Changes in respiration of fresh-cut butterhead lettuce under controlled atmospheres using low and superatmospheric oxygen conditions with different carbon dioxide levels

The effect of different O₂ levels from 0 to 100 kPa in combination with 0, 10 and 20 kPa CO₂ on the respiration metabolism of greenhouse grown fresh-cut butter lettuce was studied. Controlled atmospheres of 20 or 75 kPa O₂ with 0 or 10 kPa CO₂ showed a constant respiration rate during the first 2–4 days at different temperatures (1, 5 and 9 °C). Therefore, constant respiration rates during a short period of 2–4 days could be considered as valid for a large part of the commercial life of, for instance, a modified atmosphere package development. The fresh-cut lettuce exposed to low O₂ levels (2–10 kPa) combined with moderate to high CO₂ levels (10 and 20 kPa) had a higher respiration rate than when 20–100 kPa O₂ were used. Moderate CO₂ levels (10 kPa) reduced the respiration rates of fresh-cut lettuce 20–40% at 9 °C. This effect was less noticed at lower temperatures. Gas composition with high CO₂ levels (20 kPa) probably caused a metabolic disorder increasing the respiration rate of fresh-cut butter lettuce. It was concluded that 80 kPa O₂ must be used in modified atmosphere packaging (MAP) to avoid fermentation of fresh-cut butter lettuce in combination with 10–20 kPa CO₂ for reducing their respiration rate.     

The effect of modified atmospheres on the rate of firmness change of ‘Hayward’ kiwifruit

Gas exchange rates and softening of kiwifruit (Actinidia deliciosa (A Chev) Liang et Ferguson cv Hayward) were measured during two seasons under a range of modified atmosphere (MA) conditions (0–21 kPa O₂, 0–5 kPa CO₂) at 0–10 °C to characterise their functional relationship. The kinetics of gas exchange and softening were the same for the two seasons studied.CO₂ partial pressures delayed softening but did not inhibit the rate of gas exchange. Lowering the O₂ levels to near 0 kPa did not inhibit softening completely, suggesting that the rate of softening was driven by energy provided by both oxidative and fermentative processes.An integrated modelling approach was used to link the rate of softening to the rate of gas exchange explaining 88% of the effect of MA on both the rate of gas exchange and fruit softening. Shelf life simulations showed that during storage at 0 °C, lowering O₂ or raising CO₂ gave a substantial benefit towards extending shelf life. At temperatures higher than 3 °C, the additional effect of MA was already limited.     

Relationships between the instrumental and sensory characteristics of four peach and nectarine cultivars stored under air and CA atmospheres

‘Big Top’ and ‘Venus’ nectarines and ‘Early Rich’ and ‘Sweet Dream’ peaches were picked at commercial maturity and stored for 20 and 40 d at −0.5 °C and 92% RH under either air or one of the three different controlled atmosphere regimes (2 kPa O₂/5 kPa CO₂, 3 kPa O₂/10 kPa CO₂ and 6 kPa O₂/17 kPa CO₂). Physicochemical parameters and volatile compounds emission were instrumentally measured after cold storage plus 0 or 3 d at 20 °C. Eight sensory attributes were assessed after cold storage plus 3 d at 20 °C by a panel of 9 trained judges, in order to determine the relationship between sensory and instrumental parameters and the influence of storage period and cold storage atmosphere composition on this relationship.A principal component analysis (PCA) was undertaken to characterize the samples according to their sensory attributes. PCA results reflected the main characteristics of the cultivars: ‘Big Top’ was the nectarine cultivar with the highest values for sweetness, juiciness and flavor; ‘Sweet Dream’ was the sweetest peach and was characterized by high values for crispness and firmness, while ‘Venus’ and ‘Early Rich’ were characterized by their sourness. To assess the influence of storage period and CA composition on sensory properties, a PLS model of the flavor of the different samples was constructed using standard quality attributes and volatile concentrations as the X-variables. The model with 2 factors accounted for more than 80% of flavor variance. PLS results indicated that the main influence on flavor perception was storage period. Atmosphere composition also had an influence on flavor perception: flavor perception decreased from samples stored in a 2/5 O₂/CO₂ atmosphere composition to those of 3/10 and 6/17. These results can be qualitatively extended to juiciness and sweetness since all these sensory properties were strongly correlated.     

