Saturday, January 5, 2013

Mash Temperature Theory

Mash composition vs time in minutes.
Blue - Percentage of starch in the mash by weight
Red - Percentage of unfermentable sugars
Green - Percentage of fermentable sugars

Most likely you've heard about the enzymes in wort before, but I'm going to try to explain from little different perspective that hopefully shed some new light onto the subject for you.  It did for me.
There are two enzymes that primarily work during the saccharification of the wort.  These are Alpha-amylase and Beta-amylase.  The Beta's work slow, produce easily fermentable sugars, and work best at lower temperatures.  The Alphas work faster, produce hard to ferment sugars, and work best at higher temperatures.  You can see from this that selecting a mash temperature and time will change how much work each of these enzymes can preform. 

At low mash temperature, as seen in the 145 degree Fahrenheit chart below, the Alpha enzymes are barely active.  The Beta enzymes, however, are highly active, making up for the difference causing a 145 degree saccarifcation mash rest to produce about as many fermentables as a 150 degree rest.  At higher temperatures the Beta enzymes are not as active, but the Alpha enzymes are very active.  This produces a mash that has 100% conversion, but has less fermentables remaining.


  1. What are the units for the X axis?

    1. The x-axis is time in minutes. Keep in mind that this is just and example derived simply to illustrate the theory. There will be deviation in a real world application.

  2. Looks like 90 minutes is going to be necessary at 145F then for a highly fermentable work. What factors does starch solubility play in this? The startch from barley does not become fully soluable until 150F.

    Your timing on this is excellent (for me). I was just looking for a comparision of time / fermentability today trying to understand the differences in temperature vs fermentability of wort.

    Can this be modeled in a formula? For instance, at a given temp / time combination, what theoretical ratio of UFS:FS will exist?

    1. Yes, generally I have seen that to get an extremely fermentable wort at 145°F you need at least 90 minutes.

      Yes, good point, solubility of starch plays into this as well. Do you have a reference for the 150°F temperature for the solubility of malted barley starches? I haven't seen that before, but it would help to explain the results of low fermentable mashes conducted at temperatures less than 150°F.

      On one hand there are an enormous number of factors that play into starch to sugar conversion beyond temperature and time. There is the grist composition, pH, calcium and other mineral levels, didactic power, and the list goes on. I started trying to look at all this and it made my head spin.

      On the other hand, to some degree, a grist is a grist.

      Something I am considering is profiling starch, short chain and long chain sugars throughout a mash. From that I could derive some practical observations that may be useful.

  3. Steven:

    I routinely do long mashes (2-8 hours) and have also noticed, as you have, that fermentability goes way up. In fact I usually have to add at least 3 degrees to my starting mash temperature in order to denature enough beta amylase so that I get a similar amount of unfermentables compared to a 60m mash.

    If I mash at 153 (starting temp) for 2+ hours I end up with over 90% attenuation with US-05. For medium gravity beers I mash at 156-157 (~85% attenuation) and for malty beers I mash at 158-160 (~80% attenuation).

    Just thought I'd pass this along.

  4. Interesting data. Would you mind sharing the raw data for these plots? how did you calculate these numbers?

  5. Awesome! But I just upgraded to a Braumeister.
    Have you got a link to tables for multistep mashing?

    1. The Braumeister looks like a very nice system. Sorry I don't have any tables for multistep mashing. You might find this post that has more detail about temperature effects useful:

  6. what are the methods, raw data?