Zinc and Calcium Solubility from Instant Tea and Coffee With and Without the Addition of Milk

Abstract

The effect of tea and coffee, with and without milk, on the solubility of added zinc and calcium after a sequential pH change to 2 and 6 was investigated. The addition of milk did not decrease the solubility of endogenous zinc or calcium in tea but did in coffee. Liquid tea decreased (P<0.01) the solubility of added zinc but not of added calcium. However, the addition of milk to tea containing added zinc and calcium decreased (P<0.01) the solubility of both elements. This decrease reached a plateau after 100 or 150 ml of milk was added to 100 or 50 ml of tea, respectively. In coffee, when the minerals were added, the solubility of zinc did not depend on the presence of milk, whereas the solubility of calcium decreased proportionally to the amount of milk added (P<0.05).