Influence of the combination of different atmospheres on diphenylamine,folpet and imazalil content in cold-stored ‘Pink Lady®’ apples

‘Pink Lady^®’ apples were harvested at commercial maturity, treated with three different agrochemical products, and stored at 1 °C under either air or controlled atmosphere conditions (2 kPa O₂ + 2 kPa CO₂ and 1 kPa O₂ + 1 kPa CO₂) for 13 and 27 weeks, followed by 4 weeks storage in air at 1 °C. Diphenylamine, folpet and imazalil contents in both the skin and flesh were simultaneously determined after cold storage plus simulated marketing periods of 1 and 7 d at 20 °C. After 27 weeks plus 7 d, diphenylamine and folpet levels in apple skin were lower for fruit stored in low O₂ (2 kPa) or air than for those kept under ultra-low O₂ (1 kPa). An additional storage period of 4 weeks in air reduced diphenylamine and folpet contents in whole apples stored for 13 weeks in the low O₂ controlled atmosphere. For imazalil, the same result was obtained in apple skins stored for 27 weeks under an ultra-low O₂ controlled atmosphere. Differences in diphenylamine and folpet contents were found for skin and flesh samples throughout the simulated marketing period, but there were observable differences in imazalil contents only for flesh samples.     

Effect of atmospheric modification, 1-MCP and chemicals on quality of fresh-cut banana

Fresh-cut banana slices have a short shelf-life due to fast browning and softening after processing. The effects of atmospheric modification, exposure to 1-MCP, and chemical dips on the quality of fresh-cut bananas were determined. Low levels of O₂ (2 and 4 kPa) and high levels of CO₂ (5 and 10 kPa), alone or in combination, did not prevent browning and softening of fresh-cut banana slices. Softening and respiration rates were decreased in response to 1-MCP treatment (1 μL L⁻¹ for 6 h at 14 °C) of fresh-cut banana slices (after processing), but their ethylene production and browning rates were not influenced. A 2-min dip in a mixture of 1% (w/v) CaCl₂ + 1% (w/v) ascorbic acid + 0.5% (w/v) cysteine effectively prevented browning and softening of the slices for 6 days at 5 °C. Dips in less than 0.5% cysteine promoted pinking of fresh-cut banana slices, while concentrations between 0.5 and 1.0% cysteine delayed browning and softening and extended the post-cutting life to 7 days at 5 °C.     

Controlled atmosphere storage of guava (Psidium guajava L.) fruit

The effects of controlled atmospheres (CA) on respiration, ethylene production, firmness, weight loss, quality, chilling injury, and decay incidence of three commercially important cultivars of guava fruit were studied during storage in atmospheres containing 2.5, 5, 8, and 10 kPa O₂ with 2.5, 5, and 10 kPa CO₂ (balance N₂) at 8 °C, a temperature normally inducing chilling injury. Mature light green fruit of cultivars, ‘Lucknow-49’, ‘Allahabad Safeda’ and ‘Apple Colour’, were stored for 30 days either in CA or normal air, and transferred to ambient conditions (25–28 °C and 60–70% R.H.) for ripening. CA storage delayed and suppressed respiratory and ethylene peaks during ripening. A greater suppression of respiration and ethylene production was observed in fruit stored in low O₂ (≤5 kPa) atmospheres compared to those stored in CA containing 8 or 10 kPa O₂ levels. High CO₂ (>5 kPa) was not beneficial, causing a reduction in ascorbic acid levels. CA storage was effective in reducing weight loss, and maintaining firmness of fruit. The changes in soluble solids content (SSC), titratable acidity (TA), ascorbic acid, and total phenols were retarded by CA, the extent of which was dependent upon cultivar and atmosphere composition. Higher amounts of fermentative metabolites, ethanol and acetaldehyde, accumulated in fruit held in atmospheres containing 2.5 kPa O₂. Chilling injury and decay incidence were reduced during ripening of fruit stored in optimal atmospheres compared to air-stored fruit. In conclusion, guava cultivars, ‘Lucknow-49’, ‘Allahabad Safeda’, and ‘Apple Colour’ may be stored for 30 days at low temperature (8 °C) supplemented with 5 kPa O₂ + 2.5 kPa CO₂, 5 kPa O₂ + 5 kPa CO₂, and 8 kPa O₂ + 5 kPa CO₂, respectively.     

