H.T. Davoren. 1955. The Effect of pH on Brandy Composition

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.  We should probably figure out how to digitize all of the papers.

Davoren, H.T. The Effect of pH on Brandy Composition. 1955. from Series 600 University of Adelaide Archives, Inventory Identifier 060000059 Box Number 2. [PDF]

This paper is concerned with ester production within the still. Cognac distilling material differs significantly from Australian distilling by pH and total acidity.  Acidity is a catalyst for esterification.  The author explores the correlation between ester production and pH.

“we can only rely on reduction of pH, after fermentation, if we wish to increase the ester content of our brandies.”  I suspect this will get them closer but not be equivalent.  The wines will still differ markedly by ester already present in the wines and the distribution of types of fatty acids (ester precursors).

“Two other factors which determine the composition of a brandy are the type of still and the method of distillation.”

“It is generally accepted (1) that only good quality brandy can be made with a pot still; 90% of French brandy is made with pot stills.” Some of the other Roseworthy papers elaborate this idea more.

“In the method of distillation the main consideration are:-

1. The strength at which the spirit is distilled.

2. The speed of distillation.

3. The distribution of impurities in the fractions.

4. The separation of the ‘heads’ and ‘tails’.”

The strength at which the spirit is distilled effects the distribution of impurities. What I hadn’t noticed before is how the recycling of fractions besides allowing for more time under heat for aroma precursors, also increases alcohol content by averaging it up and effects the distribution of congeners.

The speed of distillation also effects the distribution of impurities.  A slower distillation, which means more time under heat, allows for more aroma creation processes like esterification, but also is less challenging to the subtle reflux provided by the shape of the still head.  I originally suspected a minute amount of pressure could build up during a fast distilling thus slightly altering the distribution of the fractions but it turns out the reflux from the head of a pot still is more significant than I thought.

“Australian brandies approaching French style could probably be produced in dry wine areas, such as the Hunter River, but this would be uneconomical as there is a ready market for these wines.” Brandy production is most of the world is from areas where second tier grapes are grown.  There isn’t much need to make brandy if you are already getting great money for dry wines.  This economic look makes me wonder if brandy production could help jump start unique wine growing areas of the U.S. before global warming turns them into prime dry wine growing regions.

“I’ve heard that after World War 1 a firm was formed at Allandale, in the Hunter district, which made good French style brandies from local wine but, unfortunately, didn’t last for long.”

“In order to bring the acid content of Australian base wines to a level favouring maximum ester production it is advantageous to make acid additions to the wine, so bringing about an alteration in pH.”

“Tummel states the best way to reduce the pH is by means of sulphuric acid. He found that the spirit produced from wine in which the pH had been reduced by sulphuric gave a slightly higher ester content than that made from wine in which the pH had been reduced to the same level by tartaric acid, as well as the fact that sulphuric acid is more economical to buy than tartaric.”  Tummel’s paper is this collection.  He even does some cool regression analysis to look at the significance of the differences between sulphuric acid and tartaric acid.

“The effect of sulphuric acid on the copper of the still was also investigated by Tummel and he found that relatively no reaction takes place, and that wine treated with sulphuric causes less damage to the copper than that to which tartaric acid has been added.”  Damage to copper of extra acidified distilling material has been one of the things I haven’t been able to find much on.  My theory is that wooden boilers were favored in rum production where the distilling material is so acidified with sulphuric acid (in the dunder) that it would wear down a copper boiler quicker than is acceptable.

“2. Hydrometers.

There was no spirit safe supplied with the still so a means had to be devised for taking strength readings on the spirit as it left the condenser.  A number of glass bubbles were made which just floated in spirit of varying strengths, ranging from 40° O.P. to 100° U.P. (water).

The bubbles were placed in a separating funnel which was clamped under the spirit take off from the condenser, and the spirit level in the funnel was kept constant by means of the tap.”

What is being described here are called “spirit bubbles” or “philosophical bubbles” and were a very early form of hydrometry which predated the modern hydrometer which a floating scale. They are extremely rare and I actually acquired a complete set which I found in the UK. I had to pay $300 USD.  It is really exciting to seem them used in this scaled down experiment.

Davoren explores pH’s 2.5, 3.0, 3.5, 4.0, and 4.5 in his experiment. He raised or lowered the the original pH of 3.22 with calcium carbonate and sulphuric acid respectively.  “In each case the rates of addition were determined by trial before the bulk was treated.”

“After the calcium carbonate was added it was well stirred in and the calcium tartrate formed was allowed to precipitate over night.  The clear was then drawn off and checked for the correct pH before being stored in readiness for distillation.”  Separating precipitated tartrates might be useful in some of my experiments where I tried to make a brandy from vinegar tainted cider. Removing the tartrates might mean that acetic acid can be removed then alternate acids like tartaric can be added without being interfered with by the tartrates.

The experimental still had a frothing and puking problem and Davoren has to add some glass boiling stones.

The experimental still also uses a brandy ball which I have yet to find a diagram of.  I suspect it is just water run over the still head to create small amounts of extra reflux which out having to construct a typical column.

Some of the samples have to be distilled again due to puking.  I can’t figure out if Davoren has over filled his small still or if the change in pH has made some of the samples froth more.

“Both ester curves decrease slightly as the pH increases, whilst the decrease in each case between pH 2.5 and 3.0 is practically negligible.  It appears therefore that reducing the pH of the wine to 2.5 doesn’t case any further ester production than does reducing it to pH 3.0.”  This result makes me curious about rum production practices.

“The increases in aldehyde form the higher to the lower pH is considerable, but if the heads portion were removed, as is usual in commercial distillations, most of the aldehyde would be in these fractions.” Davorens experimental distillations were uncut.

“Conclusions:

1. [de]creased pH of the base wine does give an increase in ester formation, with the maximum pH for such increase being about pH 3.0, but this might vary if only the brandy fraction of the run is taken.

2. The lower the pH of the base wine the more aldehyde is formed, which would probably necessitate the running of more spirit into the ‘heads’ fraction when distilling low pH wines.

3. The results for the acid formation are too erratic to draw any worthwhile conclusions.  It should be a fact that the lower the pH the more acid formed but this doesn’t seem to be the case, in A curve and in B the curve reaches a peak at pH 3.0 but falls away again.”

Most of Davoren’s bibliography consists of the Roseworthy projects I’ve collected.

One cool thing he and other people list is “R.A.C. Distillation notes.” I wonder if it could be found in the archives.  A search through the archives for the Distillation Notes shows that Roseworthy was making its own brandy which was sold on campus tours.  It would be really cool to find more details about it.

This might be worth digitizing: Roseworthy Distillery Survey Account Book

W.R. Jamieson. 1950. Factors Affecting the Composition of French Style Brandies

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.  We should probably figure out how to digitize all of the papers.

