Amelioration of chilling stress by arginine in tomato fruit: Changes in endogenous arginine catabolism

Freshly harvested tomato fruit were pretreated with 0.2 mM arginine at −35 kPa for 0.5 min and then stored at 2 °C for 28 d to investigate the effect of exogenous arginine treatment on endogenous arginine catabolism in relation to chilling injury (CI). Arginine treatment reduced the CI index of fruit and enhanced accumulation of polyamines, especially putrescine, and proline, which resulted from the increased activities of the catabolic enzymes arginase, arginine decarboxylase, ornithine decarboxylase and ornithine δ-aminotransferase at most sampling times. Nitric oxide synthase activity was also increased by arginine treatment, which at least partly contributed to the increased nitric oxide concentration. These results revealed that the reduction in CI by exogenous arginine may be due to the accumulation of putrescine, proline and nitric oxide induced by activating the different pathways of endogenous arginine catabolism.     

Magnetic resonance imaging provides spatial resolution of Chilling Injury in Micro-Tom tomato (Solanum lycopersicum L.) fruit

Magnetic resonance imaging (MRI) was used to monitor internal changes in harvested tomato (Solanum lycopersicum L. cv. Micro-Tom) fruit. Measurements of ethylene evolution, respiration, and ion leakage indicated that the fruit developed chilling injury (CI) after storage at 0 °C. Unlike these measurements, MRI provided spatially resolved data. The apparent diffusion coefficient (ADC), which is an indication of water mobility in tissues, was calculated from MRIs of the different parts of the fruit. Storage for 1 or 2 weeks at 0 °C caused no difference in the ADCs (D-values) in the pericarp, but it did lead to higher values in the inner tissues i.e., the columella and locular region compared to non-chilled fruit (P < 0.05). Changes in inner fruit D-values after 1 and 2 weeks of chilling at 0 °C were similar to changes in respiration, ethylene production and ion leakage which increased (P < 0.05) compared to the non-chilled controls. Most CI studies of tomato fruit used pericarp tissue. Our data indicate that columella tissue changes occur in response to chilling injury in tomato fruit and suggest that more caution is needed when interpreting data from experiments commonly used to study this phenomenon.     

Effect of hot water treatments on chilling injury and expression of a new C-repeat binding factor (CBF) in ‘Hongyang’ kiwifruit during low temperature storage

Kiwifruit is cold-sensitive and very susceptible to chilling injury (CI) during low temperature storage. In this study, kiwifruit (Actinidia chinensis cv. Hongyang) were pre-treated by water dip for 10 min at 20 (control) or 35, 45, or 55 °C (heat pretreatments) and then stored at 0 °C for 90 days to investigate the effect of hot water treatments (HWT) on chilling injury tolerance. Results showed that 35 °C and 45 °C HWT alleviated but did not completely prevent chilling injury development. By contrast, 55 °C HWT increased symptoms of chilling injury. The 45 °C HWT was the most effective at reducing chilling injury index and incidence. Compared with the other HWT, fruit treated at 45 °C exhibited higher firmness and soluble solids content (SSC), and lower malondialdehyde (MDA) content, lipoxygenase (LOX) activity and ethylene production rate. C-repeat/dehydration-responsive element binding factors (CBFs) are key regulators in cold response. To investigate the molecular regulation of HWT on chilling tolerance of kiwifruit, a 637 bp CBF gene was identified and the relative expression of AcCBF was measured by RT-qPCR. In accordance with the effects of HWT on physiological parameters of chilling injury, AcCBF expression level was highest in the 45 °C HWT. These results indicate that HWT at 45 °C for 10 min prior to low temperature storage is effective for alleviating symptoms of chilling injury in ‘Hongyang’ kiwifruit.     

