Effect of fermentation on iron, zinc, and calcium availability from iron-fortified dairy products

Iron, zinc, and calcium dialyzability and ascorbic acid (AA) concentrations were determined in milk, acidified milk, or yogurt fortified with ferrous sulfate (FS) or iron bis-glycinate (FBG) with or without AA addition in a 4:1 AA:Fe molar ratio. Milk fermentation or acidification caused an increase in iron availability from both iron sources. Highest availlability values were obtained for fermented products with added AA (18-fold increase compared to milk). AA oxidation during fermentation was minor. However, at 14 d of cold storage, AA degradation was close to 50% in FS-fortified yogurt and 35% in FBG-fortified yogurt. Nevertheless, iron dialyzability remained constant. Lactic acidification and fermentation also increased Zn availability, but Ca dialyzability was hardly increased by either treatment. AA addition did not modify Zn or Ca availability.