Using Grape Skin Packs in Wine Kits

Grapes . . . they do seem to inspire metaphor, but not as much as they inspire winemakers and wine drinkers. It is the source of wine, the beverage we all know and love so much. (Well, one source: if there’s one thing I’ve learned in more than two decades of working in the consumer wine industry it’s that folks will ferment anything that grows-on trees or off-from bushes, gardens or forests.) But it’s the grape that gets me out of bed every morning, and more often than not sends me there at night. Wine made from kits is a step removed from grape-wrangling: crushed, macerated and pressed in a winery, the juice arrives at wine kit companies clear and mostly free of solid material, to be balanced and blended into the bag of rich, luscious juice that you lug home in its sturdy cardboard box, pour neatly and easily into your sanitized fermenter and with a few additions and a bit of stirring, you’re on the path to bottling day. So where does that leave the poor grape’s contribution to the process in kit winemaking?


In standard grape winemaking red wines get all of their color from their skins (yes, there are some red grapes that have pigmented flesh and they taste kind of yucky) so contact between the crushed grape pulp and skins is necessary for color extraction. As fermentation progresses and the sugars in the pulp are converted into alcohol, the alcohol extracts color compounds from the skins. If you prevent skin contact, by pressing red grapes immediately after crushing, you can produce white wines from red grapes-this is how Blanc de Noirs sparkling wine is made from either Pinot Noir or various blends of Pinot Noir, Pinot Meunier and Chardonnay.

Using the word color sells the glorious purple-red very short. The colors found in grape skins are anthocyanins, and young wines are very high in these compounds. They are quite reactive in wine: in low pH wines they’re red, at high pH they’re more blue-ish (ever clean wine with a base solution like ammonia? Pow, it turns blue!). They also react strongly to oxygen (which has implications for oxygen management in red winemaking) and sulfites. If you dose a young red wine with very high levels of sulfite, you can bleach it white — and interestingly enough, if you oxidize the sulfite off, it will regain some color.

But the anthocyanins in grapes aren’t all the colors we find in our finished wines. There are also pigmented polymers, which are a result of tannins linking to anthocyanins (a bit more on this later). These pigmented polymers are extremely color-stable, meaning they don’t degrade or change over time, unlike anthocyanins. There’s even a technique for making wine more color-stable that involves adding extra tannin to the crush — it can be useful in stabilizing colors when you don’t want too much skin contact because of undesirable flavors or aromas.

There are a couple of more color compounds that I’m going to avoid talking about, mostly because the chemistry makes me want to drink until the equations go away. The first of these is anthocyanin-derived pigments, the result of a hilarious chemical pile-up of anthocyanins, aldehydes and phenols. They’re pretty stable, but still able to further evolve in the wine. The other color compound, copigment, is no less complex (or any better understood), but it is pretty trippy. These are colorless compounds in the grapes that bond with anthocyanins, intensifying their color. While it’s not yet understood by the chemistry side of the wine business, that turns out to be not really important: Rhône winemakers have been throwing a few lugs of Viognier into their Syrah must for a long time, and getting more intense colors as a result. Fortunately, we can use grape packs without the need for certainty in the arcana of grape color.


But it’s not just color that comes from the skins. A significant (and important) part of the tannin in a red wine comes from the skin material, as well as from the seeds. It’s a good idea to take a moment to talk about what the word tannin actually means. We derive the word from Middle English tannen to make hide into leather. In turn the word came from Latin, tannum, meaning oak bark. Tanning leather exploits a basic characteristic of tannin compounds, one which causes them to bind strongly to other compounds, particularly proteins: cross-link a bunch of the protein in a floppy animal hide by soaking it with tannins and you get stiff(er) usable leather, whose proteins decay only very slowly.

Tannin appears in the leaves, bark and under-ripe fruit of lots of different plants, its presence probably an evolutionary response to predation: tannins taste bitter and indigestible. In grapes this bitterness, combined with high acidity, keeps birds and other predators from eating them before the seeds are ripe enough to sprout a new plant.

The tannins in wine are different from the ones found in grapes. Partly this is because there are other potential sources of tannin, such as oak from barrels used for storage or added as an élevage technique, and partly because winemaking techniques actually change the tannins themselves through a process of bonding, de-bonding and reforming with other compounds in the wine — an effect of the binding process mentioned earlier. Once again, I won’t go into a technical explanation of tannin chemistry because we don’t need to go full PhD to appreciate the dynamic and evolutionary process tannins go through to arrive at the astringency and mouthfeel present in a finished wine: as winemakers we taste those changes as we go. I should also throw in another reason I’m dodging a full explanation: as with the color compounds, we honestly don’t fully know how it works. All of my career I’ve been using the standard explanation that young red wines can be very tannic and ‘closed,’ but they soften over time as the most bitter or astringent tannins combine, get bigger and leave solution. We don’t actually know if they get bigger or smaller, or just break up in the acidic environment of the wine.

