First a great thank you to Susan Coppin and the team of archivists at the University of Adelaide who made recovering these documents possible.
All these documents from Australia were contained in Series 600 of the Roseworthy Agricultural College archives.
This Study investigates the recycling of fractions during subsequent batch pot still distillations.
“Thus, addition of heads and tails to a wine charge does increase the size of the brandy heart, but only to a minor extent.”
“The heads and tails are then usually put aside and distilled at a later date for the purpose of alcohol recovery.” This line of thinking is ethanol-centric and concerns the yield. We will have to see if he makes any aroma-centric inquiries. My theory is that fractions are recycled to give aroma precursors more time under heat. The ultimate goal of fraction recycling is to improve aroma not yield.
“This practice is claimed to increase the quality of the Cognac Brandy, as well as increasing the size of the brandy heart.”
“The average for the last sixty years is 8.6% v/v alcohol.” This regards the alcohol content of Cognac wines for distillation.
“The years with the higher alcohol content were generally found to be of a lower quality. The wines also have a naturally high acid content.”
“Besides the improvement of quality claimed by the Cognac people, run-back of heads and tails will also greatly improve the efficiency of distillation, when the wines are of a relatively low alcohol strength.” When alcohol contents are low every percentage point of increase results in a dramatic increase in efficiency. The efficiency tapers off and the starting alcohol content approaches 10%.
“In Australia the base wines are not ‘cared for’ to anywhere near the extent as the base wines used in Cognac manufacture.” This is interesting because this paper is from 1975 and the Australian brandy industry should have had the benefit of lots of great research conducted at Roseworthy. Many of Australia’s producers are Roseworthy graduates.
“The Cognac people take special care to ensure the base wine is safe from oxidation, but at the same time free from SO2.”
“Also Australian brandy manufacture does not involve the addition of heads and tails back to the next wine charge.” This fact was pointed out by W.O. Graham in 1939 and apparently has persisted for many more decades.
“Australian base wines generally are greater than 10% v/v alcohol, and so, an increase in the alcoholic strength of that wine will not improve the efficiency of distillation to any great extent, as the relative increase in vapour strength will be slight.” If this fact influences practices distillers are thinking ethanol-centrically.
“The base wine used in Cognac manufacture is allowed to complete fermentation; is then racked off first lees; allowed to stand for 15 to 20 days to ensure completeness of fermentation, and is then distilled in contact with the full second lees.” I have not heard of this concept of first and second lees before.
“Also, ‘lees’ brandies have only a 40% variation in non-alcohol constituents, while the wine brandies have a 350% variation – i.e. approximately nine times as great.” I don’t completely know how to interpret this.
“Thus the presence of lees in the base wine appears to increase the proportion of non-alcohols, and to stabilize the composition. Both effects must have an important effect on quality. The increase in non-alcohols, provided they are of a desirable type, should increase quality.”
“The inclusion of lees is a regular practice in France, and so it is reasonable to assume that this practice improves the quality of the brandy.”
“Experiments carried out by T. Angove with reference to run-back of heads and tails to wine charges, show that this procedure causes the heads and tails product to pass more and completely towards the first and last stages of distillation.” I think this happens because increases in alcohol content further stratify congeners. This can be seen when distilling at higher proofs via varying the reflux on a column still. The bad stuff is very polarized in its volatility and the good stuff is luckily towards the center. Bad stuff can turn into good stuff and luckily through transformation under heat the new compounds end up appearing more towards the center of the run.
“No attempt in this experiment has been made to study the quality aspects of this modified distillery procedure.” Well that is disappointing.
Hickin conducted his experiment with a synthetic wine partly because no wines were available at the time of the experiments which had low enough SO2. It is important to remember that these are only student projects and have some limitations.
Compostion of the synthetic wine:
Ethanol …………………….. 10.1% v/v
Residual Sugar……………0.9 g/L
Total Acidity………………..4.8 g/L
Lactic Acid…………………0.25 g/L
Acetic Acid…………………0.3 g/L
Methyl Alcohol…………..0.2 g/L
n-Propyl Alcohol………. 5 ppm
iso-Propyl Alcohol……….120 ppm
iso-Butyl Alcohol………….50 ppm
iso-Amyl Alcohol………….300 ppm
Ethyl Acetate……………….75 ppm
Acetaldehyde………………50 ppm
pH…………………………..3.07 (final pH)
The pH was adjusted to greater than 3.0 by the addition of Potassium Hydroxide. Total volume of the synthetic wine was 100 litres.
This was a synthetic wine made without fruit aroma. It looks smartly put together and might be a great template for anyone that needs to construct a similar synthetic wine for experiments.
The paper concludes with the idea that recycling of fraction only slightly increases the size of the hearts fraction. He also mentions that the technique would “fall down” if the wines were of low quality and contained large amounts of SO2.
Nothing is in the bibliography that I haven’t already seen.
The most important thing to take away from this paper is how Australian brandy production hadn’t changed by 1975 even after all the great research down at Roseworthy in the 30’s, 40’s, and 50’s. Many industry people were Roseworthy grads so you think they would be aware of the projects that were done. Brandies were still made from sloppily cared for high alcohol wines and fractions weren’t recycled. Who knows why the inferior techniques persisted.