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09-29-2011, 07:17 PM   #11
dm2bfree
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Quote:
 Originally Posted by Bob While true, this is an over-simplification. I can expand on this if you want, OP. Bob
I'll ask, would you mind expanding The more the better for me, I'm trying to learn everything I can!

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09-29-2011, 08:40 PM   #12
Bob
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Okay, here it is in semi-technical brewer-speak.

There are a variety of points during the brewing cycle that gravities are taken. Usually homebrewers only worry about two: OG and FG. There are more, and they tie in with how and why things happen the way they do in the brewing process.

There are "kettle gravities", which allow us to observe - and therefore tweak if we need to - what's going on in kettle. The pre-boil gravity helps us to predict if we're going to hit our post-boil gravity. Kettle gravity determines hops alpha-acid utilization, or the degree to which the alpha acids isomerize into solution in the wort.

It is a rule of thumb that the lower the kettle gravity, the better the utilization, though there is a lower limit to that rule. It appears that below a certain gravity utilization starts to drop off, indicating that the hops seem to want a certain amount of malt in solution. No one knows exactly why.

Here's a practical example:

Let's imagine a 5 gallons (US) batch of homebrew with a desired of OG 1.048 (12°P). We want that beer to have IBU of ~30.*

When you boil the entire volume of wort, plus an amount to account for losses during the boil, the IBU calculation does not change. Many homebrewers practice a smaller boil volume than the entire brew length, however, say 3 gallons for a 5 gallon batch. If you put all your extract in at the beginning, that can present utilization problems, because the kettle gravity will change if you keep the same amount of fermentables and reduce the volume.

In our example, I'm using 6 lbs of dry malt extract plus some specialty grain. If I add all my extract to a 3-gallon boil, my kettle gravity is 1.095 and the IBU imparted at the end of the boil will be ~19. If I keep 3 lbs of DME back to add late, my kettle gravity is reduced to 1.052 and the IBU will be ~30, right where I want it.

Here's a halfway decent visual reference:

As you can see, the Utilization % is influenced by two factors: Kettle gravity and time in boil. The higher the kettle gravity (represented by the numbers on the right of the chart marking lines), the lower the utilization %, and therefore the less bitterness gets in your wort.

Make sense?

Cheers,

Bob

* IBU prediction, even with an immense weight of brewing science behind it, is not a foolproof, absolutely accurate process. But since neither you nor I can taste the difference between 30 and 34 IBU, practically speaking it doesn't matter much.

09-29-2011, 09:05 PM   #13
hector
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Quote:
 Originally Posted by unionrdr Then,before I turn off the burner,I add the remaining DME & stir to fully incorporate. Then take it off the heat to add the LME,stiring till no more can be scraped off the bottom. Then chill before topping off in the fermenter. The quicker it chills down to pitch temp,the better. Less chill haze later...
Have you ever had DMS problem with this method ?!

Hector
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09-29-2011, 09:20 PM   #14
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Why would he? Every extract manufacturer of which I am aware has a procedure specifically designed to remove DMS precursors as part of the extract manufacturing process.

DMS is not something extract brewers need worry about.

Bob

09-29-2011, 09:35 PM   #15
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Quote:
 Originally Posted by Bob DMS is not something extract brewers need worry about.
As far as I know , Extract is commercially made by boiling the Wort , but in lower pressures which leads to lower boiling points . Therefore , there are still some precursors , due to their half lives which should be boiled off .

John Palmer said once in a Podcast that a 60-minute-boil is enough for extract batches ( comparing with 90 minutes for AG ) .

Hector
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09-29-2011, 09:59 PM   #16
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Okay, you're right, there are DMS precursors. Happy now?

The point is, the vanishingly small amount of DMS precursors is nothing to worry about.

A 60-minute boil is sufficient for AG batches of flavorful beer, too; homebrewers prove that thousands of gallons worth per day.

DMS is one of those bugbears that, like hot-side aeration, homebrewers only need to worry much about if they use a large proportion of Pils malt in an all-grain beer with low hopping rates, few specialty grains and a yeast with a transparent flavor profile.

