Reduction of soluble oxalate in cocoa powder by the addition of calcium and ultrasonication

Abstract

Cocoa bean and its products are high-value, nutritious foods, but also contain considerably amounts of soluble oxalate that is linked with increased incidences of forming kidney stones. This study investigated the potential of reducing soluble oxalate contents in cocoa powder by mixing with three calcium salts (calcium carbonate CaCO3, calcium chloride dihydrate CaCl2.2H2O and calcium sulfate dihydrate CaSO4.2H2O), three milk varieties (full-cream, low-fat and high-calcium milk) and ultrasonication at different combinations of temperatures (40, 60 and 80 °C) and time (1–6 h). Analyses of soluble oxalate were carried out using Ultra High-Performance Liquid Chromatography (UHPLC). Among six calcium sources, CaSO4.2H2O and high-calcium milk were the most effective treatments that reduced 31.78 % and 21.14 % soluble oxalate in cocoa powder, respectively. Ultrasonication reduced up to 39.96 % soluble oxalate in cocoa powder, but the efficiencies greatly depended on temperatures, durations and the interactive effects between the two factors. It was concluded that the addition of calcium using its salts or milk products and ultrasonication were potential methods to reduce soluble oxalate and make cocoa powder safer for consumers at risks of hyperoxaluria.