A calibration graph was constructed, by plotting the concentrations of TA against the absorbance values. The linearity of assay was determined from five working standard solutions of TA in DI water (concentrations: 4.0– 20.0 g/ml), prepared in triplicates. The correla- tion (r2), intercept and slope of the calibration graph were calculated. The absorbance values of samples were observed and compared with those obtained from the calibration graph, to determine the amount of TA in samples. This experiment was performed in duplicates of three lots of samples.