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Free SO2: When and How

Protecting your wine with free SO2

Keeping the required amount of free SO2 in your wine is one of the important post-fermentation care steps you’ll need to stay on top of. While some people decide not to add SO2 (which is a personal preference, though we at Musto Wine Grape definitely recommend keeping the proper amount of free SO2 in your wine at all times), others choose to keep their wine protected by using it diligently.

Why we add it

To keep the wine protected. KMS serves as an antimicrobial and antioxidant and as such is a very important part in keeping your wine out of harm’s way. Without it, your wine can go bad very quickly.

How to test free SO2

Aeration oxidation method, manual ripper method, Vinmetrica, Hanna titrator, titrets

Setup for “aerative oxidation” method of checking free SO2. Though time intensive, it yields exact and accurate reuslts.

When to add it

  • During crush (to kill off any unwanted native yeast)
  • When fermentation has completed (be sure that MLF has completed as well, if that’s the goal)
  • During aging. Example: Each month many winemakers will test SO2, make any SO2 adds if needed, and then top it off.

Investing in Vinmetrica SO2 wine analyzer makes testing easy

How to add it

You’ll need to get potassium metabisulfite, if you don’t already have it. You may prefer to use campden tablets, which is fine too. Make sure it says potassium metabisulfite rather than sodium metabisulfite. The easiest way to figure out how much free SO2 you’ll need to add is to know your pH, first of all. Then you’ll need to decide if you’re using .8 or .5/6 molecular SO2. .8 is usually used for white wines, whereas .5 is used for red wines. Measure your free SO2 if you have a way of doing so. Then use the graph below to figure out what the target free SO2 is. From there you will likely choose an easy-to-use online resource such as wineadds.com to find out exactly how many grams of potassium metabisulfite should be added. Mix it with a small amount of water to ensure it can become completely incorporated into the wine.

*Remember: just knowing your target free SO2 in ppm does NOT tell you how many grams you will be adding. You need to figure that out as a second step, with an online SO2 calculator*

Graph indicating required free SO2

Now that you have a solid understanding of why, how, and when you add meta, you may want to delve into some deeper questions, such as…

Why do I need to keep adding meta? If I add a certain amount shouldn’t it stay at that number?

This is a great question. There are a lot of variables that go into answering this in as cohesive a way possible, and this could really be a topic in and of itself. Let’s keep it simple here: there are two measurements of SO2 in wine: free and bound. The free SO2 is what is actively protecting the wine, whereas bound SO2 is what has already tacked on to other compounds within the wine and as such is no longer able to actively protect it in the same way. Both are important numbers, but if a winemaker is only checking one, it’s going to be free. Over time free SO2 can become bound to various acids, solids, sugars, bacteria, yeasts, etc., that are present in the wine, which is why this number will not necessarily stay constant, especially immediately.

Why does pH affect how much SO2 I need to add?

A rule of thumb to remember is that higher pH = higher free SO2 requirement. Lower pH = lower free SO2 requirement. The chart below demonstrates the amount of free SO2 required base don the pH of the wine. This is just one of the many reasons that checking and knowing your wine’s pH is critical.

Do I need to measure total SO2 as well?

Knowing this number is important, but not as crucial as knowing your free SO2. It’s also a little less accessible of a test to run, which is why most home winemakers don’t choose to pursue knowing the total SO2 of their wines. It is possible to overadd SO2 and have the total SO2 be higher than desirable which can be problematic, so be sure to keep a running log and closely track how much you have added from the beginning of the wine’s life onward.

12 Steps to Making Wine from White Grapes

 

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Making Wine from White Grapes

1. Sanitize and Crush and Destem – Inspect your grapes and remove any moldy clusters. Crush and destem into clean and sanitized food grade plastic tubs. Always rinse your receiving vessel with a sanitizing strength potassium metabisulfite solution (2oz/gallon or 3tbsp/gallon). Make sure that the sanitizing solution touches all the surfaces of the vessel and that the vessel is completely emptied out of all sanitizing solution after. Shake free any drops as best you can from the vessel. Having remaining sulfite liquid in the vessel will prohibit fermentation. Do not rinse the sanitizer off with water after sanitizing as that will reintroduce bacteria to the environment.

2. Once all of the grapes are crushed, try to accurately measure your quantity of must. Add ¼ tsp of potassium metabisulfite for every 5 gallons of must that you have. Mix up the must thoroughly.

3. Wait for 2 hours after the sulfite addition and then add pectic enzyme to the must. Musto Wine Grape offers generic pectic enzyme or Cinn Free pectic enzyme that is specifically designed for white wine grapes. Follow the directions for the individual type of enzyme. Always mix it with water to create a 10% solution (if you use 5mls of enzyme, mix it with 45mls of water). The water allows it to better circulate throughout the must. Allow the pectic enzyme to work for 6 hours before pressing.