Jamieson, W.R. Factors Affecting the Composition of French Style Brandies. 1950. from Series 600 University of Adelaide Archives, Inventory Identifier 060000038 Box Number 1. [PDF]

Jamieson probably wrote the most thorough paper about brandy production weighing in at 51 pages. I re-typed large swaths of the paper so that it would be better indexed by search engines.

“Generally, pressings, leachings and wine from grapes unsuitable for brandy production are distilled at high proof (160-190% pf.) and is used for fortifying sweet wine and brandy is distilled at 135 – 140% pf. from the wine of selected grapes.  The Australian Pure Foods Regulations specify that brandy must be the distillate from fresh fermented grapes.”

“… Some of these problems are bound up with the economics of production as the manufacture of cognac entails the use of equipment that is too slow and cumbersome for Australian methods of production.  Many of these problems have been studied at Roseworthy Agricultural College from the angle of producing brandies more closely resembling cognac and it is the purpose of this project to include a re-survey of the work accomplished.”  So if you can only read one Roseworthy paper, read this one!

“If we are to develop and expand our export markets we will have to modify our distillation procedure and methods of manufacture to comply with this existing demand.  South Africa our sister dominion, and river on the overseas market with wines and brandies, is making strenuous efforts to capture this market.”

“The Govt. Brandy Board which has to pass all wines before distillation has lately declared itself in favour of a Cognac type brandy for South Africa.  This will mean the exclusion of the two most prolific bearers of grapes, and from the varieties specified as being suitable for distillation for the production of beverage brandies.”  It is really interesting how this stuff is regulated.

“In the eusuing [typo? ensuing?] controversy Professor C.J. Theron and Dr. C.J.G. Neehaus of the Shellenbosh-Elsenburg College of Agriculture in supporting the Govt. Brandy Board’s as to the necessity for conforming to this demand concisely summed up the situation thus.

(a) There is a great demand for certain types of South Africa brandies overseas and these resemble Cognacs. South Africa is in need of this demand and should foster it.

(b) Cognac type of brandy derives most benefit from maturation and the future of the South African wine industry lies in the production of well matured brandies. (4)”

Interesting names are introduced here and a new University to look into. No doubt these players carried out similar research to Roseworthy that we can probably track down.

“A French decree (May 16th 1936) limits the varieties which may be grown in the Charente for Cognac and these are Saint Emilion, Colombard, Folle blanche, Blanc romay, Montellis White Suavignon and Jurnac blanc. (13).. The first three varieties are the main ones and the Folle blanc which is considered the best for Cognac often attains 1.2% acid and only 7-8% alcohol by volume. Saint Emillion generally 709% alcohol by volume and Colombard 8-11%. (3)”

“In some years, during the harvesting period, many of the grapes are damaged by rain and mould and such damaged bunches are scrupulously rejected.  The grapes are crushed on the day they are picked and the juice separated from the skins immediately. Fermentation of the free run juice is carried out in small, closed containers (up to 500 gals capacity).”

“No S.O.2 is used during fermentation as it is found that any wine fermented in the presence of considerable quantities of S.O.2 will contain a considerable quantity of aldehydes, even though the wine iteself may have only negligible S.O.2 content at the time of distillation.  This is due to the formation of an aldehyde bi sulphite complex. The quantities of S.O.2 used to prevent distillation wines from becoming diseased will always result in too much aldehyde production. (4)”

“Fermentation is carried out at low temperature and the ‘silent’ fermentation takes about 3-4 weeks, the wine then containing about 8% alcohol by volume and up to 12 gms/litre of acid as tartaric. (13)”

“When the wine has fermented out dry it is left on lees but distilled as soon as possible to reduce risk of wine spoilage. Wines left too long on gross lees develop a typical stale lees flavour which may be imparted to the spirit. If the wine is racked from its lees the quality of the brandy suffers as distillation of the wines with large numbers of yeast cells is one of the essentials for imparting the Cognac character. (4) Just before charging the still wine and lees are agitated to give a uniform suspension.”

“The procedure is not in any way standardized and distillation practices are passed on from father to son.  The distiller is called upon to show great judgement in the selection of wines for Cognac; and in deciding when to take off ‘heads’ and ‘tails’ from the wines made from the different varieties and grown in different areas.  As the pot stills are direct fired great care must be taken in controlling the heat of the fire to avoid scorching of the contents.”

“The wine is fed into the cold still, the fire lit and distillation carried out at a very slow rate.  It is essential that the pot be never any more than 75% filled with wine.”

“To minimize risk of spoilage the whole of the distillation wine for the season is sometimes put through as low wines before commencing the redistillings. The best brandy, however, is obtained by redistilling immediately and where there is only a single still in operation this is done when three charges of low wines have been collected, and the joint distillate is then redistilled. (4)  The citation here is for the South African paper I haven’t yet come across and this information on not waiting to re-distill is something I’ve never seen before.  I suspect the differences before waiting or not is due to the distillate approaching equilibrium.  The fractions will be different due to the spirit evolving in terms of equilibriums like those of ethyl-acetate and acetaldehyde.  Apparently the most extraordinary results are obtained when distilling as close to the previous distillation as possible.  What I wonder is if a reference to this ideas can be found in whiskey or rum distillation. 

“Sometimes the ‘tails’ are fractioned into a portion running from 50 – 20% alcohol by volume and this is mixed with the ‘broullis’ and the portion running from 20 – 0% alcohol by volume is mixed with the distillation wine.”  This is interesting. I wonder if the very last fraction here contains any compounds related to “Cognac oil” that is supposedly produced by steam distilling the remnants.  This fraction could also be higher in fatty acids which might benefit form the longer time under heat and the acids catalysts of the first distillation rather than the second.  I haven’t seen this advice anywhere else.  If this advice is also South African they must have produced some really interesting literature.

“Brandy distilled thus is totally unsuitable for immediate consumption while young, but has to mature for a number of years whereby its secondary constituents interact to remove the disagreeable, burning taste and to impart mellowness and palatability. This maturation can only take place where the wood of the container can contribute certain qualities to the brandy.”  The wood ends up contributing a lot of acidity which influences the various equilibriums.

“The calcareous soils of the Charente are said to impart a delicate and characteristic bouquet to the Cognac. The exact explanation of why these soils give the grapes their desirable characteristics is not known but in the wine the delicate bouquet may be due to a pH effect.” I suspect the way the soil and climate stress the vines produces an abundance of diverse fatty acids while having a very high total acidity and low alcohol.  Low alcohol creates a high ratio of aroma to alcohol as well as being correlated to high TA. 

