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Published on: March 6, 2014
A simple phosphorus determination in walnuts and assessment of the assimilable fraction
Pablo Fuentes-Soriano1, Dolores Bellido-Milla2, Juan José García-Guzmán3
1Department of Analytical Chemistry, Faculty of Sciences, University of Cadiz, Campus Rio San Pedro S/N, Puerto Real, 11510, Cadiz, Spain.
Abstract:
In this work, a method for the determination of phosphorus in walnuts has been developed due to the fact that there is no specific method for this purpose. A closed-vessel microwave-assisted digestion of the samples was optimized and a modified molybdenum blue spectrophotometric method was carried out with excellent precision and selectivity. To differentiate assimilable and non-assimilable phosphorus, an easy extraction procedure using 1 M NH4Cl was used. FTIR spectra ensured that the phytate extraction was successful. A sampling of thirteen different walnuts available to consumers from different crops and geographical origin was performed. Comparative statistical tools to differentiate walnuts were also carried out. Significant differences based on total content of phosphorus were obtained. Finally, a correlation study between total phosphorus concentration and the non-assimilable fraction showed a non-linear relationship (R2 = 0.435). Therefore, in relation to consumer health the total phosphorus determination must be complemented with information about assimilable phosphorus.
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