kPa O2 Research Articles

Treatment of 'cripps pink' apples with nitric oxide in a controlled atmosphere ultra-low oxygen: Impacts on overall fruit quality and anaerobic compounds

The objective of this work was to evaluate the impact of nitric oxide application (in different doses 0, 1, 2, 5 e 10 μL L−1 of NO) on fruit quality and formation of anaerobic metabolism products of 'Cripps Pink' apples stored in a controlled atmosphere ultra-low oxygen (CA - ULO). Fruit were harvested at two maturity stages (less and more mature) and stored in CA - ULO (0.8 kPa of O2, <0.5 kPa of CO2, at temperature of 1.5 ± 0.2 °C, and 94 ± 2% RH) for four and eight months, followed by seven days of shelf life. Fruit in CA - ULO were treated weekly with 0, 1, 2, 5, or 10 μL L−1 of NO. In general, linear and quadratic models adjusted to quantitative levels of NO showed reduced respiration and ethylene evolution rates with the increase of NO concentrations. Also, the increase of NO concentration consistently reduced the activities of β-GAL and PG, preserved flesh firmness, and reduced the production of anaerobic metabolites (acetaldehyde and ethanol) and the incidence of decay in the fruit. These effects of NO concentrations on each quality attribute were dependent on maturity stage and storage duration (period in CA - ULO and/or subsequent shelf life). However, the results show that weekly application of 5–7 μL L−1 of NO during storage in CA - ULO maintained the quality of 'Cripps Pink' apples.

Nitric oxide reapplication during controlled atmosphere storage impacts on oxidative stress and volatiles production in 'Cripps Pink' apples

The aim of this study was to evaluate the effect of different concentrations of nitric oxide (NO) reapplied during controlled atmosphere (CA) storage on oxidative stress defense mechanisms and on profile of volatile compounds of 'Cripps Pink' apples. Fruit were treated with NO at 0, 1, 2, 5, or 10 μL L−1 every seven days during CA storage (0.8 kPa of O2, <0.5 kPa of CO2, at temperature of 1.5 ± 0.2 °C, and 94 ± 2% RH). Fruit were evaluated after 8 months of CA storage, followed by seven days of shelf life. In general, linear and quadratic models adjusted to quantitative levels of NO showed increased contents of total phenolic compounds (in the pulp and peel tissues), increased activity of catalase, reduced activity of lipoxygenase, reduced content of H2O2, reduced lipid peroxidation and ethylene production in the fruit with the increase of NO concentrations. NO treatment had no effect in the total antioxidant activity and in the activity of the enzymes superoxide dismutase and peroxidase in the fruit. The increase of NO concentrations reduced the volatile compounds butyl acetate, hexyl acetate, 2-methylbutyl acetate, ethyl butanoate, til 2-methylbutanoate, and 1-butanol in the pulp of the fruit. The results show that weekly application of NO at ∼6 μL L−1 during CA storage of 'Cripps Pink' apples improved the mechanisms to protect the fruit from oxidative stress, but it might impair the production of the main esters associated with aroma.

Migratory songbirds exhibit seasonal modulation of the oxygen cascade.

Migratory flight requires birds to maintain intensive aerobic exercise for many hours or days. Maintaining O2 supply to flight muscles is therefore important during migration, especially since migratory songbirds have been documented flying at altitudes greater than 5,000 m above sea level, where O2 is limited. Whether songbirds exhibit seasonal plasticity of the O2 cascade to maintain O2 uptake and transport during migratory flight is not well understood. We investigated changes in the hypoxic ventilatory response, haematology, and pectoralis (flight) muscle phenotype of 6 songbird species from 3 families during migratory and non-migratory conditions. Songbirds were captured during southbound migration in southern Ontario, Canada. Half of the birds were assessed during migration, and the rest were transitioned onto a winter photoperiod to induce a non-migratory phenotype and measured. All species exhibited seasonal plasticity at various stages along the O2 cascade, but not all species exhibited the same responses. Broadly, songbirds were more hypoxia tolerant during migration, withstanding 5 kPa O2, and breathed more effectively through slower, deeper breaths. Warblers had a stronger haemoglobin-O2 affinity during fall migration (decrease of ∼4.7 Torr), while the opposite was observed in thrushes (increase of ∼2.6 Torr). In the flight muscle there was an ∼1.2-fold increase in the abundance of muscle fibers with smaller fiber transverse areas during fall migration, but no changes in capillary-fiber ratio. These adjustments would enhance O2 uptake and transport to the flight muscle. Our findings demonstrate that in the O2 cascade there is no ideal migratory phenotype for all songbirds.