“Jocelyn and Amerine (1) suggest that red grapes contain larger amounts of the undesirable substances and if fermented on skins greater quantities of pigments and tannins are extracted. Possibly these substances are hydrolysed. The above workers also consider that the bloom of the grapes on hydrolysis yields a variety of fatty acids and other hydrocarbons and thus fermentation on skins of both red and white varieties will produce more of the hydrolytic products.  More likely, as pointed out by Kuchel (12), contain a greater quantity of volatile constituents in the skin.” I don’t completely understand what he means by bloom here unless it simply is the skins.  When you’d think you don’t really need to worry about compounds that aren’t volatile i.e. tannins or pectin the chemistry always gets a little deeper and what you thought wouldn’t be volatile gets subdivided into parts which may be volatile.  Pectin gets hydrolized into methanol which needs to be looked out for.  Amerine references this “bloom” on page 16 of Commercial Production of Brandies and has a better citation for Theron’s South African literature on the bottom of page 17. “Theron, D. de Wet. South African brandy. Wine and Spirit 11(97):4399, 4401. 1939.”

“Varietal aromas have a great influence on the character o brandies and this is generally considered undesirable in better class brandies.” This is a really interesting statement.  In whiskeys we look for the character of specific grains but not in grapes?  But this statement might just refer to varietals that have a foxy character like those of vitis lambrusco or some of the muscats.

“Grapes with a high sugar content are to be avoided for the production of quality brandy. Of two wines with the same percentage composition of volatile constituents, the wine with the lower alcohol content will yield a brandy having a greater percentage of volatile constituents if both are distilled at the same proof. (1). The ratios of aroma to alcohol.  The mosto-verde technique used in Peru is a way to skew it further.

“This may be due to the fact that the weaker the alcoholic solution the higher the temperature at which is boils and the more of the less volatile constituents pass over in the vapour.  If the wine is of comparatively high alcoholic strength the higher boiling point substances remain behind in the pot.” Here Jamieson gets a little confusing with his speculation.  The strength of the alcoholic solution in the pot is also effected by run-back which is the recycling of previous fractions.  Higher proof distilling material produces higher proof distillates and as proof increases congeners get more bunched up and less evenly distributed.  This make the cuts more of an all or none proposition.  What people didn’t understand back then was that aroma precursors would change significantly as ripening happened.  Grapes in cooler climates keep more noble fatty acids as they ripen relative to warm climates.

“The grapes that are high in total acids are superior to those containing lesser amounts. They should be picked when mature – fully ripe or over ripe grapes do not give the same quality brandy.  Wines low in total acids and high in pH will give less aroma and have a more undesirable aroma, if distilled at the same proof, than those brandies made from wines high in total acid and low in pH.  Here “mature” needs to be elaborated. It could probably be stated as the point when favorable aroma precursors are at their maximum. This will be at a point when total acidity is still very high and potential alcohol is not maximized.

“The subsequent wine made form grapes with the desirable features will be thin and very acid with no special qualities.”  It takes a lot of foresight to wrap hour head around this.

“The grapes are fermented “off skins” either by medium of a foredrainer or by fitting a false bottom for immediate drain off. It is imperative that no S.O.2 be added and should only be used as a last resource and then the wine should be distilled at high proof and not used in the production of beverage brandy.  Mouldy grapes will impart their taint to the wine and thus to the spirit.  Where S.O.2 is used the risk of mercaptan formation is veyr great and apart from the danger of these evil smelling compounds being produced, the aldehydes formed during fermentation are fixed in the wine by the sulphur and released during distillation increasing the aldehyde content of the spirit.”

“Wines fermented at high temperatures show less retention of the more desirable volatile products and in addition may give a taint to the spirit. (1) Under Australian conditions where the grapes arrive at the crusher hot and are fermented in large vats it is impossible to keep the temperature down to a reasonable degree without the use of coolers, particularly if no S.O.2 is used.”

“In order to bring the acid content of the wine to a level favouring maximum ester production it is advantageous to make acid additions to the wine prior to distillation.” I think this advice comes only from the other Roseworthy projects.

“It was also found that by putting through the distillation wine as a low wine and incorporating the ‘heads’ and ‘tails’ from the brandy run into the next low wine charge caused an increase in esters. This was particularly noticeable at pH 3. Acid catalyzed esterification and the recycling of aroma precursors.

Jamieson goes on to summarize more of the Roseworthy projects and explains in some circumstances the conflicting results.  He spends a nice amount of time summarizing the sodium flouride as a sulphur alternative project done by Shipster which was a paper I didn’t request from the archives.

“Comparisons of brandies from the different stills are practically meaningless as methods of distillation and wine type used are not known when the finished brandy is presented from analysis at the laboratory.”

“Graham pointed out that slow distillation gives a more selective separation of the secondary constituents their distribution being governed by (a) their respective volatilities, (b) their respective miscibilities in water/alcohol mixtures of different strengths. Also that slow distillation accounts for the nature or composition of these secondary constituents as well as their amounts.” Graham ends up demonstrating how a slower distillation and thus a longer time under heat produces more extraordinary results.

Jamieson’s table 5 reproduction of Grahams work is a must see.  I first heard of Graham’s work through Amerine and then finally inter library loaned the summary of his thesis from the Australian Brewing Journal.  I was really motivated to track down the original thesis to see if there was any great data to look at.  It is really a great work to help out beginning distillers.

“If early heads are undesirable in brandy and later heads desirable then the effect of lees is to give a clearer and cleaner separation between the two heads thus more of the heads could be included in the brandy.

The effect of lees summed up by Angove is to cause a marked increase in the ester and acid content of the low wines, and, in the brandy run, a stronger tendency for these constituents to pass into the heads.”

“In his literature review Angove (7) outlines the following procedures that may take place.

(a) The heads and tails may be run back to the next wine charge.

(b) The heads returned to the next brouillis charge and the tails to the next wine charge, or,

(c) High strength tails may be divided into two, the highest strength portion going to the next brouillis charge and the lower strength going to the wine charge; finally,

(d) The heads and tails may be bulked and redistilled and the heads and tails from this going back to the wine charge.” Apparently there are a lot of options and we should probably evaluate each option in relation to recycling aroma precursors, differences in time under heat, and availability of an acid catalyst.  I suspect some options might maximize ester content while others not.  You probably do not always want to maximize ester content.  Probably only from the greatest source material where the highest amount of noble precursors are found.

“Aldehydes. Heath (22) found that there was a slight cleansing of all fraction down to brandy due to the effect of run back and that the extra aldehyde tended to collect in the tails.

This is contrary to the Angove’s results where it was found that aldehydes accumulated in the heads and this was accentuated by run back.

