Fatty acid composition and antioxidant system in relation to susceptibility of loquat fruit to chilling injury

Two cultivars of loquat fruit with contrasting chilling resistance were stored at 1 °C for 35 days to investigate the relationship between chilling injury and fatty acid composition and its antioxidant system. No symptoms of chilling injury occurred in the fruit of ‘Qingzhong’ cultivar during the whole storage, whereas in ‘Fuyang’ fruit, chilling injury increased sharply after 21 days of storage at 1 °C. ‘Qingzhong’ fruit had lower levels of superoxide radical and H₂O₂, in addition to lower lipoxygenase activity, but higher membrane lipid unsaturation and higher activities of superoxide dismutase and catalase than ‘Fuyang’. Furthermore, the chilling resistant ‘Qingzhong’ fruit also showed higher activities of antioxidant enzymes involved in ascorbate–glutathione cycle and higher levels of ascorbate acid and reduced glutathione. These results suggest that the higher membrane lipid unsaturation and the more efficient antioxidant system were both beneficial in enhancing resistance of loquat fruit to chilling injury.     

MeJA induces chilling tolerance in loquat fruit by regulating proline and γ-aminobutyric acid contents

Loquat fruit were pretreated with 10 μmol l⁻¹ methyl jasmonate (MeJA) for 24 h at 20 °C and then stored at 1 °C for 35 days to investigate the effect of MeJA treatment on chilling injury (CI) and changes in the contents of proline and γ-aminobutyric acid (GABA). The control fruit exhibited severe flesh leatheriness, a specific CI symptom, after 21 days of storage at 1 °C, but it was reduced in MeJA-treated fruit. During the development of CI in fruit, proline and GABA accumulated with the storage time, while MeJA treatment enhanced the increases in proline and GABA contents. The MeJA-treated fruit exhibited higher activities of Δ¹-pyrroline-5-carboxylate synthetase (P5CS), ornithine δ-aminotransferase (OAT) and glutamate decarboxylase (GAD), and lower proline dehydrogenase (PDH) activity than control during storage. These results suggest that the reduction in CI in loquat fruit by MeJA may be due to the increased proline and GABA contents.     

Effect of methyl jasmonate on cell wall modification of loquat fruit in relation to chilling injury after harvest

Loquat fruit were pretreated with 10 μM methyl jasmonate (MeJA) for 24 h at 20 °C, and then stored at 1 °C for 35 days to investigate the effect of MeJA treatment on cell wall modification in relation to chilling injury. Loquat fruit developed chilling injury, manifested as increased fruit firmness and internal browning, decreased extractable juice during storage. These chilling injury symptoms were significantly reduced by MeJA treatment. MeJA also markedly delayed the increases in lignin, alcohol insoluble residues, hemicellulose and cellulose. Meanwhile, the MeJA-treated fruit exhibited significantly lower activities of phenylalanine ammonia lyase, peroxidase, polyphenol oxidase and higher polygalacturonase activity than the control during storage. The levels of water- and CDTA-soluble pectins in MeJA-treated fruit were also significantly higher than that in the control. These results suggest that the reduction in chilling injury by MeJA may be due to inhibited lignin accumulation and enhanced cell wall polysaccharides solubilisation.     

Postharvest quality of arazá fruit during low temperature storage

Arazá (Eugenia stipitata Mc Vaugh) fruits at breaker stage of maturity were stored at 7, 10, 12, or 20 °C and 85-90% RH for 2 weeks, with or without an additional simulated shelf-life period (3 days at 20 °C and 70% RH). Some half-yellow (turning) arazá fruit were also stored at 7 or 12 °C. Respiration rate, ethylene production, quality traits and physiological disorders and decay were monitored. Arazá fruit of both stages of maturity showed a climacteric pattern of ripening, with the maximum levels of respiration being reached after 5 days at 20 °C for breaker fruit, while half-yellow fruit ripened totally after one day. Weight loss was the most limiting quality trait for arazá fruit. Chilling injury symptoms included skin scald (only at 7 °C), uneven ripening (at 7 or 10 °C, including uneven softening during storage, particularly in breaker fruit), and slight acidification at 7 °C. Decay in the post-storage shelf-life periods (mainly Gloesporium sp.) was particularly high after storage at 7 °C in breaker fruit. The storage of breaker arazá fruit at 12 °C is recommended because this prevents chilling injury and flesh acidification, and allows normal fruit ripening during a post-storage shelf-life at 20 °C, as revealed by the lower organic acids (mainly malic) content and increased sugar (glucose, fructose and sucrose) content.     