Physicochemical measurements in ‘Mondial Gala®’ apples stored at different atmospheres: Influence on consumer acceptability

Standard quality parameters, consumer acceptability, emission of volatile compounds and ethylene production of ‘Mondial Gala^®’ apples (Malus × domestica Borkh.) were determined in relation to storage atmosphere, storage period and shelf-life period. Fruit were harvested at the commercial date and stored in AIR (21 kPa O₂:0.03 kPa CO₂) or under three different controlled atmospheres (CAs): LO (2 kPa O₂:2 kPa CO₂), ULO1 (1 kPa O₂:1 kPa CO₂), or ULO2 (1 kPa O₂:2 kPa CO₂). Fruit samples were analysed after 12 and 26 weeks of storage plus 1 or 7 d at 20 °C.Apples stored in CA maintained better standard quality parameters than AIR-stored fruit. The volatile compounds that contributed most to the characteristic aroma of ‘Mondial Gala^®’ apples after storage were butyl, hexyl and 2-methylbutyl acetate, hexyl propanoate, ethyl butanoate, ethyl hexanoate, ethyl, butyl and hexyl 2-methylbutanoate. Data obtained from fruit analysis were subjected to principal component analysis (PCA). The apples most accepted by consumers showed the highest emission of ethyl 2-methylbutanoate, ethyl hexanoate, tert-butyl propanoate and ethyl acetate, in addition to the highest titratable acidity and firmness values.     

Controlled atmosphere storage of rabbiteye blueberries enhances postharvest quality aspects

Blueberries are highly perishable and therefore it is necessary to develop strategies to increase their storage life. Two rabbiteye cultivars (‘Centurion’ and ‘Maru’) were stored at 1.5 °C in either regular air or controlled atmosphere (2.5 kPa O₂ + 15 kPa CO₂) for up to 6 weeks. Measurements of firmness, soluble solids content, titratable acidity, weight loss, shrivel and blemishes were combined with determinations of antioxidant activities and total phenolic content. Weight loss and shrivel were not affected by storage atmosphere or storage duration. After 28 days, controlled atmosphere storage resulted in only half as much blemished fruit compared with storage in regular air. Additionally, fungal development in ‘Maru’ fruit was minimised by controlled atmosphere storage.Water-soluble extracts from ‘Centurion’ fruit had higher antioxidant activities and total phenolic content than those from ‘Maru’ fruit at harvest and after storage in regular air and controlled atmosphere. The highest increases in antioxidant activity and total phenolic content occurred during the additional 6 days of shelf-life at 20 °C.     

Multivariate analysis of modifications in biosynthesis of volatile compounds after CA storage of ‘Fuji’ apples

Emission of aroma volatile compounds and some related enzyme activities (LOX, PDC, ADH, and AAT) were assessed in ‘Fuji’ apples (Malus × domestica Borkh.) during shelf life at 20 °C following cold storage under air or under three different CA conditions (3 kPa O₂:2 kPa CO₂; 1 kPa O₂:1 kPa CO₂; or 1 kPa O₂:2 kPa CO₂). Data were used for principal component analysis (PCA) and partial least-square regression (PLSR) analysis of results. LOX activity was partly inhibited by hypoxic conditions, and thus could have contributed to differentiation between air- and CA-stored fruit. Accordingly, emission of straight-chain esters was also higher in air- than in CA-stored fruit. In contrast, PDC activity was responsible for part of the differences between low (3 kPa) and ultra-low (1 kPa) O₂ storage conditions, probably by providing substrates for AAT action. AAT activity afforded no satisfactory differentiation between samples, and therefore it is suggested that substrate availability is a more decisive factor than enzyme activity for volatile production after storage. The PCA and PLSR models developed in this work were not useful for discrimination between the two studied ultra-low O₂ conditions.     

Postharvest life and flavor quality of three strawberry cultivars kept at 5 °C in air or air+20 kPa CO2

The postharvest life and flavor quality of three strawberry (Fragaria x ananassa D.) cultivars (Aromas, Diamante and Selva) kept at 5 °C in air or air+20 kPa CO₂ for up to 15 days were investigated. ‘Diamante’ and ‘Selva’ had better flavor quality than ‘Aromas’ strawberries, as indicated by levels of titratable acidity and total soluble solids, organic acids, sugars and some aroma compounds and by a consumer preference test. Flesh firmness was maintained in ‘Aromas’ and increased in ‘Diamante’ and ‘Selva’ strawberries during storage at 5 °C in both air and air+20 kPa CO₂. Fruit color was not affected by CO₂ treatments. The postharvest life based on appearance was 7, 9 and 9 days for ‘Aromas’, ‘Diamante’ and ‘Selva’ fruits stored in air and it was extended by 2, 2 and 4 days, respectively, by the CO₂-enriched atmosphere. However, the level and proportion of flavor components (sugars, organic acids, aroma compounds) and fermentative metabolites, as well as the results of sensory evaluations, indicated that the flavor life was shorter than postharvest life based on appearance in ‘Aromas’ fruit stored in air (5 vs. 7 days) and in CO₂-stored ‘Aromas’ (7 vs. 9 days) and ‘Selva’ (11 vs. 13 days) fruit. ‘Selva’ and ‘Diamante’ strawberries retained their flavor quality during storage at 5 °C in air for 9 days and CO₂-stored ‘Diamante’ fruit for 11 days.     

