Submitted to: Peanut Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 4, 1997
Publication Date: N/A
Interpretive Summary: Peanuts flower over a period of about sixty days; therefore, at harvest time peanuts of different maturities are always found on the plants. Research has shown that mature peanuts have better flavor potential than immature peanuts. The work in this study revealed that harvested peanuts continue to mature when they are slow cured. These changes should result in a higher percentage of mature peanuts and overall better flavor quality potential in all sizes of peanuts. The data support the long standing idea that the old methods of stackpole curing peanuts result in peanuts of superior quality compared to peanuts bulk cured with heated air as prescribed by current technology. This unique observation on continued maturation during slow curing opens new vistas for peanut curing research which may lead to changes in field and handling methods. Further, discovery of this maturation phenomenon provides a unique model system for study of the physiology of maturation which has potential for identification of processes, compounds, activators, etc. that might be manipulated by classical breeding or genetic engineering to enhance early or timed maturation in peanuts.
Technical Abstract: Investigations to identify biochemical changes during curing led to the unique observation that peanuts have extensive potential for post harvest maturation during slow curing. In the hull scrape maturity profile the percentage of black maturity class pods increased from 15 to 45% and 21 to 57% in ca. 30 days after stacks were prepared in two consecutive years. Simultaneously, the number of pods in less mature classes generally decreased. The weight percentage of black pods increased from 19 to 42% and 37 to 62% after 10 stack days, respectively, in the two years. A similar but less extensive maturity progression was observed in detached pods in a temperature-relative humidity-controlled environment where drying rate was faster than in stackpoles but much slower than in conventional practices. Because pod size and seed size did not change during stackpole curing, maturation resulted in large increases in the percentage of mature peanuts (maturity distribution) in all commercial grade sizes. Moisture contents for orange and brown maturity classes related to cessation of color change in pods in both stackpoles and controlled environment treatments were about 29% and 22.5%, respectively. Physuiological seed maturation appeared to occur concurrently with hull color progressions as oleic acid/linoleic acid ratio in medium grade size peanuts within each maturity class were constant over curing time.