Extremely low oxygen with different hysteresis and dynamic controlled atmosphere storage: Impact on overall quality and volatile profile of ‘Maxi Gala’ apple

This study aimed to evaluate the effect of the novel strategy of extreme low oxygen (ELO) associated to low O2 hysteresis (HY) and compare it with traditional controlled atmosphere (CA) and dynamic controlled atmosphere (DCA) methods during ‘Maxi Gala’ apple storage. The overall quality and volatile compounds were evaluated after 9 months of storage plus 7, 14, and 21 d of shelf life. Two experiments were performed in different years, evaluating ELO conditions, CA, CA + 1-methylcyclopropene (1-MCP), DCA monitored by chlorophyll fluorescence (DCA-CF), and monitored by respiratory quotient (DCA-RQ 1.3). ‘Maxi Gala’ apple stored under CA showed higher ethylene production, respiration rate, and physiological disorders incidence than fruit stored under CA + 1-MCP, ELO, and DCA. However, only storage in CA + 1-MCP and DCA-RQ 1.3 maintained higher flesh firmness. Fruit stored under 0.4 kPa O2 with 0.4 and 0.6 hysteresis had similar amount of healthy fruit to DCA-RQ 1.3 and higher than CA, CA + 1-MCP, and DCA-CF. Furthermore, CA + 1-MCP and DCA-CF suppressed the main esters of ‘Maxi Gala’ apple during all shelf life periods. On the other hand, storage in 0.4 kPa O2 + 0.6 HY resulted in fruit with higher alcohols and aldehydes concentration, in addition to have high amount of some important esters for ‘Maxi Gala’ aroma, such as 3-methylbutyl acetate. DCA-RQ and ELO storage, despite reduce main esters soon after storage, may result in aroma recovery after 21 d of shelf life. Thus, storage under ELO at 0.4 kPa O2, with 0.4 or 0.6 hysteresis, can be a promising alternative for ‘Maxi Gala’ apple storage, especially to CA and DCA-CF, without resulting in additional costs to the storage systems.

Recording of Low-Oxygen Stress Response Using Chlorophyll Fluorescence Kinetics in Apple Fruit

AbstractLong-term storage of apples (Malus x domestica, Borkh.) is increasingly taking place under Dynamic Controlled Atmosphere (DCA). The oxygen level is lowered to ≤ 1 kPa O2 and the apples are stored just above the Lower Oxygen Limit (LOL). Low oxygen stress during controlled atmosphere storage can lead to fermentation in apples if oxygen levels are too low. Chlorophyll fluorescence can be used to detect low-oxygen stress at an early stage during storage. The currently available non-imaging fluorescence systems often use the minimal fluorescence (Fo) parameter. In contrast, the use of chlorophyll fluorescence kinetics is insufficiently described. Therefore, this study aimed to gain more knowledge about the response of chlorophyll fluorescence kinetics to low oxygen stress in apples using a fluorescence imaging system. The results show that the kinetic fluorescence curves differ under aerobic and fermentation conditions. The fermentative conditions initiated a decrease in fluorescence intensity upon application of the saturation pulses during exposure to actinic light. This result was made at 18 °C and 2 °C ambient temperatures. Interestingly, the kinetic curve changed at 2 °C before fermentation products accumulated in the apples. Non-photochemical quenching (NPQ) decreased under fermentation conditions in the dark phase after relaxation. Upon entering the dark relaxation phase after Kautsky induction, ɸPSII began to increase. Under atmospheric oxygen conditions, ɸPSII reached values of 0.81 to 0.76, while under fermentation, ɸPSII values ranged from 0.57 to 0.44.

