Post-storage Ripening Research Articles

1-Methylcyclopropene Preharvest Application and Its Effect on Storability of ‘Comice’ and ‘Bosc’ Pears

Sprayable formulation of 1-methylcyclopropene (1-MCP) was tested as a preharvest application on European pears to determine the best timing and rate of 1-MCP application for maintaining fruit firmness and quality of trees during harvest and in storage after harvest. Two rates of 1-MCP, 0.06 and 0.13 g⋅L−1 active ingredient (a.i.) (minimum and maximum rates, respectively), were sprayed 1 week and 2 weeks before commercial harvest on two cultivars, Bosc and Comice, in 2017 and 2018. After 2 months in cold storage (0 ± 1 °C), differences in fruit firmness of both cultivars were observed among treatments. For ‘Bosc’, fruit treated with both rates 1 week before harvest were 50% firmer than nontreated control fruit. For ‘Comice’, fruit treated with the maximum rate both 2 weeks and 1 week before commercial harvest were 46% and 31% firmer than nontreated control fruit, respectively. However, after 4 months in storage, no differences in fruit firmness of both ‘Bosc’ and ‘Comice’ were observed among treatments. The sprayable 1-MCP application applied 2 weeks before commercial harvest also affected the fruit firmness on trees. The maximum rate of 1-MCP treatment consistently maintained the fruit firmness by 5.0 N compared with fruit treated with the minimum rate and nontreated controls. This effect was significant until 1 week after commercial harvest for both cultivars and until 2 weeks after commercial harvest for ‘Bosc’. The poststorage fruit firmness and overall eating quality of ‘Bosc’ were unaffected by the maximum rate of 1-MCP application as well as the extended harvest time. However, for ‘Comice’, the overall eating quality was negatively impacted by 1-MCP treatments. This study suggests that the maximum rate (0.13 g⋅L−1 a.i.) of 1-MCP application 2 weeks before commercial harvest maintains the fruit firmness of ‘Bosc’ for at least 2 weeks more and offers an extended harvest window for better preharvest management. Furthermore, this treatment improves the physiological fruit quality such as senescence scald during the poststorage period without significantly affecting the poststorage ripening of ‘Bosc’ after 4 months of storage.

Metabolism and cold chain performance of ‘Chuhwangbae’ Asian pears as impacted by 1-MCP treatment

The ‘Chuhwangbae’ Asian pear, a late-season cultivar that has become popular in Korea, is susceptible to physiological disorders during cold storage. The objective of this study was to evaluate the effect of 1-methylcyclopropene (1-MCP) treatment on fruit quality, physiological disorders, and targeted metabolites of ‘Chuhwangbae’ Asian pear fruit during cold storage and at the post-storage ripening stage. ‘Chuhwangbae’ Asian pear fruit were treated with 1-MCP immediately following harvest, stored at 1 °C for up to 3 months, and subsequently stored at 25 °C for 14 d to ripen. Indicators of fruit quality, namely the incidence of browning disorder and the degree of water loss or “shriveling,” as well as levels of key metabolites, were repeatedly analyzed during the simulated cold chain. Fruit treated with 1-MCP lost more weight but slightly maintained firmness than did untreated fruit during the entire cold chain. Treatment with 1-MCP reduced the severity of flesh browning but enhanced the incidence and severity of shriveling during post-storage ripening after 3 months of cold storage. GABA, histidine, phenylalanine, and tyrosine levels were higher in the flesh of the 1-MCP-treated fruit than in untreated fruit. The results indicate that the overall changes in metabolite levels following 1-MCP treatment were less during cold storage than those during post-storage ripening. Therefore, postharvest 1-MCP treatment could be at least partially effective in retaining flesh firmness and reducing the severity of internal browning of ‘Chuhwangbae’ Asian pears during the entire cold chain.

