Primary Metabolism in Fresh Fruits During Storage

The highly perishable nature of mango fruit and its susceptibility to chilling injury (CI) when stored below 13°C limits its international trade. Cold storage of mango at 12-13°C is successful only for 2-3 weeks coupled with substantial losses in fruit quality. Cold storage limits the use of sea freight which is usually more economical and eco-friendly than air freight. Controlled atmosphere (CA) storage usually involves regulating the concentration of oxygen (O2) and carbon dioxide (CO2) using nitrogen, storage temperature, as well as relative humidity in the storage environment. CA in combination with an optimum storage temperature has been reported to prolong the storage life and maintain fruit quality including aroma volatiles in mango fruit depending upon the cultivar. Fruit quality is an important factor in influencing consumer preferences in international and domestic markets. CA storage seems to be promising in extending storage life, maintaining quality of mango fruit consequently offers opportunities to export mangoes to distant markets using sea freight. This overview paper will focus on fundamental and applied aspects of CA storage of mango fruit and its implications in facilitating international trade. Some research work has been reported on optimising CA conditions for different cultivars of mango as the CA requirements of mangoes vary among cultivars and inappropriate CA conditions adversely affect quality of ripe mango fruit. CA comprising of low O2 concentrations (<2%) has been reported to accumulate ethanol and adversely affect fruit quality of ‘Tommy Atkins’ and ‘Delta R2E2’ cultivars of mango. My research group has been exploring the effects of CA on extending storage life, maintaining fruit quality including aroma volatiles production in mango fruit for more than a decade. CA storage comprising 3% O2 in combination with 6% CO2 at 13°C proved to be beneficial for extending the storage life of the Australian mango cultivars ‘Kensington Pride’ and ‘R2E2’ by up to six weeks, with good fruit quality and maintaining a high concentration of the major volatile compounds responsible for the aroma of ripe mangoes. The applications of CA in preventing CI, postharvest diseases and insect disinfestations will also be discussed. The faster rate of expansion of mango production, its international trade, short shelf life, and higher susceptibility to CI, postharvest diseases, as well as consumer demand for superb quality are major challenges in extending storage life of mango fruit and their implications in international trade. CA storage offers a great potential in extending storage life of mango which enable to employ sea freight for wider distribution of mango fruit in the distant international markets in a very cost effective manner. A specific composition of O2 and CO2 in CA which extends the storage life of mango fruit is cultivar dependent and is yet inconclusive. Moreover, to minimise the negative effects of CA storage in mango such as fruit softening, poor colour development and higher titratable acidity (TA), reduced aroma and flavour are major research gaps yet to be addressed by the research in the future. CA storage offers an attractive alternative for ameliorating CI, controlling of postharvest diseases and pests in combination with preharvest technology. A holistic approach to meet market requirements considering mango production, postharvest handling including CA storage and supply chain is prerequisite for promoting international trade of mango.

FORCED-AIR COOLING REDUCES 1-MCP APPLICATION DURATION ON PLUMS (PRUNUS SALICINA LINDL.) WITHOUT REDUCING EFFECTIVENESS

Our previous studies have shown that ‘Palmer’ mangoes immersed in solutions containing 2.5% sorbitol and stored under a controlled atmosphere (CA) at 8 °C for 30 days had fewer symptoms of a chilling injury. However, there is no information regarding the effectiveness of sorbitol treatment in other atmospheres and/or in combination with lower temperatures. Thus, the objective of this study was to assess the impact of dipping ‘Palmer’ mangoes in 0.1% and 2.5% (w/v) sorbitol solutions and storing the fruit under a CA without atmosphere modification (21 kPa O2 + 0.03 kPa CO2) at 8 °C/95% relative humidity (RH) or with 5 kPa O2 + 5 kPa CO2 at 4 °C/95% RH for 28 days. The fruits were evaluated periodically for chilling injuries, quality, and oxidative metabolism. A chilling injury (CI) was correlated with increased fresh weight loss (FWL) and changes in the color of the epicarp (Lpeel, h°peel, and Cpeel) and mesocarp (L*pulp). Lipid peroxidation (LPpulp and LPpeel) and the hydrogen peroxide content (H2O2peel and H2O2pulp) were associated with the development of a CI, particularly after being transferred to ambient. The treatment with 2.5% sorbitol was more effective in minimizing the chilling injury symptoms and did not compromise the fruit quality, especially when it was stored at 4 °C in association with a CA containing 5 kPa O2 + 5 kPa CO2. This treatment reduced lipid peroxidation and increased the activities of the superoxide dismutase (SOD) and ascorbate peroxidase (APX) enzymes in the epicarp and mesocarp, providing greater cold tolerance. The use of 2.5% sorbitol has been identified as the most efficacious approach for mitigating the adverse impacts of chilling injuries, preserving the fruit quality, and enhancing oxidative metabolism, even at lower temperatures. Thus, this treatment represents a viable alternative for managing chilling injuries in mangoes.

