Suppression of ethylene perception extends shelf-life and quality of ‘Sunrise Solo’ papaya fruit at both preripe and ripe stages of development

Abstract

Papaya fruit (Carica papaya L. cv. ‘Sunrise Solo’) at pre-ripe (10 to 20 % surface yellow coloration) and ripe stages (70 to 80 % surface yellow coloration) of development were treated with 9 µl l–1 of the ethylene antagonist 1-methylcyclopropene (1-MCP) for 18 h at 20 ºC and then stored at the same temperature. The hypothesis addressed was that fruit at both early and advanced stages of ripening would respond beneficially, in terms of extended shelf-life, and quality retention, to exposure to 1-MCP. For fruit of both ripening categories, respiration and ethylene production, firmness, electrolyte leakage, titratable acidity, pH, soluble solids, and visual changes were recorded during storage. Pre-ripe fruit treated with the ethylene antagonist exhibited a 2-day delay in the respiratory climacteric maximum and showed suppressed but steadily increasing ethylene production throughout storage. A reduction in respiration and ethylene production were also noted for fruit treated with 1-MCP at the ripe stage. The rate of softening of fruit of both ripening categories was significantly reduced in response to 1-MCP. Firmness of pre-ripe fruit declined 52 % over 9 days of storage compared with 30 % for 1-MCP-treated fruit over the same time period. Firmness of ripe fruit at the start of storage was initially 60 % lower than initial values for pre-ripe fruit; however, 1-MCP significantly suppressed further softening of ripe fruit, with 1-MCP-treated fruit declining only 15 % over 8 days of storage whereas controls softened 60 % over a 6-day period. Electrolyte leakage in pre-ripe fruit was significantly suppressed by 1-MCP treatment through 11 days of storage. Efflux was higher in ripe fruit compared with pre-ripe fruit, but leakage values in ripe fruit were not significantly affected by 1-MCP. Soluble solid levels were not significantly influenced by 1-MCP for fruit of either developmental stage whereas the ethylene antagonist affected titratable acidity and mesocarp pH. Fruit treated with 1-MCP showed delayed loss of surface green colour in pre-ripe fruit and suppressed the intensity of yellow colour development of fruit treated when ripe. In informal sensory analyses, the period of table-ripe edibility of fruit treated when pre-ripe or ripe was extended 4 to 5 days and 3 to 6 days, respectively.