Step Infusions, L/g Ratios, The Universe And Everything

[bennyc]

Howdy brewers,

I'm thinking of upgrading my mash tun to a 36L cylindrical esky and have a few questions.

I'd like to be able to do step infusions (say, for example, 50C, 60C, 70C) by through boiling water additions. (I find doing stepped mashes in my kettle with my stove inaccurate, time consuming and a general pain in the backside...)

So, question 1: Is there any risk of tannin extraction from making boiling water additions? My reading suggests that there shouldn't be, but interested in views anyway.

Next, the water additions lead to the question of liquor/grist ratios and sparge volumes.

If I was to start with 2.5L/kg for, say, 6kg of grain, I would have 15L of water at 50C, then add around 4.5L boiling water to get to 60C, and then other 7.5L boiling water to get to 70C (rough calculations using Beer Alchemy). This would give me a total of 27L in the mash tun for a L/G ratio of 4.5/1. Because of the higher final L/G ratio, I would need less sparge water to get to my pre-boil volume (generally 32L).

So, question 2: as a fly sparger, do I run the risk of not being able to rinse as much sugar from the grains (i.e. lower efficiency)?

In an alternative scenario, I could mash in with a L/G ration of 1.5L/kg = 9L. Add 3L boiling water to get to 60C, and 5L boiling water to get to 70C = 17L total water, and a greater volume of sparge water needed to get to my pre-boil volume.

So, question 3: is there any issue in step mashing with infusing at low L/G ratios?

Long winded, I know, but I would be interested in your views!

Ben

 

[seemax]

1: added boiling water plenty of times, never noticed any tannins

2: potentially, never fly sparged so can't confirm either way, why not just batch sparge?

3: i've tried a really low ratios (due to small esky) and it struggles to mix properly, but 1.5 is fine

 

[bennyc]

This is part of the problem - with the final volume of water after all the additions, there's less room to maneuver with the amount of water to batch sparge with. Plus I've already got a fairly good fly sparge system going.

 

[Screwtop]

benny, seeing as your planning a protien rest first I don't see any problems with a low L/G ratio. The sacc rest is important so try to hit something around 2.75 - 3.25 L/Kg after your boiling water addition for the sacc rest, the same for the mash out rest, less important L/G ratio. I have found using some malts that attenuation tends to be lower due to some conversion occuring in the time it takes for the hot water infusion to reach equilibrium with the lower mash temp. You might be willing to accept this trade off in return for the benefits of being able to step mash.

Cheers,

Screwy

 

[bennyc]

Aha - thanks. So looks like I'll need to vary the starting L/G ratio depending on how many infusion steps and the desired temps so as to get the right sacc rest L/G ratio. And thanks for the tip on attenuation - not too worried about minor losses there, but good to know.

But that does lead me back to one of my earlier questions - is there any difference between (1) draining highly diluted mash (i.e. high final L/G ratio) into the kettle and then fly sparging with a small amount of water, and (2) draining less diluted mash (i.e. low final L/G ratio) and then fly sparging with a large amount of water? For some reason, I want to think that you'd get higher efficiency with (2), but then again, maybe there's more sugar initially in the water in (1) and you'd need less water to rinse the residual sugars.

Cheers

Ben

 

[Bribie G]

Slightly off topic... I'm trying to get my head around decoction mashing and, if I understand rightly, the idea is to actually take a portion of the grist, following the protein rest, and boil it then return to the tun. Now you would think that this would be Tannin Central. Presumably if the decoction guys don't have a problem then by stepping via boiling water you shouldn't have a problem either ?

On the sparging question I still remember from high school chemistry a concept called 'partition coefficients' that deals with the relative strengths of solutions at different stages of progressive dilution... for example it explains mathematically why it's more efficient to wash your bottle with a litre of water four times using 250 ml each time rather than twice using 500 ml each time. Sparging is basically just progressive washing and maybe some chemists on the forum might be able to run you through the figures.

 

[Screwtop]

Slightly off topic... I'm trying to get my head around decoction mashing and, if I understand rightly, the idea is to actually take a portion of the grist, following the protein rest, and boil it then return to the tun. Now you would think that this would be Tannin Central. Presumably if the decoction guys don't have a problem then by stepping via boiling water you shouldn't have a problem either ?

Plenty of info around re this Bribie, also for the thick pull grist is held at the mash temp for conversion before being boiled, thin pulls are used to achieve the same result as a hot water infusion step except no additional water is added.

Screwy

 

[bennyc]

There was an explanation on one of the episodes of Basic Brewing Radio about this.

Apparently it comes down to pH v temperature and volumes of water. The explanation was that at the end of sparging, most of the sugars and amino acids are gone, and so the liquid running off is only lightly buffered against changes in pH. As you sparge, the pH rises and once you get past 5.8, and the temp is above 78C, you start pulling out tannins. However, combined lower pH and higher temperatures won't pull out as many tannins. Also depends on volume of water you're mashing in - lower volumes of water and higher temperatures are okay because of the lower pH, whereas with higher volumes you need lower temperature again because of the pH. While you do get tannins from decoction, they are not so much as to be a concern.