[This German paper is not too significant. The reason I’m posting it is because of its usage of both the exhaustive test and the Micko test.]
Beitrag zur Untersuchung und Beurteilung von Weindestillaten und Weinbränden.
G. Büttner und A. Miermeister.
Mitteilung aus der Preußischen Landesanstalt für Lebensmittel-,
Arzneimittel- und gerichtliche Chemie.
[Eingegangen am 5. Mai 1931.]
A. Changes in wine distillates during storage (laboratory experiments).
At the end of our Second Communication on the same subject (1), we expressed our doubts as to the accuracy of Ruppin’s (2) statements regarding the decrease in the amount of ester in the storage of wine distillate and stated our intention to report such attempts.
1) Diese Zeitschrift 1929, 58, 635.
2) Diese Zeitschrift 1929,57, 243.
The following experiments were made in the laboratory by storing wine distillates in glass bottles. Further storage experiments in barrels in the wine cellar are underway, which will be reported later.
The wine distillates used had alcohol contents of 67.6, 64.3 and 71.5% by volume. After having determined their content of acids, esters, aldehydes, furfurol and higher alcohols in exactly the same way as before, these methods of determination may be in some cases in need of improvement, but in our view, comparative values are sufficient. In this case, each one of the wine distillates was diluted to about 40% by volume of alcohol, and the undiluted and diluted distillates were placed in glass vials about half full and corked in the cabinets under the laboratory tables stored in fairly dark rooms, about 1.5 years. The results of the study of these wine distillates are shown in Table 1 below.
From this it is first evident that it is irrelevant whether the wine distillates unchanged or diluted to 40% are subjected to storage.
The content of furfurol remained unchanged in all 3 samples. The content of distillates in aldehyde has increased considerably, namely to twice that of samples A and B, and even to five times that originally present in sample C. This result is quite interesting, although it is known that fuel on standing, especially in the light, aldehyde containing after some time. Presumably, the increase in aldehyde content is due to the nature of the experimental setup, whereby the resulting aldehyde had no sufficient opportunity to further oxidize to acid. It can be assumed. that upon storage of wine distillate in barrels, the resulting aldehyde will convert to much greater extent due to the continuous air supply by autoxidation with intermediate formation of a I’ersäure in acid. In any case, it has been proved by our experiments that a very substantial increase in the aldehyde can occur in the specified type of storage, that is to say under conditions which can also be found in wine-burning businesses.
[I’ersäure seems to be google-able but only as a very old word I don’t understand how to translate.]
In addition, the content of the wine distillates in acids has increased, especially in the case of sample A; in the case of sample C, the increase has been considerable, and above all in the case of esters. It thus turns out that our doubts about the decrease in the amount of ester in storage, which Ruppin believed he had to predict by applying Guldberg-Waage’s law, were justified. Obviously, any equilibrium is repeatedly disturbed by oxidation of aldehyde to acids and further formation of new esters. Walter (1) comes to the same conclusion in his storage experiments with wine distillate, which became known after the end of our experiments. It can therefore be assumed with certainty that in our storage experiments in barrels, as a result of the oxidation of the aldehyde taking place, an even greater increase of the esters will take place, and not, as Ruppin supposes, a diminution. Ruppin’s calculations on the reduction of the ester content of wine distillate after reduction to 38% by volume of alcohol are also erroneous and are refuted by our experiments.
(1)Walter, Ester, ihre Entstehung und Bedeutung für die Beurteilung von Edelbranntwein. — Deutsche Destillateur-Zeitung 1931, 47, vom 18. April 1931.
The content of the wine distillates has been taken from higher alcohols. Although this decrease is not significant, it can be observed uniformly in all 3 distillates, so that it can be assumed that the higher alcohols are also subject to oxidation (any esterified higher alcohols would have to be recovered during the investigation).
