leftover starch in grains, efficiency

Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum

Help Support Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.


Well-Known Member
Apr 8, 2008
Reaction score
I've never looked really closely at my spent grains (amazingly), but I did this last batch. I had little white blobs of what looked like oatmeal, just kind of mushy starchy stuff. It was starch-negative to iodine, along with the surrounding fluid, but if I smashed it up a bit, I got a heavy starch-positive test.

The batch was about 71% efficiency.

My thought is that I was losing starches this way. Perhaps it is inevitable, but do other people notice white blobs of starch left in the grains? I did a double decoction, and each boil liberated more starch, and that starch was broken down within a few minutes after returning to kettle, so the mash was then starch negative within minutes of each decoction return. Maybe I should go to a triple decoction!

Anyway, I also think the crush was a bit coarse. I purchase online, so the retailer has the mill, and I do not have one yet. I've asked them to check the mill and asked if I can request a double-crush. I have four more batches prepped from them, though, that all shipped together, so if it was a crush issue, I'm stuck with what I've got for now.

has anyone found any efficiency boosters or ways to get a consistent efficiency on their brew sculpture (three vessel single-teir herms with fly sparge and two pumps)? Any suggestions at all would be fun to discuss.
You might want to try Kaiser's Efficiency Spreadsheet. I just did it this past weekend (which also happened to be a decoction) and it was a learning experience. It will tell you where you're losing efficiency.

To measure the amount of sugars left in the spent grain I measured out 1 qt for each # of grain and put it in a pot, then dumped all the spent grain into the pot and stirred it very well...then dumped it back into the lauter tun and collected all the runnings. Those runnings measured 1.006...they were cloudy as hell but not much gravity. This is all part of that spreadsheet exercise.

has anyone found any efficiency boosters or ways to get a consistent efficiency on their brew sculpture (three vessel single-teir herms with fly sparge and two pumps)?
I would def look into getting your own barley crusher. My efficiency went way up after I got one and dialed in the crush.

I use the simplest of rigs; I mash in a regular pot and fly sparge using a Zapap lauter tun (i.e. bucket-in-a-bucket). I use a saucepot to ladle from one container to another until it's light enough to lift. Per that spreadsheet I got 99% conversion eff...90% efficiency into the kettle...and 88% into the fermenter. Ever since I tightened the gap on my Barley Crusher I've been getting 88% into the fermenter. My eff number has always been consistent...but only recently has it been high. Using LHBS crushed grains my eff was always @ ~75%. So you should be able to quickly get up to around 85% or better once you get a barley crusher and dial in the whole process. I think Pol gets really high efficiency using a rig similar to yours.

I also treat my water to achieve the correct residual alkalinity and mash pH for each brew. Dunno how much efficiency that buys me though.
I wish I could afford a mill right now, and I may have to make one my next purchase.

Did you notice large chunks of starch in your grain before you started milling your own? Do you notice leftover soggy bits of starch ever after your mash?
I'm not really sure. Below is a pic of the decoction grains vs. the mash grains right after the thick-mash decoction (right before the decoction was added back to the mash) a few brews ago. I'm not sure if this pic even helps. This was at the factory barley crusher setting. I was getting 83% into the fermenter at that time. Then I tightened the gap on my Barley Crusher just a little and it went up to 88% into the fermenter. I really think the crush was the last bit of efficiency that I could easily get.
I don't know if the white globs were starch for sure, but I know I saw some micropiles, some husk, and like in the left side of that picture above, white dots, even some left in the decocted mass, which for the most part had been boiled twice (I'm sure some is different).

But by taking a wet mash sample at mash-out with no starch, then mashing up those blobs, I got a starch-positive iodine test, so either those globs are starch, or somewhere in the smooshing up of those globs and some husk bits I'm releasing more starch.

Next brew I will separate JUST those white globs and mash them up and test them without any other husk material.

THey feel like little globs of oatmeal.