Interaction between dynamic controlled atmosphere (DCA-CD), 1-methylcyclopropene and elevated temperatures in the long-term storage of organic ‘Santana’ apples

This study investigated the effects of controlled atmosphere (CA - 1.0 kPa O2 and < 0.7 kPa CO2), dynamic controlled atmosphere based on carbon dioxide production (DCA-CD), 1-methylcyclopropene (1-MCP), and raised storage temperatures (1 °C to 3 °C), on fruit metabolism and quality, disorder incidences and the volatile profile of ‘Santana’ apples after 6 months storage and 7 d shelf life at 20 °C. The evaluation is based on a comparison to a control group of cold storage under regular atmosphere (RA). Low oxygen partial pressures (pO2) in CA and DCA-CD in combination with 1-MCP slowed down fruit respiration and ethylene production and thus compensated for the ripening-inducing effect of raised storage temperatures. ‘Santana’ apples stored under CA or DCA-CD with additional 1-MCP, had the highest flesh firmness, titratable acidity, and greener peel coloration after storage and shelf life. CA and DCA-CD reduced core browning and fungal decay in comparison to RA. Low pO2 and 1-MCP application lowered the abundance of straight-chain alcohols and esters in ‘Santana’ apples. DCA-CD storage enabled a safe induction of anaerobic metabolism in ‘Santana’ apples, which increased levels of ethanol and derived ethyl esters. 1-MCP enhanced anaerobic metabolism in DCA-CD. Raised storage temperatures were found to increase alcohol and ester accumulation in DCA-CD. This technology consequently enables the storage of ‘Santana’ apples at higher temperatures, which could contribute to limiting stress experienced by the fruit and enhancing the formation of key aroma compounds, while also reducing energy usage of the refrigeration system.

Factors affecting development of disorders expressed after storage of ‘Gala’ apple fruit

This study investigated factors influencing susceptibility and development of physiological disorders and decay expressed after long-term storage in ‘Gala’ apple fruit (Malus domestica Borkh.). Five experiments were performed over ten production years with fruit from two environmentally different orchard locations in a humid subtropical climate at 990 m (warmer) and 1415 m above sea level. Fruit were harvested at two maturity stages (early and advanced), treated or not treated with 1-methylcyclopropene (1-MCP) and stored at 0.5 °C or 2 °C in a controlled atmosphere (CA, 1.5 kPa O2 and 2.5 kPa CO2), for 240 d plus 7 d shelf life. In one experiment, fruit were stored in CA with CO2 concentrations of 1.5 or 3 kPa. The relationship between fruit mineral composition and physiological disorders was assessed in one production year. Flesh browning (FB) was the predominant disorder, followed by decay, cracking, and lenticel breakdown-wet (LB-wet). The average severity index of lenticel breakdown-dry (LB-dry), leather blotch and bitter pit were low and variable across production years. The FB index was lowest in fruit produced at the colder orchard location, early harvest, treatment with 1-MCP, and storage at 2 °C. These factors also influenced fruit softening after storage. The major source of variance of the FB index in order of decreasing contribution were harvest maturity, production year, orchard location, 1-MCP and storage temperature. Production year variability of FB index correlated positively with early summer rain and negatively with early spring temperature. A weak positive correlation was also found between FB index and fruit K+Mg/Ca ratio. Higher CA CO2 concentration increased FB in fruit stored at 0.5 °C but not at 2 °C. The same factors affected decay, cracking and LB-wet disorder similarly as for FB, except that decay and cracking were not consistently affected by storage temperature, and decay and LB-wet were not impacted by 1-MCP. Storage temperature had the most influence on the variance of LB-wet. LB-dry was highest in late harvest fruit and, in the production year with the highest index, in fruit stored at 0.5 °C. Leather blotch was highest in early harvest fruit and in fruit stored at 0.5 °C. 1-MCP treatment did not affect disorders other than FB and cracking. These results suggest that interactions among harvest and postharvest factors influence the development of ‘Gala’ FB and other disorders and indicate a possible relationship of chilling in FB development. The information may be useful for implementing practical strategies to reduce the development of these postharvest disorders in ‘Gala’ apple fruit.

