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The Vinmetrica Dissolved Oxygen Probe

by Rachel Speck

Vinmetrica’s New Dissolved Oxygen Probe

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.

The Vinmetrica DO probe works via the pH function on an SC-200 or 300.  For those of you with firmware version x.1.1 and above, a millivolt (mV) mode option to pH is available.  Either function works, but for our purposes I worked with mV mode. To use mV mode all you do is turn on the instrument, put it in normal pH mode, then hit the Mode button one more time. The pH LED should now be blinking; this is mV mode. Set-up for the DO probe is relatively simple; before using it for the first time you must add electrolyte solution that goes in between the membrane and zinc anode. Unscrew the cap and, using a syringe or pipette, fill it as directed with the provided electrolyte solution.  Screw the cap back onto probe, attach the probe to the instrument via the BNC connection, select the desired mode, and you are ready to go!

In simple terms, the probe works by allowing oxygen to pass through its membrane where it creates an electrical current between a cathode, electrolyte solution and anode, much as a battery does.  This produces a change in electrode voltage that the instrument measures. The calculation for the DO probe is also very simple. By using known values for a 100% O2 saturation (open air) and a 0% O2 saturation ( a sodium sulfite solution) you can calculate your wine’s percent DO. The calculation looks like this:

%DO= 100*(Wine Sample-0% standard)/(100% standard-0% standard)

The testing process also is really simple. With the probe attached and the instrument on, take your 100% reading; record the data.  Again, this is just letting the probe sit out in open air.  Now make your 0% standard, by adding about 750 mg to 1 gram of the provided sodium sulfite to 2 mL distilled H2O. (This is a saturated solution in which solid particles are still visible and do not dissolve.) Stick the probe in this solution and gently keep the solution mixing. The number will start to drop in mV mode (or go up if using pH mode). As I have seen, it drops rather rapidly at first but takes 3-4 minutes to finally reach its end point which is typically between 8-13 mV (6.5-7.0 in pH mode). Record the lowest value for mV mode.

I have been using our DO probe in the winery, so I thought it would be interesting to share some typical results. First I took some measurements on a 2012 bottle of wine that was made and bottled by Dr. Rich Sportsman in 2012.  I tested different methods. First I stuck the probe directly into the bottle. I have found that the probe reaches its final value faster if you gently mix/stir the probe in the solution.  I next tested the wine by taking out a 2mL sample, placing it in a small tube, and then measuring the DO.  I then took the 2 mL sample and bubbled air through it for 30 seconds and measured the results.

 

Sample or Standard mV %DO
100% (open air) 258
0% (sulfite solution) 12
Bottle 46 13.8
2 mL sample in tube 72 24.4
2mL +air 243 93.9
2mL + nitrogen 49 15.0

As you can see the DO probe shows a large difference between the 100% saturation and 0% saturation. The data also follows what you might expect. The bottle has relatively low DO, but as soon as you take out a small sample into another container, the wine immediately starts picking up oxygen. This data allowed us to come to the conclusion that for the most accurate DO measurement, it is best to place the probe directly into the wine container.

Now I wanted to see what wine DO levels looked like in younger wines. I went through and measured some of our 2015 containers.  For cleanliness, I sprayed the electrode with a 50% ethanol solution and gently wiped the probe with a cleaning tissue before putting the probe into the wine. Also, all the wine had been sparged with nitrogen the day prior. Here are the results.

Sample or Standard mV %DO
100% 299
0% 9
2015 Syrah 24 5.2
2015 Barbera 19 3.4
2015 Malbec 17 2.8

We are pretty happy with these numbers at this point. I will keep checking to make sure these stay stable and do not pick up excess O2. At the very least it will now be very interesting measuring dissolved oxygen, seeing how and if it changes, and later seeing its effects on the wine.

Of course, one very important use we foresee for our DO probe is verifying that levels of DO are below about 10% saturation at bottling time.  This should prevent unwanted effects of excess oxidation on taste and sensation of the finished product.