Tails were almost free of aldehyde and they were not effected by run back.” So there is some disagreement here. I suspect we can look to Robert Léauté’s James Guymon lecture for the definitive explanation.

“The chemical changes are due to oxidation alcoholysis and esterification. Bellet (26) found that the total ester content remained essentially constant but the more volatile esters rose very slowly at the expense of the less volatile esters of the higher alcohols.  The consequent liberation of higher alcohols is termed ‘alcoholysis’. Some of the higher alcohols released are converted to aldehydes. The secondary importance of oxidation, and the relatively greater importance of alcoholysis gives reasons why the rapid oxidation of new brandies by the introduction of oxygen or ozone under pressure has not been successful.” This is all in regards to maturation.

Here Jamieson quotes a very large passage of Amerine:

“…The proportions of the various higher alcohols present in brandy is not constant due to differences in the composition of the raw material, to the use of various types of yeasts and of degrees of purity of the strain, to the extremely variable fermentation conditions, to the methods of distillation and to various other factors. As far as brandy is concerned, comparative analysis of spirits produced from raw materials of known composition, with a uniform method of fermentation and distillation would do much to elucidate the problem of the relative proportions of the higher alcohols present, and the factors which influence their formation.

Yeasts will preferentially assimilate inorganic nitrogen compounds such as ammonium phosphate and ammonium sulphate and the production of higher alcohols is reduced” [end Amerine]

“The addition of an organic source of nitrogen should give a heavier bodied brandy.”

“The tails or aftershots contain the major portion of the higher alcohols and consequently they will come over towards the end of distillation.

Iso propyl alcohol and tertiary butyl alcohol are readily soluble in ethyl alcohol and will come over during the brandy run. In a very weak alcoholic solution some of the higher boiling point higher alcohols will also tend to come over early because they are relatively insoluble in water compared to ethyl alcohol and do not suffer a reduction of vapour tension due to water admixture as does alcohol.” Amerine explains some of this well as does Robert Léauté

“The secondary constituents in brandy are never objectionable when in a pure state but their reactions with acids constitutes esters of flavouring substances which add considerably to the fullness and aroma of brandy.” I don’t really understand the logic of this statement.  So higher alcohols aren’t objectionable when alone nor are they objectionable when they form esters because they contribute to “fullness” so don’t fear higher alcohols?  I do remember reading that column stills have a tendency to produce more esters of higher alcohols of which some are considered big flaws.  One higher alcohol ester associated with column still brandy production has a highly attention, plebeian, and ordinary aroma of bananas.

Jamieson finally starts his experiment on page 41.

“By the addition of inorganic and organic sources of nitrogen to the must before fermentation it was hoped to ascertain the effect on the composition of the resultant distillate.” Interesting!

“Amounts of ammonium phosphate, ammonium sulphate and peptone containing the same percentage of nitrogen were added to the grape juice and this was seeded with 2% yeast culture and allowed to ferment.”

Jamieson has a simple table that displays his results.

“There appears to be no significant difference between the fermentation rates but this may be due to the fact that they were all fermented at low temperatures. Perhaps ammonium sulphate gave a slightly more efficient alcohol production pH.”

“Ammonium sulphate gave a big reduction in pH, while peptone raised the pH slightly above the control.  Ammonium sulphate is the salt of a weak base and a strong acid and on hydrolysis there would be a slight reversion to the strong acid thus lowering pH.  Peptone on being decomposed by the yeast would yield amino acids and finally higher alcohols and ammonia.  Ammonia on being released would raise the pH slightly.”

“Peptone has given a decided increase in ester content in the wine over the controls. Throughout the whole series where there has been a rise in the volatile acid content, there has also been in a rise in the ester content.”  This regards the wines but who knows if these were noble esters or not. Maybe Jamieson will provide organoleptic analysis.

Jamieson goes on to detail some of the limitations of his distillation apparatus that might skew the results.

“Discussion.

Alcohol – There are considerable differences in the strength of alcohol which is not entirely due to the original strength of the wine. Probably rate of distillation played some part in the variance of the strength of the distillate.

Titratable Acidity – This represents volatile acidity for the most part as there would be little or no entrainment of fixed acid when using a rectifying column.  There appears to be a decrease in volatile acids in all samples when compared with the controls – the wines fermented with ammonium phosphate giving the least volatile acidity.

Esters – There is no significant difference in the ester content of any of the distillates. This is rather surprising in view of the increased ester content of some of the samples of wine, particularly those fermented with ammonium phosphate.

Aldehydes – Again no significant differences except perhaps those fermented on less (see later)

Higher Alcohols – Not determined as method unsatisfactory.”

Now Jamieson goes on to analyze everything in regards to lees distillation:

“Distillation On Lees – Represented by C – the third jar in the triplicate of each experiment.

Titratable Acidity – No significant differences. With the exception of the control those distilled on lees may have given slightly less volatile acidity than those distilled with wine only.

Esters – No significant differences.

Aldehydes – With the exception of the control all wines distilled on lees gave a considerably lower aldehyde content than those distilled with wine only.

DIFFERENCE DUE TO ESTER CONTENT IN THE WINE AND IN THE DISTILLATE.

It is difficult to give a reasonable explanation for this difference. A possibility may be that the esters were high boiling point esters which would come over in the ordinary distillation apparatus fitting with a splash head used in the analysis of ester content of the wines, but with a still fitted with a reflux column would remain behind in the DISTILLATE.” I capitalized this last term because it is a typo and crossed out in the text but not corrected. I think he means left in the pot. Jamieson is getting into the deeper end of chemistry and analysis here and I don’t really know how to clarify anything.  Not all esters are created equal and some are noble and some are not.  Back in the day their analysis was a lot more simplified and they didn’t have the ability to sub divide esters into the specific types.  

Jamieson mentions an appendix to the project where he will discuss more results but it isn’t included in the PDF.  Jamieson had problems with his higher alcohol analysis which really limited his work. It would be really fun to perform some of these very basic experiments again with modern analysis to help beginning distillers.

Unique references from the bibliography:

“4. C.J. Theron & C.J.G. Niehaus “Wine-making” Farmers’ Bulletin, Series No.130.”

“6. F.C. Lloyd “The art & technique of wine””

“13. R.A.C. Distillation Notes”

“17. Francois De Castella. “The Grapes of South Australia Reports to the Phylloxera Board.”

P. LeH. Tummel. 1948. Acidity Modifies Brandy Composition

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.  We should probably figure out how to digitize all of the papers.

Tummel, P. LeH. Acidity Modifies Brandy Composition. 1948. from Series 600 University of Adelaide Archives, Inventory Identifier 060000025 Box Number 1. [PDF]

“Synopsis :-

1. By reducing pH of base wine the ester content of brandy is increased.

2. Returning ‘heads’ and ‘tails’ from the brandy run to the next low wine charge causes an increase in esters, especially at pH 3.