Vascular protection afforded by zinc supplementation in human coronary artery smooth muscle cells mediated by NRF2 signaling under hypoxia/reoxygenation

Zinc (Zn) has antioxidant, anti-inflammatory and anti-proliferative actions, with Zn dysregulation associated with coronary ischemia/reperfusion injury and smooth muscle cell dysfunction. As the majority of studies concerning Zn have been conducted under non-physiological hyperoxic conditions, we compare the effects of Zn chelation or supplementation on total intracellular Zn content, antioxidant NRF2 targeted gene transcription and hypoxia/reoxygenation-induced reactive oxygen species generation in human coronary artery smooth muscle cells (HCASMC) pre-adapted to hyperoxia (18 kPa O2) or normoxia (5 kPa O2). Expression of the smooth muscle marker SM22-α was unaffected by lowering pericellular O2, whereas calponin-1 was significantly upregulated in cells under 5 kPa O2, indicating a more physiological contractile phenotype under 5 kPa O2. Inductively coupled plasma mass spectrometry established that Zn supplementation (10 μM ZnCl2 + 0.5 μM pyrithione) significantly increased total Zn content in HCASMC under 18 but not 5 kPa O2. Zn supplementation increased metallothionein mRNA expression and NRF2 nuclear accumulation in cells under 18 or 5 kPa O2. Notably, NRF2 regulated HO-1 and NQO1 mRNA expression in response to Zn supplementation was only upregulated in cells under 18 but not 5 kPa. Furthermore, whilst hypoxia increased intracellular glutathione (GSH) in cells pre-adapted to 18 but not 5 kPa O2, reoxygenation had negligible effects on GSH or total Zn content. Reoxygenation-induced superoxide generation in cells under 18 kPa O2 was abrogated by PEG-superoxide dismutase but not by PEG-catalase, and Zn supplementation, but not Zn chelation, attenuated reoxygenation-induced superoxide generation in cells under 18 but not 5kPaO2, consistent with a lower redox stress under physiological normoxia. Our findings highlight that culture of HCASMC under physiological normoxia recapitulates an in vivo contractile phenotype and that effects of Zn on NRF2 signaling are altered by oxygen tension.

Redox and metal profiles in human coronary endothelial and smooth muscle cells under hyperoxia, physiological normoxia and hypoxia: Effects of NRF2 signaling on intracellular zinc

Zinc is an important component of cellular antioxidant defenses and dysregulation of zinc homeostasis is a risk factor for coronary heart disease and ischemia/reperfusion injury. Intracellular homeostasis of metals, such as zinc, iron and calcium are interrelated with cellular responses to oxidative stress. Most cells experience significantly lower oxygen levels in vivo (2–10 kPa O2) compared to standard in vitro cell culture (18kPa O2). We report the first evidence that total intracellular zinc content decreases significantly in human coronary artery endothelial cells (HCAEC), but not in human coronary artery smooth muscle cells (HCASMC), after lowering of O2 levels from hyperoxia (18 kPa O2) to physiological normoxia (5 kPa O2) and hypoxia (1 kPa O2). This was paralleled by O2-dependent differences in redox phenotype based on measurements of glutathione, ATP and NRF2-targeted protein expression in HCAEC and HCASMC. NRF2-induced NQO1 expression was attenuated in both HCAEC and HCASMC under 5 kPa O2 compared to 18 kPa O2. Expression of the zinc efflux transporter ZnT1 increased in HCAEC under 5 kPa O2, whilst expression of the zinc-binding protein metallothionine (MT) decreased as O2 levels were lowered from 18 to 1 kPa O2. Negligible changes in ZnT1 and MT expression were observed in HCASMC. Silencing NRF2 transcription reduced total intracellular zinc under 18 kPa O2 in HCAEC with negligible changes in HCASMC, whilst NRF2 activation or overexpression increased zinc content in HCAEC, but not HCASMC, under 5 kPa O2. This study has identified cell type specific changes in the redox phenotype and metal profile in human coronary artery cells under physiological O2 levels. Our findings provide novel insights into the effect of NRF2 signaling on Zn content and may inform targeted therapies for cardiovascular diseases.