Pre-storage application of 1-methylcyclopropene does not affect the flavour of ‘Conference’ pears ripened after 8 months of commercial-standard controlled atmosphere storage

Postharvest 1-methylcyclopropene (1-MCP) applications are commercially used on ‘Conference’ pears to obtain an improved fruit quality after storage for up to 11 months. Treatment with 1-MCP may result in firmer and greener fruit at the end of storage. During subsequent shelf life, 1-MCP treated pears may show slower ripening, including a reduced rate of softening and a reduced production of aroma volatiles. The lower levels of aroma volatiles and consumer complaints of reduced flavour suggest that flavour is negatively affected by 1-MCP treatments, which has raised concern within in the Dutch fruit industry.In the present study, the effect of pre-storage 1-MCP treatment on post-storage ripening and flavour perception was studied. Untreated and 1-MCP-treated pears (325 nL L−1) were stored for 8 months at -0.8 °C under controlled atmosphere conditions of 3 kPa O2 and 0.6 kPa CO2 according to commercially used protocols. At day 7 and 9 of the subsequent shelf life at 10 °C, 1-MCP-treated fruit showed decreased yellowing and ethylene production, whereas firmness was similar to that of untreated fruit. The production of aroma volatiles was significantly reduced in 1-MCP-treated fruit; this was especially observed for different acetate esters, ethanol and butanol. Despite the reduction in aroma volatiles, a consumer panel could not distinguish (in a Tetrad test) between samples from untreated and 1-MCP-treated fruit with similar firmness. This indicates that the important aroma volatiles, although reduced in abundance, were still above threshold levels and did not affect overall flavour perception. We conclude that 1-MCP does not affect flavour when pears within equal firmness classes are compared.

Responses of ‘Rocha’ pear to delayed controlled atmosphere storage depend on oxygen partial pressure

Internal disorders hinder long-term controlled atmosphere (CA) storage of ‘Rocha’ pear. The delayed establishment of CA regime is often recommended to reduce internal disorders in pear. This investigation evaluated the effect of delayed CA at two oxygen partial pressures (pO2) at constant low CO2 partial pressure (pCO2) on internal disorders and on storage potential of ‘Rocha’ pear. Fruit were stored at −0.5°C for 257 d under 0.6kPa CO2 combined with 0.5 or 3.0kPa O2. The pull down of pO2 was imposed at the beginning of cold storage (immediate CA) or after 46 d (delayed CA). ‘Rocha’ pear tolerated immediate storage at 0.5kPa O2 without developing internal disorders for 257 d storage. However, 63.3% of fruit immediately stored at 3.0kPa O2 developed internal disorders. Delayed pull down of pO2 for 46 d reduced internal disorders in fruit at 3.0kPa O2 to 35.5%, but increased the disorder incidence in fruit at 0.5kPa O2 to 27.3%. Poststorage ethylene production rate was lower in fruit stored under delayed CA at 3.0 and 0.5kPa O2. In conclusion, the immediate storage of ‘Rocha’ pear at 0.5kPa O2 prevented the development of internal disorders for 257 d, while allowing adequate poststorage ripening and maintenance of quality traits. The effect of delayed CA on internal disorders depended on pO2. Delaying CA for 46 d did not benefit ‘Rocha’ pear during long-term storage.

EFFECTS OF CONTROLLED ATMOSPHERE COLD STORAGE ON WOOLLINESS AND PECTIC ENZYME ACTIVITY IN 'DOURADÃO' PEACHES

The high incidence of woolliness is one of the main causes that reduce 'Douradao' peaches quality, during long term cold storage. Experiments were performed to study the effects of controlled atmosphere (CA) cold storage (1±1°C and 90±5% UR) on the postharvest preservation, the occurrence of woolliness and the activities of pectic enzymes. The following CA conditions were tested: CA1 -3,0% CO 2 + 1,5% O 2 ; CA2 - 5,0% CO 2 + 1,5%O 2 ; CA3 - 10,0% CO 2 + 1,5% O 2 ; CONTROL - 0,03% CO 2 + 21,0% O 2 . The experiment design was entirely randomized with 3 replications of 10 fruits. After 14, 21 and 28 days of cold storage the samples of peaches were withdrawn from CA and kept in air at 25±1°C for 2, 4 and 6 days, being evaluated for weight loss, pulp firmness, woolliness index, soluble solids content (SS), titratable acidity (TA), exo-polygalacturonase (exo-PG), endopolygalacturonase (endo-PG) and pectin methylesterase (PME). The results showed that CA reduced weight loss and had a little effect on SS and TA. The CA modified the activities of the three enzymes. The induction of exo-PG and endo-PG activity and the repression of PME activity reduced the occurrence of woolliness. The fruits from CA2 treatment maintained good quality for 4 weeks; PME activity was reduced and the activities of exo-PG and endo-PG, which were low after cold storage, effectively increased at the 4 th day post-storage ripening. The control fruits maintained good quality less than 14 days.

