Category: Fresh Off The Press

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!

Malolactic fermentation uses the beneficial bacterium Oenococcus oeni  to convert malic acid to lactic acid, with CO₂ being the byproduct of the reaction.

Malic Acid                       O. oeni           Lactic Acid      +    carbon dioxide

HOOC–CH₂–CH(OH)–COOH      CH₃–CH(OH)–COOH  +  CO₂

Sulfite, as free SO₂, inhibits the bacteria that carry out MLF.  Therefore free SO₂ levels must be kept low during MLF, carrying risks that the wine is left unprotected against oxidation and microbial contamination.  As soon as MLF is done, then, SO₂ should be raised to appropriate levels for protection of the wine.  Thus it is important to know when MLF is done, and the best way to do this is to measure malic acid levels in the wine.

Should I do MLF?

This is really a matter of choice that depends on your taste.  These days virtually every winery takes its red wines through MLF.  The mellowing tendency of MLF brings out the flavors and complex notes in red wines that are barrel-aged for months and then rested after bottling for a year or more.   Increasingly, white and rosé wines are not taken through MLF, to preserve the crisp flavors and floral aromas that would diminish at the higher temperatures (>70F) needed for MLF.  However, some winemakers prefer the mellowing, buttery flavors introduced by MLF into, say, a Chardonnay or a Muscat.

If you choose NOT to do MLF, bear in mind that your wine may decide to do it for you at any time.  If you keep your SO₂ levels properly adjusted, you should not have a problem with spontaneous MLF during bulk/barrel aging.  But once you bottle, free SO2 levels are going to slowly drop to where MLF could start up on its own.  Unless you have sterile-filtered your wine, it’s always possible that a few stragglers of O. oeni , or of some of its less savory lactobacillus relatives, could wake up to a nice malic acid breakfast and start making CO₂ in your bottle.

At our winery (Little Oaks Winery) we have made Viognier, rosé of Barbera and of Sangiovese, and Chardonnay.  All of these are fermented at 50-55 °F, and no MLF is undertaken.  When fermentation is done, the wines are chill-proofed to 30-32 °F for two weeks, then allowed to warm up for 2 days in time for bottling.  We carry out the bottling under nitrogen and sterile-filter through a 0.4 micron filter to prevent any bacterial stragglers.

When to start?

At primary: Some vintners like to inoculate for MLF right at or just after the initiation of primary fermentation.  The idea here is that the O. oeni will get going in the presence of yeast and become acclimated to the yeast byproducts and alcohol levels early on.  As alcohol levels rise, there is an increased risk of getting MLF stuck, so this avenue may be good for wines whose expected final ABV is going to exceed 15%.  Since MLF must be carried out at low free SO₂ levels, this approach also has the advantage of minimizing the time that the young wine spends at risk of oxidation.

At secondary: Typically this is the approach taken by most vintners.  Once primary fermentation has ceased, the O. oeni doesn’t face a huge population of yeast competing for resources. Also it is possible that in the presence of residual sugar the O. oeni will start to use the sugars instead of the malic acid as a food source, which could lead to off flavors and undesirable affects such as high levels of VA.  In general we find that post alcoholic fermentation is the best method for us.

Protocol for inoculation

If starting MLF after alcoholic fermentation most winemakers will rack the wine off the gross lees before initiating MLF because leaving wine on the gross lees during secondary fermentation could lead to undesirable effects such as H₂S (hydrogen sulfide, rotten egg smell). Once racking is complete it is time to inoculate the wine. There are two popular types of O. oeni used for malolactic fermentation; one is considered a direct inoculation variant, where the freeze-dried O. oeni are added directly to the wine, and the other type requires a rehydration step in water for approximately 15 mins before adding to the wine. Along with the O. oeni bacteria themselves there is also ML nutrient available that is typically used in the rehydration step.

