Time needed for Starch and Sugar Conversion in the Mash

[mabrungard]

I was poking around on the net, doing some research on another subject. I found an interesting journal article that helps illustrate the relatively short amount of time we need for a mash conversion to occur. I had heard some brewers using conversion rests as short as 15 minutes, but this paper seems to point to a slightly longer rest of around 30 minutes to produce a high degree of starch AND SUGAR conversion. The paper below presents a couple of graphs that illustrate the conversion over time.

http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.1982.tb04104.x/pdf

Look at Figures 3 and 5 to follow the story. In both figures, the starch is generally depicted with the line with the open circles. In Fig 3, you can see that starch content drops to zero after only a few minutes at 70C (158F). But Fig 5 shows it takes much longer at 45C (113F) and it only goes so far (probably due to gelatinization). The other lines on those figures are the sugars being created or converted. The lower the molecular weight (Mw), the smaller (and more fermentable) the sugar. In Fig 3, you can see the ultimate rise in the low Mw sugars (line with the open triangles) and the long time it takes to get there. Fig 3 shows that the low Mw sugar content was still rising at 25 minutes.

Ultimately, these figures show that you can control the degree of fermentability and the presence of high molecular weight sugars with the duration and the temperature of your mash. It does appear that an hour-long rest at high temp should be sufficient and you might get away with as little as a half-hour. Just remember that Fig 3 is at 158F and if you are mashing at a little lower temp, the conversion rate will be slower.

Enjoy!

 

[pjj2ba]

This is a major reason I like to do step mashes. I can tweak the fermentability even more

 

[MindenMan]

I usually mash for 90 minutes,just because I have always done it that way. Yesterday, I decide to iodine test my wort at 60 minutes, and no color change. From now on I will start checking at earlier points in time, I am pretty sure it can't hurt. I brewed a Strong Scottish Ale, and planned to brew 4 gallons, as mashing over 12 pounds of grain is a pain. No, I don't have an insulated tun. I sparged to 8 gallons, and had an O.G. of 1.040, meaning 4 gallons should post boil to 1.080. I now realize my 40 quart pot is too small to do 5 gallons of big beers correctly.

 

[biertourist]

The time required depends upon the total diastatic power of the mash; I did a historical 1850 porter recipe that had a DP of 33 Lintner and it didn't pass the iodine test after 90 minutes.

The common advice says that 30 Lintner is the bare minimum required to complete conversion in 1 hour, but I find 40 Lintner reuquired in an actual mash to be the bare minimum.

Calculating the total mash DP is relatively easy, just pull the malt report for each individual malt then take the DP in deg Lintner times the % that that malt represents of the grist; do this for each malt and then add the numbers together.

You can find that if you're using low DP Munich malt or even some floor malted Marris Otter as your base malt in a modern American home brew recipe that involves a larger percentage of speciality malts that you can get some pretty low DP number that would justify longer mash times.

BUT if you're using North American 2 row as your basemalt you'll often find the opposite especially in a recipe with little speciality malts -you might complete conversion in 30 minutes. -I've found that recirculation mashing accelerates the rate of conversion, too.

The iodine test is the best way to gauge conversion progress; blueish blackish == starch / amylopectin, deep red == long-chain sugars (but starch conversion complete), iodine color == mid or mid and low molecular weight sugars.

Without the diastatic power of the malt listed in the linked-to study, I have no idea how you're supposed to translate the lab results to something practical. It's nice that they listed the (rare?) barley variety but how was the barley malted? -Was it treated as a lager malt or a pale malt? -Even this would only give you an INDICATOR of the diastatic power. IMO, you can't really get to practical advice without the discussion of mash diastatic power AND time and temp and technique all considered together. (Mash DP in a single temp infusion mash at 65C and conversion results over time is a great starting point to get to practical advice.)


Adam

 

[Hoser_brewing]

Here's another paper from the same journal that shows fermentability as a function of mash time, mash temp (145 vs 150F), diastatic potential, and more.

So yeah. Take a read. Enjoy. The journal's got a crapton of great stuff. They just had their 125th anniversary and did a fantastic series of review papers. All of them are worth a read.

