Determination of enzymatic activities of commercial pectinases for the clarification of apple juice

Different methods for testing Polygalacturonase (PG), pectinesterase (PE), and pectinlyase (PL) activities were applied to Rohapect DSS (RHD5) and Pectinol (PAI) commercial enzyme preparations in an apple pectin substrate. The viscometric method for PG activity determination was satisfactory, but foreign proteins could affect the spectrophotometric determination of PL activity in solutions of enzyme preparations. Although 50 degrees C was a well-defined breaking point where enzymes rapidly decrease their activity, rate and range of heat-inactivation were different depending on the activity assayed. While PG activity showed two periods of different thermolability, PL was monophasic and highly sensitive to heat. The pH dependence of the pectic enzyme activities was also studied over the 3-7 range. (C) 1998 Elsevier Science Ltd. All rights reserved.