2.4. MIC and ICP-MS determination of elements
Samples of WPC, WPH, WPI, and casein were digested following the operational parameters described in a previous study (Pereira Barbosa et al., 2013). Pellets of samples were placed on a quartz holder with a small disc of filter paper. A 6 mol L−1NH4NO3 solution (50 μL) was added to the filter paper followed by the introduction of a quartz holder in a quartz vessel previously charged with 6 mL of absorbing solution (10–100 mmol L−1 NH4OH). After closing and capping the rotor, vessels were pressurized with 20 bar of oxygen.