Postharvest Quality of Strawberry Fruit (<Emphasis Type="Italic">Fragaria x Ananassa</Emphasis> Duch cv. Albion) as Affected by Ozone Washing: Fungal Spoilage,Mechanical Properties,and Structure

Storage life of strawberry fruit is limited due to its high softening rate and susceptibility to fungal attack. Thus, it is of interest to develop and improve preservation techniques to reduce postharvest losses. The aim of this study was to evaluate the effect of ozonized water washing (maximum concentration of 3.5 mg L^?1; 5–15 min) on fungal spoilage, water loss, mechanical properties, and structure of strawberries (cv. Albion) harvested in different years and stored at 5 °C. The effect of ozone treatment on decontamination and weight loss was dose-dependent. Ozonization for 5 min significantly reduced fungal incidence (~?22–25% lesser than control) and weight loss of strawberries throughout storage. High doses (10 or 15 min) did not reduce significantly fungal growth in relation to control, although weight loss in fruit treated for 15 min was higher than control. In both harvest years studied, cold storage provoked a diminution in deformability modulus and an increase in deformation but a significant effect of treatment was not observed. These changes were correlated with alteration of cell walls and turgor loss. Otherwise, cuticular membrane of strawberries treated for 5 min was observed thicker and more electron dense than in fruit ozonized for 15 min or control. It could partially explain the lower moisture loss observed in 5-min treated fruit. Results showed that ozonized water washing for 5 min can be an alternative strategy for extending postharvest strawberry shelf-life by decreasing fungal decay and water loss along cold storage, without affecting mechanical parameters.     

RELATIONSHIP OF TREATMENT OF FRESH STRAWBERRIES TO THE QUALITY OF FROZEN FRUIT AND PRESERVES1

‘Cardinal’ strawberries were hand picked and stored 1 day at 21°C to enhance softening. Three separate preprocessing experiments were conducted to determine the effects of style of pack, 0.18% calcium (Ca) dips, 0.3% low methoxyl pectin (LMP), 40° Brix sucrose dips, heat of 70°C, vacuum at 172 mm Hg and drying to 70% moisture on quality and firmness of frozen-then-thawed and preserved strawberries. The greatest firming effect on frozen-then-thawed fruit was due to Ca and pectin. Sliced fruit was firmed more than whole fruit by the Ca and pectin treatments. Drained weight loss was reduced by pectin, Ca, sucrose, heat and vacuum in frozen-then-thawed fruit. Drained weight losses were the same or greater among treatments in preserves. The firmness and wholeness of preserves was increased by Ca, vacuum, 40° Brix sucrose, heat and to a lesser extent drying, but individual effects were not additive. The drying treatment reduced color quality.     

Growth of Botrytis cinerea and Strawberry Quality in Ozone-enriched Atmospheres

Botrytis cinerea cultures were stored on potato dextrose agar in air with or without 1.5 μL/L ozone at 2 °C. Cultures stored in the presence of ozone grew slower. Strawberry fruits (Fragaria×ananassa cv. Camarosa) were stored for 3 d at 2 °C in air with or without 1.5 μL/L ozone and then transferred to room temperature. Each group was inoculated with B. cinerea grown in air with or without ozone. Visible mycelial growth developed more rapidly on fruit previously stored in air. Ozone‐enriched cold storage of naturally infected ‘Camarosa’ fruit reduced decay incidence, weight loss, and fruit softening, but resulted in a reversible loss of fruit aroma.     

The Release of Carotenoids from a Light-Protected Antioxidant Active Packaging Designed to Improve the Stability of Soybean Oil

An antioxidant active packaging was developed by coextruding two layers of high-density polyethylene (HDPE). Bags were made with the film in which the inner layer, designed to be in contact with food, contained marigold flower (Tagetes erecta) extract rich in carotenoids. The outer layer of the film was added with titanium dioxide (TiO₂) to decrease the effect of commercial lighting on the degradation of carotenoids. Four bilayer films were produced: added with TiO₂ and carotenoids, added with carotenoids, added with TiO₂, and with no additives at all (control film). Degradation of color and astaxanthin in the films was delayed by the addition of the TiO₂ when they were stored under commercial lighting at 25 °C. Bags made of these films produced an improvement on the soybean oil stability at 25 °C as a result of a synergic effect of light protection by TiO₂ and carotenoids release. This release was measured as diffusion coefficients of carotenoids from the films toward soybean oil at 10, 25, and 40 °C (2.10–19.26?×?10^?11 cm² s^?1) with activation energy of 53.66 kJ mol^?1. In conclusion, the combination of the two layers of HDPE added with TiO₂ and carotenoids introduced opacity and permitted to extend the active effect of the films in contact with soybean oil. Moreover, the effect of temperature on the diffusion of carotenoids showed that this new active packaging is able to exert its function in conditions of transport, storage, and commercialization of food.     

