Vitamin C in broccoli (Brassica oleracea L. var. italica) flower buds as affected by postharvest light,UV-B irradiation and temperature

In this study, the changes in vitamin C, l-ascorbic acid (AA) and l-dehydroascorbic acid (DHA) levels in broccoli flower buds were examined during pre-storage and storage periods, simulating refrigerated transport with wholesale distribution and retail, respectively. Broccoli heads were pre-stored for 4 or 7 days at 0 °C or 4 °C in the dark and then stored for 3 days at 10 °C or 18 °C. During storage the broccoli heads were exposed for 12 h per day to three different levels of visible light (13, 19 or 25 μmol m⁻² s⁻¹) or a combination of visible light (19 μmol m⁻² s⁻¹) and UV-B irradiation (20 kJ m⁻² d⁻¹), or they were stored in the dark. The vitamin C content in broccoli flower buds during storage was significantly affected by pre-storage period and temperature. Higher vitamin C levels in flower buds after storage were observed for broccoli heads pre-stored for 4 days or at 0 °C as compared to those pre-stored for 7 days or at 4 °C. Storage temperature also affected vitamin C in broccoli flower buds, with higher levels observed for broccoli stored at 10 °C than at 18 °C. Hence, vitamin C in broccoli flower buds was demonstrated to decrease together with increasing pre-storage period, pre-storage temperature and storage temperature. AA in broccoli flower buds was influenced mainly by storage temperature and to a minor extent by pre-storage temperature. The DHA level and DHA/AA ratio were stable in flower buds of broccoli pre-stored for 7 days, whereas increasing tendencies for both DHA level and ratio were observed after pre-storage for 4 days. These results indicate a shift in the ascorbate metabolism in broccoli flower buds during storage at low temperatures, with its higher rate observed for broccoli pre-stored for shorter time. There were no effects of the light and UV-B irradiation treatments on vitamin C, AA and DHA levels in broccoli flower buds.     

Combined effect of ultrasound,mild heat shock and citric acid to retain greenness,nutritional and microbiological quality of minimally processed broccoli (Brassica oleracea L.): An optimization study

Response surface methodology (RSM) and Box–Behnken design were used to study the combined hurdle effect of mild heat time (1–5 min) at 50 °C, ultrasonic processing time (0–10 min) and citric acid concentration (0–2%) on the quality of refrigerated broccoli after 10 d of storage at 5 °C. Treatment effects were evaluated on weight loss, superficial colour (hue angle (H°) and total colour difference (ΔE)), headspace gas composition (O₂ and CO₂), overall browning potential, chlorophyll content, ascorbic acid content, mesophilic counts and overall visual quality (OVQ) and optimize the process by means of the desirability function. Predicted models were found to be significant with high regression coefficients (91–97%). High regression coefficients indicated that second-order polynomial models could be used to predict and optimize the quality retention in minimally processed broccoli during storage. The mesophilic counts, ascorbic acid content and the overall visual quality were significantly influenced by the three independent variables either independently or interactively. Both thermal and ultrasonic treatments were found to be critical factors influencing changes in chlorophyll content, O₂ concentration inside the package, hue angle and ΔE. On the other hand, thermal treatment and citric acid concentration were found to be significant on overall browning potential. By using the desirability function approach and considering superficial colour parameters, O₂ concentration, mesophilic counts, browning potential, ascorbic acid and chlorophyll content, the optimum processing conditions were 7.5 min of ultrasonic treatment, 3 min of a heat shock treatment and a citric acid concentration of 1.5%. These results were in good agreement with the maximum found from the canonical analysis performed from the response surface when only considering sensorial analysis. Under these optimal processing conditions it is possible to employ citric acid treatment in combination with ultrasonic and thermal treatments as hurdles for retention of green colour, nutritional quality, microbial control and for extending shelf life of refrigerated minimally processed broccoli.     

