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Title: CHEMICAL CHANGES IN THE CORTICAL TISSUE AND CELL WALLS OF CALCIUM- INFILTRATED 'GOLDEN DELICIOUS' APPLES DURING STORAGE

Author
item CHARDONNET, CATHERINE - UNIVERSITY OF TENNESSEE
item CHARRON, CRAIG - UNIVERSITY OF TENNESSEE
item SAMS, CARL - UNIVERSITY OF TENNESSEE
item Conway, William

Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2002
Publication Date: 1/1/2003
Citation: Chardonnet, C.O., Charron, C.S., Sams, C.E., Conway, W.S. 2002. Chemical changes in the cortical tissue and cell walls of calcium- infiltrated 'golden delicious' apples during storage. Postharvest Biology and Technology 28 (2003) 97-111

Interpretive Summary: Chemicals which are currently being used successfully to maintain quality and reduce decay of stored apple fruit are becoming unavailable because of their association with human maladies. Therefore, the development of alternate methods for maintaining fruit quality in storage is now of the utmost importance. Calcium is the mineral element most closely associated with maintaining quality in apples. Previous research has shown that postharvest calcium treatment maintains fruit firmness and reduces decay due to postharvest fungal pathogens. However, the optimal concentration of calcium chloride to apply to various apples varieties is unclear. The results of this study indicate that the optimal calcium chloride concentration to increase total and cell wall bound calcium in 'Golden Delicious' fruit is a 2 percent solution. This information provides a guide for the apple industry to maintain fruit quality in storage while reducing their dependence on postharvest use of synthetic chemicals.

Technical Abstract: 'Golden Delicious' apples were untreated or pressure-infiltrated with 0, 1, 2, 3 or 4% calcium chloride solutions and stored at 0 degrees C for up to 6 months. The chemical composition of fruit tissue and cell walls of the layer under the epidermis was studied. Tissue infiltrated with 0% calcium chloride showed greater total K, P, Na, Mg and S compared to untreated controls and contents decreased during storage for both controls. Cell wall-bound Mg content in the water-infiltrated fruit was greater than that of untreated walls. The infiltration process also resulted in a decrease in neutral sugar content of the walls, mainly due to a loss of glucose, arabinose, galactose and xylose during storage. Analyses of the Ca-infiltrated tissue and cell walls during storage showed an interaction between calcium chloride treatment and time in storage. Calcium chloride infiltration resulted in an increase in total and cell wall-bound calcium of the apple during storage, with an optimum reached at 2% calcium chloride. Total K and Mg of Ca-treated fruit increased during storage, while P, Na, and S decreased. Cell wall-bound content of S and P of Ca-infiltrated fruit decreased with calcium chloride during storage while Na and Mg increased. Cell wall protein and neutral sugars decreased with calcium chloride during storage, mainly due to a decrease in glucose, arabinose and galactose. Sucrose increased in tissue infiltrated with calcium chloride and decreased during storage. Calcium chloride resulted in changes in wall composition and limited net wall content loss during storage. The major changes in tissue and cell walls of untreated fruit, probably resulted in fruit with a higher susceptibility to fungal diseases and lower quality.