Factors Influencing the Volatile Oil Content of the Peel of Immature and Mature Oranges.

Introduction A study was made recently in this laboratory on some possible causes of breakdown in the peel of Washington Navel oranges. One approach to this problem was the determination and evaluation of the relative quantities of volatile oil in the peel of affected and unaffected fruits (2). It was founld early in this investigation that more information was needed than had been published on the factors influencing the oil content of orange peel. Experiments were planned, therefore, to determine the effect of age and size of fruit, and the effect of environment, on the relative amounts of oil in the peel of healthy Valencia and Washington Navel oranges. The results of these studies are reported in the present paper. They are considered to be important not only because of their bearing on the commercial production of citrus oils, but also because of the relation of the oil to certain discolorations and pittings of the peel when the oil is liberated from the glands by excessive turgidity or by fungus, insect, or mechanical wounds. HOOD (7), in Florida in 1916, and WILSON and YOUNG (13), in California in 1917, appear to have been the first and only ones in the United States to have made quantitative studies on the volatile oil in the peel of citrus fruits, except possibly on a commercial basis. Comparatively recently, deterluinations of the volatile oil in citrus peel have been made in other countries bv DE VILLIERS (5), TANCHICO and WEST (11), BRAVERMAN and MON'SELISE (4), SAMISCH (9), and FELIUI (6). The sizes of the samples and the methods used in the last three studies appear to warrant conclusions only as to general trends.Materials and methods