Postharvest performance of the yellow-fleshed ‘Hort16A’ kiwifruit in relation to fruit maturation

Postharvest performance of fruit is dependent on the maturity or physiological state of the fruit at harvest in conjunction with the postharvest management applied. For yellow-fleshed kiwifruit, the flesh colour is a significant quality attribute, and for ‘Hort16A’, flesh colour has been used for timing harvest. Variability in the postharvest performance of ‘Hort16A’ kiwifruit suggests that flesh colour alone is not as strongly indicative of postharvest performance as soluble solids content (SSC) was found to be for ‘Hayward’ kiwifruit 30 years ago. The postharvest performance of ‘Hort16A’ kiwifruit, assessed as the fruit firmness and chilling injury expression during storage, has been associated with a range of fruit characteristics: flesh colour, SSC, firmness, seed colour, fresh weight, dry matter, starch and soluble carbohydrates measured at harvest throughout maturation. The changing responses of the fruit SSC to temperature, and softening to ethylene, have also been determined. The data illustrate the complex nature of ‘Hort16A’ fruit maturation, even when looking only at simple, easy-to-measure fruit attributes. While a yellow flesh colour is a commercial necessity for ‘Hort16A’ kiwifruit, flesh colour is not a robust indicator of postharvest performance and is not tightly linked to SSC or firmness. Changes in the capacity of fruit to respond to temperature or ethylene are not reflected in on-vine changes. Softening in storage is strongly linked to the softening rate occurring on the vine at the time of harvest. Any association between at-harvest characteristics and chilling susceptibility is less clear, and chilling tolerance appears more associated with the completion of growth and carbohydrate accumulation than with increased soluble solids accumulation rates as in ‘Hayward’. Approaches to extend the understanding of the link between maturation, harvest indices and postharvest performance are discussed.     

Characterization of ethylene biosynthesis and its regulation during fruit ripening in kiwifruit,Actinidia chinensis ‘Sanuki Gold’

Ethylene biosynthesis in kiwifruit, Actinidia chinensis ‘Sanuki Gold’ was characterized using propylene, an ethylene analog, and 1-methylcyclopropene (1-MCP), an inhibitor of ethylene perception. In fruit harvested between a young stage (66 days after pollination) (DAP) and an early commercial harvesting stage (143 DAP), 2 days of exposure to propylene were sufficient to initiate ethylene biosynthesis while in fruit harvested at commercial harvesting stage (154 DAP), 4 days of propylene treatment were required. This observation suggests that response of ethylene biosynthesis to propylene treatment in kiwifruit declined with fruit maturity. Propylene treatment resulted in up-regulated expression of AC-ACO1, AC-ACO2, AC-SAM1 and AC-SAM2, prior to the induction of AC-ACS1 and ethylene production, confirming that AC-ACS1 is the rate limiting step in ethylene biosynthesis in kiwifruit. Treatment of fruit with more than 5 μL L^?1 of 1-MCP after the induction of ethylene production subsequently suppressed ethylene production and expression of ethylene biosynthesis genes. Treatment of fruit with 1-MCP at harvest followed with propylene treatment delayed the induction of ethylene production and AC-ACS1 expression for 5 days. These observations suggest that in ripening kiwifruit, ethylene biosynthesis is regulated by positive feedback mechanism and that 1-MCP treatment at harvest effectively delays ethylene production by 5 days.     

The potential for commonly measured at-harvest fruit characteristics to predict chilling susceptibility of ‘Hort16A’ kiwifruit

The propensity for physiological disorders to arise during low temperature storage of kiwifruit is a significant commercial risk. The potential to use fruit characteristics (flesh colour, soluble solids content (SSC), dry matter and firmness) estimated non-destructively at harvest as markers for the susceptibility of ‘Hort16A’ kiwifruit to chilling injury (CI) has been investigated for individual fruit. While the fruit that developed CI during storage were some of the least advanced fruit on each orchard, the flesh colour, SSC, firmness and dry matter of the susceptible fruit differed considerably among orchards, such that there was not a clear minimum or maximum threshold for which fruit did or did not develop CI across all orchards. There was a large ‘orchard factor’ in the susceptibility of fruit to CI that was as important, if not more important, than the flesh colour, SSC, firmness and dry matter values. The ‘orchard factor’ may derive from a combination of environmental conditions and/or orchard management practices, in conjunction with fruit growth and development. Hence it is concluded that a generally applicable at-harvest prediction of ‘Hort16A’ fruit susceptibility to CI is not possible from an at-harvest non-destructive estimation of flesh colour, SSC, firmness and dry matter.     

