% but I tend to go 60-70%), Pilsner malt, and a touch of Munich malt. A darker weizen can be achieved by using a small percentage of one of the de-husked German carafa special malts.
Hops should be a noble variety! I tend towards Tettnanger. I like my hefes to be about 15 IBUs, which is at the top end of the style guidelines!
The two big flavours that come to mind however, when talking about hefeweizens are clove and banana! The compounds responsible for these flavours are phenols and esters!
This blog post is called ‘the acid test’ because I want to talk about ferulic acid! Any homebrewer who has made a German Weissebier will know that a fine balance between the esters and phenols make a great weissen. It can be all too easy to let the banana go wild, especially with yeast such as WLP300. I have struggled in the past to get the phenols to shine through. It was this problem in my brewing, and subsequently finding the answers (for me at least) that lead to this blog post.
Prequel to the sequel
Ferulic acid is the precursor to 4-vinylguaiacol (4VG). In the production of weissbier, the yeast decarboxylates ferulic acid into 4-vinylguaiacol, which is the predominant clove like phenol we all love so much!
Above is a pictorial representation of the decarboxilation process, whereby ferulic acid looses a molecule of CO2, either thermally or enzymatically, and becomes 4-vinylguaiacol. In the case of weissebier fermentation we are talking about enzymatic decarboxylation.
So put simply, we can boost the levels of phenolic flavour in our weissebier by utilising this enzymatic transformation. The choice of appropriate yeast is an important tool in controlling the phenol concentration in the resultant beer, as not all yeast has the ability to decarboxylate phenolic acids. Specific weisse beer yeast such as the commercially available White Labs WLP300 and Wyeast 3068 are what is known as Pof+ yeast (phenolic off-flavour) as they have the POF1 gene which enables the yeast to perform the decarboxylation.
The second way to control phenol production is by controlling precursor release during the mashing phase of wort production. Ferulic acid can be found both free and ester bound in the mash. These ester bonds can be broken by ferulic acid esterase. It has been found that the liberation of ferulic acid in the mash is maximised with a mash pH of 5.8 and a mashing temperature of 43-45oC. It has been observed by Vanbeneden et al (2008) that mashing in at 65oC produced no enzymatically released ferulic acid due to the ferulic acid esterase being denatured. It has also been shown that a 30 minute rest at 43-45oC releases the greatest amount of ferulic acid.
Fermentation temperature has been shown to affect the production of 4VG. 4VG production increases with fermentation temperature and maximises at 20oC
So in summary, there a number of practical measure that can be used by the homebrewer to enhance the phenolic characteristics of a weissebier.
- Appropriate yeast choice (Pof+)
- Ferulic acid rest (43-45oC for 15-30 mins)
- mash pH of 5.8
- Fermentation that reaches 20oC
As this is a multi part blog post part 2 will look at the other side of the weissen coin, esters. The bananary goodness that is the ying to phenolic yang!