The suitability of the simplified method of the analysis of coffee infusions on the content of Ca, Cu, Fe, Mg, Mn and Zn and the study of the effect of preparation conditions on the leachability of elements into the coffee brew

A fast and straightforward method of the analysis of coffee infusions was developed for measurements of total concentrations of Ca, Cu, Fe, Mg, Mn and Zn by flame atomic absorption spectrometry. Its validity was proved by the analysis of spiked samples; recoveries of added metals were found to be within 98–104% while the precision was better than 4%. The method devised was used for the analysis of re-distilled water infusions of six popular ground coffees available in the Polish market. Using the mud coffee preparation it was established that percentages of metals leached in these conditions varied a lot among analysed coffees, especially for Ca (14–42%), Mg (6–25%) and Zn (1–24%). For remaining metals, the highest extractabilities were assessed for Mn (30–52%) while the lowest for Fe (4–16%) and Cu (2–12%). In addition, it was found that the water type and the coffee brewing preparation method influence the concentration of studied metals in coffee infusions the most.