Article - Strike Temperature

By Alex Troncoso

Alex Troncoso getting a sample at Redhook Ale Brewery in Seattle.

As all mash brewers know, the temperature of the mash greatly affects the finished beer. Most books will list the optimum mash temperature range of 64 to 68 oC with a mash conducted at 68oC resulting in a dextrinous beer (ie. high final gravity) and a mash conducted at 64oC resulting in a well attenuated beer (ie. low final gravity). The difference in fermentability is a result of different enzyme actions during the mash. (In this article I won’t get into the function of alpha-amylase and beta-amylase enzymes at different temperatures – I’m sure that warrants a separate article and lots of information is already available in different books and the internet.)

Due to the high enzyme content of the malt on the market, the most critical time period during an infusion mash (as most of us use) is the first 5 minutes. This is when the enzymes are most active - producing a lot of reaction products (yes, sugars!!) and determining the fermentability of the wort. A mistake in the “strike” temperature of the mash liquor can result (most often) in a beer with a higher than desired final gravity. For repeatable results, it is important to achieve your desired temperature from the start of the mash.

Now, how do we calculate what the strike temperature of our mash water should be to achieve our target mash temperature? For those of us who don’t like numbers and mathematics, quit reading now. For the rest of us, read on and science will make everything clear as mud.

I will say that since I have started using the below information in my brewing that I repeatedly achieve my target final gravity. I know that if I mash at 64oC that I will end up with a beer at 1.006 and that if I mash at 67oC that I will end up with a beer at 1.012. There may be variations on these figures depending on the malt variety and yeast strain used, but these are values I have found using Wyeast 1056, American Ale and IMC Pale Ale malt.

The Concept of Specific Heat

Specific Heat is the amount of energy (calories) required to raise 1 gram of a substance one degree Celsius.

For water, this value is 1.0 cal/g-oC. For malt, this value is 0.4 cal/g-oC. As can be seen from these numbers, it actually takes quite a bit more energy to raise the temperature of water than the temperature of malt.

Strike Temperature Calculation

You will require the following information:

• Mass of malt (kg)
• Temperature of the malt (oC)
• Volume of water (litres) – technically this should be the mass of water, but since the density of water is 1, we can just use the volume.
• Desired mash temperature (oC)

To calculate the required strike temperature to achieve your desired mash temperature, the following equation can be used (adapted from “Brewing”, M Lewis and T Young, Aspen Publishers Inc, 2001, pg 102):

Example

I want to do a mash at 66oC and am mashing 5kg of malt with a temperature of 18oC with 13L of water.

Sorry to those that don’t like maths, but that’s how you do it!!! My preferred method is to heat up my mash water to slightly above the required temperature, transfer to the mash tun and then let cool to the target temperature. This way, you don’t have to worry about how much energy is required to heat up your mash tun. When the target is reached, quickly add your malt and stir, stir, stir!!! Using the above I usually get within 0.5oC of my target.

HAPPY BREWING!!!