Is this a good idea or a bad idea?

[Bigelow92]

Hey guys,

I brewed one of my most requested beers last week, and this was the first time I'd attempted it all-grain. Its a very high grav beer, and I only recently upgraded my mash-tun but I've got the same old boil kettle. It uses like 15 lbs of German Pilsner, and I was told time and time again to always do a 90 minute boil when mashing with Pilsner malt to avoid DMS precursors, and this is what I have always done... (now I have absolutely no idea what these are, and the LHBS guy was unwilling to indulge my geekyness since it was kinda busy) ...so I have no clue what DMS is, why it has precursors, and why it might be something I want to avoid in my beer.

So, all that said, I'm lautering my mash... and I overshoot my pre-boil wort volume and have about 1.5 gal extra, and I mean like won't fit into my boil kettle. At this point I happilly get the bottle of scotch, but while drinkin my scotchie, I have a lightbulb moment. Now, bear with me:

-One of the reasons we brew all-grain is to retain that fresh bread,
fresh grain aroma and flavor, right?

-Now, I assume, like aromatic hop oils, the compounds responsible for
these fresh-beer flavors and smells are boiled off and escapes
with the steam.

So here I am, waiting for my 4.7 gal of wort to reach a boil, with another 1.5-2 gal of wort sitting in another pot with a ladle. I'm planning on topping off the post-boil, hopped wort with spring water... but what if... what if I were to do my main boil with all my bittering additions, and boil this second 1.5-2 gal of wort for only like 5-10 minutes, and add all my aroma-steeping to this, less-concentrated wort while the other finishes its boil? That would be both time-efficient and would lend alot of nice fresh-bread flavors and smells to my finished beer right?

I've only had a small taste when racking to secondary and it tastes almost the exact same as when I brew it partial mash, and it smelled divine, though its coming off a big, citra dry-hop so its hard to notice any grainyness under that blanket of cantaloupe and grapefruit.

But am I wrong here? When I mentioned my idea to a friend he said I was gunna have mad DMS in my beer, but when I probed, it turned out he had no idea what DMS was either... just that its a scary boogeyman. Anyone have any opinion one way or the other?

 

[Mb2658]

DMS comes across as a canned corn/cabbage flavor. Pilsner malt is more prone to DMS and most people do a 90 minute boil to ward off DMS. If you boiled the majority of your wort for 90 min and part of it for 10-15, you will most likely have more DMS precursors remaining in your finished wort than if you had boiled the entire lot for 90 min. I don't know what the exact time to get rid of DMS precursors is but suffice it to say, if it was 10-15 min, people wouldn't need to do a 90 min boil. Your beer might turn out just fine, time will tell.

As far as the reasons for doing all grain, me personally, I have only done all grain and do it because I like to have total control over the outcome of my wort. Some people prefer simplicity and others like to be more hands on. You can get a bready or malty beer from extract or partial mash.

 

[spark_plug]

This is a C&P from beersmith.

The half-life for DMS is 40 minutes, so half of the DMS will be boiled off in a 40 minute vigorous boil. So if we do the math, a 60 minute boil gets rid of 64.7% of the DMS and a 90 minute boil rids us of 79% of the DMS. That is why most experienced brewers recommend a 90 minute or longer vigorous boil.

Beers with robust flavor profiles (dark beers, strong ales, etc) tend to mask the DMS cooked corn flavor with other flavors such as roast, chocolate or caramel malts. Because of this, high DMS levels are most perceivable in lightly flavored beers such as low-adjunct pilsners, many German lagers, continental lagers and extremely light ales. DMS is rarely a problem in beers that are Amber colored or darker, and also rarely an issue with most robust beer styles.

 

[sptaylor70]

DMS = DiMethyl Sulfide.

 

[Bigelow92]

so after reading that wiki article, and digging a little further... the stuff thats actually in the wort after a short boil is dimethylsulfoniopropionate (DMSP), which then breaks down into DMS later... so this is not a yeast by-product and therefore cannot be cleaned up with lengthy conditioning. Damn. Is there anything I can do? It didn't the smell so far as I can tell from racking... then again, maybe it hasn't all broken down yet

I suppose I should wait till I pull the first pint before I go getting all wobbly in the knees. Though I'd like to do all I can to prevent any off flavors before I reach the point of no return.

 

[sptaylor70]

Actually, it can be cleaned up by yeast, at least to some extent (see, for example, the description of Wyeast 3638 Bavarian Wheat).

Condition a little longer and see what you get. Post your result.

 

[TNTgill]

Also you need a bigger pot if you are doing 5 gallon all grain batches. I would be afraid that you will dilute out your beer if you are topping off with water. That would solve all of your problems.

 

[Bigelow92]

Also you need a bigger pot if you are doing 5 gallon all grain batches. I would be afraid that you will dilute out your beer if you are topping off with water. That would solve all of your problems.

That is indeed the next step I need to take but it will take a little while to marshal the funds. I guess I'll just have to two full length boils simultaneously for now.

 

[RachmaelBenApplebaum]

I personally have at least one smaller pot for the extra runoff after I've achieved my initial boil volume. It's usually only a few quarts but hey, if I'm gonna be putting anything into my wort to increase the volume a bit, why waste the precious sugar?