Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/1996
Publication Date: N/A
Interpretive Summary: One of the major thrusts of current postharvest research is to reduce the use of fungicides in controlling losses of fruit in storage. Previous research has shown that postharvest calcium treatment of apples can be beneficial in maintaining fruit quality. One of the major problems encountered is actually getting the calcium solution into the fruit tissue where it can have the desired effects of maintaining fruit firmness and reducing decay due to fungal pathogens. The results of this research indicated that pretreating apple fruit with selected surfactants immediately before postharvest calcium treatments increased the uptake of calcium solutions from postharvest treatments and resulted in higher fruit flesh calcium concentration. This information will enable apple growers to develop alternate strategies to maintain the quality of stored fruit and reduce their dependency on fungicides.
Technical Abstract: 'Golden Delicious' apples (Malus domestica Borkh) were pretreated by dipping in solutions of distilled water, surfactants including Brij 30, Tween 20, Tween 80, Tergitol 15-S-9, and Triton X-100, and a solvent, CH2Cl2, and then pressure infiltrated with a 2 percent solution of CaCl2. Following 4 months storage at 0C, the fruit were removed and analyzed for flesh calcium concentration, the fruit surface observed by low-temperature scanning electron microscopy and the fruit were also rated for fruit surface injury. Calcium concentration of the fruit flesh and the resulting firmness varied significantly with the surfactant pretreatment. Low-temperature scanning electron microscopy indicated that the amount of increase of the fruit flesh calcium concentration was directly related to the degree of disruption or alteration of the epicuticular wax. Brij 30 altered the epicuticular wax the least and had the lowest increase in flesh hcalcium concentration and the least firm fruit. Triton X-100 altered the epicuticular wax the most and had the highest fruit flesh calcium concentration and greatest firmness of any of the surfactant pretreated fruit. Methylene chloride actually removed some of the epicuticular wax and the fruit pretreated with this solvent had the highest flesh calcium concentration and greatest firmness resulting from any of the treatments. However, all of the fruit treated with this solvent were severely injured.