title: 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.
abstract: Ferric orthophosphate (FePO₄) has had limited use as an iron fortificant in ready-to-eat (RTE) cereal because of its variable bioavailability, the mechanism of which is poorly understood. Even though FePO₄ has desirable sensory properties as compared to other affordable iron fortificants, few published studies have well-characterized its physicochemical properties. Semi-crystalline materials such as FePO₄ have varying degrees of molecular disorder, referred to as amorphous content, which is hypothesized to be an important factor in bioavailability. The objective of this study was to systematically measure the physicochemical factors of particle size, surface area, amorphous content, and solubility underlying the variation in FePO₄ bioavailability. Five commercial FePO₄ sources and ferrous sulfate were added to individual batches of RTE cereal. The relative bioavailability value (RBV) of each iron source, determined using the AOAC Rat Hemoglobin Repletion Bioassay, ranged from 51% to 99% (p < 0.05), which is higher than typically reported. Solubility in dilute HCl accurately predicted RBV (R² = 0.93, p = 0.008). Amorphous content measured by Dynamic Vapor Sorption ranged from 1.7% to 23.8% and was a better determinant of solubility (R² = 0.91; p = 0.0002) than surface area (R² = 0.83; p = 0.002) and median particle size (R² = 0.59; p = 0.12). The results indicate that while solubility of FePO₄ is highly predictive of RBV, solubility, in turn, is strongly linked to amorphous content and surface area. This information may prove useful for the production of FePO₄ with the desired RBV.
authors.affiliation: Kellogg Company, W.K. Kellogg Institute for Food and Nutrition Research, Battle Creek, 2 Hamblin Avenue, Battle Creek, MI 49015, USA. rsdmalone@gmail.com.
authors.forename: Robin S
authors.initials: RS
authors.lastname: Dickmann
authors.affiliation: Department of Food Science and Human Nutrition, Michigan State University, 469 Wilson Road, East Lansing, MI 48824, USA. stragale@anr.msu.edu.
authors.forename: Gale M
authors.initials: GM
authors.lastname: Strasburg
authors.affiliation: Department of Food Science and Human Nutrition, Michigan State University, 469 Wilson Road, East Lansing, MI 48824, USA. dromsos@anr.msu.edu.
authors.forename: Dale R
authors.initials: DR
authors.lastname: Romsos
authors.affiliation: Kellogg Company, W.K. Kellogg Institute for Food and Nutrition Research, Battle Creek, 2 Hamblin Avenue, Battle Creek, MI 49015, USA. lori.wilson@kellogg.com.
authors.forename: Lori A
authors.initials: LA
authors.lastname: Wilson
authors.affiliation: Kellogg Company, W.K. Kellogg Institute for Food and Nutrition Research, Battle Creek, 2 Hamblin Avenue, Battle Creek, MI 49015, USA. gracehlai@hotmail.com.
authors.forename: Grace H
authors.initials: GH
authors.lastname: Lai
authors.affiliation: Kellogg Company, W.K. Kellogg Institute for Food and Nutrition Research, Battle Creek, 2 Hamblin Avenue, Battle Creek, MI 49015, USA. hsimin.huang@kellogg.com.
authors.forename: Hsimin
authors.initials: H
authors.lastname: Huang
mesh_terms: D000284:Administration, Oral; D000821:Animal Feed; D000818:Animals; D001682:Biological Availability; D015415:Biomarkers / Q000097:blood; D003677:Deficiency Diseases / Q000097:blood / Q000188:drug therapy*; D004195:Disease Models, Animal; D002523:Edible Grain / Q000737:chemistry*; D005290:Ferric Compounds / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics*; D005527:Food, Fortified / Q000032:analysis*; D006397:Hematinics / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics*; D006454:Hemoglobins / Q000378:metabolism; D007501:Iron / Q000097:blood; D000090463:Iron Deficiencies; D008297:Male; D010316:Particle Size; D017207:Rats, Sprague-Dawley; D012995:Solubility; D013499:Surface Properties
chemical_list: D015415:Biomarkers; D005290:Ferric Compounds; D006397:Hematinics; D006454:Hemoglobins; D007501:Iron; C035885:ferric phosphate
keywords: X-ray diffraction; amorphous content; bioavailability; dynamic vapor sorption; ferric orthophosphate; particle size; physicochemical properties; reduced iron; solubility; surface area