Ripening control with ethylene and ethephon on a rapid-deastringency system in persimmon fruits

The rapid-deastringency system on which removal of astringency was achieved by treatment of 0.625-2.50 ml of 99.5% ethanol/kg fresh fruit and/or above 95% carbon dioxide for 3-5 hrs at 40 degrees C, followed by sealed incubation for 12 hrs at 40 degrees C ('post-heating') after temporary opening, and thoroughly by following open incubation at 20 degrees C, removed astringency from persimmons (Diospyros kaki L. cv. 'Monpei') for 3-7 days. The treated fruits, however, remained unripe and had a 'crisp' texture for a longer period ('93 : 27 days; '95 : 12 days). Therefore, a possibility of ripening control with ethylene and ethephon was investigated. 'Monpei' fruits were softened and produced 3.5-7.2 mu l/kg.hr of ethylene at the 4th day after application of 1000ppm ethylene for 24 hrs at 20 degrees C, being sensitive considerably to external ethylene. Application of 5 ppm ethylene during deastringency for 12 hrs promoted decrease of flesh firmness and peel coloring, led to giving optimum taste for 4-8 days after 'post-heating'. On the application after deastringency, there was little effect of ethylene; ethephon dipping at 50 and 500 ppm promoted ripening, but dotted scarlet on the fruit skin was found.