If one calculates the intermediately formed quantities of aldehyde contained in the newly formed amounts of acid (calculated as acetic acid) and esters (calculated as ethyl acetate) and adds them together with the determined amounts of newly formed aldehyde (acetaldehyde), then it has 1.5-year storage, calculated on 1 liter of wine alcohol, estimated at:
A B C
un reduced Distillate 700 mg 620 mg 470 mg Aldehyde
reduced Distillate 600 mg 440 mg 420 mg Aldehyde
These values are only an approximate estimate because the method used to determine the esters gives only approximate values and in this estimation the oxidation of the higher alcohols which has taken place as well as other circumstances have been neglected.
B. Experiments on the determination of the approximate amount of added diluted fine spirit to wine distillate or brandy of known composition.
In practical food control, the chemist will often wonder whether a brandy supplied by a particular firm has remained unchanged or has been blended at the intermediary or retailer with 38% neutral spirit and, if so, in what proportion. To clarify this question, two series of experiments were carried out, one with a high-quality wine distillate “Grande Champagne” and a second with an ordinary brandy, blended with 10%, 20%, 30%, 40% and 50% neutral spirit. The neutral spirit was previously adjusted to the alcohol content of the wine distillate and the brandy. Further, in the brandy test series, the neutral spirit with sugar color was brought to the same color shade of the brandy, so that the mixtures did not differ in their color. The dilution conditions were unknown to the investigator.
Table 2. Trials with wine distillate.
[From the above chart:
Gegeben Zusatz von verdunntem Feinsprit % = Added addition of diluted neutral spirit% which implies the pure Cognac?
The next column is the notes on Micko distillation:
2. bis 6. Fraktion sehr gut weinig = 2nd to 6th fraction very good
3., 4. und 5. Fraktion gut weinig, 2. und 6. Fraktion schwach weinig = 3rd, 4th and 5th factions well, 2nd and 6th fraction weak
3. und 4. Fraktion gut weinig, 5. Fraktion Spur weinig = 3rd and 4th Faction well wine-y, 5th Faction trail vinous
Daraus geschätzter Zusatzan verdunntem Feinspirt % = From this estimated additive to diluted fine spirit % (I think this implies their guess from the organoleptic Micko test.
The next is Wüstenfeld’s exhaustive test followed by another guess based on that organoleptic test.
Their next test is classic counts of acids, esters, furfurol, aldehydes, and higher alcohols followed by another guess and I bet the most telling figure is the furfurol.]
The wine distillate used was a particularly extensive commodity. If its original composition had been unknown to the expert, then, according to the results of the blends (see table 2 above), a falsification complaint would have been possible only with the addition of 50% diluted spirits, simply because of too low an amount of esters and higher alcohols. After the failure of the Micko distillation and the exhaustiveness test, a complaint would be unjustifiable. If the undiluted wine distillate had been present at the same time as the analysis of the blends, whether a sample was stored or if it was still possible to inspect it at the operational control, all three test methods provide indications to estimate the addition of diluted neutral spirit. These estimates will obviously come closest to the truth when comparing the levels of aldehyde, esters, and higher alcohols, to 1 liter of wine alcohol, compared to the undiluted and the blended samples. It is necessary for all such estimates that the type of storage (glass jars or barrels) is taken into account. [A little bit of tricky logic here which is probably the failure of translation.]
The results given in Table 3 confirm the findings of Table 2. The brandy used was a normal commodity. If its original composition had been unknown, it would have been possible to characterize it as suspicious at 30% by its higher alcohol content, whereas the Micko distillation and the exhaustiveness test only give rise to this suspicion at the 40% level. If, at the same time, a comparative sample of the unchanged brandy is present, then the estimate of the added diluted spirit is most certainly to be carried out on the basis of the content of higher alcohols, esters and aldehyde.
C. Compilation of test results unopposed
and objectionable wine distillates, brandy and fortified wines.
In the following, following our II. Communication, we announce the following findings to show the composition of the relevant products taken from practical food control.
[To stand a chance at making sense of these charts, they probably need printed out and laid side by side sort of like a newspaper.]
(1) Despite the very low content of fortified wines from southern countries. However, we keep these neutral wines for the production of neutral brandy