Refrigeration and Pre-Cooling of Citrus Fruits 
J. W. Andrews, Pre-cooling Engineer 
The subject of “Packing and Shipment 
of Citrus Fruits” is so broad and compli¬ 
cated that I have chosen to treat upon only 
one phase of its problems, viz: on the ap¬ 
plication of refrigeration and pre-cooling. 
The use of the physical state of “cool¬ 
ing” to assist in the keeping of perishables 
is of ancient origin. Since the develop¬ 
ment of modern ice making and refriger¬ 
ating machines, the subject has become of 
deep interest to those who grow and mar¬ 
ket perishables in the warmer climates. 
This development has caused, in recent 
years, the formation of a system of spe¬ 
cially designed “refrigerator” cars which 
are in increasing heavy demand for move¬ 
ment of the highly perishable commodi¬ 
ties. 
Any discussion of the value of refrig¬ 
eration for the movement of citrus fruits 
must necessarily be based upon some pre¬ 
determined data as to what point on the 
thermometer scale it is most desirable to 
reach. Cooling, in the first place, tends 
to keep fruits and vegetables fresh and 
to hold back the ripening process. It re¬ 
duces the rate of, but does not eliminate 
respiration of all vegetation and, in doing 
so, tends to keep within the commodity its 
water content. Aside from this desirable 
feature we have the equally important one 
with Florida Citrus Exchange, Tampa 
of retarding decay. Competent scientific 
investigators seem to have established that 
blue mold, an ever present fungus disease 
of our citrus fruits, develops quite slowly 
below 40 degrees F. while it becomes 
active at temperatures from 50 degrees 
upward. Stem end rot, whether due to 
Phomopsis citri or Diplodia, seems to be 
comparatively slow in its development at 
temperatures around 50 degrees and al¬ 
most dormant at 40 degrees. As these de¬ 
cays are responsible for most of Florida’s 
losses in distribution, refrigeration has, 
within the last few years, assumed a 
prominent place in our marketing scheme. 
The rate of cooling in a refrigerator car 
depends largely on the arrangement of ice 
bunkers and the nature of floor, together 
with the general arrangement of load. 
In the case of plain box bunker equipment 
without floor racks the air circulation is 
often so retarded that cars promptly 
moved to eastern markets can reach des¬ 
tination before a desirable “keeping” tem¬ 
perature is reached. If vertical air col¬ 
umns are maintained along the sides of 
car ice chambers and a false, slatted floor 
is provided, the general average temper¬ 
ature drop is materially hastened. As a 
rule, however, a Florida car moving in 
our fall or spring months is from 3^4 to 
5 days on its journey before the temper- 
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