WHY DO WE STILL USE SULFUR DIOXIDE IN ORGANIC WINE?

Sulfur is permitted for use in organic wine because there is no other way to make sure that quality wine keeps, cellars and improves in the bottle, rather than turns to vinegar. The use of sulfur in organic wine means it is not necessarily preservative free, though some wineries such as Botobolar at Mudgee make small quantities of preservative free and certified organic wines. However, the low level permitted (about half the normal amount) means organic wine can achieve the standards of quality that are demanded by consumers.

These are some reasons we support this situation.  

Sulfur is naturally occurring. It is the tenth most abundant element in the universe, and is a component of many amino acids and proteins. As shown in the images, it occurs naturally as a crystal and is found in many different deposits on the earth's surface. Whilst the pools of Rotorua and the clouds of Krakotoa are classic volcanic forms, Sulfur has been mined since antiquity from many sources. Today a deposit consisting of a mix of sulfur, gypsum, lime and clay, containing typically about 25% sulfur, is still mined in Sicily. It is a former deposit on a deep sea floor, where alga and dead animals, whose proteins typically contain about 2% sulfur, settled over thousends of years. Under anaerobic conditions, sulfur bacterias reduced this biologically bound sulfur to sulfur-hydrogen and finally to the sulfur which is mined today. It is extracted by melting the sulfur from the excavated material in the absence of air, then purifying it by distillation. The main source of sulfur today is raw natural gas, which contains about 0,1 - 0.5% hydrogen sulfide (H2S). Since hydrogen sulfide gas is poisonous it is washed in sulfuric acid yielding relatively harmless sulfur dioxide and elemental sulfur.
Sulfur is essential for good winemaking. After the grapes are crushed (the stems are mechanically separated), the blend of pulp, skin and seeds are transfered to a vat. For white wine only the juice is used, for red wine the juice is pressed off the skins and pulp after fermentation. Here SO2 is introduced to inhibit the wild yeasts. These are too varied in composition, leading to a competition amongst themselves that causes fermentation to stop prematurely. They are replaced with a pure culture, usually of Saccharomyces cerevisiae which is resistant to sulfur.In addition,SO2, inhibits enzymes that oxidize phenolic compounds responsible for discolouring wine.

This is what Australia's foremost authority on winemaking, Bryce Rankine, says: Sulfur dioxide (SO2) is almost universally used in winemaking, and is one of the few compounds for which legal maximum limits exist (350 ppm total SO2 in Australia ). SO2 is a remarkable compound, since it combines both germicidal and anti-oxidant properties, and an excess can be detected by smell. No other compound has been found which possesses all these characteristics… SO2 exists in wine in both free (uncombined) and bound (combined) forms. The free form consists of molecular or un-ionised SO2 … and is the more effective form…. The amount of free SO2 required to preserve a wine is related to pH… ie in the more acid wines, we need less free SO2. (Source: Bryce Rankine (OA), Making Good Wine, 1989, Pan Macmillan p 106)

Preservative Free Wine is a Myth, according to the AWRI. The Australian Wine Research Institute website states that: The word “preservative” refers to protecting the wine from microbial contamination or spoilage by unwanted bacteria, moulds and yeast…. There are no wines on the market labeled “preservative free”. This is because all wines contain naturally a small amount (10-50 parts per million) of the antimicrobial agent, sulfur dioxide (SO2), as it is produced by yeast during the fermentation stage of winemaking. There are, however, wines on the market labeled “organically grown”, which contain a reduced amount of antimicrobial agents. For example, organic winemakers add approximately 50% less sulfur dioxide during winemaking.

Free SO2 is lower in old wine, and higher in many foods, according to James Halliday: SO2 gradually diminishes with age as it becomes chemically bound… A small degree of sulfur can and often does merge into the wine as part of the complexity of its flavour, as a positive addition to its character…Depending on a wine's pH, between 13ppm and 60ppm of free sulfur are required to control microbial growth… These levels are quite low by overall food standards. Fresh fruit salad or vegetable salad in health food bars frequently contain 200ppm free SO2, while other semi-processed foods and beverages frequently contain significantly higher levels..." Source: The Art and Science of Wine, by Halliday and Johnson, 1997.
Hint: Allowing wine to "breathe" or decanting it can also dissipate the dissolved sulfur.

Sulfur is one of the Seven Macrominerals for animals and plants Part of the chemical structure of several amino acids, sulfur aids in many biochemical processes. It helps protect the body from infection, blocks the harmful effects of radiation and pollution and slows down the ageing process. Sulfur-containing proteins are the building blocks of cell membranes, and sulfur is a major component of the gel-like connective tissue in cartilage and skin. Sulphur is found in cruciferous vegetables, eggs, milk and animal products. Source: Nourishing Traditions, by Sally Fallon, 2nd Edition (2001) .

As farmers and gardeners are aware, a deficiency of sulfur can bear obvious symptoms on plants, too. Sulphur deficiency symptoms in cereals will often, from a distance, resemble nitrogen deficiency, in that plants will have pale green to yellow leaves present. Similar symptoms are present in clover plants in that yellow leaves are present and when the deficiency becomes severe, the leaves will stand upright with a ‘cupped’ appearance. Canola leaves will ‘curl’ and whilst the leaves will turn yellow the veins will show a marked red to purple colouration.

Lack of molybdenum could be a cause of the sulfur intolerance Molybdenum is a minor trace element of which, according to NSW Agriculture, deficiencies occur mainly on acid soils throughout the coastal areas and on much of the southern tablelands of NSW. It is commonly deficient in our region, so if our food is also deficient in Molybdenum, we should beware: "People allergic to sulfites used as preservatives in salad bars, wine, and dried fruit may be helped by trace molybdenum. Molybdenum functions as a component in several enzymes including those involved in alcohol detoxification, uric acid formation, and sulfur metabolism. Molybdenum deficiency manifests itself as an inability to detoxify sulfites as the enzyme that detoxifies sulfites, sulfite oxidase, is molybdenum dependent. Molybdenum supplementation brought about complete resolution of symptoms of sulfite toxicity such as increased heart rate, shortness of breath, headache, disorientation, nausea, and vomiting. Since this study, a molybdenum deficiency has been suggested as a cause for sulfite sensitivities." (see www.life-enthusiast.com and www.doctormurray.com/ask/sulfites.asp ) According to other peer reviewed research, "Molybdenum deficiency may lead to amino acid intolerance, irritability, elevated urinary xanthine and sulfite, and reduced uric acid and sulfate. Condition cured by 160 microg Mo/d administered." (Aburnrad NN, Schneider AJ, Steel D, Rogers LS. Amino acid intolerance during prolonged total parenteral nutrition reversed by molybdate therapy. Am J Clin Nutr 198 ; 34:2551-2559 cited in www.imoa.info ).

If you have sulfur intolerance, why not see if extra Molybdenum can help you? Try drinking decanted, aged organic wine along with foods rich in molybdenum: peas, legumes, whole grains, pastas, dark-green leafy vegetables, yeast, milk, and organ meats!