Postharvest ethylene conditioning as a tool to reduce quality loss of stored mature sweet oranges

Ethylene is related to senescence but also induces protective mechanisms against stress in plants. The citrus industry only applies the hormone to induce fruit degreening. The aim of this work was to determine the effect of ethylene on the quality of colored citrus fruit stored under commercial conditions to extend postharvest life, since it protects them from stress causing postharvest disorders such as chilling injury (CI) and non-chilling peel pitting (NCPP). The effect of conditioning mature Navelate and Lane Late sweet oranges (Citrus sinensis L. Osbeck) for 4 days with 2 μL L⁻¹ ethylene at 12 °C, rather than at higher temperatures used for degreening, on the quality of fruit stored at 2 or 12 °C, was examined. The ethylene conditioning (EC) treatment did not increase color but reduced calyx abscission and NCPP in fruit of both cultivars stored at 12 °C, and also CI in Navelate fruit at 2 °C. Lane Late fruit did not develop CI but showed a new disorder in EC fruit held at 2 °C. This disorder began as scalded areas around the fruit stem end and extended over the fruit surface during storage. EC had no deleterious effect on the quality of Navelate oranges stored at either 2 or 12 °C. Similar results were found in Lane Late fruit although EC slightly increased off-flavor perception at 2 °C and the maturity index at 2 and 12 °C. Moreover, EC slightly increased the content of bioactive flavonoids in the pulp of Navelate fruit but significant differences between control and EC fruit were only found after prolonged storage at 2 °C. In Lane Late fruit, EC avoided the initial decrease in flavonoid content found in control samples. Results show, therefore, that EC at 12 °C may be a tool to extend postharvest life of NCPP and CI-sensitive oranges, and that the tolerance of citrus cultivars to the combined effect of EC and non-freezing low temperature (2 °C) should be tested to select the proper storage temperature.     

Chilling injury in mango (Mangifera indica) fruit peel: Relationship with ascorbic acid concentrations and antioxidant enzyme activities

We investigated the degree of chilling injury (CI) in mango (Mangifera indica) fruit stored at 4 °C or 12 °C, in relation to peel ascorbic acid concentrations, total antioxidant capacity, and the activities of four antioxidative enzymes. In cv. Nam Dok Mai fruit exposed to 4 °C, CI (peel browning) was found after 5 days, whilst CI in cv. Choke Anan fruit started after 10 days and did not reach the same degree. When held at 27–28 °C, following various periods of exposure to 4 °C, peel browning in both cultivars increased, but that in cv. Nam Dok Mai remained higher than in cv. Choke Anan. An inverse correlation was found between peel browning and ascorbic acid concentrations, and between peel browning and total antioxidant capacity, measured using the FRAP method. In cv. Nam Dok Mai, the superoxide dismutase (SOD) and catalase (CAT) activities were lower during storage at 4 °C than during storage at 12 °C, while such a difference was not found in cv. Choke Anan. When compared to cv. Choke Anan, lower activities of ascorbate peroxidase (APX) and of guaiacol peroxidase (POX) were found in the peel of cv. Nam Dok Mai. However, no difference was observed in APX and in POX activities in the peel of cv. Nam Dok Mai stored at 4 °C or 12 °C. This means that the relationships between CI and APX and POX activities were weak.     

Interpreting textural changes in low temperature stored tomatoes

Low temperature storage alters tomato textural properties, resulting in unusual changes in firmness, while ripening during cool storage can confound these chilling-induced textural changes. Inconsistent results have been reported related to chilling-induced alteration in tomato texture. The effects of chilling on tomato texture were investigated using fruit stored at 2.5 or 6 °C (chilled) or 20 °C (non-chilled) for 27 d before transfer to 20 °C. Given that many factors influence the firmness of chilling-injured tomato and different measurement methods indicate different characteristics of tomato texture, the present study employed a range of textural measurement techniques in order to interpret chilling-induced textural changes in tomatoes during long term storage. Analysis of data from a range of textural methods indicated that storage at 6 °C mainly induced loss of turgor whereas 2.5 °C induced loss of tissue integrity along with turgor loss. Plotting textural changes against colour as an indicator of ripening allowed a clearer definition of chilling-induced textural change.     

