D'Anjou Harvest Maturity and Storage
The following information on d'Anjou maturity and storage was prepared under the auspices of the Pear Bureau and Winter Pear Control Committee of Washington, Oregon and California. It has been edited for inclusion in this newsletter.
The last general publication of this type was issued in 1979, by the Oregon State University Agricultural Experiment Station, as Special Report 550, titled Commercial Handling and Storage Practices for Winter Pears," by Dr. Elmer Hansen and Walt Mellenthin. Copies of this publication are available from Dr. Kupferman. The article that follows updates those recommendations.
Readers should also be aware of Dr. Paul Chen's and Diane Borgic's 1983 article on this subject, "The Maturity and Storage of D'Anjou Pears," Postharvest Pomology Newsletter Vol. 1(3):17-18. Area Extension Agent Paul Tvergyak summarized information about maturity in 1985 in an article titled Pear Maturity Indexes Used to Time Harvest Date. Drs. Kupferman, Robert Spotts and David Sugar collaborated on Practices to Reduce Postharvest Pear Diseases. A 1995 update of this article is also available online. Reprints of these articles are also available from Dr. Kupferman.
The increasing production of d'Anjou pears in the Northwest is forcing growers to review factors which affect the postharvest life and ability of the product to ripen with quality for the consumer. Harvesting immature fruit, then using unfavorable handling and storage practices will reduce storage life, ability of the fruit to ripen, and quality.
The Pacific Northwest is the major producer of winter pear varieties in the United States. The term "winter pear" denotes the late fall and winter marketing season of this class of pears. The Beurre d'Anjou variety is an example of a late winter cultivar that is available in the market during the winter season and into the following early summer.
Over the years flesh firmness has been a very reliable index for determining harvest of pears. It is important to match fruit maturity to the storage regime and to segregate fruit for me various marketing periods at harvest.
Firmness levels are based on selecting a sample of 10 to 15 pears of similar moderate size (box size 100 or 120) from trees representative of the orchard. Test each orchard at approximately the same time of day. Do not mix fruit from young interplants with those from mature trees. Calibrate all testing equipment before the season starts. Hold the tester vertical over the pared area, and apply a uniform, steady pressure applied until the plunger breaks through the flesh. Take three tests on each fruit. Avoid the sun blushed area. Strive to have 75% of the pears in the recommended pressure range at the start of harvest.
To provide the best potential ripening quality of d'Anjou pears after storage, it is essential to match harvest maturity to the storage method and to consider the chilling requirements of the fruit. See Table 1.
Firmness, Chilling and Storage
D'Anjou pears which have an average firmness of 16 pounds or higher are immature. They will not ripen properly after any length or type of storage. In addition, they are much more susceptible to scuff marks, scald and shrivel.
When fruit firmness at harvest is 15 to 14 pounds, d'Anjou pears require at least 60 days cold storage in order to ensure normal ripening and fruit quality. After meeting the 60-day chilling requirement, these pears will be of good quality for the rest of the market season. This early harvested fruit responds well to long-term High-CO2 (11 to 12% CO2 for 2 weeks) followed by CA storage. Or, low oxygen storage (1% O2 under 0.1% CO2) can be used. This combination of maturity and storage provides the best quality for late season marketing--April and later. For long-term CA storage, select d'Anjou fruits which have been picked from the beginning to the middle of the harvest season. Avoid delaying CA storage following harvest, as delay reduces the postharvest life and fruit quality.
Pears which are harvested in the firmness levels of 14 to 13 pounds require at least 45 days of chilling. These pears are well adapted to High-CO2 treatment, followed by regular cold storage (30 to 31 °F) for sales in the January to April market. As an alternative, use regular CA storage (2% O2, 0.8 to 1% CO2) for fruit for the February to May market.
When harvest firmness levels are below 13 pounds, the chilling requirement is at least 25 days. These d'Anjou pears should not be placed in CA storage or treated with High-CO2, since these more mature pears can develop internal browning from such storage treatment. Rather, store these pears in regular cold storage, transport them from orchard to storage the same day they are harvested, and cool them rapidly to 30 to 31 ° F. They will be best marketed from November through December.
Late harvest pears having a firmness level of 12 to 11 pounds have a chilling requirement of about 25 days. They need cooling as rapidly as possible.
Days from Full Bloom
D'Anjou pears are usually harvested between 135 and 147 days from full bloom. Under growing conditions where firmness levels remain above 15 pounds through 145 days from full bloom, harvest these pears as rapidly as possible. Permitting the pears to remain on the trees after 155 days from full bloom will usually result in a shorter storage life due to more rapid softening.
Soluble solids are not a reliable maturity indicator of time of harvest for d'Anjou pears, but are useful for quality and storage management. Fruit need at least 10% soluble solids to have acceptable quality and to prevent freezing in storage. Higher soluble solids (11 to 12%) indicate higher fruit quality, longer storage life, and less shrivel.
