Sulfur has been known and used for centuries. Today, we can explain its properties. It has different actions against oxidation and micro-organisms. We have also been able to identify its different forms: free, combined, total and active.
For over 20 years, winegrowers have been working on reducing SO2 doses. It is motivated by the search for olfactory intensity, and the presentation of wines for tasting that avoid closed, drying, aggressive and hard characters on the palate.
By using the HI 84100-02 mini-titrator (see attached data sheet), you can manage the amount of free (and total) SO2 in your wines directly in the cellar, before and after each stage of vinification and maturation, right up to bottling.
This device will enable you to control the first SO2 phase of your wines. It can also be used to determine the quantity of active SO2.
Let's think in terms of active SO2, not free SO2!
The most effective form of free SO2 is called active SO2. Active SO2 is not measured, but calculated from several elements in the wine: pH, % vol, T° and free SO2.
(This formula is available at www.hanna-vin.com
In the meantime, you can view it at http://www.vignevin-sudouest.com/services-professionnels/formulaires-calcul/so2-actif.php)
This formula gives you two indications:
The first concerns your wine's effective level of protection against micro-organisms and oxygen.
The second concerns the dose of SO2 to be added to the tank to obtain optimum protection.
Active SO2 protection must be greater than 0.35 mg/l, and a maximum of 0.8 mg/l for dry wines. Depending on the stage of the wine, color, cellar hygiene, vintage, wine-growing region, state of the harvest, polyphenolic richness, etc., we aim to achieve between 0.4 and 0.7 mg/l of active SO2.
When pH levels are low, optimal protection can be achieved at around 0.5 mg/l of active SO2.
The tricky part comes with higher pH wines (above 3.6).
In these cases, it's vital to also consider the reduction of oxygen dissolution, and to maintain impeccable cellar hygiene.
Measuring dissolved oxygen
Measuring dissolved oxygen is very useful before and after operations such as racking, filtration and other wine handling operations, or just before bottling.
This measurement enables us to determine the risk level of a wine, and whether it is necessary to readjust the SO2 or deoxygenate the wine.
Using the HI 9146-04 oximeter (for tanks) or the HI 9146V (for bottles), you can measure, control and quantify the voluntary or involuntary addition of dissolved oxygen (cf. enclosed data sheet).
All decanting is accompanied by dissolved oxygen, to a greater or lesser extent depending on the technique used. The results obtained by J. Ribereau-Gayon in 1993 on the quantities of dissolved oxygen have been further refined.
OperationDissolved oxygen (mg/l or ppm)
Per operation
Pumping1-2
Decanting4-6
Filling "without aeration "2-5
Filling "with aeration "4-8
Filling0,2-1
Ellagic tannins (300 to 500 mg/l)
Earth filtration4-6
Plate filtration3-5
Centrifugation5-8
Bottling2-4
Per year
Per bung holeEnv. 0,5
Aged in young barrels0.4
Aged in old barrels0,2
Ageing in vats< 0.1
Depending on the cumulation of oenological operations, the wine receives between 5-10 and 50-60 mg/l of oxygen, from the end of fermentation to bottling. This oxygen reacts and disappears within 8-20 days, depending on the wine and temperature.
From "Connaissance et travail du Vin" - by Jacques Blouin and Emile Peynaud - Dunod Edition - pages 193, 198 and 199.
Measuring dissolved oxygen before and after bottling is very useful. It shows whether the wine contains less than 0.5 mg/l of dissolved O2, which will not alter organoleptic qualities, or whether it contains more than 1 mg/l of dissolved O2, which will guide the producer to reduce this dose by deoxygenating the wine (especially for whites and rosés), or by increasing SO2 doses.
Taking into account these different aspects of wine protection, and in order to maintain the same ageing time, lowering sulfur doses must necessarily be accompanied by the implementation of means to protect the wine against oxidation and micro-organisms.
Today, we offer you the possibility of measuring these elements with our Wine Line instruments, specially designed for oenology and field analysis.
HOW TO REDUCE SO2 IN WINE?
DECISION-MAKING TOOLS
Sulfur has been known and used for centuries. Today, we can explain its properties. It has various actions against oxidation and micro-organisms. We have also been able to identify its different forms: free, combined, total and active. For over 20 years, winegrowers have been working on reducing SO2 doses. It is motivated by the search for olfactory intensity, and the presentation of wines for tasting that avoid closed, drying, aggressive and hard characters on the palate.
By using the mini-filter from Hanna Instruments (see technical data sheet), you can manage the quantity of free (and total) SO2 in your wines directly in the cellar, before and after each stage of vinification and aging, right up to bottling. This device will enable you to control the first SO2 phase of your wines. It can also be used to determine the quantity of active SO2.
Let's think in terms of active SO2, not free SO2!
The most effective form of free SO2 is called active SO2. Active SO2 cannot be measured, but is calculated from several elements in the wine: pH, % vol, T° and free SO2.
Active SO2 protection must be greater than 0.35 mg/l, and no more than 0.8 mg/l for dry wines. Depending on wine stage, color, cellar hygiene, vintage, wine-growing region, harvest condition, polyphenolic richness, etc., we aim to achieve between 0.4 and 0.7 mg/l of active SO2.
When pH levels are low, optimal protection can be achieved at around 0.5 mg/l of active SO2.
The tricky part is for wines with higher pH levels (above 3.6). In such cases, it is essential to also consider the reduction of oxygen dissolution , and to maintain impeccable cellar hygiene.
Measuring dissolved oxygen
Measuring dissolved oxygen is very useful before and after operations such as racking, filtration and other wine handling operations, or just before bottling. This measurement enables you to determine the risk level of a wine, and whether it is necessary to readjust the SO2 or deoxygenate the wine.
All decanting is accompanied by oxygen dissolution, to a greater or lesser extent depending on the technique used. Some studies have clarified the results obtained by J. Ribereau-Gayon in 1993 on the quantities of dissolved oxygen:
Operation
Dissolved oxygen (mg/l or ppm)
Per operation
Pumping
1-2
Transfer
4-6
Filling " without aeration "
2-5
Filling " with aeration "
4-8
Filling
0,2-1
Ellagic tannins (300 to 500 mg/l)
Earth filtration
4-6
Plate filtration
3-5
Centrifugation
5-8
Bottling
2-4
Per year
Per bung hole
Approx. 0.5
Aging in young barrels
0,4
Aged in old barrels
0,2
Aged in vats
< 0,1
Depending on the accumulation of oenological operations, the wine receives between 5-10 and 50-60 mg/l of oxygen, from the end of fermentation to bottling. This oxygen reacts and disappears within 8-20 days, depending on the wine and temperature.
From "Connaissance et travail du Vin" - by Jacques Blouin and Emile Peynaud - Dunod Edition - pages 193, 198 and 199.
Measuring dissolved oxygen before and after bottling is very useful. It shows whether the wine contains less than 0.5 mg/l of dissolved O2, which will not alter organoleptic qualities, or more than 1 mg/l of dissolved O2, which will guide the winemaker to reduce this level either by deoxygenating the wine (especially for whites and rosés), or by increasing SO2 doses.
Taking into account these different aspects of wine protection, and in order to maintain the same ageing time, lowering sulfur doses must necessarily be accompanied by the implementation of means to protect the wine against oxidation and micro-organisms.
Today, we offer you the possibility of measuring these elements with instruments from the Wine Line range from Hanna Instruments, specially dedicated to oenology and field analysis.
Full document | How to reduce SO2 levels in wine | e-viti.com
In charge of product development at e-viti since 2016, Catherine shares her skills and expertise in viticulture and landscaping, to provide you with valuable advice.