 

[Tiber_Brew]

Here's another paper from the same journal that shows fermentability as a function of mash time, mash temp (145 vs 150F), diastatic potential, and more.

So yeah. Take a read. Enjoy. The journal's got a crapton of great stuff. They just had their 125th anniversary and did a fantastic series of review papers. All of them are worth a read.

Would love to read, but I'm verboten, getting a "403 Forbidden" error. What is the access to that journal article?

 

[suregork]

Would love to read, but I'm verboten, getting a "403 Forbidden" error. What is the access to that journal article?

http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.1961.tb01772.x/abstract

Here are the 125th Anniversary Reviews:
http://onlinelibrary.wiley.com/jour...e/125th_anniversary_reviews_virtual_issue.htm

 

[Tiber_Brew]

Thanks!

 

[smakudwn]

Can someone explain the "concentration of the mash" percent to me? I feel like I should know this but I just can't think of it.

 

[Milan37]

I'm curious about that, too. They show it in Table II as "wt grist as % vol mash liquor." But I'd like to understand it more, too.

 

[Owly055]

The story is NOT a simple one....... Your crush and your temp are the critical elements. I am now drinking a beer that was mashed for a total of about 10 minutes as I calculate it. Again it is not a simple calculation because I heated it from 130F tap water, taking 10 minutes (approx) from 145-155, and had 100% conversion from my tests. It was crushed with a .010 roller spacing. Attenuation was slightly low as expected, but actually better than expected. My final ABV was about 3/4 of one percent below what I would have had with my typical hour long mash. It never left the stove top. My next mash which was "splash cooled" from 155-145 after complete conversion, and spent another 10 minutes climbing back to 155, had excellent (normal) attenuation.

My conclusion from real world brewing is that half an hour is easily enough mash time..... depending on crush. Crush is the key. The penalty if it could be called that for ultra fine crush is a bit more trub.....not a lot, but more. I've been experimenting with mash times from 10 minutes upwards to as long as 2 hours, and so far I see no advantage in extended mash times unless you are using local homebrew store crush. When the conversion is done........ it's basically done. For a dry beer relying heavily on Beta Amylase, a longer lower temp mash is desirable........ or is said to be. My only gauge is attenuation, and I don't see it.

H.W.

 

[helibrewer]

The story is NOT a simple one....... Your crush and your temp are the critical elements. I am now drinking a beer that was mashed for a total of about 10 minutes as I calculate it. Again it is not a simple calculation because I heated it from 130F tap water, taking 10 minutes (approx) from 145-155, and had 100% conversion from my tests. It was crushed with a .010 roller spacing. Attenuation was slightly low as expected, but actually better than expected. My final ABV was about 3/4 of one percent below what I would have had with my typical hour long mash. It never left the stove top. My next mash which was "splash cooled" from 155-145 after complete conversion, and spent another 10 minutes climbing back to 155, had excellent (normal) attenuation.

My conclusion from real world brewing is that half an hour is easily enough mash time..... depending on crush. Crush is the key. The penalty if it could be called that for ultra fine crush is a bit more trub.....not a lot, but more. I've been experimenting with mash times from 10 minutes upwards to as long as 2 hours, and so far I see no advantage in extended mash times unless you are using local homebrew store crush. When the conversion is done........ it's basically done. For a dry beer relying heavily on Beta Amylase, a longer lower temp mash is desirable........ or is said to be. My only gauge is attenuation, and I don't see it.

H.W.

Good points. I mash until I get a refractometer reading in accordance with this chart. Sometimes it's 30 min, sometimes a full hour but my crush is .036 on a 2-roll because I want the lautering cushion:

 

[ajdelange]

I'm curious about that, too. They show it in Table II as "wt grist as % vol mash liquor." But I'd like to understand it more, too.

Haven't read the papers but taking this at face value it means just what it says. If you mash 1 kg of grain with 2 L of water you would have 1 kg/ 2L or 50% w/v. Seemingly, at first, a strange way to do it but as a liter of water weighs a kg per liter (approximately) that example would be pretty darn close to 50% w/w.

