Involved in degradation of plant cell walls. Hydrolyzes the feruloyl-arabinose ester bond in arabinoxylans as well as the feruloyl-galactose and feruloyl-arabinose ester bonds in pectin. feruloyl-polysaccharide + H2O = ferulate + polysaccharide. Homodimer. The calcium ion seen in the crystal structure is located far from the active site and appears to have a role in stabilization of the lid domain. Belongs to the tannase family.