[Kinetics of furfural formation as related to heating, concentration and storage of orange juices and concentrates].

According to studies on an orange concentrate diluted back with distilled water to the desired extract content, the formation of furfural follows the pattern of a consequent reaction. After the induction period, the reaction curve takes a linear course cooresponding to a reaction of a zero order. The temperature dependence of the resultant reaction constant k obeys the ARRHENIUS equation and yields the same energy of activation for all the extract contents under investigation. This is a case of specific acid catalysis, because the reaction velocity is directly proportional to the hydronium ion activity. On a semilogarithmic scale, the dependence of the k values of the extract contents of the concentrates and of the re-constituted juice can be presented for various temperatures in the form of parallels. According to the literature, the amount of the furfural produced correlates with the quality of the orange juices and concentrates. Consequently, this amount might be used as an indicator in evaluating quality deteriorations due to unsuitable manufacturing and storage on the one hand, and for the computation and optimization of the manufacturing processes and parameters on the other hand.