Impacts of dynamic controlled atmosphere and temperature on physiological disorder incidences, fruit quality and the volatile profile of 'Braeburn' apples

DCA-CD Plus is a novel dynamic storage technology that determines both the optimum oxygen partial pressures (pO2) and room temperatures for the storage of apples, based on monitoring the fruit CO2 production (CD). This study evaluated the effects of DCA-CD Plus on the physiological disorder incidences, fruit quality and the volatile profile of ‘Braeburn’ apples after eight months of storage and seven days shelf life. This was achieved by comparison to storage under regular atmosphere (RA), controlled atmosphere (CA, 1.3 kPa O2) and one-factor dynamic controlled atmosphere (DCA-CD, dynamic oxygen), while incorporating the influence of 1-methylcyclopropene (1-MCP). RA-stored fruit had the highest respiration rate and ethylene production and the lowest flesh firmness, while CA, DCA treatments and 1-MCP application slowed down fruit ripening. 1-MCP application increased browning and cavity symptoms in ‘Braeburn’ apples. Storage under DCA-CD and DCA-CD Plus resulted in lower browning incidences than RA or static CA treatments. Dynamic storage temperatures in DCA-CD Plus did not accelerate fruit ripening but showed no effect on the development of physiological disorders. Most volatile organic compounds showed a negative response to low pO2 and 1-MCP application, as the highest levels of key alcohols and esters were measured in RA. Storage under DCA conditions and RA correlated with increased levels of anaerobic metabolites. No correlation between internal browning symptoms and specific alterations in the volatile profile could be detected.

The Effect of Aminoethoxyvinylglycine and Dynamic Controlled Atmosphere on the Storage of ‘Bartlett’ Pear

Storage trials of 4 and 8 months’ duration, using ‘Bartlett’ pear (Pyrus communis) fruit treated with and without aminoethoxyvinylglycine (AVG) and stored using ultra low oxygen (ULO) storage (1.5 kPa O2) versus dynamic controlled atmosphere (DCA) (≈ 0.6–0.7 kPa O2) based on chlorophyll fluorescence were conducted over 2 years. AVG applied preharvest and DCA storage produced pears with significantly lower respiration, ethylene, acetaldehyde, ethyl acetate and ethanol post-storage compared to the other treatment combinations. Lower volatiles reflected a higher level of fruit quality. AVG + DCA also exhibited greater green color and firmness retention than the other treatment combinations. There were few disorders in both years of study, with no correlation with field and storage treatments, with the exception of pear scuffing, which was only present in year 2. The incidence of scuffing was positively associated with both fruit softening and yellowing, with DCA + AVG showing the lowest incidence (10%) and ULO + control, the highest (65%). Softening occurred during the shelf life period, as required, and was not an issue for any treatment combination. However, uneven degreening was a concern for fruit treated with DCA + AVG (mainly when firmness at harvest was > 85 N). Future research on higher maturity levels at harvest or reduced AVG rates could address this concern.

High‐temperature oxidation behavior of the SiC layer of TRISO particles in low‐pressure oxygen

Surrogate tristructural-isotropic (TRISO)-coated fuel particles were oxidized in 0.2 kPa O2 at 1200–1600°C to examine the behavior of the SiC layer and understand the mechanisms. The thickness and microstructure of the resultant SiO2 layers were analyzed using scanning electron microscopy, focused ion beam, and transmission electron microscopy. The majority of the surface comprised smooth, amorphous SiO2 with a constant thickness indicative of passive oxidation. The apparent activation energy for oxide growth was 188 ± 8 kJ/mol and consistent across all temperatures in 0.2 kPa O2. The relationship between activation energy and oxidation mechanism is discussed. Raised nodules of porous, crystalline SiO2 were dispersed across the surface, suggesting that active oxidation and redeposition occurred in those locations. These nodules were correlated with clusters of nanocrystalline SiC grains, which may facilitate active oxidation. These findings suggest that microstructural inhomogeneities such as irregular grain size influence the oxidation response of the SiC layer of TRISO particles and may influence their accident tolerance.

