Studies of polyphosphate composition and their interaction with dairy matrices by ion chromatography and 31P NMR spectroscopy

International audienceThe use of ion-exchange chromatography and 31P-nuclear magnetic resonance (NMR) to analyse the composition and the chain length of phosphate emulsifying salts were studied, as well as the impact of these salts in dairy products. Ion chromatography was more appropriate than 31P-NMR to study polyphosphate composition in complex environments, whereas interactions between phosphate species and dairy components were elucidated by 31P-NMR. Phosphate species interacting with calcium, as well as the percentage of chelated calcium, were identified using 31P-NMR. Thus, ion chromatography and solid-sate 31P-NMR could be used as complementary methods to study compositions of polyphosphate blends and their interactions with dairy matrices

Iron fortification of skim milk. Mineral and 57Fe Mössbauer study

International audienceReconstituted skim milk was fortified at 2, 5, 10 and 20 mmol Fe kg(-1) with ferric and ferrous chloride iron with or without reversible acidification by injection of CO2 under pressure. Carbonation improved transfer of iron from the soluble to the colloidal phase and accelerated ferrous iron oxidation. Fe-57 Mossbauer spectra of the freeze-dried casein micelles collected by centrifugation demonstrated that iron is present in a distorted octahedral coordination and is chelated by phosphate rather than citrate. Milk iron fortification induced several changes in the mineral component of the casein micelles, which are explained by the formation of a tertiary complex: inorganic phosphate-iron-organic phosphate