Organoleptic to Actionable with the Birectifier

[The birectifier is available as a column and condenser for $900.]

Slowly, I’m starting to explore the birectifier and digest all the ideas surrounding it. I’m making a lot of progress, but there is still a lot to do. The special thing about the tool is that you can do so much with so little (and then build upon that). It is quite pragmatic for product development. The literature only describes usage for distilled fermented products like rum, but I suspect the tool can provide significant insights into the development of other aromatized products like gin, absinthe, and liqueurs like triple-secs (I have a lot of ideas for those!).

After having used this apparatus for over nine years of research in rum manufacture we are ready to pronounce it the most valuable single tool available for this kind of investigation. Its introduction into the routine work of rum distilleries would represent a great step forward in the scientific control of manufacture, and in the production of standard types of rum of the highest uniformity in chemical composition and quality. -Rafael Arroyo, April, 1945.

What the tool does is allow very high fractioning of small distillate volumes. No off the shelf conventional lab glass to do what it achieves. Traditionally, you take 250 ml of a 40% ABV spirit and you separate it into 8, 25 ml fractions every fifteen minutes (2 hour distillation run). A good metaphor is that it is like a scalpel, stethoscope, and/or a magnifying glass for spirits. It is easy to predict what congeners are in each of the fractions and comparisons can be made head to head against competitors, role models, and your own production generations. The tool can be used for yeast selection, fermentation optimization, tuning of still parameters, and decisions related to maturation.

Sub analysis can be conducted chemically via the classic titrations or organoleptically which is what makes it so powerful. Say you are only set up for acid titration, you can do that chemically, while in other fractions where you are targeting fusel oil, you can opt to weight that organoleptically using the exhaustive test. On the list of stuff to try is whether we can make surface tension comparisons between particular fractions to also tell us something actionable (relating to valuable long carbon chain congeners). As you grow in chemical sophistication, you can add other titrations.

Until chemical analysis beyond titration came along, the divine congeners like rum oil could not easily be looked at which is one reason why they are not widely represented in the literature. The birectifier is/was a way to isolate and target them. It also let Arroyo see where they were in the spirits run and revealed that they overlapped with the fusel oil fraction. This led to his selection of yeasts that produced appreciable amounts of rum oil while limiting fusel oil production.

[picture depict the elaboration of fraction 3 into the modified exhaustive test.]

The German literature gives a helpful framework for making organoleptic comparisons that can confidently become actionable. For every 25 ml fraction, 5 ml is set aside to perform a unique version of the exhaustive test. The other 20 ml from fractions 1-4, where most of the alcohol resides can be diluted to 60 ml and assessed organoleptically by tasting. Fractions 5-8, which are poorer in alcohol can be diluted to 40 ml and also assessed organoleptically. If the point of the exercise is to evaluate potential fermentation faults, they will show up in the later fractions.

For the special version of the exhaustive test, the 5 ml is taken and diluted to 10 ml [I get this 10 ml number from the math, but there likely was a typo in the German source document which printed it as 100 ml]. This 2x diluted sample is systematically diluted again to weight each fraction in absence of chemical analysis. If you are indeterminate, you can take the average of two dilutions or create a special dilution depending on your needs. It is possible that the reason they first diluted it 2x is because they did not have the incredible automatic pipettes we have today. Some of the below numbers also represent rounding on the part of the dilution ratio.

0.1 ml ca. 1:2000 = (100/.1)x2   = 2000
0.2 ml ca. 1:1000 = (100/.2)x2   = 1000
0.3 ml ca. 1:700 =   (100/.3)x2   = 667 * rounded
0.4 ml ca. 1:500 =   (100/.4)x2   = 500
0.5 ml ca. 1:400 =   (100/.5)x2   = 400
0.7 ml ca. 1:300 =   (100/.7)x2   = 286 * rounded
1.0 ml ca. 1:200 =   (100/1.0)x2 = 200
1.5 ml ca. 1:140 =   (100/1.5)x2 = 133 * rounded

Don’t forget, that x2 represents the first dilution from 5 ml to 10 ml. If you’ve got a great pippetor, you can forego it and tweak things.

The tweaked version without the first dilution and with no major rounding:

0.05 ml ca. 1:2000
0.10 ml ca. 1:1000
0.14 ml ca. 1:700
0.20 ml ca. 1:500
0.25 ml ca. 1:400
0.33 ml ca. 1:300
0.50 ml ca. 1:200
0.71 ml ca. 1:140

Also don’t forget, that if you’re not too confident in your 0.10 ml or your 0.05 ml, you can practice by putting them on a sensitive scale and calculating the volume using the density to see if your pipette is reliable enough.