3. Reducing the pH with sulphuric acids, besides being more economical, gives a higher ester content than tartaric acid, and at the required strength has no adverse effect on copper plate.”

“The purpose of my project is to show that by reducing the pH of brandy base wine results in an increase in esters, which are essential component of good brandy.”

“Our climatic conditions do not lead to high acid wines as in France, and thus we can only rely on reduction of pH, after fermentation, if we wish to increase the ester content of our brandies.”

“It is noticeable that the three main varieties are white, which are considered to be superior to red owing to less oils contained in skins and stems.”

“3. Sulphuric Acid:

Has been found preferable to use sulphuric acid in lieu of tartaric, not only for economy, from (VI) price of H2SO4 3d, a lb. against 4/6d. a lb. for tartaric, but also because it gives superior results.

H2SO4 has a lower pKa value than tartaric acid.  [omitting small chart showing pKa values]

H2SO4 being more highly ionised will react with the potash neutralizing the tartaric acid, forming K2SO4 and releasing tartaric acid.

[omitting some simple formulas that are hard to re-type]

Thus reducing the pH with H2SO4 increases the content o tartaric acid.”

“Expressing results statistically confirms the hypothesis that the lower values of pH give more esters, as under.  Although a significant difference between the two acids, statistically it may be due to chance.”

Tummel goes on to calculate the statistical significance of his results, but it should be noted his sample size is really small.

“The S.S. due to pH can be further portioned into a linear component and a quadratic component by means of orthogonal polynomials.”

Quite the over achiever.  You do not see much of this math in early experiments. I think Maynard Amerine was also big pioneer of adding statistical analysis to his experiments.

“Part III.

Distillers may be dubious of the value of sulphuric acid for fear of its action on the still.

Following experiments proves H2SO4 may be used safely at the required strength.”

“From the above results, H2SO4 has less adverse effect on Cu, than Tartaric.” I don’t think you can draw much conclusions from so brief an experiment but experiments could definitely be performed. I suspect wooden boilers were used in the past for highly acidified mashes.

“Referring to table of analysis, page 7, reduction of the pH of brandy base wine has no significant effect on secondary constituents, other than esters, thus after part one, only analysis of esters was carried out.”

“The behavior of the ester content in the distilled spirits shows that as the concentration in the wash increases, the tendency is for a marked increase in the resultant heads, and to a lesser degree an increase in the brandy run, whilst the esters in the tails diminish or remain steady.”

“Although H2SO4 has been termed the “acid find” for reducing the pH of brandy base wine, it is here alone useful. H2SO4 could not be applied to marketable wine for the same purpose, as the legal limit of sulphate in wine is 2 grams per litre expressed as K2SO4.”

There is organoleptic analysis in the appendix mostly in the form of an inarticulate chart so I’m not sure how to interpret it.  I think some tasters preferred the non-sulphuric acidified brandy to the tartaric.  The experiments are unfortunately over simplified because they do not look at the distribution and variety of the fatty acid ester precursors.

Nothing unique was in Tummel’s bibliography.

J.R. Walters. 1947. The effect of the tartaric acid content of wine on the composition of distillates

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.  We should probably figure out how to digitize all of the papers.

Walters, J.R. The effect of the tartaric acid content of wine on the composition of distillates. 1947. from Series 600 University of Adelaide Archives, Inventory Identifier 060000021 Box Number 1. [PDF]

The Series 600 index does contain a typo. The study is about tartaric acid and not lactic acid.

This is another study pertaining to the old adage that high acids wines make the best distillation material.

“However, little is known of the effect of the composition of the base wine on the distillate.”

“This acid [tartaric] is the characteristic acid of the grape and is predominant in over-ripeness, being present as bitartrate and tartrate salts which are precipitated to a considerable extent during fermentation. It is a usual addition in the acid form during vintage operation and, when this is practiced it represents a considerable portion of the acid in the finished wine.”

“In literature dealing with the production of cognac, the fact that wines are always of high acidity is stressed.  In under-ripe grapes malic acid would be predominant but this would not be so under Australian conditions where grapes for distillation are usually picked at extreme ripeness.”

“Renee and Jean Lafon (6) state that tartrates in solution with wine distilled on lees react with alcohols giving esters.”

“Aldehyde is an undesirable impurity in brandy in large amounts and its elimination or production in small quantities is important in the distillation of high quality pot brandies.”  Walters references Angove that distillation on lees produces less aldehyde.

“Esters are said to be produced to a limited extent during distillation. They are the important flavouring constituents of brandy and their formation appears to be related to acid content. The bearing of tartaric acid content on the amounts of these constituents present in the distillates is the object of this experiment, the theory being that a higher ester and low aldehyde content would result.”

“Figures show a slightly lower alcohol content in wines fermented at the low pH which may be attributed to the inhibiting effect on the yeast. This also accounts for the high residual sugar and differences in volatile acidity.”  Inefficient fermentation might create different degrees of the “mosto-verde effect” where skewed ratios of aroma to alcohol are created.

“Considerably higher values in acids in AI and AII are due both to higher volatile acid produced during fermentation and to carrying over of some non-volatile acids during distillation.”  Here is where the study might have a problem.  No non-volatile acids should come over unless he is running the still incorrectly.  Because some of these students used small stills that were too full they had problems with “puking” where non-volatile material bubbles over into the condenser. Maybe Walters will give more hints later on.

“It is probably that there is a slightly lower production of aldehyde during fermentation in an acid medium. Acetaldehyde is a normal product of fermentation in small amounts. In the final stages of fermentation it is said to be converted to alcohol by reduction due to enzyme action. The change in pH would effect the activity of the enzyme and hence the products of fermentation.” I have not heard of this enzyme idea but it is really interesting.

“In the first distillation to low wines some tartaric acid could be carried over during the boiling and in view of Angove’s work (1) it appears that the process of distillation itself has an effect on aldehyde production which varies with different concentration of tartaric acid or tartrates in the wines.”  I think that tartaric acid could be carried over is only a hypothesis and the way it is stated doesn’t necessarily mean that Angove had any similar hypothesis.  Tartaric acid to the best of my knowledge is not volatile in the context of beverage distillation. Unless the still is operated incorrectly such as filled too high there should be no tartaric acid in the distillate.

“A lower ester formation from the more acid material is shown which is contrary to what would be expected and is difficult to account for. It is quite evident that this acid has no importance in regard t increasing ester production.” Other studies found sulfuric acid to be a better catalyst for esterification than tartaric. I’m not sure what happened here.

