Enzymes that cleave internal 1,3-β-linked bonds within xylan chains, the hemicelluloses of plant cell walls. In baking they act on dough arabinoxylans to improve crumb structure and loaf volume; in brewing and juice processing they reduce viscosity and aid clarification. They work synergistically with cellulases and arabinofuranosidases to dismantle plant cell walls completely, a cooperation exploited in biomass conversion as well as food processing. Dosage must be tuned: excessive xylanase degrades dough structure and produces sticky crumb, while the right level improves machinability and volume.