Steeping Roast Grains - Is This Normal?

[waggastew]

I steeped some mixed grain at 70degC this morning for a kits & bits Porter. It was a mixture of choc wheat, roast barley, choc malt and crystal. When I removed the lid to strain it into the pot the top layer of liquid had that shiny/oily/rainbow colored film I usually associate with polluted streams/oil.

It got me thinking about the compounds formed when you roast/burn grain. Most of the major types of dyes used in industry are/were derived from coal tar. I also know that too much charcoal on your bbq beef is bad.

Anyone else seen this?

 

[felten]

I seem to remember seeing the same thing when I was cold steeping some RB and carafa S.

 

[waggastew]

Cool, I assume that its not a bad thing given those grains have been used for hundreds of years! Just kinda weird when you see it for the first time.