THE EFFECT OF CALCIUM INFILTRATION ON STRUCTURAL-CHANGES IN CELL-WALLS OF STORED APPLES

Apples of cv. Golden Delicious were vacuum infiltrated with 300 mM man nitol, with or without 50 and 150 mM CaCl2. The fruits were stored und er low temperature of 2-4 degrees C for 100 d and sampled every 25 d f or flesh firmness and transmission electron microscopy. The infiltrati on of the fruits with 150 mM CaCl2 resulted in higher retention of fle sh firmness throughout the storage period, but with 50 mM CaCl2 this c ould be retained only up to 25 d. The content of insoluble calcium in the flesh increased with increase in the storage period. A large amoun t of the infiltrated calcium accumulated in walls. However, no relatio n could be observed between flesh firmness and the amounts of calcium associated with free, ionically bound and covalently bound pectin frac tions of the walls. The transmission electron micrographs revealed tha t most of the changes appeared to involve the middle lamella, and fles h firmness can be judged from the visual inspection of the micrographs . It appears that the effect of calcium in maintaining an intact middl e lamella may not be its direct ionic effect.