Soluble solids accumulation and postharvest performance of ‘Hayward’ kiwifruit

A soluble solids content (SSC) of 6.2% has been used as a minimum harvest index for ‘Hayward’ kiwifruit for about 30 years. This paper describes a study that examines the pattern of soluble solids accumulation in ‘Hayward’ kiwifruit beyond the simple timing at which fruit reach 6.2% and investigates the relationship between soluble solids accumulation and postharvest performance assessed as softening and expression of chilling injury. This has been done using fruit from 10 orchards harvested at a range of SSC from 5 to 10% during one season. Soluble solids accumulation showed a general trend for a change from slow to more rapid accumulation during the season that could be described by a single logistic curve. The point at which the rate of soluble solids accumulation increased was more or less distinct for fruit from different orchards and occurred when fruit were at SSC between 6.3 and 7.4%. It is also possible that there is not a consistent change in soluble solids accumulation rate, with the rate being dependent on the environmental conditions over several days before measurement. There was a major change in softening pattern and low temperature breakdown susceptibility between fruit harvested at 6.4 and at 8.0% SSC. This change coincided with a change to faster soluble solids accumulation at harvest. It is concluded that the pattern, or rate, of soluble solids accumulation is likely to be a more robust indicator of the physiological state of the fruit, and therefore postharvest performance, than a single SSC value.     

Aloe vera based edible coatings improve the quality of minimally processed ‘Hayward’ kiwifruit

This article studies the efficacy of an edible coating based on Aloe vera gel at four different concentrations (0, 1, 5, 15% (v/v)) in maintaining the quality of fresh-cut kiwifruit. The kiwifruit slices were packaged under passive atmosphere and stored at 4 ± 1 °C. Quality attributes such as colour and texture (firmness and texture profile analysis), titratable acidity, total soluble solids, pectin content, microbial load and sensory parameters were evaluated during storage. In general, Aloe vera coating reduced respiration rates and microbial spoilage in sliced kiwifruit. After seven days of storage, the mesophilic load dropped by approximately one logarithmic unit for slices coated with 15% and 5% Aloe vera. Total pectin depolymerization was also lower in the treated samples and the texture of the uncoated samples deteriorated more rapidly than the treated slices during storage. Furthermore, due to the atmospheric composition and the microbial load, the quality of the control samples declined after six days of storage. Our results show that an Aloe vera coating improved the quality of stored kiwifruit slices. The best results obtained in the instrumental texture profile and in the preference panel test were with the 5% coating, indicating that this may be a healthy alternative coating for fresh-cut kiwifruit.     

Internal browning disorder and fruit quality in modified atmosphere packaged ‘Bartlett’ pears during storage and transit

Internal browning (IB) can be a serious problem with the use of modified atmosphere packaging (MAP) for ‘Bartlett’ pears (Pyrus communis L.) grown in the Pacific Northwest during storage and transit to distant markets. To investigate this disorder, ‘Bartlett’ pears harvested at commercial maturity were packed in a commercial MAP (MAPc), an experimental MAP (MAPe) and commercial perforated plastic bags (control) and stored in air at −1.1 °C. After 1 and 3 months of storage, samples of MAPc and control fruit were transferred to rooms at temperatures of 2, 4.5, 7.5, and 10 °C for 3 weeks to simulate transit temperatures and the time required to reach distant markets. MAPc maintained an average internal atmosphere of 12.3% O₂ + 5.6% CO₂ and significantly extended ‘Bartlett’ pear storage life with high eating quality and without IB and other disorders for up to 4 months at −1.1 °C. The internal gas atmosphere of MAPe equilibrated at 2.2% O₂ + 5.7% CO₂, which resulted in fruit with 25.5 and 62.3% IB after 3 and 4 months of storage, respectively. During simulated transit conditions of 2, 4.5, 7.5, and 10 °C, the CO₂ level in MAPc was maintained at 5.6–7.9%, while O₂ was reduced dramatically to 10.5, 5.0, 2.5, and 1.0%, respectively. IB developed at 7.5 and 10 °C but not at 2 and 4.5 °C, regardless of pre-transit storage duration (1 and 3 months) at −1.1 °C. The longer the storage duration and the higher transit temperature, the higher the incidence and severity of IB. The MAP-related IB disorder observed in this study included two types of symptoms: classic pithy brown core and wet brown flesh. The MAPc storage gas atmospheres maintained fruit firmness, color and higher eating quality after ripening, eliminated senescent scald and core breakdown, suppressed the loss of ascorbic acid (AsA) and titratable acidity, and slowed the accumulation of malondialdehyde (MDA) during storage at −1.1 °C for up to 4 months or 3 months + 3 weeks at simulated transit temperatures of 2 and 4.5 °C. In contrast, fruit held in MAP with low O₂ levels (1.0–2.5%) developed IB that appeared to be associated with a reduction in AsA, accumulated MDA and exhibited an increase in membrane leakage. MAP inhibited ripening at high CO₂ + high O₂ but lead to IB when the packaging material or elevated temperatures resulted in high CO₂ + low O₂ conditions. The incidence of IB closely correlated with lipid peroxidation and appeared to be related to fruit AsA concentration. The MAPc designed for pears appears to be suitable for ‘Bartlett’ fruit stored at −1.1 °C for up to 4 months or storage for 3 months and a transportation duration of up to 3 weeks at 0–4.5 °C during the early season and at 0–2 °C during the late packing season. These conditions yielded fruit of high eating quality and without IB or over-ripening upon arrival at distant markets.     

Changes in the mesocarp of Annona cherimola Mill. ‘Madeira’ during postharvest ripening

Physicochemical changes during postharvest ripening of cherimoya (Annona cherimola Mill. ‘Madeira’), were investigated to follow the principal modifications occurring during this process and to determine nutritional value. Fruit harvested at the mature green stage were analyzed during ripening using standard methods. Significant (P < 0.05) changes in chlorophyll, starch, titratable acidity, total free sugars and uronic acids were obtained, but no significant changes were found in ash, protein, lignin and lipid contents during ripening. The most obvious changes were chlorophyll degradation, an accentuated decrease of starch and an increase in total free sugars, with glucose the predominant sugar in the mesocarp, as revealed by GC analyses. Firmness loss was mainly attributed to depolymerization of pectin and lipid deterioration rather than hemicellulose degradation. Results also showed that the cherimoya variety evaluated in this study is a good source of minerals (mainly potassium), palmitic acid, linoleic acid, α-linolenic acid and sitosterol.     

Salt strategies to control Botrytis mold of ‘Benitaka’ table grapes and to maintain fruit quality during storage

Gray mold is the most common postharvest disease of table grapes in most regions of the world. The effect of eight salts, namely sodium silicate (SSi), sodium sulphate (SS), sodium carbonate (SC), sodium bicarbonate (SB), iron chelate (Fech), iron sulphate (FeS), ammonium bicarbonate (AB), and ammonium oxalate (AO) was determined in vitro on mycelial growth and spore suspension of Botrytis cinerea. In particular, SSi, SC, SB, FeS, and AB completely inhibited pathogen growth at 0.25% concentration. Six salt solutions at 1%, immersion or spray, were tested to verify their effect on grapes artificially inoculated with B. cinerea. All salts significantly reduced the percentage of gray mold as compared to control except for Fech after one week at 22 ± 1 °C. Three salt solutions were applied, in vivo, according to different strategies: (i) spraying before harvest, (ii) immersion after harvest, and (iii) the combination of pre- and postharvest treatments. Water was involved as a negative control while Rovral (a.i. iprodione) and SO₂ served for comparisons. After one month of cold storage at 2 ± 1 °C followed by one week of shelf-life at 22 ± 2 °C, the natural incidence of postharvest mold was mostly caused by B. cinerea. The efficacy of preharvest applications was noticeably high and statistically was not enhanced by further treatments after harvest. Salts applied only after harvest were not effective in suppressing Botrytis mold, with the exception of FeS. The influence of salts on physicochemical properties for berry quality was also monitored. The field application of salts can be considered as an appropriate regime to enhance their activity since no negative impact of their application on quality profile was observed. The incidence of gray mold can be significantly reduced using some salts which are safe for consumers and the environment.     

Low dose gamma irradiation does not affect the quality,proximate or nutritional profile of ‘Brigitta’ blueberry and ‘Maravilla’ raspberry fruit

Blueberry (Northern Highbush, cv ‘Brigitta’) and raspberry (cv ‘Maravilla’) fruit were subject to low dose gamma irradiation (0, 150, 400 and 1000 Gy) and stored at 0 °C for three or ten days (blueberry) and two or seven days (raspberry) to determine the effects of irradiation on fruit quality and nutritional and proximate contents. In general, none of the irradiation doses (≤1000 Gy) significantly affected blueberry or raspberry fruit quality (overall fruit quality, colour, firmness, weight loss, TSS, TA levels or TSS/TA ratio), or the nutritional or proximate content (ash, carbohydrate, dietary fibre, energy, moisture, protein, sodium, potassium, total sugars, fructose, ascorbic acid, monomeric anthocyanin, citric and malic acids). The length of time in storage affected some fruit quality and nutritional and proximate content parameters (such as overall fruit quality, firmness, weight loss, TA levels, dietary fibre, potassium, ascorbic acid, citric and malic acids), with longer storage periods resulting in lower quality fruit, irrespective of irradiation treatment. No interaction was detected between the effects of irradiation treatment and storage time, indicating that the storage effect was consistent for all irradiation doses on both blueberry and raspberry fruit quality.     

Effect of modified atmosphere packaging and storage temperature on volatile composition and postharvest life of minimally-processed pomegranate arils (cvs. ‘Acco’ and ‘Herskawitz’)

This study investigated the effects of passive modified atmosphere packaging (MAP), storage temperature (5, 10 and 15 °C) and duration of 14 days on the postharvest quality attributes, compositional change in flavour attributes and microbiological quality of minimally processed pomegranate arils (Punica granatum L.), cvs ‘Acco’ and ‘Herskawitz’. Volatile compounds were extracted via headspace solid phase micro-extraction (HS-SPME) and analyzed by gas chromatography–mass spectrometry (GC–MS). A total of 17 and 18 volatiles were detected and identified in the headspace of pomegranate juices of ‘Acco’ and ‘Herskawitz’, respectively. Based on the physicochemical attributes and microbial evaluation, the postharvest life of MA-packaged ‘Acco’ and ‘Herskawitz’ was limited to 10 days due to fungal growth ≥2 log CFU g⁻¹ at 5 °C. However, the concentration (%) and compositional changes in volatile compounds indicated that the flavour/aroma life (7 days) was shorter than the postharvest shelf-life based on appearance and other physicochemical (10 days) for both cultivars.     

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.     

Ripening behavior and quality of modified atmosphere packed ‘Doyenne du Comice’ pears during cold storage and simulated transit

The effect of MAP on extending storage life and maintaining fruit quality was studied in ‘Doyenne du Comice’ (Pyrus communis L.) pears at Hood River and Medford, Oregon. Control fruit packed in standard perforated polyethylene liners started to show senescent core breakdown and lost the capacity to ripen at 20 °C after 4–5 months of cold storage in Hood River and after 5.25–6 months in Medford. LifeSpan^® L257 MAP achieved steady-state atmospheres of 15.8% O₂ + 3.7% CO₂ in Hood River and 15.7–17.5% O₂ + 3.8–5.7% CO₂ in Medford. MAP inhibited ethylene production, ascorbic acid degradation and malondialdehyde accumulation, and extended storage life for up to 6 months with maintenance of fruit flesh firmness (FF) and skin color without commercially unacceptable level of physiological disorders. After 4, 5 and 6 months at −1 °C, MAP fruit exhibited climacteric-like patterns of ethylene production and softened to proper texture with desirable eating quality on day 5 during ripening at 20 °C. After 6 months at −1 °C plus 2 weeks of simulated transit conditions, MAP fruit maintained FF and skin color and had good eating quality at transit temperatures of 2 and 4.5 °C (10.1–11.5% O₂ + 4.8–5.2% CO₂), but reduced FF substantially and developed internal browning disorder at 7.5 and 20 °C (3.2–7.2% O₂ + 7.9–9.5% CO₂). The storage life of ‘Doyenne du Comice’ pears with high eating quality could be increased by up to 2 months when packed in MAP as compared with fruit packed in standard perforated polyethylene liners.     

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.     

Dynamics of ascorbic acid in ‘Braeburn’ and ‘Gala’ apples during on-tree development and storage in atmospheres conducive to internal browning development

The underlying causes as well as chemical and biochemical alleviation for CO₂-induced browning in apple fruit are poorly understood. Ascorbic acid (AsA) dynamics in ‘Braeburn,’ a susceptible cultivar, and ‘Gala’, a resistant cultivar, were evaluated during on-tree development and storage at 0.5 °C in air or controlled atmospheres (CA) containing 1 kPa O₂ and 1, 3 or 5 kPa CO₂. ‘Braeburn’ fruit treated with diphenylamine (DPA) was also stored for 1 month to determine effects on browning incidence and AsA concentration. ‘Braeburn’ apples had significantly higher (p ≤ 0.05) AsA levels than ‘Gala’ during on-tree development, and storage. No correlation between AsA and maturity/ripening indices for ‘Braeburn’ or ‘Gala’ was apparent. Histochemical localization of fruit AsA showed a staining intensity consistent with the quantity analytically determined, and showed that AsA is diffusely distributed throughout the cortex in both cultivars during on-tree development. During storage, AsA was localized to the periphery of brown tissue in ‘Braeburn’ and to the coreline and cortex proximal to the peel in ‘Braeburn’ and ‘Gala’ tissues. DPA decreased browning development during storage, however, no correlation between DPA treatment and AsA quantity in healthy or brown cortex tissue was observed. The results indicate AsA quantity alone is not an indicator of CO₂ sensitivity in these two cultivars.     

The effect of temperature on fruit set,seed set and seed germination in ‘Sonia’ × ‘Hadley’ hybrid Tea-rose crosses

Summary The effect of temperature on fruit set, seed set and seed germination was studied in Sonia × Hadley Hybrid Tea-rose crosses. Sonia mother bushes were grown at constant temperatures (10, 14, 18, 22, 26°C) in the greenhouses of the phytotron until fruit ripening. Fruit set, fruit weight and number of seeds increased as temperature was higher. Optimum temperatures were found for days to fruit ripening (18°C), seed germination (22°C) and number of seedlings per pollinated flower (22°C). Fruit weight and number of seeds were positively correlated. For crossing and the subsequent growing of seed-bearing plants 22°C was the most favourable temperature. Effects of temperature on pollen tube growth, fertilization and seed germination are discussed.     

Investigating the potential of a humidification system to control moisture loss and quality of ‘Crimson Seedless’ table grapes during cold storage

The potential of humidifying cold storage rooms to control moisture loss and quality of table grapes in different package designs was studied. Fruit were stored in cold rooms (−0.33 ± 0.32 °C or −0.12 ± 0.32 °C) with humidifier (95.0% RH) or no humidification (90.3% RH) respectively. Room humidification resulted in a 7.5% and 9.0% increase in RH inside the clamshell and open-top punnets multi-scale packages respectively in comparison to non-humidified storage, while there was no significant change in RH inside the 4.5 kg carry bag multi-packaging. The grapes were assessed for weight loss and SO₂ injury at intervals during a 35 d period. After 21 d of cold storage under humidification, weight loss of grapes was significantly higher (P < 0.05) in packages with open-top punnets than clamshell punnets and carry-bags. After 35 days in non-humidified cold storage, grape weight losses were 1.45 ± 0.32%, 1.62 ± 0.21% and 2.01 ± 0.57% for the 4.5 kg carry-bag, 5 kg clamshell punnet and 5 kg open-top multi-packages, respectively. When fruit were stored inside the same types of multi-packages under humidification, the corresponding weight losses were 0.97 ± 0.34%, 1.08 ± 0.27% and 2.00 ± 0.57%. Cold storage humidification reduced the rate of stem dehydration and browning; however, it increased the incidence of SO₂ injury in table grape bunches and caused wetting of the packages.