Effect of non-conventional atmospheres and bio-based packaging on the quality and safety of Listeria monocytogenes-inoculated fresh-cut celery (Apium graveolens L.) during storage

The increased consumption of fresh-cut celery has led to the need to explore packaging alternatives for fresh-cut celery that can meet consumer, market, and industry needs. In this study, the effect of bio-based packaging and non-conventional atmospheres on the quality and safety of chlorine-sanitized celery sticks stored at 7 °C was investigated. Two materials differing in permeability [a bio-based polyester (polylactic acid (PLA)) and a petroleum-based polyolefin (polypropylene/low density polyethylene (PP/PE)] and four initial gas compositions [air (A-PLA or A-PP/PE), 95 kPa O₂ + 5 kPa N₂ (O₂-PLA), 99 kPa N₂ + 1 kPa O₂ (N₂-PLA), and 6 kPa O₂ + 12 kPa CO₂ + 82 kPa N₂ (CO₂-PLA)] were evaluated. Changes in headspace composition, weight loss, surface and cut end color, texture, ethanol content, appearance, and growth of Listeria monocytogenes on inoculated celery sticks were assessed during 21 d of storage. Active MAP (CO₂-PLA) out-performed passive MAP (A-PLA) in maintaining celery stick quality but not safety. Conventional active MAP (CO₂-PLA) out-performed non-conventional active MAPs (O₂-PLA and N₂-PLA) in maintaining celery stick quality throughout storage, but O₂-PLA suppressed L. monocytogenes growth while CO₂-PLA promoted growth during the first 10 d of storage. PLA and PP/PE materials affected celery stick quality but not Listeria growth. This study shows that the initial gas composition and packaging material both impact the quality and safety of celery sticks. Overall, the combination PLA and 95 kPa O₂ proved most beneficial in maximizing both the safety and quality of celery sticks during one week of storage at 7 °C.     

Low UV-C illumination for keeping overall quality of fresh-cut watermelon

The effects of four pre-packaging UV-C illumination doses (1.6, 2.8, 4.8 and 7.2 kJ m^?2) on quality changes of watermelon cubes stored up to 11 days at 5 °C were studied. Non-treated cubes were used as a control. Higher UV-C doses induced slightly higher CO₂ production throughout the storage period, while no changes in C₂H₄ production were monitored. However, UV-C did not significantly affect the final gas partial pressures within modified atmosphere packages where levels of 3–6 kPa O₂ and 13–17 kPa CO₂ were reached for all treatments. UV-C decreased microbial counts just after illumination. After 11 days at 5 °C, mesophilic, psycrophilic and enterobacteria populations were significantly lower in UV-C treated watermelon. Slight changes in CIE colour parameters were observed. According to sensory quality attributes, control and low UV-C treated cubes (1.6 and 2.8 kJ m^?2) can be stored for up to 11 days at 5 °C while the maximum shelf-life of moderate to high UV-C treated fruit was 8 days at 5 °C. Control cubes showed a 16% decrease in lycopene content after 11 days at 5 °C similar to that found for the high UV-C treatment. However low UV-C treated watermelon cubes preserved their initial lycopene content (2.8 kJ m^?2) or it was slightly decreased (1.6 kJ m^?2). UV-C radiation did not significantly affect the vitamin C content while catalase activity and total polyphenols content considerably declined throughout the storage period. However, total antioxidant capacity markedly increased, independently of UV-C doses. As a main conclusion, UV-C radiation can be considered a promising tool for keeping overall quality of fresh-cut watermelon.     

