Physiological Studies of the Fruits of the Pineapple [ananas Comosus (l.) Merr.] with Special Reference to Physiological Breakdown.

Physiological breakdown of the fruits of the pineapple [Ananas comosus (L.) Merr.] is characterized by a darkening of the flesh of the fruitlets, beginning near their attachment to the core in a region an inch or two above the base of the fruit. The-disorder progresses upward and outward, subsequently involving all of the fruitlet except the ovary and a layer approximately one quarter inch deep below the skin. Only in advanced stages do the surface of the fruit and the core become involved. Hence in most fruits there may be no external symptoms of the disorder. Severe cases of physiological breakdown are frequently discovered in pineapples that appear normal and attractive from the exterior. The disorder is not a form of over-ripeness as is true of "internal breakdown" of apples. One of the commonest causes of physiological breakdown is exposure of the fruits to relatively low temperatures. The disorder has been observed in Florida in the fruits that were induced to ripen during the winter months by forcing the bloom with acetylene gas during "off season." Physiological breakdown has been reported to occur under similar conditions in Australia (3). Also pineapples harvested during the summer months may develop breakdown during storage or transit if holding temperatures are too low (5, 8), the greener fruits being more subject to the disorder than the riper fruits. Critical temperatures appear to be in the range of 00 to 50 C. Other conditions than low temperatures may initiate the mechanism causing physiological breakdown. The disorder has been observed in imported fruits that have not been subject to low temperatures during transit. Likewise a somewhat similar if not identical disorder may be induced by heavily waxing mature fruits or by holding them in air-tight containers. The investigations now being reported were undertaken for the purpose of learning more about the fundamental causes of physiological breakdown with the hope that information so obtained might lead to methods of prevention of this disorder. It was hoped too that the information might be useful in studying physiological disorders of other fruits and of vegetables in cold storage.