Papaya Fruit Softening: Role of Hydrolases

Abstract

Papaya (Carica papaya L.) cultivars show a wide variation in fruit softening rates, a character that determines fruit quality and shelf life, and thought to be the result of cell wall degradation. The activity of pectin methylesterase, β-galactosidase, endoglucanase, endoxylanase and xylosidase were correlated with normal softening, though no relationship was found between polygalacturonase activity and softening. When softening was modified by 1-MCP treatment, a delay occurred before the normal increase in activities of all cell wall activities except endoxylanase which was completely suppressed. Significant cell wall mass loss occurred in the mesocarp tissue during normal softening, but did not occur to the same extent following 1-MCP treatment. During normal softening, pectin polysaccharides and loosely bound matrix polysaccharides were solubilized and the release of xylosyl and galactosyl residues occurred. Cell wall changes in galactosyl residues after 1-MCP treatment were comparable to those of untreated fruit but 1-MCP treated fruit did not soften completely. The changes in the cell wall fractions containing xylosyl residues in 1-MCP treated fruit showed less solubilization and a higher association of xylosyl residues with the pectic polysaccharides. The results indicated that normal modification of cell wall xylosyl components during ripening did not occur following 1-MCP treatment at the color-break stage, this was associated with the failure of these fruit to fully soften and a selective suppression of endoxylanase activity. The results support a role for endoxylanase in normal papaya fruit softening and its suppression by 1-MCP lead to a failure to fully soften. Normal papaya ripening related softening was dependent upon the expression and activity of endoglucanase, β-galactosidase and endoxylanase.

The role of hydrolases in the loss of firmness and of the changes in sugar content during the post-harvest maturation of Carica papaya L. var solo 8

“…2). These results agree with those of Thumdee et al (2010) who showed that hydrolase activities were weak in papayas harvested at the immature stage. It should be noted that the loss of firmness of the fruit increases as the enzyme activity does in the fruit cell wall (Sancho et al 2010).…”

Influence of 1-Methylcyclopropene on the Biochemical Response and Ripening of ‘Solo’ Papayas

“…The greater firmness of fruits treated with 1-MCP is probably associated with a reduction of pectinolytic enzymes activity, caused by the lower ethylene action. Similar results were obtained with apples (hEnDGES et al, 2011), bananas (yAn et al, 2011 and papayas (ThUMDEE et al, 2010) treated with 1-MCP inhibitor. Firmness is an important quality attribute for papayas and direct influence fruit storage shelf life and consumer acceptance.…”

“…4 to 6). Thumdee et al (2010) also observed higher concentrations of sugar in 1-MCP treated papayas. As discussed previously, an additional supply of carbon could come from the cell wall disassembly or even organic acids.…”

Papaya: Nutritional and pharmacological characterization, and quality loss due to physiological disorders. An overview

“…However, other's research shows that endoPG is not a major cause of papaya softening. Thumdee, Manenoi, Chen, and Paull (2010) suggest that in normal papaya ripening conditions the softening was dependent upon the expression and activity of endogluconase, β-galactosidase and endoxylanase. These authors show high relationships between endoxylanase activity and papaya softening and its complete activity suppressed in 1-MCP treated fruit.…”