Author Topic: For those that measure mash gravity  (Read 2363 times)

Offline nyakavt

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For those that measure mash gravity
« on: March 02, 2010, 07:19:59 AM »
Do you find that a mashout is necessary to ensure 100% conversion?  I have been measuring mash gravity for the past 20 batches, but it has only been accurate for the last 7 or so since I started cooling samples in a sealed container.  I have thus far found that every beer but one required raising the mash temperature at the end (sort of a mashout, but it varies from 158-170F depending on how much water is in the tun) to ensure complete conversion.  After a 60 minute sacc rest I am several Plato low, I think 2-5 but I'd have to check my notes to be sure.

These results are confusing since I have heard a lot of people saying that a low adjunct mash is converted 'as soon as it hits the water'.  There may be some starches that are not gelatinized at the mash temperatures I am using, but I'd like some independent confirmation of this from other brewer's observations.

Some details:
Grist has been mostly Best Pils or Best Munich, with a 2-row and wheat base beer thrown in
Mill gap: .025" set by feeler gauges on the Barley Crusher
Grist is conditioned prior to milling with 1-2% water by mass
Mash temp has been 151-154 over the 7 beer span, losing 1-3° in the hour
Strike water volume is accurate to the nearest quart
Grist is measured on a scale accurate to the nearest 0.1 oz
Temperature is measured with the pro-accurate digital thermometer from NB, 32.0F in icy water and 213-214F at boiling (for wort).
Sample is gathered either into a 20 mL screw top test tube and immediately sealed, or in a 10 mL medical syringe. 
The test tube is cooled by submerging in a water bath, and the syringe is cooled by running cold water over the outside.  I tried submerging the syringe before but some water mixed with the sample and contaminated the reading.  Both methods agree exactly when taken on the same mash.
Sample size is typically 1-5 mL read on an ATC refractometer after cooling until it does not feel warm to the touch.
Grist potential OG is calculated from typical malt analysis sheets for base malts and values found in Home Brewing Wiki's Malts chart for each malt used.  Formula used: expected FW extract = 100 * grain laboratory extract / (R + grain laboratory extract) where R = water to grist ratio.

Offline Kaiser

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Re: For those that measure mash gravity
« Reply #1 on: March 02, 2010, 09:30:46 AM »
I haven’t brewed with a single infusion in a while since I haven’t brewed a Pale Ale in a while but your experience matches mine. Even pale malts like Pils don’t fully convert in just 10-15 min. Those conversion time numbers, that you find on data sheets, are often misinterpreted. They should be used to compare malts and not to determine how long your mash will take.

For a long time now my standard mash incorporates a long (30-45 min) rest at 160 F which usually gives me full conversion after it is done. I have yet to take the time to plot the mash gravity over time.

Crush is expected to have a strong impact on how fast the mash actually converts.

Kai

Offline kuphish

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Re: For those that measure mash gravity
« Reply #2 on: March 02, 2010, 09:37:20 AM »
For a long time now my standard mash incorporates a long (30-45 min) rest at 160 F which usually gives me full conversion after it is done. I have yet to take the time to plot the mash gravity over time.
Could you elaborate on your standard mash procedure, please?  I'm trying to maximize my conversion efficiency and right now I am stuck at around 92-93%.

Offline Kaiser

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Re: For those that measure mash gravity
« Reply #3 on: March 02, 2010, 09:49:17 AM »
For a long time now my standard mash incorporates a long (30-45 min) rest at 160 F which usually gives me full conversion after it is done. I have yet to take the time to plot the mash gravity over time.
Could you elaborate on your standard mash procedure, please?  I'm trying to maximize my conversion efficiency and right now I am stuck at around 92-93%.

My standard mash, which I use for most of my German beers goes like this:

- 63 C (145-146 F) held for 30 – 45 min. This is the maltose rest and its length controls attenuation
- Then heating while stirring
- 70-72 C (158-162 F) held for 30-45 min (sometimes even 60 min). This is the dextrinization rest and it needs to be held until the mash is iodine negative. That may happen after as little as 15-20 min but I’m holding it longer since some literature sources mention head retention and mouthfeel improvements for an extended rest at this temp. The few explanations that I found involve glycoprotedies which are releases into the wort but the enzymes that would be able to degrade them have already been denatured. I haven’t done any experiments regarding this effect yet.
- Then heating and stirring to mash-out at 75-76 C (167 – 169 F)

My malt is milled at about 0.7-0.8 mm (28 – 31 mil). I think my good conversion is helped by the fact that I do stir the mash, mash thin and hold that long rest at 160 F. But mashing with direct heat may not be a viable option for everybody since it does take a little more effort.

