Mash temperature questions/clarification

Help Support The HomeBrew Forum:

Buffers brewery

Regular.
Joined
Dec 11, 2019
Messages
346
Reaction score
169
Location
Bognor Regis
So far, I have set my mash temperature to 65 C and mashed for an hour, recirculating the wort through a water bath heat exchange to keep the temperature constant. My mash tun is a cool box with no heater. For a 5kg grain bill I’ll use 3.5 gallons of water. At the end of the hour I drain the wort off (get about 2 gallons of high SG wort - +1.070) and then refill the tun with water (about 2 gallons) and do second (mini) mash at 70 C for 15 minutes then drain the wort. Then a third and final (mini) mash (another 2 gallons of water) at 70 C.
Now, I want to make a beer around 5%ABV with good body and sweet. So my understanding is at 65 C you get fermentable sugars and at 70 C non-fermentable sugars and ”body”. I also believe that at the end of an hour mash, all the starch should be converted to sugar irrespective of temperature?

How do I change my method/process to get a wort that I know has the right amount of fermentables (SG) but also will have sweetness and body (non-fermentables)? I’m guessing shorten the initial mash and up the grain bill?
 

cushyno

Landlord.
Supporting Member
Joined
Jun 23, 2018
Messages
973
Reaction score
549
Location
Ormskirk
Shortening mash and upping grain bill is an easy option. You could up your grain bill by 5% and shorten to 45 minute mash, but that may not solve the problem.

By doing two sparges at 70degC you're effectively doing 90 minutes mashing. The longer the mash, the better conversion, but also the enzymes will have more time to break down long chain sugars to short chain and hence more fermentable wort. At 70degC the enzymes that break down the long chain sugars are less active, but given more time and any cold spots in your mash, they'll still be working to a degree. Besides, as you've already done 60 minutes mashing at 65degC, the extra two lots of 70degC won't help get your non-fermentable sugars, they've already been converted to fermentables in the prior hour (mostly in the first 20 minutes).

My understanding is that sparge temperature should be high enough to stop the enzyme activity, i.e. 75degC, but not too high to cause astringency from tanins. That way your sparge will mostly be to wash the existing sugars out of the grains rather than to convert more starches or long chain sugars to simple sugars.

I'm no expert, but I'd suggest you mash higher if you want more body, no lower than 68degC. After 60 minutes, do your one or two sparges at 75degC. Two should get you increased efficiency as you'll wash out progressively more of the sugars while not converting any more.
 

strange-steve

Quantum Brewer
Joined
Apr 8, 2014
Messages
4,751
Reaction score
3,662
Location
Galle Crater, Mars
There will always be a mixture of fermentable and non-fermentable sugars in the wort, and as you're aware mash temperature is one of the main variables that we can manipulate in order to adjust the ratio.

A low temperature (say 63°C) favours the beta-amylase enzyme and will result in a beer which is thinner, drier, and stronger, whereas a high temperature (say 70°C) favours the alpha-amylase enzyme and will give a beer that is fuller bodied, sweeter, and weaker (in alcohol that is).

Because we're talking about enzymes, they don't work in an "on/off" way but rather within a specific range, and luckily for us there is an overlap in those ranges. Around 67°C is considered a good compromise between the two, but mash temperature is a continuum and so you can customise to the desired style and your particular taste.
 

Buffers brewery

Regular.
Joined
Dec 11, 2019
Messages
346
Reaction score
169
Location
Bognor Regis
So, the brew I’ve just done was mashed as I described above and got 25 litres into the FV with OG 1.054. I’m hoping for an FG of around 1.012. Currently, after 4 days, it’s 1.020.
So, if I were to do this brew again and upped the mash temperature to 68 C, the OG should, all things being equal, be ITRO 1.054 but a mix of fermentable and unfermentable. I suppose the problem for me is not knowing what that mix is and what FG I should expect and therefore how to adjust the grain bill to achieve the desired ABV and “body”.
 

cushyno

Landlord.
Supporting Member
Joined
Jun 23, 2018
Messages
973
Reaction score
549
Location
Ormskirk
It's always going to be trial and error for us at homebrew levels, but there is some science in it.

Your yeast manufacturer will state an attenuation range for the yeast Let's say the yeast is S04 with attenuation range of 74%-82% . There are many variables that will affect the attenuation, such as fermentation temperature, nutrients, and quality of wort. Your recipe will usually shoot for the middle figure of a recommended yeast's range, in this case 78%.

Taking your example gravities of 1054 and 1012 (5.5%ABV), that gives approximately 1-(12/54) = 0.78, or 78% attenuation. Bingo! Bang on target for S04.

If your have fewer fermentables your attenuation will be lower than 78%, but probably not as low as 74%. You only go that low if you mashed really high and fermented at lower temperatures.
Assuming you mash at 70degC and have a healthy fermentation but don't want esters so keep the temperature around 20degC, you may be in the region of 75% attenuation. With the same starting gravity, (1-0.76)*54 = 13.5, therefore final gravity may be 1.0135 and 5.3%ABV. So there's not a lot in it.
 

