Tape 3.—Average percentage concentration of carbon dioxide and 
owygen in the atmosphere when Bartlett pears were held in various 
sealed films 
Gas concentration in sealed films 
Film o1° F.! 65°—70° F.2 
CO, | O, | CO; O, 
Pliofilm— Percent | Percent Percent Percent 
TS Se Secret ek Oia a ee 3.5 | 1710 10. 0 i bees 
SOQ: Mila a Soe 1.0 16. 0 3. 0 a5 
1OORE Mil 2 ao eee eee ZO 13. G 6. 0 2.0 
Cellophane— 
2002S Asha oe are ee 3. 0 =O 13. 0 3. 0 
Polyethylene— 
Ce ee epi iy eee eee 2.5 14. 0 6. 0 | 2a 
ES tees ce See ne aoe 3. 0 17. 0 6. 0 | sees 
1 During 107 to 160 days of storage. 
2 After 5 days of ripening. 
The data are average concentrations obtained from many individual 
boxes during 3 years of study. The diffusion rate of oxygen and 
carbon dioxide through all films was sufficiently great at 31° F. to 
prevent the harmful accumulation of carbon dioxide or the depletion 
of oxygen. Carbon dioxide accumulated to concentrations of 1 to 3.5 
percent and oxygen was lowered to a range of 13 to 17 percent. These 
concentrations were attained soon after packaging and remained rel- 
atively constant as long as the pears were held at 31°. 
The respiration of a fruit is a good index of its rate of metabolism. 
Measurements of this kind were made on Bartlett pears wrapped in 
oiled paper and sealed in various plastic films. These data are given 
in figure 5; they show that at 31° F. pears in the sealed films respired 
at a slower rate than comparable fruit in oiled paper wraps in the 
standard pack. In other words, the sealed film depressed the general 
rate of metabolism of the fruit and thereby contributed to a length- 
ened storage life. The polyethylene film was more efficient in this 
respect than was the Plofilm. 
Stem shrivel was reduced and the fresh appearance and green color 
of Bartlett pears in cold storage were markedly preserved by packing 
the fruit in any of the sealed films shown in table 2. Fruit in oiled 
wraps when packed in the standard manner usually developed con- 
siderable yellow ground color and visible shrivelling in the stem 
region after prolonged cold storage. Differences in ground color of 
pears due to packaging methods are shown in figure 6. The preserva- 
tion of green color, reducticn of moisture loss and soluble pectin 
formation, and a reduced respiration rate indicate that the cold stor- 
age life of Bartlett pears was lengthened by packing in any of the 
sealed films used. 
3 
