Changes in Pectic Substances and Cell Wall Degrading Enzymes During Muskmelon Fruit Ripening

Abstract

Changes in pectic substances and the activities of the cell wall
degrading enzymes, pectin esterase (PE) and polygalacturonase (PG) were
evaluated during muskmelon fruits ripening. Respiration rate
progressively increased in a climacteric pattern. Fruit flesh firmness
steadily declined and rind yellow colour increased during ripening. Total
and insoluble pectins progressively decreased, while the soluble pectins
increased with fruit ripening. Positive correlation coefficients were
obtained between total and insoluble pectins, and fruit flesh firmness.
Total protein and PE activity increased up to the climacteric peak of
respiration and decreased afterwards. PG activity progressively increased
during fruit ripening, with high correlation between the increase in
enzyme activity and fruit softening in the three muskmelon cultivars. This
may indicate that the two enzymes polygalacturonase (PG) and pectin
esterase (PE) are the main enzymes responsible for fruit softening during
muskmelon fruit ripening.