 

[smakudwn]

Thank you AJ. I was thinking along the same lines but in my head I was useing pounds of grain to gallons of watter in the mash. Makes sense how you describe it. So if a 10lb grain bill @1.5qts per pound of grain would get me a mash concentration of about 70% right?

 

[ajdelange]

Converting everything to metric: 10 lbs is 4.54 kg and 10*1.5 = 15 qts. (15*3.785/4) = 14.19 L. 4.54/14.19 = 32%

 

[Owly055]

I've experimented with mash times from 10 minutes up to 2 hours. What becomes immediately obvious is that there are two factors.......... conversion and attenuation. Conversion can happen in as little as 5 minutes with a fine crush as borne out by iodine tests and refractometer tests. To achieve extremely rapid conversion, you need fine crush, and a relatively high temp...152-155 or so. lower temp mashes take longer to convert. Lower temp mashes yield higher attenuation due to the Beta Amylase having more time to work, but the difference isn't huge.

My radical 10 minute mash experiment involved a dough in at 135, and steady heating up to 145 on high heat, then reduced heat at about 1 deg per min from 145 to 155, then heating on up to a boil. It yielded a slightly sweet, but excellent brew that fell less than one percent below expected ABV (about 3/4 of a percent). There was no other downside. The slight additional sweetness was an asset, and the beer had been hopped to take advantage of that.

I've had good results duplicating that program, and doing a "splash down" to 145 with cold water, and doing a 1 deg per min heat back to 150, holding there for an additional 5 minutes, then cranking the heat and running right up to boil. I get full conversion and "normal" attenuation doing this. The actual "mash time", I consider to be the time I dwell between 145 and 155, or about 20 minutes total, or 22 if you count the time taken to reach 155 from 150 at high heat.

There is no observable downside other than the fact that using my ultra fine crush, I end up with slightly more trub. (double crush with .010 spacing for the second crush). In a 2.5 gallon brew, I lose about half a bottle. (1/2L).

I've concluded that the hour mash and wrapping my kettle, trying to maintain temp is just a waste of time. I now mash on the stove top.......... Half an hour of stirring and monitoring the temp, then right on up to boil. This cuts my brew day down to about 2 hours. It's worth half a bottle of beer, and half an hour of steady attention!!

 

[Owly055]

I do BIAB....... so fine crush isn't an issue. The theory that a full volume mash is less efficient than a conventional mash due to the density of the enzymes has been completely debunked. I was going to build a mash tun and do a conventional mash and sparge originally, but abandoned that thought after doing BIAB and hitting excellent efficiencies of as much as 90%. There may be flavor benefits to the longer steeping times......but I don't see it. I just see more time and work with mash and sparge.


H.W.

Good points. I mash until I get a refractometer reading in accordance with this chart. Sometimes it's 30 min, sometimes a full hour but my crush is .036 on a 2-roll because I want the lautering cushion:

 

[biertourist]

Good points. I mash until I get a refractometer reading in accordance with this chart. Sometimes it's 30 min, sometimes a full hour but my crush is .036 on a 2-roll because I want the lautering cushion:

Wow; my head just exploded with the awesomeness of this post!

I really like this method... even more than the iodine method, actually...

Do you have to filter your wort through a paper towel or coffee filter to get an accurate reading?


Adam

 

[Milan37]

Haven't read the papers but taking this at face value it means just what it says. If you mash 1 kg of grain with 2 L of water you would have 1 kg/ 2L or 50% w/v. Seemingly, at first, a strange way to do it but as a liter of water weighs a kg per liter (approximately) that example would be pretty darn close to 50% w/w.

Thank you. So that means my 12.25# (5.5kg) grain bill, mashed BIAB in 7.5 gallons (28.4L) of water comes out at 19%.

For a high diastatic power malt at this concentration, both 145 and 150 for an hour showed well over 90% efficiency and over 80% fermentability (it looks like almost no difference in fermentability between the two). I looked up Rahr and Briess 2-row and Rahr is listed at 130 and Briess at 140 (the DP 130 malt in the study was described as 'exceptionally high').