α-Farnesene, conjugated trienols, and superficial scald in ‘Rocha’ pear as affected by 1-methylcyclopropene and diphenylamine

Diphenylamine (DPA) has been used for decades to prevent superficial scald, but the presence of DPA residues and the need for safer fruit warrant the search for alternative strategies to control superficial scald. The effect of DPA and 1-methylcyclopropene (1-MCP) on the levels of α-farnesene and conjugated trienols was examined in ‘Rocha’ pear in relation to the development of superficial scald. Fruit were harvested at three maturity stages and stored at 0 °C in air or in 2.5 kPa O 2 + 0.7 kPa CO 2. At 0.5 and 1.0 μl l −1, 1-MCP strongly reduced α-farnesene and conjugated trienols accumulation during storage. α-Farnesene levels in fruit treated with 1-MCP at 0.1 μl l −1 did not significantly differ from those in untreated controls in fruit from the early and normal harvest dates, but were lower in late harvested fruit. At 0.1 μl l −1, 1-MCP reduced the levels of conjugated trienols in comparison with untreated controls, but the effect was not as pronounced as with 0.5 or 1.0 μl l −1 of 1-MCP. α-Farnesene levels in fruit treated with DPA were similar to or higher than those in untreated controls throughout the storage period, but the conjugated trienols resulting from the oxidation of α-farnesene were reduced by DPA treatment. 1-MCP was very effective in reducing scald. 1-MCP at 0.1 μl l −1 was as effective as DPA in reducing scald, and had no effect on fruit ripening after a 4-month storage period. At 0.5 or 1.0 μl l −1, 1-MCP nearly eliminated superficial scald and also delayed post-storage ripening. We conclude that 1-MCP can be used to replace DPA as a postharvest treatment to control scald in ‘Rocha’ pear, although ripening after storage is delayed by relatively high concentrations.

Inhibition of ethylene-induced α-farnesene synthase gene Pc AFS1 expression in ‘d’Anjou’ pears with 1-MCP reduces synthesis and oxidation of α-farnesene and delays development of superficial scald

Pre-storage treatment of superficial scald-susceptible apple and pear fruits with the blocker of ethylene action 1-methylcyclopropene (1-MCP) inhibits the synthesis of α-farnesene. Consequently, accumulation of α-farnesene and its conjugated trienol (CTol) oxidation products in the fruit skin is diminished, and scald is largely prevented. In cold-stored apple fruit, a marked increase in expression of AFS1, the gene encoding α-farnesene synthase (AFS), precedes the rapid accumulation of α-farnesene. A Pyrus communis L. gene encoding AFS (Pc AFS1) was cloned using RT-PCR with primers based on apple AFS1 and RNA from peel tissue of ‘d’Anjou’ pears cold-stored for 33–94 days. Non-treated control and 1-MCP-treated (300 nL L −1 for 6 h at 1 °C) pears were stored at −1 °C in air for up to 216 days. Pc AFS1 expression in control fruit increased sharply over the first 63 days, remained high through 123 days, fell to much lower levels from 157 to 183 days, then increased again to maximum levels at 216 days. In comparison, expression of Pc AFS1 was attenuated in 1-MCP-treated fruit. Pc AFS1 transcript was almost nil through 94 days, rose sharply at 123 days and reached a maximum at 183 days that was two-fold lower than the highest level in controls. Maximum concentrations of α-farnesene and CTols in control fruit occurred at 94 and 123 days, respectively, and scald incidence was 100% after 94 days. α-Farnesene and CTol levels at these time points were, respectively, 9- and 19-fold lower in 1-MCP-treated fruit, which had no scald at 157 days, 13% at 183 days and 40% at 216 days. Post-storage ripening, with the associated increases in softening, respiration and ethylene production, was fully enabled in control fruit after 63 days at −1 °C, whereas 1-MCP-treated pears failed to ripen properly even after 216 days.

