11.5.1 Ripening indicators
Several major changes can take place as fruits ripen. Not all occur in every type of fruit, but taken collectively they charac-terise ripening processes. They include:
1. a rise in respiration rate;
2. production of ethylene;
3. flesh softening;
4. appearance of colour;
5. formation of volatiles with associated development of flavour (Figure 11.12).
One prime objective of a postharvest physiologist is to ensure these changes occur immediately prior to fruit purchase or in the hands of a consumer. Sometimes all events take place at about the same time, denoting the time of optimal eating quality. However, the linkage is not a rigid one. Throughout ripening, respiration remains tightly coupled (Section 2.4) so that one consequence of increased respiration is an increase in available energy as ATP. Biological energy is used for many biosynthetic events, and more ATP is consumed during ripening to produce the many attractive characteristics of a ripe fruit.