Glycerin in Winemaking
I first started using glycerin decades ago when making liqueurs from extracts — it was a less expensive way of making good liqueurs. In a blender put 1 bottle of extract (1-2 oz), liquor (typically vodka or brandy, depending on type of extract), sugar syrup, and 1 oz glycerin. Blend to mix, and I had 1 quart (or liter) liqueur.
I made liqueurs without glycerin, but all tasted thin. The flavor and aroma were there, but adding glycerin perked the liqueurs a lot, with more mouthfeel (sensation on the tongue), and in general smoother.
In the last five years, I’ve started adding glycerin to my wines at bottling time, for the same reasons as adding to the liqueurs.
Comments about “mouthfeel” abound, but finding a good definition took searching. The best I’ve found is “texture”, the way tannin imparts dryness, acid imparts bite and/or sharpness, and glycerin imparts a thickness of the wine, so it more coats the tongue, gums, and cheeks. Up to a point, glycerin makes the wine tackier and improves sensation.
Body is how rich and full the wine tastes. A thin wine is lacking in taste, and probably aroma, which affects taste. It’s easy to confuse this with mouthfeel, but they are different.
Wine can be harsh in different ways: too much tannin or acid can make the wine unpleasant. Glycerin may soften the harshness, making an unpleasant wine good.
Glycerin may impart a perception of sweetness, although it contains no sugar, nothing fermentable.
How Much To Add?
I’ve seen recommendations to add up to 2 oz (59 ml) glycerin to 1 US gallon (4 liters) wine. In my experience, that’s way too much as it makes the wine cloying and, well, not like wine.
Note: While I realize that 1 US gallon does not equal 4 liters, for the purposes of this post, they are close enough for practical purposes.
I generally recommend 1/4 oz (7.4 ml) to 1 oz (29.6 ml), although my most frequent addition is 2/3 oz (19.7 ml) to 3/4 oz (22.2 ml).
Based upon my tastes, I typically start with 1/2 oz (14.8 ml) per gallon. If the wine is thin or harsh, I’ll increase the initial amount.
Stir VERY well (glycerin is thick) and taste. I reserve a large glass of the base wine and will compare the current wine and the base wine.
If I think the wine needs more glycerin, I’ll add more, stir very well, and taste again. Repeat until satisfied.
Alternately, put 1 gallon wine in a smaller fermenter and use it for experimentation / taste testing. If too much glycerin is added, there is more wine blend in to correct the over-addition.
There is no science to this — it’s all to taste. Trust your taste buds. When you think it needs just a bit more, stop. It doesn’t.
Keep in mind that it’s always easier to add more than to take some out, so don’t put in too much.
Another alternative is bench testing, add tiny amounts of glycerin to individual glasses and choose the favorite. I don’t do this because such small amounts of glycerin are added to each glass, that a very fine measuring tool is required. Plus it’s too much effort.
Making It Dissolve
Glycerin is thick and getting it to dissolve completely can be difficult. Years ago I had a batch where there were globs of glycerin in the bottom of the bottling bucket, so most bottles got just enough and a few got WAY too much.
Following is a list of methods that have worked.
1. After the wine is in the bucket, start stirring the wine and add the glycerin in a very thin stream while continuing to stir. Although hand stirring works, a drill-mounted stirring rod works better.
2. Add the glycerin to the bottling bucket after the siphon has started, using the siphoning wine to rinse the measuring cup. Stir during the siphoning. This works fairly well.
3. Dilute the glycerin with 5 times its volume in wine and pour into the wine while stirring. This seems to work best as the globs of glycerin can be broken up in the smaller container, then better distributed when adding to the main batch.
In 2019 I made a second run wine that was barrel aged for a year adding 6 oz medium toast oak cubes in 54 liters (14.25 gallons) wine. I reserved a bottle without glycerin but added it to the vast majority of the wine. Two years later I opened the reserved bottle — it was undrinkable, the oak taste too harsh and overpowering. The addition of glycerin completely changed the wine. Most changes are not this significant, but it can happen.
As previously mentioned, add by taste, and go lightly with additions. When satisfied, stop.
Remember that the enemy of Good is not Bad. The true enemy is Better. As in “This is really good, but I can make it better!” 🙂