Mash Thickness and Fermentability

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Orangevango

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Has anyone done any research on the effect mash thickness has on the fermentability of wort? I ask because I made an English porter that I felt needed more body, and I was wondering if I should consider thickening up the mash next time in addition to raising the temperature. I normally mash at 2 qts./lb.
 
I think two quarts is certainly on the higher end of what most people do.
I recently bumped mine up from 1.10 quarts/pound to 1.30,
 
Mash thickness will slightly affect the fermentablitiy of your wort, but mash temp will affect it much greater. It's true that thinner mashes tend to produce a slightly more fermentable wort, while thicker mashes produce a more dextrinous wort, but the difference will be maybe 2 points on your FG. If you want more body, you should either up your mash temp or alter your grain bill to include more caramel malts.
 
There's a really good section on this in Brew Science (in my sig) Chapter 4.3.7

a snipet:
At high mashing temperatures thicker mashes give worts with higher fermentabilities (Muller, 1991; Fig. 4.13). On the other hand, at `normal' mashing temperatures weaker mashes give more fermentable worts. The high concentrations of sugars and dextrins present in thick mashes can inhibit the amylases. Enzyme inhibition is due to the reduced availability of free water as well as to the sugars acting as competitive inhibitors.

Generally, altering the liquor/grist ratio at values over 3 has comparatively minor effects, but these are not necessarily negligible. In a particular case mashing with a liquor/grist ratio of 2.5 : 1 gave an extract of 291 l ë/kg, while at a ratio of 7 : 1 the extract was 311 l ë/kg. The extent of water binding becomes progressively greater as mashes become more concentrated and there is insufficient free water to permit the gelatinization of much of the starch.
 
I now always mash in at 2.0qt/lb, and have seen no drop in my FG. I have been brewing this way for quite a while now and my FGs are in line with where they were on the same beers mashed at 1.25qt/lb

You have to be careful when you start saying something broad like "thin mash". 2.0qt/lb is thinner than some do, but definately not thin when you look at BIAB methods and the like.

What is a "thin mash"? 1.5qt/lb, 2.0qt/lb, 3.0qt/lb? When these statements are made aobut "thin mashing" creating a more fermentable wort, there are never any specifics given... I am sure a thin mash may contribute to a lower FG, but in my experience 2.0qt/lb isnt thin enough... so what do you mean by "thin" when you say thin mashing creates this lower FG? Any specifics?

I would suspect that anyone who has actually mashed thin enough to see a noticeable drop in FG would have some exact numbers, and done this over several batches to be sure that it isnt a fluke.
 
in brew science, fig 4.13 they don't really start to see a drop in fermentability until the 3:1 ratio mashing at 75C - 167F. They don't list results at lower temperatures, but based on what is written and what looks to be a trend in the graphs, the lower the temperature the thinner the mash you can get away with and still not effect fermentability.

Even then, no one mashes at 167 I would suspect and I bet no one mashes at 3qt/lb either, so at our temperatures this seems to just be a non issue - thin mashes. If you look at the graph it is clear that temperature is the determining factor in fermentability much more than mash tickness.
 
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