[So it turns out the reason Robert Léauté got selected to give the lecture was because of the Remy Martin-Scramsburg brandy collaboration that I had never heard of. In 1982 they invested a lot of money to build a world class Alembic distillery in Carneros.
Here is a great background piece from 1985. This great articles from 1986 shows how silver tongued and well spoken Robert Léauté is. Scramsberg had backed out of the partnership in 1987. And this Etude brandy might be a product of that distillery. I suspect they are still laying around liquor stores. This article from 2002 tells of the closing and says glowing stuff about the product they were making. I think they were ahead of their time. The cocktail movement and spirits renaissance hadn’t happened yet.]
The James F. Guymon lecture series is very cool and there are a few other lectures from the series I want to track down. For the 40th annual meeting of the American Society for Enology and Viticulture, Robert Léauté gave a talk about alembic distillation. Léauté had been with Remy Martin since 1973 and at the time was head Cognac master, research and development manager, and RMS vineyards technical adviser.
The presentation which I read as a paper is unique because of how articulate and concise it is. Léauté covers things other people gloss over which makes the paper invaluable to beginning distillers trying to sort out some curiosities not found in other texts. Most texts about distillation are either too simple or far too advanced. It has been hard to find explanations for practices geared towards intermediate levels of involvement.
Léauté doesn’t cover everything I’ve been curious about, but I’m hot on the trail of explanations to those phenomenons. Many of the things I’ve written need to now be reconsidered in the light of these new concise explanations. Thanks Robert!
**The shape of the Cognac still head which is approximately 10% the size of the boiler provides a small amount of reflux thus influencing the degree of equilibrium (Equilibrium influences how volatile components distribute themselves).
**Léauté mentions the hydrometer port and how it is used to filter the distillation. This he unfortunately glosses over. Germain Robin also mentions filtering the distillate at this point and claims to use unbleached toilet paper. [I later solved this mystery in Whiskey Verdigris.]
**Simple easy to follow charts show how particular volatile components present themselves during the heads, hearts, and tails such as:
acetaldehyde & ethyl acetate
ethyl caproate, isoamyl acetate, ethyl caprylate, ethyl caprate & ethyl laurate
methanol, isobutanol, methyl-2-butanol & methyl-3-butanol
acetic acid, 2-phenyl ethanol, ethyl lactate & diethyl succinate
and finally furfural
The curves and their simplicity illustrates the significance and priority of separating heads and tails.
**A gem is Léauté’s explanation of how volatile compounds distill. Previous explanations I have read from Maynard Amerine seemed more complicated and harder to grasp.
“Each volatile component will distill following three criteria: boiling point, relationship with alcohol or water, and the variation of alcohol content in the vapor during the distillation. With respect to the relationship with alcohol or water, there are several possibilities: (1) the component is completely or partially soluble in alcohol and will distill when the vapor is rich in alcohol; (2) the component is soluble in water and will distill when the vapor is low in alcohol; (3) the component is soluble in both alcohol and water and will distill throughout the entire distillation; or (4) the component is not soluble in water, but the water vapor will carry over this component (hydrodistillation).”
This starts to explain the phenomenon where components with fairly high boiling points come across at the beginning of distillation. Boiling points are not the whole story.
Type 1 components are acetaldehyde and ethyl acetate because they have low boiling points and are completely soluble in ethanol so they end up in the heads.
Type 2 components which also end up in the heads have fairly high boiling points (above that of water) but are completely or partially soluble in ethanol. Fatty acids and fatty esters are in this category.
Type 3 components which are in the heads and the hearts “have a low boiling point (not above 200°C)” are soluble in alcohol and are completely or partially soluble in water. Examples are methanol and some of the higher alcohols. Methanol is harder to separate than people think.
Type 4 components which start during the middle of the heart have a boiling point above that of water and are soluble or partially soluble in water such as acetic acid or ethyl lactate.
Type 5 components (5 wasn’t yet mentioned but these are defined as appearing during the distillation) have a high boiling point and are very soluble in water. They start during the middle of the heart. Furfural is a type 5.
**Léauté mentions that “higher heat is favorable for the less volatile components, as increased heat [applied to the boiler] will allow them to distill earlier and to be present in the first fractions of the distillation in higher concentration.” what isn’t clear is if Cognac distillers use this idea at any point in the run or if they only keep consistent heating programs. I haven’t found an answer to the question whether applying significant amounts of energy to the boiler changes volatility through super-heated hot spots or through a slight pressure build up. Amerine references one paper which might be the precedent for the observation in a journal article (a 1940 Australian brewing journal) and I’ve requested it through inter library loan but it hasn’t turned up yet. I suspect this idea could be used to capture as much aroma as possible when re-distilling commercially produced spirits such as modifying chartreuse or a adding aromas to whiskeys, etc.
