posted by Dave Arnold
We’ve been working hard over the past four years to make the best possible hooch. I thought we were doing a top-notch job, but yesterday I discovered I was wrong. That’s because yesterday we split a distillation run into 27 distinct parts based on volatility, nosed and tasted them all, and blended the best of them back together: super-hooch. This test was done with home-made Thai basil eau de vie, and it was truly excellent.
As many of our readers know, the rotary evaporator (rotovap) is perhaps my favorite piece of equipment. It allows us to distill at very low temperatures, with very complete flavor recovery. For example, the aforementioned eau de vie never went above room temperature. For more on how a rotovap accomplishes these miracles, see the rotovap primer.
Our distillations are more akin to gin than to traditional distillation –they are re-distillations of already purified spirits, with the intention of capturing flavor. Traditional distillation’s primary purpose is to concentrate ethanol. You start with a lower proof alcohol (such as whiskey mash, or fermented potatoes) with some impurities. When you distill, you concentrate these impurities as well as the ethanol. The first liquid to leave the still is referred to as the heads, and it is full of nasty stuff. After the heads come the heart –the good stuff you want to drink. Lastly, the tails – no good. Too much heads or tails makes for popskull moonshine that can make you sick. Distillation enthusiasts often ask me if I cut the heads and tails out of our rotovap distillate. With re-distillation there is no need to remove heads and tails for safety, though it is typical to remove them for taste. At the school, we usually don’t separate the heads from the heart — I like the heads. But we do cut off the tails –we just stop the distillation when the flavor tapers off. Then it occurred to me: What if some phases of the distillation process produce better flavors than others? In alcohol-concentration distillation the breakdown into heads heart and tails makes sense, but in flavor-based distillation there isn’t any reason to assume that the best flavors should be concentrated in the center of the run, or that undesirable flavors will only occur in the beginning or end. I pride myself on getting the maximum flavor out of my distillations, but what if some of the flavors I’ve been collecting are not so good?
Because different aroma and flavor compounds have different volatilities, they distill at different times — and so the flavor of the distillate changes over the course of a run. What if I separated the entire distillation into small samples of slightly different volatility and checked their flavor individually? Most people with rotovaps can’t taste the distillate as they go. Rotovaps are sealed systems under vacuum –that’s how they work. To taste the distillate, you have to stop the distillation, break the vacuum, pour off the distillate, and restart. Years ago, I addressed this limitation by building a pump system that connects to the output of my rotovap (see picture below). To this pump system I added a bunch of luer-lock stopcocks that allow me to divert the flow of distillate into any one of four small graduated cylinders, or into a larger collection beaker.
Thai Basil Eau De Vie
We blended 750 mls of vodka with 82.5 grams of Thai basil leaves, put them into the rotovap and distilled with a bath temperature of 40°C and a condenser temperature of -17°C. In a rotovap, the product you’re distilling is a good 15-20°C cooler than the water bath, so the Thai basil was never heated above room temperature. With the new stopcock system we easily separated the distillation into 20ml samples. We collected every 20 mls that came off the rotovap, then capped and labeled them. Some samples were a little more, or a little less than 20 mls, so we recorded the actual number of mls of each sample, accurate to 0.5 ml. After we collected 542 mls of distillate (27 samples), we shut down the rotovap and got to tasting.
We checked every sample for alcohol content with a refractometer. The first two samples read lower in alcohol than the second two did. I don’t know if they were actually lower in alcohol, or if impurities made them read lower. We smelled each sample in order, then tasted them. We organized the samples into four groups:
- Green: everybody liked these
- Yellow: everyone thought these were OK
- Orange: some people hated these, some thought they were OK
- Red: everyone hated these
The samples were tasted by 6 people –we will do tastings with larger groups very soon. Here’s the tasting chart, with abbreviated notes:
As I had hypothesized, there were samples right in the heart of the distillation that we all hated –I had hoped there wouldn’t be; because diverting the distillate at precise times isn’t the easiest thing to do.
Blending spirits is a complex problem. Sometimes, small additions of flavors you don’t like can actually make the drink as a whole taste better –counter-intuitive, but true. We had to test whether removing the parts of the distillation run that we didn’t like improved the taste of the whole distillate. We did some blending and made four different eau de vies:
- 3 mls from every vial in the green group: “Green”
- 3 mls from every vial in the green group AND the yellow group: “Yellow”
- 3 mls from every vial in the green group, the yellow group and the orange group: “Orange”
- 3 mls from every vial: “Red”
I thought Green would be the hands-down winner, but three of the six people at the tasting preferred Yellow. Everyone chose Green and Yellow as their favorite two liquors. The people who chose Green had a strong preference for Green, while Yellow lovers tended to like both. Half the tasters preferred the Red liquor to the Orange one. I was surprised that the Orange liquor would score lower on some people’s ratings than the red because the red samples were unanimously disliked on their own –goes to show the whole isn’t just the sum of its parts. One fact is certain: selectively removing portions of the distillate that occur in the “heart” of the run can improve the flavor of the hooch you make.
We ran two more Thai basil distillations using the same amount of liquor and basil as the first test: one we did the old way, and one we did by diverting the distillate according to the recipe for “Yellow” above. The one made like Yellow was better than the one made the old way, showing that the same flavors come out of the distillation at the same point in the run from batch to batch.
Now we have a problem: how do we distill this way on a regular basis? How are we going to get our yield up? Is there a way to re-use the red and orange part of the distillation, the way a pro distiller does?