Effect of high-temperature-conditioning treatments on quality,flavonoid composition and vitamin C of cold stored ‘Fortune’ mandarins

The effect of high-temperature-conditioning treatments (1–2 days at 37 °C) on fruit quality, flavonoids, total antioxidant capacity (TAC) and vitamin C was investigated in chilling-sensitive ‘Fortune’ mandarins subjected to single or double quarantine treatments (16 or 32 days at 1.5 °C, respectively). High temperature-conditioning treatments, which reduced chilling injury, allowed fruits to withstand quarantine treatments without affecting the fruit quality, vitamin C or TAC. Hesperidin and isorhoifolin were the most abundant flavonoids followed by didymin and narirutin, whereas the polymethoxylated flavones (PMFs) nobiletin and tangeretin were the less abundants. Didymin and narirutin slightly increased (∼1.5-fold) at 1.5 °C. A 4-fold increase occurred in eriocitrin, though its concentration was much lower. Small differences in flavonoids were found between non-conditioned fruit and fruit conditioned for 1 day after cold storage and their concentration in carpellary membranes were, in general, much higher than in juice. Therefore, fruit conditioning at 37 °C allows chilling-sensitive citrus cultivars to withstand quarantine treatments without having deleterious effects on the fruit quality, vitamin C or relevant flavonoids.     

Physiological and biochemical response of harvested plum fruit to oxalic acid during ripening or shelf-life

The effect of oxalic acid application on plum fruit (Prunus salicina cv. ‘Damili’) ripening properties during storage or shelf-life was determined. The fruits were dipped for 3 min in solutions containing 5 mmol/L oxalic acid and then were packed into polyethylene bags and stored at 25 °C for 12 days, or at 2 °C for 20 days and subsequently at 25 °C for 12 days. Ethylene production, fruit firmness, contents of pectin and anthocyanin, specific activities of polygalacturonase (PG), pectin methylesterase (PME) and phenylalanine ammonia lyase (PAL), and chlorophyll fluorescence (Fv/Fm) were measured. The application of oxalic acid reduced ethylene production and delayed softening of plum fruit. The inhibition of softening was associated with decreased PG and PME activities; that is, the retardation of pectin solubilization/degradation. During storage or shelf-life, flesh reddening and anthocyanin synthesis were significantly inhibited in oxalic acid-treated plum fruit, accompanied with decreased PAL activity. Furthermore, it was found that variable:maximalchlorophyll fluorescence (Fv/Fm), an indicator of ripening, senescence or stress injury of fruit and vegetable, decreased much more slowly in oxalic-treated plum fruits than in control fruits. Thus, oxalic acid treatment can be an effective means to extend the shelf life of plum fruit.     

Sugar metabolism and involvement of enzymes in sugarcane (Saccharum officinarum L.) stems during storage

Sugarcane (Saccharum officinarum L. cv. Badila) was harvested at the mature stage and stored at 2, 10, and 20 °C for 30, 90, and 120 days, respectively. Metabolic changes in the contents of sucrose and reducing sugar in relation to the activities of soluble acid invertase (SAI), neutral invertase (NI) and sucrose-phosphate synthase (SPS), in sugarcane juice, were studied. Extractable juice, sucrose and vitamin C declined significantly with increasing storage temperatures, while respiration rate increased. There was a rapid increase in titratable acidity during storage, with a more rapid rate at higher temperatures. A sharp increase in reducing sugar was observed within 20 days at 20 °C and 70 days at 10 °C, followed by a rapid decrease. Both SAI and NI activities showed a sharp increase within 15 days at 20 °C, followed by a rapid decrease, while a moderate increase occurred within 40–60 days at 10 °C. Slight increases were observed in SPS activity within 20 days at 20 °C and 50 days at 10 °C. Enzyme activities remained steady or underwent a small change in canes stored at 2 °C. Enzyme activities were significantly correlated with reducing sugar content.     

