Chemical changes during myrtle (Myrtus communis L.) fruit development and ripening

The chemical composition of fruit belonging to 'Barbara' and 'Daniela' myrtle cultivars was monitored during development from fruit-set to an over-ripe stage (July-January), with the aim to identify a reliable maturity index. Acidity, pH, reducing and total sugars, phenols, tannins, anthocyans, carbon dioxide and ethylene production rates were monitored over two different year seasons. Titratable acidity decreased during maturation, with significant differences due to cultivar and year of observation. Reducing sugars increased in both cultivars approximately sevenfold from fruit set to complete maturation. Total sugar content increased similarly ranging from 1.43% and 1.41% at fruit set to 8.28% and 7.56% at maturation for 'Barbara and 'Daniela', respectively. Total phenols and tannins occurred at high levels after fruit set and declined during development. Anthocyans levels increased, in both cultivars, according to a sigmoid curve. The pattern of respiration rate showed a gradual decline in both cultivars ranging from 365.81 and 396.42 mg kg(-1) h(-1) to 79.98 and 52.27 mg kg(-1) h(-1), respectively for 'Barbara' and 'Daniela' in 2006. A peak of variable size was observed in October-November period. Small increases in ethylene production have been detected during fruit development ranging from 130.57 and 269.14 mu L kg(-1) h(-1) measured at the onset of development to 13.04 and 19.36 mu L kg(-1) h(-1) measured at harvest for 'Barbara' and 'Daniela', respectively. (C) 2010 Elsevier B.V. All rights reserved.