My aim here is to sacrifice a bottle of Stock’s sweet vermouth to learn something about it. Most importantly, its official sugar content unobscured by alcohol that can only really be found by using distillation.
Before distillation and separation of the alcohol, the vermouth’s brix can be tested obscured by its alcohol content to see how much it throws off the hydrometer (11.25 brix). Most people’s understanding is that sweet vermouths are much higher in sugar so maybe the alcohol (16%) throws the hydrometer off more than I thought (I really just estimated the reading would be off one or two percentage points).
I put the vermouth into the still with an equal volume of water to essentially split it in half. The half left in the still is sugar, water, acid, and whatever aromatic compounds do not distill. What comes through is alcohol, distilled water, and what ever aromatic compounds that are volatile.
After the run and re-cutting what was left in the still to the original volume with distilled water (because a small volume escaped the system) the hydrometer shows a reading of 15.5 brix. This result seems likely because it is within Maynard Amerine’s guidelines for sweet vermouth.
Now we have something intuitive to shoot for in our home made vermouths.
During the run I was also able to taste the distillate as it came out of the the still. The results were very cool in that it smelt exactly like it does out of the bottle. You do see some of the separations of the botanicals as they move through in waves. The orange phase is the most distinct and intense showing how important shades of orange are to a sweet vermouth. I thought I noticed a whisper of vanilla along the way that I never tasted before in Stock and towards the end I noticed heavier wormwood-maybe herb-like aromas.
Now the 15.5 brix measurement of sugar can be translated to grams/liter so we can think of it in another way. With the help of the grams/liter translation, the volume the vermouth’s sugar takes up when dissolved can be found so that we can solve our two variable equation for sugaring and fortifying our wines to stock’s 16% alc. y 15.5 brix model (port often uses a 18% alc. by 6 brix model so if you substitute it for vermouth you will need to compensate with extra sugar for a drink that isn’t too dry!).
A formula that I’ve come across but never really used is weight in g/L = sg * brix * 10
brix 15.5 = SG 1.06326 so —-> g/L = 1.06326 * 15.5 * 10 = 164.8 g/L
Which is 5.81 oz. if you can’t handle metric
(what is interesting is that the tables in the back of Daniel Pambianchi’s Techniques in Home Wine Making show different results. His would be higher by more than 20 grams. So did I go wrong anywhere? I used the Circular of the National Bureau of Standards to get my specific gravity for 15.5 brix. The circulars table also computes the g/L of sucrose so it is an awesome resource to the liqueur maker.)
Now we can see what 164.8 grams of sugar looks like undissolved volumetrically in an oxo measuring cup. using whole foods organic sugar it looks like 3/4 of a cup (different sugar types will make it vary slightly).
When dissolved this will compress. but by how much? Supposedly there are wine makers tables for such things but I haven’t been able to locate any. Pambianchi does note that adding 250 g to 1 liter of water yields a new volume of approximately 1.2 liters.
A useful table may not be that important since we are primarily going to be using the same sugar content over and over. We can probably rely on a one time experiment with sugar and water.
A sugar-water solution and my scale shows that 164.8 g/L dissolves and compresses to become about 86 milli liters in volume (2.9 fluid oz.)
This gets us closer to how much we have to over fortify the wine to bring it back to 16% when sugar is added. More algebra could solve it exactly but the numbers are looking round and it should be noted that alcoholic beverage labels, even on wines, are allowed to have a one percentage point margin of error so if it was really 17% alc. but printed as 16% alc. they would be off by more than 5% and be okay. We could just fortify to 17.5% before we add our sugar and be done with it (we don’t even know how accurate the wine we use to start is anyhow!).
My understanding from Amerine’s books is that we want as little alcohol as possible so our beverage will not be hot tasting or cost us lots of tax money. Sweet vermouths commonly are 16% alc. while dry vermouths are usually 18%. Being over 16% alc. puts both over the very important acetification point (vinegar bacteria) but sweet vermouth may be able to be slightly lower because its large sugar content protects it from various other lactic bacterial spoilage thresholds (I really don’t know but 18% is a key number for those). Another reason for the differing alcohol contents could be because within a producer’s production process, both sweet and dry (before they are aromatized) come from the same fortified wine stock. The volume of the sugar in the sweet dilutes the alcohol to 16% (with an accepted one percentage point margin of error!).