TY - JOUR

T1 - Calcium availability from whey mineral residues increased by hydrogen citrate

AU - de Zawadzki, Andressa

AU - Skibsted, Leif H.

PY - 2020

Y1 - 2020

N2 - Insoluble mineral residues from whey processing dominated by hydroxyapatite and calcium hydrogen phosphate were found to dissolve isothermally in aqueous sodium hydrogen citrate. Dissolution occurred spontaneously and the resultant homogeneous solutions were found to be supersaturated solutions in both calcium citrate and calcium hydrogen phosphate. Supersaturation was investigated by visual inspection combined with turbidity measurements and analyses of calcium and phosphorous by ICP. The maximal supersaturation was found to be proportional to total hydrogen citrate concentration. For 0.2 M hydrogen citrate, maximum calcium concentration was achieved in the first hours of dissolution resulting in the supersaturation of calcium hydrogen phosphate with a factor of 10. Calcium citrate rather than calcium hydrogen phosphate precipitated from the supersaturated solutions and the time elapsing before precipitation began, increased with increasing concentrations of excess of hydrogen citrate. This lag phase for precipitation ranged from several hours for 0.2 M hydrogen citrate to more than a day for higher hydrogen citrate concentrations, for which the solutions were saturated in calcium hydrogen phosphate and became supersaturated only in calcium citrate due to the strong binding of calcium by citrate. The appearance and decay of supersaturation was kinetically studied in order to provide the background for future exploration of whey minerals in functional foods for improved calcium nutrition.

AB - Insoluble mineral residues from whey processing dominated by hydroxyapatite and calcium hydrogen phosphate were found to dissolve isothermally in aqueous sodium hydrogen citrate. Dissolution occurred spontaneously and the resultant homogeneous solutions were found to be supersaturated solutions in both calcium citrate and calcium hydrogen phosphate. Supersaturation was investigated by visual inspection combined with turbidity measurements and analyses of calcium and phosphorous by ICP. The maximal supersaturation was found to be proportional to total hydrogen citrate concentration. For 0.2 M hydrogen citrate, maximum calcium concentration was achieved in the first hours of dissolution resulting in the supersaturation of calcium hydrogen phosphate with a factor of 10. Calcium citrate rather than calcium hydrogen phosphate precipitated from the supersaturated solutions and the time elapsing before precipitation began, increased with increasing concentrations of excess of hydrogen citrate. This lag phase for precipitation ranged from several hours for 0.2 M hydrogen citrate to more than a day for higher hydrogen citrate concentrations, for which the solutions were saturated in calcium hydrogen phosphate and became supersaturated only in calcium citrate due to the strong binding of calcium by citrate. The appearance and decay of supersaturation was kinetically studied in order to provide the background for future exploration of whey minerals in functional foods for improved calcium nutrition.

KW - Calcium availability

KW - Calcium citrate supersaturation

KW - Hydrogen citrate

KW - Whey minerals

U2 - 10.1016/j.foodres.2020.109372

DO - 10.1016/j.foodres.2020.109372

M3 - Journal article

C2 - 33233074

AN - SCOPUS:85086067228

VL - 137

JO - Food Research International

JF - Food Research International

SN - 0963-9969

M1 - 109372

ER -