The pH of the resultant suspension was measured after 10 min at room temperature (about 20±2 °C) using a Hanna pH metre (Hanna HI-9321,Woonsocket, RI), equipped with a FC220B electrode (Hanna HI-9321), calibrated with standard buffers of pH 4.0 and 7.0. Three readings were made for each sample and the mean recorded (AOAC, 1984).