You can check out the manual for the Dissolved Oxygen Probe here.

Dissolved Oxygen Probe Product Page

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The Wine Analyst

The Wine Analyst

My career has been one of analysis. Yes, I’m one of those analytical types who dissects much of his daily experience into subjects for further investigation. Never could really get the hang of politics, religion or film criticism, but I do take an almost indecent interest in the technical workings of things. That curiosity led me into a career as a Ph.D. analytical chemist – and ultimately, into wine analysis, and making products for that endeavor.
As a 20-year veteran amateur winemaker, I knew there were better ways for home winemakers (and small wineries) to get the basic chemistry information they need for their craft. High on the “annoyance list was sulfite analysis. From desperately slogging my way through color test strips and unreliable Ripper set-ups, both commercial and homemade, I was motivated to find a better way to get that information.

I think it’s fair to say that we succeeded in making a simple, affordable SO2 analysis kit, starting about 5 years ago. Now we have a series of products that get you 5 important parameters: SO2 (free and total), pH, TA, malic acid (for MLF), and residual sugar. We are trying to make a simple ABV test as well, but it doesn’t meet our requirements yet, so no go until it does.

There are some other things though, that you can do with our equipment, so in this blog I’d like to tell you a little about them. These have to do with the pH measurement functions on our SC-200 and SC-300.

Measuring potassium and sodium (and other simple ions):

The latest versions of our firmware (X.1.1 or higher, where X is 2 or 3) for the SC-200 and SC-300 instruments allow you to use the pH capability in a slightly different way. Instead of attaching a pH probe, you can attach one that responds to potassium or to sodium. These so-called ion selective electrodes (ISEs) put out a voltage that is proportional to the sodium or potassium ion concentration, just as the pH probe does for hydrogen ion.

In the potential mode (which we inserted between the pH and TA modes on these instruments) the readout will now be in millivolts. To analyze sodium or potassium, you prepare standards (as well as your samples) in a special buffer that ensures that the readout is not affected by changes in other ion concentrations, or by pH. Then you just put the electrode in and read out the voltage. A simple calculation allows you to relate the voltage response of the standards to the concentration of the sodium or potassium in your sample. It all works very well!
Here is some recent data on potassium (K+ for short). We used a potassium ISE from Van London pHoenix Co.

potassium electrode graph

The slope of this line is in agreement with the manufacturer’s specifications (56 mv/decade concentration, 58.1 theoretical at 20C)

potassium electrode data

The potassium electrode gives good data in a wine sample, as the table above shows. A red wine sample was run undiluted and at 4 dilutions. The numbers ranges from 44 to 35 mM, but at dilutions of 2-fold and higher, there is less than 3 mM (10%) difference. Note also that three of the dilutions are 37 +/- 1 mM , which equates to 1460 mg/L of potassium, a value not unusual for a California wine.

Measuring Dissolved Oxygen:

You can also measure dissolved oxygen (DO) with the new version of the firmware. A galvanic DO probe is pretty inexpensive, and it attaches to the pH probe position. It puts out a voltage that is proportional to %DO. You calibrate it with water standards: a 0% DO (saturated sodium sulfite that eats up all the oxygen) and a 100% (i.e., air-saturated) DO standard. Then just dip the electrode in the sample; the readout can be converted simply into %DO.
Other electrodes:
there are ion selective electrodes for a large number of substances, including calcium, magnesium, “water hardness”, CO2, nitrate, fluoride, chloride, copper, silver, lead, and “redox potential”, just to name a few.

If you are interested in any of these, let me know. I would be happy to set you up with the source for ISEs, reagents and the protocol – and if there’s enough interest, we could begin to offer these for routine sale!

At Vinmetrica, we are always looking for new ways to improve the utility of our products. If there’s something you’d like to analyze, let us know.