Other Usable Indices
Color, corking of lenticels, and general finish all aid in determining time of harvest. Lenticels of immature pears are usually white or light colored, and as cork cells develop they become more brown and shallow. Brown in the lenticels is a good indicator that the fruit will ripen without shriveling. Color between the lenticels also becomes lighter green than at the lenticel. The increased waxiness of the skin and rounding of the fruit are also guides.
Rapid Cooling Is Essential
Delayed storage following harvest influences the skin color, fruit firmness and postharvest life. Rapid removal of field heat is essential for lengthening postharvest life. Fruit must be moved from the orchard into storage within 24 hours.
Forced air cooling or pressure cooling systems, which move cold air through the bins of fruit instead of over them, reduce the time for the removal of field heat.
When market conditions dictate that fruit at high harvest firmness levels (15 or 14 pounds) should be marketed before satisfying the 60-day chilling requirement, ethylene gas can be introduced into the conditioning room to initiate ripening. Often it is necessary to apply the gas more than once to keep them ripening. However, if the chilling requirement has been completed, the pears will not require ethylene.
Marketing of preconditioned d'Anjous has been studied and implemented for a number of years. The technique allows the consumer to buy a ready-to-eat product. Where preconditioning of fruit should take place--whether at the point of origin or at the terminal market--has long been been debated. Conditioning guidelines need to be established for each of these methods to increase the amount of conditioned fruit at the market. The fully ripened, high quality d'Anjou pear should have a firmness slightly under 3 pounds and at least 12% soluble solids. Most importantly, it should have a smooth and juicy texture, and sweet flavor.
Bartram, R. D. 1977. Retail quality of d'Anjou pears found in Virginia through New York Area, March & April, 1977. Paper prepared for Washington Tree Fruit Research Commission.
Bartram, R. D. 1978. Retail quality of D'Anjou pears found in Southern California, Arizona & Texas, March & April, 1978. Paper prepared for Washington State Tree Fruit Research Commission.
Chen, P. M., and W. M. Mellenthin. 1981. Effects of harvest date on ripening capacity and postharvest life of d'Anjou pears. J. Amer. Soc. Fort. Sci. 106:38-42.
Chen, P. M., W. M. Mellenthin, and D. M. Borgic. 1983. Changes in ripening behavior of d'Anjou pears (Pyrus cummunis, L.) after cold storage. Scientia Hortica. 21:137-146.
Chen, P. M., R. A. Spotts, and W. M. Mellenthin. 1981. Stem-end decay and quality of low oxygen stored 'd'Anjou' pears. J. Amer. Soc. Fort. Sci. 106:35-38.
Claypool, L. L., and R. B. Fridley, 1966. Precision in a pressure tester Western Fruit Grower 20:18-19.
G.M.A. Research Corp., June 1985. Winter pears 21038 (Measures market awareness and use of winter pears among consumers), Research Report, Winter Pear Bureau.
Hansen, E. 1957. Reaction of pears to carbon dioxide and oxygen content of the storage atmosphere. Proc. Amer. Soc. Fort. Sci. 69:110-115.
Hansen, E. 1962. Factors affecting susceptibility of pears to carbon dioxide injury. Proc. Amer. Soc. Fort. Sci. 80:146-153.
Hansen, E., and W. M. Mellenthin, 1979. Commercial handling and storage practices for winter pears, Oregon State University Agricultural Experiment Station Special Report 550, Corvallis.
Mellenthin, W. M., and P. M. Chen. 1981. Softening and ripening of 'd'Anjou' pears as influenced by simulated transit temperatures. J. Amer. Soc. Fort. Sci. 106:35-38.
Mellenthin, W. M., and S. B. Kelly. 1980. Low oxygen effect on dessert quality, scald prevention, and nitrogen metabolism of 'd'Anjou' peer fruit during longterm storage. J. Amer. Soc. Fort. Sci. 105:522-527.
Mellenthin, W. M., and C. Y. Wang. 1974. Friction discoloration of d'Anjou pears in relation to fruit size, maturity and polyphenol oxidase. Hortscience 9(6):592-593.
Porrett, S. W. 1964. The effect of temperature on postharvest physiology and storage life of pears. Can. J. Plant Sci. Vol. 44.
Porrett, S. W. 1976. Preharvest temperatures in relation to postharvest quality of d'Anjou Pears. J. Amer. Soc. Fort. Sci. 101:302-305.
Wang, C. Y. 1976. Effect of different handling methods on cooling rate and moisture loss of d'Anjou pears stored in bins. Hortscience 11(4):397-398.
Wang, C Y., and W. M. Mellenthin. 1975. Effect of short term high CO2 treatments on storage of d'Anjou pears. J. Amer. Soc. Hort. Sci. 1 00(5):492-495.
Initiated by Jim Klahre and completed by the cooperative efforts of Walt Mellenthin, Dr. Paul Chen, Fred Valentine, Earl Talley, Richard Bartram, and Dr. Tom Raese
Post Harvest Pomology Newsletter, 5(2): 10-14