Jurin and Karel (36) used the results of respiration studies to predict 
optimum packaging conditions in polyethylene. They found that the theoretical 
steady-state concentrations of carbon dioxide and oxygen in polyethylene bags 
were in good agreement with experimental results with McIntosh apples in tests 
at 20° C. (68° F.). Marcellin (45) found that physiological packaging in 
plastic films which maintain a beneficial microclimate for apples is possible. 
However, many factors are involved other than just the choice of film. 
Effect of Film on Cooling 
Film liners retard cooling, but the amount depends on the type of con- 
tainer in which liners are used (30, 33, 35, 69). Schomer, Gerhardt, and 
Sainsbury (69) measured the time required for removal of three-fourths of the 
field heat from Golden Delicious in different containers. Fifty-six hours were 
required to remove three-fourths of the field heat of tissue-wrapped fruit in a 
wood box. In a cell carton it took 77 hours, and in a cell carton with a poly- 
ethylene liner, 99 hours. However, they concluded that this interference in 
cooling by polyethylene was not serious. Workman (79) stated that some pre- 
cooling before packaging in film was desirable. 
A package having poor cooling characteristics, such as a corrugated 
carton, when stacked in a manner that allows little surface presentations to 
the airstream, will not cool much more slowly when lined than when unlined (30). 
On the other hand, liners will alter the cooling of packages that are normally 
open so convection currents can pass through the fruit. Golden Delicious apples 
in a pallet load of field boxes required 29 hours for three-fourths cooling 
with no polyethylene cover. With a film pallet cover over the boxes, 66 hours 
were required for three-fourths cooling (30). 
Dewey, Raphael, and Goff (9) found that it took 8 days for apples in the 
center of 18-bushel bulk boxes to cool to 36° F. in a 32° room. When these 
bulk boxes had a 4-mil polyethylene liner, it took 16 days for center fruit to 
reach 36° and the temperature stayed 1.5 to 3 degrees higher than in unlined bulk 
boxes. 
Storage Temperature 
Workman (79) stored several varieties at temperatures as high as 42° F. 
in sealed polyethylene liners without injury, However, he recommended keeping 
the storage temperature below 37° to avoid possible low oxygen or high carbon 
dioxide injury. Ryall and Uota (65) stored Yellow Newtown at 32°, 40°, and 45° 
in a 1.5-mil polyethylene. They found that carbon dioxide was maintained at 4 
to 5 percent and oxygen at 3.0 to 7.5 percent at each storage temperature. Al- 
though respiration was higher at the higher temperature, the film also was more 
permeable at higher storage temperatures. Best results with this variety were 
obtained at 40°. Marcellin (44) reported that the composition of the atmosphere 
inside film liners depends but little on the storage temperatures. Marcellin 
(40, 44, 46) and Bouhier (2) had good success in storing the Calville Blanc and 
Golden Delicious apples at temperatures of 45° and 59° in sealed polyethylene, 
with a saving in refrigeration. Leblond (39) packed Belle de Boskoop apples in 
small 1 kilogram (2.2 pounds) polyethylene bags and stored them successfully 
for 5 months at 7° C. (44.6° F.). At this temperature an atmosphere of 6 per- 
cent carbon dioxide and 2 to 4 percent oxygen was maintained, Johansson (35) 
enclosed 5 tons of apples in a 1l-mil polyethylene tent at 40°, and maintained a 
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