Kai

Offline kuphish

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Re: For those that measure mash gravity
« Reply #4 on: March 02, 2010, 10:21:40 AM »
For a long time now my standard mash incorporates a long (30-45 min) rest at 160 F which usually gives me full conversion after it is done. I have yet to take the time to plot the mash gravity over time.
Could you elaborate on your standard mash procedure, please?  I'm trying to maximize my conversion efficiency and right now I am stuck at around 92-93%.

My standard mash, which I use for most of my German beers goes like this:

- 63 C (145-146 F) held for 30 – 45 min. This is the maltose rest and its length controls attenuation
- Then heating while stirring
- 70-72 C (158-162 F) held for 30-45 min (sometimes even 60 min). This is the dextrinization rest and it needs to be held until the mash is iodine negative. That may happen after as little as 15-20 min but I’m holding it longer since some literature sources mention head retention and mouthfeel improvements for an extended rest at this temp. The few explanations that I found involve glycoprotedies which are releases into the wort but the enzymes that would be able to degrade them have already been denatured. I haven’t done any experiments regarding this effect yet.
- Then heating and stirring to mash-out at 75-76 C (167 – 169 F)

My malt is milled at about 0.7-0.8 mm (28 – 31 mil). I think my good conversion is helped by the fact that I do stir the mash, mash thin and hold that long rest at 160 F. But mashing with direct heat may not be a viable option for everybody since it does take a little more effort.

Kai


Interesting, I think I'll give that a try on my next batch.  I know the problem isn't my crush, so it's probably the lack of agitation during the (single infusion) mash and having a second rest at 160F.  Two questions: (1) What is your conversion efficiency with this procedure?  (2) Do you use a different mash schedule for non-German beer styles?

Offline a10t2

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Re: For those that measure mash gravity
« Reply #5 on: March 02, 2010, 10:52:06 AM »
Are you checking your mash pH? 2-5°P low seems like a lot to me, especially after 60 minutes. My mashes are always within about 1°P of the theoretical values.

Is your refractometer calibrated?
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Offline Kaiser

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Re: For those that measure mash gravity
« Reply #6 on: March 02, 2010, 11:11:26 AM »
(1) What is your conversion efficiency with this procedure?  (2) Do you use a different mash schedule for non-German beer styles?

I usually convert around 98-100% but at levels so close to the max it matters to use the actual grain potential from the malt analysis which I don't My calculations assume 80% extract potential and 4% moisture. The actual values are more like 82-83% extract potential which means that I'm overestimating my conversion efficiency. But I don't worry about that detail.

Kai

Offline nyakavt

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Re: For those that measure mash gravity
« Reply #7 on: March 02, 2010, 11:39:00 AM »
Are you checking your mash pH? 2-5°P low seems like a lot to me, especially after 60 minutes. My mashes are always within about 1°P of the theoretical values.

Is your refractometer calibrated?

pH is checked with colorpHast strips and I don't close up the tun until the pH is between 5.3 and 5.6 (5-5.3 on those strips) as measured on a sample that is not warm to the touch.  I measure right after stirring, maybe only a minute after making a salt adjustment.  Sometimes it comes in right at 5.3, other times it is too high or too low, but this is what I shoot for.  I have only checked the mash pH at the end of the rest a couple of times to see if I was getting an inaccurate reading early, the measurements both times have agreed with the early measurement.  Those strips really are borderline for being useful in the brewing range.

I agree it seems low, especially for the nearly 100% pils malt grist.  I'll have to check my notes when I get home to be sure, hopefully I wrote down the 'incomplete' conversion reading.

The refractometer is calibrated on brew day once with a drop of tap water.  I used to have to adjust it a lot when I first got it, but it rarely needs adjusting now.  I try to remember to check every time, but it's conceivable that I got lazy once or twice.

Offline nyakavt

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Re: For those that measure mash gravity
« Reply #8 on: March 02, 2010, 11:47:55 AM »
For a long time now my standard mash incorporates a long (30-45 min) rest at 160 F which usually gives me full conversion after it is done. I have yet to take the time to plot the mash gravity over time.

I know you said that you do not yet have a plot of mash gravity over time.  I have found that whenever I check the mash gravity after raising the temperature (min 5 max 10 min) it has gotten up to 100% conversion.  Do you have a similar observation, or does yours take quite a while longer?

