Generality
What are sulphites and why are they used?
Sulfur dioxide (E220) and sulphites (from E221 to E228) are used in the food industry as antimicrobial, anti-enzyme and antioxidant preservatives. As such, they are used to inactivate molds, yeasts and bacteria, as well as to preserve the color of foods and protect them from browning.
Sulfur dioxide is a gas and can be used as such or in liquid form, while sulphites appear as stable powders, highly reactive in an aqueous environment.
In common parlance, the term sulphites includes the sulfur dioxide and some of its inorganic salts (sulphites, bisulfites and metabisulfites) used as additives for food preparation and preservation:
- E220 (Sulfur dioxide)
- E221 (Sodium sulfite)
- E222 (Sodium bisulfite)
- E223 (Sodium metabisulfite)
- E224 (Potassium metabisulfite)
- E225 (Potassium sulphite)
- E226 (Calcium sulfite)
- E227 (Calcium bisulphite)
- E228 (Acid sulphite potassium).
Sulfur dioxide and sulphites in wine
Sulfur dioxide and sulphites are widely used to keep the color of fruit and vegetables intact, although the main and most ancient application lies in the wine-making process. The sulphites - which once immersed in an acid solution release sulfur dioxide - have the ability to inhibit the fermentative action of the yeasts present on the skin of the berries, which would give unwanted aromas to the wine.
After inactivating these "wild" micro-organisms, selected yeast strains are added to the must, insensitive to the action of sulphites and capable of giving the wine the sought-after aroma. Some of them even have the ability to generate them (which is why the presence of sulphites in wine and beer is however, a priori, a natural fact).
Before bottling, the wine can again be treated with sulphites to stop the fermentation processes and improve their conservation.
Food
What are foods rich in sulphites?
- Wine (normally it contains more white than red and sweet than dry)
- Wine vinegar
- Cider
- Beer
- Fruit juices
- Jellies
- Dehydrated fruit
- Dried fruit (especially the peeled one)
- Candied fruit
- Frosted fruit
- Seafood
- Shrimps and other crustaceans
- Codfish
- Preserved vegetables (freeze-dried, dried, frozen, in oil, vinegar, etc.)
- Dried mushrooms
- Raisins
- Meat products like hot dogs and hamburgers.
By law, the use of sulphites in meat foods is severely limited, as they considerably reduce the bioavailability of thiamine (vitamin B1).
Note : The ADI (acceptable daily intake dose) of sulfur dioxide was set at 0.7 mg / kg / day. In general, in the developed countries the daily intake does not exceed 20 mg.
Side effects
Sulphite reactions: intolerance or allergy?
Allergic reaction to sulphites
Sulphites are on the list of the nine most common food allergens, although the body's most common reaction to these additives (which we will see better in the next section) is not actually considered a true allergy. In fact, only a small slice of the population is actually positive for skin allergy testing with a clear involvement of the immune system (IgE-mediated). Anaphylaxis and other serious reactions are however quite rare.
Sulphite intolerance
In healthy individuals, at the doses commonly used in the food industry, sulfur dioxide is included in the list of GRAS (Generally Recognized as Safe) active ingredients; it is in fact a natural compound, also produced by our body during the metabolism of some amino acids and easily inactivated by endogenous detoxification systems (thanks to the sulfite-oxidase enzymes that transform it into the harmless sulfate).
Curiosity: Deficit Cofactor of Molybdenum (MoCo)
The high content of sulphites in the blood and urine of children can be caused by the so-called co- factor deficiency of molybdenum (75% correlated to Sulfite Oxidase Deficiency Encephalopathy), which if untreated can lead to neurological damage and early death .
The treatment, which requires daily injections, has been made available since 2009.
Despite this safety in use, sulfur dioxide and sulphites can cause some, sometimes serious, problems for people who are "sensitive". Sulfur dioxide, or sulfur dioxide, is a gas with an acrid, pungent odor that develops when sulfur is burned. Sulphites, on their part, react with acids developing sulfur dioxide, which has whitening, bactericidal, but also highly irritating properties. However, it must be said that - once added to the food product - sulphites tend to combine irreversibly with some of its components, becoming largely inactive, therefore not subject to evaporation.
The contact of food sulphites with gastric acidity generates a certain amount of sulfur dioxide, which represents one of the most effective gases in inducing bronchospasm attacks in asthmatic subjects.
Aspirants allergic to aspirin are particularly at risk of suffering this kind of reaction. In general, it is estimated that sulphites cause problems at about 0.05-1% of the population (depending on the sources and dosages), with a significantly higher risk for asthmatic individuals (in which the prevalence can reach 5% ). In this context the term sensitivity is used, since we cannot speak of a real allergy, but of an intolerance that triggers pseudo-allergic symptoms, including the characteristic "circle on the head" (to which it contributes, often to a dominant extent, also the alcohol).
In addition to benign migraines, we must add the already mentioned risk of asthma crises (bronchospasm), but also of hives, nausea, vomiting, intense sweating, hot flushes and hypotension. Symptoms generally occur within 15-30 minutes of ingestion.
Curiosity: Asthma from sulphites
In 1986, after the identification of numerous cases of asthma induced by the intake of sulphites contained in vegetables and fruit, the FDA (Food and Drug Administration) prohibited the use of these additives on fruit and vegetables intended for consumption as raw food; the only exception is the use of sulphites on minimally processed or ready-to-fry potatoes, where the use of sulfite is still allowed.
Precisely because of the potential similallergenic activity of sulphites and sulfur dioxide, food manufacturers have for some years now been obliged to declare the presence of these substances on the label; in particular, this obligation applies if the concentration of sulfur dioxide in the food exceeds 10 mg / L or 10 mg / kg (result of sulphites naturally present in foods added to added ones). Food products that exceed this threshold will be subject to possible recall or sanction actions.
