We’ve been getting a lot of buzz from cider makers the past few weeks asking if our units can test SO2 levels in cider, and they do! We have several customers that use our various instruments to test their cider for SO2 with great success. Using the same method as found in our product manuals, you can test your cider for SO2 the same way you would test your wine!
How does the Vinmetrica SC-300 SO2 and pH/TA Analyzer Kit compare to other Free SO2 testers on the market? Daniel Pambianchi has done some benchmark comparisons between several Free SO2 testers available. He has created a full report outlining the methods, results and his conclusions. Thank you Daniel for your report. We are happy to share this with our customers.
To view the full report, click here.
By now you may have heard that we just released our newest product, the SC-50 MLF Analyzer. We have been working on this for nearly two years, mainly to be sure that the product is easy to use, reliable and accurate. The approach we took was to have the device measure the increase in CO2 pressure that occurs when malic acid is converted to lactic acid, a process we call ‘Biopressure’. This increase in pressure is then converted to an electrical current that the SC-100 or -300 SO2 analyzers can pick up and display. Pretty simple really, but the devil is in the details as they say. And quite honestly we expect the methods (but not the hardware) to improve over time as we learn new ways to make it even faster to use.
They idea of using pressure to measure malic acid in wine is not new in itself. Over 50 years ago, George Kolar of the Australian Wine Research Institute published an article entitled “Manometric Determination of l(—) Malic Acid in Grape Musts and Wines”* that described a method adapted from earlier biochemical research. This method was adopted widely during the 60s, but was eventually displaced by other analytical techniques, most notably the paper and liquid chromatographic methods, and enzymatic spectrometric assays. All of these later methods were either simpler (paper chromatography) or more accurate and suitable for commercial laboratory use. In contrast, the manometric (i.e., based on measuring gas pressure) method, while sensitive and accurate, involved complex glassware and a good deal of professional training to execute.
We believe that the SC-50 incorporates 21st century technology that makes it a pretty good manometric device that is easy to use; the Biopressure agents, reagents, and methods we have developed over the the last 2 years give Dr. Kolar’s technique an entirely new lease on life. You should be able to complete a few or a few dozen tests in 30 minutes, something that would have taken him (or probably his graduate student, poor soul) hours and hours, 50 years ago.
*Am. J. Enol. Vitic 1962 vol. 13 no. 3 99-104 http://www.ajevonline.org/content/13/3/99.abstract
Vinmetrica specializes in wine testing equipment, but did you know that our instruments can also be used for beer making as well as distilling spirits? During the distillation of whiskey, the water used is the most crucial liquid used for production. It is vital to have water at the proper pH in order to smoothly run through the distillation process of mashing, fermentation, distillation and maturation. All good whiskeys start with the use of good quality water. The water needs to be at the proper pH, lower than pH 7, which is crucial for starch conversion. A distiller must also monitor the pH of the mash. The American Distilling Institute discusses the importance of obtaining and using a good pH meter in their paper, The Craft of Distilling Whiskey (http://www.distilling.com/PDF/craftbook.pdf).
A few months ago a customer purchased one of our SC-200 Kits in the hopes of using it for his up and coming distillery located in Berthoud, Colorado. Being in the heart of one of the largest craft/micro-brewing regions in the United States, the opening of K J Wood Distillers was a nice change and the owner, John Wood, was very welcoming. We always like checking in with our customers but the opportunity to visit one was a special treat. Their grand opening celebration took place on June 27th at their distillery. They offered several types of Gin cocktails ranging from a cucumber soda fizz to a cocktail with habanero peppers. I have never actually tried Gin but have heard that it can be a bit hard to drink. Their “Jinn Gin” was phenomenal. Yes, phenomenal!
During the celebration I was introduced to John’s neighbor who owns a winery, Sweetheart City Wines. After some casual discussion about wineries and wine-making in general, I was taken into his winery itself and given the grand tour. Come to find out he is one of our original customers and owns the original model of the SC-100. These two neighbors both own Vinmetrica SC series systems! One for a winery and one for a distillery. What are the chances of that?
