Short-Term Controlled Atmosphere Storage of Apples
Controlled atmosphere (CA) storage for 30 or 60 days reduced quality losses for Jonagold, Golden Delicious, Delicious, Granny Smith and Fuji apples. After 30 days Jonagold and Golden Delicious apples from CA were firmer, had higher acidity and less yellow (more green) color than apples from regular atmosphere (RA) storage. Delicious and Granny Smith apples had better firmness after 60 days of CA storage than fruit from RA. In addition, Granny Smith apples from CA had more acid and greener color than apples from RA. After 8 days ambient storage, little loss in firmness and no loss in acid content occurred with Jonagold or Golden Delicious apples from CA compared to the significant loss in firmness and acid when stored in RA. After ambient storage for 8 days Jonagold, Golden Delicious and Granny Smith apples retained a freshly harvested apple color with more green and less yellow development when stored in CA rather than RA. In Fuji apples the treatments had no effect except for improved acid retention if stored in CA. A combination of 30 days CA followed by 30 days RA produced Jonagold, Golden Delicious and Delicious apples that were superior in quality to apples from 60 days RA.
Present controlled atmosphere (CA) storage codes in Washington State (WAC, 1989), established in 1964, requires that before fruit can be certified as CA, apples must be stored for 90 days at 5% O2 or less and that the O2 requirement be met within 20 days after sealing the room. Since these requirements were established, technology has advanced and CA conditions can be at a 1% O2 level in a matter of hours. There is no doubt that long?term storage in CA has enhanced the dessert quality of apples (Patterson and Workman, 1962; Olsen and Schomer, 1964; Olsen, 1969; Meheriuk and Pruitt, 1973; Lidster et al., 1980; Meheriuk et al., 1984; Patterson and Nichols, 1988; Mattheis and Olsen, 1989; Meheriuk, 1991). If new technology of establishing very low O2 levels quickly is taken into consideration, there is good reason to believe that early storage quality advantages would be present. Some research (Couey and Olsen, 1975; Wang and Mellenthin, 1975; Lau and Looney, 1978; Olsen and Bartrum, 1978) has been concerned with short?term changes in CA atmospheres, but after this short period of time normal CA patterns were established for long-term storage. Little, if any, research has been conducted on apple response to short-term (60 days or less) CA storage.
Materials and Methods
Apples (Malus domestica Borkh) from three trees each of Delicious, Golden Delicious, Granny Smith and Fuji were harvested at commercial maturity (WAMP, 1986) and seven to ten days later, for two harvest seasons. Jonagold was harvested at commercial maturity for only two seasons. Immediately after harvest the fruit was graded and sorted for uniform size. Acceptable fruit (360/harvest or 120/tree) for each crop season and cultivar were divided into two groups and stored at 1 °C in either RA or CA storage. CA conditions for regular atmosphere (RA) or controlled atmosphere (CA) Delicious, Granny Smith and Fuji were 1% O2 and 1% CO2 for Golden Delicious and Jonagold were 1% O2 and 3% CO2. After 30 and 60 days of storage apples were removed and quality comparisons made between RA and CA storage. A portion of the fruit was removed after 30 days from CA and stored an additional 30 days under RA. Fruit that had received a combination of CA and RA (30/30) storage were compared with fruit from 60 days of RA or CA storage alone. Analysis of Jonagold, Golden Delicious, Delicious, and Fuji was performed immediately after removal from storage and after eight days ambient temperature storage and after 10 days ambient storage for Granny Smith. Twenty fruit (storage type/storage time/rep) were used for quality analysis.
Results and Discussion
Firmness values for Jonagold and Golden Delicious apples were strongly influenced by storage atmosphere at 30 days after harvest (Table 1). A firmness loss of 15.2% and 9.3% was determined for Jonagold and Golden Delicious, respectively, for those apples stored 30 days in RA compared with identical apples from 30 days CA. By the end of a 60?day storage period firmness in apples from RA compared to CA storage had decreased by 25.3% and 17.4% for Jonagold and Golden Delicious, respectively. Firmness values for Delicious apples were not different after 30 days RA and CA storage, but after 60 days of storage Delicious apples from CA were 7.5% firmer than Delicious apples from RA.
Granny Smith apples from CA storage consistently averaged 3.5% higher than Granny Smith apples from RA storage. Firmness values of Fuji apples were similar regardless of storage or duration.
