[denny]

There have to be DMS precursors (SMM) in order for DMS to be formed.  Those are driven off when the extract is produced.

I've wondered about this.  When I make a starter with DME and boil it for 10 minutes on the stove, why do I get hot break?  I figured that would have been taken care at the maltster as well.

You get hot break because there's proteins there.

[redbeerman]

There have to be DMS precursors (SMM) in order for DMS to be formed.  Those are driven off when the extract is produced.

I've wondered about this.  When I make a starter with DME and boil it for 10 minutes on the stove, why do I get hot break?  I figured that would have been taken care at the maltster as well.

Malt extracts still contain the proteins from the grain mash.  The extraction process only removes water and volatile compounds (SMM, for instance).

[hubie]

I thought when they made malt extract that they took wort through the boil, so I always figured that the proteins should have coagulated out.

[redbeerman]

You are correct.  They actually produce the extract (liquid) under vacuum evaporation so that the boiling point is a lower temperature, thus no scorching.  Dry extract is usually spray dried.

Link to BYO article on extract making.

http://www.byo.com/stories/techniques/article/indices/30-extract-brewing/1106-making-malt-extract