Impact of edible coatings and mild heat shocks on quality of minimally processed broccoli (Brassica oleracea L.) during refrigerated storage

The effects of edible coatings and mild heat shocks on quality aspects of refrigerated broccoli were studied. Minimally processed broccoli was coated with either chitosan or carboxymethyl-cellulose with or without a previous application of a mild heat shock of 1.5 min at 50 °C. Product was packaged in multilayered polyolefin bags and stored at 5 °C for 18 d. Quality parameters such as weight loss, texture, colour, ascorbic acid content, total chlorophyll content, oxygen concentration inside the bags, browning potential, mesophilic aerobic counts, and sensory quality, were evaluated during storage. Edible coatings exhibited a beneficial impact on broccoli quality. The weight loss in uncoated broccoli was found to be between 2 and 5 times higher compared to coated samples. During storage, coated florets from both thermally and non-thermally treated samples, presented higher retention of the (?a*/b*) ratio indicating better green colour retention and a reduced rate of floret yellowing. Chitosan coating always presented the lower ascorbic acid degradation rates (twofold lower compared with control samples). Broccoli texture for uncoated samples increased significantly during storage. However, for carboxymethyl-cellulose coated broccoli a slight increase in texture was observed while for chitosan coated broccoli no significant changes in texture were observed throughout the storage period. After the edible coating application the microbial broccoli load dropped by around 1.5 and 0.9 logarithmic units in chitosan and carboxymethyl-cellulose films, respectively. During storage, the application of chitosan coating significantly reduced total microbial counts in the thermally and non-thermally treated uncoated samples. Among the assayed edible coatings, chitosan effectively maintained quality attributes and extended shelf life of minimally processed broccoli. The single application of a mild heat shock had a measurable influence in reducing weight loss, enzymatic browning in broccoli stems, and in delaying yellowing of broccoli florets. Moreover, chitosan coating combined with a mild heat shock showed the best performance for long-term refrigerated storage of minimally processed broccoli.     

UV-C treatment delays postharvest senescence in broccoli florets

Central broccoli heads (cv. de Cicco) were harvested and treated with UV-C light (4, 7, 10, or 14 kJ m⁻²). All treatments delayed yellowing and chlorophyll degradation at 20 °C but the irradiation dose of 10 kJ m⁻² allowed retaining the highest chlorophyll content yet had lower amounts of pheophytins than every treatment other than 7 kJ m⁻². This dose was selected to analyze the effect of UV-C on postharvest broccoli senescence at 20 °C. The UV-C treatment delayed yellowing, chlorophyll a and b degradation, and also the increase in pheophytins during storage. The activity of chlorophyll peroxidase and chlorophyllase was lower in UV-C treated broccoli. Instead, Mg-dechelatase activity increased immediately after the treatment, but after 4 and 6 d this activity was lower in UV-C treated florets than in controls. Treated broccoli also displayed lower respiration rate, total phenols and flavonoids, along with higher antioxidant capacity. The results suggest that UV-C treatments could be a useful non-chemical method to delay chlorophyll degradation, reduce tissue damage and disruption, and maintain antioxidant capacity in broccoli.     

Effects of hot water treatment on the storage stability of satsuma mandarin as a postharvest decay control

Satsuma mandarins (Citrus unshiu Marc., cv. Gungchun) of an early harvesting cultivar were treated by hot water dipping at 52 °C for 2 min, 55 °C for 1 min, and 60 °C for 20 s, and then stored at 5 °C for 3 weeks and subsequently at 18 °C for 1 week (simulated shelf-life) to examine the possible use of hot water treatment (HWT) as an environmentally benign method to maintain mandarin quality characteristics during postharvest storage and sale. The initial respiration rate, just after heat treatment, was significantly higher in the treated fruit than in the untreated controls. During storage, however, the respiration rate was at a similar level in all treatments. HWT also had no adverse effects on quality attributes, including pH, titratable acidity, soluble solids contents, weight loss, firmness and peel color. The development of stem-end rots, mold decay, and black rots was manifestly lower in heat-treated fruit than in untreated controls. Sensory evaluation showed that HWT at 60 °C for 20 s markedly improved fruit appearance, making them cleaner and glossier. The results confirmed that hot water dipping could be applied to satsuma mandarin as an effective pretreatment to maintain postharvest quality during storage and marketing.     

