This precipitate is not suitable for a pigment until it is filtered, dried, crushed, heated to a high temperature and quenched in cold water. The second heating in a muffle furnace at 725 °C produces crystals of the right optical size.

Macromolecular oxidation was detected in proteins by the colorimetric measurement of Advanced Oxidation Protein Products (AOPP) and in lipids by the colorimetric quantification of malondialdehyde (MDA). Standard curves were run with chloramine-T and 1,1,3,3 tetraethoxypropane (TEP) for AOPP and MDA methods, respectively [29], [30], [31]. Values were normalized to initial protein content in samples, measured with Bradford reagent [32]. The standard deviation of at least six measures was calculated and p-value < 0.05 were considered significant.