Weizen pt 1: The Acid Test

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!

Cheers

LB

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20 thoughts on “Weizen pt 1: The Acid Test

  1. Some of this reads like my final assignment for my HNC, a liberal dose of plagiarism with some of the words changed to make it sound like I’d wrote it 😉 If its all your own work I apologise 😉 Your Second Blog Post, and a massive brainer to boot!

    • Of course it’s not all my own work! I’ll go though it and put the references in if it makes you feel better! however I did study applied industrial science and inorganic/organic chemistry so I can back up the big words with understanding! 😉

      • I’ll just say ‘Oooo, get yooooo’! 🙂
        I’ve always liked science, too much watching early morning Open University on TV as a kid with bearded blokes in beige trousers. (The bearded Blokes were on the telly, not sat watching with me, that would have been weird!)

        If I read carefully i do follow 🙂

      • Sorry, may have gone on the defensive there! Very tired as just finished a night shift!

        I didn’t want the post to sound like it was my primary research, but also didn’t want to litter it with references like a piece of Uni work!

        I like reading journal articles an thought that blogging what I have read may interest others! 🙂 plus I have a beard, no beige trousers though! Do camo shorts count? 🙂

      • Camo shorts are a bit radical, make sure your beard is well stroked to compensate for the lack of Beige!
        I half-thought what I initially commented might be pushing it a bit, so sorry too… my excuse is i suffer from Early-Morning-Stupid-Brain-Syndrome (EMSBS for short!)

  2. Should have also said that the Ferrulic acid rest is also in the working range for the glucanase enzymes, which reduce the sticky glucans making the mash easier to lauter, and also to provide that wonderful thick long lasting head which is so essential for weizens.

  3. I think my IQ grew by 5pts to 32 by just reading this… See, i completed a sentence 🙂

    Keep it coming!!!

    bite sized knowledge made for idiots like me

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