Energy metabolism and membrane lipid alterations in relation to brown heart development in 'Conference' pears during delayed controlled atmosphere storage

Research was carried out to test the effectiveness of delayed controlled atmosphere (CA) storage (21 days at 0degreesC in air before CA storage) on the occurrence of browning disorders and related physiological changes such as energy status and fatty acid metabolism in 'Conference' pears during long-term CA storage. After delayed CA, fruit were stored for up to 6 months in 3% CO2 + 1% O-2 at 0 degreesC. Fruit stored without delay had a high incidence of flesh and core browning and cavities, whereas delayed CA-fruit had only a very low incidence of flesh browning and no incidence of core browning and cavities. No significant losses of flesh firmness, acidity, skin colour and soluble solids contents between treatments were detected. Fruit subjected to delayed CA had higher ethylene production and respiration activity during the first 2 months of storage and higher ATP concentrations in the fruit tissue. A higher adenylate energy charge was maintained during storage, indicating a higher energy status in delayed CA-fruit. Delayed CA-fruit showed higher contents of total and free fatty acids and polar lipids than fruit stored in CA without delay. The results suggest that by delaying CA storage conditions, 'Conference' pears can become adapted to CA during the early stages of the storage period, making them more resistant to browning disorders. Reasons for this may be found in the energy status of fruit and integrity of membranes which may play an important role in this adaptation process. (C) 2003 Elsevier B.V. All rights reserved.