Chemical Forms of Iron, Calcium, Magnesium and Zinc in Coffee and Rat Diets Containing Coffee

Abstract

Chemical forms of iron, calcium, magnesium and zinc (mineral profiles) were measured in brews of regular and decaffeinated instant coffee and diets containing these coffees. Iron, calcium and magnesium were highly soluble (90–98%) in brews of both coffees and zinc could not be detected. All ionic iron was in the ferric state and 40–48% of total iron was in soluble complexes. Iron was less soluble in a rat diet containing regular instant coffee (57%) and a diet containing decaffeinated coffee (62%) than in a control diet (74%). Diets had the same amounts of ferric and ionic iron (43–45%). More iron was in soluble complexes in control (29%) and decaffeinated coffee (21%) diets than a regular coffee diet (12%). Calcium had low solubility (12–14%) while magnesium had high solubility in diets. Zinc was more soluble in both coffee diets than in the control. Some mineral profiles of rat diets containing coffee were similar to mineral profiles of coffee alone. Differences indicated that mixing coffee into diets induced changes in coffee. Mineral profiles of diets predicted some results of a rat bioavailability assay.