The Unscientific Re-Test
For several months I was too busy to pursue further legal distillation tests. Then I remembered I had promised to bring my rotovap to the 2010 Star Chefs demonstration, and the following occurred to me:
1. Crap, I don't want to lug my chiller with all the tubes and propylene glycol to Star Chefs.
2. Crap, they never have enough power in the demo rooms and I'll probably blow a circuit running the chiller and the rotovap.
3. They will have a boatload of liquid nitrogen at the event, which I could use to run the cold-finger (they ran out last year so they over-ordered this year).
4. People might like to see a legal distillation demonstration.
Legal it would be.
Legal Distillation at the Star Chefs Demo (for the rest of the demo, see my upcoming post)
I decided my earlier tests were fundamentally flawed. I had been comparing the results of cold-finger distillation to standard condenser distillation by trying to match the yield and proof of the cold-finger product to the standard product. What if that method was biased against the cold-finger?
For the Star Chefs demo I decided to focus only on making a delicious product with the cold-finger. I vacuum-bagged Thai basil and orange peel in ice water to thoroughly saturate the leaves and peels with water.
Experiments I had run with Tony Conigliaro at his bar 69 Colebrook Row in London (where he is allowed to re-distill with alcohol—the lucky cuss), showed that leaves not fully saturated wouldn't give up their flavor as readily. You can't blend the leaves to mingle their flavor with the water, either—blended herbs distilled with water in the rotovap taste brown and swampy. The swamp thing doesn't happen when you blend herbs and liquor. In a side-by-side test, distilled blended mint plus ethanol beat distilled vacuum-saturated mint plus ethanol; distilled blended mint in water was wretched, while distilled vacuum-saturated mint in water just lacked power.
I loaded the saturated peels and Thai basil in the rotovap, sucked a vacuum, filled the condenser with liquid nitrogen, lowered the distillation flask into the water bath, and commenced distillation. I left Nastassia to finish the process while we went on with the rest of the demo. When she felt she'd pulled off all the water she could, we melted the ice off the condenser with the 200-proof and tasted. It was fantastic. Really fantastic. Nastassia claims it was good because the rotovap required a woman's touch. I'm not so sure because she says that about everything.
The outcome of the demo left me very, very optimistic about the future of legal rotovapping.
Tips and Comments on Running the Cold Finger:
1. Running a cold finger isn't the same as running a standard condenser. Do not add coolant to the cold finger until you have established a partial vacuum in the system. If you ignore this warning you risk clogging the vacuum intake of the condenser with ice crystals—a pain in the rear.
Watch out for condensation here.
2. It's normal for the ice at the bottom of the cold finger to melt under heavy distillation, even with something as cold as liquid nitrogen as your coolant. Condensing water requires a lot of power.
3. A mixture of dry ice and 200-proof ethanol is food-grade and will probably work as well as liquid nitrogen. Dry ice isn't as cold as, but has much more cooling power than, an equal amount of liquid nitrogen. Dry ice is also easier for most people to source. Unlike me—I have liquid nitrogen dribbling out my ears.
Even though liquid nitrogen is super-cold, you will see liquid water at the bottom of the condenser and in the receiver flask. This is normal.
4. As a corollary to 3, you will need a lot more liquid nitrogen than you think. It will take many, many liters to condense 1 liter of product. Keep adding liquid nitrogen throughout the distillation (it runs out quickly). Don't be alarmed, but you will get a huge vapor plume once the distillation starts in earnest.
5. Make sure to melt the distillate off the condenser immediately with 200-proof ethanol. I have no scientific proof, but every distillate I have made with water loses its aroma very quickly. I feel melting it with liquor helps fix the flavor, but I'm willing to be proven wrong.
6. It is extremely difficult to determine how much product you have distilled off your mixture in a cold finger condenser. Some protocol has to be devised to figure this out or recipes won't be repeatable (suggestions anyone?).
Up for Comment:
My old theory as to why liquor-based distillation is inherently better than water-based was threefold:
1. Flavor is captured better in distillations that go through a range of boiling points with large amounts of distillate produced all the time—the way an ethanol-water system works. The range of boiling points in a water-based distillation is much lower, plus many of the more volatile compounds that boil at significantly lower temperatures than water will be boiled off unnoticed in a water-based distillation.
2. Ethanol and ethanol-water mixtures are inherently better at carrying volatile aromas and flavors than water alone.
3. Once distilled, ethanol mixtures hold volatile flavors better.
How do these theories jibe with the new water-based distillations?
First, I am willing to be challenged on all of these theoretical points, as they were arrived at through experience, not scientifically.
If my theories are correct, point 1 is partially addressed in the legal method, because the traces of flavor that get lost in a water-based distillation in a standard condenser freeze on the side of the cold finger and would then be dissolved in straight alcohol at the end of the distillation run, which solves the problem from theory 3.
As to the first part of theory 1 (that a range of boiling points in a distillation leads to better flavor) and theory 2 (that ethanol is a better flavor carrier than water), I guess it's open for discussion. In fact, I haven't been able to devise a good side-by-side test where legal distillation was as good as illegal, so maybe these theories are correct, and illegal distillation is inherently superior. The success I had at Star Chefs, however, leads me to think my theories should be revised.
This post also appears on CookingIssues.com. All photos courtesy of Cooking Issues.