The principle mechanism of sodium metabisulfite's action
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2022-05-23 15:19:24.310
Bleaching agents are divided into oxidative bleaching agents and reducing bleaching agents. Sodium metabisulfite is a reducing bleach.
The purpose of sodium metabisulfite to achieve bleaching is to use the pigment to fade by reduction. The color of most organic substances is produced by the chromophores contained in their molecules. The chromophore contains unsaturated bonds. Reducing the bleach will release hydrogen atoms, which can make the unsaturated bonds contained in the chromophore into single bonds, so that the organic matter will lose its color. The existence of ferric ions can make food brown, and reducing bleach can be added to make ferric ions into ferrous ions, which can prevent food from browning.
Sodium metabisulfite uses sulfite addition reaction to fade, so as to achieve the purpose of bleaching. The addition reaction of anthocyanins can be bleached to fade. However, this reaction is reversible, and the sulfurous acid can be removed by heating to regenerate the anthocyanins and restore the original red color.
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