Delayed storage and controlled atmosphere storage of nectarines: two strategies to prevent woolliness

Both delayed storage (DS) of nectarine (Prunus persica cv. Flavortop) fruit s held for 48 h at 20 degrees C before storage, and controlled atmosphere ( CA) storage, fruits stored at 10% CO2, 3% O-2, alleviated or prevented chil ling injury manifested as woolliness in nectarine fruits stored for 4 or 6 weeks at 0 degrees C. Control fruits showed 80 and 100% woolliness during r ipening after 4 or 6 weeks at 0 degrees C, respectively. DS and CA were sim ilar in their beneficial effect after 4 weeks and CA was better after 6 wee ks storage. The two storage processes appeared to prevent woolliness by dif ferent mechanisms. DS initiated ripening so that at removal from storage po lygalacturonase (PG) activity was higher and pectin esterase (PE) activity lower than in control fruits. The PG activity increased further during ripe ning, and normal softening occurred in DS fruits. There was no difference i n mRNA abundance of PG and PE between DS and control fruits. CA repressed b oth mRNA levels and activity of PG during storage, but allowed recovery of activity during ripening. Endoglucanase (EGase) activity declined during ri pening in all fruits, but control fruits retained more activity than DS or CA fruits. The EGase mRNA level was high in control fruits during ripening after storage, and almost undetectable in all treatments at all other times . We postulate that the ratio between PG/PE either at removal (DS) or durin g ripening (CA) will determine whether woolliness develops or not. (C) 2000 Elsevier Science B.V. All rights reserved.