I got an interesting question from a winemaker in California the other day. He wanted to know why the published Brix levels of a kit we sold were low, relative to commercial harvest sugar levels. It's a good question because it's got a two-part answer. 

First, the particular Brix level he was reading (21 degrees brix, 12% potential alcohol) was on an information sheet, and it listed the harvest value for the 75% of the grapes that made up the listed varietal (Sonoma Cabernet in this case), rather than the finished kit itself. The particular kit actually starts off at almost 25 brix, 14.5% potential alcohol.

This of course leads immediately to a second question: why so low on the Cab, and where does the extra sugar come from? 

Wine kit companies don't like handling super-ripe grapes. Not only are they squishy and prone to over-ripeness and rot, above 23 brix we start seeing very low acid and high pH. While correctable, the acid you have to add to correct the juice always falls out as a precipitate (wine diamonds, or potassium bitartrate) and it mostly does it post-fermentation, which a lot of folks find irritating. When we harvest at a reasonable brix we get brighter fruit and much easier handling. 

The extra degrees of sugar comes from the other juices and concentrates we blend in to make up the kit. In this case the kit also got a bag of grapeskins, which were suspended in jammy 52 brix  Cabernet concentrate. It's kind of strategic: we shoot for the best quality of fruit and balance of acidity, and make up what we need to with Chaptalisation in our winery.

But it does raise another point: as a general rule of thumb, many wine kits, including most of those made by my company, have a slightly lower starting gravity than commercial wines, and slightly lower alcohol contents. This is done on purpose, and a lot of it is my doing: I don't like over-alcoholic wines, which in most cases is anything over about 13.5%. There are exceptions: most wine kit companies make a 'Rosso' or a 'Rossa' or a 'Grande' or other proprietary name. These kits have high alcohol contents specifically to cater to folks who want a 'fruit-bomb' wine that packs sweetness in alcohol to drive fruit character. 

I've expressed my opinion on the pernicious practice of creeping alcohol levels before, and even named a culprit. I'm not the final arbiter of taste (well, I am, for my own taste) but there's another benefit to the leaner, less explosively fruity-sweet style. It ages on a very predictable curve and is firmly planted in a style of winemaking that lasted for hundreds of years in the old world, and which was only challenged in the last thirty. I kind of like hanging on to a bit of tradition--especially when it makes good wine.