Appropriate boilage to avoid DMS spoilage

[natefitz]

I was a little confused by the 30min boil called for in my AHS Wit kit.
After perusing the forums it seems that short boils are ok for a low-hop brew, however I have also read that any recipe with pils should boil for up to 90 min due to dms. This recipe is 46% belgian pils (see bellow).

Can anyone give me the straight dope on boiling time and dms with different grains?
Thanks

Ingredients

Amount Item Type % or IBU
4.75 lb Pilsner (2 Row) Bel (2.0 SRM) Grain 46.34 %
3.00 lb White Wheat Malt (2.4 SRM) Grain 29.27 %
2.50 lb Wheat, Flaked (1.6 SRM) Grain 24.39 %
0.50 oz Amarillo Gold [8.50 %] (30 min) Hops 11.4 IBU
0.50 oz Amarillo Gold [8.50 %] (5 min) Hops 3.0 IBU
0.50 oz Coriander Seed (Boil 5.0 min) Misc
0.50 oz Orange Peel, Bitter (Boil 5.0 min) Misc
2.00 items Zest of One Orange (Boil 1.0 min) Misc
1 Pkgs Belgian Witbier (Wyeast Labs #3944) Yeast-Wheat

 

[PNWgirl]

I think that Pilsner malts and anything with corn will cause more DMS, so a longer boil will help get rid of that. Personally I would go longer than 30 minutes with 46% Pilsner. Longer boil times also help clarify your beer as it coagulates proteins.

 

[jayhoz]

I just did a 90% pilsner malt brew and boiled for 75 mins. Am I screwed? Have I made vegetable beer?

I don't know how I missed the need for longer boils for Pilsner malt?

 

[BierMuncher]

As quoted from Palmer's "How to Brew"

Like diacetyl in ales, DMS is common in many light lagers and is considered to be part of the character. DMS is produced in the wort during the boil by the reduction of another compound, S-methyl-methionine (SMM), which is itself produced during malting. When a malt is roasted or toasted, the SMM is reduced beforehand and does not manifest as DMS in the wort, which explains why it is more prevalent in pale lagers. In other styles, DMS is a common off-flavor, and can be caused by poor brewing practices or bacterial infections.

DMS is continuously produced in the wort while it is hot and is usually removed by vaporization during the boil. If the wort is cooled slowly these compounds will not be removed from the wort and will dissolve back in. Thus it is important to not completely cover the brewpot during the boil or allow condensate to drip back into the pot from the lid. The wort should also be cooled quickly after the boil, either by immersing in an ice bath or using a wort chiller.

When caused by bacterial infection, DMS has a more rancid character, more liked cooked cabbage than corn. It is usually the result of poor sanitation. Repitching the yeast from an infected batch of beer will perpetuate the problem.

Four rules of thumb for preventing DMS (in order of importance in my opinion)

1) Never cover a boiling (or hot) kettle.
2) Get a good rolling boil to help evaporate DMS.
3) Boil less kilned malts (like pilsner) for 90 minutes.
4) Cool the wort to below 140 degrees as quickly as possible to stop DMS production.

 

[ChrisKennedy]

It isn't the modification of the malt, it is the kilning that makes pilsner prone to DMS in the final beer.