Cold Storage Effects on Pawpaw Fruit Ripening and Quality

Pawpaw [Asimina triloba (L.) Dunal] has significant potential as a new fruit crop. During ripening, loss of firmness is extremely rapid, and this trait may be the biggest obstacle to the development of a broader market. Cold storage of pawpaw fruit seems limited to 4 weeks at 4 °C, though fruit softening merely slows during storage. A study of several cultivars with commercial appeal has shown that none have superior cold storage life. Extending the cold storage beyond 4 weeks resulted in increasing loss of fruit firmness, poor poststorage ripening, and development of quality traits, and many fruit exhibiting flesh and peel discoloration. Cold storage duration affected fruit volatile production. By 4 weeks of cold storage, ethyl hexanoate and ethyl octanoate were the major volatiles produced, replacing methyl hexanoate, which was the major volatile produced by ripe fruit after harvest. By 8 weeks of cold storage, volatile ester production was generally low and ethyl hexanoate became the only major volatile. This loss of volatile production was accompanied by a decrease in alcohol acetyl transferase activity. Also, during cold storage, there was an increase in total phenolic content, lipid peroxidation products, and polyphenol oxidase activity. These changes may contribute to the black discoloration that developed in fruit cold-stored for 8 weeks or more. It is apparent that cold storage alone may not be sufficient to extend the storage life of most, if not all, current pawpaw cultivars beyond 4 weeks.

Salicylic Acid, Ethephon, and Methyl Jasmonate Enhance Ester Regeneration in 1-MCP-Treated Apple Fruit after Long-Term Cold Storage

Volatile esters, primarily synthesized in peel tissues, are major aromatic components of apple fruits [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.]. The use of cold storage combined with 1-methylcyclopropene (1-MCP) treatment prolongs the life of apples but represses the regeneration of esters during poststorage ripening. In this study, the regeneration of total esters was significantly increased in apple fruits treated with salicylic acid (SA) and Ethephon (ETH) that had been treated once or twice with 1-MCP. However, methyl jasmonate (MeJA) treatment resulted in regeneration of total esters after a single 1-MCP treatment. To determine the mechanism by which SA, ETH, and MeJA regulate ester regeneration, the apple alcohol acyltransferase gene (MdAAT2) was investigated at the mRNA, protein, and enzyme activity levels. Genes associated with ethylene perception were also investigated by RT-PCR. The results suggest that MdAAT2 controls ester regeneration and that MdETR1 plays a key role in ethylene perception and regulation of downstream MdAAT2 gene expression during poststorage. Ester compounds and concentrations differed in peels treated with different signal molecules, indicating that regulation of the pathway upstream of straight-chain ester biosynthesis depended on the regulation of lipoxygenase (LOX) and alcohol dehydrogenase (ADH) activity by SA, ETH, and MeJA during poststorage ripening.

Influence of Ethylene Action, Storage Atmosphere, and Storage Duration on Diphenylamine and Diphenylamine Derivative Content of Granny Smith Apple Peel

The application of diphenylamine (DPA) to prevent the apple peel disorder superficial scald can result in accumulation of a number of DPA derivatives resulting from C-nitration, C-hydroxylation, O-methylation, and N-nitrosation during fruit storage. As the presence of these compounds may be indicative of metabolic processes leading to superficial scald development, the contents of DPA and DPA derivatives were determined in fruits treated at harvest with DPA or DPA plus the ethylene action inhibitor 1-methylcyclopropene (1-MCP), which also prevents scald development. Influences of fruit maturity, storage environment, storage duration, and a 14 day poststorage ripening period on accumulation of DPA metabolites were also assessed. Poststorage ripening, 1-MCP treatment, and controlled atmosphere storage had varied effects on DPA derivative contents suggesting that reactive oxygen and nitrogen species, such as *OH, *NO, and *NO2, or enzyme-catalyzed reactions may be present during certain ripening and senescence-related physiological processes. Definitive correlations between superficial scald incidence and contents of specific derivatives were not observed.

Influence of 1-Methylcyclopropene and Storage Atmosphere on Changes in Volatile Compounds and Fruit Quality of Conference Pears