Walters proposes experiments that link acid content of the wine to aldehyde content. He states that if aldehyde content could be reduced in the wine a smaller heads cut could be made therefore increasing economy. He runs out of time to conduct any further experiments.

The paper is fairly short but has a large appendix of his methodologies.

R.T. Heath. 1941. The effect of certain distillation procedures on the brandy composition.

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.  We should probably figure out how to digitize all of the papers.

Heath, R.T. The effect of certain distillation procedures on the brandy composition. 1941. from Series 600 University of Adelaide Archives, Inventory Identifier 060000012 Box Number 1. [PDF]

“The object of this paper is to see:

1. What effect reflux, as governed by the length of the column has on the resultant brandy fractions, and comparing with reflux obtained by the use of the brandy ball: and to establish:

II. A recheck on the run-back of heads and tails to the next wine charge, as it is still in doubt whether the final brandy is cleaner and or a longer cut in the brandy-run is obtained under this method.”

All of these simple experiments probably need re-performed in conjunction with modern analysis that can sub-divide the congener groups like esters, aldehydes, volatile acids, and higher alcohols.

“A still constructed by Pontifex and Wood similar to the brandy-ball effect, where the whole column up to the bend is cooled by water overflowing from the top tray to one immediately below, and so on down the column — the cooler water therefore being at the top, this being only one of the many types of stills used.” This might be a description of an experimental still used in Armagnac production. I think that Pontifex and Wood were equipment designers.

“and according to Rene et Jean Lafou (16) all heads and tails are run-back to the next wine charge, whereas others state that only part of the feints are returned; some to the brouillis charge, some to the next wine charge, while proportions may be discarded altogether.”

“The tails are sometimes separated into two portions; the first fraction down to 20 percent A.A. returned to the next brouillis, while the second fraction from 20 percent to 0 percent is returned to the next wine charge.”  If this is practiced I suspect the congeners of the second part of the tails will benefit from a longer time under heat and the total acidity of the wine charge to catalyze esterification.  Eventually a tails fraction has to be thrown away because otherwise you could not get rid of accumulated furfural.

“Plan of Experiment.

A study of the resultant brandy fractions after–

(a) Lengthening the column, by raising the arm in upward slope to the condenser.

(b) Using a cool brandy-ball, without lengthening column.

(c) Comparisons of the above made against fractions obtained without the use of either (a) or (b)”

“the Table shows a definite decrease in the acid and ester content both by the Lengthened column and brandy-ball whereas the other constituents remain more or less constant, except perhaps a descrease in secondary alcohols obtained by means of the lengthened column.

Therefore, from the low-wines produced similar effect would be expected to occur in the same constituents in the brandy-fractions, and such is the case.”

Heath goes on to discuss all the congener categories separately.

From his organoleptic analysis, Heath suspects that “the higher alcohols have a very marked effect on the bouquet, more so than esters.”

Heath concludes that lengthening the column is more efficient than employing a brandy-ball.

Next Heath re-explores run-back to verify Angove and Graham’s results.  The recycling of fractions was for some reason barely practiced in Australian brandy making.

[in regards to volatile acids] “it appears that with the use of the feints an equilibrium is established in this constituent which distills over unchanged throughout progressive distillations.”

“As for the other constituents, the esters appear to gradually increase throughout subsequent distillations, while aldehydes decrease slightly. Secondary alcohols and Furfural, however, have undergone little or no change whatever with the use of the feints.”

“Esters: Here it is interesting to note that although the low wines gradually increase in ester content, produced by the effect of run-back, this increase is not uniformly distributed among the brandy fractions, but in each case more are pushed into 1st. heads and 2nd tails, leaving the fractions 2nd heads, brandy and 1st tails uniform within themselves.”

“The course taken by the esters is to concentrate in heads and tails with decreasing amounts in towards brandy.”

“Results obtained in the above experiment also show that feints play an important part. It does not necessarily mean that by introducing the dirty or undesirable fraction of the brandy-run to the following brandy charge a corresponding dirtier spirit will result; but on the contrary, it cleanses all fractions of their respective constituents except perhaps esters which tend to increase gradually-this being an advantage to Australian brandies as they are generally low in ester content, as compared with French standards. Consequently, by utilizing the feints it is evident that a longer run on brandy could be obtained than otherwise.”  So it can be said that recycling fractions increases the size of the hearts fraction while at the same time it recycles fatty acids which gives more opportunity to produce esters.

Unique entries in the bibliography:

“2. Nettleton, J.A. “Manufacture of Spirit”. 123-150.”

This text has a few editions with the earliest being 1893. Sadly it hasn’t been digitized by google yet or republished and used copies are astoundingly expensive.  Ian Buxton, the rare book collector/re-publisher made a limited edition high end reproduction of the text. I bought one and he has a few left for about $150USD.

Apparently the wisdom of this book plays a small part in the birth of Japanese Single Malts.  The young Japanese chemist Masataka Taketsuru had tracked down the author with discouraging results when he visited Scotland in 1919.

Apparently Masataka returned to Japan with a Scottish wife.  It is a really wonderful story.

W.O. Graham. 1939. A comparison of the composition of successive fractions obtained during distillation and their relation to the composition of commercial brandies.

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.  We should probably figure out how to digitize all of the papers.

W.O. Graham. A comparison of the composition of successive fractions obtained during distillation and their relation to the composition of commercial brandies. 1939. from Series 600 University of Adelaide Archives, Inventory Identifier 060000006 Box Number 1. [PDF]

This is Graham’s original thesis whose summary was published in an Australian Brewing Journal as part of the Karl Weiderhofer prize.  Maynard Amerine included the journal article in his seminal look at brandy making, Commercial Production of Brandies, from 1941.  For some reason the original thesis was never collected by Amerine nor other important papers that I’m republishing in this series.  They might have been lost due to the war.

People can download the original paper for themselves but I’m going to re-type some choice quotes so they are better indexed by search engines.

“Various modification in the operation of the still and in the separation of the ‘spirit’ running are adopted commercially in Australia, but there are no recognized standards for the distiller to work upon. The rate of distillation is of prime importance, and a section of this paper is devoted to the study of it and its effects on the distribution of impurities in the fractions of the distillate.”

“Much importance has been attached to the ester content by some countries importing Australian brandy, and methods of increasing the amount of esters have been attempted by some distillers even as far as allowing the wine to become slightly ‘pricked’ to raise its volatile acidity before distillation. The volatile acidity of a wine was thought to have considerable influence on its ester development, and experiments were carried out to verify this. The ester content of a brandy is subject also to changes during storage, and changes during storage in ester content of freshly-distilled spirit were studied.”

What they might have found out is that not all esters are desirable esters.  You want only so many esters of acetic acid. You want to have a base wine that is higher in other kinds of fatty acids to develop more ester diversity.

