The flour sample was digested by oxidation mixtures of HNO3 and H2SO4, and the minerals in the flour samples were dissolved in the digestive solution.
The contents of Fe, Zn, and Ca in the digestive solution were determined with a Varian spectr AA220 atomic absorption spectrometer (Varian, Inc., Palo Alto, USA).
Digestion and analysis were done in triplicate for each sample.