Abstract
Isobaric and isothermal semi-logarithmic survival curves of natural microflora in apple juice treated with high-pressure carbon dioxide at 7, 13, and 16 MPa pressures and 35, 50, and 60 degrees C temperatures were fitted with a nonlinear equation to find the values of the coefficient b(P), b(T), n(P), and n(T). Profiles of the model parameters were obtained as a function of pressure and temperature. The model fitted with good agreement (R-2 > 0.945), the survival curves. An empirical equation was proposed to describe the combined effects of pressure and temperature. The equation, derived from a power law model, was written in the form: log(10)S (t) = -log(e) [C-0 + C-1 x exp (K-T x (T - T-C)) - C-2 x exp (K-P x (P - P-C))] x t ((C)(3) (x T2+ C)(4) (x T+ C)())(5). The proposed model fitted the experimental data well. At 7 MPa and 50 and 60 degrees C, 13 MPa and 35 and 60 degrees C, 16 MPa and 35 degrees C, the model provided log(10) reduction residual values (observed value - fitted value) lower than 0.284 showing a good agreement between the experimental and the predicted survival levels.