1 Internal browning disorders during storage of ‘Rocha’ pear: effects of harvest maturity and CO 2 partial pressure T. Deuchande 1 , F. Fidalgo 2 , C. Larrigaudière 3 and D. P. F. Almeida 1,4 1 CBQF, Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Rua Dr. António Bernardino de Almeida 4200-072 Porto, Portugal 2 BioFIG – Center for Biodiversity, Functional and Integrative Genomics, Departamento de Biologia da Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal 3 UdL-IRTA, Postharvest Department, Av. Alcalde Rovira Roure 191, 25198 Lleida, Spain 4 Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal Keywords: Pyrus communis, CA-storage, carbon dioxide, oxygen, fermentative metabolism, physiological disorders. ABSTRACT The aim of this work was to study the development and biochemical basis of internal browning in ‘Rocha’ pear (Pyrus communis L. cv. Rocha) in relation to storage atmosphere and harvest maturity. Pears were harvested at an early, optimal, and late maturity stages and stored for 6 months at 0 o C + 3% O 2 + 0.5% CO 2 (normal CA storage) and up to 2 months at 0 o C + 1% O 2 + 10% CO 2 (browning inducing CA storage). Internal browning symptoms were classified into two categories: wet necrotic breakdown and dry cavities. After 4 months of storage under normal CA, fruit from the early and optimal harvests did not develop browning, while 25% of the late harvested fruits were affected with an index of ca. 0.1. After 2 months under high CO 2, internal browning disorders affected, on average, 90% of the fruit. Late harvested fruits had the highest browning incidence (98%) and index (0.72), while early-harvested fruit and fruit picked at optimal maturity had 90 and 92% incidence and indices of 0.46 and 0.67, respectively. Disorder incidence was positively correlated with increased levels of acetaldehyde and ethanol in late harvested fruits both at harvest and after 2 months of storage, but not with changes in H 2 O 2 -scavenging potential (CAT, APX and POX activities). Hence, we proposed to use the fermentative markers to predict the sensitivity of ‘Rocha’ pear to browning disorders. INTRODUCTION ‘Rocha’ pear is susceptible to internal browning disorders (IBD), a major cause of postharvest losses during long-term storage under controlled atmosphere (CA) (Veltman et al., 2000). The main factors affecting the incidence and severity of IBD during long term storage are: fruit maturity at harvest, imbalance between oxidative and reductive processes, fermentative metabolism, partial pressures of the gases used in CA storage and Deuchande, T., Fidalgo, F., Larrigaudière, C. and Almeida, D. P. F. 2012. Internal browning disorders during storage of ‘Rocha’ pear: effects of harvest maturity and CO 2 partial pressure. In: I. Recasens, J. Graell, G. Echeverría (editores), Avances en Poscosecha de frutas y hortalizas. Edicions de la Universitat de Lleida.