Do Rootstocks Influence Global Fruit Quality, Postharvest Performance and Metabolite Profiles of Persea americana cv. Hass?

The choice of rootstock has a significant impact, not only on fruit growth and development, but also on avocado fruit quality and postharvest performance. The objective of this study was to evaluate and compare attributes related to the postharvest quality of Hass avocados from “Mexicola” and “Duke 7” rootstocks grown under similar conditions. This study included two harvests: early (23–26% dry matter) and middle (&gt;26–30% dry matter) per season for the 2016/2017 and 2017/2018 seasons and two storage conditions (regular air (RA) at 5 °C and controlled atmosphere (CA) at 4 kPa O2 and 6 kPa CO2 at 5 °C) for 55 days. The results showed significant differences in firmness, color and vascular and flesh browning between storage conditions; in addition to these last three attributes, the rootstock played an important role. The fatty acid profile did not reveal significant differences between fruit from both rootstocks. Finally, the polar metabolite profiles revealed differences only for the storage condition, not associated to the rootstock, which could affect the postharvest performance of Hass avocado fruit. This study is one of the few available showing the interaction of rootstock/Hass cultivar on fruit quality and postharvest performance.

Does severe hypoxia during irradiation of Aedes aegypti pupae improve sterile male performance?

BackgroundThe yellow fever mosquito, Aedes aegypti, vectors several pathogens responsible for human diseases. As a result, this mosquito species is a priority for control by mosquito control districts in Florida. With insecticide resistance development becoming a concern, alternative control strategies are needed for Ae. aegypti. Sterile insect technique (SIT) is an increasingly popular option that is being explored as a practical area-wide control method. However, questions about sterile male performance persist. The objectives of this study were to determine the extent to which hypoxia exposure prior to and during irradiation effects the longevity, activity and mating competitiveness of sterile male Ae. aegypti.MethodsMale longevity was monitored and analyzed using Cox regression. Mosquito activity was recorded by an infrared beam sensor rig that detected movement. Competing models were created to analyze movement data. Fecundity and fertility were measured in females mated with individual males by treatment and analyzed using one-way ANOVAs. Mating competition studies were performed to compare both hypoxia and normoxia treated sterile males to fertile males. Competitiveness of groups was compared using Fried’s competitiveness index.ResultsFirst, we found that subjecting Ae. aegypti pupae to 1 h of severe hypoxia (< 1 kPa O2) did not directly increase mortality. One hour of hypoxia was found to prevent decreases in longevity of irradiated males compared to males irradiated in normoxic conditions. Exposure to hypoxia prior to irradiation did not significantly improve activity of sterile males except at the highest doses of radiation. Hypoxia did significantly increase the required dose of radiation to achieve > 95% male sterility compared to males irradiated under normoxic conditions. Males sterilized after an hour in hypoxic conditions were significantly more competitive against fertile males compared to males irradiated under normoxic conditions despite requiring a higher dose of radiation to achieve sterility.ConclusionsHypoxia was found to greatly improve key performance metrics in sterile male Ae. aegypti without any significant drawbacks. Little work other than increasing the target dose for sterility needs to be conducted to incorporate hypoxia into SIT programs. These results suggest that SIT programs should consider including hypoxia in their sterile male production workflow.Graphical

Comprehensive responses of aroma production in 'Benihoppe' strawberry to low oxygen associated with the changes of key gene expressions and energy levels.