Fruit quality is preserved through cold storage, but climacteric fruits are prone to chilling injury (CI) which limits their shelf life and marketability. Two postharvest treatments, 1 mM methyl jasmonate (MeJA) and 4% (wt/vol) calcium chloride (Ca2+), were separately used to investigate their influences on chilling injury (CI) incidence and fruit quality in unpacked banana cultivar “Grand Nain” during cold storage and subsequent ripening. Banana fruits were dipped for 2 min in aqueous emulsions containing 1% Tween‐80—used here as a surfactant with untreated fruits being used as control. Fruits were stored at 10 ± 2 or optimal 14 ± 2°C temperature and relative humidity 85%–90% for a 20‐day cold storage period and then removed from cold storage at 5, 10, 15, and 20 days followed by ripening at 22 ± 2°C. Treatments with MeJA or Ca2+ significantly reduced CI in banana fruit during cold storage and subsequent ripening temperature. Untreated controls exhibited increased CI, weight loss, and decreased hue angle, as well as firmness. In contrast, the aforementioned changes were considerably delayed after treatments with MeJA or Ca2+. Application of MeJA or Ca2+ also increased total phenolic compound contents and maintenance of total antioxidant activity throughout cold storage and during ripening periods as compared to that of the control. These findings indicate that coating bananas with 1 mM MeJA or 4% (wt/vol) Ca2+ can improve the postharvest quality and shelf life of fruits, and it can ameliorate chilling injury during cold storage and at ripening temperature.

Peaches (Prunus persica) were packaged in two kinds of gas environments: the steady-state controlled atmosphere (CA) of 10% O2 and the modified atmosphere (MA) of polyethylene bag. Based on 1ºC, storage temperature was set four fluctuation values: 1 ± 0ºC, 1 ± 0.5ºC, 1 ± 1ºC and 1 ± 2ºC. Results indicate that postharvest quality of peach under temperature without any fluctuation (1 ± 0ºC) was effectively maintained by reducing respiration rate and polyphenol oxidase activity. The total soluble solid content and superoxide dismutase activity were considerable high at constant temperature. Temperature fluctuations were not conducive to quality maintenance of peach during storage. The combination of constant temperature and MA significantly hold the pulp firmness and overall sensory quality. Peaches were suitable for MA storage of polyethylene (PE) bag, in comparison to CA storage of 10% O2. The present study provided a theoretical basis for peach during cold storage (CS). Practical applications Peach fruit ripen and deteriorate quickly at ambient temperature. CS, CA and MA are effective methods to slow ripening and reduce decay development after harvest. The reliability of atmosphere packaging depends on rigorous temperature control. However, temperature is not always constant during transportation and storage, and temperature fluctuation (TF) means an alteration in fruit respiration and gas transmission. Because of its high metabolic activity, peach is sensitive to TF particularly. The aim of this study is to evaluate the effect of TF treatment combining with CA or MA on quality characteristics of peach. In general, peach was suitable for storage in MA of PE bag and the storage temperature without any fluctuation could delay ripening and improve the edible quality of peach.

Pomegranate (Punica granatum) is a non-climacteric fruit susceptible to chilling injury (CI) at temperatures below 5 °C. To understand the influences of ethylene and modified atmosphere on CI physiological disorders of pomegranate, exogenous ethrel (0.5, 1 and 1.5 µg L-1 ) treatments, 1-methylcyclopropene (1-MCP) (1 µL L-1 ) exposure, packaging in a modified atmosphere (MAP) (XTend™ bags; StePac, São Paulo, Brazil), a MAP/1-MCP combination, and packaging in macro-perforated bags (MPB) were applied. The treated fruits were cold stored (2 ± 1 °C; 85% relative humidity) and sampled during 120 + 3 days at 20 °C. During cold storage, CI symptoms started at 20 days in MPB and at 60 days for all exogenous ethylene treatments, and were delayed to 120 days in MAP, 1-MCP and MAP/1-MCP treatments. MPB and ethylene treatments induced significant electrolyte leakage, oxidative damage, lipid peroxidation, ethylene and CO2 production, and 1-aminocyclopropane-1-carboxylic acid oxidase activity, without any change in total soluble solids, titratable acidity or skin and aril colours. Conversely, MAP by itself, or in combination with 1-MCP application, effectively delayed CI symptoms. During long-term cold storage of this non-climacteric fruit, ethrel application induced endogenous ethylene biosynthesis, accelerating the appearance of CI symptoms in contrast to the observations made for MAP and 1-MCP treatments. © 2018 Society of Chemical Industry.

Controlled atmosphere (CA) has been used to alleviate chilling injury (CI) of horticultural crops caused by cold storage. However, the effects of CA treatment on peach fruit sensory quality and flavor-related chemicals suffering from CI remain largely unknown. Here, we stored peach fruit under CA with 5% O2 and 10% CO2 at 0 °C up to 28 d followed by a subsequent 3 d shelf-life at 20 °C (28S3). CA significantly reduced flesh browning and improved sensory quality at 28S3. Though total volatiles declined during extended cold storage, CA accumulated higher content of volatile esters and lactones than control at 28S3. A total of 14 volatiles were positively correlated with consumer acceptability, mainly including three C6 compounds, three esters and four lactones derived from the fatty acid lipoxygenase (LOX) pathway. Correspondingly, the expression levels of genes including PpLOX1, hyperoxide lyase PpHPL1 and alcohol acyltransferase PpAAT1 were positively correlated with the change of esters and lactones. CA elevated the sucrose content and the degree of fatty acids unsaturation under cold storage, which gave us clues to clarify the mechanism of resistance to cold stress. The results suggested that CA treatment improved sensory quality by alleviating CI of peach fruits under cold storage.

