Effect Of Mash Temperature On Final Gravity

[buttersd70]

My question is this. For a particular grain bill, knowing the potential (or at least a good average) of your ingredients, and using a yeast with a given apparent attenuation, can the final gravity be estimated (or even determined) for a given strike temperature.

Obviously, you can use FG=OG-(Atten x OG), but this does not take into account higher mash temp creating more lower fermentables than a low mash, and vice versa. I would presume that this is ok for the mean temp in the sacch range, ie 65 or thereabouts. But what if you mash at 69, or at 61?

Is there a way that is more specific than just assuming it will end a couple of points higher if you mashed at 68 or 69?

Assumptions for this topic are
- grain bill does not vary
- yeast strain and viability does not vary
- methodology and equipment does not vary, with the exception of the mash temperature.

The main reason that I ask is that I would like to be able to check what the FG should be, because we do, after all, brew for the final result.
(and I'm completely obsessed by the thought that if you measure precicely, you may or may not achieve precision - but if you measure imprecisely, you are guaranteed to achieve imprecision)

Any thoughts would be appreciated.

 

[Adamt]

Best way to do this at home is experience. There are far too many variables in home brewing equipment to have exact numbers or correllations to use in the community.

For example:

How accurate and how precise is your mash thermometer? Where is your thermometer in your mash tun? Is your mash thermally homogenous (well mixed)?

How accurate and how precise is your hydrometer? Is your sample free from bubbles? Error of parallax?

 

[mika]

Start brewing. Comes down to knowledge of your system and yeast. It can also be influenced by your water to grist ratio, whether your thermometer is calibrated to a known standard, where you're measuring the mash temp in your tun.
Basically it's a mash it and see kinda deal.

 

[bigfridge]

The main reason that I ask is that I would like to be able to check what the FG should be, because we do, after all, brew for the final result.
(and I'm completely obsessed by the thought that if you measure precicely, you may or may not achieve precision - but if you measure imprecisely, you are guaranteed to achieve imprecision)

Any thoughts would be appreciated.

buttersd70,

The theory of the enzyme reactions involved is well known and can be expressed as a series of complex equations, but as others have said it is very difficult to know what the exact temperature distribution is during your mash.

Breweries who are concerned about such things approach this from a more practical perspective and perform a forced fermentation to determine the limit attenuation. This is easy to do and just involved collecting a sample of wort (say 500ml in a 1.2 litre soft drink bottle) and pitch a heap of yeast - one packet wouldn't be too much.

This sample is fermented at room temperature and given a shake a couple of times each day. The large amount of yeast together with the high temperatures and agitation will ferment down to the final gravity in just a few days and this allows you to know the expected final gravity of the actual wort well before the main fermentation is over.

You can use any yeast you like for the test as the different strains have effectively the same attenuation under these conditions.

But as others have said, does it really matter - just brew and enjoy.

David

 

[Adamt]

I think I understand what you're getting at but still don't understand why this is at all necessary.

Brewing is a very very complex process, and at a home-brewing scale the planning stage is only a very rough estimation of what will happen during brewing. The idea of having everything constant but the mash temperature is good but is not going to happen.

 

[Adamt]

You sound like one of those weird pure maths people... *cough*

Try and track down a copy of "Brewing: Science and Practice" by Briggs et al... Chapter 4 should be enough to have you sucking your thumb in the corner for a week

 

[Thirsty Boy]

somewhere between that bigfridge and mika said from my perspective.

I know that at work, they are able to predict FG based on a variable input - ie: they want the FG of a fermentor full of Carlton Draught to be the same every time, no matter whether the DP of the malt they use is a little different, whether the batch of adjunct that is being used this time has a different ratio of fermentable to non-fermentable sugars etc etc. They will generally achieve the changes needed with a small change to the sach rest stand time, but also by changing the ratio of different adjunct sugars (we usually use a combo of sucrose and a high maltose adjunct in syrup form) and in really extreme circumstances they might alter the temperature of the sach rest.

But what I am saying really is - if you know exactly whats going in and you have lots and lots of experience brewing on your system, then yes... absolutely you can predict whats going to come out, down to tenths of a Plato.

From a homebrewers perspective - even the keenest brewer brews less batches in a year than someone like my employer does in a few days, and most likely doesn't get a separate malt analysis sheet for every single batch of malt they use. so the information about how your system works and what you are putting into it is much less precise.

But if you use the same sort of malt from the same provider each time, you keep an eye on the spec sheets to make sure nothing is radically different in a given batch and as mika said, you get brewing and build up a body of experience about how your system works, then there is no reason why you couldn't and shouldn't get the point where you can predict your FGs to the 1.01? level with a fair amount of consistency.

Of course.... that leaves your yeast management completely out of the picture - its gonna help a lot if you only use one or two different strains and you learn how they work back to front.