**Unlike other papers this one acknowledges three distillation “processes”. The first two are the usual but because in Cognac they take a “heads 2” fraction from the second distillation the third process is a unique distillation where the heads 2 fraction gets recycled and reprocessed.
**When describing each distillation phase, with the first phase Léauté mentions that “Each fraction is obtained at a temperature below 60°F. In this case, they are removed by filtration combinations between sulfury components and copper and a part of fatty acids and copper (Fig. 22).” The reference to figure 22 points to the furfural chart so I suspect it may be a typo and he meant to reference figure 21 which covers acetic acid. It isn’t clear what exactly Léauté means. Germain Robin also references a specific condensing temperature for different fractions which I have never seen described in whiskey or rum production.
For the second distillation “heads and Cognac are obtained between 62°F and 66°F and the secondes below 60°F like the brouillis during the first distillation (Fig. 25).”
The slight change in temperature at the end of the run may help certain components come out of solution so they can be separated by the “filter”. It is probably only necessary when the distillate is rich in those components. Though the temperatures seem close together, the span might be all that you can practically change such a large volume of water by in a fairly short period of time. It is never said whether they use glycol chillers to keep the temperature precise. I suspect that the procedure and its high involvement (a term I like to use to point out varying levels of attention to detail) does not make or break the product. They do it because they can. They have mastered everything else and still have capacity to spare. Whiskey or rum distillers may not follow the same procedures because they either do not encounter the same amounts of volatile components or they do not have the same degree of involvement.
**A gem is the comment “the purpose is not to make a table wine but to make the best possible raw materials to distill and produce a quality brandy.” Wines made to distill are different. It would be interesting to hear if and how grapes destined for distillation are treated differently in Vineyard management practices.
**Léauté points to a 1978 study by Onishi et al. that systematically tried using the Cognac method on numerous varietals found in California.
**He then points to another Guymon memorial lecture by Elie Skofis in 1983 that gives suggestions for making Cognac style brandies in the U.S. The tone of these papers is unique because they are intermediate as opposed to too advanced or too simple. They also make suggestions and give guidelines instead of just making cryptic observations using mass spec. or chromatography.
**Apparently Skofis’ paper gave recommendations for production practices. Léauté clarifies a few: “slight changes can be made: recommendation (4), no SO2 or no more than 20ppm to avoid having high quantities of acetaldehyde in brandy and recommendation (5), fermentation temperature between 68°F to 77°F. This is mainly done to reduce acetaldehyde and ethyl acetate by evaporation.
The very last comment strikes me as very interesting because in the book “Food Flavorings” by Joseph Merory a technique is mentioned for making fruit brandies where the unfermented juice is bolstered with spirits then distilled (unfermented!) to capture aroma, the then alcohol-free/aroma-free wash in then fermented to produce aroma for the next batch. Merory claimed that this was done to prevent aromas being lost with escaping CO2 during fermentation. Merory might never have used his technique and it might have just been a fun potential experiment. Léauté makes it seem like evaporation or compounds escaping with fermentation gases can benefit the spirit by removing a portion of the two most volatile components you want to significantly reduce anyway.
**As for aroma created in the still (besides furfural), Léauté says: “In addition, during distillation in alembic, the wine and the brouillis are cooked; many reactions occur between the compounds, and this phase generates delicate aromas.”
**Léauté mentions the use of “microdistillation” where glass lab-ware is used with copper shavings placed in the boiler to a give a glimpse of flaws that cannot be noticed by tasting the wine alone. He mentions it used to detect:
High acetaldehyde; too much ethyl acetate; acrolein; butyric smell; oxidization characteristics; high level of volatile phenolic compounds; and pollution by sulfury compounds, hydrocarbons, etc. So if a flawed 600 gallon batch of wine needs special treatment why not go into distilling it having an idea of what extra nasties you are going to encounter? I’m not aware if new, lower involvement American distillers are using microdistillation procedures to evaluate every new batch of distilling material. Most are understaffed and there is only 24 hours in the day.
**”Reaction between compounds during distillation: The first distillation last around 10 hours and the second distillation approximately 14 hours. When it is operating, many types of reactions occur between the compounds of mixtures which are boiling. The boiler can be compared to a reactor.”
