[tygo]

How much is not much though?  After mashing at say 154F for 60 minutes how much b-amylase is left?  If it takes awhile to run off the wort into the kettle and the wort is sitting there at 140F for half an hour or so, isn't that beta going to continue to work?  It seems to me like it would.  I don't know how much impact having 10% of the original b-amylase running for 30 minutes in the wort would have, but it feels to me like it would have some impact.

Maybe I'm wrong but I'm having issues with my attenuation being a bit higher than I would like.  I'm going to try a mashout step to see if I can mitigate that.

[denny]

Seems like it would be a lot more controllable to just raise your mash temp.

[Kaiser]

Seems like it would be a lot more controllable to just raise your mash temp.

That's what I was going to suggest as well.

If the process consistent, I.e. the wort always sits for about the same time at about the same temp, rising the mash temp can also help with lowering the wort fermentability.

But you may also try a mash-out.

Kai

[tygo]

I'm going to do that as well but I want to try to minimize the amount of enzyme activity that's occurring in the kettle.

[Podo]

The only time I use a mash out is when I'm brewing a wheat or rye beer to let the wort flow a little better.  I've also done one a few times when I screwed up my water calculations  .  It would seem logical that a mash out would increase efficiency, because water can dissolve more sugar at higher temps, but if your sparge is higher temp than your mash, it seems like it should all even out.

[tomsawyer]

Is the increase in efficiency seen with a mashout due to stimulation of alpha amylase, or better gelatinization of suspended starch particles that were big enough to prevent complete solubilization/gelatinization?

The solubility of sucrose in water at 65C versus 20C is 50% greater (300g in 100ml versus 200g in 100 ml).  The sugar concentration in a batch sparge is typically 1/3 of what the mash conc was, so a decreased solubility still won't cause anything to drop out.  Plus the sugar is already dissolved and so you don't need the increased entropy from hot water to break the crystals down and dissolve them.

[Kaiser]

Is the increase in efficiency seen with a mashout due to stimulation of alpha amylase, or better gelatinization of suspended starch particles that were big enough to prevent complete

It might be a combination of both. And if you infuse water for the mash-out, the reduced mash thickness also helps.

Barley has large and small starch granules. The small ones make up about 10% of the starch but require a higher temp to gelatinize than the large granules. As you heat the mash you’ll keep releasing starch, albeit in decreasing quantities, which is why you have to make sure that you don’t heat the mash above 175 F. At that point you would denature the a-amylase and with it the mash’s ability to break down the released starch.

Kai

[CASK1]

What are everyones procedures for a mashout? I used to use a SS kettle as my mash tun, and could add direct heat to raise mash temp or do a mash out. I've since gone to an Igloo cooler mash tun, and only raise temp by addition of hot water. It seems a true mashout would require a large addition of boiling water, or does anyone do decoction-style mashouts? Any ideas are welcome!

[Kaiser]

I have gone from mashing in a cooler to direct heat mashing on the stove. Wrapping the pot in blankets or a sleeping bag holds the temp during rests.

Kai

[gordonstrong]

It's going to depend on your equipment.  I can direct fire my mash tun, so that's what I do (while recirculating, so as to keep the temperature gradient low).

When I used to use a cooler, I'd infuse boiling water.

I've done decoction style mashouts, taking the thin portion of the mash and boiling it, then infusing it back in.  That will definitely stop enzymatic activity since the enzymes will be in the thin portion and boiling will denature all of them.

All of them work.  What you pick is up to you; what works best on your system and what your goals are.

If you have room for the boiling water, I'd think that would be the easiest.  Don't worry about mash thickness.  You're done mashing.  Now your concern is whether the additional weight will have impact on your lautering.

[Kaiser]

Now your concern is whether the additional weight will have impact on your lautering.

Gordon, how would the additional water weight impact lautering? Is it because the increased water column causes a faster flow rate?

Kai

[gordonstrong]

Just a general concern that a lot of water sitting on top of your grain bed can compact it.  I wish it would cause a faster flow rate    I'm concerned about the flow rate going to zero.

It's not a problem for most beers, and it's something batch spargers deal with all the time.  But I'm thinking about my weizens and other beers where I don't have as much filter material as usual.

Just something to watch.  There are obviously ways to mitigate the problem.

[Kaiser]

Once all the grain is submerged and nothing is flowing yet, the column of water on top of it does not affect how much it is compressed. It could only have an effect if there are air pockets in the grain which would get compressed.

As the wort starts flowing there will be a pressure difference between the bottom and top of the grain bed and that pressure difference compacts the grain bed. This pressure difference depends on the porosity and depth of the grain bed and the flow rate. The latter is what you’ll have to adjust to prevent the mash from getting stuck.

Kai

[bonjour]

I fly sparge most of my beers.  I will go up to about 4 gallons above my grain bed on occasions with no ill effects

Sometimes  see that the grain bed is floating so I let it settle on to the false bottom  and initially I'll drain until the wort level goes just below/at the surface of the grain bed.  After that I add my sparge water usually at least 12 inches above the grain bed.  Never had a problem.

[mabrungard]

Um guys, it doesn't matter if there was a million feet of water column over the grain bed as long as there is no flow through the bed.  The net downward force on the grain bed is the same as if there was 1 inch of water of the grain bed.  Its when there is flow that the stress on the grain bed can go up some.

In this case, there is a concept called Effective Stress that applies here.  This is a primary concept to geotechnical engineering, which is what my first Masters degree is in.

As was alluded to by the comments, we know that the pressure applied by the water increases as we go deeper under the water surface.  But that water pressure doesn't just act on the top of the grain bed, it acts on each grain within the grain bed too.  So to simplify, consider a single grain that is small so that the water pressure at the top of the grain is roughly the same as at the bottom of the grain. 

Since water pressure always acts perpendicular to the surface to which it is applied and since there is equal upward facing surface area as downward facing surface area, the net effect is that the water force acting downward on a particle is the same as the water force acting upward on that particle when there is no flow. 

The force imposed by flow is another matter and the depth of the water column over the bed can have an effect.  As I mention above, the pressure on the top of the bed is roughly the same as on the bottom of the bed when there is no flow.  To cause flow, you have to have a pressure gradient across the bed.  For our tuns, we open a valve that is connected to the outside world where the water pressure is essentially zero.  If we open the valve a crack, we can keep the pressure at the bottom of the bed only a little lower than the pressure at the top.  But, if we open the valve all the way, we could get close to zero water pressure at the bottom of the bed.  This is where the depth of the water column over the bed plays a part. 

If I've got a million feet of water head over the grain bed and I make a mistake and open the valve too much, then I could be placing a 1,000,000' - 0' = 1,000,000 feet of head on the grain bed.  But if I only have a foot of water over the grain bed, then the worst I could do is apply 1' - 0' = 1 foot of head on the grain bed.   

So, its not really that putting a lot of water over your grain bed is bad.  Its that you could place a lot of stress on the grain bed if you open the outlet valve too much and draw off wort too fast.

So its not the water's fault, its the operator's fault. 

And regarding the issue with Batch spargers, they are draining all the wort from the bed.  Recall that I mentioned that the water pressure acts on all surfaces.  As we drain the bed, then a portion of the bed is above the liquid surface and instead being partially supported by the water pressure, that grain is applying all its soggy weight to the rest of the bed.  That can certainly compress the bed and is a good reason why you should not perform batch sparging.  Don't drain the bed until the final runoff.