Mineral Composition of Fruits in Different Walnut (Juglans regia L.) Cultivars

Abstract

Walnuts are considered to be a good source of dietary minerals. Mineral composition was determined in nine walnut cultivars (‘Mihaela’, ‘Roxana’, ‘Velnita’, ‘Geoagiu 65’, ‘Jupanesti’, ‘Valcor’, ‘Valmit’, ‘Valrex’, ‘Argesan’) originated from Romania. A Milestone digestion microwave system was used for mineralization of solid samples. Microelements: Na, Ca, Mg, Fe, Mn, Cu, Se, Al, Cr, Zn, Sr and Rb were determined by using ICP-MS as measurement tool, and K content was determined with an atomic absorption spectrometer in flame, by using as excitation source the cavitar cathode lamp for potassium. Mineral elements content presented significant differences from a cultivar to another. Potassium content has varied between 357.1 mg/100g in ‘Valmit’ cultivar, and 499.6 mg/100g, in ‘Geoagiu 65’ cultivar, recording significant differences from the average (414.0 mg/100g) in ‘Velnita’, ‘Roxana’ and ‘Argesan’ cultivars. Magnesium content varied between 189.2 mg/100 g in ‘Mihaela’ cultivar and 278.1 mg/100 g in ‘Argesan’ cultivar, significant differences from the average (216.6 mg/100g) were obtained in cultivars ‘Geoagiu 65’, ‘Valrex’, ‘Argesan’. The order of nutritive elements depending on their content/100 g of produce was K>Mg>Ca>Mn>Fe>Cu>Zn>Na>Cr>Al>Rb>Sr. Comparing obtained data with the ones existing in the literature, Romanian walnut cultivars proved to be important sources of nutritive elements, and walnut kernel consumption can contribute to a well balanced diet.