The sour, salty taste of sodium accentuates beer's flavor when it is found in reasonable concentrations. It is poisonous to yeast and harsh tasting when it is in excess. Usually found at levels of 2 to 100 ppm, it is very soluble. Carbonate is a strongly alkaline buffer formed by the reaction of atmospheric carbon dioxide with hydroxides of alkaline-earth and alkali metals. Bicarbonates form by the reaction of a carbonate ion with a molecule each of carbon dioxide and water.
Carbonates resist increases in mash acidity by neutralizing acids as they are formed.
It also hinders gelantinization of starch by alpha amylase, impedes trub flocculation during the cold break, and increases risk of contamination in the ferment. It contributes a harsh, bitter flavor overwhelming in delicate lagers, and carbonate in excess of 200 ppm is tolerable only when a dark-roasted malt is used to buffer its excessive acidity. Preferably, carbonate should be less than 50 ppm when pale malt or infusion mashing is used. Sulfate is weakly basic, and its alkalinity is overcome by most acids. It is fairly soluble.