Figure D-1 Major food sources of iron ha fine food supply. Source: LSRO (1989).

dilute acids are ferrous fumarate, ferrous succinate, and ferric saccharate. Many of the iron preparations commonly used for food fortification are poorly soluble in water and poorly soluble in dilute acid (e.g., ferric pyrophosphate and ferric orthophosphate, which were used in the past, and elemental iron powders of intermediate particle size).

In the presence of oxygen, water-soluble forms of iron react with various components of food to produce oxidative rancidity. Such forms of iron can be used to fortify foods that can be packaged to limit prolonged contact with oxygen (e.g., infant formulas). Dry cereals packaged in cardboard boxes (including cereals specifically marketed for infants) permit exchange of air between package contents and the environment, and it is therefore not feasible to fortify them with ferrous sulfate or with most other iron salts known to have good bioavailability (Coccorilli et al., 1976; Hurrell, 1984). In the United States, most dry infant cereals are fortified with a metallic iron powder, specifically, electrolytic iron.

The bioavailabilities of metallic iron powders are closely related to particle size and solubility (Björn-Rasmussen et al., 1977). Metallic iron powders of extremely small particle size are readily soluble in dilute acid (Björn-Rasmussen et al., 1977) and have good bioavailability (Björn-Rasmussen et al., 1977; Rios et al., 1975). Unfortunately, the greater the solubility (and, presumably, the greater the bioavailability) of a metallic iron powder, the greater its chemical reactivity and the less suitable it is for food fortification. Circumstantial evidence has led several authors to conclude that electrolytic iron powder of the