Our wine is pressed off the grape skins at about 0 degrees Brix and we will rack the wine approximately  24 hours after it has been pressed.. We like to use the direct inoculation O. oeni.  We have found that adding  ML nutrient before adding the O. oeni to our wine helps promote a successful  MLF. We measure out the O. oeni at 1 g/40 gal and for our ML nutrient we use Acti-ML at a rate of 0.84 g/gal. We put our desired amount of O. oeni and Acti-ML in with chlorine free water and let incubate for 15 minutes. We then give the mixture a good stir and then gently add it into the wine. Once it is in the wine container we do not mix it but let it sit for a few days.  The O. oeni tend to settle at the bottom of the barrel so it is a good idea to mix/stir the barrel or container 1-2 times per week.

How to monitor MLF

It’s important to know when MLF is done, because you need to bring up SO₂ levels as soon as you can to minimize oxidation and spoilage of the wine.  During MLF, malic acid levels will drop from over 1000 mg/L typically, to below 50 mg/L at completion.  Some vintners rely on the pH and TA changes (increase and decrease, respectively) to assess completion of MLF.  However, the danger lies in an MLF that goes part way.  If you have 100 mg/L of Malic Acid left, that is enough to pop a cork if MLF starts up again.  The pH and TA changes are too subtle to be reliable indicators of completion.

There are several ways to monitor the progress of MLF by measuring malic acid levels.  Many wine makers rely on the paper chromatography method.  This is fairly simple to run, and it is semi-quantitative if you run known standards alongside your samples.   The drawbacks are that it involves use of noxious reagents and takes 24 hours generally to complete.  But probably the biggest drawback is lack of sensitivity: it’s difficult to assess levels below about 200 mg/L.  So again there is a risk of miscalling MLF and having exploding corks and bottles.

Commercial wine analysis labs will typically use HPLC or enzymatic spectrophotometric methods.  These are accurate and sensitive enough, but the instrumentation costs upwards of tens of thousands of dollars.

Accuvin (Napa, CA) makes the “Quick Test” kits for a variety of wine tests.  Their malic acid test produces a colored spot whose intensity is proportional to malic acid levels.  We have found them to be semi-quantitative, but capable of determining completion of MLF.  Our assessment of these in comparison to other methods is on our web site https://vinmetrica.com/wp-content/uploads/2014/06/Malic_testing_comparisons_original_SC-50.pdf  Note that the version of the SC-50 kit (see below) used in this report has now been updated.

Our  SC-50 MLF Analyzer kit https://vinmetrica.com/product/vinmetrica-sc-50-mlf-analyzer-kit/ can be used to determine malic acid concentration in wine.  This kit relies on the biochemical MLF reaction caused by enzymes found in certain bacteria, including Lactobacilli and Oenococcus strains, and in the “Biopressure” agent component of the kit. These bacteria live on a variety of nutrients, but their production of CO₂ results almost entirely from the enzymatic transformation of malic acid to lactic acid as shown above:

The CO₂ creates pressure, which is read by the MLF Analyzer.  The CO₂ biopressure signal is directly proportional to the amount of malic acid in the sample. The level of malic acid can be calculated from the digital readout by a calibrator of malic acid provided with the kit.  Detection limit is below 0.04 g/L (40 mg/L).   The cost of the unit is around $160 and cost per test is about $3.00.

Do you have any tips for starting up stuck MLF? Share them in the comments below.

Cheers!

Dr. Richard Sportsman

 

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 of the product.   In that regard, many attendees stopped by the Vinmetrica booth to hear and see the latest products, including our ABV kit and dissolved oxygen system, as well as the workhorse SC-300 SO₂ and pH/TA analyzer.

Of course there were several opportunities to try some great local wines as well as the proud creations of the members.

Next year, Winemaker Magazine will host its conference right here in San Diego, so Vinmetrica will especially do its part to make it another success!

KickStarter Program through July 29^th 2017

Don’t forget to check out our WinePilot Project on Kickstarter! Go to www.kickstarter.com and search on Vinmetrica.