Theoretically : Yes - practically : sorta

Thirsty

 

[crozdog]

Try and track down a copy of "Brewing: Science and Practice" by Briggs et al... Chapter 4 should be enough to have you sucking your thumb in the corner for a week

available as a torrent

check this out

 

[MHB]

This little table in Graham Wheelers book Home Brewing, the CAMRA Guide is a pretty good starting point.
It gives the relative amounts of maltose and dextrins produced at various temperatures and for different pH values.

MHB

View attachment 20295

 

[wessmith]

Gidday Mark,

These numbers will be for UK malts and probably floor malted varieties. Our local malts cant compete. Bottom line is if you want to brew English styles, then use English malts. Full stop.

Wes

 

[MHB]

Wes

Fair point

But would a similar trend be noticeable for Oz malts (well maybe not Schooner) or are the local malts just too well attuned to the needs of the mass market brewers? Who from what I can gather are mashing far hotter than home brewers would expect; then adding lots of sugar to make up for the reduced fermentability.

Wheeler suggests about a 7% difference between Hot and Cold mashes, could we apply a smaller number to get some idea of the difference?

MHB

 

[wessmith]

Wes

Fair point

But would a similar trend be noticeable for Oz malts (well maybe not Schooner) or are the local malts just too well attuned to the needs of the mass market brewers? Who from what I can gather are mashing far hotter than home brewers would expect; then adding lots of sugar to make up for the reduced fermentability.

Wheeler suggests about a 7% difference between Hot and Cold mashes, could we apply a smaller number to get some idea of the difference?

MHB

Schooner excepted, I would expect to see a similar result with local malts - except it would be around 2 to 3 degrees higher in temp across the range. While our local maltsters do produce "ale" malts, they tend to be just high colour pale malts. The culture of malting in Australia does not allow for extended germination and kilning regimes as are used in the UK for the traditional craft malts. Dont get me wrong, all the big maltsters in the UK ALSO produce mainstream products on short germination cycles just as we do here. And they are just as bland and "maltless" as our examples.

Producing specialty malts for craft brewing and home brewing is a very niche business which few maltsters are willing to enter. We should be thankfull for the few local and imported products that are available and make the most of them.

Unfortunately some recent experiences with startup brews on our equipment installations have left me dismayed at the current quality of some of our local malts. Sure we have had a couple of bad seasons, but that shouldnt stop the screening out of undersized grains or the cleaning of the finished malt to get rid of the dust. Its bad enough having to cope with high protein/over modified product without also seeing wasted extract shovelled out of the mash tun.

Wes

 

[Stuster]

Wes, what maltsters are you favourite then (of the ones we can get here)? Do you rate Weyermann? How about Bairds?

(Totally understand if you can't comment for professional reasons.)

 

[Hargie]

....i'm no Wes Smith,who i met about 12 months ago and who clearly knows brewing inside out... but for mine, Weyerman = king of malts...Maris Otter is sensational as well....

 

[wessmith]

Wes, what maltsters are you favourite then (of the ones we can get here)? Do you rate Weyermann? How about Bairds?

(Totally understand if you can't comment for professional reasons.)

Thats an easy one Stuster - the only imported malts around at the moment are Weyermann and Bairds. Weyermann are recognised internationally as THE BEST producer of specialty malts - they have no peer. But when looking for English ale malts, I have found nothing to equal the quality, consistency and range of Thomas Fawcett. Sadly TF is not currently available here in Australia however the Bairds offerings arent too bad but just dont have the depth of flavour that floor malted ale malts can give.

Wes

 

[Steve Lacey]

If you'll excuse me extending the thread hijack just a little longer ...

Wes, what do you think of Crisp MO? It is what we get here in Japan.
Regards,
Steve

 

[///]

My training has made predictable results based from using a specification for the beer being produced. From there the rest is good management and technique to work with the variences that brewing throw you. You can still brew to a specification no matter how often you brew and to what size brewery. The principles are the same. Also deliriously happy with my malt supplier for quality and consistency... lucky us I guess.

 

[wessmith]

If you'll excuse me extending the thread hijack just a little longer ...

Wes, what do you think of Crisp MO? It is what we get here in Japan.
Regards,
Steve

Hi Steve,

I have never personally brewed with the Crisp product but have tasted a few ales produced from their floor malted ale malts. UK brewers comments usually bracket Crisp malts with Simpson malts - very good quality, very reliable supply but not quite up there in the flavour/aroma stakes with TF and Warminster. That said, you still have a very good malt. Actually, TF still use a direct Anthracite coal fired kiln for their floor malted offerings - not sure about Warminster though.

The other point to note is the sourcing of the barleys for floor malting - you cant use just any old crop of MO (or Halcyon or GP). The grains must be plump and full, low in protein and readily (evenly) germinate. All these traditional barley strains are low yeilding by present day standards and are mostly contract grown for a particular maltster. Even that is not sometimes enough to guarantee the farmer a premium sale as any slippage in quality can mean the barley is fit only for animal feed. These factors tend to rule out the larger maltsters when it comes to sourcing specialist barleys - they tend to go with some of the more recent strains such as Optic which is grown in larger volumes and more reliable in a dodgy season.

Wes