CHANGES IN THE PECTIC SUBSTANCES OF APPLES DURING DEVELOPMENT AND POSTHARVEST RIPENING .1. ANALYSIS OF THE ALCOHOL INSOLUBLE RESIDUE

Cell wall material in the form of an alcohol-insoluble residue (AIR) w as prepared from apples during growth and maturation on the tree and a t different stages of ripening during postharvest storage. The galactu ronic acid, neutral sugar, starch content as well as the degree of ace tylation of the AIR were determined for each stage as was the degree o f methyl esterification of the pectic substances. During the first wee ks of development, the AIR content of the fruit decreased; it then sta yed constant until the end of storage. The galactose and arabinose con tent of the AIR decreased with time while the galacturonic acid conten t stayed almost constant. Hardly any changes were observed in the degr ees of methyl esterification and acetylation. The unripe fruit contain ed appreciable amounts of starch whereas none could be determined shor tly after harvest. The significance of the losses of arabinose and gal actose residues will be examined in a further paper.