Cell wall-modifying enzymes and firmness loss in ripening ‘Golden Reinders’ apples: A comparison between calcium dips and ULO storage

Calcium treatment and storage under ultra-low oxygen (ULO) conditions are common post-harvest practices aimed at delaying ripening-related softening of apple (Malus × domestica Borkh.) fruit, but the biochemical mechanisms underlying these effects have not been determined conclusively to date. In this study, commercially mature ‘Golden Reinders’ apples were dipped in 2% calcium chloride prior to storage at 1 °C and 92% RH under either regular air or ultra-low oxygen (ULO; 1kPa O₂:2kPa CO₂) for 19 or 31 weeks, and kept thereafter at 20 °C for 0, 7 or 14 days in order to simulate the usual marketing time. Cell wall composition and cell wall-modifying enzyme activities were determined in relation to fruit firmness. ULO-storage and calcium dips were effective for firmness preservation, seemingly due to decreased pectin solubilisation. β-Galactosidase, α-l-arabinofuranosidase and pectate lyase activities were correlated positively with firmness loss of ‘Golden Reinders’ fruit after storage.     

Peach fruit acquired tolerance to low temperature stress by accumulation of linolenic acid and N-acylphosphatidylethanolamine in plasma membrane

Peach fruit (Prunuspersica L. cv. Beijing 33) did not show symptoms of chilling injury in 0 °C-Air or 0 °C-CA, but did in 5 °C-Air after 21 d. The mechanisms by which 0 °C storage could activate chilling tolerance of peach fruit were investigated by analysing characteristics of plasma membrane. We found that peach fruit stored in 0 °C-Air and 0 °C-CA had much higher linolenic acid content and unsaturation degree of plasma membrane than did that in 5 °C-Air. In addition, the fruits stored in 0 °C-CA showed a higher membrane fluidity and membrane integrity than did that in 0 °C-Air, which was related to the accumulation of N-acylphosphatidylethanolamine (NAPE) of peach fruits stored in 0 °C-CA. Based on these results, it appears that a higher unsaturation degree of membrane lipid and NAPE accumulation are beneficial for maintaining membrane fluidity, leading to an enhanced tolerance of peach fruit to chilling stress.     

Acetylsalicylic acid alleviates chilling injury of postharvest loquat (Eriobotrya japonica Lindl.) fruit

Loquat (Eriobotrya japonica Lindl. cv. Luoyangqing) is a chilling-sensitive fruit and therefore has a limited postharvest life. While fruit stored at 5 °C retained its acceptable quality after 39 days, fruit stored at 0 °C had chilling injury with the symptoms of tissue browning and lignification, decrease in percentage juice, increase in superoxide free radical production, electric conductivity and lignification enzyme activities, including phenylalanine ammonia lyase (PAL), cinnamyl alcohol dehydrogenase (CAD), and guaiacol-peroxidase (G-POD). Such chilling injury symptoms became more severe after fruit were moved to 20 °C shelf life. A postharvest application of 1 mmol/L aqueous acetylsalicylic acid (ASA, a derivative of salicylic acid) to loquat fruit significantly alleviated chilling injury symptoms, inhibited accumulation of superoxide free radical, and reduced PAL, CAD, and G-POD activities. ASA treatment impairing the accumulation of superoxide free radical may prevent chilling injury and lignification in loquat.     

Soluble Sugar Content and Metabolism as Related to the Heat-Induced Chilling Tolerance of Loquat Fruit During Cold Storage

The effects of high-temperature, short-time hot air treatment (45 °C for 3 h) on soluble sugar metabolism and chilling tolerance in loquat fruit stored at 5 °C for 5 weeks were investigated. Heat treatment significantly reduced chilling severity, as evidenced by lower firmness and internal browning and higher levels of extractable juice. Meanwhile, this treatment accelerated the activities of acid invertase, neutral invertase, sucrose phosphate synthase and sucrose synthase during storage. However, sucrose degradation was predominant, which caused lower levels of sucrose and higher levels of glucose and fructose in the heat-treated group. In addition, the ascorbate acid content and the activities of ascorbate peroxidase and glutathione reductase in the heat-treated fruit were much higher than those in control fruit, resulting in lower levels of hydrogen peroxide (H₂O₂) and malondialdehyde and decreased membrane permeability as well as a higher unsaturated/saturated fatty acid ratio at the end of storage. Our results suggest that the increased levels of reducing sugars, especially those of glucose, may induce the ascorbate–glutathione cycle activity to scavenge for H₂O₂, whose content relates to the heat-induced chilling tolerance of loquat fruit.     

