It’s probably the humidity packs making the extract come out dark. Not the initial freeze drying.
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Are we talking cryo-cold? What vacuum depth?
My guess would be ice nucleation from the thawing process making the chlorophyll and other nasties more prone to be released when extracted.
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Whatever vac depth a HR goes at while it goes through its motions and regular freezing cold
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nahh we get stuff thats been stored with humidity packs for 6months+ and it runs just fine.
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thats what im thinking as well.
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hmmm ill have to look into hydration beads iv never used them before. who makes them?
To add on to this, the freeze drying process typically ruptures or weakens the cell walls in plant material unless done extremely slowly and carefully, making the chlorophyll much easier for solvents to access and extract.
EDIT: Looks like my street knowledge regarding the rate of freeze drying may not hold up with further review. Still stand by the rest of the comment regarding weakening cell walls and exposing more chlorophyll and undesirables to the solvent.
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doesn’t that mean you’re doing it wrong?
either the freezing or the drying?
edit: more likely the freezing.
learned here that there was a “remove unfrozen water” phase in the drying. makes sense. you sublime most of the water…
https://www.sciencedirect.com/science/article/pii/S0168365921003400
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Perhaps, its my understanding that it happens upon freezing no matter what, nature of the crystals formed by water. Cell walls weaken during thaw from the crsytals formed, I’ve heard it likened to water in concrete when its curing. I’m guessing this is why fresh frozen is never run after being thawed.
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Ah that definitely makes sense.
You sure about that?
wanted to (dis)agree with @SauceBossNW, went looking for data one way or the other.
the paper linked above isn’t specifically about cell membranes, but its still worth a read.
imo it makes it clear that “there will be leakage”…not sure it supports “nucleation during thaw”.
seems to make it pretty easy to argue “nah, you just froze it wrong”…(at least till you rule that out for us).
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I love the responses that this thread has gotten so far i wanna say thank you to all that have put your experience and personal testing into here to help further the topic and understanding of the FD bud game.
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Huh?
What data are you interested in, specifically?
Coming from a micro background, preserving cell walls is fairly common knowledge.
You get it very cold, very fast, and you use interferents.
Of course, we can’t really use interferents in the case of fresh frozen, but we can certainly get things very cold very fast, but yeah, there’s definitely a problem with the standard approach to lyophilization depening on how you’re doing it.
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That was actually why I asked about cryo-cold. I wasn’t trying to be facetious, but liquid-nitrogen cooling followed by sublimation/refreeze cycles could minimize cell wall damage and “leaking” from left over water that wasn’t sublimated.
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How would we go about leveraging ln2 to rapid-cool the shipping-container-sized-freeze-dryer posted above? What additional structural considerations should one concern themselves with?
My first thought is to use ln2 misting lines? and like, a big ole’ prv and maybe a gate valve for the vacuum system? Just make it rain liquid nitrogen till you’re at least -70c within the meatiest shelf of grass in the middle of the room, vent it all to save your vacuum system from unnecessary wear n’ tear. At the end of every sublimation cycle it rains.
We’ve talked about doing a ln2 freeze tunnel for initial freezing and also ln2 freeze tunnel right before loading into the freeze dryer. This would give us the best possible quality but we are not sure if its a justifiable process to add. But in theory it would be the best thing to do.
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Have you tried pressing any of the bud?
I would think that it would be important to consider the time between the end of a sublimation cycle and the point at which it’s all a solid again. I would think that the more times in the process that cycle occurs, the more likely some cell damage may occur, depending on the length of time as stated above.
But, like, it probably wouldn’t take nearly as much ln2 to re-freeze from a sublimation cycle as it would to strip the bulk of the initial energy in-system.
(I wish my job gave me an R&D budget 
)
Additional stoner thought - > what if the ln2 wasn’t just vented, but captured instead? Like, if it’s only used just at the end of a sublimation cycle, it won’t be That much, yeah? Run it to a compressor and a heat exchanger and back to the -ln2 tank- expansion/prechilling tank??
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