The influence of low oxygen on the biosynthesis of aroma-related esters and alcohols in strawberries has been well revealed. However, how low-oxygen conditions affect other volatile compounds, such as terpenes and furans, is still to be elucidated. The effects of 2 kPa O2 low oxygen on the biosynthesis of aroma in 'Benihoppe' strawberries were comprehensively investigated in this study. The results showed that, like esters, the accumulations of key terpene alcohols and furans in strawberries were also inhibited by 2 kPa O2 low oxygen during storage and subsequent shelf life, which was associated with the down-regulation of expression of FaNES1 (nerolidol synthase) and FaOMT (O-methyltransferase). However, no anaerobic fermentation occurred in 'Benihoppe' strawberries since no ethanol and acetaldehyde were produced under the 2 kPa O2 condition. As expected, the 2 kPa O2 condition suppressed the respiratory intensity and lowered the energy charge to maintain the quality of strawberries. The negative effects of low-oxygen storage on aroma accumulations and the energy charge of strawberries were more pronounced when transferred to the period of shelf life. The 2 kPa O2 condition caused a full-scale loss of aroma in 'Benihoppe' strawberries, including esters and alcohols as well as terpenes and furans, which was mainly reflected in the reduction of aroma emissions rather than the production of off-flavor, probably due to the reduced expressions of related genes and energy charge. © 2022 Society of Chemical Industry.

Tissue-Specific Recovery Capability of Aroma Biosynthesis in ‘Golden Delicious’ Apple Fruit after Low Oxygen Storage

The impact of low-oxygen (2 kPa) controlled atmosphere storage on the recovery of aroma biosynthesis in ‘Golden Delicious’ (GD) apple tissues during their subsequent shelf life was investigated. The results showed that the highest ester content was found in skin tissue, followed by Flesh 2 and Flesh 1. The 2 kPa O2 storage of GD apples resulted in a decrease in the emission of volatile esters and alcohols, but an increase in aldehyde emission. Notably, compared with skin tissue, the flesh tissue of 2 kPa O2-stored GD apples had a relatively high recovery capacity of ester biosynthesis but a low recovery capacity of alcohol synthesis for its shelf life. The impact was associated with increased levels in the MdLOX1a and MdAATs (MdAAT1 and MdAAT2) transcripts, as well as a decreased level in the MdHPL transcript in the flesh tissue. In addition, a complex regulatory network of ethylene on fruit aroma biosynthesis in response to low-oxygen conditions was also indicated. Collectively, there was a tissue-specific recovery capability of aroma biosynthesis in GD apples after low-oxygen storage.

Treatment of ‘Baigent’ apple fruit with nitric oxide in controlled atmosphere storage reduces decay and physiological disorders

The study was carried out to evaluate the effects of nitric oxide (NO) treatment at different doses and times during controlled atmosphere (CA) storage on quality of ‘Baigent’ apples. The evaluated treatments were: control; 10 µL L−1 of NO applied only at the beginning of CA storage; 1, 2 or 5 µL L−1 of NO applied every 30 d of CA storage; and 5 µL L−1 of NO applied at the beginning and at the end of CA storage. Fruit were stored for 7.5 months in 1.2 kPa O₂ + 2.0 kPa CO₂, 1.5 ± 0.2 °C, and relative humidity of 94 ± 2%. NO treatments, except 10 µL L−1 NO applied only at the beginning of CA storage, reduced ethylene production. At removal from CA storage, 5 µL L−1 NO, applied every 30 d of CA storage or at the beginning and at the end of CA storage, reduced respiratory rates. Control fruit and fruit treated with 2 µL L−1 NO every 30 d of CA storage had higher soluble solids content, and control fruit and fruit treated with NO at 1 or 2 µL L−1 every 30 d of CA storage had higher titratable acidity. NO treatments, regardless of the dose and application time during CA storage, delayed skin yellowing and reduced hydrogen peroxide content and the incidence of pulp mealiness. The application of 5 µL L−1 of NO at the beginning and at the end of CA storage maintained a higher total phenolic compound content and reduced the incidence of flesh browning. Treatment with 5 µL L−1 NO at the beginning and at the end of CA storage provided better quality maintenance of ‘Baigent’ apples.