Kinetics of changes in the physical quality parameters of fresh tomato fruits (Solanum lycopersicum, cv. ‘Zinac’) during storage

The effects of storage at different temperatures (2, 5, 10, 15 and 20 °C) conditions on whole tomato (Solanum lycopersicum, cv. ‘Zinac’, fruits harvested at mature-green stage) quality parameters, such as colour, chilling injury, firmness, weight loss and total phenolic content, were investigated during a month period.     

Reducing Chilling Injury of Loquat Fruit by Combined Treatment with Hot Air and Methyl Jasmonate

The effects of a combined treatment of hot air (HA, 38 °C for 6 h) and methyl jasmonate (MeJA, 16 μmol L^?1) on chilling injury, fruit quality, and physiological changes in loquat fruit stored at 1 °C were investigated. The results showed that treatment with HA or MeJA alone both significantly alleviated chilling injury in loquat fruit compared with the control, while their combination had the lowest level of chilling injury symptoms and highest quality. The activities of antioxidant enzymes such as superoxide dismutase, ascorbate peroxidase, and catalase were enhanced by the combination of HA and MeJA. In addition, the combined treatment significantly inhibited the activities of phenylalanine ammonia-lyase, peroxidase, and polyphenol oxidase, which resulted in lower lignin content. Highest level of polygalacturonase activity and water-soluble pectin content and lowest level of protopectin content were also observed in the combined treatment. These results suggested that the enhanced chilling tolerance by combination of HA and MeJA treatment in loquat fruit was related to the induction of antioxidant enzymes and the inhibition of lignin biosynthesis. The combination of HA and MeJA treatment could be a useful technique to alleviate chilling injury and maintain quality of loquat fruit during cold storage.     

Superchilling of rested Atlantic salmon: Different chilling strategies and effects on fish and fillet quality

Rested Atlantic salmon was superchilled in seawater slurry (−1.93 ± 0.27 °C). The chilling efficiencies of slurry and crushed ice were compared. The feasibility of using slurry to produce subzero core temperatures before packing was also evaluated. Simulated transport to market, with or without ice after initial superchilling (1 day), was also studied. Fish quality (Quality Index, fillet colour, pH, water content, water-holding capacity, hardness and bacterial loads) was evaluated at arrival to ‘market’ and after keeping the fish ‘in the market’ for 1 week. The results were compared with continuous ice (control) or slurry storage. In terms of quality, pre-chilling in slurry and continuous storage in slurry were evidently not advantageous over traditional ice storage, as evaluated after 4 days. After 11 days, both advantages and disadvantages of continuous superchilling were observed. Notably, subsequent ice storage of superchilled fish resulted in increased bacterial load and inferior fillet hardness.     

Effect of low temperature storage on physical and physiological characteristics of eggplant fruit (Solanum melongena L.)

Eggplant (Solanum melongena L.) is a perishable and chilling-sensitive tropical fruit. The chilling injury (CI) symptoms as well as some physical and physiological implications were studied in eggplants Money Maker No. 2 stored at 0 and 10 °C for 15 days. Eggplants stored at 10 °C were not damaged by temperature, whereas fruit stored at 0 °C suffered CI. Eggplant stored at 0 °C exhibited a decrease in L₀ (lightness) and ΔL (oxidation potential), increase of pH and electrolyte leakage after CI symptoms are manifested. At this temperature, flesh tissue revealed ultrastructural damage. On the other hand, skin from upper fruit section showed more lightness, reddish colouration, and lower content of anthocyanins than the central fruit section at harvest and over the entire storage period at 0 °C. In fruit stored at this temperature and in upper section, changes of anthocyanin content with time were closely proportional to the Chroma evolution (lower content of anthocyanin, lower saturation of colour).     