Taylor had a wonderful time visiting K J Wood Distillers and seeing Colorado. I can’t wait to try the whiskey and I hope that their Vinmetrica SC-200 helps them make the best whiskey out there. Thank you to all our customers; from the wineries to the distilleries.
Vinmetrica knows what it takes to make a great wine; it takes hard work and proper testing techniques. Eventually we all learn how to become sommeliers, because, let’s face it, we all like to taste test our wine too! We started Vinmetrica with a desire to make quality devices for wine makers that are accurate, easy to use, and affordable. This stemmed from the fact that we are wine makers ourselves. We have been making wine for many years and we decided to enter two of our wines in the wine competition at the San Diego County Fair.
Our 2009 Merlot was made at home as our first trial with Oak barrels from grapes grown in El Dorado County. This wine received the Silver medal from the San Diego County fair. Our 2011 Merlot was made here at Vinmetrica using grapes from Ramona Valley. We were awarded the gold medal and were given the honor of being the “Best in Class” this year. We attribute our success to regularly testing for sulfite and other analyses for both wines. Rich was surprised and thrilled at the news!
The awards ceremony was on June 29th where Rich received his awards. He was able to taste some of the 300 highly qualified entries in the competition as well as taste locally made cheese. The event was well organized and it was great to see some of our customers thriving in the competition.
We hope to see you all again next year!
Did you know that if you plan on exporting your wine, you are required to present a specific chemical analysis? Vinmetrica is here to help! After a long testing and analysis process, Vinmetrica now has TTB certified laboratory technicians!
The process to obtain this certification was not an easy feat. The Alcohol and Tobacco Tax and Trade Bureau provided us with two standard wine samples, one red and one white. Being TTB certified gives our customers the piece of mind that their wines and spirits are being analyzed properly and according the the industry standard. Some of the analyses we performed for the certification were alcohol by volume, acetic acid, residual sugars, free sulfite, and methanol.
Vinmetrica provides services that give wine makers the confidence that their wine production is running smoothly. Our TTB certification gives you the assurance that our analytical methods are held to the highest standards.
See you in two years TTB!
Malic Acid Test Kit
Vinmetrica is focused on quality, low cost, easy-to-use products for winemakers. That is why we are proud to be introducing our next product this summer. Malic acid testing is notoriously tedious, but we have a better answer. Get ready to free yourself from paper chromatography! Vinmetrica is currently moving into beta testing for the new Malic Acid tester, which will be an add-on for the Vinmetrica SC-300 (and we are working on compatibility with our other units as well). How much time will it save you? In 30 minutes, you will have a quantitative result that lets you know how your malolactic fermentation is going. How easy is it to use? Put your wine sample in our container, cap it and shake, set it aside for 30 minutes and then come back and take a measurement. Simple as that! No toxic volatile chemicals, no waiting to develop paper chromatography, and no mess!
The Vinmetrica analyzers have been revolutionizing wine making practices for the past three years. In the course of product development, we have generated capacity to perform the tests most commonly needed by winemakers. Need to perform a specific test but don’t have the equipment? We are now offering laboratory services for winemakers so they can focus on creating high quality wines. Check out our services page at vinmetrica.com/services for more details. We offer over 20 analyses at reasonable prices. Our services will be performed following the rigorous AOAC and TTB approved wine analysis methods. We are currently being TTB certified. We are offering, for a limited time, a 10% discount on all our laboratory services, upon checkout type in the discount code ‘VINMETRICALABS’ for instant savings!
What’s coming up next from Vinmetrica? Research and development is always ongoing and we have new products in the pipeline for measuring alcohol by volume and residual sugar. Make sure to check out our blog for the latest updates here on our blog, or sign up for our newsletter on the left
At Vinmetrica, our products and services come with a personal touch: we’re winemakers ourselves. With our background in analysis and our passion for making great wine, we believe we can provide the best products and services that any home winemaker or winery could need. Feel free to call us if you have any questions; our technical support and sales team is standing by Monday through Saturday 9am to 6pm (PST)!
