Favoured steriliser for Cidermakers, as the potassium salt leave little ‘aftertaste’.Potassium metabisulfite is one of the most important winemaking compounds. It is an antioxidant and bactericide that releases sulfur dioxide into wine must. Use 1/4 teaspoon per five gallons to add 50 ppm. Or, mix 1/4 pound in 1 quart of water to make a stock solution; 1 teaspoon of stock solution in 1 gallon of must yields 50 ppm sulfur dioxide