ENZYMATIC MACERATION OF APPLE PARENCHYMA TISSUE. I. MODELLING OF THE KINETICS OF HYDROLYSIS

Abstract

During the maceration of apple parenchyma with polygalacturonase (PG), three fractions were obtained (residual tissue, free cells or pulp, juice) in which the cell wall material was measured as alcohol-insoluble solids (AIS). A model is proposed to describe the distribution of cell wall material in these three fractions during the course of the enzymatic maceration process, which fitted the experimental data with a determination coefficient r² superior to 0.99. Two processes of maceration were shown to be involved. A first, fast process, degraded a small part of the tissue while the second process slowly degraded the remaining tissue. The maceration products were principally non degradable cells and non degradable soluble pectins. The degradable cells and the degradable pectins accumulated only at the beginning of the maceration. The rate constants followed the Arrhenius law. The initial rate of maceration increased with the amount of PG or the surface area to reach a limit value at high enzyme concentrations or high surface areas, respectively.

ACKNOWLEDGMENTS

The authors thank C. Renard for useful discussion and for correcting the English and the Comité des Fruits à Cidre for funding of C.E.M.