The next step is understanding what the hell we’re looking at. The first fraction contains most of the esters and aldehydes of low boiling boiling point and low molecular weight, the ordinary stuff. This fraction is also very high in ethanol. The second fraction is similar in composition, but much less concentrated in congeners. The third fraction is primarily ethanol, but has traces of esters, aldehydes, and fusel oil. The forth fraction is the higher alcohol fraction and Arroyo reports that 70-75% of all the higher alcohols can be found there. Arroyo singles out the fifth fraction as the one that regulates quality. Most of the higher boiling point and high molecular weight congeners are located there. The major portion of rum oil is also located in fraction five. Fractions six through eight are made up of mostly water with small amounts of ethanol and minute amounts of high boiling point, high molecular weight esters and aldehydes. Arroyo tells us that when there are fermentation faults with “malodorous substances derived from protein degradation and decomposition products”, they will appear in these last fractions. This becomes important because “If these latter substances are present in liberal amounts they may tend to mask the aromatic effect of the other rum ingredients mentioned above.”

All this information can help with yeast selection and make more readily apparent that different yeast produce different products of metabolism other than ethanol. Once a yeast is selected, or a complication is added, such as a symbiotic bacterial culture, fermentation variables can be adjusted and their impact explored with the birectifier. Still tuning decisions can come after. A cut could be made deeper to reduce excessive ordinary congeners or shorter if more is to be allowed and the spirit is a candidate for long aging. If the ferment consistently proves to be high in rum oil, while relatively low in fusel oil, it may be a candidate to distill at a lower proof to retain an increased amount of higher boiling point, high molecular weight aroma-beneficial congeners without over accumulating fusel oil.

Fermentation faults may increase as distillers walk on the wild side of risk, adding complications to create grand arôme rums. Faults likely can be noticed through the noise with the birectifier before they run amok. Eventually experience will give us specifics to share with each other.

One application for the birectifier I was not previously too aware of is the ability to predict the duration of aging time required to bring a spirit to maturity. Arroyo described the concept outside of Studies on Rum in a document I only recently found. At the moment, I do not not think I can completely describe all the options, but it is something collective use of the apparatus and sharing of information will reveal.

Arroyo does give us some starting points:

The state of maturity may be judged in genuine rums from an examination of the true chemical constitution; but more so by the ratios existing among different constituents. For instance, a raw distillate will be a fast maturing rum under natural aging if it fullfills the following requirements:
(1) A low, or moderate numerical value (expressed in milligrams per hundred milliliters) in the constituents of the first fraction.
(2) A low ratio of first fraction components to those of the fifth fraction.
(3) A high ratio of total non-alcohol-number to the members composing the fourth fraction.
(4) A high ratio of esters to volatile acidity and to aldehydes.
(5) Presence of liberal amounts of rum oil in fractions five to eight inclusive.
(6) Absence of malodorous bodies in fraction to eight inclusive.
(7) High ratio of high molecular weight esters and aldehydes to low molecular weight esters and aldehydes.
The information necessary for this kind of chemical control in the distillery  is greatly facilitated by the introduction of the Luckow birectifier into the daily, routine work of the distillery laboratory.

All of the these concepts can be elaborated and a triage developed for influencing all preceding stages of production. A bang for your buck approach to increasing involvement will develop. Once we know what is possible, we will develop different approaches to get there. Arroyo tells us more:

As the raw rum matures in storage, the successive fractional distillations performed at intervals of three months’ time, will show the manner in which the raw spirit reaches maturity. At first there will be great changes in the composition of individual fractions and of the amounts of individual components present in different fractions. At first there will be great changes in the composition of individual fractions and of the amounts of individual components present in different fractions. The graphs showing these changes will be quite different also. But these differences will become less accentuated and striking as time passes and the maturing process goes on, until the time comes when the rum constituents show such states of balance and equilibrium that differences in analytical results and in the shape of graphs become so inconspicuous as to be insignificant. At this point the rum has reached maturity, and we may hope for very little improvement of taste and aroma thereafter.

Not all spirits are especially palatable out of the still, especially fractions experienced live. This process of evaluation during maturation can help increase the intuition it takes to make decisions related to distillation proofs and making cuts. If you’re daunted, he offers encouragement:

It is true that it takes time, labor, and expense to follow in this manner the maturing process of the raw rums in industrial practice; but at the same time the work is highly interesting, very enlightening, and above all profitable.

There will be a lot more to come about the birectifier as I tackle its use and applications.