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Oil of Cognac
Oil of Cognac.
The flavor belonging to genuine French brandy is due to a peculiar oil, known as oil of Cognac. This oil is obtained by distillation from the marc, or lees of wine, either dried or made up into cakes, or, in their wet state, mixed with about seven or eight times their weight of water. The brandy from any part of the world may be very closely imitated by distilling the oil from the marc of the wines produced in the particular district. Oil of Cognac is also prepared by dissolving the fusil oil of marc brandy in strong rectified spirit, and then adding a sufficient quantity of concentrated sulphuric acid to form a sulphate; alcohol and excess of acid is removed by washing the newly formed compound with water. To 100 lbs. of marc add ½ lb. sulphuric acid; the oil is generally formed towards the end of the distillation, and is found floating in blackish drops on the surface of the distillate. According to a distinguished French chemist, this oil is a compound of potatoe oil and enanthic ether. Cognac oil when pure, has a true vinous odor, and, like all essential oils, requires to be cut with strong alcohol. One ounce of the pure article is sufficient to flavor from 200 to 250 gallons. The manufacturer should be very careful when using this powerful oil: add a very little at a time, and remember more may be added if necessary.
Oil of Cognac is very generally adulterated with alco hol; indeed, it is extremely difficult to procure the really genuine article. As a test to ascertain whether it is pure, we offer the following simple method:-Take a half ounce phial, and fill it exactly half full with the oil, then fill up the remaining space with water, and shake it well; if the oil is adulterated with alcohol, the latter will leave the former and mix with the water, conse
This is a compounder's formula for a flavoring concentrate, not a kitchen preparation, and it cannot be carried out today. The following notes explain the terms and the specific hazards.
- What the words meanMarc is the pressed skins, pips and stems left after winemaking; lees the sediment from the cask. Rectified spirit is high-proof neutral alcohol, and enanthic ether (oenanthic ether) was the nineteenth-century name for the aroma fraction chemists believed carried the vinous smell of wine.
- "Potatoe oil" is fusel oilBoth this and the "fusil oil of marc brandy" mean fusel alcohols, chiefly isoamyl alcohol, the heavy-tailing fraction of a distillation. Fusel oil is an irritant and toxic in quantity, and distillers generally cut much of it away in the tails, though isoamyl alcohol itself is used in small amounts as a permitted flavouring substance.
- Concentrated sulphuric acidHalf a pound of oil of vitriol to 100 lbs of marc, then esterification of the fusel oil with more concentrated acid, is bench chemistry with a strong dehydrating agent. It generates heat on contact with water and alcohol and produces charred, acidic residues; the text gives no temperature, no cooling, no neutralisation step.
- DistillingThe process depends on running a still. Distillation of alcohol at home is illegal in the United States and in most other jurisdictions without a federal permit, quite apart from the fire and vapour risk of heating spirit over a flame.
- Washing does not purify itRinsing the crude ester with water removes free acid and alcohol but leaves residual sulphates, unreacted fusel alcohols and whatever came over in the blackish drops at the end of the run. There is no assay here, only a smell test.
- The dose is the giveawayOne ounce flavoring 200 to 250 gallons is a dilution of roughly one part in thirty thousand. A preparation that potent, made without analysis, is exactly the case where an impurity carried through at trace level matters and cannot be judged by taste.
- The purity test does work, as far as it goesShaking the oil with an equal volume of water to see whether alcohol partitions out is sound old practice: the alcohol leaves the oily layer and the volumes shift. It detects dilution with spirit and nothing else, which is the limit of its usefulness.
- If you want the flavorBuy a commercial food-grade cognac or brandy flavoring, or use brandy itself. There is no domestic route to this compound.
Oil of cognac belongs to a nineteenth-century trade in "imitation spirits" that flourished because genuine French brandy was expensive, taxed and often unavailable. Chemists of the period had identified that the distinctive smell of wine and brandy came from a small aromatic fraction rather than from the alcohol, and named it oenanthic ether; the ambition of manuals like this one was to isolate or fake that fraction and dose it into cheap neutral spirit, so that a barrel of rectified spirit could pass as Cognac, Armagnac or any regional brandy whose marc one could get hold of. The claim that the flavor is a compound of "potatoe oil and enanthic ether" reflects the real chemistry only dimly: esters of fusel alcohols do smell fruity, which is why the trick half worked. Books of this kind were sold to rectifiers, saloon keepers and grocers, and the passage is best read as evidence of how thoroughly adulterated the drinks trade was before the food and drug laws of the early twentieth century.