Changes in papaya cell walls during fruit ripening

Abstract The apparent molecular mass range of different extractable fractions of papaya fruit pectin and hemicellulose during fruit ripening was determined. The pectin molecular mass declined and the solubility of pectin in cyclohexane-diaminotetraacetic acid and Na 2 CO 3 solutions increased during ripening. The molecular mass decreased and the solubility of hemicellulose in KOH increased during ripening. Water soluble uronic acid increased 6-fold during ripening as the yield of cell wall material declined. The loss of high molecular mass pectins decreased throughout ripening while the demethylation rate was greater early in ripening. Changes in pectin molecular size did not parallel loss of fruit firmness during early ripening. The pectin fractions were mainly composed of rhamnose, glucose, xylose, galactose, mannose and arabinose, in decreasing order of concentration. Non-cellulosic glucose and xylose were the main neutral sugars in the hemicellulose fraction followed by mannose and galactose and traces of rhamnose and arabinose. These results suggested that pectin hydrolysis and the modification of hemicellulose both were involved in papaya fruit softening. Pectin hydrolysis was apparently more important during the late phase of fruit softening.