Commercial pectinases used in apple juice manufacturing contain a mixture of pectin-degrading enzyme activities. Nevertheless, fragments of branched pectic molecules (or pectic hairy regions) are resistant to degradation, and can cause membrane fouling in the final ultrafiltration step of concentrated apple juice. The pectic hairy regions contain both rhamno- and xylogalacturonan. Whereas rhamnogalacturonan-degrading enzymes were already identified, no enzyme was known for a fast degradation of xylogalacturonan. Apparently, these enzymes are very minor components of technical pectinases. Since Aspergillus strains are able to completely degrade pectin, including xylogalacturonan, we decided to use expression cloning to obtain xylogalacturonan-degrading enzymes.