Vinmetrica’s WinePilot project will bring the power of smartphones and the internet to your wine making. Our latest versions of the SC-300 are pre-configured for serial communication, and now we will develop the communication module and smartphone app to control, analyze and display your wine’s chemistry and history.

There are several reward levels if you pledge your support. You will see these options on the right hand side of the web page. You can upgrade recent versions of the SC-200 and-300, or receive considerable discounts for older versions of any of these, including the original SC-100 and 100A.

You’ll receive the latest version of the SC-300 with the WinePilot adapter and Smartphone App!

Thanks!

~Dr. J Richard Sportsman, Ph. D, President

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

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.

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

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.

Do you want to take your winemaking to the next level? We hope you already measure important parameters like free SO₂ (sulfites), pH, titratable acidity and malic acid, but residual sugar has always been tricky, expensive, and/or subjective when trying to get a quantitative answer. Now Vinmetrica introduces its NEW Residual Sugar reagent kit.  Using the pH meter you already have, you can now get accurate and reliable residual sugar data.

Residual sugar is simply the amount of sugar left over in your wine after alcoholic fermentation has completed (in some cases this includes sugar that has been added later to increase sweetness).  Residual sugar values are expressed in g/L or as a percentage of weight to volume. Dry wines typically have up to 4 g/L (0.4%) residual sugar , medium-dry wines have up to 12 g/L (1.2%), medium wines up to 45 g/L (4.5%) and sweet wines have over 45 g/L. You certainly want to be sure that your Chardonnay or Syrah is dry, while you probably want that Riesling to be moderately sweet.  So knowing the level of residual sugar in your wine sample is important.  But there are two other factors that you want to keep in mind.

First, the residual sugar level lets you know that fermentation is over and whether stabilization will be needed.  Wines containing about 2 g/L of residual sugar or more may need to be stabilized with potassium sorbate (sorbitol) to ensure that fermentation will not start up and cause bottle explosions. You do not want to add sorbitol to wines that have already undergone malolactic fermentation as the sorbitol reacts negatively with the lactic bacteria and can cause unpleasant odors. You should stabilize your wine with sulfite and sterile filtration instead and monitor your wine while it ages in bulk to ensure fermentation does not start up again.

The second reason why measuring residual sugar is important is for labeling purposes: you are able to characterize your wine’s sweetness. Knowing the concentration of residual sugar in your wine allows you to classify it as a sweet wine or a dry wine or something in between. The European Union has classifications based on the residual sugar level, for example.

In our newly released Residual Sugar Reagent Kit, you will now have the tools to quantitatively test your residual sugar levels. Using the pH meter you already have, the Residual Sugar reagent kit can give you reliable, accurate results quickly and affordably at less than $3.00 per test.

For questions, please email info@vinmetrica.com or visit the Residual Sugar Reagent Kit product page (//vinmetrica.behladev.com/product/residual-sugar-reagent-kit/) for more information.

 

Adapted from: http://winemakermag.com/501-measuring-residual-sugar-techniques by Daniel Pambianchi

Do you wait for the completion of Malolactic fermentation before adding sulfite to your wine? This reduces the overall acidity of your wine, leading to a smooth, softer mouth feel and a pleasant complexity in nose and taste. If malic acid levels are not reduced below around 0.1 g/L, there is significant risk that fermentation will start up again in the bottle, popping corks and/or making that beautiful red you so lovingly put up in your cellar turn fizzy! So it’s important to have accurate information on your malic acid levels.

Recently, Vinmetrica’s president Richard Sportsman completed a comparative analysis of Malic Acid testing methods by comparing Vinmetrica’s SC-50 MLF Analyzer (paired with the SC-300 Analyzer), Accuvin MLF test strips, HPLC (High Performance Liquid Chromatography) and an enzymatic assay.

The full report can be found here or in Vinmetrica’s FAQ section under MLF Questions. Happy testing (and tasting)!