4. Press the Must – Wash the press and sanitize using potassium metabisulfite. Again, make sure the press does not have an excessive puddles or lingering amounts of sanitizing solution remaining. Sanitize the receiving container for fermentation (carboy, tank, demijohn, barrel) and any pumps or tubing that you may use. Anything that comes in contact with the wine should be rinsed with sulfite sanitizing solution. Place a screen or mesh (also sanitized) inside of the press to hold back any extra skins or seeds from getting through. Start by scooping up the must and placing it in the press. Some of the liquid will immediately flow through; this is the “free run”. When the press is full, slowly begin pressing. Do not try and press every last drop out of the must as this can lead to seed cracking and bitterness in the wine. Fill each container to within 6 inches of the top, to allow room for fermentation. This process will cause the juice to foam up and generate gas, therefore volume.

5. After pressing the grapes, mix the container thoroughly and take and record your measurements. Measure Brix, pH, and TA. If you need to adjust your juice at all, this is the time to do it. Ideally your Brix should be between 21-26 degrees, the pH between 3.2-3.5, and the TA between 6.5-8.5g/L. Your initial Brix reading, multiplied by .55, will give you a close estimate of your ending alcohol by volume percentage.

6. If you would like to use fermentation tannins (FT Blanc) or fermentation nutrients such as Opti-White, add them after measurements and adjustments have been made. Musto Wine Grape packages FT Blanc and Opti-White in small packs for 5 gallon batches. Mix any of these ingredients in thoroughly.

7. After measurements have been taken and any adjustments have been made, it is time to set yeast if you are using a cultured yeast strain. Use 1gram/gallon of wine must. Follow the yeast set directions on the packet explicitly and/or see the separate “Yeast Set” instructions.

8. After you atemperate and add your yeast, cover your tank with a floating lid or your carboy or demijohn with an airlock. An air lock will allow the carbon dioxide to escape the container without additional air getting in to oxidize the wine.

9. Stir the juice every other day to re-suspend the yeast and nutrients. Keeping the yeast in suspension is important to give it access to sugar and nutrients and to avoid the production of H₂S.

10. If you are using additional yeast nutrients to assist in fermentation you will add them after fermentation has started. Fermaid O is added at the beginning of fermentation (1 day after yeast set) and all others (BSG yeast nutrient, Fermaid K, AnchorFerm) will be added at 1/3 depletion of the Brix (2/3 of the beginning amount of Brix). Follow the directions for the individual yeast nutrient, hydrating with water and mixing thoroughly.

11. If you are adding malolactic cultures to your wine (Chardonnay), you may also chose to do this at 1/3 Brix depletion. If using a malolactic nutrient (Opti-Malo Plus) with the bacterial culture, hydrate the nutrient in a separate container from the bacteria and add to the must directly before the addition of the bacteria. Follow all directions on the bacteria and nutrient packets explicitly.

12. Monitor the progression of the juice by taking daily hydrometer readings. Using a sanitized wine thief or syringe, pull a sample of fermenting wine that is large enough to fill the hydrometer cylinder. Always sanitize the hydrometer and the cylinder before taking a reading. Look to the meniscus of the wine surface in relation to the hydrometer for the most accurate reading. When the wine is fermented to dryness (0.90 Specific Gravity), is has completed its primary fermentation. Allow the lees particles to settle, and then rack the wine into a sanitized container. Be sure that the container is filled within ½” of the top to prevent air exposure. At this point, it is imperative to add ¼ tsp of potassium metabisulfite per 5 gallons of wine. The sulfites will kill off any harmful microbes and prevent the wine from oxidizing.

13 Steps to Making Red Wine from Grapes

13 Steps to Making Red Wine from Grapes 

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1. Sanitize and Crush and Destem – Inspect your grapes and remove any moldy clusters. Crush and destem into clean and sanitized food grade plastic tubs, stainless steel tanks, or glass carboys or demijohns. Always allow an extra 20% of volume for fermentation purposes as the wine will “expand” throughout fermentation. Always rinse your fermentation vessel with a sanitizing strength potassium metabisulfite solution (2oz/gallon or 3tbsp/gallon). Make sure that the sanitizing solution touches all the surfaces of the fermentation vessel and that the vessel is completely emptied out of all sanitizing solution after. Shake free any drops as best you can from the fermentation vessel. Having remaining sulfite liquid in the vessel will prohibit fermentation. Do not rinse the sanitizer off with water after sanitizing as that will reintroduce bacteria to the environment.

2. Once all of the grapes are crushed, try to accurately measure your quantity of must. Add ¼ tsp of potassium metabisulfite for every 5 gallons of must that you have. Mix up the must thoroughly.

3. Wait for 6-8 hours after the sulfite addition and then add pectic enzyme to the must. Musto Wine Grape offers generic pectic enzyme or Color Pro pectic enzyme that is specifically designed for red wine grapes. Follow the directions for the individual type of enzyme. Always mix it with water to create a 10% solution (if you use 5mls of enzyme, mix it with 45mls of water). The water allows it to better circulate throughout the must. Allow the pectic enzyme to work for 12 hours before yeast set.

4. Twenty four hours after crushing the grapes, mix the container thoroughly and take and record your measurements. Measure Brix, pH, and TA. If you need to adjust your must at all, this is the time to do it. Ideally your Brix should be between 23-28 degrees, the pH between 3.4-3.7, and the TA between 6-7g/L. Your initial Brix reading, multiplied by .55, will give you a close estimate of your ending alcohol by volume percentage.

