Quality and shelf life of mango (Mangifera indica L.) fruit: As affected by cooling at harvest time

Mango fruit has high nutritional values, nice flavor, taste, etc. and hence is known as king of fruits. However, it faces number of challenges such as attack of microorganisms, having short shelf life, mismanagement during transportation and storage. Therefore, two varieties of Pakistani mango fruits namely, Langra and Sammar Bahisht Chaunsa, were harvested and endeavored to prolong the shelf life while keeping the quality up to the requirement. For the purpose, the mango fruit was harvested at hard green stage of maturity; it was cleaned and subjected to analysis for different parameters. The rest of the fruit was kept in water and/or in air, maintained at 15 °C, for different time periods and stored at 30 °C till ripening. The fruit was analyzed for different parameters at the time when the control was ripened and at the ripening stage of each sample. The results obtained were correlated with/the heat removed during the pre-storage treatment and was observed that the impact of these treatments upon the quality and shelf life of the fruit was significantly under the limit P ≤ 0.05. It was also observed that the heat removed as per treatment T₂ enhanced the quality of the fruit and prolonged the shelf life more than others.     

Addition of salicylic acid to nutrient solution combined with postharvest treatments (hot water,salicylic acid,and calcium dipping) improved postharvest fruit quality of strawberry

This experiment was conducted to study the effect of salicylic acid addition to nutrient solution and different postharvest treatments on fruit quality of strawberry cv. Camarosa after 7 days at 2 °C. Plants were irrigated with two complete nutrient solutions, with salicylic acid (0.03 mM) or without salicylic acid as the control. Fruits were then treated with eight different postharvest treatments (25 °C water, 45 °C water, 25 °C or 45 °C water containing CaCl₂ (1%), 25 °C or 45 °C water containing salicylic acid (2 mM) and 25 °C or 45 °C water containing both CaCl₂ (1%) and salicylic acid (2 mM)). Fruits which received SA in their nutrient solution had less weight loss and decay and higher firmness. All of the postharvest treatments improved fruit quality characteristics. Fruits dipped in salicylic acid solution had less weight loss, decay and a* (redness) and higher firmness and hue angle than control. Heat treated fruits had less decay and a* and higher hue angle than control. Fruits dipped in CaCl₂ solution had less weight loss, decay and a* and higher firmness than control. Combination of the three postharvest treatments improved firmness, decay, weight loss and vitamin C.     

Effect of exogenous putrescine on post-harvest life of strawberry (Fragaria ananassa Duch.) fruit,cultivar Selva

Effect of different concentrations of putrescine on post-harvest life of strawberry (Fragaria ananassa Duch.) fruit, cultivar Selva at 5 °C was studied. Fruits were immerged in 0.3, 0.5, 1 and 2 mM putrescine as well as distilled water (control) for 5 min, then transferred into the fridge (5 °C) together with untreated fruits (dry treatment). The rate of weight loss, ethylene production, flesh firmness, soluble solids content, titratable acidity and pH of fruits were determined 5, 9 and 13 days after the beginning of storage. Flesh firmness, appearance, color change and taste of fruits were also determined in the same intervals using a taste panel. Storage life of the strawberry fruits was significantly increased by the use of putrescine, so that the untreated and control fruits had 6 and 8 days storage life, respectively, while the immerged fruits in 1 and 2 mM putrescine were still suitable to be exposed in the market 12 and 14 days after the beginning of storage, respectively. No significant weight losses were observed in treated fruits compared to controls and dry treatment at all determination times. Ethylene production was decreased significantly by the use of putrescine. Untreated fruits (dry treatment) had the highest rate of ethylene production and the lowest rate was occurred in 2 mM putrescine treatment at all determination times (5, 9 and 13 days after the beginning of storage). The use of putrescine also prevented the softening of fruit flesh during the storage and kept their firmness, so that, the 2 mM putrescine treatment caused the highest fruit firmness at all determination times. Distilled water treatment (control) had the lowest fruit firmness 5 and 9 days after storage, while this occurred for the dry treatment 13 days after storage. Soluble solids content, pH and titratable acidity of the fruits were not significantly affected by the use of putrescine, but the highest and lowest rate of titratable acidity were related to the 2 mM putrescine and dry treatment, respectively, at the three determination times. Overall, the quality of fruits was improved by the use of 2 mM putrescine in terms of properties evaluated by the taste panel.     

