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In use of postharvest CaCl2 drenches, it is important to 

 understand that little or no Ca enters the fruit during the 

 drenching process. The purpose of the drench is to leave a resi- 

 due of CaCl2 on the fruit. Ca is slowly absorbed by the apple 

 from the residue during storage. Therefore, the drench is never 

 followed by a rinse, which would remove the residue. Further- 

 more, for Ca to be absorbed from the residue, the residue must 

 not dry out. The apples should not be allowed to air-dry before 

 storage. If the storage is operating at the desired relative 

 humidity (90-95%), the residue should not dry out. However, if 

 the storage is operated at less than 90% relative humidity the 

 residue may dry out and no Ca uptake will occur as a result of 

 the drench treatment. 



We have encountered no difficulty from this residue when 

 apples are removed from storage. It will be removed if apples 

 are water-dumped, but even with hand-packed fruit no difficulty 

 has been reported. 



CaCl2 drenches can cause fruit injury, which occurs as tiny 

 black spots on the surface of the fruit. Generally, these spots 

 are concentrated in the calyx cup of the apple and are not objec- 

 tionable, although under some circumstances they may coalesce 

 into more unsightly blotches or may occur at the lenticels on the 

 cheeks. Do not exceed the recommended CaCl2 concentration, as 

 risk of this injury escalates rapidly at higher concentrations. 



CaCl2 is also corrosive, so equipment should be thoroughly 

 cleaned at completion of treatment. However, with appropriate 

 rinsing corrosion should not be a concern. 



The purpose of the postharvest application of CaCl2 is to 

 reduce the risk of breakdown, rot, and scald during but especial- 

 ly after storage. The recommended treatment will not make fruit 

 firmer, but will improve their ability to hold up during market- 

 ing. Treatments will be of greatest benefit to mature fruit des- 

 tined for long-term storage. Overripe fruit cannot be expected 

 to benefit significantly from a CaCl2 treatment. 



