Acetic and propionic acids, inducers of ripening in pre-climacteric golden delicious apples

Abstract When treated with acetic or propionic acid vapours, intact pre-climacteric Golden Delicious apples started ripening prematurely. Experiments with [2− 14 C]propionic acid showed that a small part of the added acid is transformed into [ 14 C]ethylene, and that ripening probably begins in these circumstances as a result of the artificial increase in the endogenous ethylene level. It may be that in unripe apples the small amount of evolved ethylene is mostly derived from simple organic acids, so that the moment at which its triggering concentration is reached depends on the available supply of acids. As this, in turn, is a function of the state of maturity of the fruit, there must be a direct relationship between the start of ripening and the degree of maturity. Thus, even in very unripe apples, catabolic processes are at work or potentially present because of the modified β–oxidation of [1− 14 C]propionic acid observed.