Heat treatments and expansin gene expression in strawberry fruit

Heat treatments have been applied in fruit postharvest technology for insect disinfestations, decay control, ripening delay and modification of fruit responses to other stresses. Heat treatment affects several aspects of fruit ripening, such as ethylene production and cell wall degradation probably through changes in gene expression and protein synthesis. In this paper, strawberries (Fragaria × ananassa Duch., cv Camarosa) at 50–75% red stage of ripening were heat-treated at 45 °C during 3 h in an air oven and then stored at 20 °C for 0, 4, 18, 24 and 48 h. Fruit firmness was determined and the expression of a set of expansin genes (FaEXP1, FaEXP2, FaEXP4, FaEXP5 and FaEXP6) was analyzed. The firmness of treated fruit was higher than that of control fruit 24 h after treatment, though the differences disappeared after 48 h at 20 °C. The analysis by northern-blot indicated that heat treatments affected differently the expression of expansin genes. The expression of FaEXP1, FaEXP2 and FaEXP6 was lower in treated fruit during the following 24 h post-treatment. The lower expression of these expansin genes could contribute to delay softening after heat treatment.     

Physicochemical changes in Mazafati date fruits incubated in hot acetic acid for accelerated ripening to prevent diseases and decay

A method was developed and optimized for the accelerated ripening of date fruits of cultivar ‘Mazafati’ to prevent diseases and decay. The date fruits were incubated in hot acetic acid solution 0.5% at 40 + 1 °C for 72 h. During the process some physicochemical changes in the fruits were studied and were found to be comparable with the changes in the fruits that naturally ripened on the tree. Fruit firmness, water insoluble solid (WIS), protein, pH, L*a*b* and E decreased during accelerated ripening whereas in control samples at 4 °C increased. Total solid (TS), total soluble solid (TSS) and acidity were slightly higher in treated fruits compared to control fruits. The greatest loss of fruit firmness occurred during the first 12 h of incubation. Organoleptic tests also showed little difference between the naturally ripened fruits on trees and accelerated ripened fruits in hot acetic acid. Overall there was no difference between the fruits and were readily acceptable to consumers.     

A novel postharvest UV-C treatment to reduce chilling injury (membrane damage,browning and chlorophyll degradation) in banana peel

To investigate the mode of action of UV-C to alleviate CI in banana. Banana [Musa (AAA group), Cavendish subgroup cv. Cavendish] fruits were treated with UV-C at dosages of 0.03 kJ m⁻² prior to storage at 8 or 25 °C. UV-C treatment reduced both the incidence and severity of banana fruits stored under low temperature. UV-C treatment reduced membrane damage indicated by lower activity of lipoxygenase (LOX) and malondialdehyde (MDA) content. In additions, the in vitro polyphenol oxidase (PPO) activity was activated when fruits were stored at CI temperature and UV-C treatment could inhibit the PPO activity. UV-C treatment also delayed yellowing and chlorophyll (Chl) degradation due to the inhibition of chlorophyllase and chl-degrading peroxidase activities. Furthermore, the reduction of ethylene production and respiration rate by UV-C treatment results in extended postharvest shelf life of banana. These finding suggest that the loss of cellular compartments in consequence of membrane degradation, combined with the increase of PPO activity, might contribute to the development of CI in banana peel. UV-C treatment may play an important role in maintained membrane integrity and inhibited PPO activity, reducing the severity of CI symptom and delayed ripening in banana. This novel technique may offer an advance in postharvest handling of bananas and other chilling-sensitive commodities in order to reduce postharvest losses resulting from CI.     