Postharvest nitric oxide fumigation delays fruit ripening and alleviates chilling injury during cold storage of Japanese plums (Prunus salicina Lindell)

We investigated the effects of nitric oxide (NO) fumigation on fruit ripening, chilling injury, and quality of Japanese plums cv. ‘Amber Jewel’. Commercially mature fruit were fumigated with 0, 5, 10, and 20 μL L⁻¹ NO gas at 20 °C for 2 h. Post-fumigation, fruit were either allowed to ripen at 21 ± 1 °C or were stored at 0 °C for 5, 6, and 7 weeks followed by ripening for 5 d at 21 ± 1 °C. NO-fumigation, irrespective of concentration applied, significantly (P ≤ 0.5) suppressed respiration and ethylene production rates during ripening at 21 ± 1 °C. At 21 ± 1 °C, the delay in ripening caused by NO-fumigation was evident from the restricted skin colour changes and retarded softening in fumigated fruit. NO treatments (10 and 20 μL L⁻¹) delayed the decrease in titratable acidity (TA) without a significant (P ≤ 0.5) effect on soluble solids concentration (SSC) during ripening. During 5, 6, and 7 weeks of storage at 0 °C, NO-fumigation was effective towards restricting changes in the ripening related parameters, skin colour, firmness, and TA. The individual sugar (fructose, glucose, sucrose, and sorbitol) profiles of NO-fumigated fruit were significantly different from those of non-fumigated fruit after cold storage and ripening at 21 ± 1 °C. CI symptoms, manifest in the form of flesh browning and translucency, were significantly lower in NO-fumigated fruit than in non-fumigated fruit after 5, 6, and 7 weeks storage followed by ripening for 5 d at 21 ± 1 °C. NO-fumigation was effective in reducing decay incidence in plums during ripening without storage and after cold storage at 0 °C for 5, 6, and 7 weeks. In conclusion, the postharvest exposure of ‘Amber Jewel’ plums to NO gas (10 μL L⁻¹) delayed ripening by 3–4 d at 21 ± 1 °C, and also alleviated chilling injury symptoms during cold storage at 0 °C for 6 weeks.     

Effect of sustained deficit irrigation on physicochemical properties,bioactive compounds and postharvest life of pomegranate fruit (cv. ‘Mollar de Elche’)

In this study, the influence of sustained deficit irrigation (SDI; 32% of reference evapotranspiration (ET₀)) on physicochemical and sensory quality and bioactive compounds of pomegranates stored for 30, 60 and 90 days in air at 5 °C + 4 days at 15 °C, at each storage period, was studied and compared to a control (100% ET₀). Fruit from SDI had higher peel redness and greater firmness, soluble solids contents, vitamin C (27%), phloretin (98%) and protocatechuic acid (10%) levels, and total antioxidant capacity (TAC) (46%) than the control. Cold storage and shelf-life did not induce significant changes in soluble solids, pH, titratable acidity, and chroma and Hue. SDI fruit had retarded development of chilling injury (CI) symptoms, which appeared after 60 days of storage in comparison to 30 days in the controls. Anthocyanins, catechin, phloretin and protocatechuic, caffeic, p-coumaric and caffeic acids contents had greater increases in SDI fruit than in controls throughout the postharvest life. TAC was significantly (P < 0.05) correlated to anthocyanins, gallic acid and total vitamin C contents. Generally, after long term storage, the fruit grown under SDI showed higher sensory and nutritional quality, more health attributes and a longer shelf-life (up to 90 days at 5 °C + 4 at 15 °C) than fruit irrigated at 100% ET₀.     

Influence of environmental conditions on the quality attributes and shelf life of ‘Goldfinger’ bananas

