34 



PRECOOLING 



Car Precooling. 



For the precooling of produce after being loaded on the 

 cars, known as ''car precooling," rather heavy equipment 

 must be provided, because the volume of air circulated must 

 be at a maximum, while the temperature must be at a mini- 

 mum in order to accomplish the work quickly. It is difficult 

 under ordinary conditions to cool produce after it is packed, 

 especially where, as is the case in car loading, the packages 

 must be rather closely stacked. A considerable length of 

 time is required to cool the entire load satisfactorily. The 

 packages most exposed to the air blast and the outer layers 

 in the packages are naturally cooled first, but where the pro- 

 duct is tightly packed the interior of the packages is not 

 easily affected. In the Bureau work, differences of fifteen or 

 twenty degrees are frequently found between outer layers 

 and the interior of the same packages. It is necessary, 

 therefore, to continue the process long enough to reach the 

 interior or to cool the outer layers to a minimum temperature 

 and to depend upon equalization throughout the load to bring 

 the average temperature of the carload as a w^hole to a point 

 low enough to hold the produce in good condition. 



Work With Vegetables. 



I regret that it will be impossible to give records on pre- 

 cooling and shipments of vegetables, for the reason that this 

 work has only recently been started in Florida and the data 

 thus far obtained are insufficient as yet to enable definite 

 analyses and deductions to be made. So far, ten cars of let- 

 tuce have been precooled by the experimental portable plant 

 built by the Bureau of Plant Industry, and these cars were 

 shipped to northern markets. Each precooled car is accom- 

 panied by a check car non-precooled and all cars contain 

 marked crates of lettuce handled by the representatives of 

 the Bureau in Florida and ordinaiy commercial packages of 

 the same cutting. These crates are carefully inspected on 

 arrival by representatives of the Bureau; the hampers are 

 held several days under market conditions and further in- 

 spections are made to determine the market-holding quali- 