A lot of people have asked me, “Hey Rich I have my Free SO2 results, now what do I do with it?”
Now that people are more often testing their sulfite levels in their wines, the results need to be used to the winemaker’s full advantage in protecting their wine from oxidation and spoilage. I would like to bring up the sulfite (SO2) adjustment process since the results gathered from the SC-100, SC-100A or SC-300 need to be crunched by hand or by a calculator to determine how much, if any, sulfite needs to be added to your wine.
How to adjust your sulfite levels: testing and calculating.
Whenever you move your wine from one container to another, or when you are preparing to bottle your wine, it’s important to check and adjust your sulfite (SO2) levels. What is the right level? It depends on the pH of your wine. The key parameter in protecting wine is “Molecular SO2” which for most wines following primary fermentation, should be at 0.8 ppm (mg/L). This in turn depends on the “Free SO2” (it can also be referred to as “unbound” SO2) and the pH, both of which can be measured with the Vinmetrica wine analyzers. Overall, you can reach your target Molecular SO2 by measuring and adjusting your free sulfite levels and considering your wine’s particular pH.
Measuring SO2: the Vinmetrica SC-100A and SC-300 help you to do this with confidence. But whatever methods you use, keep a few things in mind.
The key thing to check is accuracy. How do you know if your results are accurate? If you are using Aeration oxidation, you need to be sure that your NaOH titrant is standardized. A solution of sodium hydroxide loses strength over time because CO2 in the air reacts with it. Similarly, the 0.02N iodine solution that many use for Ripper titrations can undergo significant loss over time, even a relatively short period of time like 6 months. For Ripper-based methods, you can use the vitamin C trick that we recommend for Vinmetrica’s SO2 tests (although these are generally run for confidence-building, as it turns out that our reagents are very stable.)
But, you might ask, why not just make a standard solution of, say, 50 ppm SO2 from metabisulfite and analyze that to check accuracy? In principle you could do this – for example, you could weigh out fresh potassium metabisulfite (K2S2O5) accurately and dissolve it in pure water to make a 1.0% solution. This would be 10 g/L * 0.57 g SO2/g K2S2O5 = 5.7 g SO2/L = 5700 mg/L = 5700 ppm SO2. Then you could dilute this 100-fold in pure water to make a 57 ppm test solution. Here’s the problem: unless meticulous measures are taken, “pure” water is usually saturated with atmospheric oxygen, and at room temperature this level is about 8 mg/L. Each mg of oxygen will react with 4 mg of SO2, so at 8 mg/L, our water can already eat up 32 mg/L of SO2. Thus our 57 ppm (57 mg/L) SO2 solution will quickly become as low as 25 ppm. As you can see this conundrum is what brought us to use and adopt the vitamin C trick to check our SO2 reagents.
So go ahead, measure the pH and take your Free SO2 result, both can be measured with the SC-300. Make sure to write this info down! Now then, typically, if you have a higher pH wine (lower acidity), you need to add more sulfite (SO2) to achieve the Molecular SO2 level of 0.8 ppm (mg/L). The Table and graph below show the relationship between pH and Free SO2 to achieve this 0.8 ppm (mg/L) Molecular SO2. The Free SO2 on the left side of the graph indicates the Free SO2 you will NEED to achieve 0.8 mg/l Molecular SO2 in your wine. This will be made up of the Free SO2 you currently have now plus whatever you may need to add. So if your Free SO2 results (measured using Vinmetrica’s method or an alternative method) matches the Free SO2 level on the graph or table at your known pH, then you are good, no need to add more sulfite at this time. If it is not you just have to work a little harder to get it there. If your Free SO2 results are below this Free SO2 level you will need to add some sulfite to achieve this level of antimicrobial & oxidative protection for your wine. The amount you add can be determined with a sulfite calculator, which we will talk about next.