‘Goldfinger’ bananas (Musa accuminata, FHIA-01) were harvested, held for 14–22 d at five temperatures and a constant relative humidity (RH) or at five RHs and a constant temperature and evaluated for quality attributes. The objectives of this work were to: (1) create quality curves for bananas stored at chilling and non-chilling temperatures; (2) create quality curves for bananas stored at a non-chilling temperatures and different RHs; (3) identify which sensory quality attribute limits the shelf life and marketability of bananas when stored at chilling and non-chilling temperatures or at different RHs; and (4) correlate subjective sensory attributes with quantitative quality measurements. Results from this study showed that temperature had a more significant impact on the quality of banana than RH. Bananas stored at temperatures higher than 10 °C were yellower and softer but had lower starch and higher soluble solids and total sugar content than those stored at lower temperatures. When stored at 2, 5 and 10 °C, bananas developed chilling injury (CI) and abnormal ripening when transferred to 20 °C. The most remarkable impact of RH on banana quality was on weight loss, which was significantly higher in fruit held below 80% RH than in fruit held in 87 or 92% RH. CI was the first sensory quality attribute to reach the limit of acceptability in fruit stored at 2, 5 and 10 °C, whereas color changes and softening limited the shelf life of bananas stored at 15 and 20 °C. Changes in color and/or softening were the two main sensory attributes that limited the shelf life of bananas stored at different RHs. Overall, for maximum quality and shelf life bananas should be stored at or above 15 °C and 92% RH. Finally, sensory attributes can be used to estimate peel color, pulp softening and sweetness, while SSC can be used as a reliable and simple method to estimate the total sugar content of bananas stored at different temperatures or different RHs.     

Effect of ethylene degreening on the development of postharvest penicillium molds and fruit quality of early season citrus fruit

The effect of commercial degreening with ethylene gas on fruit susceptibility and quality and development of postharvest green (GM) and blue (BM) molds on early season citrus fruit was investigated. Each cultivar was harvested with different peel color indexes (CI). Fruit were exposed for 3 d to 2 μL L⁻¹ ethylene at 21 °C and 95–100% RH before or after artificial inoculation with Penicillium digitatum or Penicillium italicum. Control fruit were kept at the same environmental conditions without ethylene. Fruit were stored at either 20 °C for 7 d or 5 °C for 14 d and disease incidence (%) and severity (lesion diameter) were assessed. No significant effect of commercial degreening was observed on fruit susceptibility to both GM and BM on citrus cultivars inoculated after degreening. Likewise, no significant effect was observed on disease incidence on citrus cultivars inoculated before degreening and stored at either 20 °C for 7 d or 5 °C for 14 d. In contrast, in cultivars like ‘Clemenules’ mandarins and ‘Navelina’ oranges, degreening significantly increased the severity on fruit with higher initial CI (−3.6 and 1.7, respectively). GM and BM severity on degreened and control ‘Clemenules’ mandarins incubated at 20 °C for 7 d was 146 and 118 mm and 56 and 46 mm, respectively. In general, commercial degreening did not significantly affect external and internal quality attributes of citrus cultivars. Commercial degreening after inoculation of less green (more mature) fruit showed a trend to increase mold severity, presumably through an aging effect (acceleration of peel senescence).     

Efficacy of 1-MCP treatment in tomato fruit: 1. Duration and concentration of 1-MCP treatment to gain an effective delay of postharvest ripening

‘Raf’ tomato fruit were harvested at the mature-green stage and treated with 1-methylcyclopropene (1-MCP) at 0.5 (for 3, 6, 12 or 24 h) or 1 μl l⁻¹ for 3 or 6 h. Fruit were stored at 10 °C for 7 days and a further 4 days at 20 °C for a shelf life period. All 1-MCP treatments reduced both ethylene production and respiration rate and in turn retarded the changes in parameters related to fruit ripening, such as fruit softening, colour (a^*) change, and increase in ripening index (TSS/TA ratio). These effects were significantly higher when 1-MCP was applied at 0.5 μl l⁻¹ for 24 h. In order to obtain the maximum benefit from 1-MCP, this treatment would be the most suitable for commercial purposes.     

Response of climacteric-type guava (Psidium guajava L.) to postharvest treatment with 1-MCP

