Enzymatic maceration of apple parenchyma tissue. I. Modelling of the kinetics of hydrolysis

During the maceration of apple parenchyma with polygalacturonase (PG), thre e fractions were obtained (residual tissue, free cells or pulp, juice) in w hich the cell wall material was measured as alcohol-insoluble solids (AIS) A model is proposed to describe the distribution of cell wall material in t hese three fractions during the course of the enzymatic maceration process, which fitted the experimental data with a determination coefficient r(2) s uperior to 0.99. Two processes of maceration were shown to be involved. A f irst, fast process, degraded a small part of the tissue while the second pr ocess slowly degraded the remaining tissue. The maceration products were pr incipally non degradable cells and non degradable soluble pectins. The degr adable cells and the degradable pectins accumulated only at the beginning o f the maceration. The rate constants followed the Arrhenius law. The initia l 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, r espectively.