Volatile compounds profile and quality of “Cripps pink” apple: Impact of dynamic controlled atmosphere combined to delayed storage and 1‐MCP treatment

AbstractThis study evaluated the effects of delayed storage followed by storage under static controlled atmosphere (CA) and dynamic controlled atmosphere established by respiratory quotient (DCA‐RQ) with and without 1‐methylcyclopropene (1‐MCP) application on quality and volatile profile of “Cripps Pink” apple. A fruit batch was immediately stored at 1.5 ± 0.1°C, and another remained for 7 days at 20°C (delay) until storage. The storage conditions were: (1) CA (1.0 kPa O2 + 1.0 kPa CO2); (2) DCA‐RQ 1.3; (3) DCA‐RQ 1.5. Additionally, for each storage condition and delay strategy, a batch of fruit was treated with 1‐MCP, and another batch was left untreated.Practical applicationsDCA‐RQ 1.3 maintened flesh firmness even without 1‐MCP and with delayed storage. 1‐MCP application reduced all esters. Delayed storage increased the esters concentration and when associated with DCA‐RQ 1.3 and 1.5 should be recommended to reduce decay, increase the healthy fruit amount, and improve the aroma emission of “Cripps Pink” apple.

Combined effect of UV–C and passive modified atmosphere packaging to preserve the physicochemical and bioactive quality of fresh figs during storage

Figs are an important constituent of the Mediterranean diet, widely consumed fresh. Due to their very short shelf life, postharvest techniques to preserve quality and safety should be implemented. The current work aimed to study the combined effect of a postharvest UV–C treatment (5 or 10 kJ m−2) followed by packaging under passive modified atmosphere (MAP) on physicochemical and bioactive quality of fresh figs (cv. ‘Colar’) stored up to 12 d at 0 ºC (90–95% RH). As controls, UV–C untreated and air-stored (AIR) samples were used. The flesh firmness, skin colour, soluble solids content (SSC), titratable acidity (TA), pH, total phenolic content and total antioxidant activity were monitored. The steady-state modified atmosphere reached since day 8 was 17 kPa CO2 and 4 kPa O2. UV-C treated samples did not show visual decay incidence, while mycelial growth was observed in untreated figs on day 12. Figs treated with 10 kJ m-2 UV–C and stored under MAP conditions showed the highest flesh firmness with values of 0.6 N, which is 50% higher than in AIR. Skin darkening observed among samples was higher in 10 kJ m-2 with Chroma decreases of 2.6 units on day 12 under MAP, although panellists preferred this treatment according to its visual appearance. Higher SSC and TA differences were found in UVC-treated samples during storage. Moreover, 10 kJ m-2 UV–C and MAP induced the highest total phenolic content accumulation, with 260% and 540% higher values from day 4 to day 12 for skin and flesh, respectively. In conclusion, a 10 kJ m−2 UV–C treatment after harvesting followed by packaging under MAP conditions may be considered a good tool to preserve the physicochemical and bioactive quality of fresh figs during 12 d at 0 ºC.

Equilibrium modified atmosphere packaging on postharvest quality and antioxidant activity of strawberry

SummaryMicroporous film and MAP were evaluated to find the optimal method for extending the postharvest storage of strawberry. To determine the most suitable MAP system for strawberry, fruits were stored in controlled atmospheres (O2/CO2 partial pressures in kPa: 5/10; 10/10; 5/15), and in a separate experiment, strawberries were sealed in the container with different microporous PET/PE films. Results showed that the optimum atmosphere of strawberries was 10 kPa O2 + 10 kPa CO2 which could be achieved and maintained by using the microporous film with four perforations of 100 μm. By maintaining the optimal atmosphere, active EMAP could increase polyphenol compounds accumulation, with total phenolic content increased by 25% and the content of anthocyanin and total flavonoid was 13% and 29% higher than control at the end of storage. Meanwhile, active EMAP significantly increased CAT PAL and APX activities and the shelf‐life was prolonged for 6 and 3 days, respectively, compared with strawberries packed in control and passive EMAP.