“At the present time there appears neither any relation between quality and composition, nor any methods of securing a spirit of desired composition (at least with a pot still) and it was for these reasons mainly that this subject was undertaken for investigation.”

“Vizetell – (1) says that the nearer brandies are distilled to their drinkable degree, the more perfect are their vinous flavour and aroma, and the more distinguishable their taste and smell.”

“Distillation at a low strength may be quite satisfactory for clean sound wines, but those unsound or of poor quality should be distilled at a higher strength to eliminate undesirable impurities and off-flavours.”

“Rate of Distillation.

Young (3) slow and regular distillation will give a more selective separation of impurities. Different rates of distillation will give different distribution of impurities in the distillate. Elliot (2) In brandy-making in France the distillation of the spirit fraction which amounts to 80-85 gallons for a still holding about 220 gallons, occupies from 10 to 11 hours, while the distillation occupies from 16-18 hours. This is a very slow rate of distillation. Schidrowitz (4) By vigorous distillation certain impurities as furfural may be formed.”

A bunch of new names here. I only recognize Young.

“The distribution of impurities in the fractions of the distillate.

It is well-known fact that in distillation, those substances with a higher vapour pressure (i.e. lower boiling point) will tend to distill over first. Consequently the more volatile substances as aldehydes will accumulate in the foreshots to a greater extent, and the slower the distillation the more marked should this separation be – Young (3). Young (3) The distribution of the impurities is, however also affected by their relative miscibility with the alcohol-water mixture.  The rectifying action of the neck of the still will cause differences in the distribution also, and the longer the neck the greater will be the degree of victification and the more marked should be the separation of various constituents.

G. Buttner and A. Miermeister (5) studied the course of distillation and found that acetaldehyde distills early, furfuraldehyde at the middle of the run, while esters and higher alcohols distill more or less regularly and no appreciable partition is effected….”

A better explanation of this can be found in Roberte Léauté’s 1989 James Guymon lecture.

“…L.W. Cornell and R.E. Montanna (6) showed that acetic acid (principle volatile acid in wine) distilled more or less regularly from start to finish.”

Again, more great names that I haven’t come across before.

“The chief chemical changes (14) consist of an increased aldehyde, acid (both fixed and volatile) and ester content, the latter being formed by the esterification of the alcohols and acids present, this change being subject to an equilibrium constant which is only obtained after long periods at ordinary temperatures, and occurs when two thirds of the equilibrium mixture is esterified.  Whatever the modifications in composition of the brandy occurring during maturation, there must be in the newly distilled spirit some optimum amount of impurities which will give a final product of highest quality for the type of wine from which it was distilled.”

So what we are dealing with is a moving target. A spirit straight of the still may not be instantly enjoyable so we have to know how it will evolve so that it can have the right starting point.  I suspect many white dogs sold to be drunk immediately are not exactly the same as what is worth putting into barrels, or they are held to come to equilibrium.

“A considerable amount of work has been done on the ‘judgement’ of spirits. Most authors state that spirits cannot be judged on results of analyses alone, but by combining analyses with testing. Hehner (7) Analyst – 1905 – says that the quality of brandy cannot be judged by the amount of impurities present, and also that esters fluctuate as widely as other impurities. He says that too much importance is attached to the ester content.  Quoting Nessler and Barth 1883, he says that the noses and palate of a brandy are better reagents for quality and purity than are chemical means.  This was also recommended by Fresenius 1890, Sell 1892, Bersch 1895, and Koenig 1904. (Analyst 1905) (7).  Hehner says that, taking all circumstances into consideration, it follows that the amount of impurities (coefficient of impurities) is largely an accidental quantity, applicable under proper restrictions, to products made in the same way from approximately uniform crude products, but not applicable to all brandies alike, not useful for fixing a standard.

Dr. Schidrowitz (7) did not agree that it was an impossible matter to practically substantiate the genuine character of a spirit. He said of the analysis done, the samples did not represent those coming from the still-head. There was practical conditions under which samples might be taken so as to enable it to be shown within what limits the different qualities are types of brandy did vary.  It is evident that there is no definite relationship between the quality of a mature brandy and its composition., but there is possibly come relationship between the composition of a newly-distilled spirit and its potential quality.”

Lots of new names. I only recognize Konig. I had always wondered what these people were reading back then and apparently it was some serious stuff. I suspect most of the 19th century literature is not in English.

One problem Graham seems to have by looking at quality from an analytical measure is that his measurements are over simplified. He can only find total esters as acetic. He cannot further subdivide this ester content into the various individual esters like you can with new techniques though the new techniques cannot even find patterns in quality.

Understanding quality seems to be limited by our understanding of perception and neuroscience.  Subjectivity seems to come from our tendency to generate aroma illusions from taking in just aroma fragments in a distillate.

Graham ends up distilling fast and slow with his experimental distillate and finds it “inexplicable” how they differed in alcohol content when the same amount of distillate was collected.  I was hoping he was able to explain this phenomenon.  I can’t remember which other paper it gets explained in but apparently distilling fast challenges the subtle reflux provided by the neck of the pot still and can lead to significant changes in fractions.

“The ester content of the distillate obtained by low speed distillation is significantly higher than that of the distillate obtained by high speed. This may be caused by a loss of esters due to incomplete condensation when distilling rapidly, or to the formation of more esters during the longer distillation.”

“The difference between the aldehyde contents is not significant.”

“Alcohol. By rapid distillation the strength of the distillate remains fairly constant for the first part of the distillation but after the 5th fraction the strength drops gradually in increasing amounts. When distilling slowly the strength falls gradually from beginning to end in increasing amounts. Thus when distilling slowly the temperature in the still will increase gradually, and impurities will distill over more uniformally, and their separation should be more marked. The lower strength of the fraction by the slow distillations is probably due to the difference in strengths of the low wines.

Esters. By rapid distillation there is a sharp decrease in esters from the first to the fifth fractions, but from the 5th to the 10th fractions the change is not appreciable.”

“According to Australian methods of separating the ‘heads’ and ‘tails’ fractions, 1 to 3 and possibly 4 would be separated as ‘heads’ while fraction 10 and 11, owing to their low strength, would most probably be included in the ‘tails’. This leaves fractions 5 to 9 (inclusive) as representing the spirits fraction. The average ester content would then be about 37, which is not high enough to satisfy the customs authorities of certain importing countries. On consulting the results of analysis of commercial brandies it is noted that the average ester content of the sample (excluding the samples 8,11, and 12, none of which are really typical commercial brandies in Australia) is 39, which agrees remarkably well with the above figure. The above method of separation is probably a fair indication of Australian method.  The rate of distillation has considerable influence on the distribution of the esters throughout the distillate.  When distilling slowly the ester content of the first fractions is not so high, and the decrease is not so sharp.  The value for the middle fractions is not so low, and consequently the ester content of the spirit as obtained by the aforesaid method of separation will be higher. The actual value is 46 as compared with 37 obtained by rapid distillation.”