“Regarding the future characteristics of the Cognac (or brandy), the reactions which occur during the first distillation are the most important. These reactions are functions of: the characteristics of the wine; the use of lees; pH and acidity; the size of the alembic; the temperature generated by the gas burner under the boiler; the duration of distillation; and the cleaning of the alembic. (Note: In addition, the wine extracts compounds from lees because of the heat. These components also can react with others during distillation.)”
pH might be a very important variable because it catalyzes reactions and could explain the importance of grapes high in total acidity, significance of the sour mash process, the use of sulfuric acid in rum production, or the freeze concentration of distilling material before distillation (to concentrate acidity!). Because the wine can extract a lot of components from the lees, some of which are negatives, they are often separated while they wait for distillation and then are re-mixed before they are distilled. Whiskey mashes are made every week so it doesn’t sit around but wine is made only once in the season so it can sit around for considerable time while it waits its turn in the still. A still can get pretty grimy. It makes me wonder if any laissez faire cleanliness can add complexity.
“The yeasts represent around 60% to 70% of the lees. Their use in distillation wines give more fatty esters (like ethyl caprylate, ethyl caprate, ethyl laurate, esters C14 to C18), more fatty acids, and nitrogren compounds (like amino acids). The fatty esters give fruitiness to the Cognac; the fatty acids give body and are like fixatives for many other aromatic components; amino-acids are involved in the thermic break down reactions.”
Many distillers use the term fruitiness which implies olfactory-sweet aromas but I suspect these compounds also stimulate the umami which a lot of researchers still do not acknowledge. The term “fixative” might not refer to any chemical reaction but something at the level of perception. For example in cocktail construction a simple daiquiri can be tart and limey but when the non aromatic sugar is swapped for an orange liqueur the result seems to conjure grapefruit. Compounds associated with the lees might be the orange liqueur in the example around which other more complex associations like grapefruit revolve.
“Types of reactions: The reactions are numerous: that is the reason that the double distillation technique in alembic is unique. Volatile components already in wine, may decrease or increase in concentration, depending on the types of reactions they are involved in. New volatile components can appear and generally are important for the aromas of Cognac.”
One thing that makes all of the reactions happen is the long time under heat that double distillation has relative to column distillation. Esters can also form differently in column distillation because fatty acids that could latch onto ethanol often latch onto another higher alcohol instead that has accumulated in the column. Some higher alcohol esters are seen as flaws and the phenomenon most significantly in continuous column distillation (as opposed to batch) because there is the opportunity for lots of higher alcohols to accumulate and congregate in one place on the various plates. One component type that decreases are fatty acids and one type that increases as esters as one turns into the other through esterification. Furfural also increases. Copper reactions also decrease sulfury components and some fatty acid components.
“Examples of reactions: Some reactions have been known for years, such as hydrolysis, esterification, acetalization, reactions with copper, and furfural production. Generally, the above produce, in relatively large quantities (more than 2 mg/L, constituents which are easily detected by gas chromatography. Other reactions produce, in a very small small quantities (less than 1 mg/L), constituents which are detected by glass capillary gas chromatogrpahy. During the last decade, many authors published articles about these reactions and the components they produced in spirits…”
“For instance, by hydrolysis, thermal break down and rearrangement may be generated: monoterpenes (linalool and alpha terpineol, <1 mg/L); ketones (alpha-ionone and beta-ionone, <0.01 mg/L); and others (vitispirane and T.D.N., < 0.1 mg/L).”
“Maillard reactions (reactions between a sugar and amino compounds) can also take place. The Maillard reaction is the main source of heterocyclic compounds such as furans, pyridines, and pyrazines…”
I think furans here refers to furfural.
**Léauté goes on to describe experimenting with Cognac production in California and how new varietals were explored. They used a 6.5 gallons baby alembic and found each varietal had to have its own cuts made to maximize its varietal character.
**Some California brandies are analyzed chemically and Léauté makes some interesting observations based on the numbers. Two examples have unusually high amounts of hexanol which might indicate they were crushed and de-stemmed at a too high a temperature. These are considerations that can be made probably only as involvement deepens. He notes that some of the brandies are higher in ethyl acetate than others, but below the threshold of perception. Apparently you want to be as close to line without going over. Seeing the numerical data for spirits so that it can be compared to that of successful products or other data such as threshold of perception helps distillers optimize their cuts.
One of the distillates is rich in Isoamyl acetate which contributes a banana smell. This ester of a higher alcohol might be the result of column distillation as opposed to alembic.
**Léauté recommended chilling the experimental California wines to thwart malolactic fermentation, but Cognac wines might go through malolactic fermentation as evidence by the ethyl lactate esters. His recommendation might have been made so the unique varietal character of the grapes could be explored. Malolactic fermentation produces generic aromas that though fun and potential “fixatives” for aromas, can rob a wine or spirit of its sense of place.