Leaf pruning intensities at flowering of banana (Musa AAA,cv. Grande Naine) did not influence fruit green and yellow life and quality

This study examined the effects of leaf pruning intensities at flowering on the green and yellow life and fruit quality of bananas (Musa AAA, cv. Grande Naine). The fruit from banana plants that retained 7, 9, 11 and 13 leaves after pruning were packed in carton boxes of 13.7 kg and stored in a cold room at 14 °C for 21 days to simulate transportation conditions. During this period, eight visual evaluations of fruit peel colour were made. Next, fruits were induced to commercial ripening using ethylene at 100 μl/ml. Four evaluations (every 2 days) on fruit firmness, soluble solids, titratable acidity, fruit weight and peel colour were made to assess fruit yellow life. No interaction between evaluations and number of leaves retained was found for pulp firmness, soluble solid percentage, fruit acidity, fruit weight and maturation grade. The fruit green life and peel colour was similar for plants retaining different number of leaves. After the application of ethylene, there were no differences in fruit firmness (P > 0.62), percentage of soluble solids (P > 0.24) nor in the percentage of acidity (P > 0.32). No difference in fruit weight (P > 0.07) and ripening grade (P > 0.17) were observed among plants retaining different number of leaves. The results suggest that in tropical commercial banana plantations, producing for international markets, it is possible to defoliate the banana plants to seven leaves at flowering without causing a reduction on the green and yellow life and quality of fruit.     

Effect of high temperature stress on the reproductive growth of strawberry cvs. ‘Nyoho’ and ‘Toyonoka’

High temperatures are known to reduce fruit size and fruit weight in strawberry, but cultivar differences in the response to high temperature stress during the reproductive stage up to the second inflorescence have not been sufficiently reported. We examined the effect of two day/night temperature regimes on fruit set and fruit growth in two cultivars, ‘Nyoho’ and ‘Toyonoka’. A high day/night temperature of 30/25 °C reduced the number of inflorescences, flowers, and fruits in both cultivars compared with plants grown at 23/18 °C. The percentage of fruit set in ‘Nyoho’ was not significantly different between the two temperature treatments, while that in ‘Toyonoka’ was much lower at 30/25 °C than at 23/18 °C. Days to ripening was shorter at 30/25 °C than at 23/18 °C, and no cultivar differences were observed. Fresh weight of primary, secondary, and tertiary fruits was greater at 23/18 °C than at 30/25 °C in both cultivars, and no cultivar differences were observed, except in tertiary fruits. The diameter of fruits from all positions was also reduced at 30/25 °C in both cultivars. Relative growth rates of fruits showed two peaks in both cultivars and in both temperature treatments. Both peaks appeared earlier at 30/25 °C than at 23/18 °C. Percentage of fruit set at 30/25 °C in the second inflorescence was also significantly lower in ‘Toyonoka’ than in ‘Nyoho’. These results indicate that high temperature stress negatively affects the reproductive process in strawberry and that plant response to high temperature stress is cultivar-related in such responses.     

Post-harvest heat treatments modify cell wall composition of strawberry (Fragaria × ananassa Duch.) fruit

‘Pájaro’ strawberry fruit were treated at 45 °C by hot air or hot water prior to storage at 3 °C for 10 days. Control fruit were stored without treatment. Modifications in cell wall composition and fruit quality caused by heat treatment were assessed after removal of fruit from storage. Treatment with hot water improved fruit resistance to fungal infection, but caused external damage, which rendered fruit commercially unacceptable. Hot air treatment did not affect external appearance, improved resistance to fungal infection and preserved firmness. Heat treatments did not affect cell wall yields obtained, but caused alterations in solubility of the different cell wall polysaccharide fractions. Higher yields for CDTA- and KOH-soluble fractions were observed as a consequence of treatment, suggesting decreased solubilization of cell wall polymers in treated fruit, even though no apparent relationship to fruit firmness was found. Higher degrees of esterification as well as total sugar contents in both CDTA- and KOH-soluble fractions were also found in heated fruit.     

