- 7 - 



CA to raise the atmosphere to either 121 or 151 CO2 (with about 31 

 Oo)- Samples were kept at 38°F in 12% CO2 for 3 weeks, and in 151 

 for 1,2, or 3 weeks, before transfer to 31 O9, 51 CO2 and 38°F; 

 samples were examined in January, March and May. 



The effects of the treatments on fruit firmness are shown in 

 Table 1. Benefit to 'Mcintosh' was substantial. All treatments 

 retarded softening, and the effect persisted throughout the storage 

 season. These values are for fruit kept 1 day at room temperature 

 after removal from storage, but substantial differences were also 

 measured after 7 days at room temperature, so the benefit should 

 carry through to the consumer. 'Cortland' apples responded less 

 than 'Mcintosh' ; only 15% CO2 for 3 weeks produced a measurable 

 difference in May. 



The benefit to 'Mcintosh' was obtained at a price; CO2 caused 

 injury to some fruits. CO2 injury can be of 2 forms: an exernal 

 scald-like injury on the green portion of the fruit; and, an inter- 

 nal damage characterized by dry pockets in the flesh, that often 

 leads to breakdown of the fruit. Both forms of CO2 injury appeared 

 in and on 'Mcintosh. ' 



The scald-like injury occurs during the CO2 exposure and was 

 detectable at all examinations. It resulted from all treatments 

 to 'Mcintosh,' but the amount of injury was usually only 1-2% of 

 the total number of fruit. This injury can be sorted out easily, 

 gets no worse during later storage, and would probably be tolerable 

 because of the firmness benefits obtained on 'Mcintosh.' 'Cortland* 

 showed none of this injury. 



The internal injury is of much more concern. It was not de- 

 tected until May, could not be removed by sorting, got worse with 

 time, and was worse in larger than in smaller fruits. The percent 

 occurrence was not determined, but some internal injury was present 

 in all the treated samples of 'Mcintosh. ' This injury is probably 

 not tolerable. Again, however, injury did not occur in 'Cortland' 

 from any treatment. 



The 1974-75 test clearly illustrated that 1) high CO2 can 

 sharply retard softening of 'Mcintosh, ' but 2) 'Mcintosh* can be 

 severely injured if exposed to too high a CO2 level at the begin- 

 ning of storage. Thus, it is obvious that considerable work remains 

 to be done on this subject. 



Other experiment stations have also been examining high CO2 

 treatments on 'Mcintosh' during the past several years, and their 

 findings suggest that 12-13% CO2 for about 2 weeks at the begin- 

 ning of CA may be optimum. However, many questions must be answered 

 before any commercial recommendations can be made. Some of these 

 questions are: How quickly after harvest must the high CO2 level 

 be obtained to influence firmness? (Dr. Couey finds half the bene- 

 fit to 'Golden Delicious' to be lost if treatment is delayed only 

 10 days.) Is the benefit related to maturity of the fruit at har- 



