The use of Mn to improve the darkening process of ripe olives was studied with Manzanilla, Hojiblanca, Carrasquena and Cacerena cultivars on both pilot and industrial scales during the "desalting" and storage steps. Results showed a general improvement of colour when Mn was used, although it was limited in the case of the Cacerena cv. Its addition to the storage brine for a period of at least 1 month yielded the best darkened olives and gave rise to low residues of Mn (around 10 mg/kg) in the final product, these conditions of processing being the most recommendable. This work has scaled up to use Mn during the oxidation process of ripe olives from pilot to industrial scale. (C) 2001 Elsevier Science Ltd. All rights reserved.