grain question

what is better - to crush the grain just before brewing, or to crush it few days prior to brew day?

I heard that some grains need to "rest" for some time before being mashed...

I see no logic, but maybe there is scientific explanation.

I never heard of giving some grains time to rest except if you roast them yourself but other than that I just crush while my strike water is heating up.

Personally I think the fresher the crush the better.

I'm not sure about freshness of the crush, but I know of one reason to wait a day or two. Crushing creates a lot of dust in the air which can carry bacteria. That bacteria can land in your wort and on your equipment.

The only grain "rest" i've heard of is a protein rest; basically you mash at a lower temp before saccrifcation.

The only time I've seen a rest for grains is when you toast/roast your own. You let them sit in a paper bag for 2 weeks.

jaxn said:

I'm not sure about freshness of the crush, but I know of one reason to wait a day or two. Crushing creates a lot of dust in the air which can carry bacteria. That bacteria can land in your wort and on your equipment.

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The suggestion here is to not crush where you ferment and it is valid. But, if you are crushing then you don;t have a wort yet and any wort you create after the crush will be boiled so, your statement has some merit when proper context is applied.

Crushing just before mashing is best from my experience. If you crush the grain and let it sit for more than a few days or so the fatty acids in the germ, which you expose to air on grinding, begin to oxidize. This can result in some off flavors in your beer.

The rest period I think you are referring to is for freshly kilned or dried malt as others have referred to here. The theory there is that in commercial processing at least, the malt coming off a large kiln has a range of moisture from say 6% to 3%. Letting it rest in a silo allows the moisture to equalize to the normla range of 4%. This is important to commercial brewers as the moisture of the malt affects how it mills in terms of particle size distribution.

Dr Malt