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Say Goodbye to Paper Chromatography – Malic Acid Tester & Vinmetrica Labs

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!
   
Vinmetrica Services
 

Vinmetrica now offers quality Laboratory Services!
Vinmetrica now offers Wine & Beer Laboratory Services!
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!
   
Product Pipeline
 
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)!

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Sulfite Adjustments: What to do with my SO2 results?

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)
3.0 13
3.1 16
3.2 21
3.3 26
3.4 32
3.5 40
3.6 50
3.7 63
3.8 79
3.9 99
4.0 125

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:

WineMaker Magazine Sulfite Calculator

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!

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The Ripper Titration: Recent Improvements in Measuring SO2

handrawing of an old wine barrel

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.

Other references:
A summary of an ASEV meeting discussing a comparison of methods
Capillary electrophoresis vs. AO vs. Ripper
More SO2 stuff; good overview.

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)

3 http://www.gencowinemakers.com/docs/Measuring%20Free%20Sulfur%20Dioxide.pdf

4 https://vinmetrica.com/Souder_Eval.pdf

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

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An Encouraging Start in the Wine Analysis Business

hand drawing of grapes on a wine barrell

…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.

“Great product!”

“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!

Rich Sportsman Junior drinks from a remarkable big barrel of wine
Wine is Big in Brazil!

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!

 

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How It All Began

"a line drawing of grapes being crushed"

I founded Vinmetrica in December of 2009 on the belief that I could put together products that would help winemakers like me.

This belief  crystallized over several years and several events.  In 1993 I moved to Palo Alto with my family after living in Indianapolis for 8 years working as a research scientist at Eli Lilly.

We bought a house that had a venerable apricot tree in the back yard.  This tree was probably a remnant of the fruit orchards that used to occupy most of the Silicon Valley area in the early part of the 20th century.

apricots in a tree
Too Many Apricots?

It was a very productive tree, and after making several cases of apricot jam one summer, I still had several pounds of apricots.

It occurred to me to try to make wine out of them.   It wasn’t long before I was fussing over 5 gallon batches of apricot wine, and gradually I found myself learning the ropes of fermentation chemistry.

Over the succeeding years I graduated from fermenting fruit to condensed juices, then to wine kits and finally grapes (though I still like the dry apricot wine one can make from sugar, water and halved apricots).   Inevitably I was confronted with the task of measuring my sulfite levels.

Now, as an analytical chemist by training, I understood the basics of measuring sulfite by iodometric (or “Ripper”)  titration.  You take a measured quantity of wine, add acid and starch solution, and titrate with an iodine solution of known strength until the color turns blue.

My local winemaking supply guy recommended the Chemetrics Titrets(r) which essentially minimize this procedure into handy measuring ampoules.  Despite the manufacturer’s admonition that these are not suitable for red wines, I kept trying to use the Titrets for a whole winemaking season before finally giving up.  You just can’t see the blue endpoint reproducibly.

Next I went on to doing the full Ripper method with starch.  But again the red wines defeated me. As a scientist I had to admit that I would be fooling myself in claiming that I could see that endpoint in any kind of reproducible way.

I remembered the iodine titrations I did as an undergraduate.  In the experiment we determined the endpoint via a cobbled-together battery-powered electrode system with a microammeter as a readout.  I recall remarking to my professor that I could see the faint yellow iodine color about the same time that the meter started to indicate.

I asked my professor,”Couldn’t you just use the color as the endpoint?” He quipped, “Oh sure, Rich; even better, we could just add some starch and it would turn deep blue!  But the point of the experiment is to make you aware that you can use electrochemistry to detect the endpoint. “

So I thought I would cobble together one of these as best as I could remember.  Two platinum electrodes from ah, disused equipment at work, a few components from Fry’s Electronics, and an output that I read with my voltmeter.  Wasn’t much to look at, but I found I could get reproducible results in minutes.  This was about 1995.  I used this setup for years in my garage.

Little did I know what I was getting myself into…