Effect of Acid Pretreatment on the Stability of Citric and Malic Acid Complexes With Various Iron Sources in a Wheat Flake Cereal

Abstract

An in vitro incubation at pH 2 of citric and malic acids with each of five iron sources [(hydrogen (HRI) and electrolytically reduced elemental iron (ERI), ferric chloride (FeCl3), ferrous sulfate (FeSO4) and ferric orthophosphate (FOP)] at a 10:1 molar ratio (acid:iron) was evaluated for its effect on iron solubiliza‐tion in a wheat flake cereal subjected to a sequential gastrointestinal pH treatment from endogenous pH (E) to 2 to 6. Citric acid maintained significantly more complexed and ionic iron (Fe+3) in solution than malic acid, with and without incubation, through the final stage of the sequential pH treatment with each of the five iron sources. However, the malate treated samples were affected less than the citrate by acidification from pH E to 2, with less of the soluble complexed iron being insolubilized and significantly more ionic iron (Fe+2) being produced. Incubation significantly enhanced the iron solubilizing capacity of citrate at all stages of the sequential pH treatment with HRI and at pH E with ERI, FeCl3 and FeSO4, As well, incubation increased the iron solubilization properties of malate at all stages with FeSO4 and at E and 2 with HRI and ERI. These results indicate that acid incubation to form an organic acid‐iron chelate, particularly with elemental iron, has the potential to improve cereal iron fortificant bioavail‐ability.

Organic Acids Influence Iron Uptake in the Human Epithelial Cell Line Caco-2

“…Oxaloacetic acid, which is a four-carbon dicarboxylic acid with a keto group, showed a similar response on iron absorption as the other acids in group C (data not shown). The more positive effect on ferric iron, as compared with ferrous, by the organic acids in group C is consistent with data by Nadeau and Clydesdale ( , ), who studied the solubility of iron in combination with citric and lactic acid together with wheat flakes. The large difference between lactic and propionic acid regarding level of impact on iron absorption suggests that the hydroxyl group of lactic acid again plays a role in the complex formation.…”

EFFECTIVENESS of ORGANIC CHELATORS IN SOLUBILIZING CALCIUM AND ZINC IN FORTIFIED CEREALS UNDER SIMULATED GASTROINTESTINAL pH CONDITIONS

“…Rumenapf and Schwille (1987) obtained a decrease in intestinal calcium absorption of healthy men when citrate was administered orally at a citrate:Ca molar ratio of 4: 1 , the Ca-citrate complex being less absorbable than ionized calcium. Malic acid has been shown to complex iron (molar ratio 10: 1) in cereals during an acid incubation period of lh, in a form which was stable through neutralization (pH 6) (Nadeau and Clydesdale 1986). A molar ratio of 1O:l (ma1ate:zinc) was also chosen in this study because it might be found in food fortification programs, and because it was effective with citrate in promoting calcium and zinc solubilization.…”

“…The 1igand:iron molar ratio used in that study was rather high (290:l). Nadeau and Clydesdale (1986) found that a 10: 1 citrate:iron molar ratio promoted in vitro solubilization of iron. Gillooly et al (1983) noted an improvement of the geometric mean of iron absorption by human subjects from a basic rice meal following the addition of citric, ascorbic, malic, and tartaric acids.…”