We have dipped several varieties of apples in various concen- 

 trations of CaCl2 from 0.5°^ (4 lbs/100 gal) to 41 (32 lbs/100 gal). 

 We found that little Ca was absorbed during the actual dip and that 

 uptake was mainly during storage from residues left on the apple. 

 Thus, the length of time apples actually spent in the dip was not 

 important, whether it was as short as a few seconds or as long as 

 60 minutes. Also, the solution temperature, whether cold or hot, 

 did not in itself affect Ca uptake. However, we observed that put- 

 ting warm apples into a cold solution may increase the uptake and 

 will of course have the added benefit of helping to cool the fruit. 

 Apparently, the cooling apple forms a partial vacuum that draws some 

 Ca solution into the fruit from the dip solution. 



The factor most influencing the uptake of Ca is the concentra- 

 tion of CaCl2 in the solution. The optimum CaCl^ concentration for 

 the dip is not yet clear. Low concentration (O.S and 1.01) of 

 CaCl-, were insufficient to substantially increase the Ca level of 

 apples. The effects of a 2% solution were variable; 1% signifi- 

 cantly increased the Ca in 'Mcintosh' stored for 3 months, but did 

 not significantly increase 'Cortland' or 'Baldwin' flesh Ca. This 

 does not mean that at \% and 1% concentrations the Ca is not pene- 

 trating the fruit; tests with radioactive Ca demonstrated that a 

 1% solution did penetrate into the flesh. However, individual fruits 

 vary greatly in their native Ca concentration as well as in their 

 ability to absorb Ca, so that the effect of the 2% CaCl^ was not 

 great enough to significantly overcome these variations^within our 

 relatively small sample sizes. Whether or not 1% CaCl2 is a high 

 enough concentration to substantially raise the Ca level in the 

 fruit during storage probably depends on the conditions of the fruit 

 and the storage. Furthermore, the most suitable CaClT concentration 

 probably varies with the variety being treated and the growing con- 

 ditions. We found that ^% CaCl2 significantly increased flesh Ca 

 in all varieties tested; this very concentrated solution (32 lbs of 

 CaCl2/100 gal) can probably be counted upon to raise the Ca level 

 in apples under most conditions that might be encountered, but it 

 is also probably more concentrated that necessary under many condi- 

 tions and may lead to problems, as will be mentioned later. 



How does Ca enter the apple, since absorption is almost entirely 

 from residue? We tested this question using radioactive Ca "tracers" 

 and found that absorption appears to be almost exclusively through 

 natural openings in the fruit, but at a very slow rate. Therefore, 

 the more openings available (open lenticels, open calyx, punctures, 

 etc.) the more readily Ca will penetrate. However, different vari- 

 eties and individual fruits within a variety varied greatly in open- 

 ness. Submerging cold apples in warm water and observing air bub- 

 ble formation may be a quick test to determine these fruit openings 

 and thus get an indication of how readily they will respond to post- 

 harvest dips; if many bubbles appear quickly, perhaps reduced CaCl2 

 concentrations may be used. 