MaCDPK7, a calcium-dependent protein kinase gene from banana is involved in fruit ripening and temperature stress responses

Calcium-dependent protein kinase (CDPK) is an important Ca²⁺ sensor in plant development and responses to stress stimuli. Banana fruit is a typical climacteric- and chilling-sensitive fruit. The roles of CDPK genes in the ripening and chilling response of banana fruit are unclear. We isolated a cDNA fragment with full-length coding MaCDPK7 (HM061075) from fruit peel tissue. Induction of MaCDPK7 expression in fruit peel was observed 0.5 h after phytohormone ethylene treatment, earlier than the up-regulation of MaACO1 and MaACS1, coding a 1-aminocyclopropane-1-carboxylate oxidase and 1-aminocyclopropane-1-carboxylate synthase, respectively. Penetration of calcium signaling blockers, EGTA, or LaCl₃ inhibited the ripening and gene expression of MaCDPK7, MaACO1, and MaACS1 in the in vitro cultured peel pieces, but Ca²⁺ application removed the inhibitory effect of EGTA and LaCl₃. This suggested that MaCDPK7 might be a positive regulator involved in the calcium signaling in banana fruit ripening. Under temperature stresses, we found that MaCDPK7 gene expression increased 3 h after hot water dipping (HWD). The HWD-treated fruits exhibited markedly less chilling injury (CI) than control fruits in cold storage. Stored at 7°C (CI temperature) dramatically increased MaCDPK7 gene expression, while pre-treatment of HWD repressed the induction in cold storage. These results show that the MaCDPK7 gene is involved in regulating banana fruit ripening and chilling resistance induced by heat treatment.     

Putrescine and carnauba wax pretreatments alleviate chilling injury,enhance shelf life and preserve pomegranate fruit quality during cold storage

Keeping in mind to reduce chilling injury and retain quality; pomegranate (Punica granatum L., cv. Mridula) fruits were treated with putrescine, carnauba wax and putrescine + carnauba wax prior to cold storage at 2 °C. Before analyzing physical, physiological and biochemical parameters fruits were subjected to post cold storage exposure at 20 °C for 3 days. Untreated fruits developed rapidly chilling injury, with main symptoms being brown discolouration of the skin, surface pitting, weight and firmness loss during storage. All these undesirable changes were significantly delayed by putrescine + carnauba wax application. Respiration and ethylene evolution rate were also brought down by combined application of putrescine and carnauba wax treatment. The superiority of combine treatment over other applications seems arises due to additive benefit of antisenescence and barrier properties of putrescine and carnauba wax, respectively.     

Fractional changes of pectic polysaccharides in different tissue zones of developing guava (Psidium guajava L.) fruits

Cell-wall pectic polysaccharides were fractionated by sequential extraction with water, 1% potassium oxalate at room temperature, 0.05 M HCl at 100 °C and 0.05 M NaOH at 4 °C from the three specific tissue zones, i.e., outer pericarp (OP), middle pericarp (MP) and inner pericarp (IP) of the guava fruits during their development and ripening. The water and oxalate-soluble pectic fractions were found to increase, while acid and alkali-soluble pectic fractions had a decreasing trend at ripening phase of fruit, irrespective of the different tissue zones. However, the extent of pectic solubilization was more pronounced in IP region as compared to OP and MP zone of the fruit tissue. The differential degradation of pectic polymers thus points out that ripening as well as tissue softening of guava fruits are centrifugally expressed as evidenced by higher accumulation of sugar and soluble pectic polysaccharides in IP zone of the fruits.     

