Effects of a thicker mash

[The-Engineer-That-Brews]

In the past I haven't paid much attention to mash thickness other than swearing at it when the wort is running too slow for the recirculation pump. But typically I use about 3.0 litres per kg of grain.
Recently however I read about how a thicker mash slows down the rate at which mash enzymes (especially beta amylase) are destroyed by heat.

Beta amylase is an important enzyme if you're aiming to produce a highly fermentable wort for a crisp, dry beer.
Unfortunately it's a delicate beast - in a typical 66ºc mash its half-life is (at best) only about 7 mins:

[TU Vienna]


Kai Troester ('braukaiser') says: "The concentration of the mash (water to grist ratio) can have a significant impact on the mash performance".
He offers the following two charts:

​

β-amylase, 65ºc mash​

The first chart [Kunze, 2007] suggests that thickening the mash from 3 to 2 litres per kg doubles the half-life of β-amylase, from three to seven minutes (at 65ºc).
The second chart [Briggs, 2004] reveals that there may be a small price to pay however, as the same increase in mash thickness reduces the total sugar extraction from about 78% to 72%.

Make of that what you will - but for the time being I have increased my mash thickness to about 2.3 litres per kg.
Surprisingly, this doesn't yet seem to have given me any stuck mashes (that's jinxed it...)

 

[DocAnna]

This seems of particular relevance to the risk of over estimating the strike temperature, and would mean it was better to under do the temperature then heat up a bit if need be rather than go too hot.

 

[The-Engineer-That-Brews]

This seems of particular relevance to the risk of over estimating the strike temperature, and would mean it was better to under do the temperature then heat up a bit if need be rather than go too hot.

Good point - yes, I think that makes sense.
In fact these days following a suggestion by @Hanglow, I typically mash in really low (41° or so) before moving straight on up to conversion temps. The idea being that as I’m starting below the gelatinisation temperature, I don’t get any dough balls (seems to work). I also lower the grain basket gradually into the strike water to achieve an ‘under letting’ effect.

 

[moto748]

I guess a thicker mash tending to be less efficient (other things being equal) makes sense.

I generally avoid dough-balls by utilising my revolutionary 'bag-prodding' technique!
Obviously, this option is not open to those with closed systems.

 

[foxy]

For me, as I use 2 row, well modified malt so for single infusion I mash in at high temperature, I also have an extremely fluid mash. Why, as mentioned the more fluid mash will give a higher fermentability, mashing in at a higher temperature does mean that the Beta amylase does have a short life but works 3 times as fast. The higher the 'dough in' temperature the better the foam stability, if you have the pH under control.
When I say high, between 65 to 68C, pH 5.2 to 5.5 depending on what I am brewing.
Stout I use the 'high short mash'. Mash for 45 mins @ 63C Beta amylase rest. 45 mins @ 69C Alpha amylase rest.

 

[The-Engineer-That-Brews]

For me, as I use 2 row, well modified malt so for single infusion I mash in at high temperature, I also have an extremely fluid mash. Why, as mentioned the more fluid mash will give a higher fermentability, mashing in at a higher temperature does mean that the Beta amylase does have a short life but works 3 times as fast. The higher the 'dough in' temperature the better the foam stability, if you have the pH under control.
When I say high, between 65 to 68C, pH 5.2 to 5.5 depending on what I am brewing.
Stout I use the 'high short mash'. Mash for 45 mins @ 63C Beta amylase rest. 45 mins @ 69C Alpha amylase rest.

I hear you mate: hochkurtz for the win!
Mind you, for an 'extremely fluid' mash I'd be willing to put money on the line that you'd get identical results with half the time at the 63ºC rest :-)