48 HARVESTING, STORING, AND MARKETING 



than $100 have proved satisfactory. One of the best of these 

 consists of a tank equipped with paddles which both propel the 

 fruit and immerse it slightly. This device is not satisfactory 

 for pears since most varieties sink to the bottom of the tank. 

 A better device for pears is a belt conveyor which carries the 

 fruit along, partly immersed in the solution. 



It has been possible to remove as high as 90 per cent of 

 residue under commercial conditions. 



Efficiency of the treatment is increased by increasing the 

 strength of the acid, increasing the time of exposure, and 

 especially by raising the temperature of the solution. Varie- 

 ties with oily skins are most difficult to clean. Best results are 

 secured by treating soon after picking. 



Residues of lime, copper, lead, etc., are removed at the 

 same time. Very slight detrimental effects on appearance or 

 keeping quality have occurred on sound fruit when the op- 

 eration is properly performed. Some varieties have calyx 

 tubes extending well down to the core of the apple. In the 

 machines submerging the fruit, it has not been possible to 

 remove the cleaning solution from these tubes, and some dam- 

 age to the tissues, sometimes followed by decay, has resulted. 



Careless cleaning methods may result in arsenical injury 

 at calyx or stem, or hydrochloric acid burning, or chemical 

 injury at the core. Any of these injuries may result in storage 

 rots. All decayed fruit should be kept out of the cleaning 

 equipment. 



The commercial grade of acid testing 20 degrees Baume is 

 satisfactory, 3 gallons in 100 gallons of water making approxi- 

 mately a 1 percent solution, by weight. Solutions containing 

 about % of 1 percent are commonly used except in aggravated 

 cases. The strength of the acid bath should be maintained by 

 additions of acid from time to time. Clean the acid tank com- 

 pletely each day to prevent the accumulation of soluble 

 arsenic. 



Rinsing is very important in preventing injury to the keep- 

 ing quality of the fruit. Two to 3 gallons of fresh water 



