SO2 - what’s the use?

[MedPretzel]

A response I got in an email... This is the question I asked:


I've been thinking about it for a while (and I even bought a sulfite titrette kit, but don't really know what to do with it.).

I feel a little silly admitting that and asking this question, but....


Why would you need to know the sulfite levels other than if you are wondering over a stuck fermentation? Or am I missing something big here?







And this is the response I got:

Martina, I think that sulphite are the most important aspect of winemaking. If you work with kits, this is easy because you only have to follow the instruction and add the sulphite package when requested. The calculation for the proper amount of sulphite has been made by the manufacturer. However, if you do work with fruits or grapes you have to add the proper quantity of sulphite for many important reason.

First, too much sulphite or too low can be dramatic and could ruin the whole batch. This is rare but it happen ( mainly when too low SO2 content ). In low sulphite wine, you will get a beautiful place for bacteria infection, including aceto vinegar which will turn your wine in a highly priced vinegar

In low sulphite wine, the color will be less bright, less attractive, oxydation will begin soon. In high content sulphite, you will get bad off-flavors, bad taste, a loose of the color intensity and in very large quantity it can be dangerous for your health ( but you know this better than me

) .

You have to know that sulphite ( So2 ) is pH dependant. Meaning that the same amount add to a given wine will give different level of So2 concentration is the wine depending on the pH. Low pH wine required less quantity of sulphite for the same effect. In high pH wine you will required much more quantity of sulphite to get the same concentration in the wine. A low pH wine is below 3,45 and a high pH is more than 3,65. In between are the normal correct range for wines. Sulphite come in many sources. Most homewinemakers use potassium metabisulphite or sodium metabisulphite. Both salt have the same property but metabisulphite is better because it does not add sodium in the wine. Potassium metabisulphite is often refer to K-meta. When you add any given amount of k-meta to a wine, you will get some of this addition that will bound to some of the wine's components and O2 molecule and it is called fixed or bound So2. The remaining part that is not bound will remain as free state, therefore naming free So2. The free So2 is the one that protect the wine against microbial spoilage and oxydation. The quantity that are bound and stay free are not calculable with math. formulation. We can only estimate as this vary from wine to wine depending on the pH of the wine and the oxygen present in the wine and such. What is sure, is when you add the first dose of k-meta in a wine most of it will become bound and when the wine are at a certain level of bound So2, every further addition will stay mostly as free So2. However, every time the wine is expose to oxygen this will consume some of the free So2. That is why we need to add back k-meta if the wine is to be rack, filter, bottle, age for a while and such. Since we do not want a low So2 content in our wine and either a high concentration we need to know what are the free So2 level in our wine before doing anything. When we know that we have 20 ppm of free So2, we can estimate with formulation what amount will be required to get back to a more acceptable level or maybe 40-50 ppm.

We know So2 is pH dependant. A good rule of thumb is to take the last two digit of the pH of the wine and keep this level of free So2 in the wine. A wine that are at 3,45 pH will required 45 ppm free So2. 3,30 pH will required 30 ppm free So2. This is for a red wine, add 10 ppm more for white wine that are more sensitive to oxydation. Avoid going higher than 75 ppm. So at 3,80 pH you will target 75 ppm maximum.

I hope this can help others too.

 

[jobe05]

Thats actually very good. Who ever wrote it, responded in a mannor that the layman could understand. I think it would take a few times of following this example, but it good and understandable.


Thanks Martina.

 

[AAASTINKIE]

Does anyone else get a headache from sanitizing bottles in SO2? I
bottled me first REAL Beer and my Pineapple Beer today and had a
headache the whole time but it went away after I was finished, and it
has happened before.

 

[MedPretzel]

Some say there is an allergic response to SO2. If it exists, I cannot explain. Some say yea, some say no. I am not an allergist, so I cannot tell you either way.


What you might be experiencing is an allergic response.





Or it might be the beer.

(NAHHHHHH!)





If you do not experience any response other than inebriation when you drink your beer/wine, you could pretty much rule out an allergic response. However, the body is complex and different people react differently to different substances. You might want to check it out with an allergist to make sure.


Congrats on your first "Real" beer, though...

Again, I haven't forgotten you, just delayed. Lots of stuff going on in Ohio at the moment. Sorry...

 

[Waldo]

Hmmmm I know I am allergic to Sulpha drugs. Wonder if Sulpha and Sulfite are related?

 

[bilbo-in-maine]

The fumes coming off an open source of the solution irritates my upper
respiratory area...