Firmness values of Jonagold, Golden Delicious, Delicious and Granny Smith apples from RA storage declined more rapidly during the ambient storage period than similar apples from CA storage (Table 1). Firmness of Jonagold apples from RA storage declined 24.7% during an 8?day ambient temperature storage period, however, over the same time period, the decline in firmness values for apples from CA storage was only 9.7%. This more rapid decline in firmness of apples from RA storage during ambient temperature storage was also evident for Delicious apples, but not to the same extent. Delicious apples from RA storage lost 14.6% of their firmness during ambient temperature storage compared to 9.5% for Delicious apples from CA storage.
The decline in firmness during ambient temperature storage of Granny Smith apples was only apparent when the apples were from RA storage. Granny Smith apples from CA did not decline in firmness after an 8?day ambient temperature storage. Except for Fuji, firmness values were higher in CA apples compared to RA apples after eight days at ambient temperature. If Jonagold and Golden Delicious apples are considered, this difference in firmness was evident before the initiation of ambient temperature storage.
Acid content (TA) of Jonagold, Golden Delicious, Granny Smith, and Fuji was superior in CA apples regardless of storage time (30 or 60 days) when compared to identical RA apples (Table 2). Differences in acid content between RA and CA storage types was particularly large for Jonagold and Golden Delicious and a moderate difference in acid content present for Granny Smith and Fuji apples. Acid content of Delicious apples from RA or CA was similar regardless of storage or time.
Time in storage had a distinct influence on the acid values of Jonagold apples. As storage time progressed from 30 to 60 days, acid values decreased for Jonagold apples from RA, but no decrease in acid values was evident for Jonagold from CA storage. After 60 days CA storage, only Delicious apples had acid values equal to apples from RA storage. In all other instances, acid values were highest in CA apples regardless of storage time.
Both RA or CA storage had a visible effect on Jonagold, Golden Delicious and Granny Smith apple color (Table 3). In these three cultivars, CA stored apples were darker in color (lower Hunter 'L' values) and had a less yellow (lower Hunter 'b' value) greener color (higher 'hue' value) than similar apples from RA storage. This color difference between RA and CA storage was visually apparent. As storage time progressed from 30 to 60 days, color changed in all three cultivars (Jonagold, Golden Delicious and Granny Smith) . Apples from 60 days storage, particularly Golden Delicious and Granny Smith, were lighter in color with a distinct change in Hunter 'b' and hue values (yellower, less green appearance). Jonagold apples became lighter in color as storage time progressed with more yellow color (Hunter 'b'). Apple color became lighter (higher Hunter 'L' values) in all three cultivars; during an 8?day ripening period. No change in Hunter 'b' or hue values was evident for Jonagold apples after eight days ambient temperature storage, but Golden Delicious and Granny Smith lost green color and became a more pronounced yellow during ambient temperature storage.
Time in storage resulted in a color change for Delicious apples but not Fuji apples (Table 4). Delicious apples from CA storage were lighter in color with less red development coupled with a higher hue value (more yellow). Ripening time had no influence on color for Fuji apples and only a slight influence on Delicious apples. In Delicious apples, as ripening time progressed, there was an increase in hue values toward a yellower color.
Jonagold, Golden Delicious and Delicious apples from CA were firmer than apples from RA storage. Jonagold, Golden Delicious and Delicious apples subjected to a combination storage of 30 days of CA followed by 30 days of RA were firmer than apples from RA only (Table 5). In the case of Delicious apples, firmness values were identical for CA and CA/RA storage, and both were higher than firmness values for RA apples. Firmness values for Jonagold and Golden Delicious from CA/RA storage were less for apples from CA storage but higher for apples from RA storage. No firmness differences were present for Granny Smith or Fuji when apples from CA/RA storage were compared with CA or RA storage alone (data not shown).
Acid values for Jonagold and Golden Delicious after 60 days of CA/RA storage were between those acid values determined for apples from CA (highest) and RA (lowest) alone. Acid values for Delicious apples were similar in all three storage types. No acid differences were present for Granny Smith and Fuji apples from the three storage types (data not shown).
Not only consumers, but also state and federal inspectors, use apple texture or firmness as an indicator of quality. Other attributes used to judge fruit quality can include flavor and color. Almost immediately after an apple is harvested quality starts to decline. This decline can be slowed using reduced temperature (RA) and slowed even more by manipulation of the atmosphere (CA). How rapidly quality declines during either RA or CA storage depends on the cultivar. Historically, CA storage has been used to increase market availability of apples over a 12?month season. However, there are quality advantages for apples after only a short storage time in CA. In this study, response time to CA was cultivar dependent. CA storage of only 30 days after harvest resulted in a significant reduction in quality losses of both Jonagold and Golden Delicious apples, the two softer cultivars. CA storage of 60 days resulted in a reduction of quality losses for both Delicious and Granny Smith apples.
