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The Use of Glycerine in Wine
Parent's Method of Preserving Wine.
This consists in the addition of a small quantity of tannin or tannic acid to the wine, which perhaps acts in a similar way, by destroying the vitality of the spores of the fungus, since a microscopic examination of wine known to contain these germs, within a few weeks after being treated with the tannin, has failed to detect the slightest trace. Indeed, wine which has already begun to change, and become turbid, can be restored to its primitive clearness, and with a great improvement in its taste. Care must be taken, however, to use only tannin which has been prepared from the constituents of the grape, since the slightest proportion of the extract of nut-gall, although accomplishing the general object of destroying the fungus, will impart a peculiar taste, which never disappears. The Use of Glycerine in Wine.
Glycerine differs from sugar in not fermenting or taking any active part in the process of fermentation. It can, therefore, be made use of after fermentation, to impart any required degree of sweetness to wine, without the risk of further fermentation, as is the case with sugar when used for this purpose; it is said that it can be added with perfect safety to even a young or new wine, as soon as it has become clear. It is absolutely necessary that the glycerine should be chemically pure. The proportion of glycerine should be from 1 to 3 gallons for 100 gallons of wine, according to the quality of the latter. If the wine is perfectly clear it will be ready for bottling at once. Mix the glycerine first with an equal quantity of the wine, and then add the mixture to the rest.
This is not a dish but a pair of trade procedures for "doctoring" finished wine: tannin as a supposed sterilant, and glycerine as a non-fermentable sweetener. Both belong to a period before wine microbiology and additive law existed in any modern sense, and neither should be reproduced.
- The purity clause is the whole problem"It is absolutely necessary that the glycerine should be chemically pure" was an instruction the nineteenth-century buyer had no way to verify. Commercial glycerine was a soap and candle byproduct, and technical grades have on occasion been found contaminated with diethylene glycol, a poison that is sweet and viscous much like glycerol. That such a substance can pass for glycerol in wine is not hypothetical: in the 1985 Austrian wine scandal diethylene glycol was deliberately added to exported wine as a sweetening agent.
- Quantities as writtenOne to three gallons per hundred is one to three percent by volume. Scaled down that is roughly 2.5 to 7.5 tablespoons per gallon of wine, but the text gives no way to judge which end of the range a given wine needs beyond "the quality of the latter," which is not a specification.
- It is adulteration, not winemakingAdded glycerol is not a permitted additive in wine under US TTB standards of identity or EU wine regulations. Wine sweetened this way cannot legally be sold, and the whole point of the technique was to make a thin wine taste richer than it is.
- The tannin claim is falseTannic acid at the levels used in fining does not sterilise wine or kill yeast and bacterial spores. A cloudy, turning wine is spoiling from acetic acid bacteria, Brettanomyces or lactic organisms, and tannin will not reverse that. What the author saw was tannin and protein flocculating and dropping bright, which hides haze without removing the cause.
- "Spores of the fungus"The phrase reflects post-Pasteur vocabulary applied loosely. Pasteur's Études sur le vin (1866) identified microbial "diseases" of wine, and the trade seized on the language well before it had the tools to test any of these remedies microscopically with the confidence claimed here.
- Nut-gall versus grape tanninThe warning is one of the few sound observations on the page. Gallotannin from oak galls carries harsh, inky phenolics that do not integrate, which is why enological tannins are still sold by botanical source and specified for the job.
- If you want a sweeter wineSweetening and stabilising finished wine is a solved problem with measured sulphite and sorbate additions, or with sterile filtration, and any current winemaking text covers it. Use one of those rather than this.
The context of this kind of procedure is the phylloxera catastrophe: from the late 1860s the root louse destroyed most of the French vineyard, wine grew scarce and dear, and an enormous trade grew up in stretching, colouring, sweetening and "restoring" thin or failing wine, along with building wine outright from raisins, sugar and water. Glycerol was an attractive tool because it occurs naturally in wine already, produced by yeast during fermentation at roughly half a percent to one and a half percent, where it contributes much of the sense of body and sweetness on the palate. Adding more was simply a way of counterfeiting that impression in a wine that had never earned it, and unlike sugar it would not restart fermentation in the bottle. The same reasoning resurfaced in the 1985 Austrian scandal, where the sweetening agent turned out to be diethylene glycol rather than glycerol, and effectively ended that country's bulk export trade overnight.