where Y is the response variable (TMA or TPC); ˇ0is an inter-cept term; ˇ1and ˇ2are linear coefficients; ˇ12is interactioncoefficients; T and A are the independent variables representingthe sonication time and amplitude. The coefficient of determina-tion (R2), response surface and contour plots were to examine andevaluate the models.