An idea to possibly improve my lautering.

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An idea to possibly improve my lautering.

Postby billvelek » Fri Dec 05, 2008 3:39 pm

I have an equipment or technique idea that I will try during my next brew session, but thought I'd ask for some comments first -- and maybe someone has a better or easier way to fix the problem.

Ordinarily I don't have much trouble with my sparges ... (incidentally, I batch sparge, so fly sparging might be different) ... but with a few of my recipes where I use very finely powdered adjuncts like ordinary baking flour for my wheats or corn meal for my cream ales, I eventually approach a stuck sparge. My last four batches have been cream ales (which have turned out excellent, by the way), and so I have had to contend with the problem enough lately that I want to fix it. Drainage never actually stops completely, but it slows down to a flow rate that I am not happy with. I know that the first idea that probably pops into everyone's mind is to add rice hulls; I haven't tried that yet, but suspect that it might not work for the reasons I will explain.

I use a 10' long length of stainless steel mesh hose in a 48 quart rectangular ice chest -- no spigot. I just hook the drain hose on the handle during my mash, and then lower it into my kettle to drain, and it flows like there is no tomorrow. With grist consisting of just malted barley and specialty grain, and even some oatmeal, it doesn't skip a beat. My vorlauf consists of letting all of the wort drain into the kettle, which takes maybe five minutes or less, and then pouring it back on top of the grain bed, using a lightweight plastic plate I set on top of the grain to break the fall of the wort so that it doesn't disturb the grain bed. Works great -- very clear beer and no signs of hot side aeration. For those worried about HSA, you could drain into a bottling bucket, and then use a hose to drain the bucket back on top of the grain to minimize aeration, but I haven't needed to do that. Because of the rapid drainage of the tun, the grain bed no doubt compacts to a great degree -- but this has NOT been a problem in nearly all instances.

Now, in those batches (flour and/or cornmeal) where I have had a problem, the entire tun drains for my vorlauf without slowing down to any noticable degree; it is after I pour the wort back on top of the grain bed that the problem occurs, and it happens with both first runnings and my batch sparges (each one is vorlaufed). After about half of my wort is drained, it slows down to a slow trickle. Looking down into the tun, I see a layer of gray 'silt' (probably proteins and/or gluten) covering the entire top of my grain bed, with relatively clear wort -- maybe an inch or two -- sitting on top of it. It appears to me that the problem is not that my mesh hose is getting clogged, but rather that the gray layer on top of my grain bed is not allowing the wort to pass through it. I got to thinking that this might be why commercial breweries use 'knives' to 'cut' the top of the grain bed in their lauter tuns, so I used a spoon to scrape the gray substance aside, which definitely helped improve my flow rate. The grain bed was thick and compacted enough that my scraping didn't disturb the grain filter that had been established around my mesh hose, because the runnings didn't seem to cloud up to any degree, as far as I could tell.

Finally, I always do two batch sparges in which all the grain is stirred very well after sparge water is added; after I first do that, drainage is not impeded at all as I drain it for my new vorlauf -- but there is no significant layer of gray matter on top of the grain bed a that time, probably because it is distributed throughout the mash and everything is pretty loose from my stirring; it is when I pour the runnings back into the tun to complete the vorlauf and then begin to drain into my kettle that the problem arises again -- for each batch sparge.

The reason I suspect that rice hulls won't work is that I can't see how they will prevent the formation of that gray 'layer' on top of my bed.

My idea is this: before pouring the runnings back on top of the grain bed for vorlauf, I could cover the entire grain bed with a piece of thin cloth of some sort, with a string attached to each corner and anchored at the top of the tun. Then, when drainage slows down due to the settling of the gray matter on the top, I could either lift the cloth out completely, or pull it to one side of the tun to 'roll' the gray matter into one small area on top of the grain bed.

After I try this on my next batch, I'll post my results. If anyone has any other suggestions, I'm all ears.

Cheers.

Bill Velek
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Sludge

Postby chils » Sat Dec 06, 2008 10:14 am

I recently brewed a wit with 1lb. oats and flaked wheat & wheat malt and my 1st. runoff had this grey sludge on top of it.I just skimmed it off and kept lautering although I did add 1/2 bag of rice hulls just before my sparge.Does your sludge float on the wort before runoff?I didn't notice it on mine until after the runoff and then it was in my brewpot and easily dealt with.
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Oberteig

Postby slothrob » Sat Dec 06, 2008 10:56 am

Interesting idea, Bill. I think I'd try a paint strainer bag, but I wonder if it would be fine enough to catch the material. Let us know how your experiment works out.

That stuff is called the Oberteig and I remember seeing reference to it being the result of oxidation of proteins and tannins, so you spurred me to go and learn a bit more about it. It seems that it is probably a complex mix of fine particulates released from the grain, ß-glucans, and oxidized proteins.

When using a large proportion of unmalted grains or adjuncts like oatmeal, I like to use a ß-glucanase rest at ~100-110°F for 20 minutes to reduce these gums in the mash. It seems to help my flow rate on mashes with oats. It's a recommended rest for unmalted wheat, like your flour, as well.

Another possible help would be a protein rest on the high side of the range, like 130°F for 20 minutes, to break down the proteins that combine to form this silt without destroying too many of the peptides that contribute to head retention.

Or you could try a 118°F rest to cover ß-glucanase and proteinase. Especially if you believe that little proteinase activity remains after kilning malt.

From my experience with the gumminess of cereal mashes of corn meal, I'd think that one or both of these might benefit a mash high in corn meal, as well. While corn is a bit lower in protein, it's unconverted in corn meal.

Here's a couple interesting references:
Brewing Science and Practice by Briggs, and
a scientific paper studying the material in the Oberteig

Another thing you could try, which would be more unconventional, is cinnamon. 1 tsp of cinnamon in the mash is supposed to reduce hot side oxidation without adding any flavor to the finished beer. That may decrease the amount of Oberteig. I think I'll try that and see how it works out.
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