Periodically we get asked about making non-grape wines and if/how our equipment can test for the same parameters when different fruits, vegetables or flowers are used. We thought we would explain how the test kits that we offer may need to be adapted to test a non-grape wine.
Country wine, as it’s commonly called, is wine made from something other than grapes. We have customers that make mead, cider, kombucha, jalapeno wine, blueberry wine, and dozens of other fruit combinations. They have had much success using several of our testing kits. We note that some analyses require adjustments to the calculations and/or procedures to get useful results. In rare cases, some of the tests cannot be used because of interferences.
Vinmetrica started after I saw a need for better SO2 testing for home winemakers. In fact I cut my home winemaking teeth using apricots from my tree in Palo Alto in the 1990s. Since then, we have moved more towards traditional grape wines, but every so often we will make a small carboy of peach or fig wine using the excess fruit off the trees in the backyard here in San Diego. Many of the same cautions about harvest and crush in grape winemaking apply when making non-grape wine. To reduce the chance of bad outcomes, you want to ensure you have good fruit that is free of mold or vinegary odors, and that you are following proper procedures for cleaning as well as stabilization using sulfites.
We always advise you to seek out all the information you can regarding making non-grape wines. We will list several resources at the end of this blog. There are many books and forums that can help you with recipes and that contain tips and tricks for making specific types of wines. We are not exactly experts in non-grape wine recipes but we can help with the chemistry and testing of these wines. When using your Vinmetrica testing equipment, we recommend taking note of the various suggestions below.
Testing for SO2 using the Vinmetrica SC-100A or SC-300 unit:
First, respecting free SO2, be aware that some berries and other fruits have significant amounts of vitamin C (ascorbic acid), which interferes in the Ripper titration that is the basis for the Vinmetrica SO2 test, giving false high readings. Some common fruits with high levels of vitamin C are: persimmons, guava, kiwi, orange, blueberries, and strawberries. See the troubleshooting guide on our website or a separate blog post here for more information about how to test and possibly correct for it.
Other than that, the free SO2 test is generally quite reliable in most fruit wines and musts.
Testing pH:
Here, basically, pH is just pH, no matter what. There are no particular corrections needed. Calibrate in the usual way; we recommend a check with cream of tartar as detailed here in the troubleshooting guide.
It is advisable to make sure the sample is free of debris by settling, filtering or centrifuging.
Monitoring TA using the SC-200 or SC-300 unit:
For making country wine you will still want to test the TA before fermentation and before bottling. The TA test is run the same way as for grape wines. It’s just that the identity of the acids is often different. This of course should influence your choice of agents to add or subtract acidity. For grape wines, the major fruit acid is tartaric, so it’s common to report the TA value in units of tartaric acid, even though other acids (malic, lactic, succinic, and others) are also present. And usually the winemaker will use tartaric acid to make any needed additions to the acidity of the wine. For many berries, and certainly things like apple, the major acid is malic, so you may want to report the results as malic acid (see below), and you may want to add malic acid to increase acidity if needed. If you need to reduce acidity, in most cases you will add something like sodium bicarbonate, sodium carbonate, or calcium carbonate, irrespective of the major fruit acid, but it’s good to check what others have done for your particular fruit.
A little point about reporting and interpreting TA. In a TA titration, you take a known volume of the sample and titrate it with slow additions of a TA titrant, comprising sodium hydroxide of strength between 0.10 and 0.20 N, until the pH reaches 8.2. You note the number of mL needed to get there. Then the immediate result is a number that is “acid equivalents (eq)” per liter.
TA, equivalents per L (or “eq/L”) = V x N/S,
where V is mL of TA Titrant of strength ‘N’ eq/L to titrate ‘S’ mL of sample to pH 8.2 (or 7 in some places). For example, if you titrated a 5.0 mL sample (S), and used 4.0 mL (V) of Vinmetrica’s TA Titrant (whose N = 0.133 eq/L of NaOH) to reach pH 8.2, you would have
eq/L = 4 x 0.133/5 = 0.106 eq/L TA.
Frankly, “equivalents per liter” is a perfectly correct parameter for TA. But historically winemakers have converted it to something more tangible, like g/L of tartaric acid. And of course, numerous recipes and guidelines for adjustment are based on TA in units of tartaric acid. When you plug in 0.133 for the TA Titrant strength N and 5.0 for mL of wine sample S, then multiply by 75 g/eq (the “equivalent weight” of tartaric acid), you have
TA, g/L of tartaric acid = (V x 0.133/5) x 75,
or 2 x V as in our manual. In the above example, TA = 2 x 4.0 = 8.0 g/L as tartaric.
If you’re working with apple cider, whose major fruit acid is malic, you might want to report the TA value in terms of malic acid. The “equivalent weight” of malic acid is 67 g/eq; then it’s
TA, g/L of malic acid = (V x 0.1333/5) x 67 = 1.79 x V.
In Europe they often use units of sulfuric acid, even though there’s no sulfuric acid there at all (one hopes). The equivalent weight of sulfuric acid is 49 g/eq, so there it would be
TA, g/L of sulfuric acid = (V x 0.1333/5) x 49 = 1.31 x V.
Finally, everyone still seems to want to add one more bit of confusion by insisting on reporting values as %TA, or g per 100 mL. In that case, each of the above values is divided by 10, i.e.
TA g/100 mL (or %) = TA (g/L) / 10.
I’d like to see everyone use eq/L for TA, but even I still revert to g/L tartaric acid by habit. You can report your results in units of any acid you wish by using the equivalent weight of the acid at the end of the equation as above. But rarely do we see anything other than tartaric, malic, or sulfuric as used above.
Other Tests in Fruit Wines and non-Grape Fermentations
Testing MLF:
There are no corrections needed for non-grape wines when using the Vinmetrica SC-55 system. Follow the instructions for sample preparation in the usual way.
Testing ABV:
There are no corrections needed for non-grape wines or other fermentations when using the Vinmetrica ABV kit for alcohol content. Note that the volume of sample recommended is 100 microliters for a typical wine of around 13% ABV. Take more or less sample for lower or higher expected %ABV, respectively. Follow the instructions in the manual.
Residual Sugar:
In general there are no corrections needed. If the fruit is highly colored or very tannic, it will be necessary to decolorize the samples first, as described in the manual. Keep in mind that the default method in the residual sugar kit is for “reducing sugars” like fructose and glucose; sucrose, which may be present or added at some point, will not register in this assay unless you first follow the manual’s appendix for converting sucrose to fructose and glucose.
YAN:
No more preparation is needed than that described in the manual for YAN (yeast available nitrogen). You want to be sure to off-gas any dissolved CO2 as directed. Filter or otherwise clarify the sample to remove gross particulates.
DO:
Dissolved oxygen should work without further intervention. Calibrate the probe as directed. Remember that it’s usually best to put the probe directly into the bulk container, because trying to pull a sample into a small container can lead to false high readings from ingress of air. It’s also not a bad idea to sparge out the headspace of the container with nitrogen, argon, or CO2 before making the measurement.
Rich Sportsman 4-18-23
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References:
https://winemakermag.com/article/non-grape-winemaking
Stone Fruit: https://winemakermag.com/article/stone-fruit-wines-2
Mead: https://winemakermag.com/article/honey-based-wines
And of course, there’s the excellent guide for all fruit winemakers: Jack Keller’s Recipes for fruit wines
thanks a lot of information