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Various additives have been reported to influence Ca absorption 

 from a CaClo dip, E.g . , certain "thickeners" have been reported to 

 greatly increase absorption, and wetting agents to reduce it. Fur- 

 ther, commercial adoption of the practice would likely incorporate 

 CaCl2 into a solution containing a scald inhibitor and fungicide. 

 The presence of thickeners, a strong wetting agent, a fungicide, a 

 scald inhibitor, and combinations of these materials in a 2% CaClo 

 dip neither aided nor hindered Ca uptake by 'Mcintosh' nor produced 

 any adverse effects on the apples. Thus, a CaCl^ dip can be suc- 

 cessfully combined with a wide range of other materials. It is 

 noteworthy that we have had no success in trying to increase Ca ab- 

 sorption through use of "thickeners," and cannot recommend their use. 



It must be recognized that uptake of Ca from residues is slow. 

 Relative humidity (R.H.) of the storage atmosphere is a factor that 

 can influence this uptake. Whether this influence is good or bad, 

 again would seem to depend on the specific conditions you are work- 

 ing with. It appears that a high R.H. (95-98'o) has a positive in- 

 fluence if it keeps the CaCl7 residue from drying out, so that the 

 apples can continue to absorb Ca for several months. On the other 

 hand, a low R.H. (85-901) may concentrate a weak solution (that is 

 make a 11 CaCl^ solution act like a 4% CaCl2 solution) and increase 

 the rate of Ca^'absorpt ion, but if the low rTh. causes the residue 

 to completely dry up, the absorption will cease. Thus, at a low 

 storage R.H., rapid penetration of Ca may occur, but only for a 

 short period of time. Since apples are normally stored for many 

 months, high R.H. is probably desirable, to maintain uptake over a 

 long period of time and thus obtain maximum benefit from dips. If 

 you maintain a high storage R.H., you can probably obtain consider- 

 able benefit from moderate CaCl2 concentrations in the dip solu- 

 tions and avoid the necessity for the very high (3^ or 4%) CaCl2 

 concentrations . 



Will postharvest CaCl2 dips improve the storageability of 

 Massachusetts apples? We conducted a small scale pilot study to 

 measure potential benefits to fruits from the CaCl2 dip treatments. 

 A 21 or 4% CaCl2 dip significantly increased the flesh Ca of 'Mcin- 

 tosh' and decreased their internal breakdown from 16% in the con- 

 trols to 2-3% in treated samples. Also, the fruit dipped in 4% 

 CaCl were significantly firmer than the controls after 3 months 

 storage. In 'Cortland', breakdown was seemingly reduced from 17% 

 in the controls to 6% in samples dipped in 4% CaCl2. These were 

 encouraging results, and there is another way to look at the re- 

 sults, too. In Massachusetts, a flesh Ca concentration of about 

 225 ppm appears to be optimum for quality retention during long- 

 term storage of apples. Fruits frequently possess Ca levels sub- 

 stantially lower than this at harvest, and therefore, have a high 

 potential for deterioration. Ca concentrations in 'Mcintosh' and 

 'Cortland' were increased more than 100 ppm by a 4% CaCl2 dip, and 

 50 ppm by a 2% dip, and in 'Baldwin' more than 60 ppm ana about 30 

 ppm by 41 and 2% dips, respectively. Dips therefore made the fruits 

 considerably more suitable for long-term storage. We believe that 