Conference pears (Pyrus communis L.) were treated with 25 and 50 nL L(-1) 1-methylcyclopropene (1-MCP) at -0.5 degrees C for 24 h, then stored for up to 22 weeks in air (NA) and controlled atmosphere (CA). After 7 and 14 weeks of storage, fruits were retreated with 1-MCP. After 7, 14, and 22 weeks of storage, fruits were kept for up to 7 days at 20 degrees C in air for poststorage ripening. The effects of 1-MCP treatment declined with duration of storage in both storage atmospheres, indicating that retreatments had little additional effects on subsequent ripening. Ethylene production was lower and firmness was higher in 50 nL L(-1) fruits, while the 25 nL L(-1) dose was not very different from the control. Development of superficial scald was not prevented by 1-MCP treatments, but the severity of the symptoms was influenced. The 1-MCP effects were perceivable on texture (juiciness) and flavor. Control fruit and 25 nL L(-1) fruit reached their best sensory quality after 14 weeks of storage, while 50 nL L(-1) fruit reached the same sensory quality later, keeping a fresh flavor when the quality of control fruit declined and became watery or grainy. The fresh flavor in 50 nL L(-1) fruit was probably due to the presence below the odor detection threshold concentrations of the volatile compounds responsible for the "ripe pear" aroma, mainly of butanol and ethyl butanoate. CA prolonged or enhanced the effects of 1-MCP; 1-MCP cannot substitute for CA but can reinforce the CA effects.

Diphenylamine and Diphenylamine Derivative Content of `Granny Smith' Peel: Influence of Ethylene Action and Regular or Controlled Atmosphere Storage Duration

Diphenylamine (DPA) is used for superficial scald control in apple fruit. A number of DPA derivatives resulting from C-nitration, C-hydroxylation, O-methylation, and N-nitrosation can be present in DPA-treated apple fruit after storage. The presence of the compounds may be indicative of metabolic processes that lead to scald development. Therefore, apple peel DPA and DPA derivative content in fruit treated at harvest with DPA or DPA plus 1-methylcyclopropene (1-MCP) was assayed upon removal of fruit from controlled atmosphere (CA) and regular atmosphere (RA) storage and during a 14-d post-storage ripening period. Apples were also treated at harvest with different concentrations of DPA and assayed after 6 months CA storage to confirm recovery of DPA and DPA derivatives is linear over a wide concentration range. Harvest maturity notably affected peel DPA and 4-hydroxydiphenylamine (4OHDPA) content. Post-storage ripening, 1-MCP treatment, and CA storage had varied affects on DPA derivative content, suggesting reactive oxygen or nitrogen species, such as •OH, •NO, and •NO2, or enzyme catalyzed reactions may be generated during ripening and senescence related physiological processes. Consistent correlations between scald incidence and content of specific derivatives were not observed.

VOLATILE PRODUCTION IN ´FUJI´ APPLES STORED UNDER DIFFERENT ATMOSPHERES MEASURED BY HEADSPACE/GAS CHROMATOGRAPHY AND ELECTRONIC NOSE

Volatile production, sensory acceptability and electronic nose responses were measured in 'Fuji' apples (Malus x domestica Borkh.) to evaluate the effects of different storage conditions, storage periods and days of shelf life. Apples harvested at 185 days after full bloom were analysed after 5 and 7 months of cold storage in normal atmosphere (AIR: 21% O 2 + 0.03% CO 2 ) and in two controlled atmospheres (CA: 1% O 2 + 2% CO 2 and 3% O 2 + 2% CO 2 ). During post-storage ripening, apples were kept at 20°C for 1, 5 and 10 days before analytical and sensory measurements were made. Volatile production was measured by means of headspace/gas chromatography and electronic nose and the acceptability of apples by a semi-trained panel. Sensor responses registered by 21 different metal oxide sensors of an electronic nose (EN) were used to classify apples using Principal Component Analysis (PCA). The PCA model containing data from all fruits (at-harvest and after storage) showed that it was possible to identify fruits recently harvested and under different storage conditions. Principal components 1 (PC1) and 2 (PC2) accounted for 63 and 30% of the total variability respectively. On the other hand, a PCA involving volatile production, sensory acceptability and EN signals corresponding to all fruits allowed a better differentiation between fruits stored at 1% O 2 + 2% CO 2 and 3% O 2 + 2% CO 2 , with an explained variance of 58% (two first PCs).

