270 EFFECTS OF INTERMITTENT WARMING ON CELL WALLS OF NECTARINES
Nectarine fruit (Prunus persica (L) Batsch) cv. Fantasia, were ripened immediately after harvest (normal ripening), or stored for 6 weeks either continuously at 0°C or were intermittently warmed (IW) for 48 h at 20C after 2 and 4 weeks, and then ripened. Fruit subjected to IW ripened normally, whereas the continuously stored fruit developed mealiness during ripening. Normal ripening was associated with solubilization and depolymerization of pectic polymers and a net loss of galactose. Only limited pectic solubilization and removal of side chains occurred during ripening of mealy fruit. Pectic polymer polymerization occurred at each IW occasion continued during ripening after storage, but was not as extensive as in normally ripened fruit. Mealy fruit had high autolytic capacity, probably as a result of insoluble pectic polymers in the cell wall that were not solubilized during ripening. The release of uronic acid suggests that cool storage temperatures do not irreversibly inhibit polygalacturonase activity.