24 MISC. PUBLICATION 168, U. S. DEPT. OF AGRICULTURE 



concerned, it can often be detected by tasting the injured flesh. 

 Fertilizers and lime are less easily detected in this way ; therefore, 

 when injury is found and either of these substances is suspected 

 of being the cause, diagnosis depends chiefly on whether the 

 substance can actually be found on the car floor and walls. Injury 

 comes about only where the fruit lies in contact with the chem- 

 ical, and it is usually more severe in the layer next to the floor 

 than in that next to the wall. It is due apparently to the forcing 

 of the fruit into or against the chemical by the weight of the 

 overlying load combined with the rubbing and bruising that result 

 from the constant jolting and shifting about of the load in the 

 moving car. 



INJURY BY HYDROCHLORIC ACID 



Injury to apples caused by hydrochloric acid used in washing 

 treatments appears typically as a bleaching of the skin. It usually 

 appears within a day or two after washing. At first the color 

 seems merely to fade into the flesh and the skin softens, but later 

 the skin may crack through the center of the spots and become 

 dry and papery. With age the spots become depressed, and some- 

 times the presence of dissolved arsenic in the acid washing solu- 

 tion causes them to turn black. The appearance and severity vary 

 somewhat with different varieties. Sometimes a few tiny black 

 freckles found at lenticels on stored fruit, especially Winesap 

 and Arkansas Black, may be the only indication of acid injury. 

 Such spots might easily be mistaken for Jonathan spot. 



Acid injury is sometimes localized in the stem or calyx region 

 or at points where the apple has remained in contact with other 

 objects; but usually the injured areas are scattered irregularly 

 over the apple, marking places where drops of acid washing 

 solution evaporated. Where drops of solution have concentrated 

 to an injurious strength through evaporation, the outline of the 

 affected area is usually circular (pi. 5, A) ; but where acid has 

 accumulated between an apple and some other object in contact 

 with it, the outline may be quite irregular. 



Acid injury can be prevented by careful attention to the instruc- 

 tions given in Technical Bulletin 245 (1+6) for the use of hydro- 

 chloric acid solutions for washing apples. Of special importance 

 in preventing acid injury is a thorough rinsing of the fruit after 

 it passes through the washing solution. 



(See U6, 136.) 



INJURY BY ALKALINE SOLVENTS 



Although hydrochloric acid is the solvent commonly used for 

 the removal of arsenical-spray residue, a number of alkaline 

 materials, including solutions or mixtures of sodium hydroxide, 

 sodium carbonate, trisodium phosphate, borax, sodium silicate, 

 and other substances, are also employed. These solvents are some- 

 times used at a temperature of 100° F. or higher. Arsenical injury 

 occurs somewhat more commonly on apples washed in alkaline 

 solvents than on those washed in hydrochloric acid. Because an 

 alkaline solvent is much more difficult to rinse off than the 

 hydrochloric acid solution, apples washed in the former often 



