RESUMO
Rheological behaviour of enzyme clarified sapota (Achras sapota L.) juice at different temperatures (10 to 85 °C) and total soluble solid content (10.2 to 55.6 °brix) corresponding to a water activity (aw) (0.986 to 0.865) was studied using controlled stress rheometer by coaxial cylinders attachment. The rheological parameter shear stress (Pa) was measured upto a shear rate of 1,000 s(-1). The investigation showed that the enzyme clarified sapota juice and its concentrates behaved like a Newtonian liquid and the viscosity (η) values were in the range 4.340 to 56.418 mPa s depending upon temperature and concentration studied. The temperature dependency of viscosity of enzyme clarified sapota juice was described by Arrhenius equation (r > 0.94) and activation energy (Ea) for viscous flow was in the range 5.218 to 25.439 KJ/mol depending upon concentration. The effect of total soluble solid content on flow activation energy was described by exponential relationship (r > 0.95, rmse% <13.5, p < 0.01) and that of water activity was described by power law relation (r > 0.99, rmse% <5.80, p < 0.01). The effect of total soluble solid content on viscosity of enzyme clarified sapota juice followed second order exponential type relationship (r > 0.99, rmse% < 3.53) at the temperature used. The effect of water activity on viscosity of enzyme clarified sapota juice followed power law equation (r > 0.98, rmse% < 4.38). A single equation representing combined effect of temperature and total soluble solid content/water activity on viscosity of enzyme clarified sapota was established.