Effects on Physiological Disorders

Effect of a low oxygen atmosphere combined with 1-MCP pretreatment on preserving the quality of ‘Rojo Brillante’ and ‘Triumph’ persimmon during cold storage

Sorbitol immersion controls chilling injury in CA stored ‘Palmer’ mangoes

Mature ‘Barhy’ date fruits (Phoenix dactylifera L.) were stored under different storage temperatures (0, 2, 4, 6°C) under modified atmosphere (MA) conditions with 0.03, 5, 10, or 20% carbon dioxide concentrations (balance air). Fruit total phenolic content (TPC), flavonoids content, carotenoids content, total sugar %, SSC %, and fruit skin color (L*a*b*c* and h*) were determined. Total phenolic content (TPC) was determined by the Folin-Ciocalteu method, and antioxidant capacity was determined using ferric reducing antioxidant power (FRAP). A clear integration was observed between modified atmosphere and cold storage treatments regarding maintaining fruit quality during the storage period. Fruits stored under low temperature conditions (0°C) or relatively high CO2 concentration (20% CO2) did not show any chilling or CO2 injury symptoms. Fruits kept under MA conditions with 20% CO2 at cold storage (0°C) showed brightest yellow color, and highest storage ability among all stored fruits. All MA conditions investigated extended date storability by maintaining fruit quality. The effect of MA conditions on maintaining fruit quality was magnified when fruits were stored under cold temperature. Fruit quality was maintained for 173 days when stored in 20% CO2 at 0°C, whereas it did not exceed 60 days when stored under common air composition (containing 0.03% CO2) at 0°C. Treatments with high CO2 concentrations (20% CO2) under cold storage conditions (0°C) maintained fruit total phenolic content, SSC%, total sugar content, and total tannins.

The effect of deficit irrigation of olive trees on fruit total phenol content and chilling injury during cold storage was examined. 'Konservolea' and 'Chondrolia' olive trees were irrigated based on the farmer's decision (control, exceeding 100% evapotranspiration) or deficit irrigated during stone hardening and final flesh swelling (irrigation water around 50% of control). Green olive fruit quality was evaluated at harvest and every week plus 1 day shelf life during 4 or 5 weeks storage at 5°C and included skin color, flesh firmness, % flesh dry matter, total phenol content and chilling injury (CI) symptoms. CI was subjectively evaluated as discoloration of flesh and skin due to injury and not due to ripening. In `Konservolea' olives, skin color darkened after long storage due to internal CI (flesh browning), while there were no significant differences in total phenol content and CI during most of the measurements in fruits from control or deficit irrigated trees. In contrast, total phenol content in deficit irrigated 'Chondrolia' olives was higher at harvest and until the development of significant CI than control irrigated fruit, while a similar trend was found in CI early in storage between the two treatments. In the same cultivar, fruit total phenol content decreased with time in cold storage as severe CI symptoms appeared. 'Konservolea' green olives had lower total phenol content and sensitivity to low temperature storage compared to 'Chondrolia' green olives. These data could relate olive fruit total phenol content to CI sensitivity during cold storage.

Evaluation of storage temperatures to astringency ‘Giombo’ persimmon: Storage at 1 °C combined with 1-MCP is recommended to alleviate chilling injury

Fruit of ‘Fuyu’ persimmon ( Diospyros kaki L.) were harvested from commercial orchards and stored in 1984–1986. Fruit maturation varied considerably between the three seasons, in particular in the relationship between soluble solids concentration, loss of astringency, and colour development. Development of chilling injury (CI) in fruit during storage varied with season, harvest time, and storage treatment. Fruit harvested in 1984 stored longer without CI at 0°C than fruit harvested in 1985 or 1986. In 1986 fruit harvested late in the season had less CI than those harvested early. Both preconditioning of fruit and storage in a modified atmosphere (MA) formed by polyethylene bags (polybags) ameliorated chilling damage. Respiration rates of fruit held at 20 °C after 0°C storage closely correlated with chilling damage; injured fruit showed higher respiration rates. Fruit stored in MA showed a relationship between oxygen level during cool storage and development of CI; high O 2 levels (14–20%) allowed greater CI. Fruit stored at 4°C developed more severe CI than those stored at 0°C. New Zealand grown ‘Fuyu’ will store at 0°C for at least 4 weeks in MA polybags. This is a much shorter storage time than that for Japanese grown ‘Fuyu’. The occurrence of chilling injury in New Zealand grown ‘Fuyu’ may be related to an effect of climatic conditions on fruit development, with tree age perhaps playing a secondary role.

The quality of Gold Queen Hami melons stored under different temperatures