BEHAVIOR OF PECTIC SUBSTANCES AND NARINGIN IN GRAPEFRUIT IN THE FIELD AND IN STORAGE

The physiological breakdown of citrus fruits variously known as storage spot, pitting, or pox has presented a perplexing problem to growers and shippers ever since the storage and transportation of these fruits was undertaken on an extensive scale. This breakdown manifests itself in various forms of blemishes of the rind, depending on such factors as the inherent condition of the fruit, the temperature at which the fruit is held, the length of storage, and the composition of the atmosphere surrounding the fruit. The disease is associated with exposure to excessively low temperatures, but its development is conditioned by the other factors mentioned. Partial control of this disorder has been attained in commerce by raising the temperature at which the fruit is held during transit and storage, the temperature depending on the kind of fruit in question. California oranges hold well at 380 F., but California-grown lemons and grapefruit require a temperature of 500 to 550, and recommendations of temperatures as high as 650 -have been made for commercial grapefruit storage. Other factors enter into the consideration of the best holding temperature; e.g., grapefruit will develop a deeper yellow or bronze at a temperature of 550 than at 650. This deep yellow color is considered undesirable by the trade because of the appearance but has no ill effect on the quality of the fruit. On the other hand, fruit held at 65° will be more subject to attacks by the various organisms of decay. High relative humidities are necessary at these higher temperatures in order to reduce shrinkage, but also afford favorable conditions for the development of these organisms. It has been shown previously (6) that losses from pitting in grapefruit can be reduced by choosing the proper season for picking fruit which is to be held or which is to be shipped great distances under refrigeration. Additional evidence on the influence of season on the susceptibility of grapefruit to pitting will be submitted in this paper. The nature of the changes occurring in the fruit during its development on the tree which tend to-increase or decrease its susceptibility to pitting if subjected to the unfavorable environment of low storage temperatures is not known. Evidence has been presented previously (6) and additional evidence is presented in this paper indicating that the temperature in the grove during the period immediately preceding picking has a bearing on the susceptibility the fruit will have to