The Graph above shows the relationship of Free SO2 and pH required to achieve the 0.8 mg/L Molecular SO2. Molecular SO2 is the active form of Sulfite (SO2) which will protect your wine from oxidation and spoilage.
Table of Free SO2 concentrations necessary to attain 0.8 mg/L Molecular SO2 at a designated pH.
|pH||Free SO2 ppm (mg/L)|
Wait I have to do this by hand? No fear not, that is what the sulfite calculator is for! Winemaker Magazine’s website provides a great calculator and except for some tweaks, which we will talk about below, the instructions are pretty clear.
Once you know your sulfite levels, it’s easy to make any adjustments that may be necessary. The table and graph above is there to guide you in this, but we always like to use the sulfite calculators that are available for download or on the web as applications. My favorite is the Winemaker Magazine Sulfite calculator on the web:
This is easy to use and is accompanied by a nice guide. However a few notes are in order:
1. I highly recommend you choose (and use) “10% Sulfite Solution” from the drop-down menu next to the prompt “Preferred method of Sulfite addition”. (The guide tells you how to prepare the 10% solution. The sulfite solution we’re talking about is potassium metabisulfite (KMBS), though if you choose to use sodium metabisulfite or other sulfite forms, the accuracy is not too bad.).
2. Choose the wine type (red or white). Keep the desired molecular SO2 at 0.8 and enter your wine’s pH value (hit your keyboard’s “Enter” button after entering the value).
3. This is the one step that is not obvious at first (at least it wasn’t to me). After you enter your wine’s pH and the molecular SO2 level, you will see a recommended free SO2 level in the “Notes:” section, just below the entry fields. Enter this number in the “Desired level of free SO2” field. If you don’t see anything in the “Notes” section, enter a “guess” number higher than your current level in the “Desired level of free SO2” field (and see step 6!).
4. Next you enter the “Current level of free SO2” (What you have just measured), and the “Volume of wine to be corrected”, being sure to indicate liters or gallons as appropriate.
5. Now by pressing the “Calculate” button below, you should see a figure under “Amount of sulfite to be added in milliliters (if you used Liters for the wine volume) or fluid ounces (if you used Gallons).
6. If you entered a “guess” number in step 3, you now should see the recommended level in the Notes: section – so enter this and repeat the calculation.
Simple as that! Now that you have protected your wine from oxidation and spoilage, seal up your container and take a siesta. But remember to check your wine for sulfite regularly, especially after you transfer your wine to a new container or are about to bottle!
In the effort to create high quality wines, it is critical to maintain proper free sulfur dioxide (SO2) levels during all steps of the winemaking process. Keeping SO2 levels at optimum values is key to preventing the discoloration, off-flavors and unpleasant aromas resulting from oxidation and microbial contamination. Suffice to say that all those award winning wines going for $200 a bottle or more have the correct levels of sulfites added to them!
The problem with the task of maintaining SO2 levels is the tendency for this component to disappear over time. The SO2, typically added as a sulfite like potassium metabisulfite, undergoes an equilibrium between free and bound forms which is pH- and temperature-dependent. In addition, oxidation by atmospheric oxygen continually reduces SO2 levels especially when the wine is briefly exposed to air as occurs during racking and bottling. Therefore it is important to have a reliable method handy for measuring free SO2.
There are Several Approaches one can take to determine free SO2. However, as a large number of winemakers rely on the simple Ripper titration, we thought it a good idea to elaborate on the virtues and cautions of using this method.
In the Ripper titration, standard iodine is titrated into an acidified wine sample. The iodine reacts with free SO2, and when the SO2 has all been titrated, free iodine appears at the endpoint. Originally described in 18981, the original Ripper method is fast but its accuracy and precision are notably poor, primarily because it relies on the appearance of a dark blue starch-iodine complex to detect the end point, which is difficult to see (especially in red wines) and subject to errors of interpretation2.
