[jimrod]

I had a fellow brewer tell me not to mill the whole bag of grain at once because in 4-5 weeks it won't be fresh and taste the same. I don't have my own mill so it's handy to mill it in advance.

Is that true?  Will there be a difference in taste or performance?

[Slowbrew]

I would agree with your friend.

I can't quote any specifics but generally anytime you open a package (in this case the barley grain) the item will spoil faster.  Increased contact with oxygen and ambient moisture will dull the flavor.

The time frame that this happens depends a lot on storage conditions.  If you are milling 50lbs of grain and putting it back in the original bag it will degrade fairly quickly.  If you put the milled grain in sealed bags then it will last longer.  Refrigeration will make a difference too.

I have my own mill now but I used to get my grain crushed at my LHBS.  If I kept it sealed it seemed to last 3 or so weeks without much issue.  Basically, if you can taste a difference it matters.  If you can't, it doesn't.

Not really very helpful, I know, but there is no definitive answer available.  To me at least.

Paul

[denny]

Based on my experience, yes there will be a bit of lessening of flavor.  In addition, when you have a large bag of milled grain, the fines tend t sink to the bottom of the bag so you have to be sure to somehow mix it up before you use it.

[davidgzach]

It all depends upon how it is stored.  But even in a sealed container, I would give it a month or maybe two max.  Denny also raises a good point about the small particulate.

Dave

[majorvices]

I disagree that it is a big problem. I think that as long as it is stored cool and sealed it can last for a couple months crushed with minimal loss of flavor. Probably even longer.

[denny]

I disagree that it is a big problem. I think that as long as it is stored cool and sealed it can last for a couple months crushed with minimal loss of flavor. Probably even longer.

I agree a couple months is probably closer to correct, but I've noticed degradation in shorter times.  I had a bag of grain milled and ready to go when I had a heart attack and couldn't brew for a while.  I sealed it up in a plastic bag and kept it in a cool dark place, but 6 weeks later there was a noticeable difference from when it was fresh.