Color and tannin in wine kits

Since the juices and concentrates that go into the kits can’t go through a complete alcohol fermentation to extract the full range of color and tannin (because then we’d be selling wine, not wine kits), the question immediately arises, ‘Where do those colors and tannins come from, then?’ Rest assured, it’s nothing sinister like coloring agents or the intervention of a chemistry set. Rather, juice processors macerate crushed red grapes with a cocktail of enzymes, some of which break down pectins and others which break down cellulose. The crushed grapes are lightly sulfited and chilled, to prevent fermentation during the enzyme treatment. At the end the must is pressed, and the juice, clarified and filtered, is now rich in anthocyanins (color compounds) and tannins necessary to make wine.

But despite a lot of attention and effort to get the maximum extraction with this process, it’s very difficult to get out all of the compounds from the skins. Some of the tannins and colors, particularly the very desirable ones, are best extracted with an alcohol solution. And that’s where grape packs come in: by providing a certain amount of skins to the must, the alcohol fermentation can go that last extra mile to getting the good stuff out of the grapes and into the wine.

The packs

There are two main sorts of grape packs, dried and wet, and each has a different approach to providing color and tannin to the must for alcohol extraction. Packs of dried skins supply a high volume of skin and seed material for a given weight/volume of pack, while wet skin packs use heavily processed varietal skins to give a big dose of the good stuff.

Each approach has its merits: typically a finished six-gallon (23-liter) batch of wine will take about 100 pounds (45 kilos, or about three ‘lugs’) of grapes to make. If you’re trying to boost the alcohol-soluble tannins and color in your finished wine you’ll want to maximize the amount of grape skin material, and dried skins do that by removing all of the extra water, and most of the stems and cellulose.

However, many of the dried skins are derived from the Corinth grape, also known as a Zante currant (even though it’s not related to currants at all). It’s a small, mostly seedless grape originally from the Mediterranean, and grown there for millennia, and is sometimes marketed as fresh fruit in the US under the name “Champagne grapes,” although it’s doubtful anyone makes sparkling wine from them.

It’s perfectly possible to make single-varietal wine out of Corinth grapes, but the varietal character is a bit different from most of the common vinifera grapes used in wine kits. Still, dried grape packs bring the tannins and colors, and they’re less expensive than wet packs, which means you can get them in value-priced kits instead of just the big (and more expensive) premium kits.

Wet grape packs typically come in a size that’s roughly 10-15% of the total volume of the kit, packed in very high sugar solution of grape concentrate. The concentrate acts as a preservative on the grapes, with an extremely low pH and high acidity preventing both bacterial action and oxidation.

Because wet packs contain more pulp, cellulose and goo, they typically contain only about the same amount of grapes as the dried packs. Their benefits come because most of them are made from the same varietal grape that went into the kit (please check with your manufacturer to be sure: I can only speak for my own company, but typically this is the case), giving a very true and precise boost to the finished wine.

In addition, the skin packs are processed to maximize the extractability of the material, and like the grapes used to make the juices in the kits, they are treated with a tailored cocktail of enzymes (a different one!) that breaks them down to a point where even five or six days of fermentation will extract all of their pucker purple goodness.

Both of these things make the packs more expensive. First, sourcing the grapes themselves means bothering wineries and juice processors for a value-added product they’re not used to handling, and they have to charge full price for the skins as they would for the juice derived from them — the skins have to be crushed and pressed immediately, so the juice that comes off can’t be used to make varietal winemaking products — no color or tannin from the skins-plus an added charge for packing and blast-freezing them for shipment to the facility that processes them into packs, and then the extra handling and processing itself. This is why wet grape packs have so far typically appeared in the more expensive, premium-type wine kits.

Which one is better? I work for a manufacturer that only uses wet packs, but you can draw two conclusions from tasting dried pack wines versus wet-pack wines. First, the dried grapeskins can provide some pretty amazing results in kits that don’t have to cost an arm and a leg. Second, as with most consumer goods produced in a mature market (like wine kits), there is a very direct correlation between the actual cost of a product and the goodness it delivers, so premium kits, with their premium price, deliver some very good wine as well.

Probably the only way to settle this would be to make both kinds of kits and do a tasting. Two things about that: the handling instructions for the grape pack kits can be very different from a company’s regular kits. Be sure to read the instructions thoroughly before you start, and understand that there may not just be issues of handling a goopy mass of grape sludge or retrieving a bag of saturated skins from your fermenter, but also changes in racking, timing and the addition of other compounds to the kit. The other thing? You should probably invite an expert to your tasting to get his opinion on the wines. I’m just saying . . .