In terms of possible DMS precursors, adding extract late isn't going to cause any issues whatever.

Practically speaking, if you're brewing an all-grain Pils or American Lager, keep up a vigorous, rolling boil for 90 minutes. If you're not, don't worry about it. Simple as that.

I really wish people would stop idly tossing around less-than-accurate information.

Bob

09-30-2011, 03:36 PM   #17
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I've never had DMS issues with my process,for the reasons already stated. Not even in light pale ales. The fact that I used late additions for the remaining DME, & all the LME isn't going to automatically cause DMS to rear it's ugly head. I also forgot to mention that I leave it to steep with a lid on for 15mins or so after the late additions are stirred in. OH,THE HORROR!!! No,didn't get anything off from that either. I also use o2 barrier caps,They work so well,I'm sold on them. They def seem to keep the beer fit to drink after long periods. Moreso then the regular caps did in this regard.
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09-30-2011, 06:26 PM   #18
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Quote:
 Originally Posted by Bob Okay, here it is in semi-technical brewer-speak. There are a variety of points during the brewing cycle that gravities are taken. Usually homebrewers only worry about two: OG and FG. There are more, and they tie in with how and why things happen the way they do in the brewing process. There are "kettle gravities", which allow us to observe - and therefore tweak if we need to - what's going on in kettle. The pre-boil gravity helps us to predict if we're going to hit our post-boil gravity. Kettle gravity determines hops alpha-acid utilization, or the degree to which the alpha acids isomerize into solution in the wort. It is a rule of thumb that the lower the kettle gravity, the better the utilization, though there is a lower limit to that rule. It appears that below a certain gravity utilization starts to drop off, indicating that the hops seem to want a certain amount of malt in solution. No one knows exactly why. Here's a practical example: Let's imagine a 5 gallons (US) batch of homebrew with a desired of OG 1.048 (12°P). We want that beer to have IBU of ~30.* When you boil the entire volume of wort, plus an amount to account for losses during the boil, the IBU calculation does not change. Many homebrewers practice a smaller boil volume than the entire brew length, however, say 3 gallons for a 5 gallon batch. If you put all your extract in at the beginning, that can present utilization problems, because the kettle gravity will change if you keep the same amount of fermentables and reduce the volume. In our example, I'm using 6 lbs of dry malt extract plus some specialty grain. If I add all my extract to a 3-gallon boil, my kettle gravity is 1.095 and the IBU imparted at the end of the boil will be ~19. If I keep 3 lbs of DME back to add late, my kettle gravity is reduced to 1.052 and the IBU will be ~30, right where I want it. Here's a halfway decent visual reference: As you can see, the Utilization % is influenced by two factors: Kettle gravity and time in boil. The higher the kettle gravity (represented by the numbers on the right of the chart marking lines), the lower the utilization %, and therefore the less bitterness gets in your wort. Make sense? Cheers, Bob * IBU prediction, even with an immense weight of brewing science behind it, is not a foolproof, absolutely accurate process. But since neither you nor I can taste the difference between 30 and 34 IBU, practically speaking it doesn't matter much.
That makes a lot of sense! Thank you!
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09-30-2011, 08:24 PM   #19
hector
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Quote:
 Originally Posted by unionrdr I also forgot to mention that I leave it to steep with a lid on for 15mins or so after the late additions are stirred in.
Does it mean that you turn off the heat after adding the malt and let it simmer for 15 minutes ?!

Hector
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09-30-2011, 09:14 PM   #20
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Quote:
 Originally Posted by Bob If you add before the end of the boil time, you run into a Catch-22: in order to safely add LME and prevent scorching, you must switch off the heat. When you do that, the boil stops. Which means your 60-minute hops addition just became 45 minutes (or whatever), which screws up your IBU calculations. It's a PITA to add late.
I think you are over thinking it. Even if you turn off the heat to get the LME/DME into solution you ramp it back up to a boil for at least another 15 minutes. If anything, you might extract a bit more bitterness from the hops than if you did a 60 minute continuous boil and as you already mentioned you can't detect a difference of fewer than 5 IBUs or so... pretty much a non issue IMO.

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