Use and Removal of Sulfite by Conversion to Sulfate in the Preservation of Salt-Free Cucumbers†

Abstract

Cucumbers (Cucumis sativus) were microbiologically stable in cover liquid containing 300 ppm of added sodium metabisulfite (calculated as SO2), 20 mM calcium chloride, and HCl to give an equilibrated pH of 3.5. The sulfur(IV) oxoanions could be easily removed to nondetectable levels (<3 ppm) by addition of an equimolar amount of hydrogen peroxide, which rapidly converted S(IV) primarily to sulfate ions. When sulfur(IV) oxoanions were removed from stored fresh cucumbers, 85% of the added metabisulfite could be accounted for by formation of sulfate ions. If cucumbers were heated before addition and removal of sulfur(IV) oxoanions, 96% of that added was converted to sulfate by hydrogen peroxide. Preservation of cucumbers in this way does not require fermentation, so addition of salt is not needed to select for lactic acid bacteria.