Douglas D. Archbold,1 Rumphan Koslanund,2 and Kirk W. Pomper3
ADDITIONAL INDEX WORDS. kentucky banana, Asimina triloba
SUMMARY. To facilitate the growth of a commercial pawpaw (Asimina triloba) industry, several problems with harvest and postharvest handling of fruit need to be resolved. Pawpaw fruit ripening is characterized by an increase in soluble solids content, flesh softening, increased volatile production, and a loss of green color intensity. Within 3 days after harvest, ethylene and respiratory climacteric peaks are clearly evident. Softening of fruit is due to the action of at least four enzymes, with the softening proceeding from the surface to the interior tissue. Fruit on a single tree can ripen over a 2-week period, creating labor problems. When immature fruit is harvested it does not ripen, even if treated with ethephon at 1000 mg·L⁻¹ (ppm), but the use of commercially available growth regulators both pre- and postharvest warrants further study. Fruit soften very rapidly at room temperature after harvest and have a 2-to 4-day shelf life. However, we have stored pawpaw fruit for 1 month at 4 °C (39.2 °F) with little change in fruit firmness and fruit apparently continue normal ripening upon removal to ambient temperature. The optimum temperature and duration for holding fruit will need to be determined. Further extension in pawpaw storage life may be feasible with controlled or modified atmosphere storage. Although there are a number of practical problems with pawpaw harvest and postharvest storage that need to be addressed, we hope to develop recommendations for harvest and handling of fruit in the near future.
The pawpaw fruit has become the focus of a significant regional effort to expand its production and marketing. The unique fruit qualities of pawpaw suggest that it has great potential as an alternative high-value crop in the eastern United States and beyond. The primary impediment to introduction of pawpaw into both fresh and processing markets is its perishability (Peterson, 1991), first noted in 1916 by the American Genetics Association (Popenoe, 1916, 1917). To date, appropriate harvest and storage practices for pawpaw fruit have not been studied. In order to facilitate the growth of a commercial pawpaw industry, we are evaluating harvest indices and storage techniques with the goal of developing a set of recommendations for handling the fruit. The primary problems, though not mutually exclusive, can be broadly categorized as ripening issues and cold storage issues.
Pawpaw fruit ripening is characterized by an increase in soluble solids content (up to 20%), flesh softening, increased volatile production, and, in some genotypes, a decline in green color intensity (McGrath and Karahadian, 1994). The volatile profile during ripening consists primarily of ethyl and methyl esters (McGrath and Karahadian, 1994; Shiota, 1991).
1Professor of horticulture, Department of Horticulture, University of Kentucky, Lexington, KY 40546-0091. To whom reprint requests should be addressed.
2Graduate student, Department of Horticulture, University of Kentucky, Lexington, KY 40546-0091.
3Principal investigator of horticulture and curator, USDA National Clonal Germplasm Repository for Asimina species. Atwood Research Facility, Kentucky State University, Frankfort, KY 40601-2355.