Antioxidant and radioprotective properties of commercially grown litchi (Litchi chinensis) from India

In an earlier study, radiation treatment (0.5 kGy) and low temperature (4 °C) storage were found to extend the shelf life of litchi fruit var. ‘Shahi’ and ‘China’ from India up to 28 days, while maintaining its physical, biochemical and organoleptic properties. The current study was aimed to elucidate the antioxidant and radioprotective properties of the litchi fruit, and the effect of radiation processing on these properties. The litchi fruit was found to be significantly rich in antioxidant and radioprotective properties, and the antioxidant parameters were found to be well correlated with the phenolic and flavonoid contents. A significant protection to pBR322 plasmid DNA and Escherichia coli cells from radiation induced damage was observed in the presence of litchi juice. Plasmid DNA was well protected even at the dose of 5 kGy, whereas, bacterial cells could be protected up to 0.5 kGy. Neither of these properties was found to be sensitive to radiation processing or low temperature storage.     

Changes in red pepper antioxidants as affected by UV-C treatments and storage at chilling temperatures

Chilling injury (CI) is one of the main factors limiting refrigeration in several horticultural commodities of subtropical and tropical origin such as pepper. Short UV-C treatments before low temperature storage have been shown to reduce CI. In this work we wanted to test whether or not the reduced susceptibility to CI in UV-C treated fruits was associated with increased levels of antioxidant compounds and enzymes. Red peppers (Capsicum annuum L.) were treated with UV-C radiation (10 kJ/m²) and stored at 0 °C for 21 d. During storage we analyzed chilling injury development, ascorbic (AA) and dehydroascorbic acids and DPPH radical scavenging capacity. We also followed superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and guaiacol peroxidase (GPX) activities. CI increased rapidly when the fruit was stored for longer than 14 d, but was significantly lower in UV-C treated peppers. Exposure to UV-C did not alter fruit color but reduced weight loss. Although AA and DPPH radical scavenging capacity were lower in the control, this occurred towards end of storage, when CI was already advanced. In contrast, SOD, CAT and APX activities were higher in UV-C treated fruits during the first 2 weeks of storage when the symptoms became visible. Results show that UV-C exposure prevents CI and weight loss in red pepper and suggest that this might be related to increased activity of antioxidant enzymes.     

Crucial contribution of membrane lipids’ unsaturation to acquisition of chilling-tolerance in peach fruit stored at 0 °С

Peach fruits (Prunus persica L.) were less prone to chilling injury (CI) when stored at 0 °С than at 5 °С for 30 days. In order to make known the mechanism involved, the relationship between CI and membrane lipid unsaturation was investigated in this study. The results demonstrated that peach fruit stored at 0 °С manifested higher membrane lipid fluidity and higher membrane lipid unsaturation than at 5 °С. In addition, a higher omega-3 fatty acid desaturase gene (FAD) mRNA level and a higher level of linolenic acid (C18:3) were found when peach fruits were stored at 0 °С. The findings indicated that the higher membrane lipid unsaturation in peach fruit stored at 0 °С was beneficial in maintaining membrane lipid fluidity and enhancing tolerance of peach fruit to low temperature stress, and the C18:3 level could be regulated by omega-3 FAD.     

Shelf-life extension of highbush blueberry using 1-methylcyclopropene stored under air and controlled atmosphere

The potential of 1-methylcyclopropene for controlling ripening in ‘Lateblue’ blueberry fruit was explored. After harvest, blueberry fruits were exposed to 1-MCP (0.3 and 0.6 μl l⁻¹). After treatment, samples were stored in air at 0 °C for 35 days and in a controlled atmosphere (3 kPa O₂ + 11 kPa CO₂) for 60 days. Quality parameters were monitored (weight loss, total soluble solids content, titratable acidity, firmness, anthocyanin content, phenolic content, total antioxidant capacity). Blueberries treated with 1-MCP showed a reduced weight loss during storage and a lower total soluble solid content compared to untreated fruit. High titratable acidity values were observed after controlled atmosphere storage, but no significant effect of 1-MCP on this parameter was observed. 1-MCP had no significant effects on anthocyanins, phenolics or antioxidant activities.