The instrument was calibrated against a white-standard. Measurements were individually taken for ten samples per treatment and the average of ten readings was calculated. The color difference ΔE was calculated from the L, a, b parameters, using the Hunter–Scotfield equation: ΔE = (Δa)2 + (Δb)2 + (ΔL)2.2.6. Statistical analysisAnalysis of variance (ANOVA) was performed in a completely randomized design, using Duncan's Multiple Range Test. All determi- nations were done at least in triplicate and all were averaged. The confidence limits used in this study were based on 95% (pb0.05)