 

[helibrewer]

Wow; my head just exploded with the awesomeness of this post!

I really like this method... even more than the iodine method, actually...

Do you have to filter your wort through a paper towel or coffee filter to get an accurate reading?


Adam

No filtering required, I just pull a little sample off the RIMs return into the MLT and take a reading. Iodine is good for verifying that the amylose is fully broken down. It is much harder to determine that the amylopectins have been broken down using just iodine.

 

[smakudwn]

Converting everything to metric: 10 lbs is 4.54 kg and 10*1.5 = 15 qts. (15*3.785/4) = 14.19 L. 4.54/14.19 = 32%

Thank you AJ

 

[MikeInMKE]

Good points. I mash until I get a refractometer reading in accordance with this chart. Sometimes it's 30 min, sometimes a full hour but my crush is .036 on a 2-roll because I want the lautering cushion:

On which page of Braukaiser's site did you find this chart? I'd like to read his research behind it, and quite likely bookmark the page for future brews.

Thank you.

 

[MikeInMKE]

Never mind, found it.

"Table 1 gives the expected first wort extract/gravity based on the mash thickness at the time that the sample is pulled. To simplify the calculations this table assumes an 80% potential extract content in the grist (which is typical for most base malts) and 100% mash efficiency. Use these numbers as a benchmark for comparing your measured first wort gravities." Emphasis mine.

 

[Owly055]

Here is an example of how this chart would apply to my inline mash. I typically mash with about 3.75 gallons of water for 5.5 pounds of grain. That's 15 quarts for 5.5 pounds of grain or 2.73 quarts per pound using a full volume BIAB process. If I hit 1.048 or a touch more at the end of mash, I've hit the conversion target. I read brix not gravity at this point, but that's hardly relevant. That is almost exactly the reading I am seeing when conversion ends. With my speed brew mash........ the 10 minute mash, I hit these numbers almost dead on in a bit under 10 minutes.

This of course doesn't address fermentability. It's easy to achieve full conversion, but we have no way to measure fermentability until we are done fermenting. We are shooting in the dark here. Do we continue the mash for a full hour? Another 10 minutes, 20, 30???

The only way we can control fermentability is by very tight process control. The easy way of course is by using crystal so we have a known amount of unfermentable sugars, and mashing for a long time at a lower temp as if we were otherwise shooting for a very dry beer.

Fortunately....... for me, it isn't all that critical. If I mash for an hour or two, I get exactly the same attenuation as if I mash for 20 minutes with a fine crush (in line). That leaves me with crystal malts and things like CaraPils to achieve the body, head, and sweetness I'm shooting for. I watch the refractometer, watch the clarity of the wort, and if I feel like it I do an iodine test........ I know when I hit 100% conversion. The wort is clear, and the refractometer reading has stopped rising. At this point, I "splash down" to the mid 140's with cold water, and hold it there awhile, the slowly bring the temp back up to mashout temps.

We are fortunate to have the tools and quality consistent ingredients we do. We can achieve reasonable repeatability with little effort.

H.W.

 

[pricelessbrewing]

Thanks for the linka brun, haven't had a chance to read yet. Did they happen to state their crush size or mill gap?

 

[helibrewer]

This of course doesn't address fermentability. It's easy to achieve full conversion, but we have no way to measure fermentability until we are done fermenting. We are shooting in the dark here. Do we continue the mash for a full hour? Another 10 minutes, 20, 30???

The only way we can control fermentability is by very tight process control. The easy way of course is by using crystal so we have a known amount of unfermentable sugars, and mashing for a long time at a lower temp as if we were otherwise shooting for a very dry beer.


H.W.

IMHO if you have reached full conversion (100% extract potential) you are done as far as the mash impact on fermentablility goes. The grain bill will determine the variables of color, body, residual sweetness. Attenuation is layered on top of the fermentablility based on all the factors that effect yeast performance but I tend to think of fermentablility as extract potential and nothing more (from a mashing perspective).