Prediction of decoloration in paprika oleoresins. Application to studies of stability in thermodynamically compensated systems

In six paprika oleoresins, the kinetic parameters for the decoloration reac tion at three temperatures have been established. The thermodynamic study s hows that the decoloration reaction in each oleoresin has its own activatio n entropy (Delta S) and activation enthalpy (Delta H). The six reactions st udied show a constant ratio between Delta H and Delta S, which means that e ach reaction is an isokinetic form of only one reaction affected by thermod ynamic compensation. Instead of one equation per oleoresin to predict pigme nt concentration as a mathematical function of time and temperature, one un ique equation can be obtained in which Delta H is a function of Delta S. Th e validity of this equation has been tested by comparing the actual concent ration remaining during a heat treatment and the calculated one. More than 90% of the calculated concentrations are within the range of variability of the actual mean. Due to the reduction in the number of variables in thermo dynamic compensated systems, a general procedure to calculate the activatio n entropy in isokinetic reactions is proposed.