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Kölsch: the Science of the Mash, Part 1

Posted by GrizzlyBearLovesKolsch on 12/04/2014 at 09:59:18 PM



Well, it's been a week since my last post and I have been considering very carefully how to proceed on our journey. I originally said I would take the reader through a brew-day, but, after reconsideration, I came to the conclusion that the best line of attack will resemble closely how we all, as home brewers, plan our brew days. After all, planning comes before brewing!

Most brewers will, firstly, determine the style of beer that they wish to brew. I think it is pretty clear from my last post that I've chosen a Kölsch. Second, and this is where brewers may take a differing approach; the brewer will consider the appropriate grain bill. A Kölsch's grain bill primarily consists of Pilsner malt, and perhaps one (possibly two) other addition(s). Because I want to start right from the basics and work upward, I will be sticking to a 100% Pilsner grain bill to start off. This will give me a good benchmark to work from. I can then substitute in some wheat malt or Munich malt at a later date. The differences can then easily be compared.

In this post I want to concentrate on a topic closely related to the grain bill: the mash schedule. Many readers may be wondering how Kölsch beers differentiate themselves. Indeed, the grain bills are pretty similar. We will also find in posts to come that the hop additions and the yeasts used are fairly common amongst brewers of Kölsch. Nevertheless, there are differences between every Kölsch, and these differences are affected by a number of factors, one of these being the mash schedule.

It is now a good time to introduce the reader to a few books that will be considered along this journey, and, hopefully, will help us towards brewing a fantastic Kölsch. The first book is called, A Text-Book of the Science of Brewing by Edward Ralph Moritz and George Harris Morris. This book is not for the faint-hearted. It covers all aspects of brewing from a scientific standpoint (surprise!). Unless you are a biochemist much of this book can be easily overlooked; take it from me: I'm no chemist! However, it is an incredibly intriguing read, and I will be using anything that I can flesh out from its pages to help me along my way. The second book that I will be considering is, Designing Great Beers by Ray Daniels. This book is much more accessible, but in no way lacks detail. Given that A Text-Book of the Science of Brewing was first published in 1891, this book, being published in 1996, is much more modern. An excellent aspect of this book is its practical approach. When I first started brewing, I relied entirely on brewing software for understanding, well, basically everything! The best thing I learnt from this book was how to manually adjust the brewing parameters (such as grains and hops) to achieve different outcomes (such as different gravities and IBU levels). If you're like me, and you rely on brewing software for everything, I recommend this book to you. The understanding that it imparts will take your brewing to a whole different level - and, make you a more creative brewer. Lastly, I will be considering, Kölsh: History, Brewing Techniques, Recipes by Eric Warner. Obviously, this book is concerned solely with Kölsch, and discusses, well, its history, brewing techniques and various recipes. The importance of this book, however, cannot be underestimated. It bridges the gap between the science of brewing and the practical aspects of brewing, and will enable me to apply what I have learned from the first two books when brewing my own Kölsch.

The Science

As mentioned above, I am no scientist. In fact, I am a Canadian living in the UK that loves home brewing, has an affinity for Kölsch, and calls himself a Grizzly Bear. Even though I'm not a scientist, it did not take much effort to come to a firm grasp of the basics behind turning water and barley into sweet wort. In essence, the mashing process is the process by which you convert the starches contained in barley into fermentable sugars. To mash, the brewer adds various grains to a vessel full of hot water. This is called "mashing in". The grains are stirred gently to ensure full contact between the water and the grain, and to avoid any "dough balls" from forming. This is left to rest or steep (much like a tea bag in water), until conversion is complete. At this stage, you have what is called "wort," which will then be boiled, chilled, pitched with yeast, and then allowed to ferment. Whilst the overall process is fairly simple, there are many variables that come to play on the quality and characteristics of the wort. Indeed, the characteristics of the wort will weigh heavily on the characteristics the beer that you will end up brewing.

