Vacuum herb dryer

[KennethT]

Has anyone experimented using a vacuum chamber to dry herbs?  Herbs dried the traditional way (low humidity, elevated temperature) take on a different flavor than when they're fresh.  Drying under a vacuum can be done at lower temperatures, maintaining a more similar flavor profile.

 

There has been some research done on this that I've read here and there, and there are some "vacuum ovens" that integrate low power microwaves to speed the process slightly, but they're very expensive.

 

I'd be curious to know about anyone's experiences....

[Coogles]

Never tried it before, but since I needed to prune the basil growing in my Aerogarden anyway I thought I'd give it a go.  My chamber sealer doesn't have the option of holding at vacuum so I sealed up the basil in a Ball jar at high vacuum (45 sec, ~99.9% vacuum according to the gauge) along with a little rice to act as a desiccant.  I'll open up the jar in a few hours to see how it looks and repeat the vacuum a few times if the herbs aren't dry enough.

[Coogles]

The vacuum removed some of the moisture but not enough to dehydrate the herbs, I don't think the volume of the Ball jar (1 quart) is big enough to allow enough of the water to boil off under vacuum.  After repeating the vacuum procedure several times the leaves had shrunk significantly and gone limp but were still moist to the touch.  Something like a vacuum degassing chamber would probably have a better chance of doing this successfully due to the larger chamber size and the ability to keep it under vacuum indefinitely.  

[Kerry Beal]

On 1/7/2019 at 1:09 PM, KennethT said:

Has anyone experimented using a vacuum chamber to dry herbs?  Herbs dried the traditional way (low humidity, elevated temperature) take on a different flavor than when they're fresh.  Drying under a vacuum can be done at lower temperatures, maintaining a more similar flavor profile.

 

There has been some research done on this that I've read here and there, and there are some "vacuum ovens" that integrate low power microwaves to speed the process slightly, but they're very expensive.

 

I'd be curious to know about anyone's experiences....

I used to have a vacuum microwave - picked up from ebay I think. It would have worked for something like this. I put a vacuum jar in it, attached it the vacuum tubing that ran from the jar through to the back wall of the microwave to a pump, then microwaved on very low powers for short bursts. I never recall doing any herbs in it. My aim at that time was to concentrate liquids. 

[KennethT]

40 minutes ago, Kerry Beal said:

I used to have a vacuum microwave - picked up from ebay I think. It would have worked for something like this. I put a vacuum jar in it, attached it the vacuum tubing that ran from the jar through to the back wall of the microwave to a pump, then microwaved on very low powers for short bursts. I never recall doing any herbs in it. My aim at that time was to concentrate liquids. 

Thanks.  I've read a bunch of research papers talking about using vacuum microwave (sometimes called vacuum ovens) to dry herbs.

Do you recall from your time using it how it worked for your purpose?

[Kerry Beal]

Unsatisfactory - but possibly due to some issues with the microwave itself as I recall.

[btbyrd]

Freeze dried herbs are a thing. Seems like a more common way to dry herbs under vacuum than using a vacuum microwave or whatever.

[KennethT]

The results from freeze dried and the other kind of dried are totally different.  One wouldn't use one process instead of the other.