Spent Grain Starter

[Merryb]

Hey all! We have a local brewery here in our small town, and they are
making some really good beers. I asked about getting some of their
spent grain, and they said ok! When I was in school, I made a starter
from another student's dregs, but can't remember exactly what I did. I
think I just kept feeding it until it was really happy. I'm looking
forward to doing this again- the bread was really flavorful. Any tips?
TIA!!

[Steve Bonine]

Spent grain is what is left after the sugars and enzymes are extracted
by heating malted barley to temperatures that are high enough to kill
any living yeast. Spent grain is great for providing texture to bread,
but as a basis for a starter it seems a poor choice. There's no yeast
and no nutrients.

[Merryb]

I thought that there was some residual yeast left- maybe my memory is
gone. I wonder if I added yeast before? I know it worked...

[Steve Bonine]

Yeast never touches spent grain. You are perhaps thinking of the
technique of using bottle-conditioned beer as the basis for a starter.

Here's the beer making process in a nutshell.

Grain, usually barley, is malted. That means that it begins to sprout.

The malted grain is mixed with water and heated to 150-160 degrees.
This releases the starch and the enzymes that convert it to sugar.

The grain is removed. That's the spent grain we're discussing.

The resulting wort is boiled to complete the conversion process. Hops
are added at this point, different hops at different times.

The wort is cooled and yeast is added. This is the first appearance of
yeast in the process. This is brewing yeast, not bread yeast.

The wort ferments into beer as the yeast converts the sugar into
alcohol. The amount of alcohol depends on the amount of sugar which in
term depends on how much grain was used in the first step.

When the fermentation is complete, most commercial beer is filtered and
pasteurized. This provides the clean and clear product that most beer
drinkers expect. It is then carbonated by using CO2 under pressure and
bottled or canned.

Sometimes the process of bottle conditioning is used. In this case, the
beer is not pasteurized and a little sugar or other fermentable is added
to the beer. It is then bottled. The residual yeast converts this tiny
bit of fermentable material into CO2, thus carbonating the beer in the
bottle. It is this type of beer that has a bit of viable yeast in the
bottle.