Monitoring mash temps - results

[The-Engineer-That-Brews]

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:

• 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:

1. The grain bed settled at about 1.2 degrees below the temperature of the kettle (heat exchanger input).
2. 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.
3. 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:

1. The grain pretty much hit the temperatures and durations that I was aiming for. Monitoring the temperature of the grain was very helpful.
2. 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.
3. 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:

1. The overall temperature of the grain bed was maintained reasonably close to 77ºC during sparge and run-off.
2. The temperature of the surface grain fell rapidly once the liquor was run off below that level.

Conclusions:

1. This exercise taught me a lot about the behaviour of my setup and how to get the best from it.
2. 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.
3. 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.

 

[phettebs]

Excellent work. Nothing better than good hard data to back up a process!

 

[Hanglow]

Nicely done. That's useful info to know for mashing and making it more efficient

If you want to see how your mash is progressing, then take gravity samples at the end of each step. You can see then the effectiveness of each step, with regards to expected conversion.

On the temperatures them selves, I wouldn't bother with the protein step for the vast majority of beers, but doughing in at that temperature is good as it is well below geletanisation temps for malted barley so you will get no dough balls. Once the grain is saturated and well mixed, immediately ramp up to beta.

Because geletanisation temperature of barley is about 64c or so, it is useful to spend a decent amount of your beta rest at that temperature. This depends on the malt though from batch to batch. You'll get better conversion rather than using a lower temperature below gel temp. Although a short step lower like you did at 61c is fine

68c is fine for a short step, but you would be better served raising that to 72c, alpha amylase works great at that temperature and it is a good temperature to help with foam formation and retention and gives good body to beers, even if well attenuated.

Of course great beers can be made with a single infusion, but imo getting to grips with proper step mashing can really help nail some beers and allows less compromise to be made by the brewer. Plus it's a bit nerdy

 

[The-Engineer-That-Brews]

Nicely done. That's useful info to know for mashing and making it more efficient [...] imo getting to grips with proper step mashing can really help nail some beers and allows less compromise to be made by the brewer. Plus it's a bit nerdy

Thanks for those kind words and the helpful info... I'm definitely still learning path and will be for some time.

Concerning rest temperatures, I've been basing what I've done so far on a byo article called 'the science of step mashing'. It doesn't mention 'gelatinisation' though - what's all that about?

Just FWIW the reason I rested at 56ºC was not really for 'protein' (that was just me being sloppy with my labelling) but for beta-glucanase: as I was using floor-malted lightly kilned grain that I suspected might be slightly undermodified (I say, trying to sound like I know what I'm on about... )

Also the reason for the 68ºC was (probably completely misguidedly) to sneak into alpha amylase territory for a bit of 'body' (the article says optimal for alpha is 68-72) with a tiny bit of beta amylase still going on to help with starch conversion...?

For foam and head retention, which has been a bit of an issue in the past, I added 200g of carapils for the dextrine - and goodness me, it seems to have worked because when I aerated the wort it looked like someone had tipped bubble bath in there!

:hat:

 

[chthon]

Starch gelatinisation

TLDR;: Basically this helps making starches more accessible to enzymes, and is thus good for your conversion.

 

[The-Engineer-That-Brews]

Very interesting - thanks

 

[DocAnna]

Just catching up, I'd seen the summary chart on your brew thread though. Are your probes in the mash at the edge of the container or in the centre of the mash? The temperature in the step mash seems very consistent and I'm wondering whether an edge effect of the fluid flow could be occurring with greater flow at the boundary between grain and the container wall. This boundary effect and flow would be magnified by the presence of the probes and their support post. Testing if you get the same graph from the probes in the centre of the mash might help but it would be difficult to eliminate the boundary effect altogether?

Anna

 

[The-Engineer-That-Brews]

Yes - very good point...! I'd wondered about the boundary effect at the container wall too. In the end, I stuck the sensor string diagonally down through the mash bed so that that the bottom bit ended up more or less in the centre of the base :-)

 

[The-Engineer-That-Brews]

FWIW, I've tried to design my recirculation setup so as to give fairly evenly distributed flow: at the top the liquor is fed in via a perforated spiral pipe laid on top of the grain; and at the bottom the whole base of the mash tun is a 0.2mm stainless steel mesh above a sump.
The intention is to get the same flow across the whole cross section, but of course it's hard to know how well it achieves this :-)

 

[The-Engineer-That-Brews]

I have a Cunning Plan: temperature sensing tee pieces ...

The idea is to use them during tomorrow's brew day to monitor the temperature flowing into and out of the mash (via the HERMS)