Grafting effects on postharvest ripening and quality of 1-methylcyclopropene-treated muskmelon fruit

In addition to managing soil-borne diseases in muskmelon (Cucumis melo L.) production, grafting with resistant rootstocks may impact fruit quality. The ethylene antagonist 1-methylcyclopropene (1-MCP) has been shown to extend shelf life of fresh muskmelon fruit. Postharvest characteristics of 1-MCP-treated melon fruit as affected by grafting, however, have not been well examined. This study was conducted to explore the influence of grafting with different rootstocks on ripening and quality attributes of 1-MCP-treated muskmelon fruit during postharvest storage. Grafted ‘Athena’ muskmelon with two commercial squash interspecific hybrid rootstocks including ‘Strong Tosa’ and ‘Tetsukabuto’ as well as non-grafted and self-grafted ‘Athena’ were grown in replicated field plots at the University of Florida Plant Science Research and Education Unit (Citra, FL, USA) during April–June 2010. Half-slip fruit from two harvests were treated with 1.0 μL L⁻¹ 1-MCP (18 h, 20 °C) and analyzed during storage at 13 °C. For fruit from the 27 May harvest, whole fruit and mesocarp firmness, titratable acidity, soluble solids, and ascorbic acid content were measured, while production of ethylene and CO₂ was determined on fruit from the 29 June harvest. Grafting did not show a significant impact on fruit yield but affected the fruit shelf life significantly. Fruit from non-grafted ‘Athena’ and ‘Athena’ grafted onto ‘Strong Tosa’ demonstrated a shelf life of 31 d for the first harvest and 22 d for the second harvest. Shelf life of fruit from self-grafted ‘Athena’ and ‘Athena’ grafted onto ‘Tetsukabuto’ declined by 6 d and 3 d for the first and second harvest, respectively. Whole fruit firmness decreased by approximately 15.5% on average from 13 to 31 d except day 19 as a result of grafting, but to a lesser extent with ‘Strong Tosa’ rootstock. Mesocarp firmness of grafted melon was reduced by about 30.2% at days 13 and 19 compared to non-grafted ‘Athena’ fruit. In contrast, titratable acidity, soluble solid content, and ascorbic acid concentration were less affected by grafting. All the measurements except for ethylene and CO₂ production declined during storage regardless of the grafting treatment. Compared with ‘Strong Tosa’ rootstock, ‘Tetsukabuto’ resulted in a more rapid ripening under 1-MCP application, as reflected by earlier increase in ethylene production and higher respiratory rate. The study demonstrates that grafting effects on postharvest ripening and quality of ‘Athena’ muskmelon can vary markedly with rootstocks used.     

Influence of harvest time and after-ripening on the seed quality of eggplant

Eggplant cv. Emi and Tsakoniki were cultivated for seed in an unheated greenhouse and fruits were harvested at 25–65 days after anthesis (DAA) in order to determine the optimum harvest time. In addition, the effect of after-ripening on seed quality (i.e. seed size and germination) was examined by storing harvested fruit at 25 °C for 20 days prior to seed extraction. From the results, it was concluded that the optimum time of harvest for seed production is 55 DAA. Seeds extracted from fruits that were harvested at 25–35 DAA did not germinate, but when fruits harvested at the same age were stored for 20 days at 25 °C prior to seed extraction (i.e. seeds were after-ripened) germination was induced. Seeds extracted from fruits harvested at 45 DAA showed a high percent germination, which decreased after storage at 25 °C for 3 months. This decrease, however, was reduced by after-ripening prior to extraction. It is concluded that although eggplant is a non-climacteric species and fruit do not ripen after harvest, nevertheless seeds within the fruit continue to fill and mature after harvest; hence storage of prematurely harvested fruit prior to seed extraction permits the seeds of these fruits to after-ripen in situ and thereby increases seed size and germination. The implication of this result for eggplant seed production is discussed.     

