22 



PRECOOLING 



In the citrus work of the Office of Horticulture and Pomol- 

 ogy and in the vegetable work, we found that there was a 

 great deal of difficulty in handling fruits and vegetables, even 

 under our modern system of transportation under refrigera- 

 tion in so-called refrigerator cars. The difficulty is this, that 

 a product is harvested oftentimes when the outside tempera- 

 ture is comparatively high. The product is packed often- 

 times in comparatively close packages. These packages, 

 with the latent heat, are loaded into the cars; and it is sup- 

 posed that the ice in the bunkers of the cars will not only 

 counteract the latent heat which is in these packages, but will 

 reduce the temperature to a point below which the organisms 

 which cause decay, bacteria and fungi, will not work. Suc- 

 cess in the transportation of any perishable product of this 

 character depends upon reducing its temperature to a point 

 below which these organisms of decomposition cannot act. 

 If the time for reducing the temperature is long, the pro- 

 cesses of ripening go on rapidly and the organisms multiply 

 to an extent that they cause very considerable loss in transit, 

 loss from decay. The problem of precooling, then, is the 

 problem of reducing the temperature of the product to a 

 point of safety before it goes into the car which is to carry it 

 on its journey to the market. You can readily see that when 

 a warm product goes into a cool car, it will be a considerable 

 period of time before the center of the package is reduced 

 to the same temperature as the fruits or products on the out- 

 side layers of the package, and with perishable stuff like 

 celery and lettuce, we get decay in the center of the package. 



The Package Question. 



You are familiar with the packages which are used to ship 

 lettuce from the southern regions, the barrel-high hampers, 

 which are packed very tightly. The leaves of the heads are 

 rolled tight, and then the heads are forced into the packages. 

 When you have as many as a dozen heads on a layer, it is 

 not a difficult matter to reduce the temperature of the out- 

 side heads, but it is difficult to reduce the temperature of 

 the inside heads. So if a basket of warm lettuce is put into 

 a refrigerator, it is a considerable time before the inside heads 

 become cool enough to prevent molds and rots starting. 



