The pH 4 reference solution (for use with the SC-200 or SC-300 unit + pH electrode) is now labeled as 4.00, the correct reference value at a temperature of 20 ℃ (68 ℉). The chemical composition of the solution itself is unchanged from before, and its reference value is still 4.01 at 25 ℃ (77 ℉). It’s just that since most of us work on wine or other beverages that are closer to 15 to 20 ℃ (59 to 68 ℉), a value of 4.00 is slightly more accurate than 4.01. Instruments that use the old reference value 4.01 rather than the new value of 4.00 do not produce significant error: less than 0.02 pH difference in wines with pH values from 3.00 to 4.00.
As mentioned in a recent newsletter, we have a new update to the firmware for SC-200s and -300s built after 2015 (Serial numbers 2897 and above for SC-300s, 470 and above for SC-200s). This new firmware, versions 3.2.F (or 2.2.F for an SC-200) and higher, uses the value of 4.00 instead of 4.01 for pH calibration. All new units being shipped will now have this new firmware version installed on them. If your instrument has a lower serial number, or an earlier version of firmware, it will set the pH 4 reference to 4.01 as usual.
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. Keep Reading More!
This is a regularly debated topic that deserves some attention. We’d like to refer you to a great blog by Andrew Waterhouse at UC Davis that breaks down all aspects of the “sulfite gives me headaches” conundrum. Below, we have summarized it for you, but briefly, sulfites are unlikely to cause that headache that some people report occurring within a few hours of consuming wine.
As most winemakers know, sulfite or sulfur dioxide is an anti-oxidant preservative used in winemaking that can also help protect your wine from harmful bacteria or other non-desirable things that might make their way into your barrel. Did you know it is also used to preserve dried fruits? Keep Reading More!
This time of year, when vineyards are quiescent, many of us use the downtime for bottling. At Vinmetrica’s sister company Little Oaks Winery, we are making final preparations for bottling in early Spring. This involves several activities, and a little coordination for proper timing. So we thought we’d share a little about what we do as bottling draws near.
This year we’re bottling our 2022 Viognier, 2022 Rosé of Sangiovese, and our 2021 Sangiovese. We’ll be producing about 180 cases all told. The grapes are from Monarch Hill Vineyard in nearby Escondido, our main source of quality grapes for 10 years now. The Viognier and Rosé, about 80 gal each, were fermented sur lie for 4 months, then cold-stabilized for 2 weeks before racking and storage at 55ºF. The ’21 Sangio was fermented in poly tanks, and after MLF completed, aged over the past year in 50:50 new:neutral Hungarian Oak barrels. We are pleased with the results, made possible in no small part by attention to monitoring important parameters.
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We get this question a lot so we thought we would discuss it here. [Note: Most of this information is available on our troubleshooting guide under SO2 Problems]
There’s two situations that may cause concern about the reading.
- Your instrument indicates an endpoint (beeps) right away, either before adding any SO2 Titrant, or after adding just 1 or 2 drops.
- Your instrument apparently never indicates an endpoint, even after titration with a large amount of the SO2 Titrant.
Situation (1.) happens a lot. Most of the time, this is just the normal endpoint response, telling you that your wine’s ppm of free SO2 is zero. To verify that the endpoint indication is valid, add 1 drop of 10% KMBS and stir. The signal should drop to below 50 right away, and the endpoint indicators should stop signaling. If the endpoint signaling does not stop, you may have a problem with the instrument.
Situation (2.) also crops up from time to time. Let’s say you are running an SO2 test on your wine and you use the ENTIRE 5mL syringe of SO2 Titrant, but your instrument stays on 0.00 or a low number, indicating that you still haven’t reached the endpoint. This would normally mean you have over 100 ppm free SO2 in your wine. But you’re pretty sure there isn’t that much SO2 present. So your instrument must not be working, right?
Actually, it might be working just fine! Keep Reading More!
A few notes on measuring acidity and pH of wines.