Flesh quality and lycopene stability of fresh-cut watermelon

Red fleshed watermelons are an excellent source of the phytochemical lycopene. However, little is known about the stability of lycopene in cut watermelon. In this study, lycopene stability and other quality factors were evaluated in fresh-cut watermelon. Twenty melons each of a seeded (Summer Flavor 800) and a seedless (Sugar Shack) variety were cut into 5 cm cubes and placed in unvented polystyrene containers, sealed, and stored at 2 °C for 2, 7, or 10 days. At each storage interval, melons were evaluated for juice leakage, changes in carotenoid composition, color, soluble solids content (SSC), and titratable acidity. Headspace carbon dioxide and ethylene were monitored during storage intervals. Juice leakage after 10 days of storage averaged 13 and 11% for the seeded and seedless melons, respectively. Lycopene content decreased 6 and 11% after 7 days of storage for Summer Flavor 800 and Sugar Shack melons, respectively. β-Carotene and cis lycopene contents were 2 and 6 mg kg⁻¹ for Summer Flavor 800 and Sugar Shack, respectively, and did not change with storage. After 10 days of storage, CIE L¹ values increased while chroma values decreased, indicating a lightening in color and loss of color saturation in melon pieces. Symptoms of chilling injury, such as greatly increased juice leakage, or lesions on cubes, were not seen on the fresh-cut cut watermelon after 10 days storage at 2 °C. Puree pH increased and SSC decreased slightly after storage. Carbon dioxide levels increased and oxygen levels decreased linearly during storage, creating a modified atmosphere of 10 kPa each of CO₂ and O₂ after 10 days. Fresh-cut cut watermelon held for 7 or more days at 2 °C had a slight loss of SSC, color saturation, and lycopene, most likely caused by senescence.     

Modified atmosphere packaging preserves quality of SO2-free ‘Superior seedless’ table grapes

‘Superior seedless’ table grapes were stored for 7 days at 0 °C followed by 4 days at 8 °C + 2 days at 20 °C under modified atmosphere packaging (MAP). Two polypropylene films (PP) were used to generate the MAP, the micro-perforated PP-30 and an oriented PP (OPP). The OPP film was applied with and without fungicide (10 μL of trans-2-hexenal or 0.4 g Na₂S₂O₅ kg⁻¹). As control a macro-perforated PP was used. PP-30 packages reached the lowest O₂ and the highest CO₂ levels. Control clusters showed the highest weight losses and decay while almost no losses occurred under MAP treatments. No changes in softness, skin and/or pulp browning, or cluster shatter were found. After shelf life MAP-treated clusters showed slight to moderate stem browning, except under SO₂ where practically no browning occurred while control clusters showed an extreme stem browning. After shelf life, MAP treatments showed good visual appearance and crunchiness, while control fruits were unmarketable. No off-flavors were detected for MAP treatments except for hexenal-treated berries. No remarkable changes for color, firmness, soluble solids content, pH, titratable acidity and maturity index were detected. Total sugars content at harvest was 200 g L⁻¹ and only slight decreases were found after shelf life for most treatments. Total organic acids content at harvest was 15.4 mg 100 mL⁻¹, which remained quite constant after cold storage and shelf life. The main phenolic compounds were flavan-3-ols (over 85% from the total content), hydroxycinnamic acid derivatives and flavonols, whose total amount at harvest was 140 mg kg⁻¹ in a fresh weight basis. After shelf life only slight decreases in total phenolics occurred in all treatments. As a main conclusion, SO₂-free MAP kept the overall quality of clusters close to that at harvest, with few differences when SO₂ was added.     

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.     

High oxygen combined with high carbon dioxide improvesmicrobial and sensory quality of fresh-cut peppers

The effects of high O₂ and high CO₂ throughout storage on the microbial and sensory quality of fresh-cut bell peppers from two commercial ‘California’ cultivars grown under different climatic conditions were studied. The ‘Meteor’ cultivar was minimally processed in Leuven (Belgium) and the ‘Requena’ cultivar in Cartagena (Murcia, Spain). The storage conditions were (kPa O₂/kPa CO₂/kPa N₂) 100/0/0, 80/15/5, 60/0/40, 50/15/35, 20/15/65 and 21/0.03/≅79 as control. Bell peppers freshly-cut in cubes were stored at 5 °C up to 9–10 days. Changes in total counts of mesophilic, psychrotrophic, yeasts and mould as well as Enterobacteriaceae were monitored. Individual and total sugars and organic acids contents, visual appearance, color, shriveling, off-aroma, crunchiness, flavor and overall quality were also evaluated. The results in both experiments showed that 80 or 50 kPa O₂ combined with 15 kPa CO₂ maintained the main sensory quality attributes and inhibited growth of the spoilage microorganisms and Enterobacteriaceae in minimally processed bell peppers.     