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.     

Pre-storage hypobaric treatments delay fungal decay of strawberries

Fungal decay is a major cause of postharvest losses in strawberries. The traditional approach for controlling fungal decay is the use of fungicides. However, the use of fungicides has been questioned as a sustainable and safe method, and is also prohibited in many countries. One potential physical method for reducing fungal decay is application of a short-term hypobaric treatment prior to storage. In this study efficacy of postharvest hypobaric treatments to control natural rot development in strawberries was evaluated. Strawberries were treated with hypobaric pressures (25 kPa_a, 50 kPa_a and 75 kPa_a) for 4 h at 20 °C and subsequently stored at 20 °C or 5 °C. A 50 kPa_a treatment consistently delayed rot development in samples stored at either temperature confirming that the technique has potential as a non-chemical treatment. Moreover 50 kPa_a treatments did not affect weight loss and firmness at either 20 °C or 5 °C. An initial increase in respiration rate was observed in 50 kPa_a treated samples potentially indicating mild stress due to hypobaric treatment. An in vitro fungal study found that 50 kPa_a treatment for 4 h did not affect the rate of radial growth of colonies of Botrytis cinerea and Rhizopus stolonifer, providing further evidence that the potential mechanism of hypobaric treatment is induction of the defence system within the fruit rather than a direct effect on fungal viability. Further molecular and biochemical research is required to evaluate the possible stimulation of resistance in fruit through short-term hypobaric treatments.     

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.     

Responses of 1-MCP application in plums stored under air and controlled atmospheres

The potential of 1-MCP for controlling ripening in ‘Angeleno’ plum fruit under air and controlled atmosphere (CA) storage was explored, and the possibility that 1-MCP can inhibit development of brown rot caused by Monilinia laxa and internal breakdown in ‘Fortune’ and ‘Angeleno’ plums tested. After harvest, fruit were exposed to 300 and 500 nl l⁻¹ (in 2003) and 500 nl l⁻¹ 1-MCP (in 2004) at low temperatures (0–3 °C) for 24 h. After treatment the plums were stored in air at 0 °C and ‘Angeleno’ fruit were also stored in CA storage (1.8% O₂ + 2.5% CO₂). Following storage, fruit were kept at 20 °C. In ‘Angeleno’ fruit, 1-MCP was effective in delaying the loss of firmness and colour changes during holding at 20 °C. 1-MCP reduced brown rot in fruit stored in CA but no significant reduction was found in air storage. Internal breakdown, a major physiological storage disorder in plums, was inhibited by 1-MCP treatment. Furthermore, since 1-MCP applied in air storage showed better results than the control in CA conditions, an application of 1-MCP before air storage could be the best way to reduce the ripening process for short or medium storage periods (40 and 60 days). CA storage plus 1-MCP treatment could be used for long periods (80 days).     

Opening of cut Iris x hollandica flowers as affected by temperature,dry storage,and light

Flower opening in Iris (Iris x hollandica) depends on elongation of the pedicel + ovary. This elongation lifts the bud above the point where the sheath leaves no longer mechanically inhibit lateral tepal movement. We here report on the effects on flower opening of storage at various temperatures, of holding the flowers dry rather than in water, and of a 12 h light/dark cycle instead of darkness, in cv. Blue Magic. During 3 d of storage in darkness at 11 °C or 6 °C the flowers placed in water opened. Flowers stored at 3.0 °C did not open during the storage period but did so during subsequent vase life at 20 °C. Flowers stored in water at 0.5 °C remained closed, even during subsequent vase life at 20 °C. None of the flowers that were stored dry for 3 d at 15 °C, 11 °C, 6 °C, 3 °C or 0.5 °C opened during vase life. Compared to flowers placed in continuous darkness, a rhythm of 12 h light and 12 h darkness inhibited opening during a 3 d storage period at 20 °C. It is concluded that cut Iris flowers (a) can be stored in water at 3 °C for more than a week, but cannot be stored for 3 d or more in water at 15 °C, 11 °C, 6 °C or 0.5 °C, and (b) cannot be stored dry for long (under the present conditions 3 d or longer) at any of these temperatures. Iris flowers were found to be chilling-sensitive, although only at temperatures of about 0.5 °C.     

