Mash thickness and efficiency.

[Dave70]

My new 50L keg mash tun setup lets me basically dump the grain into the full volume of water I need for a brew, most days around 33L. So at for around 5 kg of grain that's around 6.6 liters per kilo of grain. I use to go about 3L per kilo in the old esky set up as was recommended to me.
So can having a to thin mash cause problems?
I've so far only produced one batch with the new set up and though OG / FGs were pretty good but haven't had a chance to taste it yet.

 

[manticle]

There's various bits of science on mash thickness, etc but I'm not sure how relevant it is to small scale home brewing when you consider some 3V types mash in at 2.5 kg per L and most BIABs have full volume of liquor immediately. I can look some stuff up when I get home if you're interested but what you are doing sounds no different to what BIABers do all the time. BIAB efficiency is usually on par or slightly higher, all things being equal.

 

[Dave70]

If you're taking the time to look it up I'll certainly be interested to read it.
Cheers.

 

[brewbienewbie]

Yeah I just picked up a keggle which I'm looking at using for full-volume mashes so I'd be interested in this too.

 

[manticle]

OK - I'll try and summarise my fairly quick reading:

Brewing Science and practice seems to suggest that mashes up to 7:1 will result in greater extraction. The suggestion is that thicker mashers can be problematic.

Here's a quote from the relevant section

Changes in mash thickness (liquor/grist ratio) have significant effects on mash
performance (Hind, 1950; Hopkins and Krause, 1947; Harris and MacWilliam, 1961;
Muller, 1989; 1991; Table 4.14). Very concentrated mashes, (liquor/grist <2:1ml/g), are
difficult to mix and pump, extract recoveries are reduced, starch conversion is slowed
down, worts are more concentrated and viscous, TSN and FAN are increased and more
high molecular weight nitrogenous substances remain in solution, but a lower proportion
of hydrophobic peptides (relative to the amount of extract) are present, causing `high
gravity' beers to have poor head retentions (Bryce et al., 1997). In the concentrated
mashes both the enzymes and their substrates are more concentrated. Some enzymes
(proteolytic enzymes, disaccharidases) are more stable in concentrated mashes producing
higher proportions of TSN and hexose sugarsrespectively. 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.
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. Brewery worts contain 0-40% more
soluble nitrogen than laboratory analytical worts. It was reported that mashes made with
39% solids give worts with maximum extract yields while worts with the highest
fermentabilities are given by mashes made with 16-32% solids. The effects of mash
concentration on extract yield are also present when adjuncts are included in the mash
(Harris and MacWilliam, 1961; Muller, 1991; Fig. 4.14).
As the grist hydrates water is bound, and there is a rise in temperature caused by the
release of heat (the `heat of hydration'). As the mash proceeds water is utilized in
hydrolyses, a water molecule being consumed when any bond is split. Some water is
more or less firmly bound (by hydrogen bonding) to starch, to sugars in solution, to -
glucans, to pentosans and to other substances reducing the concentration of `free' water.
In all-malt mashes and mashes made with 50:50 malt and barley or wheat starch the
extract recovered falls very sharply as the liquor/grist ratio is reduced below about 2.5
(Fig. 4.14). 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 Litre degrees/kg, while at a ratio of 7:1 the extract
was 311 litre degrees per/kg. The extent of water binding becomes progressively greater as mashes
become more concentrated and there isinsufficient free water to permit the gelatinization
of much of the starch. The addition of more enzymes to a very thick mash does not
quickly convert the ungelatinized starch and so does not enhance the extract obtained.

Lewis and Bamforth in 'essays in brewing science' suggest that mashing in at full volume (obviously talking about commercial practice) would require much larger vessels but anything less than 2.5:1 is problematic. Thicker mashes have a greater concentration of enzymes but a greater concentration doesn't necessarily equate to better performance (as suggested by briggs, boulton et al - brewing science and practice). Thicker mashes resist degradation from quick heating (such as in infusion or decoction mashing), dilute mashes are more easily mixed and heat exchange is more efficient. Might be one for the HERMS guys to consider. Range spoken of is 2.5:1 up to 5.1:1 (water to grain)

Fix (principles of brewing science) suggests thick mashes favour proteolytic activity while thin mashes favour carbohydrase activity but these effects are small.

Finally (at least as far as the sciencey texts I have at hand go) de Clerck, writing in the 50s but still well respected as far as I know, suggests ratios of 2:1 - 4:1 are typically used. Infusion mashing such as that carried out in the UK (which he suggests are primitive), requires thicker mashes as the mash temperature will be raised by underletting/infusion. Thinner mashes are generally more efficient and more modern brewing processes utilise them.

None of these seem to suggest that mashing at a higher ratio is a bad thing - indeed it seems quite the opposite. The only limitation mentioned is equipment size with the lowest ratio mentioned being 1.5:1 and the highest 7:1.

No idea if that helps but it is hopefully of interest and should hopefully put to bed the idea that lower concentration of enzymes necessarily = less extract/conversion, especially with well modified, modern malts.

 

[pk.sax]

Absolutely. Adding to what you've said, I'm learning new things from what you've posted.

I mentioned on another forum, your l/g ratio is also of concern in the mash tun design. The material (steel vs aluminium) and it's thermal capacity to hold temperature play a part as with a mash tun that doesn't hold temp too well decreasing the ratio provides more thermal mass per unit volume and can give a stabler temperature. Of course, insulation helps.

It is like doing a crepe I suppose, thick pan at constant sort of heat vs thin pan with on demand heat.

 

[Bribie G]

I was only reading something about mash thickness on Braukaiser last night and he confirms that thinner mashes are more efficient and the enzymes work better. This is particularly so in German brewing as they tend to do their steps by adding boiling water as opposed to heating a steam jacketed vessel as in the UK. Google Braukaiser Infusion Mash for details.

OP is in a very fortunate position here, just add a burner to your mash tun and head off to Spotlight B)

 

[RelaxedBrewer]

I have read that mash thickness can effect the way alpha and beta enzymes act and temperature rests may be slightly different (ie a 65C rest with 2L/kg is not exactly the same as 65C rest with 5l/kg).
However, according to experiments on Braukaiser this is incorrect.

From Braukaiser
"Contrary to common believe no attenuation difference was seen between a thick mash (2.57 l/kg or 1.21 qt/lb) and a thin mash (5 l/kg or 2.37 qt/lb). Home brewing literature suggests that thin mashes lead to more fermentable worts, but technical brewing literature suggests that the mash concentration doesn't have much effect in well modified malts [Narziss, 2005]. Briggs cites data that doesn't show a change in fermentability when the mash thickness is changed [Briggs, 2004]. This was confirmed by these eperiments where all the data points were on the same curve that had already been established in the temperature experiment."

The Braukaiser experiment also showed that thinner mashes result in a higher efficiency when mashing at higher temps. So this could be an added bonus for when mashing for a fuller body.

http://braukaiser.com/wiki/index.php?title=Effects_of_mash_parameters_on_fermentability_and_efficiency_in_single_infusion_mashing#Mash_thickness

"

 

[Parks]

I reckon it would mean more with a shallower mash tun where the grain is more spread out and not compacting on itself like it tends to in a keggle shaped tun.

 

[Bribie G]

Most commercial mashes get stirred as well.

 

[stm]

OP is in a very fortunate position here, just add a burner to your mash tun and head off to Spotlight B)

What are you suggesting Bribie? Heat water, mash and boil in the same vessel? You're pulling our leg....