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.     

Extending the shelf life of fresh-cut eggplant with a soy protein–cysteine based edible coating and modified atmosphere packaging

The effect of a soy protein-based edible coating with antioxidant activity, and conventional and superatmospheric modified atmosphere (MA) packaging, on the quality of fresh-cut ‘Telma’ eggplants, was evaluated during storage. In a first experiment, eggplant pieces were dipped in either a coating composed of soy protein isolate (SPI) and 0.5% cysteine (Cys), or water as an uncoated control. Samples were packed in trays under atmospheric conditions to reach a passive MA (MA-P) or two gas mixtures (MA-A: 15 kPa CO₂ + 5 kPa O₂; MA-B: 80 kPa O₂) and were stored at 5 °C. Atmospheric conditions were used as the control conditions (Control). The coated samples packed under MA-B and Control conditions resulted in the highest whiteness index (WI) values during storage, whereas MA-A did not improve the shelf-life of minimally processed eggplants and had the lowest WI values. The MA-B and atmospheric control conditions helped to maintain firmness, whereas the coating helped to maintain the weight loss under MA-A and MA-B. The maximum commercial shelf-life was reached on day 6 for the coated samples packed under atmospheric conditions. In a second experiment, the commercial shelf-life of fresh-cut eggplants was extended to 8 and 9 storage days by increasing the Cys content in the edible coating from 0.5 to 1% under MA-B and Control storage conditions, respectively.     

High CO2 effects on postharvest biochemical and textural properties of white asparagus (Asparagus officinalis L.) spears

The effects of high CO₂ concentration (10% CO₂, 17% O₂) on the changes of functional cell wall components (pectic substances, hemicellulose, cellulose, lignin), mechanical properties, content of free soluble sugars (sucrose, glucose, fructose), and respiration activity were studied in harvested white asparagus spears stored at 10 and 20 °C, respectively, for up to 7 d. Spears stored at 2, 10 and 20 °C in air were studied as controls, where the 2 °C condition indicated the effects of cold storage. During storage, respiration activity declined only slightly, irrespective of the CO₂ and temperature regime. Spears stored at 20 °C under both CA and normal air became less stiff and more elastic, however, tissue toughness increased significantly. Changes in toughness were associated primarily with the dynamics of lignin and cellulose, revealing a strong correlation (r² = 0.81). High CO₂ concentration inhibited the synthesis of cellulose and, to some extent, lignin accumulation at 20 °C. Additionally, elevated CO₂ inhibited the degradation of soluble carbohydrates. In contrast, slightly lower temperatures of 10 °C in combination with high CO₂ did not have a pronounced effect on changes in structural carbohydrates (lignin, cellulose, hemicellulose and pectins). The effect low temperature (2 °C) under normal atmosphere conditions resulted in the inhibition of cell wall changes in asparagus spears.     

Off-odour development in modified atmosphere packaged baby spinach is an unresolved problem

A major problem associated with minimally processed baby spinach (Spinacia oleracea L.) is strong off-odours when stored under modified atmosphere packaging (MAP) with low O₂ and high CO₂. Although the influence of O₂ and CO₂ levels on the quality and shelf-life of baby spinach has been extensively studied, results have been inconsistent and the benefits and disadvantages are not well understood. In this study, the effects of 3 different MAP conditions with low O₂ with CO₂ (stabilizing near 1% O₂ + 11% CO₂), low O₂ alone (stabilizing near 1% O₂, CO₂ scrubber) and moderate O₂ with CO₂ (stabilizing near 10% O₂ + 9% CO₂) were studied during storage at 7 °C for 12 days. Different parameters related to physiology, tissue structure, microbial population and metabolite production were evaluated. Samples exposed to low O₂ with CO₂ had the lowest quality at the end of storage due to high development of off-odours, while off-odours of spinach in low O₂ alone were intermediate but higher than in moderate O₂ with CO₂. Increasing CO₂ concentration significantly increased tissue damage with ammonia release and decreased protein content. Decreasing O₂ concentration significantly reduced the development of aerobic psychrophilic bacteria and Pseudomonas. Senescence occurred more rapidly in baby spinach held in moderate O₂ with CO₂. Baby spinach quality remained acceptable during 7 days of storage at 7 °C, independent of MAP conditions tested. Appropriate MAP for baby spinach must be associated with maintenance of quality and extension of shelf-life.