2.2.5. Determination of pH
The pH was determined after mixing a 10 g sample with 90 mL distilled water (1/10 sample/water) and the pH value measurements were carried out using a Hanna pH meter (Hanna HI-9321, Woonsocket, Rhode Island, USA), equipped with a FC220B electrode (Hanna HI-9321, Woonsocket, Rhode Island, USA), after calibration with standard buffers of pH 4.0 and 7.0 [26