COLD STORAGE FOR APPLES AND PEARS 15 



conditions in the orchard and is not caused by storage conditions. 

 Affected fruit can be stored approximately as long as normal fruit, 

 but its market value may be greatly depreciated if cork spot is very 

 prevalent. 



CORE BREAK-DOWN 



Core break-down is characterized by an extremely soft watery con- 

 dition about the core, followed by rapid disintegration and discolora- 

 tion in the tissue of this region, sometimes leaving only a shell of the 

 outer tissue unaffected. It frequently occurs during the ripening 

 of fruit that has been left on the tree too long before harvesting and 

 also may occur in fruit that has been held too long in storage at low 

 temperatures. In Bartlett pears it is aggravated by ripening at too 

 high temperatures, in which case it is not confined to the core region. 



COLD-STORAGE PLANTS AND EQUIPMENT 

 Refrigeration 



The best way to become familiar with refrigeration is to work with 

 it and use it. Each cold-storage plant has characteristics of is own, 

 and to take advantage of its good points and to avoid difficulties that 

 may not be common to other plants one must be familiar with that par- 

 ticular plant, General principles of refrigeration apply to all plants, 

 however, and knowing these principles will enable an operator to profit 

 by his experience. They are covered in textbooks (12, IS, 16, %lf), 

 and more specific information is given in handbooks {2, 3, 23, 25) on 

 characteristics of refrigerants, condenser, compressor, and evaporator, 

 insulation values, fan and duct data, requirements of stored products, 

 cooling surface, power requirements, and other matters. 



PUMPING HEAT 



The process of refrigeration might be likened to pumping air out of 

 a tank until the pressure is lower than that of the atmosphere. Once 

 the desired low pressure inside the tank is reached, the only additional 

 pumping necessary is to remove any air that enters the tank by leakage, 

 and then the pumping needed will depend entirely upon the leakage. 

 In a refrigerated space, it is desirable to maintain a certain tempera- 

 ture below that of the surroundings. Heat is pumped out until the de- 

 sired low temperature is reached, whereupon further pumping is nec- 

 essary only to remove the heat that enters the chamber by leakage 

 through walls and open doors or heat that is generated within the space. 



When pumping air from a vacuum tank, if only a slight approach 

 to vacuum is required, less power and a smaller pump are needed than 

 for a high vacuum. The size of the pump required and the horsepower 

 of the motor depend upon two factors: (1) The quantity of air to be 

 removed and (2) the pressure inside the tank. If too much air is 

 allowed to enter the tank, the pump cannot remove it and the desired 

 vacuum cannot be maintained. Similarly in a refrigerating system, if 

 only a moderately low temperature is required, less power and a smaller 

 compressor are needed than where a very low temperature is desired. 

 Furthermore, if the refrigeration machinery does not have the capac- 



