Vapor Heat Sterilization of California Citrus and Avocado Fruits against Fruit-Fly Insects12

Publisher Website
Google Scholar
Abstract
Citrus and avocado fruits have been treated by moist heat according to the recommendations authorized by the U. S. Department of Agriculture, Bureau of Entomology and Plant Quarantine. These recommendations include two methods: (1) the vapor-heat "quick run-up" method to 120[degree] F; and, (2) the vapor-heat treatment which requires from 4 to 8 hours to get the fruit up to the required 110[degree] F temperature. The severity of injury to citrus fruits depends upon the environment in which the fruit is grown, the degree of maturity and the quality of the fruit. Only the highest quality citrus fruits can withstand the vapor heat treatments without injury. The avocado fruits tested in these experiments (the Fuerte and Dickinson varieties) could not tolerate the vapor heat treatments. The navel orange variety was severely injured by the vapor heat treatments, the degree of injury depending upon certain environmental conditions. The peel of the navel orange from some districts is too tender to withstand either the 110[degree] F or 120[degree] F temperature treatments. The storage life of navel oranges was significantly reduced by the heat treatments. Similar experiments on lemons show that the surface injury on the fruits was not quite as great as on the navel orange. The lemons did not store well and could not withstand the ordinary room temperatures on the packinghouse floor. The breakdown was so great that the fruit was not acceptable for processing for by-products. The Valencia orange appears to withstand the heat treatment much better than either navel oranges or lemons, however, Valencia oranges picked late in the season may be severely damaged when given the vapor-heat treatment. There is a slight off-flavor in the Valencia orange, but we do not get the marked surface damage to the peel which was obtained in the navel orange. Grapefruit can withstand the 110[degree] F treatment very well. Some injury to the peel occurs, but that is markedly influenced by the location in which the fruit is grown. As a generalization, grapefruit and Valencias can withstand the vapor-heat treatment much better than navel oranges and lemons. The soluble solids, the pH, the titratable acidity and the ascorbic acid have been determined on the juice of the different varieties of citrus fruits. As a result of the heat treatments, a marked reduction occurred in the titratable acidity and the ascorbic acid of navel and Valencia oranges, grapefruit and lemons. This decrease in free acidity of the treated fruit was accompanied by a corresponding increase in the pH of the juice. The vapor-heat treatments altered the taste of the citrus fruits and produced off-flavors which could be detected by the taste test. The heat treatments destroyed the fresh delicate flavor of the navel orange, and the loss of flavor and the reduction in acidity of the fruit gave the treated navels a flat taste.

This publication has 0 references indexed in Scilit: