Non-chilling Temperatures Research Articles

The role of respiratory metabolism in chilling injury development of Chinese olive fruit during cold storage

Chilling injury (CI) and browning occurrence are pivotal issues during the cold storage of postharvest Chinese olive fruit. This study evaluates the effects of non-chilling temperature (8 °C) and chilling temperature (2 °C) on CI development, browning occurrence, and respiratory metabolism in postharvest Chinese olives. Compared to storage at 8 °C, storage at 2 °C significantly induced CI, accompanied by higher indices of CI and browning, as well as a higher fruit respiratory rate. Storage at 2 °C increased the activities of phosphohexose isomerase (PGI), succinate dehydrogenase (SDH), ascorbic acid oxidase (AAO), and cytochrome C oxidase (CCO) by 55.1%, 11.1%, 26.4%, and 98.8%, respectively, on day 120. On the other hand, storage at 2 °C reduced the activities of NAD kinase (NADK), 6-phosphogluconate dehydrogenase (6-PGDH) + glucose-6-phosphate dehydrogenase (G-6-PDH) by 95.6% and 6.6%, respectively, on day 120. The contents of nicotinamide adenine dinucleotide (NAD) and its reduced form of NAD (NADH) increased by 10.0% and 22.8%, respectively, in fruit stored at 2 °C on day 120. Conversely, the contents of nicotinamide adenine dinucleotide phosphate (NADP) and its reduced form (NADPH) decreased by 58.3% and 64.4%, respectively, in fruit stored 2 °C on day 120. These findings indicate that CI development and browning occurrence in Chinese olives induced by storage at 2 °C were associated with a higher respiratory rate, increased activities of PGI, SDH, AAO, and CCO, higher contents of NAD(H), reduced activities of 6-PGDH + G-6-PDH, and lower contents of NADP(H).

Delaying ripening using 1-MCP reveals chilling injury symptom development at the putative chilling threshold temperature for mature green banana.

Storage at the putative chilling threshold temperature (CTT) to avoid chilling injury still limits postharvest handling of tropical fruit like banana in that ripening may occur at the CTT. To determine whether chilling injury (CI) symptoms would develop in mature green (MG) banana fruit if the CTT exposure was extended by inhibiting ethylene action and thus ripening, 1-methylcyclopropene (1-MCP) was applied. Individual ‘fingers’ from multiple ‘clusters’ of MG bananas were either immersed in water or 50 μg L−1 1-MCP (a.i.) solution and each treatment was divided into three subgroups for storage at 5.0°C (severe CI), 13.0°C (mild CI), or 14.0°C (CTT) ± 0.1°C. 1-MCP delayed ripening in terms of color change for 10 days for fruit stored at the CTT. Ethylene production by fruit at 5.0°C remained around 0.04 ng kg−1 s−1 with no obvious increase during 31-day storage. Ethylene production at 14.0°C (−1-MCP/+1-MCP) increased on Day 33 while increasing on Day 38 for 13.0°C fruit without 1-MCP and on Day 39 for fruit with 1-MCP. Peak climacteric ethylene occurred on Days 44 and 39 for 13.0 and 14.0°C fruit without 1-MCP, respectively, and on Days 59 and 51 for 13.0°C and 14.0°C 1-MCP-treated fruit, respectively. As hypothesized, longer exposure of MG banana fruit to the CTT of 14.0°C without onset of ripening as was allowed by prior 1-MCP treatment allowed CI to develop at that normally non-chilling temperature. Vascular browning was the first visual and most sensitive CI symptom in the experiment and was observed on Day 4 at 5.0°C, Day 10 at 13.0°C, Day 19 at 14.0°C without 1-MCP, and on Day 28 at 14.0°C with 1-MCP. Using a 1-MCP pre-treatment to remove the influence of ethylene from bananas stored at 13°C or 14°C also resulted in slight reduction in vascular browning severity. In conclusion, a putative safe temperature may become a CI temperature if the shelf-life-limiting factor is removed, allowing longer exposure. Chilling at the CTT caused relatively mild injury on fruit, and vascular browning is a sensitive indicator of CI status, while the light-adapted quantum yield of photosystem II [Y(II)] could be a non-destructive indicator of early CI stress in MG banana. Fruit at 13.0/14.0°C developed CI symptoms slightly later with 1-MCP than without 1-MCP. This suggests that ethylene might be involved in early CI symptom development.

Melatonin Treatment of Apricot Trees Leads to Maintenance of Fruit Quality Attributes during Storage at Chilling and Non-Chilling Temperatures

The effects of preharvest melatonin treatment on apricot crop yield and fruit quality properties at harvest and during storage have not yet been investigated. Apricot trees, of the ‘Colorado’ and ‘Mikado’ cultivars, were sprayed with 0.1 mM melatonin at three key points of fruit development. Fruit were harvested at commercial ripening stage and yield was higher in melatonin treated trees than in the controls. Fruit were stored at 1 and 8 °C for 21 and 28 days, respectively. Samples were taken weekly and left at 20 °C for 1 day. Weight losses, as well as reduction in firmness and acidity, were delayed in fruits from melatonin treated trees, showing an effect of treatment on delaying the postharvest ripening process, which was attributed to a reduced ethylene production in both cultivars and at both storage temperatures. In addition, chilling injury symptoms were observed in apricots stored at 1 °C, which were reduced by preharvest melatonin treatment. Moreover, apricot from melatonin-treated fruit retained higher total phenolic content than the controls after 14 days of storage, although the phenolic profile was not affected by treatment. Thus, melatonin could be a useful tool for practical purposes to improve apricot crop yield and maintain fruit quality properties during storage.

Effects of 1­methylcyclopropene treatment on quality and anthocyanin biosynthesis in plum (Prunus salicina cv. Taoxingli) fruit during storage at a non-chilling temperature

Abstract The effects of 1­methylcyclopropene (1-MCP) treatment on the quality attributes of ‘Taoxingli’ plum fruit, particularly on whole fruit anthocyanin content via anthocyanin biosynthesis during storage at the non-chilling temperature of 10 °C were investigated. The results showed that 1-MCP treatment effectively reduced weight loss and better maintained soluble solids content (SSC) and titratable acidity (TA), resulting in increased contents of fructose, glucose, sorbitol, and malic acid, and reduced decay during storage. Furthermore, major anthocyanins, including cyanidin 3-O-glucoside and cyanidin 3-O-rutinoside, were detected. 1-MCP treatment delayed increases in total anthocyanins along with the major individual anthocyanins during storage, which was attributed to its effect in suppressing the expression of synthesis-related structural genes and the transcription factor PsMYB10 early in storage, enhancing their expression later in the storage period. Thus, 1-MCP treatment was beneficial for retaining the quality of ‘Taoxingli’ plums, particularly the chemical attributes, and extending the storage life with low economic loss during storage.

Canopy Position Affect Rind Biochemical Properties of ‘Marsh’ Grapefruit during Postharvest Cold Storage at Non-chilling Temperature

ABSTRACT Effect of canopy position on rind biochemical properties of ‘Marsh’ grapefruit during postharvest non-chilling cold storage was evaluated on fruit harvested from different orchard locations. Inside canopy (IC) and outside canopy (OC) fruits were harvested at commercial maturity from two commercial farms located at KwaZulu-Natal (KZN) and Limpopo (LMP), South Africa, during two seasons. Rind biochemical analyses including color indices, total phenolic concentration, and sugars were performed on harvested grapefruit after Weeks 0, 3, 6, and 9 of cold storage at 7.5 ± 0.5°C. Canopy position showed a high significant (p < .001) effect on rind biochemicals while significant (p < .05) influence of orchard locations was observed on the same parameters. Reducing sugars were more concentrated in IC fruit harvested from both orchard location than OC fruit at Weeks 0 and 3, but inverse results occurred at Weeks 6 and 9. Orchard location significantly (p < .001) influenced vitamin C (14.4, 14.2, 14.4, 14.8 g kg−1) and (12.3, 16.1, 15.9, 14.6 g kg−1) of fruit rind at Weeks 0, 3, 6, and 9 from KZN and LMP, respectively. This study revealed that canopy position can influence rind biochemical properties of ‘Marsh’ grapefruit during non-chilling postharvest cold storage. However, further studies are required to formulate and provide the citrus industries with adequate advice.

Heat treatment effects on chilling injury and disease incidence in sweet orange fruits stored at chilling and non-chilling temperatures

Citrus chilling injury causes 25% postharvest losses by shortening its storage life and lowers its market value in developed countries. In citrus fruits, chilling injury is characterized by increased moisture loss and disease susceptibility. The present study was conducted with the objective to evaluate the effects of pre-storage heat treatments (HTS: control, 5, 10, 15 and 20 min), heat treatment methods (HTM: wet heat treatment [WHT], vapor heat treatment [VHT]), and exposure temperatures (ET: chilled [2.5 °C], non-chilled [10 °C]) on citrus fruits (cv. Blood Red having sour orange rootstock) during 2015–2016 at the University of Agriculture, Peshawar, Pakistan. Sweet orange fruits and fruit discs of 10 mm diameter were simultaneously treated with WHT and VHT. The heat treated fruits and fruit discs were separated into two lots. One lot was held at non-chilling temperature (10 ± 1 °C), while the other lot was exposed to chilling temperature (2.5 ± 1 °C) for 75 days and packed in fiber board packages. The fruits and fruit discs after 75 days storage at both storage temperatures (10 ± 1 °C and 2.5 ± 1 °C) were incubated at ambient temperature for 7 days (simulated marketing time) and analyzed for different chilling injury parameters. Heat treatment periods (HTS), exposure temperature (ET) and their interactions (HTS × ET) showed significant (p ≤ 0.05) differences for the majority of the traits. The interaction of HTS × HTM was significant (p ≤ 0.05) for weight loss and surface pitting. However, heat treatment methods (HTM) and interaction of ET × HTM × HTS was significant for surface pitting and weight loss, respectively. The non-chilled (10 ± 1 °C) fruits revealed lower weight loss (6.80%), surface pitting (4.40%), disease incidence (7.07%), disease expansion (3.97 mm), ion leakage (15.77%) while the ascorbic acid increased (32.38 mg 100 g−1). However, chilling (2.5 °C) triggered the increase in weight loss (8.32%), surface pitting (16.13%), disease incidence (14.59%), lesion diameter (10.37 mm) and ion leakage (27.96%) in sweet orange. Heat treatments with WHT and VHT for 5–10 min resulted in reduced weight loss (6.07%), surface pitting (3.33%), disease incidence (2.00%), disease expansion (5.00 mm) and ion leakage (20.23%) in sweet oranges. Heat treatments with WHT and VHT for 15–20 min, accelerated the fruit senescence by increasing the weight loss (8.98%), surface pitting (15.67%), disease incidence (15.33%), disease expansion (8.33 mm) and ion leakage (23.62%). In comparison to heat treatment methods, highest weight loss (7.57%), surface pitting (11.53%), ion leakage (21.94%) and disease incidence (10.86%) were recorded in VHT, whereas WHT treatments had lowest weight loss (7.55%), surface pitting (9.00%), ions leakage (21.80%) and disease incidence (10.79%). Therefore, modest WHT pre-storage heat treatment (5–10 min) is recommended for storage of sweet orange.

Storability, Quality Changes, and General Postharvest Behavior of Dudaim Melon Harvested at Two Maturity Stages

Dudaim melon (Cucumis melo Group Dudaim) is a unique edible melon for which few postharvest physiology studies have been conducted. To investigate the postharvest behavior of dudaim melon, two cultivars (Zangi-Abad and Kermanshah) were planted, tagged at anthesis, and harvested at two maturity stages: 21 and 28 d after anthesis (DAA). Harvested fruit were stored at 5 or 13 °C for up to 3 weeks and various quality parameters including color, firmness, titratable acidity (TA), total soluble solids (TSS), weight loss, chilling injury (CI), ethylene production, protein content, glucose content, fructose content, sucrose content, and maltose content were assessed during storage. After 3 weeks of storage at 13 °C, early-harvested fruit (21 DAA) had relatively similar color values (L*, lightness; a*, green–red tones; b*, blue–yellow tones) and TA compared with late-harvested fruit (28 DAA); however, some quality traits, such as TSS, were not similar. Ethylene content decreased initially after harvest and then started to increase during storage at 13 °C. For most treatments, glucose and fructose contents decreased whereas sucrose and maltose contents increased with advancing maturity. Increased ethylene production, in concert with color development at 13 °C, similar to ripe fruit, and the changing balance of measured mono- and disaccharide sugars in harvested fruit likely indicates ‘Kermanshah’ is climacteric. Results for ‘Zangi-Abad’ were not as definitive. Dudaim melon fruit can be harvested at an optimum stage of maturity, similar to known climacteric melon fruit, and then allowed to ripen at proper storage temperatures before consumption. Based on the results of this study, we recommend that harvest at 21 DAA and storage at a nonchilling temperature such as 13 °C are the optimal stage and temperature for long storage purposes.

Expression of antioxidant-related genes in flavedo of cold-stored grapefruit (Citrus paradisi Macfad cv. Rio Red) treated with pectic oligosaccharides

Cold storage is one of the main postharvest technologies for fruit preservation, however, cold-sensitive citrus fruits develop peel physiological alterations affecting external quality known as chilling injury (CI). An efficient antioxidant system has been associated to an enhanced cold stress tolerance in citrus fruits. The application of pectic oligosaccharides (POs) stimulates the enzymatic antioxidant system in plants and reduces CI development in grapefruit fruit (Citrus paradisi) during cold storage. The aim of this study was to contribute to the basic understanding of peel physiological disorders in cold-stressed ‘Rio Red’ grapefruit fruit at ultrastructural level and to determine whether the POs are involved in the CI reduction by modulating the antioxidant enzymatic system at the transcriptional level. Peel morphology in grapefruit fruit stored at chilling (2 °C) and non-chilling (13 °C) temperatures was analyzed by electronic microscopy and the effect of POs treatment on manganese superoxide dismutase (MnSOD), ascorbate peroxidase (APX1), catalase (CAT1) and glutathione reductase (GR2) gene expression was investigated by RT-qPCR. Results indicate that a prolonged cold storage promoted the incidence of CI symptoms in 'Rio Red' grapefruit and altered the ultrastructural morphology of flavedo epidermal tissue. POs significantly modulated the MnSOD, APX1 and CAT1 expression levels mainly in a storage time- and temperature-dependent manner with regards to controls. By contrast, POs only significantly affected the GR2 gene expression when grapefruit were stored at non-chilling temperatures. Our results revealed a possible involvement of the MnSOD, APX1 and CAT1 genes in the CI susceptibility reduction induced by POs in ‘Rio Red’ grapefruit stored at chilling temperatures.

Ripening Recovery and Sensory Quality of Pink Tomatoes Stored in Controlled Atmosphere at Chilling or Nonchilling Temperatures to Extend Shelf Life

Harvesting before ripening initiation (i.e., mature green) may negatively affect the flavor of fresh tomatoes (Solanum lycopersicum) even though the ripening process off the vine is physiologically the same as that on the plant. Low temperature storage at or below the putative chilling injury (CI) threshold can also have detrimental effects on fresh tomato flavor regardless of the developmental stage of the fruit at harvest, but sensitivity to CI declines with ripening. Controlled atmospheres (CA) using reduced oxygen and elevated carbon dioxide partial pressures can extend the shelf life (SL) of tomatoes while possibly minimizing the negative effects of low temperatures. In this study, we explored the possibility that a combination of temperature and CA could be used to achieve similar SL for pink-harvested tomatoes as has been found in other studies with green-harvested fruit while avoiding the negative effects of CI on sensory quality. Consumer panels were given samples of pink-harvested tomatoes after they had reached the red ripeness stage in terms of surface hue following storage for 7 days in air or CA at 7.5, 15, or 20 °C followed by 2–7 days ripening in air at 20 °C. Exposing pink tomatoes to 7.5 °C before ripening to the full-red stage at 20 °C negatively affected fruit sensory quality, holding fruit constantly at 20 °C until they reached the full-red stage resulted in better quality for one taste panel, whereas there was no difference in another taste panel. The time to reach the full-red stage was extended by CA. Sensory quality of air- and CA-stored fruit was similar at the nonchilling temperatures of 15 and 20 °C. Pink stage tomato fruit stored in CA at 7.5 °C for 7 days did not attain full red color within the subsequent 7 days in air at 20 °C.

Role of canopy positions on rind biochemical concentrations and radical-scavenging activities in relation to rind breakdown of ‘Nules Clementine’ mandarins stored at non-chilling temperature

Abstract Rind biochemical concentrations and radical-scavenging activities of ‘Nules Clementine’ mandarin could play a significant role in the susceptibility of the fruit to various forms of physiological rind disorders. This study examined the effect of fruit position within tree canopy on biochemical concentrations and radical-scavenging activities of ‘Nules Clementine’ mandarin fruit rind after harvest at week 0 and after 3, 6 and 9 weeks of postharvest cold storage at 7.5 ± 0.5 °C. Biochemical concentrations and radical-scavenging activities of flavedo and albedo tissues of the rind were also examined. Fruit from inside canopy (IC) and outside canopy (OC) were harvested at commercial maturity in May 2015 and 2016 from Unifruiti and Swartvelei Farms located at Eastern Cape (EC) (33° 27′ 32″ S, 25° 34′ 79″ E) and Western Cape (WC) (19° 02′ 33.8″ S, 33° 41′ 17.24″ E) provinces of South Africa, respectively. Results showed that canopy position played a significant ( p 0.001) role on total carotenoids, total phenolics and total flavonoids as well as rind dry matter, with OC fruit often characterised by higher biochemical concentrations than IC fruit during cold storage. The study further showed that production region influenced radical-scavenging activities and carbohydrate content of OC and IC fruit rind during cold storage. Radical-scavenging activities of OC fruit (61.2%) were higher than IC fruit (52.5%) from EC whereas radical-scavenging activities of IC fruit (67.1%) were higher than those of OC fruit (58.2%) from WC at harvest. Overall, this study revealed that fruit position within tree canopy influenced its rind biochemical concentrations and radical-scavenging activities.

The effect of postharvest storage temperature on sweet cherry (Prunus avium L.) phenolic metabolism and colour development

Abstract Sweet cherry storage at 1 °C significantly affected many biochemical parameters linked to anthocyanin concentration in fruits and subsequently their colour. While no significant differences in the concentration of total phenolics were detected among treatments, total anthocyanin concentration and phenylalanine ammonia-lyase enzyme activity, as well as the transcription of anthocyanidin synthase and flavonol 3-O-glucosyltransferase (genes coding for enzymes fundamental for the anthocyanin synthesis) were considerably lower in fruits stored at 1 °C (with or without a 24-h period of storage at 20 °C) in comparison to the initial fruits at harvest. In contrast, the fruits stored continuously at 20 °C exhibited higher levels of total anthocyanins and Phenylalanine Ammonia-Lyase activity and also elevated expression of the genes coding for enzymes involved in the biosynthesis of anthocyanins in comparison to fruits that underwent cold storage. Our results suggest that cold storage of sweet cherries at low, but non-chilling temperatures, decelerates the accumulation of anthocyanins and consequently causes slower colour development in fruits.

Changes in visual quality, physiological and biochemical parameters assessed during the postharvest storage at chilling or non-chilling temperatures of three sweet basil (Ocimum basilicum L.) cultivars.

Leaves of three different sweet basil (Ocimum basilicum L.) cultivars (Italico a foglia larga, Cammeo, and Italiano classico) packed in macro-perforated polyethylene bags were stored at chilling (4°C) or non-chilling temperature (12°C) for 9days. During storage, visual quality, physiological (respiration rate, ethylene production, ammonium content) and chemical (antioxidant activity, total polyphenols and polyphenol profile) parameters were measured. Detached leaves stored at chilling temperature showed visual symptoms related to chilling injury, while ethylene production and ammonium content resulted associated to cultivar sensibility to damage at low temperature. Storage at 4°C caused a depletion in polyphenols content and antioxidant capability, which was preserved at 12°C. Regarding the polyphenols profile, stressful storage conditions did not enhance the phenolic metabolism. However, leaves stored at 12°C did not loss a significant amount of metabolites respect to fresh leaves, suggesting the possibility to extend the storability after the expiration date, for a possible recovery of bioactive compounds.

Pectic and Galacturonic Acid Oligosaccharides on the Postharvest Performance of Citrus Fruits

Orange [Citrus sinensis (L.) Osbeck] and grapefruit (Citrus paradisi Macfad) citrus fruits are prone to develop different peel physiological disorders caused by storage at both chilling and nonchilling temperatures. The effect of galacturonic acid oligosaccharides (GAOs) and pectic oligosaccharides (POs) in reducing postharvest nonchilling peel pitting (NCPP), decay, and chilling injury (CI) in orange cv. Navelina and the effect of POs in reducing CI in grapefruit cv. Rio Red, were investigated. The incidence of these disorders was examined in fruits stored at chilling and nonchilling temperatures and at 90% to 95% relative humidity (RH). POs showed a better efficacy than GAOs in reducing postharvest losses in orange. The POs were able to reduce NCPP and decay in ‘Navelina’ fruits stored at 20 °C, irrespective of the fruit maturity stage. The application of 10 g·L−1 POs also reduced CI and the chilling-induced ethylene production in oranges and grapefruits maintained at the chilling temperature. Likewise, the decrease in ethylene production found in ‘Navelina’ fruits that developed NCPP during storage at the nonchilling temperature was related to lower peel damage. Moreover, results showed that POs do not induce an increase in ethylene when fruit are stored under conditions that do not cause stress-related injury to fruit. Therefore, POs efficacy in reducing postharvest physiological disorders is not likely mediated by ethylene. Overall results indicate that the application of POs may be an acceptable alternative to mitigate postharvest losses of citrus fruits.

Proteomic analysis of postharvest peach fruit subjected to chilling stress or non-chilling stress temperatures during storage

Proteome patterns from peach fruit subjected to chilling stress (5°C) and non-chilling stress (10°C) temperatures were compared by 2-dimensional gel electrophoresis (2-DE) and MALDI-TOF/TOF mass spectrometry. Among the 60 differentially expressed proteins detected by 2-DE, those involved in stress response and defense were the most abundant. Proteins associated with membrane stability, as well as sucrose content were reduced in fruit stored at 5°C, possibly contributing to the development of chilling injury (CI) seen at 5°C. In addition, small heat shock proteins and components of the antioxidant defense system were expressed at higher levels under chilling stress. In contrast, storage at non-chilling temperature (10°C) promoted the softening of peach fruit accompanied by increased levels of expansin and pectate lyase. The expression of pathogenesis-related proteins also increased at 10°C, in parallel with the relatively higher incidence of decay observed at this temperature.

A Comparative Proteomics Analysis of Soybean Cotyledon and Unifoliolate Leaves Under Heat (Chilling) Treatments

To understand the cold stress response of soybean, 480 soybean germplasms were used to find the tolerant and sensitivity of germplasm to cold. Then a comparative proteomic analysis between soybean seed treated at chilling and non-chilling temperature was carried out using the tolerant cold soybean germplasm. During the germination of seed, it was possible to discriminate between proteins involved in symptoms and proteins implicated in response to chilling. A proteomic approach, based on two-dimensional electrophoresis and MALDI-ToF-MS peptide mass fingerprinting experiments, was used for this purpose. The comparison of the resulting proteomic maps highlighted proteins showing quantitative variations induced by temperature treatments. Twenty-nine protein spots exhibited significant quantitative changes under at least one stress condition. Identified, differentially represented proteins belonged to two main broad functional groups, namely energy production/carbon metabolism and response to abiotic and oxidative stresses. In addition, our data seem to indicate a possible candidate to be used as a protein marker for further studies on cold stress.

Benzyl-aminopurine (BAP) treatments delay cell wall degradation and softening, improving quality maintenance of refrigerated summer squash

Round summer squash are harvested before reaching full maturity and even though they are highly perishable, fruit postharvest handling is mostly based on storage at non-chilling temperatures. Finding complementary treatments minimizing deterioration and reducing postharvest losses would be extremely useful. In this work we evaluated the effect of postharvest cytokinin (CK) treatments on refrigerated round soft rind squash. Fruit were harvested at commercial maturity and sprayed with 1mmolL−1 benzylaminopurine (BAP) or water (control) prior to storage at 5°C for 0, 13 or 25 days. Quality was assessed upon removal from cold storage as well as after a 2 day shelf-life period at 20°C. CK-treated fruit showed slower deterioration and dehydration and remained firmer than the control. BAP sprays did not affect color, respiration or sugar-acid balance. The treatments prevented phenolic compound accumulation, and decreased pectin solubilization. By the end of the storage period BAP-treated squash had higher levels (45%) of tightly-bound polyuronides than untreated controls, indicating a substantial delay in cell wall dismantling. CK sprays also reduced neutral sugar solubilization from pectin-rich fractions, but no changes were found in the cross-linking glycans or cellulose. To our knowledge, this is the first work showing that CK can regulate pectin disassembly in developing fruit. Postharvest BAP sprays preventing texture deterioration may be a simple treatment to complement refrigeration of round, soft rind, summer squash.

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

‘Goldfinger’ bananas (Musa accuminata, FHIA-01) were harvested, held for 14–22d 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.

Influence of fruit maturity in the susceptibility of Navelina oranges to develop postharvest non-chilling peel pitting

Peel pitting is a disorder occurring mostly during postharvest storage at non-chilling temperatures in different varieties of citrus fruit and consists in collapse of flavedo and albedo tissues that may affect oil glands. It has been demonstrated that during postharvest, sharp variations in water potential of cells from flavedo and albedo are sufficient to provoke fractures in cell walls from external albedo resulting in tissue collapse. However, morphology and composition of cells and cell walls in flavedo and albedo varies during fruit maturation and this may affect water flow through the different fruit peel layers and susceptibility of fruit to develop peel pitting. In this paper, we have studied the influence of the stage of maturation in the susceptibility of Navelina orange to develop peel pitting. Except in mature-green fruit, peel pitting increased with maturation after transferring fruit from 45% to 95% relative humidity and was also more severe as more dehydrated was the tissue before transference. Also, differences in water potential of fruit maintained at 45 or 95% relative humidity increased as fruit matured, suggesting that tissue reduces the ability of water adjustment during maturation. In this sense, only mature-green fruit flavedo was able to recover water potential when transferred from 45 to 95% relative humidity. Ethylene production upon transfer from low to high relative humidity increased only in mature tissue and was rapid and transient, and before initial symptoms of peel pitting. Flavedo and albedo water potential (ψw) was substantially reduced during fruit maturation. As lower was the ψw of freshly harvested fruit, minor variations were observed by changes in the storage relative humidity and higher the induced damage. Therefore, the increasing susceptibility of Navelina fruits to develop peel pitting with fruit maturation may be related to a reduced ability to regulate peel evapotranspiration and osmotic adjustment during postharvest storage.

The effects of fruit maturation, delayed storage and ethylene treatment on the incidence of low‐temperature breakdown of ‘Hayward’ kiwifruit

Low-temperature breakdown (LTB), a disorder inducing quality loss, during and after cold storage of 'Hayward' kiwifruit was investigated. Harvested kiwifruits during fruit maturation or after delayed storage (DS) at 20 °C for 0, 1, 2, 3 and 4 weeks and 1 µL L⁻¹ ethylene treatment for 24 h were stored at -0.5 °C for 24 weeks and additional ripening at 20 °C for 5 days. Fruit quality indices and LTB incidence and severity were determined before and after treatments. Harvested fruits ripened during maturation, DS and after ethylene treatment. After storage and shelf life, fruits of all treatments were at complete ripening stage. LTB incidence of early harvested fruits was high, while that of fruits of the mid (third) and late harvests was low. Fruits of the third harvest date showed progressively increased LTB incidence with increasing duration of DS to as high as 95-100% after 4 weeks. Ethylene-treated fruits showed a comparable increase in LTB to that corresponding to 2-3 weeks of DS. In contrast to fruit maturation, postharvest (after harvest and before storage) DS at non-chilling temperature and ethylene treatment advanced the ripening of 'Hayward' kiwifruit and resulted in increased LTB incidence.

Proteome Changes in Tomato Fruits Prior to Visible Symptoms of Chilling Injury are Linked to Defensive Mechanisms, Uncoupling of Photosynthetic Processes and Protein Degradation Machinery

A comparative proteomic analysis between tomato fruits stored at chilling and non-chilling temperatures was carried out just before the appearance of visible symptoms of chilling injury. At this stage of the stress period it was possible to discriminate between proteins involved in symptoms and proteins implicated in response. To investigate the changes in the tomato fruit proteome under this specific stressful condition, two-dimensional differential in-gel electrophoresis coupled with spot identification by mass spectrometry was applied. This proteomic approach allowed the identification of differentially expressed proteins which are involved in two main biological functions: (i) defensive mechanisms represented by small heat shock and late embryogenesis proteins; and (ii) reaction to the uncoupling of photosynthetic processes and the protein degradation machinery. One of the first changes observed in chilled fruits is the down-regulation of ATP synthase, 26S proteasome subunit RPN11 and aspartic proteinase, whereas the first responses in order to deal with the stress are mainly multifunctional proteins involved not only in metabolism but also in stress regulation such as glyceraldehyde phosphate dehydrogenase, 2-oxoglutarate dehydrogenase and invertase. In addition, our data seem to indicate a possible candidate to be used as a protein marker for further studies on cold stress: aldose-1-epimerase, which seems to have an important role in low temperature tolerance.