Specifications for reduced iron as a food additive

Abstract

The relative biological value of eight reduced iron powders manufactured by reduction with hydrogen or carbon monoxide, or by the electrolytic or carbonyl process, was determined by a rat hemoglobin repletion assay. The particle size distribution of these powders was determined by a photographicmicroscopic method. The solubility of five of the above powders in 0.290 (w/v) hydrochloric acid (pH about 1.2) at 37 "C with shaking in a 1-in. orbital stroke incubator shaker for 10 to 180 min was estimated.The relative biological value, as determined by a rat hemoglobin repletion assay, was generally found to increase with decreasing median particle sue and with the solubility at different times. It was concluded from the results that a reduced iron powder to be used as a food additive should meet the following specifications in order to ensure acceptable quality. (1) The iron content of the powder should not be less than 96%. (2) At least 95% of the powder should pass through a 325 mesh sieve having a pore size of 44 jtm. (3) At least 90% of the weight of the iron powder should be soluble in dilute hydrochloric acid as determined by the method described.Enrichment of flour with thiamin, riboflavin, niacin, and iron was introduced in Canada in 1953 (Chapman andCampbell, 1957). Concerning iron, the present regulation states that "enriched white flour shall be flour to which has been added iron in a harmless carrier, in such amount that one pound of enriched flour shall contain not less than 13.0 mg and not more than 16.5 mg of iron". In enriched bread the corresponding levels of iron are 8.0 and 12.5 mg per lb (Health and Welfare Canada, 1975). The stipulated amounts of iron in enriched flour and bread were based on the levels of iron in whole wheat.The milling industry has been using iron powder for enrichment of flour mainly because it is an economical, inert source of iron which does not affect the color or keeping quality of flour or bread. In recent years, however, the availability of iron from this source has been questioned (Cook et al., 1973;Rios et al., 1975). The biological availability of the reduced iron specified in Food Chemical Codex (National Research Council, 1972) was also not satisfactory (Shah and Belonje, 1973a). On the basis of rat assays of a number of iron powders it was concluded that at least 95% of the particles (by number) should be less than 10 jtm in size so that the powder would have an acceptable bioavailability. Similarly the absorption of fine (97% particles about 5 pm) iron powder by male and female volunteers was 9% whereas the comparable value for coarse iron powder (23% particles about 25 jtm and 48% larger than 30 pm) was only 3% (Hoglund and Reizenstein, 1969). In view of the these results there is a need to revise the specifications for iron powder used in foods, so that an acceptable bioavailability w i l l be ensured.These specifications can be based on particle size distribution (Shah and Belonje, 1973a) or solubility of an iron powder in dilute hydrochloric acid (Hinton et al...

The Usefulness of Elemental Iron for Cereal Flour Fortification: a Sustain Task Force Report

“…Several authors have evaluated solubility in dilute HCl, although the early studies of Pla and Fritz 38 found poor agreement between the solubility of a range of iron compounds in dilute HCl (pH 1.1) and their relative bioavailability in rat hemoglobin repletion studies. Shah et al 33 proposed that the suitability of elemental iron powders for food forti cation should be judged by their solubility in dilute HCl. To measure solubility, investigators recommended that 100 mg powder be shaken with 250 mL of 0.2% HCl (pH 1.2) at 37°C, and that only powders that are 90% soluble after 3 hours should be used for food forti cation.…”

“…They reported 44% solubility of electrolytic iron, 45% and 31% with two different batches of carbonyl iron, 8% for CO-reduced iron, and 8% each for two different batches of H-reduced iron. Using the method of Shah et al, 33 Forbes et al 40 reported that electrolytic iron was 75% dissolved in dilute HCl after 30 minutes and that the relative human absorption of electrolytic iron compared with ferrous sulfate was also 75%. The other compound tested in this study was ferric orthophosphate, which was only 3 to 4% soluble in dilute acid after 30 minutes but was 25% as well absorbed as ferrous sulfate in man.…”

Zinc Bioavailability Is Improved by the Micronised Dispersion of Zinc Oxide with the Addition of L-Histidine in Zinc-Deficient Rats

“…Particle size has previously been shown to have a positive influence on iron absorption. Motzok et al (21) found about a three-fold increase in bioavailability of reduced iron by reducing the particular size from 24-40 m to 7-10 m. Similar observations were also reported for electrolytic iron powder (24), ferric orthophosphate (24) and micronised dispersible ferric pyrophosphate (12). Concerning zinc compounds, decreasing MPS would increase zinc solubility, as observed in iron (20) and calcium (25).…”

Particle Size, Surface Area, and Amorphous Content as Predictors of Solubility and Bioavailability for Five Commercial Sources of Ferric Orthophosphate in Ready-To-Eat Cereal

“…Freely soluble iron forms such as ferrous sulfate have the highest bioavailability since iron and must be solubilized in gastric juice before it can be absorbed by the body [ 1 , 2 , 3 , 4 ]. However, soluble iron is also a pro-oxidant, has a metallic off-taste and reacts with many food components causing negative organoleptic changes and shortened shelf life [ 5 , 6 , 7 ]. As a result, less soluble and thus less reactive forms of iron are often chosen for food applications.…”