Ah, kits are getting so clever these days! I would say it all depends on the quality of what you feel, taste, see, and smell for the material that comes in your skin pack. Not specifically to kits, but in general you want to use all of your senses to try to figure out what that material might add to your wine during an extended maceration, which will expose it to the higher-alcohol content of your finished wine. Aroma, tannins, possibly color, and flavor particles will all come through. Seriously, put some skins in your mouth and chew them around — do you like the flavor? The tannin? If you have enough, put a few in a glass of water mixed with some neutral vodka at around 14% alcohol and let it sit overnight. That’ll give you another way to look at what might extract into the wine.
For fresh grape winemakers, leaving the skins in the wine after the fermentation is complete is a common practice, but even they need to be careful of going over two weeks and managing headspace for oxidation. Once the CO2 is gone from the top of that fermentation, it’s really easy for VA (volatile acidity, caused by Acetobacter) and other bad guys to grow in your fermentation because the wine is essentially unprotected. You may not have CO2 on top nor have free SO2 in the wine yet since fresh grape winemakers may still want to send their wine through MLF and it isn’t sulfured yet. But the fact is wine kit companies don’t recommend sending their wines through MLF since sorbate and lactic acid bacteria are not a good combo.
Spoilage is absolutely the biggest risk with extended maceration. A normal kit size, like 6 gallons (23 liters) will be very challenging. With a larger volume (like if you’re working with at least a 50-gallon/190-L, trash-can size) then yes, you would check in every day for sure. In that case, if you can get some dry ice, you can keep the headspace protected by floating an empty pie tin on top of the skins, and then filling it with dry ice pellets once or twice a day. Be sure to keep the lid of your fermenter tightly covered. Be aware that CO2 is slightly heavier than air, so if you want to preserve the headspace in good condition, open the lid carefully so as not to disturb the settled carbon dioxide layer. Carefully (because there’s CO2 gas . . .) sniff the interior of your fermenter. If you smell VA, acetaldehyde, or ethyl acetate, (the last two are ingredients of nail polish remover) then it’s time to pull the plug and think about pressing or straining out the skins.
With all that said, my expertise doesn’t necessarily lie in the world of kit winemaking. With that in mind I decided to reach out to one of the kit making companies to get their feedback. Technical expert Gail Tufford from the Winexpert line of kits had the following to weigh in: “There is no benefit to extending the fermentation period of a kit with skins. It is best to rack off of the skins and sediment after 14 days, 17 at the most. The skins will be spent by this point and will offer no further alcohol, flavor, or aromatics to the wine. The lees will start to break down and can give off-flavors if the wine is left on the sediment too long. It is really important to punch the skins down every day during fermentation. Mix them around and squish the skins bag to the sides of the fermenter and give it a good stir to incorporate flavors and tannin into the must. Even though the wine is naturally off-gassing, which offers some protection, there is still a risk of exposing the wine to bacteria if left in the fermenter too long.”
So there you go Paul, we’ve got some general advice on extended maceration and some kit-specific advice for you. Hope that helps and happy winemaking!