geraldmarken

Artemisia pre distillation

15 posts in this topic

I'm submitting a formula to the TTB that contains Artemisia ingredients which I infuse into spirit before distillation. I'm feeling confident that the finished product will be thujone-free but I want to make sure I'm not missing something.

Thujone has a boiling point of 394ºF. Since I will be heating the spirit to just above 174º during distillation, there will be no thujone in the resulting distillate. 

Is this correct, or is it too oversimplified to be practical? 

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Oversimplified and wrong. Many chemicals can be carried in trace quantities during distillation far below their boiling points. Remember, boiling point is the temperature at which the chemical has a vapor pressure of one atmosphere. At lower temperatures, it will have a partial pressure below that. Even something with a boiling point 100s of degrees higher might have a very low but some vapor pressure at 174°, but it would only take very low pressure to get ppm in the distillate. Thujone has to be below detectable limits, or 10 ppm. If you are distilling with wormwood, they will require a lab sample. Luckily, they usually can get the measurement completed rather quickly these days.

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Many other botanical's essential oils also have high boiling points but they all come over into the distillate when you make gin. It's because oil and water are immiscible. And when you have two liquids that are immiscible (they do not dissolve in one another, they separate) but they can and will both still boil...and the boiling point of the immiscible liquids will be lower than the lower of the two boiling points!  The temperature to boil will be when the summation of the vapor pressures of the two liquids is equal to the atmospheric pressure, which will end up being slightly less than the boiling point of water (the lower of the two boiling points). So the oil will end up in the distillate...the alcohol present will even further reduce this boiling point.

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Not quite right, glisade. The actual boiling point of immiscible liquids are not really affected if they are truly immiscible. Miscible liquids will have a depressed boiling point from the value of the weighted average of the two constituents. In addition to the affect I described above, however, there is also the fact that it can be energetically favorable for an immiscible liquid in a poor solvent (like oil in water) to be in the vapor (steam) rather than the boiling solvent, at the boiling temperature of the solvent. In that case, some of the oil will be carried with the steam, even though it is not soluble, and then will separate out again as the steam condenses. This is common toward the end of tail runs of oil-containing mashes, like corn, for example.

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Thank you both for the help. I'm gonna sit with it a while to make sense of it, but I have one more immediate question. What happens if the TTB detects an unacceptable thujone content in my sample? Do they close the formula application or just return it for corrections?

Do either of you know any strategies for reducing the guesswork in determining thujone content before sending it to the TTB, or is it entirely trial and error? Obviously the thujone content of a given specimen is variable so that seems to preclude any predictive thujone management. On the other hand I'm not aware of any ways to measure thujone content without gas chromatography. Maybe I could buy some relatively pure thujone to acquaint myself with the aroma.

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1 hour ago, bluestar said:

Not quite right, glisade. The actual boiling point of immiscible liquids are not really affected if they are truly immiscible. Miscible liquids will have a depressed boiling point from the value of the weighted average of the two constituents. In addition to the affect I described above, however, there is also the fact that it can be energetically favorable for an immiscible liquid in a poor solvent (like oil in water) to be in the vapor (steam) rather than the boiling solvent, at the boiling temperature of the solvent. In that case, some of the oil will be carried with the steam, even though it is not soluble, and then will separate out again as the steam condenses. This is common toward the end of tail runs of oil-containing mashes, like corn, for example.

Bluestar,

Not sure if there's a misunderstanding of what I wrote but check out this link: http://www.separationprocesses.com/Distillation/DT_Chp01m.htm

Key point from the link:

For example, the 2 liquids A and B are immiscible. At equilibrium, they each exerts equilibrium vapour pressure PVP,A and PVP,B respectively. Thus the total pressure exerted is

P = PVP,A + PVP,B

The equilibrium vapour pressures of water and benzene at 100 oF (37.8 oC) are 0.95 and 3.30 psia respectively. The total pressure exerted is therefore (0.95 + 3.30) = 4.25 psia. Note here that in the calculations of total pressure, the actual amount of each is immaterial.

An important outcome is that the boiling point of an immiscible mixture must be lower than that of either of its components. Again, using water-benzene mixture, we note that the mixture will boil when the total pressure exerted by the mixture equals the atmospheric pressure, 14.7 psia.

This temperature is 156 oF (68.9 oC), when the equilibrium vapour pressures of water and benzene are 4.45 and 10.25 psia respectively (thus, total 14.7 psia). Note that the mixture boiling point is lower than that for pure water 212 oF (100 oC) and pure benzene 176 oF (80.2 oC).

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55 minutes ago, geraldmarken said:

Thank you both for the help. I'm gonna sit with it a while to make sense of it, but I have one more immediate question. What happens if the TTB detects an unacceptable thujone content in my sample? Do they close the formula application or just return it for corrections?

Do either of you know any strategies for reducing the guesswork in determining thujone content before sending it to the TTB, or is it entirely trial and error? Obviously the thujone content of a given specimen is variable so that seems to preclude any predictive thujone management. On the other hand I'm not aware of any ways to measure thujone content without gas chromatography. Maybe I could buy some relatively pure thujone to acquaint myself with the aroma.

Geraldmarken,

Search "thujone content" there's a thread with similar issues about how to estimate the amount of thujone content in spirits.

