PECTIC POLYMER CHANGES IN NECTARINES DURING NORMAL AND ABNORMAL RIPENING

Nectarines (Prunus persica, cv Fiesta Red) were harvested and either ripened for five days at 20 degrees or stored for eight weeks at 0 degrees in air or in a controlled atmosphere (CA) of 10% CO2 and 15% O-2 before ripening. Air-stored fruit developed the flesh disorder of mealiness, while CA-stored fruit did not. During storage, the degree of esterification of the cell wall decreased in air- but not CA-stored fruits. Air-stored fruits retained more pectin in the sodium carbonate fraction after ripening and the polymers in the trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid (CDTA) and water-soluble fractions were of smaller M(r) than unstored or CA-stored fruits. Air storage also led to loss of arabinose from the sodium carbonate and guanidine thiocyanate fractions, and a lower arabinose content was also found in the CDTA fraction when air-stored fruits were ripened. The size distribution of components of the pectic fractions from air-stored fruits differed from fruits after harvest or CA-storage. In comparison with air-stored fruit, the CA-stored fruit showed changes in cell wall components which were very similar to those in fruit ripened immediately after harvest. 4