Influence of self-produced CO2 on postharvest life of heat-treated strawberries

Strawberries cv. Selva (75 or 90% superficial red color) were packaged with films having different permeability properties, heat-treated in an air oven (45 °C, 3 h), stored at 0 °C for 0, 7 or 14 days and then transferred to 20 °C for 2 days. The percentage of CO₂ in the package atmosphere and the effect of heat treatment on the following parameters were recorded: weight loss, external color, lightness, anthocyanin content, firmness, titratable acidity, pH, total sugar, total phenol and fruit decay. The application of heat treatment alone reduced fungal decay and delayed red color development and fruit softening. When the treatment was performed on fruit in films that allowed retention of part of CO₂ produced during heating, the delay of fruit softening and color development and the reduction of decay were enhanced. The benefit for 90% red fruit was minimal and decay development was only delayed by 1 day. The results of this work indicate that the well-known benefits of heat treatment could be considerably improved by performing the treatment in the presence of low permeability films, with the aim of retaining the CO₂ produced by the temporary increase in fruit respiration during the heating.     

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.     

Effects of base removal and heat treatment on visual and nutritional quality of minimally processed leeks

Freshly harvested leeks (Allium ampeloprasum L. var. porrum) were trimmed (leaf tips, roots), had the decayed leaves removed, washed with tap water, cut at 50 cm length and subjected to heat treatment at 55 °C for 0 and 17.5 min. They were then trimmed at the root base and leaves to produce stalks 22 cm in length with or without removal of a 2 cm portion of the base. Minimally processed leeks were tray-packaged, wrapped with 16 μm stretch film and stored at 10 °C for 7 days to determine the effects of base removal and heat treatment on visual (leaf growth, fresh weight loss and discoloration) and nutritional quality after storage. CO₂ and ethylene concentrations of packages containing minimally processed leeks showed a wound-induced pattern typical of other fresh cut vegetable tissues. Base removal did not significantly affect respiration but increased ethylene production, while heat treatment increased respiration rate and suppressed ethylene production. Storage of minimally processed leeks at 10 °C for 7 days resulted in a slight decrease of chroma and hue angle of base cross section as well as a decrease of chroma of the upper cross section. Heat treatment prevented the decrease of chroma of the base and upper cross section. Base removal reduced, but did not totally control leaf growth of stored minimally processed leeks. Moreover, it resulted in a decrease of dry matter, soluble solids, total soluble phenols, antioxidant capacity and total thiosulfinates at the end of the storage. A combination of base removal and heat treatment efficiently controlled leaf growth, but these treatments resulted in increased fresh weight and total thiosulfinate loss.     

Respiration rate response of four baby leaf Brassica species to cutting at harvest and fresh-cut washing

