PECTIC POLYMER CHANGES IN NECTARINES DURING NORMAL AND ABNORMAL RIPENING

Nectarines (Prunus persica, cv Fiesta Red) were harvested and either r ipened for five days at 20 degrees or stored for eight weeks at 0 degr ees in air or in a controlled atmosphere (CA) of 10% CO2 and 15% O-2 b efore ripening. Air-stored fruit developed the flesh disorder of meali ness, while CA-stored fruit did not. During storage, the degree of est erification of the cell wall decreased in air- but not CA-stored fruit s. Air-stored fruits retained more pectin in the sodium carbonate frac tion after ripening and the polymers in the trans-1,2-diaminocyclohexa ne-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 le d to loss of arabinose from the sodium carbonate and guanidine thiocya nate fractions, and a lower arabinose content was also found in the CD TA 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-store d fruit, the CA-stored fruit showed changes in cell wall components wh ich were very similar to those in fruit ripened immediately after harv est. 4