Guava (Psidium guajava L. cv. ‘Allahabad Safeda’) fruit harvested at the mature light-green stage were exposed to 300 and 600 nL L⁻¹ 1-methylcyclopropene (1-MCP) for 6, 12 and 24 h at 20 ± 1 °C, and held in either cold storage (10 °C) for 25 days or ambient conditions (25–29 °C) for 9 days. Most of the physiological and biochemical changes during storage and ripening were affected by 1-MCP in a dose dependent manner. Ethylene production and respiratory rates were significantly suppressed during storage as well as ripening under both the storage conditions depending upon 1-MCP concentration and exposure duration. 1-MCP treatment had a pronounced effect on fruit firmness changes during storage under both the conditions. The reduced changes in the soluble solids contents (SSC), titratable acidity (TA) and vitamin C content showed the effectiveness of 1-MCP in retarding fruit ripening. Vitamin C content in 1-MCP-treated fruit was significantly higher than in non-treated fruit, and those treated with 300 nL L⁻¹ 1-MCP for 6 h. The development of chilling injury symptoms was ameliorated to a greater extent in 1-MCP-treated fruit during cold storage and ripening. A significant reduction in the decay incidence of 1-MCP-treated fruit was observed under both the storage conditions. 1-MCP at 600 nL L⁻¹ for 12 h, in combination with cold storage (10 °C) seems a promising way to extend the storage life of guava cv. ‘Allahabad Safeda’ while 1-MCP at 300 nL L⁻¹ for 12 and 24 h or 600 nL L⁻¹ for 6 h, may be used to provide 4–5 days extended marketability of fruit under ambient conditions.     

Role of putrescine in regulating fruit softening and antioxidative enzyme systems in ‘Samar Bahisht Chaunsa’ mango

The role of putrescine (PUT) in regulating fruit softening, antioxidative enzymes and biochemical changes in fruit quality was investigated during ripening and cold storage of mango (Mangifera indica cv. Samar Bahisht Chaunsa). Fruit were treated with various PUT concentrations (0.0, 0.1, 1.0 and 2.0 mM) and were allowed to ripen at 32 ± 2 °C for 7 days, or stored at 11 ± 1 °C for up to 28 days. Respiration rate and ethylene production were measured daily during ripening and cold storage. Cell wall degrading enzymes such as exo-polygalacturonase (exo-PG), endo-polygalacturonase (endo-PG), pectin esterase (PE), endo-1,4-β-d-glucanase (EGase), antioxidative enzymes including superoxide dismutase (SOD), peroxidase (POX), and catalase (CAT), fruit firmness as well as biochemical fruit quality characteristics were estimated during ripening and cold storage at 2 and 7 day intervals, respectively. PUT treatments reduced respiration rate, ethylene production and maintained higher fruit firmness during ripening as well as cold storage. PUT-treated fruit exhibited significantly suppressed activities of cell wall enzymes (exo-, endo-PG and EGase), but retained higher PE activity during ripening and cold storage. Total phenolic and antioxidant contents were significantly higher in PUT-treated fruit during ripening as well in the cold storage period than in the controls. Activities of antioxidative enzymes (CAT, POX and SOD) were also significantly higher in PUT-treated fruit during ripening as well as cold storage. SSC and SSC:TA were lower in PUT-treated fruit, while TA and ascorbic acid content showed the reverse trend. In conclusion, pre-storage 2.0 mM PUT treatment inhibited ethylene production and suppressed the activities of cell wall enzymes, while resulting in higher activities of antioxidative enzymes and maintaining better fruit quality during ripening and cold storage.     

Ethylene synthesis,ripening capacity,and superficial scald inhibition in 1-MCP treated ‘d’Anjou’ pears are affected by storage temperature

A continuing challenge for commercializing 1-methylcyclopropene (1-MCP) to extend the storage life and control superficial scald of ‘d’Anjou’ pear (Pyrus communis L.) is how to initiate ripening in 1-MCP treated fruit. ‘D’Anjou’ pears harvested at commercial and late maturity were treated with 1-MCP at 0.15 μL L⁻¹ and stored either at the commercial storage temperature −1.1 °C (1-MCP@−1.1 °C), or at 1.1 °C (1-MCP@1.1 °C) or 2.2 °C (1-MCP@2.2 °C) for 8 months. Control fruit stored at −1.1 °C ripened and developed significant scald within 7 d at 20 °C following 3–5 months of storage. While 1-MCP@−1.1 °C fruit did not develop ripening capacity due to extremely low internal ethylene concentration (IEC) and ethylene production rate for 8 months, 1-MCP@1.1 °C fruit produced significant amounts of IEC during storage and developed ripening capacity with relatively low levels of scald within 7 d at 20 °C following 6–8 months of storage. 1-MCP@2.2 °C fruit lost quality quickly during storage. Compared to the control, the expression of ethylene synthesis (PcACS1, PcACO1) and signal (PcETR1, PcETR2) genes was stable at extremely low levels in 1-MCP@−1.1 °C fruit. In contrast, they increased expression after 4 or 5 months of storage in 1-MCP@1.1 °C fruit. Other genes (PcCTR1, PcACS2, PcACS4 and PcACS5) remained at very low expression regardless of fruit capacity to ripen. A storage temperature of 1.1 °C can facilitate initiation of ripening capacity in 1-MCP treated ‘d’Anjou’ pears with relatively low scald incidence following 6–8 months storage through recovering the expression of certain ethylene synthesis and signal genes.     

