USING SCANNING ELECTRON MICROSCOPY FOR QUALITY EVALUATION OF APPLES AFTER COLD STORAGE

Changes in the cuticle, epidermis and pulp of apple fruits were studied after cold storage using scanning electron microscopy (SEM). Also the firmness of the pulp, soluble solids content and juice pH were quantified. The study did use of 3 different apple cultivars ('Golden Delicious', 'Oregon Spur' and 'Bravo de Esmolfe') subjected to different pre-storage treatments (hot water treatments and calcium chloride solutions). The main objectives concern to: the identification of structural differences among varieties; some explanations for individual behaviour along the storage period; and the relationship between pre-storage treatments and structure and quality evolution of the fruits along the storage period. The thickness of cuticle and its waxes is quite different (less in 'Bravo de Esmolfe' apples). The extension of cracks in cuticle wax is higher with long term storage than at the initial phase of the storage in untreated fruits. Heat treatments and calcium application contribute to quality preservation of apples, particularly reducing the acidity loss. SEM will be a very interesting tool to complement quality studies and to accompany the fruit behaviour during its life time.