“Greatest differences due to varying the speed of distillation are noted in the distribution of the volatile acids.  By rapid distillation the first few fractions comparatively high in volatile acids, there being a sharp decrease from the first to the fourth fraction, when variations become relatively small.  The amount gradually decreases up to the seventh fraction when a slight increase in each fraction becomes noticeable. Marked increases are noticeable towards the end of the distillate….

…The value for the tails for the slow distillation is very much greater than that for the rapid distillation, and it must be concluded that by slowing down the rate of distillation the volatile acids will tend more so to concentrate in the tail fractions. The explains the difference in the volatile acid values of the low wines.”

At the end Graham gives an acknowledgement to Allen R. Hickinbotham for advice throughout the work. Someone named W.J. Hickinbotham did lots of theoretical work on distillation in the early 20th century that is referenced by Amerine.  Apparently there was even a book written about the collaboration of Allen Hickinbotham and Roseworthy Agricultural College.  I thought they might be one in the same person but it appears to be a common English name.

“References.

1. Vizell “Wines of France.”

2. Elliot, C. “Distillation in practice”.

3. Young, S. [Sydney] “Distillation Principles and Processes.”

4. Allen’s Commercial Organic Analysis – Vol. I Fifth Edition.

5. Buttner, G. and Miermeister, A. Brit. Chem.Abs. B. June 1930.

6. Cornell, L. and Montanna, R. Ind, Eng. Chem. Dec. 1933.

7. Hehner, O. Analyst 1905. “Brandy”. [this paper privdes a great list of names and titles we can scour to find analysis of early commercial products similar to joseph Konig which I discovered years ago.]

8. Methods of the Assocn. Official Agric. Chemists 1935.

9. Hossack, J. Analyst 1935. “Determination of Esters in Alcoholic Liquids.”

10. Kelly, C.W. Unpublished data.

11. Espezal, P. and Jaulmes, P. Analyst 1935. “Determination of Aldehydes in Wines and Spirits.”

12. Joslin, M.A. and Comar, C.L. Ind. Eng. Chem. July 1938. “The determination of Acetaldehyde in Wines”.

13. Sutton, F. “Volumetric Analysis”.

14. Simmonds, C. “Alcohol, Its Production, Properties and Applications”.

Chas. W. Kelly. 1938. Suitable methods of testing commercial spirit and the results obtained in testing a representative group of commercial samples.

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.  We should probably figure out how to digitize all of the papers.

Kelly, Chas W. Suitable methods of testing commercial spirit and the results obtained in testing a representative group of commercial samples. 1938. from Series 600 University of Adelaide Archives, Inventory Identifier 060000004 Box Number 1. [PDF]

This project was unfortunately not completed by Kelly but I’m not sure why.  It still seems to have received a Karl Weidenhofer prize.

Chemistry and analysis was particularly important to the Roseworthy program. Alan Hickenbotham who many of the papers thank in their acknowledgements was a chemist who made many firsts in wine analysis.  Hickenbotham’s work paralleled that of Maynard Amerine and Emile Peynaud.

The paper starts with a bibliography with some references that are new to me:

“2. Simmonds ‘Alcohol’ page 270, 1919.” Page 270 relates spirit percent alcohol and specific gravity.

“5. Vasey ‘Analysis of potable spirits’ 1904.This English text supposedly contains some of the statistics found in the famous French book on analysis by Girard and Cuniasse.  He acknowledges the works of Allen, Hewitt, and Schidrowitz who turn up in a lot of early bibliographies.  He even thanks M. Ordinneau whom he visited in Paris and described his work as well known. It is worth while to start reading at page 67 and hear Vasey’s anecdotes of organoleptic analysis.  He describes strange foaming with soda water of some spirits and formation of soaps when other spirits are mixed with caustic alkali and distilled. Definitely a notable book.

“The analysis of fortifying spirits has been, prior to this last decade, much neglected in this country, partly because little attempt was made to draw up a systematic scheme for their examination,…”

This paper is important but not particularly exciting. I do need to learn more about the specifics of these analysis procedures but at the moment I have no where to put them to use. Some day.

The analysis that Kelly explores probably paves the way for a lot of the other papers.

B. Hickin. 1975. A Modified Distillery Procedure

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.

Hickin, B. Modified distillery procedure: effect of run-back of heads and tails to subsequent wine charges on the efficiency and yields of pot still brandy production. 1975. from Series 600 University of Adelaide Archives, Inventory Identifier 060000096 Box Number 3. [PDF]

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.

Green Apple Soda as De-aeration Color-Indicator-Test

Acmeapple soda

For a while I’ve been trying to dream up a test that could illustrate the effectiveness of reflux de-aeration with the champagne bottle manifold.  Of course you can smell the absence of oxidative aromas in de-aerated lemon juice but not everyone smells so well, not even experienced culinary professionals.  A better test would be something visual which made me think of apples.

Apples are subject to oxidative browning which many people are well aware of.  The juice starts out pale and fairly clear like white wine then slowly turns brown before your eyes.  My hope was that de-aeration could remove enough oxygen to prevent any visible browning.  This might be achieved without even adding any ascorbic acid as anti-oxidant.

Using only reflux de-aeration, the juice of green apples stays green and the highly carbonated product is delicious even by itself with no added sugar or acid.

Of course it is even more delicious in a cocktail:

5 oz. highly carbonated green apple soda (probably 8g/L dissolved gas)

1 oz. gin (something burly and high proof)

.5 oz. lime juice

2 g. non-aromatic white sugar

The green apples were juiced with an Acme centrifugal juicer.  The juice was then quickly funneled into a champagne bottle (a clear bottle!) and reflux de-aerated at 65 PSI.  Centrifugal juicers are known to whip a lot of air into the juice accelerating browning but miraculously reflux de-aeration takes the oxygen right out.  Once the oxygen was vented, the juice was carbonated to 8 g/L of dissolved gas which gives it quite the sparkle.

At this point the unadulterated juice is turbid and has some sediment which might irk some neurotics, but the settled juice could easily be racked before carbonation to remove most of the particulates.

To clarify the unadulterated juice within reason on the larger scale (gallons), I bet the juice could be de-aerated in a 3 gallon keg, allowed to settle, then racked off by use of a floating down tube.

Production is pretty quick, low foot print, and economical. No enzymes, no agar clarification, no centrifuges (even though I love those techniques!). Just plain old raw juice, reflux de-aerated.