Warning... slightly geeky post ahead ...
I do step-mashes by heating the wort while it's re-circulating. I've been wondering how long it takes the temperature changes to work their way into the 'body' of the grain, and whether that is something I need to adjust for.
In preparation, I modified my heating controller to log multiple channels and made a string of sensors to measure the temperature of the gain at different depths of the mash.
Yesterday was the first chance to give this setup a whirl.
I mashed 5kg of grain and 12.5L water, aiming for the following profile:
The following chart shows the first part of the results, where I mashed in and did the step up to 61º.
The red line is the 'kettle' temperature (the input to the heat exchanger). The 'Mash 1-5' lines show the temperature at increasing depths of the grain bed.
Observations:
For the remainder of the program I set the kettle temperature a bit over-target towards the end of the step in order to maintain the rate of temperature increase.
Observations:
Finally I continued monitoring while fly-sparging with 20L of water at 77ºC.
The results here are harder to interpret because I was having trouble balancing the inflow and drain rates, and I increased the temperature of the sparge water towards the end.
Observations:
Conclusions:
I do step-mashes by heating the wort while it's re-circulating. I've been wondering how long it takes the temperature changes to work their way into the 'body' of the grain, and whether that is something I need to adjust for.
In preparation, I modified my heating controller to log multiple channels and made a string of sensors to measure the temperature of the gain at different depths of the mash.
Yesterday was the first chance to give this setup a whirl.
I mashed 5kg of grain and 12.5L water, aiming for the following profile:
- 56º (protein rest) for 15 min;
- 61º (beta amylase) for 15 min;
- 68º (alpha amylase) for 30 min;
- 75º (mash out) for 5 min;
- maintain grain bed at approx 77º during the sparge.
The following chart shows the first part of the results, where I mashed in and did the step up to 61º.
The red line is the 'kettle' temperature (the input to the heat exchanger). The 'Mash 1-5' lines show the temperature at increasing depths of the grain bed.
Observations:
- The grain bed settled at about 1.2 degrees below the temperature of the kettle (heat exchanger input).
- At the start of the step the grain temperature increased at about 0.7 degrees per minute, then tailed off as it approached the target temperature.
- While the temperature was changing, the bottom of the bed lagged about 2 degrees / 3 minutes behind the top.
For the remainder of the program I set the kettle temperature a bit over-target towards the end of the step in order to maintain the rate of temperature increase.
Observations:
- The grain pretty much hit the temperatures and durations that I was aiming for. Monitoring the temperature of the grain was very helpful.
- The temperature took longer to change between steps than I'd expected (about 10 mins), however I was able to reduce this by increasing the kettle temp by about 3 degrees higher for the last 3-4 mins.
- The bottom of the mash was a bit late reaching temperature at the beginning of each step but was equally late beginning the next - so the overall delay tended to cancel out.
Finally I continued monitoring while fly-sparging with 20L of water at 77ºC.
The results here are harder to interpret because I was having trouble balancing the inflow and drain rates, and I increased the temperature of the sparge water towards the end.
Observations:
- The overall temperature of the grain bed was maintained reasonably close to 77ºC during sparge and run-off.
- The temperature of the surface grain fell rapidly once the liquor was run off below that level.
Conclusions:
- This exercise taught me a lot about the behaviour of my setup and how to get the best from it.
- I don't think I will worry in future about the temperature difference at the bottom of the mash. It certainly exists, but the time delays tend to equalise out between the start and end of each mash step.
- It took longer to move the mash between the rests than I had previously expected. 'Over-driving' a little towards the end of each step did seem to be worth it however.