 

[smurfe]

Hmmmm I know I am allergic to Sulpha drugs. Wonder if Sulpha and Sulfite are related?

Waldo, No, they are different compounds.


Sulfa is an antibacterial drug while sulfite's are antioxidants which is a subclass of Sulfates. Years ago in paramedic school we had to study this. For example many that are allergic to Sulfa feel they may be allergic to drugs such as Morphine Sulfate which is regular Morphine. Not true, they are a different class altogether. Sulfates and Sulfites are related but Sulfa is in a different class. Here is some interesting reading on sulfites:


The Sulfates are an important mineral class and include some very interesting and attractive specimens. Although many minerals belong to this class onlybarite, gypsum, and anhydrite can be considered common. The basic chemical unit is the (AO4) complex anion with a charge of negative two (-2). The sulfites, selenites and tellurites (notice the spelling) have a basic unit of (AO3)The A can be either sulfur (S), chromium (Cr), tungsten (W),selenium (Se), tellurium (Te) and/or molybdenium (Mo). The principle anion group nevershares oxygens with other principle anion groups and this limits the structural possibilities. The A atom at the center of the AO4anion has a positive six charge (+6) and the oxygens have their obligatory negative two charge (-2). The AO4 anions form symmetricaltetrahedrons when A is either sulfur or chromium and flattened tetrahedronswhen A is either molybdenium, selenium or tungsten. The flattened tetrahedrons form a square outline and help produce (in most of those minerals) a tetragonal(four fold) symmetry, which is an uncommon symmetry in minerals. The typical Sulfate Class mineral is vitreous, average to above average in density,average in hardness and are originally formed in veins, oxidation zones,contact metamorphic zones and in evaporite deposits. Some Sulfate Class minerals are soluble and several are <M href="/minerals/fluoresce.htm" target="_blank">fluorescent</M>.All other properties are variable.


Source: http://mineral.galleries.com/minerals/sulfates/class.htm


Glad I could help you out

Smurfe

 

[smurfe]

Does anyone else get a headache from sanitizing bottles in SO2? I bottled me first REAL Beer and my Pineapple Beer today and had a headache the whole time but it went away after I was finished, and it has happened before.

I never noticed it during sanitation but I do suffer from the headaches from red wines. I get some terrible hangover symptoms from over indulgence. I have only ever experienced hangovers from drinking wines, never beers or liquor.


Here is an article about it http://www.beekmanwine.com/prevtopbd.htm


Smurfe

 

[MedPretzel]

Okay.

I tried to use those titrette things again, and the result was that my hands were blue, and I didn't have a SO2 result.





Can someone explain to me how these titrettes are supposed to work?


I have two left hands, (and I am right-handed).

 

[Joseph1]

Martina, These are the instructions I have for Titrets. Somehow, I think you are looking for more information than this and unfortunately I have no camera.


1. Collect the sample in any clean container.


2. Push a valve assembly onto the Titret ampoule tip until it fits snugly.


3. Gently snap the tip of the ampoule at the score mark. The score mark is about a 1/4 inch from the tip.


4. With the tip of the valve assembly immersed in the sample, squeeze the bead valve briefly to add a small amount of sample to the Titret. The contents will turn a deep blue color. Wait 30 seconds.


5. Rock the Titret to mix the contents.


6. Continue to add small amounts of the sample until the liquid in the Titret turns from blue to colorless or the color of the red wine for red wines. Be sure to rock the Titret to mix the contents after each addition of sample. When the color of the liquid in the Titret changes to colorless (or the color of the sample), the end point has been reached.


7. Hold the Titret with its tip pointed upward and read the scale opposite the liquid level to obtain the test results in ppm (mg/L) free sulfur dioxide.

 

[MedPretzel]

Thank you, Joseph.

I got to step 5, but none of the sample went into the titrette. It turned blue, but nothing else went into the glass thing.

And then, after fiddling with it (and getting that blue stuff on my hands), the bead thing popped out.

Is there something like SO2 litmus-paper available? I'm too uncoordinated to do this, it seems.

 

[MedPretzel]

Question:


George has got this in the online-shop... Iodic (SO2) Solution


Measures free sulfites in wine; use with Acidometer #6856.


The acidometer's description says only something about pH testing. Does anyone use this to measure free SO2? If so, can you give a run-down on it? Is it easier than the titrettes?


Thanks!


(By the way, I totally messed up any experiments of titration in college and med-schoolChemistry, so I need something that's idiot-proof.)