However, the method’s speed and simplicity are attractive; many winemakers have claimed that they can train themselves to read the endpoint reproducibly.
Some modifications to the Ripper method improve the reliability of detecting the endpoint. For example, the use of electrochemical sensors that respond to the appearance of free iodine removes the burden of trying to visualize the starch endpoint against a dark background in red wines.
The Hanna Instruments autotitrators like the HI 84100 (also sold by Milwaukee Instruments) use the ORP electrode in an automated device. This electrode relies on a change in the oxidation status of the solution that occurs as free iodine appears. Vinmetrica’s SC-100 uses an amperometric probe to detect appearance of free iodine. This provides robust, sensitive results that compare favorably with other methods.
There have been numerous reports describing the various sources of potential error and interferences in the Ripper method. The acidification step (also required in some other methods) induces slow dissociation of bound SO2 to form more free SO2, leading to a systematic overestimation of free SO2. This effect can be minimized by performing the Ripper titration quickly (within 2 minutes), such that it probably contributes less than a few percent error.
Another source of error that can lead to overestimation of free SO2 is the presence of other oxidizable compounds in the wine. These can react with the iodine titrant, again leading to overestimation of the SO2 level. In some white wines, there are appreciable levels of ascorbic acid which react readily with the titrant. In red wines, the presence of phenolic compounds can also lead to overestimation.
In this case the error may be estimated by a modified Ripper method3 in which duplicate samples are titrated, one having been pretreated with a drop of 3% hydrogen peroxide, the other untreated. The difference between the two values provides an estimate of the “true” SO2 ppm value (since peroxide primarily removes only the free SO2).
In our hands, using the Vinmetrica SC-100 (or the SC-300 in SO2 mode), we have not seen significant differences between the “true” and uncorrected value of free SO2 in the wines we have worked with to date. This implies that phenolic compounds are not significant sources of interference with Vinmetrica instruments.
Indeed, the aeration oxidation (AO) method, which is theoretically free of these interferences, has been shown in one independent study to give identical results to those of the SC-1004 . Although it seems to be generally accepted that Ripper methods produce higher values and are less accurate5 than other methods, it is possible that the Vinmetrica’s improved endpoint detection may change this perception
In summary, the Ripper method is quick and can be made reliable and accurate enough to guide the winemaker in maintaining proper levels of sulfur dioxide. The SC-100A and SC-300 are simple and inexpensive SO2 meters for accurate SO2 analysis.
1 M. Ripper, Die Schwelflige Saure im Wein und deren Bestimmung, J. Praia. Chem. 46, 428-73 (1898)
2 James E Vahl and Jean E. Converse, Ripper procedure for determining sulfur dioxide in Wine: Collaborative study. J Assoc Off Anal Chem 63, 194-9 (1980)
5 J.W. Buechsenstein and C. S. Ough, SO2 Determination by Aeration-Oxidation: A Comparison with Ripper (1978) Am. J. Enol. Vitic. 29:3:161-164
…continued from “How It All Began“.
In July of 2008, a year after my former company (Molecular Devices) was acquired, my position as Vice President of reagent R&D was phased out. Soon after that I was able to wrap up my affairs in Palo Alto and join my wife Marcia in Encinitas near San Diego, where we had conducted a commuting marriage for the last 7 years.
Jobs were not plentiful at that time, especially in my field. I started Sportsman Consulting and had a few clients, but it wasn’t much. I also worked on a startup called Ascent Biosciences, but in December of 2009 the company moved away.
I talked with my wife about the sulfite meter. She encouraged me to pursue it. About this time I decided to open a lab in some space within a warehouse that I rented from a friend of mine in Carlsbad. Sportsman Consulting had just enough income to pay the rent. I built a simple prototype sulfite meter and sent it to Dave Donofrio, a former colleague of mine who had been a marketing director at Molecular Devices, and who is a serious winemaker in the Santa Cruz mountain area.