Along a10t2's line of questioning, how close are you after the sacc rest?

Quote
My malt is milled at about 0.7-0.8 mm (28 – 31 mil). I think my good conversion is helped by the fact that I do stir the mash, mash thin and hold that long rest at 160 F. But mashing with direct heat may not be a viable option for everybody since it does take a little more effort.

Assuming that the measurements taken are accurate I am also getting 100% conversion.  The water to grist ratio I use is around 2 qts / lb, (1.5 for bigger beers).  I get up to 160F by boiling 2-4 qts of the mash and adding back to the cooler.  I don't want to call it a decoction because I am only raising the temperature, not heating long enough to get a lot of flavor development.

Offline Kaiser

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Re: For those that measure mash gravity
« Reply #9 on: March 02, 2010, 11:57:29 AM »
I know you said that you do not yet have a plot of mash gravity over time.  I have found that whenever I check the mash gravity after raising the temperature (min 5 max 10 min) it has gotten up to 100% conversion.  Do you have a similar observation, or does yours take quite a while longer?

I didn't check right after raising the temp since I didn't get a refractometer until recently.

Kai

Offline a10t2

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Re: For those that measure mash gravity
« Reply #10 on: March 02, 2010, 01:07:15 PM »
The refractometer is calibrated on brew day once with a drop of tap water.  I used to have to adjust it a lot when I first got it, but it rarely needs adjusting now.  I try to remember to check every time, but it's conceivable that I got lazy once or twice.

I was more concerned that it might have some sort of linear error. Have you checked a known-Brix solution?

FWIW my last three single-infusion mashes were at 89%, 95%, and 94% of the values from Kai's chart. For the 89% batch, I don't have a lot analysis, so it assumes 80% DBFG and may not be accurate. The other two were domestic 2-row and are relative to the actual potential extract.
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Offline nyakavt

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Re: For those that measure mash gravity
« Reply #11 on: March 03, 2010, 05:42:39 AM »
I was more concerned that it might have some sort of linear error. Have you checked a known-Brix solution?

FWIW my last three single-infusion mashes were at 89%, 95%, and 94% of the values from Kai's chart. For the 89% batch, I don't have a lot analysis, so it assumes 80% DBFG and may not be accurate. The other two were domestic 2-row and are relative to the actual potential extract.

I did this but probably about a year ago.  May be time to check it again.  FWIW, the values from the refractometer don't seem to be too far out from the hydrometer samples post boil, the refractometer reading / hydrometer reading (in plato) I think has been 1.01 - 1.04.

I looked through the notes and came up with the following (hopefully this shows up ok  :-\):

batch        targ G  G@60  % conv  Gmshout % conv  mash temp
oktoberfest   17.3   13.8     80   17.8     103    151
dortmunder    15.7   13.4     85   15.8     101    151
dunkel        15.4   14.6     95   16.4     106    154
German Pils   15.6   13.5     87   15.6     100    148
Citrarillo    19.5   14.8     76   20       103    153
Alt           18.7   19      102   19       102    151.5
Munich Weiss  20.3   14       69   19.5     96     151
Pliney        19.7   18.2     92   18.2     92     150
Janet's Brown 19.8   18.3     92   19.4     98     154


Some of the readings are higher than 100%, I attribute this to not having the real malt sheets.  The ones I have been going by for base grains list the yield as a minimum, so the individual bags could be higher.
« Last Edit: March 03, 2010, 05:44:23 AM by nyakavt »

Offline Kaiser

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Re: For those that measure mash gravity
« Reply #12 on: March 03, 2010, 06:35:06 AM »
Thanks for sharing this. In many cases the boost is quite substantial. I'll take some readings when I brew on Friday but it will be a while until I have an ale with a single infusion scheduled.

Kai

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Re: For those that measure mash gravity
« Reply #13 on: March 03, 2010, 05:52:36 PM »
The refractometer is calibrated on brew day once with a drop of tap water.  I used to have to adjust it a lot when I first got it, but it rarely needs adjusting now.  I try to remember to check every time, but it's conceivable that I got lazy once or twice.

I was more concerned that it might have some sort of linear error. Have you checked a known-Brix solution?

FWIW my last three single-infusion mashes were at 89%, 95%, and 94% of the values from Kai's chart. For the 89% batch, I don't have a lot analysis, so it assumes 80% DBFG and may not be accurate. The other two were domestic 2-row and are relative to the actual potential extract.

Edit: I should add that these are without a mashout.
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