Heat treatment and harvest date interact in their effect on superficial scald of ‘Granny Smith’ apple

A study was made of the effect of hot water dips (HWD) at temperatures of 42, 44, 46 and 48 °C (HWD 42 °C, HWD 44 °C, HWD 46 °C and HWD 48 °C, respectively) for 3 min on development of superficial scald and the concentration of α-farnesene and conjugated trienols (CT), CT₂₅₉, CT₂₆₉, CT₂₈₁, as well as OD₂₀₀ on Granny Smith apple fruits harvested on three dates and stored 125 days in air at 2 °C. HWD 48 °C efficiently decreased surface scald in the second and third harvest. α-Farnesene and CT were measured spectrophotometrically and by HPLC. No clear relationship of OD₂₀₀ and scald development was observed. Correlation of scald index and OD₂₀₀ at the end of storage was negative for the second harvest date. There was no significant correlation between the scald index and CT₂₅₉. Scald index was positively correlated with CT₂₆₉ after 80 days for the second and third harvest and at the end of storage for the second harvest. CT₂₈₁ was spectrophotometrically detectable only at the end of the storage, for the third harvest date, in control, HWD 42 °C, and HWD 44 °C. HWD 42 °C had significantly higher CT₂₈₁ compared to HWD 44 °C and control. HPLC analysis of control samples revealed presence of CT₂₈₁ in all three harvest dates, and presence of at least two components, as was the case of CT₂₅₉ and CT₂₆₉. The ratio of these two components was different for all three CT species. Fruit maturity was an important factor determining the response of fruit to heat and occurrence of superficial scald. The results indicate that a successful treatment using HWD to control superficial scald may be obtained after further research and that there are still some questions on the role of different CT's in scald biochemistry that should be addressed in future research.     

Different mechanisms to obtain higher fruit growth rate in two cold-tolerant cucumber (Cucumis sativus L.) lines under low night temperature

One cold-sensitive cultivar (Jinyan 4) and two cold-tolerant inbred lines (NY-1 and XC-1) of cucumber (Cucumis sativus L.) were subjected to temperatures of 28 °C/22 °C (day/night, control) or 28 °C/12 °C (day/night, cold treatment) in a 10 h photoperiod (7:00–17:00). Under control conditions, cucumber fruits grew fast during afternoon and early night, and slow during late night and morning. Under 28 °C/12 °C conditions, the two cold-tolerant inbred lines maintained relatively higher fruit growth rates than the cold-sensitive cultivar by different mechanisms. Compared to Jinyan 4, NY-1 fruits had higher growth rates during cold nights while XC-1 fruits grew faster during the next day. Under the 28 °C/12 °C temperature regime, the assimilate accumulation in the fruits of all tested genotypes followed a similar trend with the corresponding fruit growth rates. After a cold night treatment, the net CO₂ assimilation rates of one- and two-fruit plants, which had increased sink demand, were higher than that of plants without fruits in all tested genotypes. This response indicates that feedback inhibition might be an important reason for the reduction of photosynthesis on the next day. In addition, after a cold night treatment, the levels of exportable sugars (sucrose and stachyose) in mature leaves of XC-1 were higher than those measured in Jinyan 4 and NY-1, which might explain why XC-1 fruits had faster assimilate accumulation rates in the next morning. Higher activity of sucrose-phosphate synthase, a key enzyme of sucrose and stachyose biosynthesis, constituted an additional evidence that faster sucrose and stachyose biosynthesis in mature leaves may occur in XC-1 than in Jinyan 4 and NY-1 at that time. In conclusion, our results showed that cucumber genotypes may use different mechanisms to enhance their cold tolerance.     

Effect of hot acetic acid solutions on postharvest decay caused by Penicillium expansum on Red Delicious apples

The objective of this research was improvement of apple hot water treatment efficiency by using acetic acid. The apples (cultivar Red Delicious) were treated using hot acetic acid solutions (1, 2 and 3%) at 50 °C for 1, 2 and 3 min. The results of in vitro study showed that treatment with acetic acid at 50 °C can significantly reduce the growth of Penicillium expansum spores. The treatment of apples with 50 °C acetic acid solutions, in particular 2% acetic acid solution for 3 min or 3% acetic acid solution for 2 min, had significant impacts in reducing the extent of decay of the fruit during the short time storage experiment, while this effect was not significant in the long-time storage.     

