The effects of organosilicone and more conventional hydrocarbon surfactants on postharvest radiolabeled calcium (Ca) and on Ca solution infiltration into `Golden Delicious' apples were examined to provide a direct and more efficient pressure infiltration technique to increase fruit Ca concentration. Both radiolabeled Ca infiltration and the proportional increase in fruit Ca estimated by fruit weight gain from Ca solutions of known concentration were significantly enhanced by a range of surfactants having differing chemical structures. Two organosilicone surfactants, Silwet L-77 and Silwet L-7604, known for their greater capacity to lower the surface tension of solutions than conventional hydrocarbon surfactants, were the best among the surfactants tested at augmenting Ca infiltration. Applications of surfactants to fruit were as effective or more effective when used as a pretreatment rather than by mixing with Ca solutions. The applied atmospheric pressure necessary to infiltrate Ca to levels considered sufficient to maintain fruit firmness and resist decay during storage could be lowered in fruit treated with organosilicone surfactants. Postharvest surfactant and Ca treatments may offer a practical means of increasing the Ca concentration of apple fruit.
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