The beauty of winemaking is that no matter which side of your brain you use more often, it encompasses both; bringing together the art and the science of winemaking. But here is the real question. How many of our readers make their wine in a scientific fashion? Noting every single detail about your sulfite levels, color of your wine, the taste, the smell and even the location it is stored in? Or are you the type of winemaker that adds sulfite without measuring or doesn’t take notes and just does “what the wine tells them to do”?

I realize that not everyone has had to live through the long and trying hours of writing in and maintaining a laboratory notebook. I remember in college, my lab partners and I would get together and try to remember how many milliliters we pipetted here or how long we incubated there… If only I would have learned sooner that the attention to detail and the thoroughness of a lab notebook can make or break it in the end.  It’s the same when you are making wine. If you keep a detailed notebook you will have all the information right at your finger tips should you ever need it.

How many of our readers wish they were able to duplicate a vintage wine with a new harvest? It may be possible to do so, especially if you keep thorough notebooks. Plus, this sort of practice is great if you decide you want to become a bonded winery somewhere down the road.

So, what are the tricks to keeping a great winemaking lab notebook?

Setting up a great lab notebook:

1. It’s always good to start with a sturdy notebook with bound pages, such as a standard composition book available in most stores and office supply places.  M ake sure to put your name and contact information on the front page.
2. A table of contents is also a great feature to start with. This is especially good if you plan on having several types of wine or carboys in one notebook.  This brings up another good point; you can’t use a table of contents without numbers on the pages! I know this may be a bit time consuming but it will be worth it! Trust me!  So number your pages right away.
3. I also always like to leave several blank pages at the front of the book for a “random notes” section. Here I may write the information about the potassium metabisulfite (KMBS) I purchased such as where I bought it, how much it was, the LOT number on the package and the vendor. This information may seem boring, but hey! It’s always good to have just in case.
4. If you are using one notebook for several wines, break your notebook up into sections and write any distinguishing information about the separate varietals on “cover pages”. Make sure to write these “cover pages” down in your table of contents.

 

What do I record?

1. It is important to write down detailed information as you are performing a procedure. The rule of thumb is that your notebook should be detailed enough so that someone with little or no knowledge of what you are doing can replicate the exact same procedure. Make sure your entries are clear and legible too! This can be important if you are not the only one testing sulfite levels in your wine.
2. Make sure you write down the barrel number you are testing and any identifying information of each sample.
3. It is a good idea to record as much as you can even though you may not need all the information. Record pH levels, ppm SO2, amount of KMBS added, etc… It is very important to keep track of your units of measure. If you are adding KMBS to your sample and it is a 10% KMBS solution and you write down 10 as the amount added, someone else looking at the notebook may think that is 10 grams of KMBS powder or that you added KMBS 10 times. Units of measure are very important in a lab notebook.

Finishing Up and Maintaining the Notebook:

As you record your activities in the laboratory, ask yourself, “Did I…”

• Keep up with the table of contents?
• Date each page?
• Number each page consecutively?
• Enter all information directly into the notebook?
• Include complete details of all first-time procedures?
• Include calculations?
• Highlight my results?

Now, I am not saying that this type of detailed lab notebook should be followed by everyone. This is simply a nice way to keep your notes organized and maintained. Always remember to keep your notebook in the same spot after testing.

Happy Testing!

Taylor

 

Adapted from: http://www.ruf.rice.edu/~bioslabs/tools/notebook/notebook.html#top

 

Sulfur Dioxide, or SO2, is a chemical compound used by winemakers to help keep their wine protected from the negative effects of oxygen exposure as well as spoilage microorganisms. Free SO2 is important for determining preservation ability. Total SO2 is not as important for home winemakers because it is usually measured to fulfill export regulatory requirements. Regular testing for Free SO2 allows for the winemaker to make the necessary additions to the wine to avoid spoilage. Vinmetrica’s SC-100A and SC-300 test for not only Free SO2 but Total SO2 as well, when you purchase separately our 1N NaOH solution. For more information about Free SO2 and Total SO2, check out this link to the MoreWine article: SO2 Management by Shea A.J. Comfort. http://morewinemaking.com/public/pdf/so2.pdf