EFFECT OF CULTIVAR AND RIPENING STAGE ON QUALITY AND MICROSTRUCTURE OF FROZEN MANGOES (MANGIFERA INDICA LINN.)

The aim of this work was to investigate the quality and microstructure of different frozen mango cultivars. Since freezing can cause severe textural damage to fruit, the proper selection of a ripening stage and cultivar can reduce such damage. Two mango cultivars (Nam Dok Mai and Chok Anan) were allowed to ripen for four ripening stages. During ripening, titratable acidity, alcohol-insoluble residues, and firmness significantly decreased while total soluble solids, total pectin, and water-soluble pectin levels increased. Mangoes from the three final ripening stages were frozen until the temperature of the samples reached -25 degrees C. After thawing, the partially ripe mango samples exhibited the highest firmness, lowest drip loss, lowest water-soluble pectin, and the highest sensory firmness scores. The microstructure found using light microscopy and transmission electron microscopy showed that all frozen-thawed mangoes exhibited a swelling and folding of the cell wall due to freezing damage. The cell walls of fully ripe mangoes were dramatically damaged, which explained the low firmness values. Tissue and cell wall damage in Nam Dok Mai were the greatest, which contributed to the large drip loss. The cheaper Chok Anan cultivar was more resistant to freezing damage than Nam Dok Mai.