The commercial storage life of the nonastringent Japanese `Fuyu' persimmon (Diospyros kaki L.), grown in Israel, was extended from 6 to 18 weeks at 0C by modified-atmosphere packaging (MAP) in a low-density polyethylene (LDPE) film. MAP retarded fruit softening and inhibited development of peel and flesh disorders, which limited the storage life of the naked fruit. The fruit maintained its external and internal quality within the MAP during a subsequent week at 20C in the 0.08-mm LDPE film. Fruit quality deteriorated more rapidly in a 0.06-mm package. The difference between fruit quality in the two packs is attributed to specific physiological effects of the different atmospheric equilibria established due to film thickness.
Ruth Ben-Arie and Yohanan Zutkhi
Yolanta Saks, Lilian Sonego, and Ruth Ben-Arie
In `Jonathan' apples grown in Israel, the incidence of senescent breakdown after 5 months of storage at 0C was not correlated with total or water-soluble Ca content at harvest. Likewise, no other assayed component of the water-soluble or total mineral content (P, Mg, K) of the fruit pulp at harvest correlated with the disorder after storage. After storage, a general decrease in the solubility of Ca was observed. However, this decrease was not uniform in all fruit and, as a result, the correlation between water-soluble and total Ca content, which was high at harvest, diminished after storage. Water-extractable Ca from stored fruit was negatively correlated and water-soluble K/Ca was positively correlated with the incidence of senescent breakdown, whereas total Ca was not correlated.
Yolanta Saks, Lilian Sonego, and Ruth Ben-Arie
Mature-green `Anna' apples (Malus domestics Borkh.) reddened after harvest as a result of exposure to continuous cool-white fluorescent light. Color development was most rapid at 20C but most intense at 13C. At 2C, although the induction of red pigmentation was the slowest, a 72-hr exposure rendered color not significantly different from that of red, commercially harvested fruit. The development of color was light-intensity dependent, approaching saturation at 14.5 W·m-2 (at 13 C). No differences in fruit ripening were found between fruit that developed color under artificial light and red fruit from the commercial harvest, in spite of some stimulation of ethylene production during illumination.
Joshua D. Klein, Susan Lurie, and Ruth Ben-Arie
`Anna' and `Granny Smith' apples (Malus domestics Borkh.) that were held at 38C for 4 days before storage at 0C not only were firmer than controls upon removal from storage, but also softened more slowly during shelf life at 17C. Skin yellowing and loss of acidity attendant upon the heat treatment were not prevented by dipping fruit in 2% CaCl2 before heating. Both heat-treated and control fruit softened at the same rate upon exposure to ethylene at 100 μl·liter-1 upon removal from storage. The insoluble pectin content of cortical tissues was higher in heat-treated fruit than in controls after 10 days at 17C, while soluble pectin levels were lower. Arabinose and xylose levels were lower in cell walls from heat-treated cortical tissue, but the treatment had no effect on loss of galactose residues during shelf life.
Hong-Wei Zhou, Lilian Sonego, Ruth Ben-Arie, and Susan Lurie
Harvested nectarine fruit [Prunus persica (L.) Batsch `Flavortop'] were held for 5 days at 20 °C, or stored at 0 °C either immediately (control), or after 2 days at 20 °C (delayed-cooling). Observations were conducted after removal from storage for 1, 3, or 5 weeks and a shelf life of 5 additional days at 20 °C. After 5 weeks storage, 87% of control fruit developed woolliness (mealiness in texture accompanied by dry tasting fruit as a result of reduced juice content), while only 7% of delayed-cooling fruit showed signs of woolliness. Firmness of fruit in the delayed-cooling treatment was less at the beginning of ripening than control fruit, but after shelf life in both treatments, fruit reached the same final softness. Expressible juice was lower in woolly fruit (46%) than in healthy fruit (65%). Along with woolliness, viscosity of the resuspended alcohol insoluble residue (cell wall material) of expressed juice increased, implying accumulation of large molecular-weight polymers. The high performance liquid chromatography profile confirmed there were more large pectin polymers (2000 to 76 Ku) in the cell wall components of juice from woolly fruit and a lower arabinose content in these polymers reflected greater side chain removal from pectins in the juice of woolly fruit. Accumulation of larger sized pectin polymers along with high viscosity correlated with lower polygalacturonase activity in woolly fruit. Degradation of soluble pectin released into the juice of woolly fruit may have been impeded by repressed polygalacturonase activity.
Susan Lurie, Joshua D. Klein, and Ruth Ben Arie
A prestorage heat treatment of 38C for 4 days applied to `Granny Smith' apples (Malus domestics Borkh.) before regular air storage at 0C inhibited the development of superficial scald. Heat-treated apples stored for 3 months had superficial scald levels similar to diphenylamine (DPA)-dipped apples, while all nontreated control apples had scald. After 5 or 6 months of storage, this inhibition of scald development by prestorage heat treatment declined. The prestorage heat treatment inhibited the accumulation of α-farnesene and conjugated trienes in apple cuticle during storage, while DPA inhibited only α-farnesene oxidation. This treatment may be a substitute for chemical treatments against scald not only for short-term storage of `Granny Smith' but possibly also for other scald-susceptible apple cultivars.
Hong-Wei Zhou, Lilian Sonego, Andrai Khalchitski, Ruth Ben-Arie, Amnon Lers, and Susan Lurie
Most `Flavortop' nectarines [Prunus persica (L.) Batsch (Nectarine Group)] that were placed directly into 0 °C storage developed chilling injury after removal, while preconditioning fruit for 2 days at 20 °C (delayed storage) reduced chilling injury substantially. Chilling injury was expressed as the development of a dry, woolly flesh texture during ripening. Delayed-storage fruit were as firm as control fruit when placed in storage, but softened more during storage. Analysis of cell wall components showed that in woolly fruit a higher percentage of pectin was retained in the sodium carbonate fraction, although during ripening polymers in this fraction decreased in molecular mass (Mr). In the guanidine thiocyanate hemicellulose fraction of woolly fruit, the associated pectin and hemicellulose remained as large polymers, while in delayed-storage fruit they decreased in Mr during ripening. Endo-polygalacturonase (PG), pectin esterase (PE), and endo-glucanase (EGase) activities of delayed-storage fruit were the same as control fruit at the beginning of storage, although exo-PG was higher. However, differences were observed at the end of storage. Endo-PG activity was lower in control than delayed-storage fruit at the end of storage while PE activity was higher, and exo-PG and EGase activities were similar. These differences in activity were not reflected in the mRNA abundance of the respective enzymes. Endo-PG and PE message was similar in all fruit at the end of storage and increased during ripening, while EGase message was low at all times except in control fruit after storage and development of woolliness. Prevention of chilling injury by delayed storage appears to be due to the ability of the fruit to continue a progressive, slow cell wall degradation in storage which allows normal ripening to proceed when the fruit are rewarmed. Regulation of the softening process did not appear to be by enzyme synthesis, since mRNA levels of the enzymes did not correspond with enzyme activity.