The most important part of the mashing process is the temperature at which you let the grain steep. This is because the enzymes that convert the starch into sugar are most active in certain temperature ranges. Moreover, there are two important enzymes that work on the starches, and, surprise, they are most active at different temperatures. The two enzymes that we will consider are Beta-amylase and Alpha-amylase. Beta Amylase is most active at a mash temperature between 130 and 150 F (54-66 C), and Alpha Amylase is most active at a mash temperature between 150 and 160 F (66-71 C). For the purposes of clarity, it is important to note that Alpha-amylase will be active within the temperature range for Beta-amylase, only to a much lesser extent.

By mashing grains in the range for Beta-amylase, you will achieve a much different wort than if you mash the same grains in the range for Alpha-amylase, and vice versa. A mash in the range required for Beta-amylase will result in a highly fermentable wort, which works well for dry beers. A mash in the range required for Alpha-amylase will result in a less fermentable wort, but will result in a sweeter and more full-bodied beer.

An example may be necessary. Mash some Pilsner malt for 90 minutes at 60 C, boil, chill and pitch with yeast ("Mash 1"). Now, take the exact same amount of pilsner malt and mash for 90 minutes at 68 C, boil, chill and pitch with the exact same yeast ("Mash 2"). When fermentation is complete for both mashes, take a reading of your final gravities. In theory, Mash 1 should have attenuated further than Mash 2. This is because Mash 1, which utilized a mash temperature aimed at Beta-amylase, contains more fermentable sugars than Mash 2, which utilized a mash temperature aimed at Alpha-amylase enzyme activity.

The fermentable sugar referred to above is Maltose. Mash 1 produced more Maltose, and less Dextrin. Dextrin is, strictly speaking, unfermentable. Moritz and Morris suggest that an abundance of Dextrins leads to four characteristics of the beer: Condition (or after fermentation), body or fullness, soundness or stability and viscosity or head.

Now, as mentioned, Dextrin remains unfermented and adds specific characteristics to the beer. The interesting thing is, however, that it remains in the wort alongside some unfermented maltose. Yes, I said unfermented Maltose. But wait, Griz, I thought you said that Maltose was fermentable?! Yes, I did say that; however, some of the maltose remains in the beer after fermentation because it is locked up beside the Dextrins, in the form of Maltodextrin (which, as the name suggests, is part Maltose and part Dextrin). As the mash temperature rises, more Maltose will become locked up with the Dextrin.

Another example may be necessary to illustrate this in practice. Mash A (which was mashed in the Beta-amylase territory) will give you more "pure" Maltose (maltose completely separate to the Maltodextrin, highly fermentable) and a higher proportion of Maltose in the Maltodextrin (which unfortunately, because it is locked up with the Dextrin, remains unfermentable). Conversely, with Mash B, you will have less "pure" Maltose (Maltose completely separate to the Maltodextrin, highly fermentable) and a lower proportion of Maltose in the Maltodextrin. The fact that there is less pure Maltose in Mash B and more Dextrin in the Maltodextrin results in a lower attenuating, sweeter beer.

This last fact piqued my interest. It appears that Kölsch would be better suited to Mash A, because we want a relatively dry and highly attenuated beer. This is achieved by the high levels of pure Maltose which is produced during the mash. But of course, I do want good mouthfeel, head retention and some sweetness to round off the beer. Can I not have both?! Can I not have my Kölsch and drink it too?! You may think the answer is obvious, but I can almost assure you that we are not thinking the same solution to the problem. More on this in the next post!

Post Script

I have said this before, but it necessitates a second mention. I am not a scientist, and I am absolutely certain that some of my comments above on Alpha and Beta-amylase and its impact on fermentation and the final beer are not without some errors. This post is intended to document a learning experience, hopefully for you and I. So, as always, comments are open and I would love to hear your take.

Last but not least, please head over to and sign up for the mailing list. Part 2 of this post will mark the first entry on my own website, so please come and support!

Tags for this post: Kölsch, Grizzly Bear, mash, science, books, amylase, alpha, beta, maltose, dextrin

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Two isolated mash runs integrated at chilling? The suspense is killing me!

posted by Dustin on 12/05/2014 at 04:06:14 PM