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.
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!
There are several reports comparing various methods for determining free and total sulfites (SO2). Aeration oxidation (AO) and Ripper titration methods (like Vinmetrica, Hanna, and old starch color change techniques) are the most commonly employed. In addition there are a number of methods based on spectrophotometric techniques or color reactions that have come into use in recent years. Here I want to focus on the performance of the AO and Ripper methods vs. others, and vs. each other.
We have generated lots of our own data comparing AO and Vinmetrica’s SO2 test, and we know without any doubt that, with the exception of exotic samples (like wines made from ascorbic acid-containing fruit), the Vinmetrica system produces results that are indistinguishable from those of the AO method. But I think it’s time to revisit the information that’s out there on others’ assessment of the comparison of these techniques. Keep Reading More!
As many of you know, Winemaker Magazine (WMM) is a great source of information and techniques for the serious home winemaker. This weekend many of us planned to attend the annual WMM Conference that was to be held in San Luis Obispo amid one of our favorite wine regions, the California Central Coast. In the interest of public health and safety, the meeting has been postponed. As of this writing, it is to be held next year May 20-23 in the same location. So we’re looking forward to that!
The Vinmetrica Team would have been at the WMM Conference to share information about our products and to learn more about your needs. We can’t all meet this year, but we can provide the same discount codes for a brief time as we do every year at the conference!
If you order anything on-line from Vinmetrica before midnight on Sunday, you can take 15% off your entire order by entering this discount code Keep Reading More!
On the quest to fashion the best wines, we make multiple measurements to ensure that our wine ferments and ages properly. We know that it’s important to keep our SO2 levels up; knowing the pH and acidity of the wines is essential to SO2 management as well as proper stability and flavor. If we’re doing malolactic fermentation, we need to measure malic acid to know when that step is complete.
At some point prior to bottling, you’ll likely want to know the levels of residual sugar (RS), as this will impact your preparation for bottling. If you’re selling your wine, you need to measure your wine’s alcohol by volume (ABV); and even if it’s for your own use, it’s good to know the alcohol level, if for no other reason than to be able to prove you are on top of your process from vineyard to bottle. In the last few years, Vinmetrica has released two new kits for assessing these post-fermentation parameters. The Residual Reducing Sugar test and the Vinmetrica ABV kit are accurate and simple procedures for home winemakers and small wineries. Keep Reading More!
By now you know that Vinmetrica has the reputation for providing simple, low cost, fast and accurate tests for winemakers…tools that let you make the best wine you can. In this installment of the winemaker’s blog, we’d like to give a brief account of our origins. Keep Reading More!
I’m sure many of you are familiar with the technique of malolactic fermentation (MLF), typically carried out in most red wines and in some white varietals. MLF plays an important role in the finished wine’s feel and taste. MLF reduces titratable acidity, increases pH, and produces flavors often characterized as “soft” or “buttery”. In addition, carrying out MLF before bottling prevents an unintended development of carbon dioxide gas (CO2) due to MLF starting up in the bottle, which can lead to fizzy wine, or worse, exploding bottles! Keep Reading More!
As many of you know, Vinmetrica shares a warehouse space with our sister company Little Oaks Winery. After years of private winemaking, our president Rich decided it was time to turn his garage operation into a business. We have grown from a one barrel, garage operation to a small winery producing about 350 cases a year.
Our winery has anywhere between 18-24 barrels at once and we were looking for a more efficient and cost effective way to clean our barrels and tanks after bottling. We followed all the usual methods and found that we were either using up too much water, potentially adding odd flavors to our barrels from the use of harsh chemicals, and we weren’t exactly sure if our barrels were getting clean. It dawned on us that we needed to find a better solution, and fast. We eventually determined that barrel steaming was the best way to go.
Vinmetrica at the Winemaker Magazine’s annual conference. June 1-3 2017, Ithaca, New York.
Vinmetrica was at the Winemaker Magazine Conference, held at the Statler Hotel on the Cornell University campus, amid the beautiful Finger Lakes Region of upstate New York. Every year the conference hosts hundreds of wine and cider enthusiasts who are passionate about their craft. As always there were numerous presentations and workshops on vineyard practices, wine making, and of course, quality management Keep Reading More!
Introducing one of Vinmetrica’s newest products: the Dissolved Oxygen (DO) Probe, a tool for fast and accurate measurement of dissolved oxygen in your wine. Why measure DO in your wine? Oxygen plays a major role in winemaking, having both good and negative effects on the final product. Dissolved oxygen is helpful in small amounts, but too much could lead to an undesirable bottle of wine. By just taking a few measurements you can quickly take control of that. Keep Reading More!