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11.5 - Fruit ripening

Several processes take place as fruit ripen and become edible, and then senesce. These changes may take place while fruit are still attached to the plant or after harvest. Tomato, banana and avocado are examples of fruit that at harvest can be at a mature green but unripe stage and are inedible until subsequent ripening processes have occurred. In contrast, strawberry, orange, boysenberry and grape are examples of fruit that need to stay on the tree or vine until ready to eat in order to have their desired eating characteristics.

Several major changes take place as fruits ripen, and taken collectively they characterise ripening processes. They include:

  1. Changes in carbohydrate composition, resulting in sugar accumulation and increased sweetness;
  2. Change in colour;
  3. Flesh softening and textural change;
  4. Formation of aroma volatiles;
  5. Accumulation of organic acids with associated development of flavour.

These changes make the ripe fruit attractive to animals, which in eating the fruit will disperse the seeds and enlarge the range and improve the survival chances of the next generation of the plant. Lignified pits and seeds encased in a fibrous core might be discarded after eating the flesh, whereas smaller seeds might pass through the animal’s digestive system and be deposited with the animal’s excrement.