Enzymatic hydrolysis of carrot for extraction of a cloud-stable juice

Abstract

The influence of various enzymes on the cell wall structure of carrots ( Daucus carrota) was examined and related to changes in the juice extracted from the pulp with respect to volume, solids content, pH and viscosity. Crude preparations of cellulase (EC 3.2.1.4), hemicellulase, pectinase (EC 3.2.1.15), pectinesterase (EC 3.1.1.11) and an industrial grade pectinase/cellulase preparation (Rohament PC), all exhibiting cellulolytic as well as pectinolytic action, were used either singly or in combinations. Polarizing microscopy revealed a gradual loss of birefringence from the cell walls indicating degradation of ordered structure by all of the enzymes. The time for loss of birefringence was significantly correlated with the pectinase activity but not with the cellulase activity, suggesting that the presence of pectic substances is important in maintaining the ordered structure of the cell wall in carrot. Alterations to cell wall structure by pectinase were confirmed by scanning electon microscopy. Hydrolytic activity against carrots as measured by the increase in yield of juice could be predicted from the pectinase and cellulase activities through a linear regression equation ( R = +0.72; P < 0.01) but the pectinolytic action was the most important factor. The yield of juice from the control carrot was 50.5% of the wet pulp mass with a total solids content of 7.9%, viscosity of 2.9 centistokes and a pH value of 5.65. Application of the enzyme preparations to the pulp (268–455 mg/kg) increased the volume of juice extracted, with the industrial grade preparation (440 mg/kg) yielding 50% more juice than the control for a 30-min incubation at 50 °C.