5. If you would like to use fermentation tannins (FT Rouge, oak dust) or fermentation nutrients such as Opti-Red, add them after measurements and adjustments have been made. Musto Wine Grape packages FT Rouge and Opti Red in small packs for 5 gallon batches. If using oak dust, use 1/4cup for every 5 gallons of must. Mix any of these ingredients in thoroughly.

6. After measurements have been taken and any adjustments have been made, it is time to set yeast if you are using a cultured yeast strain. Use 1gram/gallon of wine must. Follow the yeast set directions on the packet explicitly and/or see the separate “Yeast Set” instructions.

7. After you atemperate and add your yeast, you may cover the vessel lightly with an old sheet or towel or place the lid gently on top of the bucket, if an airlock is in place. An air lock will allow the carbon dioxide to escape the pail without additional air getting in to oxidize the wine.

8. Obtain a must punch tool, a long stainless steel spoon, or your bare hands, and sanitize your tool or hands with sulfite sanitizer. This is what you will use to “punch down” or mix up the must three times a day. Try to mix everything very well, pushing all of the skins back down to the bottom, getting them very wet, and bringing up the piqued from the bottom. This should be done as often as possible, preferably three times a day. [Before work (7am), after work(5pm), and before bed (10pm)] When punching down every evening, take a sample of the liquid and using your hydrometer, track the Brix depletion. You should notice a drop in Brix daily.

9. If you are using additional yeast nutrients to assist in fermentation you will add them after fermentation has started. Fermaid O is added at the beginning of fermentation (1 day after yeast set) and all others (BSG yeast nutrient, Fermaid K, AnchorFerm) will be added at 1/3 depletion of the Brix (2/3 of the beginning amount of Brix). Follow the directions for the individual yeast nutrient, hydrating with water and mixing thoroughly.

10. If you are adding malolactic cultures to your wine, you may also chose to do this at 1/3 Brix depletion. If using a malolactic nutrient (Opti-Malo Plus) with the bacterial culture, hydrate the nutrient in a separate container from the bacteria and add to the must directly before the addition of the bacteria. Follow all directions on the bacteria and nutrient packets explicitly.

11. Punch down and take Brix measurements daily. When your hydrometer reads 0.90, you have fermented to dryness. At this point your malolactic fermentation may still continue, but the primary alcoholic fermentation is complete. You may now press the wine. Wash the press and sanitize using potassium metabisulfite. Again, make sure the press does not have an excessive puddles or lingering amounts of sanitizing solution remaining. Sanitize the receiving container (carboy, tank, demijohn, barrel) and any pumps or tubing that you may use. Anything that comes in contact with the wine should be rinsed with sulfite sanitizing solution. Place a screen or mesh (also sanitized) inside of the press to hold back any extra skins or seeds from getting through. Start scooping up the must and placing it in the press. Some of the liquid will immediately flow through, this is the “free run”. When the press is full, slowly begin pressing. Do not try and press every last drop out of the must as this can lead to seed cracking and bitterness in the wine. Fill each container to within ½” of the top and secure a bung and airlock in place. Malolactic fermentation will exude a small amount of carbon dioxide and there will be trapped gas within the wine that will need to escape the container.

12. Allow the wine to sit for 2-3 weeks. You can conduct malolactic chromatography or bring a sample to a winemaker at Musto Wine Grape for analysis to ensure that your secondary fermentation is finished. At this point you should see a nice thick layer of lees in the bottom of the carboy or demijohn. You will want to place the full vessel onto an elevated surface such as a table and place the new, sanitized, empty vessel on the floor below. Using a sanitized siphon, rack the wine into the new carboy. You may have space at the top which will need to be “topped off” with more wine. You can either use wine from another container, or finished wine to do this. It is very important that there is less than a 1/2” of headspace in each container. At this point you should also add 1/4tsp of potassium metabisulfite per 5 gallons of wine.

13. Now it is time to let your wine age. You will need to rack it and add additional SO₂ every 3 months. Make sure you sanitize all equipment and containers when racking and keep them topped off within ½”. Come visit Musto Wine Grape for bottling advice and supplies.

Bring On The Bordeaux! – A Home Winemaking Experience

This year we are making Bordeaux Blends. One blend is made up of 68% Cabernet Sauvignon from Oakville, 14% Petite Verdot from Atlas Peak, and 18% Merlot from Caneros, Napa Valley.  This blend costs more than my first our first cars so we are praying we don’t screw them up. Lol

We crushed the grapes on 10/22. It was a deep, dark, and beautiful color purple.

       

 We added about 3.5 tsp of postassium meta-bisulfite to keep the must from fermenting and 50mL of Color Pro to bring out even more color. We left the must in a cold soak for 6 days. Keeping the must in a cold soak helps extract “the good stuff” – all the vivacious flavors and color components great Bordeaux’s posses.

  

There is more information to come! Stop by for the next post updating our wine making process!

Next  we will be discussing Degrees Brix, Total Acidity, and pH Levels

Until next time….

Cheers ~ CM & FJ

Images via D. Pelletier