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Bluestar, thanks for handling what I've come to call the "magic boiling point myth", which often ends with the proponent stating that if you can hold the wash temperature higher than the boiling point of ethanol, but lower than that of water, you can get just ethanol out of the condenser. I've been known to rant on the subject, and you did much better than I often do.

Actually, as beverage distillers we almost never run into totally immiscible liquids, although we commonly deal with non-water-or-ethanol mixtures that approach concentration of immiscibility. Our gin, for instance, is close to louching (incipient immiscibility), such that temperature or ethanol concentrations can cause or reverse louching. I think everyone's absinthe is similarly unstable.

Even in essential oil distillation, where those oils are mostly immiscible with water, much of the oil is actually mixed with the water as a hydrasol,

Hope I didn't muddy the water.

 

 

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On 3/29/2017 at 1:46 PM, glisade said:

Bluestar,

Not sure if there's a misunderstanding of what I wrote but check out this link: http://www.separationprocesses.com/Distillation/DT_Chp01m.htm

Key point from the link:

For example, the 2 liquids A and B are immiscible. At equilibrium, they each exerts equilibrium vapour pressure PVP,A and PVP,B respectively. Thus the total pressure exerted is

P = PVP,A + PVP,B

The equilibrium vapour pressures of water and benzene at 100 oF (37.8 oC) are 0.95 and 3.30 psia respectively. The total pressure exerted is therefore (0.95 + 3.30) = 4.25 psia. Note here that in the calculations of total pressure, the actual amount of each is immaterial.

An important outcome is that the boiling point of an immiscible mixture must be lower than that of either of its components. Again, using water-benzene mixture, we note that the mixture will boil when the total pressure exerted by the mixture equals the atmospheric pressure, 14.7 psia.

This temperature is 156 oF (68.9 oC), when the equilibrium vapour pressures of water and benzene are 4.45 and 10.25 psia respectively (thus, total 14.7 psia). Note that the mixture boiling point is lower than that for pure water 212 oF (100 oC) and pure benzene 176 oF (80.2 oC).

True for a true immiscible liquid system. Some oils in water obey this well. But many are slightly miscible, so they don't obey this rule exactly. And some are immiscible as liquids, but not as gases, and then this rule breaks down again. In the case of oils during gin or absinthe distillation, it is further complicated by it not be a two component immiscible system, since there is significant alcohol in the system, and the oils are soluble in the alcohol. So, oils that come across with heads are usually not showing the "steam distillation" effect, in which case they could raise, not lower, the boiling point. Actually, the oils coming across in the end of tails, as I described above, are much closer to "steam distillation" as you describe above, because most of the alcohol is gone. Usually, oil partial pressure is so much lower than the water in this case, that it only depresses the boiling point a small amount, and only small quantities of oil are carried with the water.

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1 minute ago, bluestar said:

True for a true immiscible liquid system. Some oils in water obey this well. But many are slightly miscible, so they don't obey this rule exactly. And some are immiscible as liquids, but not as gases, and then this rule breaks down again. In the case of oils during gin or absinthe distillation, it is further complicated by it not be a two component immiscible system, since there is significant alcohol in the system, and the oils are soluble in the alcohol. So, oils that come across with heads are usually not showing the "steam distillation" effect, in which case they could raise, not lower, the boiling point. Actually, the oils coming across in the end of tails, as I described above, are much closer to "steam distillation" as you describe above. Usually, oil partial pressure is so much lower than the water in this case, that it only depresses the boiling point a small amount, and only small quantities of oil are carried with the water.

Ya totally agree. I just wanted to point out to the OP that no matter how he was distilling: steam distillation with just water and essential oil (immiscible) or alcohol distillation with various solubles (miscible) that he was going to get thujone. Basically, as long as the liquid mixture boils (immiscible or miscible) he's going to get all the components to come over though in different amounts at different times. And that the "magic boiling point myth" does not exist even with mixtures that don't combine.

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34 minutes ago, glisade said:

Ya totally agree. I just wanted to point out to the OP that no matter how he was distilling: steam distillation with just water and essential oil (immiscible) or alcohol distillation with various solubles (miscible) that he was going to get thujone. Basically, as long as the liquid mixture boils (immiscible or miscible) he's going to get all the components to come over though in different amounts at different times. And that the "magic boiling point myth" does not exist even with mixtures that don't combine.

True, unless extreme fractionation is going on, like in a 40 plate vodka still!

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8 hours ago, bluestar said:

True, unless extreme fractionation is going on, like in a 40 plate vodka still!

I completely agree. I just tend to look at everything through a potstiller's eyes,

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I agree with the previous analysis, but want to add something that I found in my own journey to getting my absinthe approved. If you're experimenting outside of the usual ingredients of traditional absinthe, it's possible to tip the scale of thujone in the absinthe. I tested with Cedar Leaf Tip, which contains more thujone than wormwood, though I wasn't able to find clear amounts before "hoping for the best" and sending it in for TTB testing. Came back 56ppm or so thujone in the absinthe. I swapped that ingredient out and passed no problem. As long as your only ingredient containing thujone is the wormwood, I doubt you'll have much a problem. Be mindful about other ingredients that contain thujone however (rosemary, cedar leaf tip, so on).

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On 4/2/2017 at 4:56 PM, JazJarzewiak said:

Be mindful about other ingredients that contain thujone however (rosemary, cedar leaf tip, so on).

Sage can have very high levels of thujone.

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