Roller mill vs Hammer mill, 3 day vs 7 day fermenting, Parker Beam explains

[Vadertime]

I have to admit, I am a sucker for YouTube bourbon videos, it makes me drink less alone when I drink alone. There are some real gems on there, especially the UK Nunn Center Oral History videos. In one Parker Beam shares some very interesting historical bits about how the old timers and the newer (less than 100 years old) distillers do thinga:

http://youtu.be/bNl5DvAn-Ts

Why would hammer mills make the fermentation hotter? Is that due to uneven particle size and a higher percentage of fines? Also, what difference would 3 day and 7 day fermentation make? Obviously 3 days is more than double the yield, so based on volume it would be preferrable. But how would it affect taste?

Cheers

[wadewood]

The big guys all use hammer mills now, but some of the craft distillers are using roller mills. I know Firestone and Robertson in Ft. Worth is using roller mill (their product is still aging).

[squire]

I believe he was talking about a build up of heat as the grain was being milled. With a hammer mill the grain can be slightly scorched but of course the experienced distillers know how to avoid that.

[sutton]

Just guessing from my own wine fermentations:

Faster fermentations (which usually means hotter fermentations) can stress the yeast and produce off-flavors or stick a fermentation if the yeast die off in the heat. On the other side of the coin, a warmer fermentation can sometimes extract goodies that a cooler one will not. I suppose the faster you ferment the more you can turn that capacity over, depending on your ability to distill it as it is produced.

[squire]

Yes, too much heat can stress or even kill the yeast which is why in the old days they used to shut down the distillery during the hot summer months.

[squire]

Stressed yeast can also product some odd taste notes that will carry through into the distilled whisky.