The influence of the first and second cutting at harvest on the physiological response of four baby leaf Brassica species was studied. The species were salad rocket (Eruca vesicaria), wild rocket (Diplotaxis tenuifolia), mizuna (Brassica rapa L. ssp. nipposinica) and watercress (Nasturtium officinale) stored at 1, 4, 8 and 12 °C. In addition, the microbial and metabolic behaviours of baby leaves were evaluated after different washing treatments including water, ozonated water (10 mg L⁻¹ total dose), ozonated water activated with ultraviolet C light (UV-C) and heat shock wash (50 °C, 1 min). Temperature had a significant effect on both respiration rate and post-cutting life. The production of CO₂ increased between 2- and 4-fold when temperature increased from 1 to 12 °C. Minor differences in leaf respiration rate between the first and second leaf cutting were observed for salad rocket and wild rocket, while leaves from the second cutting of mizuna and watercress leaves had a higher respiration rate than from the first cutting. Ozone, and ozone combined with UV-C, were the most efficient washing treatments in reducing total mesophilic counts, while heat shock treatment did not affect them. Additionally, naturally occurring Listeria spp. were controlled well in wild rocket and mizuna (<1 log cfu g⁻¹) when the ozone treatments were applied. On the other hand, respiration rates of the Brassica species were not substantially affected by the washing treatments when stored at 4 °C. Maximum CO₂ production was observed immediately after washing but decreased during the first 24 h of storage. Baby leaves washed with cold water consistently showed a lower respiration rate than the other washing treatments. Heat shock was the washing treatment that most influenced the increase in the respiration rate of baby leaves during storage at 8 °C.     

Variation of total FOS,total IOS,inulin and their related-metabolizing enzymes in burdock roots (Arctium lappa L.) stored under different temperatures

Burdock roots were stored for six weeks at three temperatures, 0, 15 and 20 °C, and activity of sucrose hydrolase (SH), 1-kestose hydrolase (1-KH), inulin hydrolase (InH), sucrose:sucrose 1-fructosyltransferase (1-SST) and fructan:fructan 1-fructoslytransferase (1-FFT) were assessed. Simultaneously, total fructooligosaccharides (FOS), total inulooligosaccharides (IOS) and inulin were also assessed during storage. During storage, SH showed an irregular variation at 15 and 20 °C, and was significantly higher at 0 °C showing a continuous increase during the storage period. 1-KH decreased progressively at 15 and 20 °C, but showed a sharp increase at 0 °C after two weeks and decreased afterwards. InH showed a different although more regular pattern by decreasing progressively at 0, 15 and 20 °C. However, the decrease was more significant at 15 and 20 °C during the first two weeks, while at 0 °C the decrease was significant after four weeks storage. 1-SST and 1-FFT activities decreased progressively in a pseudo-linear regression during storage, and showed similar patterns. At 15 and 20 °C, total FOS increased during the first three weeks then decreased, while at 0 °C FOS increased progressively during storage. Total IOS increased during storage, however, this increase was much higher at 0 °C than that observed at 15 and 20 °C. Inulin content decreased during storage and final content was lower at 20 °C. The inulin to total FOS plus total IOS ratio decreased sharply during the first two weeks of storage, then progressively during the last four weeks, while the ratio of hydrolyzing to synthesizing activities was quite stable at 15 and 20 °C, but showed a peak at 0 °C after two weeks. The results suggest that carbohydrate metabolism in stored burdock depends partly on temperature and other physiological factors.     

Effect of 1-methylcyclopropene (1-MCP) on storage life of durian fruit

Fruit of cv. Monthong durian (Durio zibethinus) were treated with 0 (control) or 500 nL L⁻¹ 1-MCP for 12 h at 25 °C. Fruit were then stored at 15 °C. To determine storage life, every 3 days a batch of fruit was transferred to 25 °C. The time to ripeness (adequate eating quality) at 25 °C in controls (no 1-MCP) decreased from 5 days in freshly harvested fruit to 3 days after 18 days of storage at 15 °C. Storage life was considered adequate if the time to ripeness was ≥3 days. The storage life at 15 °C of control fruit (no 1-MCP) was therefore 18 days. After the 1-MCP treatment the time to ripeness at 25 °C was 7 days in fresh fruit, while in fruit stored at 15 °C for 30 days it was about 3 days. The storage life at 15 °C of 1-MCP-treated fruit was therefore 30 days. Pulp firmness and pulp total soluble solids (TSS) were determined after 3 day storage intervals at 15 °C and when the fruit was ripe at 25 °C. These parameters were only slightly affected by the 1-MCP treatment. Furthermore, 1-MCP had no effect on pulp color, but delayed yellowing of the fruit exterior. It is concluded that treatment with 1-MCP before storage at 15 °C extended storage life from 18 to 30 days.     

