Metabiszulfitek

Metabiszulfitek are inorganic compounds with the general formula M2S2O5, where M typically represents an alkali metal like sodium or potassium. Sodium metabisulfite (Na2S2O5) is the most common form. They are produced by reacting sulfur dioxide with a metal hydroxide or carbonate. Metabiszulfites are characterized by their strong sulfurous odor and are typically found as white crystalline powders.

In aqueous solutions, metabiszulfites readily hydrolyze to form bisulfite ions (HSO3-) and then sulfite ions (SO32-), which are the actual active species. This reaction is pH-dependent, with lower pH favoring the formation of bisulfite. The primary chemical property of metabiszulfites is their reducing ability and their capacity to act as preservatives.

Metabiszulfites are widely used in various industries. In the food industry, they serve as antioxidants and preservatives, preventing spoilage and discoloration in products like dried fruits, wines, and processed potatoes. They achieve this by scavenging oxygen and inhibiting the activity of enzymes that cause browning. In winemaking, they are crucial for stabilizing the wine and preventing oxidation and microbial spoilage. They are also used in photography, as bleaching agents in the textile industry, and in chemical synthesis.

While generally safe when used within permitted limits, metabiszulfites can cause allergic reactions in sensitive individuals, particularly asthmatics. Symptoms can range from mild skin irritation to severe respiratory distress. Regulatory bodies worldwide set limits on their use in food products to minimize these risks.