Buffers brewery

Regular.
Joined
Dec 11, 2019
Messages
346
Reaction score
169
Location
Bognor Regis
Wow! Like a bit of science! Thanks for that @cushyno thumb. Got a bit hung up on the sums (you talked about 75% attenuation and the put 0.76 in your formula! Put that down to finger trouble). But I get what you’re saying, there’s not a great loss in ABV with a slightly higher FG. And I suppose I’m going to have to brew one to see if the ABV/body mix is what I’m aiming for. I was considering doing two brews, one short (30 minutes @70 C) with a small quantity of pale malt and all the other malts for the body part. Drain that off the put the rest of the pale malt on top and mash for 30-40 minutes at 65 until complete conversion, then mix the 2 worts for the boil. Probably a bit OTT. Will try you and @strange-steve suggestions and mash at 68 C and see what occurs. Thanks bothacheers.
 

strange-steve

Quantum Brewer
Joined
Apr 8, 2014
Messages
4,751
Reaction score
3,662
Location
Galle Crater, Mars
Wow! Like a bit of science! Thanks for that @cushyno thumb. Got a bit hung up on the sums (you talked about 75% attenuation and the put 0.76 in your formula! Put that down to finger trouble). But I get what you’re saying, there’s not a great loss in ABV with a slightly higher FG. And I suppose I’m going to have to brew one to see if the ABV/body mix is what I’m aiming for. I was considering doing two brews, one short (30 minutes @70 C) with a small quantity of pale malt and all the other malts for the body part. Drain that off the put the rest of the pale malt on top and mash for 30-40 minutes at 65 until complete conversion, then mix the 2 worts for the boil. Probably a bit OTT. Will try you and @strange-steve suggestions and mash at 68 C and see what occurs. Thanks bothacheers.
That's sort of like a step mash, which may be worth looking into. It's something I often do with German and Belgian styles, mash in at 63c for half an hour or so then raise the temperature to 70c for half an hour.
 

strange-steve

Quantum Brewer
Joined
Apr 8, 2014
Messages
4,751
Reaction score
3,662
Location
Galle Crater, Mars
Also as much as I love the maths theory, it's still only an estimate because there are so many variables at play. The attenuation ranges given by yeast manufacturers aren't terribly useful unless you're using the same mash parameters they used in their test batches. Final gravity is always an estimate, unless it's a recipe you've made before, and even then it may not be the same.
 

Buffers brewery

Regular.
Joined
Dec 11, 2019
Messages
346
Reaction score
169
Location
Bognor Regis
That's sort of like a step mash, which may be worth looking into. It's something I often do with German and Belgian styles, mash in at 63c for half an hour or so then raise the temperature to 70c for half an hour.
Interesting! Does it matter which way round you do it? Don’t know why I thought doing the high temperature first and draining the wort off before adding the second lot of grain and strike water.
 

cushyno

Landlord.
Supporting Member
Joined
Jun 23, 2018
Messages
973
Reaction score
549
Location
Ormskirk
You were right spotting the 75/76 degree mix-up, I started changing my example halfway through. Oops!

Steve's right about the theory too. The attenuation figure of yeasts are just a guide. I recently got 95% from the Lallemand Saison yeast even though the spec sheet show its maximum as 92%.
 

strange-steve

Quantum Brewer
Joined
Apr 8, 2014
Messages
4,751
Reaction score
3,662
Location
Galle Crater, Mars
Interesting! Does it matter which way round you do it? Don’t know why I thought doing the high temperature first and draining the wort off before adding the second lot of grain and strike water.
Yes, low temperature first to limit denaturing of the beta enzymes. Although if you're adding more grain that shouldn't be an issue.
 

Buffers brewery

Regular.
Joined
Dec 11, 2019
Messages
346
Reaction score
169
Location
Bognor Regis
Yes, low temperature first to limit denaturing of the beta enzymes. Although if you're adding more grain that shouldn't be an issue.
My thinking was that the first batch of grain would be “steeped”? (if that’s the correct term) to produce mostly unfermentable sugars for the body, then after running off the wort, add a goodly quantity of pale malt onto the already warm mash to produce the fermentable sugars. Is there a flaw in my original idea?
 

strange-steve

Quantum Brewer
Joined
Apr 8, 2014
Messages
4,751
Reaction score
3,662
Location
Galle Crater, Mars
My thinking was that the first batch of grain would be “steeped”? (if that’s the correct term) to produce mostly unfermentable sugars for the body, then after running off the wort, add a goodly quantity of pale malt onto the already warm mash to produce the fermentable sugars. Is there a flaw in my original idea?
I'm not sure if there's a flaw, it's not a technique I've come across before, but I'm certain you could get the same result from a single infusion mash which targeted each enzyme to the appropriate degree.

If up to now you've been mashing at 65C then I suggest for your next batch you follow @cushyno's idea and mash at 68C instead.
 

Buffers brewery

Regular.
Joined
Dec 11, 2019
Messages
346
Reaction score
169
Location
Bognor Regis
I'm not sure if there's a flaw, it's not a technique I've come across before, but I'm certain you could get the same result from a single infusion mash which targeted each enzyme to the appropriate degree.

If up to now you've been mashing at 65C then I suggest for your next batch you follow @cushyno's idea and mash at 68C instead.
Sounds like a plan. I like to repeat recipes (especially if they’re “new”) with slight changes so will do some ‘xperimenting to see what differences occur.
 
Top