Aryl-alcohol oxidases (EC 1.1.3.7) are enzymes that catalyse the oxidation of primary alcohols bearing aromatic rings, forming aromatic aldehydes and hydrogen peroxide. Their products include flavour-relevant aldehydes such as benzaldehyde, the character compound of almond aroma, linking these enzymes to flavour chemistry. In nature, white-rot fungi deploy aryl-alcohol oxidases during lignin degradation, where the peroxide generated feeds further oxidative attack on wood polymers. Biotechnologists are interested in them as selective, environmentally gentle catalysts for the green synthesis of aromatic aldehydes used in flavourings and fragrances. Like all oxidases, their activity depends on oxygen availability, pH, and temperature, factors that process designers must control.