Dave had just purchased a Hanna 84100 autotitrator himself, after struggling for years to keep his sulfites under control by other methods. Dave endorsed my idea of a simple and accurate sulfite test and agreed readily to be the first guinea pig. Dave did some comparisons and reported that the prototype gave results that were quite close to the Hanna. (Dave is now advising Vinmetrica on Marketing.) Dave suggested that we could support a sales price that would make a viable business.
We went on from there. I retained Bill Ewing after seeing his name on the San Diego Electrical Engineers web site. I picked him because he lives nearby me in Encinitas. But what a lucky choice that was!
Bill was enthusiastic from the start and we hit it off right away. We put together the SC-100 prototype in about 4 months. In the meantime I worked out the details of the chemistry to make it a stable product, and found a manufacturer that could make the electrodes to my specification.
More comparative data was forthcoming. Dave really liked the new prototype and showed it to some colleagues in the winemaking business, and I began to get some feedback from other winemakers.
One of my first early demos was with three Ramona Valley winemakers who were getting ready to bottle their Merlot. We did a side by side comparison between the SC-100 and their manual Ripper method.
The way they did their assay was illuminating: take a 10 mL wine sample. Dilute it with about 100 mL of water. (Gasp! You’re going to make the endpoint very fuzzy!) They explained that by so diluting it, they could reduce the opacity of the red color to see the blue endpoint better. They added starch and acid in the usual way.
Then they took a 10 ml graduated pipette and filled it to the zero mark with 0.02N iodine. (Gasp! This is your burette?!). They then titrated from this pipette. It took 0.3 mL to reach an endpoint that they all agreed to after some squinting. This calculated out to about 20 ppm of free SO2.
At the same time, I did an assay on a 25 mL sample in the usual way using the SC-100. I determined 6 ppm.
We talked about this, and they agreed to repeat their method, this time using a 25 mL sample. They titrated to the endpoint that they felt was correct: also 0.3 mL (mind you, reading 0.3 mL off a 10 mL pipette isn’t exactly giving yourself much resolution!) Hmmm. But of course now the calculation gave 8 ppm, since they had taken 25 mL instead of 10 ml wine.
Then I suggested we check the strength of their iodine solution. I produced a vial with pre-weighed amounts of ascorbic acid – I use these as a quick check of my SO2 Titrant and they are accurate to 5%.
Turned out that their 0.02N iodine solution, which was near its expiry, was actually 0.015N. So their 8 ppm was actually 6 ppm, and in fact we had numbers that agreed exactly!
With several examples like this under my belt, I knew we were ready to release the SC-100. Our assessment of the competition showed that inexpensive sulfite tests available for winemakers were not practical.
Chemetrics Titrets don’t work in red wines (according to the manufacturer).
People report struggling to use the test-strip indicator kits offered by some competitors. Aeration-oxidation (AO) is time consuming and somewhat complicated.
Other options were sending out samples for analysis (~$20 a pop) or buying an autotitrator of some kind ($600 or more and significant yearly maintenance.) And even the autotitrators require calibration each time you use them, adding significant time to get the job done.
In the 18 months since we released the SC-100, we have sold over 500 of them. I think this is a testimony to our commitment to bring low cost, simple and fast testing to winemakers. Most importantly, what we hear from our customers is satisfaction.
“I love my Vinmetrica”
“My autotitrator is now a door stop!”
Now we are on the next adventure. With the release of the SC-200 and SC-300, we have added pH and TA measurement to the product line. The SC-300 is great for those who want to get reliable testing for pH,TA and SO2 without spending a fortune and sacrificing large amounts of bench space.
I’d rather see you spend your money on some new oak barrels!
We will continue to be in the business of quality products for wine testing. In the works is a test for malic acid. We hope that the malic acid test is as simple and affordable as SO2 now is through Vinmetrica!