Water Into Wine
Since kit wines are almost all intended to make 23L and they start off at between 7.5L to 16L depending on the type of kit, they require the addition of 7.5L to 15L of water. Since the water was originally remove from the grape juice by some method of distillation it would follow logically that the only thing that should be added back would be a variant of distilled water – as pure as chemically possible. After all, no minerals or trace elements were removed, so water with minerals and such would alter the character of the wine.
This turns outs to be one of those things that while technically true, it’s also completely unimportant. It turns out that unless your water tastes or smells absolutely horrible or is contaminated with bacteria or high mineral counts, it’s just fine to use in making up wine kits.
Two of the most common concerns about water:
1. Chlorine added to disinfect municipal (city) water is a sterilant. It kills yeast and smells like a pool – icky.
It’s natural to assume that because you can smell chlorine or chloramines in your water supply (the additive is essentially the same as household bleach) that it’s going to affect the wine. What actually happens is this: all juices used in winemaking, be they kits or even fresh grapes, contain sulfite compounds. They’re present on all grapes. When added to a solution containing chloride ions (the form the chlorine takes in water) sulfites bind to the ions instantly, forming stable chloride salts such as potassium chloride or sodium chloride.
If this sounds familiar, that’s because it’s common table salt. If you bind out 100% of the chlorine in municipal tap water with sulfite, you’ll wind up with about two grains of table salt per 23L carboy. That teensy amount won’t have much effect, especially when it’s mixed into a wine with a Brix of 25 and a whole lot of acid, sugars and solid material. So, there are no worries from municipal water treatment.
2. The pH of water varies a lot, so it’s better to add distilled water (with a pH of 7.0) to make sure the pH of the kit isn’t thrown off.
pH is a numerical scale running from 1 to 14. Right in the middle, 7 is considered neutral, neither acidic nor alkaline: pure water at 25°C is pH 7.0. Above 7 is alkaline; below 7 is acidic. Because wine contains a lot of acid, it generally has a low-ish pH, somewhere above 3 but below 4. A ph of 3.4 is a pretty sweet spot for most wines.
In a solution containing other ions (like a kit wine), activity and concentration will not generally be the same. Activity is a measure of the effective concentration of hydrogen ions, rather than the actual concentration; it includes the fact that other ions surrounding hydrogen ions will shield them and affect their ability to participate in chemical reactions.
So it’s not just the amount of acid in the wine kit that affects the pH, it’s a bunch of other junk in solution as well. This is sometimes referred to as buffering. Kit wines tend to be heavily buffered, partly because they contain very high levels of solid material and partly because the effects of concentration and pasteurization include some bonding of acids and sugars and some release of ions.
And water isn’t. And that’s why the pH of tap water is pretty much inconsequential – there’s almost nothing there to release hydrogen ions. When chemists calculate the pH of a weakly acidic solution, they usually assume that the water does not provide any hydrogen ions. Add the wimpy tap water to highly acidic, heavily buffered kit wine and POWIE! the water will meekly do as it’s told, and get swamped in a tsunami of acids and dissolved solids from the kit.
In the thirty years I’ve been making wine from kits I’ve never used anything but the water that came from the tap, and never given it a second thought. If it’s good enough to drink, it’s good enough for winemaking. But if you’re unsure go ahead and use bottled or filtered water: it can’t hurt your finished wine and will give you good exercise lugging around water bottles – always good for building up a thirst!
Tim Vandergrift is the Technical Manager for Winexpert.