Medium-strength acid (international name dihydrogen sulphite), which is formed when sulphur dioxide is introduced into water. Particularly in a warm environment, it tends to oxidise into the much more toxic and stronger sulphuric acid. The salts and esters of sulphurous acid are called sulphites or neutral or secondary sulphites, as well as hydrogen sulphites or formerly bisulphites or primary or acid sulphites. When sulphur dioxide is added to mash, must or wine, most of it is converted into sulphurous acid, with only a small proportion remaining as sulphur dioxide. The sulphurous acid immediately begins to split into sulphites and hydrogen sulphites. Both form compounds with various substances in the wine. Only when these processes are complete is the so-called free sulphurous acid present. The amount depends on the temperature and the pH value, but is usually around 20%. This means that around 80% of the sulphurous acid is present in the wine in bound form.
Antimicrobial and reducing effect
The sulphurous acid or sulphur dioxide has an antimicrobial effect, particularly against Acetobacter (acetic acid bacteria), lactic acid bacteria and wild yeasts. The hydrogen sulphites bind aroma-disrupting substances, including acetaldehyde (alcohol precursor). The sulphites react with the dissolved oxygen to form sulphates and have a reducing effect. The sum of free and bound sulphur dioxide (sulphurous acid) gives the total sulphur (also total sulphur dioxide or total sulphurous acid). The proportion in wine is measured using iodometry (free) and acidimetry (bound) and is given in milligrams per litre (mg/l). Excessive amounts of sulphur in wine are harmful to health, which is why there are legal limits. Even if these limits are adhered to, however, improper dry preservation of empty wooden barrels or over-sulphurisation of the wine can lead to the wine defect sulphuric acid firn.
Human organism
Sulphur is an important component of the human body and is involved in a number of metabolic processes. It is one of the most important functional carriers in the organism, is necessary for skin, hair and nails, keeps the tissue soft, reduces stress, has been proven to help with asthma, arthritis, rheumatism, internal and external inflammation, back and muscle pain and all allergies. Sulphur baths are generally recognised as beneficial to health and are also used by many people. The body of an adult with an...