Pulsed light effects on surface decontamination,physical qualities and nutritional composition of tomato fruit

Pulsed light (PL) is a nonthermal food technology with a potential as postharvest decontamination strategy for fruit and vegetables. The feasibility of PL in extending shelf-life of food products while assuring appropriate quality is still under investigation. The effect of pulsed light (PL) on surface decontamination (natural and inoculated microorganisms), physical (colour, texture and weight) and nutritional quality (ascorbic acid and major carotenoids) was investigated in red-ripe tomatoes during 15 days of storage at 20 °C. The application of PL treatments at fluences of 2.68 and 5.36 J/cm² reduced microbial loads during storage of whole tomatoes. One log₁₀ reduction on the microflora present in both skin and peduncle scar parts of the tomato was obtained with a fluence of 4 J/cm². Fluences of 2.2 J/cm² allowed a 2.3 log₁₀ reduction of Saccharomyces cerevisiae inoculated onto the tomato surface. Softening, increased loss of weight, and wrinkles on the tomato surface appeared after 3 days on PL treated tomato fruit. Ascorbic acid levels remained unchanged during storage. Total lycopene, α-carotene and β-carotene contents and lycopene isomerisation percent were higher in tomato extracts prepared with fresh tomato fruit treated with a high PL dose of 30 J/cm². An increase in the bio-accessibility of lycopene was observed in hot-break purees prepared with fresh tomatoes treated at 5.36 J/cm² and stored 15 days. In conclusion, PL treatment of fresh tomato would result in a reduction in microbiological contaminants without compromising the nutritional value; but it did induce some appearance defects.     

Postharvest treatment of polyamines maintains quality and extends shelf-life of table grapes (Vitis vinifera L.) cv. Flame Seedless

Investigations were carried out to verify the potential of putrescine and spermidine as a postharvest dip treatment for maintaining quality and extending storage life of table grapes (Vitis vinifera L.) cv. Flame Seedless during the 2012 and 2013 seasons. Grape clusters were manually harvested at the commercial mature stage and were dipped in different concentrations (0.0, 0.5, 1.0 and 1.5 mM) of putrescine and spermidine, and then stored at 3–4 °C, and 90–95% RH. Evaluation of physico-chemical parameters and other fruit quality attributes were made at 0 day (before treatment) and at 30, 45, 60 and 75 days of storage. Putrescine and spermidine at the lowest dose (0.5 mM) effectively maintained berry firmness, peel colour (L*, C*, h°) and stabilized anthocyanins as well as suppressing the activity of pectin methylesterase and reducing the rate of electrolyte leakage. The polyamines also retarded the degradation of TSS and TA while maintaining higher total phenol content and reduced decay incidence. Putrescine and spermidine at 1.0 mM exhibited almost similar effects with a 0.5 mM dose. The highest doses (1.5 mM) of both polyamines showed detrimental effects, especially on weight loss, decay incidence, rachis browning and organoleptic properties, as found in the control group, which was commercially acceptable only up to 45 days. Furthermore, analysis of linear regressions and correlations showed that many quality parameters were interdependent. The postharvest dip treatment of spermidine or putrescine at a dose of 0.5 mM for 5 min could be an effective means for prolonging storage and increasing shelf-life of ‘Flame Seedless’ grapes.