efficiency vs. conversion

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airving

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*** pseudo-science warning ***

So I see lot of posts about low efficiency and talk about testing for complete conversion, but that seems a bit odd to me. Chalk it up to too much thinking and not enough brewing.

Per Palmer's chart of enzyme activity temps and text thereabouts, the starches are soluble at 95 degrees reaching 90% solubility at 130. I imagine that if we were to mash at that temperature for a short time (or otherwise horribly miss our target temps in a normal mash), we'd have a wort full of starch, but I expect the gravity would be roughly the same as a good mash - it's a measure of solids disolved in the H2O, right? Starches are particles too! I could be totally off here though - please tell me if you know better.
Other reading indicates raising to mash out temps should free up a small % more starch.

So my question to those with more experience: Do you consider conversion and efficiency as two separate topics, or are they close enough to the same thing to lump together?

I also wonder what effect finings can have on final gravity - especially in a beer with starch haze, for example. Could use of finings be masking unfermentables (causing them to drop out thereby reducing the final gravity)?

I'd be intersted in gravity readings taken during the mash process - every 15 minutes or so. My expectation is that the readings would quickly reach a steady-state. I may have to test that next time around (although it would add a good bit of work).
 

david_42

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Two separate concepts. You can have good conversion and fail to rinse the sugars from the grain, resulting in low efficiency.
 

dallasd9

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Question: Is there any correlation between a high OG (1.076 vs 1.052) and efficiency?

All Grain Newbie
 

VikeMan

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Question: Is there any correlation between a high OG (1.076 vs 1.052) and efficiency?
Yes, all other things being equal (equipment/process/pre-boil volume), a batch with more grains will have a lower mash efficiency percent than a batch with less grains.
 

Holden Caulfield

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Question: Is there any correlation between a high OG (1.076 vs 1.052) and efficiency?
I would expect if you ran a regression against the two data points you would find zero to low correlation. Here is why...
  • Efficiency tells you how much of the available sugars in the grains you collected or will collect
  • Efficiency is a factor, along with the OG, that goes into the beer plan - combined they drive the the grain quantity
  • Efficiency is a constant for a brewers system
  • OG is a variable that changes dependent on a brewers intended beer
All that being said - efficiency doesn't change, only OG when building recipes, so no correlation.
 

VikeMan

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  • Efficiency is a constant for a brewers system
Eh? More grains --> lower mash efficiency. Unless you're willing to collect extra wort and boil it down.

Recipes with larger grain bills (but the same pre-boil volume) require more total water, because of more grain wort absorption. So the ratio of absorbed wort to total wort (including absorbed) is larger. Therefore a smaller percentage of the total sugars/dextrins produced makes it to the kettle.
 

McKnuckle

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In other words, the higher the theoretical maximum gravity attainable from a given grain bill and water volume, the less efficient a given process will be at achieving it.

Practically speaking for brew day, it means you factor in a lower mash efficiency as the gravity potential in a recipe goes up.
 

Holden Caulfield

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Eh? More grains --> lower mash efficiency. Unless you're willing to collect extra wort and boil it down.
Agree, I didn't want to get into all the subtleties.

Do brewers change their efficiency targets when brewing higher gravity beers, or do they change their boil rates to rinse the grains better - never really thought about it. Without changing boil rates, no/low sparge processes will definitively show correlation as the brewer will need to account for greater levels of sugars left behind.
 

VikeMan

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Do brewers change their efficiency targets when brewing higher gravity beers, or do they change their boil rates to rinse the grains better - never really thought about it. Without changing boil rates, no/low sparge processes will definitively show correlation as the brewer will need to account for greater levels of sugars left behind.
Given the same pre-boil wort volume, there's a relationship between grain bill size and mash efficiency for any type of sparge. Some just minimize the impact more than others.

ETA: I think @doug293cz has some nifty charts that show this.
 

VikeMan

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^That's one way to do it, i.e. plotting actual observations to get a curve.

You can also, given a brewing system's parameters, compute expected changes in mash efficiency resulting from changes in grain bill size and/or changing from no-sparge to batch sparge (or vice versa), starting with just a single (reliable) observation.
 

mashpaddled

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Two separate concepts. You can have good conversion and fail to rinse the sugars from the grain, resulting in low efficiency.
RIght--these are entirely different issues. Full conversion just means the available soluble starches became sugar. How much of the potential soluble starches you extracted from the grain and then how much of the sugar you extracted from the mash give you mash efficiency. The above discussion about mash density is an issue but you can also have poor solubility because your mash is full of grainballs where your well milled grain has not been mixed completely into the water and there is very little soluble starch extracted from those grainballs to convert.
 

dallasd9

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I would expect if you ran a regression against the two data points you would find zero to low correlation. Here is why...
  • Efficiency tells you how much of the available sugars in the grains you collected or will collect
  • Efficiency is a factor, along with the OG, that goes into the beer plan - combined they drive the the grain quantity
  • Efficiency is a constant for a brewers system
  • OG is a variable that changes dependent on a brewers intended beer
All that being said - efficiency doesn't change, only OG when building recipes, so no correlation.
Got it. Thanks
 

doug293cz

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Given the same pre-boil wort volume, there's a relationship between grain bill size and mash efficiency for any type of sparge. Some just minimize the impact more than others.

ETA: I think @doug293cz has some nifty charts that show this.
Here's the nifty chart:

Efficiency vs Grain to Pre-Boil Ratio for Various Sparge Counts.png


This is from a simulation based on a model described by Kai Troester. The model is pretty simple:
  • The wort has been fully homogenized prior to run off, so that there are no differences in extract concentration across the mash volume.
  • No additional conversion takes place after initial run-off begins.
The input parameters to the model are:
  • Total grain bill weight
  • Weighted grain potential (fine grain dry basis)
  • Grain moisture content
  • Desired post-boil volume (or pre-boil volume if boil time or rate is 0)
  • Boil-off rate
  • Boil time
  • Minimum water/grain ratio in mash (i.e. max mash thickness)
  • Expected apparent grain absorption rate
  • MLT undrainable volume
  • Number of batch sparge steps (0 - 3)
  • Expected conversion efficiency
Outputs are:
  • Pre-boil SG
  • Post-boil SG (i.e. OG)
  • Mash efficiency
  • Lauter efficiency
  • + a bunch of others
The default for the simulation is to force equal volumes for initial and all sparge run-offs. Strike and sparge volumes can be overridden manually if desired. Strike volume will be increased if necessary to limit max mash thickness, and sparge volumes decreased accordingly. The simulation also assumes that you have the same grain absorption rate for all run-offs.

You can find the simulation spreadsheet here. To use the sheet, download a copy and open with Excel or LibreOffice.

You can do some interesting things with the "Goal Seek" function of either Excel or LibreOffice:
  • Determine Grain Bill Weight needed to achieve a specific OG by using target post-boil OG as the goal, and the grain weight as the adjustable parameter.
  • Determine actual conversion efficiency by using actual OG as the goal and conversion efficiency as the adjustable parameter
  • Lots of other things depending on how creative you are.
It's not possible to do this kind of simulation for fly sparging in the general case since it is a dynamic process and batch sparging is a static process. However, limited data shows that a good fly sparge (i.e. no channeling) should follow a line about as much above the solid green line as the solid green line is above the solid purple line.

Brew on :mug:
 
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