Changes in flavour, cell wall degrading enzymes and ultrastructure of guava (Psidium guajava L.) during ripening
2005
Tóth-Markus, M. | Siddiqui, S. | Kovács, E. | Róth, E. | Németh-Szerdahelyi, E.
Volatile flavour substances were isolated from the minced pulp of half ripe and full ripe fruits of guava (Psidium guajava L.) cv. Lucknow-49 by simultaneous steam distillation extraction (SDE) with diethyl ether as extracting solvent. The concentrate was analysed by GC-MS. Acetic, butyric and hexanoic acids were the predominant acids, trans-2-hexenal and hexanal the predominant aldehydes and ethyl propanoate, methyl butyrate, ethyl butyrate, methyl hexanoate, ethyl hexanoate, cis-3-hexen-1-yl acetate, hexyl acetate, methyl benzoate, methyl octanoate, ethyl benzoate, phenylpropyl acetate and cinnamyl acetate, the esters responsible for the characteristic guava flavour were also present. The amount of total volatile substances was about 20% higher in full ripe fruits. The concentration of acids and most esters increased and that of C6 aldehydes decreased during ripening. The enzyme analysis showed that the polygalacturonase (PG) activity was lower in the ripe fruit, than in the half ripe one, while the β -galactosidase activity was not influenced by maturity stage. The surface and the cell walls of full ripe guava became wrinkled, and parenchyma cells were empty (SEM).
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