Temperature affects color and quality characteristics of ‘Pink’ wax apple fruit discs

Red color plays a very important role when wax apple fruits are purchased. Temperature is one of the key factors among those influencing red color development. We evaluated the effects of temperature on color formation and other quality characteristics of ‘Pink’ wax apple fruit discs by using constant, slow-increase, fast-increase, transient shifting to high temperature, shifting to high temperature for different length of time and different day/night temperature regimes. The results show temperature has pronounced effects on quality attributes of wax apple fruit discs. Anthocyanin and total soluble solid (TSS) were greatest in the 20 °C treated discs under constant temperatures. In the slow-increase and fast-increase treatments, quality attributes in disc were better in treatments with a final temperature of 25 °C than of 30 °C. The concentration of soluble sugars (SS), starch, total phenolic compounds (TPC), free amino acids (FAA) and soluble protein (SP) all decreased with increasing temperature. Transient shifting to high temperature of 30 °C for 1-day had no effect on pigmentation but treatment periods from 3- to 5-days had a substantial adverse effect. At 30 °C for 5-days, exposed discs had the lightest weight and shortest diameter as well. Both SS and TPC decreased in the 3- and 5-day treatments. When temperature was shifted from 20 to 30 °C for 2 to 11 days, the widest and heaviest discs were found in the 5-day treatment. Anthocyanin and TSS concentration decreased following increased length of exposure to high temperature. Pigmentation of discs exposed to high temperature treatment was worse than in uncultured controls. Both protein and FAA concentrations decreased after culture. Among the 5 different day/night temperature combinations, discs under 25/20 °C had the highest anthocyanin and TSS concentrations, while those under 30/15 °C had the worst.     

Changes in starch and soluble sugar concentrations in winter squash mesocarp during storage at different temperatures

The effects of storage at 5, 10 or 15 °C for 6 months on the concentrations of starch and soluble sugar in winter squash (Cucurbita maxima Duch.) cultivar ‘TC2A’ fruits were examined. Starch contents were significantly lower at 15 °C than at the other temperatures, although concentrations decreased throughout the storage period at all temperatures. Total soluble sugar contents increased during the first 3 months of storage regardless of temperature, and decreased at 5 °C or 15 °C, but not at 10 °C after 6 months. Myo-inositol and raffinose concentration patterns were more complex, and may reflect some role in regulating fruit metabolism during storage that may be important in maintaining overall squash fruit quality.     

Induction of disease resistance and ROS metabolism in navel oranges by chitosan

The objective of this work was to evaluate how disease resistance and reactive oxygen species (ROS) metabolism in harvested navel oranges (Citrus sinensis L. Osbeck) may be affected by chitosan. Fresh navel oranges were treated with 2% chitosan or 0.5% glacial acetic acid (control) solution for 1 min, and some were inoculated with Penicillium italicum and Penicillium digitatum. Then, the fruit were stored at 20 °C and 85–95% RH. Treatment with 2% chitosan significantly reduced the disease incidence and the lesion diameter compared with control fruit. This treatment effectively enhanced the activities of peroxidase (POD) and superoxide dismutase (SOD), and levels of glutathione (GSH) and hydrogen peroxide (H₂O₂), inhibited the activities of catalase (CAT) and the decreases of ascorbate (AsA) content during navel orange fruits storage. Ascorbate peroxidase (APX) activity in the navel orange fruit was induced slightly by the chitosan treatment during 14–21 days storage. However, glutathione reductase (GR) activity in the fruit was not enhanced by the chitosan treatment. These results indicated that chitosan treatment could induce the navel orange fruit disease resistance by regulating the H₂O₂ levels, antioxidant enzyme and ascorbate–glutathione cycle.