Interaction of temperature control deficiencies and atmosphere conditions during blueberry storage on quality outcomes

Southern hemisphere blueberry producers often export their products through extended supply chains to Northern hemisphere consumers. During extended storage, small variations in temperature or atmosphere concentrations may generate significant differences in final product quality. In addition, relatively short delays in establishing cool storage temperatures may contribute to quality loss. In these experiments a full factorial analysis was done of the effects of three cooling delays (0, 12 or 24 h at 10 °C), three atmosphere concentrations (air, 10% CO₂ + 2.5% O₂ and 10% CO₂ + 20% O₂) and two storage temperatures (0 °C and 4 °C) which were assessed for their impact on final quality, measured as weight loss, firmness and rot incidence. Two blueberry cultivars were studied: ‘Brigitta’, a highbush cultivar, and ‘Maru’, a rabbiteye. Delays in cooling had a small effect on final product weight, whereas variation in storage temperature and atmosphere during simulated transport influenced both firmness and rot incidence. Atmospheres with 10% CO₂ reduced decay incidence, particularly at low oxygen concentration (2.5% O₂), although the latter conditions tended to soften fruit. In order to achieve optimal postharvest storage for blueberries, minimising temperature variability in the supply chain is important, as is finding the potentially cultivar-specific optimal combination of high CO₂ and low O₂ concentration that results in simultaneously minimising rot incidence and induced softening.     

Respiration and quality responses of sweet cherry to different atmospheres during cold storage and shipping

Most sweet cherries produced in the US Pacific Northwest and shipped to distant markets are often in storage and transit for over 3 weeks. The objectives of this research were to study the effects of sweet cherry storage O₂ and CO₂ concentrations on the respiratory physiology and the efficacy of modified atmosphere packaging (MAP) on extending shelf life. Oxygen depletion and CO₂ formation by ‘Bing’ and ‘Sweetheart’ cherry fruit were measured. While respiration rate was inhibited linearly by reduced O₂ concentration from 21% to 3–4% at 20 °C, it was affected very little from 21% to ∼10% but declined logarithmically from ∼10% to ∼1% at 0 °C. Estimated fermentation induction points determined by a specific increased respiratory quotient were less than 1% and 3–4% O₂ for both cultivars at 0 and 20 °C, respectively. ‘Bing’ and ‘Sweetheart’ cherry fruits were packaged (∼8 kg/box) in 5 different commercial MAP box liners and a standard macro-perforated polyethylene box liner (as control) and stored at 0 °C for 6 weeks. MAP liners that equilibrated with atmospheres of 1.8–8.0% O₂ + 7.3–10.3% CO₂ reduced fruit respiration rate, maintained higher titratable acidity (TA) and flavor compared to control fruit after 4 and 6 weeks of cold storage. In contrast, MAP liners that equilibrated with atmospheres of 9.9–14.4% O₂ + 5.7–12.9% CO₂ had little effect on inhibiting respiration rate and TA loss and maintaining flavor during cold storage. All five MAP liners maintained higher fruit firmness (FF) compared to control fruit after 6 weeks of cold storage. In conclusion, storage atmospheres of 1.8–14.4% O₂ + 5.7–12.9% CO₂ generated by commercial MAP, maintained higher FF, but only the MAP with lower O₂ permeability (i.e., equilibrated at 1.8–8.0% O₂) maintained flavor of sweet cherries compared to the standard macro-perforated liners at 0 °C. MAP with appropriate gas permeability (i.e., equilibrated at 5–8% O₂ at 0 °C) may be suitable for commercial application to maintain flavor without damaging the fruit through fermentation, even if temperature fluctuations, common in commercial storage and shipping, do occur.