RELATIONSHIPS BETWEEN SENSORY AND INSTRUMENTAL QUALITY CHARACTERISTICS OF ´FUJI´ APPLES BY MULTIVARIATE ANALYSIS

Standard quality parameters and sensory characteristics (sensory acceptability and sensory acidity) of 'Fuji' apples (Malus x domestica Borkh.) were studied in relation to storage conditions, storage duration and shelf life period. 'Fuji' apples harvested at 185 days after full bloom were analysed after 3, 5, and 7 months of cold storage in normal atmosphere (AIR: 21% O 2 + 0.03% CO 2 ) or under three different controlled atmospheres (CA), in which oxygen and carbon dioxide were held at 1% + 1% (ULO1), 2% + 2% (LO) or 1% + 3% (ULO2), respectively. During post-storage ripening, apples were kept at 20°C for 1, 5 and 10 days before analytical measurements were made.Partial least squares regression models (PLS1) were run, in an attempt to correlate sensory acceptability and sensory acidity to instrumental measurements (SSC, TA, firmness and Hue). PLS1 model for sensory acceptability, where the instrumental quality parameters were used as X-variables, showed that the quality parameters most positively influencing acceptability were SSC, TA, firmness and background colour (Hue). The predicted sensory acidity versus the measured sensory acidity plot from the PLS1 model developed for sensory acidity revealed three groups defined by sensory acidity with a correlation coefficient of r= 0.94. Thus, ULO1-stored fruit had the highest sensory acidity score, ULO2- and LO-stored fruit showed intermediate sensory acidity score, and finally AIR-stored apples had the lowest sensory acidity score.

1-Methylcyclopropene plus high CO2 applied after storage reduces ethylene production and enhances shelf life of Gala apples

The effect of a combined treatment comprising a 35% CO2 atmosphere plus 250 nL L-1 1-methylcyclopropene (1-MCP) on shelf life of Gala apples app lied after removal from air or controlled atmosphere (CA) storage was evaluated. Fruit were removed from air storage at 10 and 18 wk and from CA storage at 18 and 22 wk, warmed to 20°C and then treated for 16 h with 1-MCP either in combination with or without 35% CO2. Treated fruit were held at 20°C in air for up to 15 d and assessed every 5 d. Onset of ethylene production was delayed and quality retention was only marginally improved with the 1-MCP treatment. In contrast, both were significantly affected when a 35% CO2 atmosphere was applied in combination with the 1-MCP treatment. Fruit that were treated with 1-MCP in a 35% CO2 atmosphere exhibited the lowest levels of internal ethylene concentration (IEC) and the smallest decline of flesh firmness and titratable acidity (TA) during holding at 20°C. No symptoms of CO2 injury were noted. In the high CO2 atmosphere, a 250 nL L-1 treatment with 1-MCP resulted in similar firmness and titratable acidity retention at room temperature as did a 1000 nL L-1 treatment with 1-MCP. Additionally, the application of the combined 1-MCP/high CO2 treatment after holding at 20°C for 24 h resulted in similar effects as seen if the treatment were applied only 2 h after removal from storage. Biochemical analysis showed that 1-MCP and high CO2 have two distinctly different effects on ACC-synthase activity, explaining the synergistic effect of the combined treatment. Key words: Post-storage ripening, 1-MCP, carbon dioxide, ethylene biosynthesis

Ethylene involvement in the cold storage disorder of ‘Flavortop’ nectarine

‘Flavortop’ nectarine was either held at 20°C for ripening or stored at 0°C for 30 days after treatment with 0.1 ppm 1-methylcyclopropene (MCP) at harvest. Half of the untreated fruits were exposed to 15 ppm ethylene during storage. Fruit softening was retarded by MCP both without storage or after storage but not affected by ethylene treatment during storage. Fruits treated with MCP developed severe flesh woolliness and reddening and had lower expressible juice compared to the ethylene treatment. Ethylene production of the fruits following treatment was not affected by MCP but was inhibited after storage while it was enhanced by exogenous ethylene. mRNA abundance of ACC oxidase (ACO), polygalacturonase (PG) and pectin esterase (PE) during storage was also inhibited by MCP, and ACO and PG expression was furthermore inhibited after post-storage ripening. Ethylene-treated fruits had higher message levels of ACC synthase (ACS) and PE than control fruit following storage while ACO levels were higher in control fruit and PG was similar in both. The accumulation of endogluconase (EGase) mRNA was enhanced by MCP at all stages while inhibited by ethylene after post-storage ripening. The data suggest that a certain level of ethylene production is essential for normal ripening of nectarines after cold storage. Exogenous ethylene during storage enhanced ethylene production after storage, thereby promoting the sequence of cell wall hydrolysis necessary for normal ripening. MCP blocked the ethylene action and inhibited its synthesis after cold storage, subsequently leading to abnormal softening and the occurrence of severe disorders.