At Vinmetrica, we get a lot of inquiries about the acidity of wines and how to measure them. We have a blog on pH & TA here (and followed up here) on our website wherein you can find detailed discussions about various aspects of this subject. Here I’d like to touch on a few of these.
pH vs TA
pH is a measurement of the free hydrogen ion concentration (OK, actually it’s activity that is measured; close enough…but see below). Titratable acidity TA, on the other hand, measures the total amount of hydrogen ion available in free and bound forms. pH and TA both correlate to the tartness of the wine, but the kind of acidity the wine exhibits is generally more a function of its TA value. The pH value is important for taste as well, but more important is its effect on stability of wine, from the beginning of fermentation through to the final product. Very roughly speaking, we want our whites and rose’s to be in the pH range 3.1 to 3.4, while our reds are usually best in the range 3.3 to 3.7. And in general we’re hoping that our TA values are going to be 6 to 7 for reds and 6 to 9 for whites. Note that pH and TA of wines do not track each other in any consistent way. For example it’s possible for a low pH wine to have a low or a high TA value.
Tips on Measuring pH and TA
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For those us of in the northern hemisphere it is time we start getting ready for harvest season!
WineMaker Magazine has a great Harvest Check List in their most recent edition, written by Bob Peak. It is wonderfully detailed and a must read for all our customers. It is an all encompassing check list whereas ours will just scratch the surface. Our checklist reflects only what we do here at our own winery. What you do during your own harvest is up to you.
We always use a checklist to prepare and to ensure we have everything we need for a successful harvest. Our winery, Little Oaks Winery, is a small operation with a limited about of employees and we have found that preparing for harvest is essential for producing award-winning, memorable wines. Our winery is about four to five weeks away from harvest time. It’s time to start preparing.
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For years it has been said that the Ripper method for measuring sulfite (SO2) has one drawback: interference from “reductones”. These are substances that react with the iodine titrant as SO2 itself does, causing an overestimation of the true SO2 level. But as we’ll see below, this does not seem to be a huge problem with the Vinmetrica version of the Ripper method, and where encountered, it can usually be corrected for.
The Ripper method uses iodine or iodine-generating reagents to oxidize the SO2 in the test sample (primarily wine, but beer and cider are also examples). It relies on the quantitative reaction of iodine (I2) oxidizing the SO2 in the sample under acid conditions.
In this reaction, SO2 is acting as a “reductant” for the oxidant iodine. When all the SO2 is oxidized by iodine at the endpoint, excess iodine appears in solution. The Vinmetrica system detects this event as a sharp rise in electrochemical current with its SO2 electrode.
Anything in the sample that reacts like a reductant – called a “reductone” – in a Ripper titration will appear to be SO2, leading to an overestimation of the SO2 level. A well-known example of a reductone is ascorbic acid. Ascorbic acid (“AA”, also known as ascorbate or vitamin C) reacts with iodine just as SO2 does, that is
Ascorbic acid can be found in modest amounts in some vinifera varietals, and it can occur in high levels in a number of fruits, like citrus and some berries. When trying to measure SO2 levels in these samples, one must be careful not to get misled by ascorbate parading as SO2!
There are other things present in wines and juices that can act as reductones. In principle, reducing sugars (glucose, fructose) and various polyphenols could act as reductones.
How to correct for reductones:
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Vinmetrica Compares Well with Wine Testing Labs
Summary: Vinmetrica is participating in the CTS Wine Industry Interlaboratory Program this year. Along with 100 other labs, we tested two samples from CTS for up to 16 parameters. Using our products, we obtained results for free and total SO2, pH, TA, malic acid, and residual sugar that were in good agreement with those of the other participants.
We are pleased to report the first round of results from participating in Collaborative Testing Services’ (CTS) Wine Industry Interlaboratory Program for 2020. CTS (www.collaborativetesting.com) provides samples to, and analysis of the results from, participating laboratories in a wide variety of testing technologies. The Wine Industry Interlaboratory Program focuses on chemical and physical analysis of wine.
This last round of samples from CTS (“Cycle 065”) comprised two sweet red wines. About 100 labs across the US participated. The following parameters were available to be measured and compared: Total SO2, Free SO2, TA, pH, Residual Reducing Sugars, L-malic acid, %ABV, Specific Gravity, Glucose + Fructose, Copper, Potassium, A420, A520, L-lactic acid, Conductivity, and Methanol. We submitted results for all these except Copper, A420, and A520, the first because we don’t have the equipment for it, the latter two because we rarely perform them (though we can do so). Keep Reading More!