A brewing puzzle: solution

Kudos to Clayton, mantis, and MannekinPis, who were on the right track about how to make beer in 17th century Germany.  The trick to exactly hitting arbitrary temperatures without a thermometer lies in the fact that boiling water is always 212 °F.

Ice is not relevant here, though.  For one thing, ice does not have a single fixed temperature, and can be much colder than freezing point.  For another, Hans does not have a freezer, electricity, or any other way to make ice!

A traditional brewing technique is:

  • Take 10 gallons of water from the well. Underground temperatures are extremely steady throughout the year, so this will not vary by more than a degree or two. Hans must learn by trial and error what temperature his particular well happens to produce. Let’s say this is 50 °F.

  • Measure out 6.3 gallons, and bring it to a boil.

  • Mix everything back together. 3.7 gallons at 50 °F plus 6.3 gallons at 212 °F = the desired 152 °F.

There is no need to worry about heat loss once the mash is at the desired temperature. Five or ten gallons of hot liquid has a lot of thermal inertia, and can sit long enough for the enzymes to do their work without cooling too much.

More complex mashes (used to make various kinds of beer) require a series of different temperatures, which can be achieved by repeatedly boiling the appropriate portion of the liquid and then mixing back together.  The measurement could be done by weight, but volume was more often used. It’s trivial to do this by ratio (“1 scoop into the small kettle, 2 into the big… 1 in the small, 2 in the big…”) without needing any dedicated measuring equipment at all. And having counted out the scoops once, future batches can hit the exact same temperatures just by remembering how close to the top each kettle was filled.

I think it’s pretty amazing that, armed with nothing more than two kettles, a ladle, and a fire, uneducated farmers were able to follow complex mashing schedules such as:

  • 20 minutes at 109 °F  (acid rest: phytase enzymes alter pH while beta-glucanase breaks down gums)
  • 20 minutes at 122 °F  (protein rest: proteolytic enzymes split up the longer protein chains)
  • 30 minutes at 149 °F  (saccharification rest: beta-amylase enzymes convert starch to sugar)
  • 30 minutes at 158 °F  (saccharification rest: alpha-amylase enzymes convert starch to sugar)
  • 10 minutes at 168 °F  (mash out: denatures all enzymes, freezing the mash chemistry in its current form)

and consistently get within a few degrees of each target temperature.

But what really blows my mind is how anyone managed to figure out the right temperatures to make great beer, long before we understood enzymes or starch molecules!  Those medieval monks must have had a LOT of spare time to experiment :-)

Comments (7)

  1. I bet none of the best beer came from mountainous locations, where water boils at a lower temperature.

  2. Kern says:

    Well, boiling point for water is not always 212 °F, depends on pressure.


  3. ShawnHargreaves says:

    Altitude affects boiling point, sure, but that just means Han's cousin who lives high in the alps needs to boil a slightly different proportion to get to the same target temperature.  Both can still get consistent results, they just can't use the same boil proportions at high and low altitudes.

  4. Andy says:

    Since you have to reboil some proportion doesnt' that mean your mash will have intermediate steps at 212 (which I assume is not good for the enzyme stuff)? Or are you just boiling the liquid and leaving the solids in the cooler kettle?

  5. ShawnHargreaves says:

    Andy – spoken like a true brewer-in-the-making!

    You're exactly right, whatever portion of the liquid you boil will have all its enzymes destroyed.  But this does not ruin everything, because the temparature steps (apart from the initial one up from the cold starting point, for which you can boil plain water with no grain in it yet) are typically not that far apart, so you are only boiling less than half of the total each time.  There will be enough enzymes left in the part you did not boil that the neccessary reactions can still take place when it is all mixed back together.

    Brewers actually prefer to boil a dense portion of the mash, with only just enough liquid to cover the grain, while leaving the thinner liquid part in the cooler kettle.  This is because enzymes are highly soluble, so the most enzymes will be in the thinnest part of the liquid.  Meanwhile, boiling the grain portion has the advantage of breaking down cell walls which makes the starch more easily accessible when it's mixed back in with enzyme-heavy liquid.

    That's the German approach, anyway.  English brewers did basically the same thing, but instead of boiling part of the mash, they started out with a relatively high grain/water ratio, and each time they wanted to raise the temperature they would boil and add a fresh quantity of water.  Same idea of using exact ratios to control temperature without needing a thermometer, but the English style gets more and more watery as the mash goes on, never boils the grain so it never wastes any enzymes, but also never softens the grains so gets less starch out.  More enzymes but less accessible starch typically ends up about the same in terms of how much beer you can get from a given quality of grain.

    English style is called an infusion mash, which is what most brewers do today.  German style is called a decoction mash.  The German style is more laborious (as I learned when I tried it for the first time last Sunday!) because you have to stir constantly to avoid scorching while boiling the dense grain/water mix, but I'm told it can produce a richer malty flavor because the boiling causes malliard reactions that caramelize some of the malt sugars.

  6. Shawn, the way you describe you get water at 66.6C but once you mix it with the grain (lets say that it is at 25C) the mix will reach a lower temperature. Your solution will work if you have way more water than grain. If you have 50% water and 50% grain youd need to take into account the masses of the grain and water as I did to make sure your final temperature is 66.6C.

  7. AQ says:

    Shawn – Please. Don't. Do. That.

    Not all of us are fans of beer to solve a brewing puzzle. And those of us who like puzzles, don't come to your blog for them. Stick to the main subject of your *MSDN* blog.