Influence of Nitrogen and Bagging on Fruit Quality and Mineral Concentrations of `BC-2 Fuji' Apple

The influence of three rates of nitrogen (N) and fruit bagging on fruit peel and flesh mineral concentrations and fruit quality in `BC-2 Fuji' apple (Malus domestica Borkh.) trees on Malling 9 (M.9) was studied. Increasing N application decreased fruit peel red color, fruit N, iron (Fe), and manganese (Mn). Fruit from trees receiving 10.72 oz (303.9 g) N per year had higher evolved ethylene and respiration during poststorage ripening tests. Bagging of fruit reduced fruit peel red color, soluble solids concentrations (SSC), and dry weight as compared to nonbagged fruit. Bagged fruit had higher N, potassium (K), and copper (Cu) than nonbagged fruit. Fruit peel had a greater percentage of dry weight, and higher concentrations of all tested minerals compared to fruit flesh.

Juice characteristics related to woolliness and ripening during postharvest storage of peaches

The effect of up to three cycles of intermittent warming (IW) for one day at 20 °C every 6 days of storage at 0.5 °C on the development of woolliness and on the changes in juice characteristics during post-storage ripening of "Paraguayo" peaches at two ripening stages was studied. By subjecting the peaches to IW, woolliness was strongly reduced concomitantly with a sudden reduction in flesh firmness due to normal fruit ripening. During post-storage ripening, extractable juice and juiciness only decreased in conventionally stored (CS) fruit as a result of woolliness. However, the liquid phase of the juice extracted (clear juice) decreased in IW but not in woolly CS fruit. Clear juice reduction appeared to be related to normal advanced ripening, with differences between woolly and sound fruit associated with the ripening stage during storage. The technological and physiological implications of these quality indices, mainly related to ripening, senescence, and woolliness, are discussed. These results support the hypothesis that IW maintains cellular membrane integrity and helps the recovery of pectolytic enzymatic activity. It has been stated that the incidence of woolliness was more closely related to the juice release mechanism than to the clear juice content.

Quality and Shelf Life of Tomatoes Improved by Intermittent Warming

Breaker tomatoes of the long life cultivar ‘Daniela F-1’ Hazera (Lycopersicon esculentum Mill) treated with 1 g/L iprodione, were stored at 6, 9 and 12 °C, and 90–95% RH for 14 and 21 d. Fruit stored at 6 and 9 °C was exposed to intermittent warming at 20 °C for one day, at 7-d intervals. Fruit was then allowed to ripen for a period of 3 d at 20 °C and 75–80% RH. In comparison to continuous storage at 6 or 9 °C, intermittent warming during two or three cycles of 6 d at 6 or 9 °C and 1 d at 20 °C, enhanced the surface colour and encouraged ripening. At the end of cold storage and after post-storage ripening, there was no significant change in the soluble solids content. A slight reduction in titratable acidity was induced by intermittent warming. After ripening, the best results were obtained by intermittent warming during three cycles of 6 d at 9 °C and 1 d at 20 °C. Continuous storage at 12 °C also yielded good results. Both treatments resulted in fruits of acceptable quality and shelf life for commercial purposes. Similar results have already been reported for conventional tomato hybrid plants, indicating that the physiological behaviour of both cultivars were similar under similar intermittent storage temperatures.

Physiological changes in peaches related to chilling injury and ripening

Firm-breaker (FB) and firm-mature (FM) peaches cv. ‘Paraguayo’ were either stored for 4 weeks at 2°C or subjected to three cycles of 1 day of intermittent warming (IW) at 20°C every 6 days at 2°C. Normal postharvest ripening and post-storage ripening at 20°C were also studied in order to relate postharvest physiology with the onset of chilling injuries (CI) (woolliness, gel breakdown and scald). As far as we know, both gel breakdown and scald have been described and reported on peaches for the first time. FB peaches were more sensitive to CI than FM ones. A high respiration rate and ethylene production in conventionally stored fruit after 2 weeks of storage, followed by a drop in ethylene production, was accompanied by the development of CI in fruit of both maturity stages. IW strongly reduced CI during storage. Periodic warming acclimatised chilled fruit to subsequent periods of chilling by allowing them to ripen due to the production of a suitable amount of ethylene, depending on their maturity stage at harvest. The increase in ethylene production during post-storage ripening could be related to the development of over-ripeness.