Understanding Sulphites: Their Role, Presence in Food, and Potential Side Effects

Sulphites, along with sulfur dioxide, are commonly used in the food industry as antimicrobial, antienzyme, and antioxidant preservatives. They are used to inactivate harmful microorganisms such as mold, yeast, and bacteria, and to preserve the color of food, protecting it from browning. They come in different forms and are often referred to by their E numbers, ranging from E220 (Sulfur dioxide) to E228 (Potassium acid sulphite).

Sulphites in Food Preservation

One of the primary applications of sulphites is in the winemaking process. They inhibit the fermentative action of yeasts present on the skin of grapes, which would otherwise impart unwanted aromas to the wine. After these "wild" microorganisms are inactivated, strains of selected yeasts, which are insensitive to the action of sulphites, are added to the must to give the wine its desired aroma.

Sulphites are also used before bottling to stop fermentation processes and improve wine conservation. However, their use is not limited to winemaking. They are found in a variety of food products, including wine vinegar, cider, beer, fruit juices, jellies, dehydrated fruit, dried fruit, seafood, preserved vegetables, and certain meat products.

Despite their utility, the use of sulphites in meat foods is strictly limited as they significantly reduce the bioavailability of thiamine (vitamin B1). The acceptable daily intake (ADI) of sulfur dioxide has been set at 0.7 mg/kg/day.

Potential Side Effects of Sulphites

While sulphites are generally recognized as safe (GRAS) for consumption by healthy individuals, they can cause problems for certain "sensitive" people. The reaction of sulphites with gastric acidity generates sulfur dioxide, one of the most effective gases in inducing attacks of bronchospasm in asthmatic subjects.

People allergic to aspirin are also at a higher risk of suffering from this type of reaction. Overall, sulphites are estimated to cause problems in approximately 0.05-1% of the population, with a significantly higher risk for asthmatic individuals (in whom the prevalence can reach up to 5%).

The symptoms of sulphite sensitivity, which are not considered a true allergy but rather an intolerance, can include migraines, asthma attacks, hives, nausea, vomiting, intense sweating, hot flashes, and hypotension. These symptoms typically appear within 15-30 minutes of ingestion.

Mandatory Labeling of Sulphites

Due to the potential allergenic activity of sulphites and sulfur dioxide, food producers are required to declare the presence of these substances on the label. This obligation applies if the concentration of sulfur dioxide in the food exceeds 10 mg/L or 10 mg/kg. Food products exceeding this threshold could be subject to recall or fine actions.

In conclusion, while sulphites play a crucial role in food preservation, their potential side effects, particularly for sensitive individuals, necessitate caution. The mandatory labeling of sulphites in food products is an important measure to safeguard consumers, allowing those who are sensitive to make informed choices about what they consume.

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