Post-harvest Ripening of Avocados

Abstract

IT is a common observation that fruits of many species ripen quickly if they are harvested but more slowly or not at all if left on the tree. An extreme case of this behaviour is that of the Fuerte avocado (grown in southern California) which will not soften while attached to the tree by a healthy stem¹. Similarly, Florida avocados (var. Choquette and others) are stimulated to ripen when they are detached, but they differ from the California fruit in that most varieties eventually will successfully ripen on the tree. Recently, several objections¹ to the theory that ethylene plays an important part in fruit ripening have been eliminated, and it has been established that an active concentration of the ripening hormone accumulates within cantaloupes², bananas, mangoes and probably many other fruits³ before or coincident with the climacteric rise. From the work of Biale⁴ it is known that Fuerte avocados are stimulated to ripen by as little as 0.1 p.p.m. ethylene, and this same minimum concentration of gas is effective with most other fruits and plant tissues which have been investigated⁵. Therefore, a very small change in ethylene content induced after separation of the fruit from the tree could lead to an acceleration in ripening, and this possibility is investigated in the present communication.