Reduced yield from Rye

[PeteB]

My yield of alcohol per Kg of rye has never been great, but it was acceptable because I was producing a very nice Whisky

But the yield has dropped about 30%!!

I have almost exhausted every trial variation I can think of.

Does anyone know if the alcohol yields will fall off as grain gets older? My silo of rye is now 2 years old.

[Natrat]

Hey Pete,

are you using malted rye? The nominal silo life of malted rye is about 18 months. Un malted maybe 2 years. The grain gets friable, and when the hull collapses, the grain dust tends to either fall down the cone or stick to the sides of the silo (static)

Perhaps you were getting great yields from all the grain dust in the first batches? And now that you've used that, you're into the chaff...just an idea. Do you taste your grain before you mill it? I find that a quick crunch on the grain can tell me a lot about its condition...and sometimes I adjust my grain bill on the fly when I get into a new crop batch...just on the flavor/texture.

[PeteB]

I use 80% unmalted and 20% that I malt myself.

From the malting process I can see that the germination is still very close to 100% so that part of the grain quality has not reduced.

I said "silo" to save a bit of typing, it is stored in a shipping container that I can't auger it out any more because I am getting to the end, so I bucket it into bags. There should be no variation in the amount of dust etc.

[Natrat]

Weird.

Only other thing I can think of might be moisture content. But if they're germinating, one would think you're well in the ballpark. Did you drop the hydrometer?

[mendodistilling]

Malt it all. Mix it with newer grains.

[mendodistilling]

The shipping containers here in california seem to condensate on the inside of the unit, maybe when it was full it was acting as an insulator but as the mass has dropped inside its starting to affect the bulb temp on the inside and now finally affecting moisture levels.

secondly I have read that malt /unmalted grains should be kept at a low % moisture or it starts to rapidly deteriorate. It can last upto a decade if appropriate moisture is maintained.

[PeteB]

A visitor to my distillery a few weeks ago gave me a clue to my yield problem.

A grain is a living organism and it slowly consumes the starch to stay alive. It still germinates well but there is less starch.

As I said earlier, I tried the grain from my newest harvest and found it no better, but this appears to be a different problem. The grain was quite a lot smaller because of a dry growing season. Smaller grain has a lower % starch per Kg.

Mendodistilling, thanks for the suggestion but I doubt that humidity is the problem. The average humidity here is quite low and I have never seen any condensation in the containers. Also, you suggested to malt it all. Firstly that is a lot more work than doing 20% malt. Also I use the malt green so the roots and shoots go into the mash. With 100% green I suspect I could end up with whisky that smelt like boiled cabbage.

Coop had a similar yield issue about 3 years ago that generated a lot of discussion. His problem turned out to be a poor quality batch of grain, same problem as mine.

I have got my alcohol yield per batch back to where it was by increasing the quantity of grain per mash and adding some extra enzymes as well.

Thankyou all for the suggestions, they help me work through the possibilities.

Pete