Differences in firmness values for apples stored under short-term CA could be the determining factor in fruit meeting market requirements, particularly in the case of soft cultivars such as Jonagold or Golden Delicious where firmness values were significantly (1.5 to 2.5 lb) different between CA and RA storage in a short term (30 days). A high acid content produces an apple with more flavor. Higher acid content was present in apples from short?term CA for all apple cultivars in this study except Delicious. This lack of difference in Delicious acid content was directly related to its initial low acid content. Granny Smith apples in both RA and CA storage had sufficient acid content for good flavor. Acid content of Jonagold, Golden Delicious and Fuji was enhanced with the use of CA storage. Lack of color change for Jonagold, Golden Delicious and Granny Smith from CA storage could be used for market advantage. Many markets prefer a greener Jonagold and Golden Delicious apple. In the case of Granny Smith apples, the amount of green color present reflects directly upon the fruit grade.
A combination (CA/RA) of the two storage types could improve the quality of apples in the market. The ideal conditions for good quality apples would be to use CA in both storage and transit. Presently, most apples for early shipment are stored and shipped in RA only. Apples that receive 30 days of CA before transit (RA) should arrive in better condition than apples stored in RA only through the storage and transit period.
Good quality fruit is in demand for export and some of the largest demand for U.S. grown apples is from November through January, which is at or near the end of the quality life of RA-stored fruit. Apples stored under a short-term CA environment (60 days or less) would be in better condition than apples from RA and subsequently would be of higher quality on the early export market.
Appreciation is expressed to the Washington State Tree Fruit Commission for grant funds partially supporting this study.
Couey, H.M. and K.L. Olsen. 1975. Storage response of Golden Delicious apples after high carbon dioxide treatment. J. Amer. Soc. Hort. Sci. 100:148-150.
Lau, O.L. and N.E. Looney. 1978. Effect of prestorage high CO2 treatment on British Columbia and Washington State Golden Delicious apples. J. Amer. Soc. Hort. Sci. 103:341-344.
Lidster, P.D., E.R. Forsyth, and H.J. Lightfoot. 1980. Low oxygen and carbon dioxide atmosphere for storage of McIntosh apples. Can. J. Plant Sci. 60:299-301.
Mattheis, J. and K. Olsen. 1989. Evaluation of commercial Delicious apples stored at 1.1 °C and 3% CO2, p. 287-294. In: J.K. Fellman (ed). Proc. 5th National Controlled Atmosphere Res. Conf., June 1989, Wenatchee, WA.
Meheriuk, M. and S.W. Pruitt. 1973. Effects of picking late, delayed storage, storage temperature and storage atmosphere in the quality of Starking Delicious apples. J. Amer. Soc. Hort. Sci. 53:593-595.
Meheriuk, M., O.L. Lau, and J.W. Hall. 1984. Effect of some postharvest storage treatments in the incidences of flesh browning in controlled atmosphere stored Delicious apples. J. Amer. Soc. Hort. Sci. 109:290-293.
Meheriuk, M. 1991. CA storage conditions for commercially grown apples. Compiled by: Meheriuk, Ag. Can. Res. Sta., Summerland, B.C. Canada.
MSTAT. 1988. Version 1.0 Michigan State Univ., East Lansing, MI.
Olsen, K.L. and H.A. Schomer. 1964. Oxygen and carbon dioxide levels for controlled atmosphere storage of Starking and Golden Delicious apples. USDA, AMS MRR653.
Olsen, K.L. 1969. Controlled atmosphere storage of apples. Proc. Nat. CA Res. Conf., Mich. State Univ. Hort. Rep. 9:60-63.
Olsen, K.L. and R.D. Bartrum. 1978. Carbon dioxide treatment of Golden Delicious apples. USDA, SEA ATT-W2/September.
Patterson, M.E. and M. Workman. 1962. The influence of oxygen and carbon dioxide in the development of apple scald. Proc. Amer. Soc. Hort. Sci. 80:130-13.
Patterson, M.E. and W.C. Nichols. 1988. Metabolic response of Delicious apples to carbon dioxide in anoxic and low-oxygen environments. HortScience 23:866-868.
Wang, C.Y. and W.M. Mellenthin. 1975. Effect of short?term high CO2 treatment on storage of d'Anjou pear. J. Amer. Soc. Hort. Sci. 100:492-495.
Washington Agriculture Code 16-690-025. Washington controlled atmosphere storage requirements. March 31, 1989.
Washington Apple Maturity Program Handbook. 1986. Washington Apple Maturity Program, Wenatchee, WA.
Dr. Steve R. Drake
USDA ARS Tree Fruit Research Laboratory
1104 N. Western Ave., Wenatchee, WA 98801
15th Annual Postharvest Conference
March 9-10, 1999