PRECOOLING 



35 



ties of the produce. In this way accurate figures of precool- 

 ed and non-precooled shipments are being obtained. 



In addition, a comparison of the effect of different handling 

 methods in the field are likewise being made. In general, it 

 may be said that the precooling of lettuce has been followed 

 by marked beneficial results. The lettuce arrives in the mar- 

 ket in crisper condition and with less decay or deterioration 

 than the same stock shipped without precooling. When the 

 precooling is accompanied by methods of handling in the 

 field through which a large part of the source of disease in- 

 fection may be removed, the results are tenfold greater than 

 by the utilization of precooling alone. This result amply 

 confirms the work done with fruits, and from this we may 

 confidently expect that the general principles underlying the 

 precooling and handling of vegetables will be found essen- 

 tially the same as those worked out for fruits. 



The proper system of precooling applicable to the handling 

 of vegetables has not as yet been determined. Under the 

 ordinary conditions of producing and marketing truck crops 

 at present, the utilization of the warehouse system, in which 

 the packages are cooled before they are loaded in the cars, 

 is perhaps impracticable, although under this system more 

 thorough and uniform work can be accomplished. It is only 

 where associations of growers or shipping companies are 

 sufficiently large to enable them to erect precooling plants, 

 or where packing-house or loading-shed facilities are suffi- 

 ciently ample to justify the erection of precooling plants that 

 the warehouse system can be successfully used. Such condi- 

 tions exist only in a comparatively few districts. The use 

 of the car cooling system therefore is apparently of the 

 greatest importance to the vegetable industry at present. 



Figures on the rate of cooling of lettuce are not yet avail- 

 able, but the work done shows that the time necessary to 

 accomplish satisfactory results is longer than was at first 

 expected. 



We have been surprised at the difficulty with which ham- 

 pers of lettuce can be cooled. The hampers are tightly pack- 

 ed, and the cooling of the interior of the package is dependent 

 upon the conductivity of the heat from the interior to the 