Controlling Temperature and Water Loss to Maintain Ascorbic Acid Levels in Strawberries During Postharvest Handling

‘Chandler’, ‘Oso Grande’ and ‘Sweet Charlie’ strawberries were stored for 8 days at 1 or 10°C, or 4 days at 20°C, either unwrapped or wrapped in PVC film to retard were conducted during the 1 water loss. Total ascorbic acid (AA) content was expressed on a dry weight basis to correct for water loss differences between treatments. Loss of AA was low and did not differ between wrapped treatments at 1 and 10°C, but was much greater at 20°C. Wrapping reduced AA loss by 5-fold at 1 and 10°C and by 2-fold at 20°C. The effect was not due to modification of O₂ and CO₂ levels in wrapped treatments, which was minimal. The results indicate that water loss had a greater effect on AA levels than temperature. Combining wrapping with storage at 1 or 10°C reduced AA loss by 7.5-fold compared to unwrapped strawberries stored at 20°C.     

Determining the physical stability and water–solid interactions responsible for caking during storage of alpha-anhydrous glucose

Typically, a crystalline powder is considered reasonably stable below it deliquescence point (RH₀), however, caking has been reported for some materials below their RH₀. The critical relative humidity (RH) values for caking and hydrate formation in alpha-anhydrous glucose (α-AG) and α-AG partitioned into three particle sizes were assessed using saturated salt slurries ranging from 0 to 84 % RH at 25 °C for 20 weeks. The degree of caking was determined by a five-point visual physical stability scale, from free flowing with minimal clumping (1) to fully caked (5), and X-ray powder diffraction was used to determine the composition of the samples. Caking was observed in α-AG during storage at 68 % RH at 25 °C and the severity of caking increased with increasing RH. Fine particle α-AG caked during storage at 64 % RH, whereas medium and large particle α-AG caked at 68 and 75 % RH, respectively, at 25 °C. Caking was observed in the absence of deliquescence, amorphous content, and hydrate formation; therefore, it is proposed that capillary condensation leads to caking in α-AG below its RH₀. Capillary condensation caking occurs at a specific RH (termed RH_cc) where direct condensation of moisture into confined spaces, such as particle contact points or surface defects, causes the formation of liquid bridges, which may solidify over time without changes in RH or temperature. To avoid caking, α-AG should be stored below its RH_cc, which is highly dependent on particle size; and to avoid conversion to glucose monohydrate, α-AG, regardless of particle size, should be stored below 64 % RH at 25 °C.     

Edible Active Coatings Based on Pectin,Pullulan, and Chitosan Increase Quality and Shelf Life of Strawberries (Fragaria ananassa)

Edible active coatings (EACs) based on pectin, pullulan, and chitosan incorporated with sodium benzoate and potassium sorbate were employed to improve the quality and shelf life of strawberries. Fruits were washed, disinfected, coated by dipping, packed, and stored at 4 °C for 15 d. Application of EACs reduced (P < 0.05) weight loss and fruit softening and delayed alteration of color (redness) and total soluble solids content. In contrast, pH and titratable acidity were not affected (P > 0.05) throughout storage, and ascorbic acid content was maintained in pectin‐EAC coated strawberries. Microbiological analyses showed that application of EACs reduced (P < 0.05) microbial growth (total aerobic counts, molds, and yeasts) on strawberries. Chitosan‐EAC coated strawberries presented the best results in microbial growth assays. Sensory quality (color, flavor, texture, and acceptance) improved and decay rate decreased (P < 0.05) in pectin‐EAC, pullulan‐EAC, and chitosan‐EAC coated strawberries. In conclusion, EACs based on polysaccharides improved the physicochemical, microbiological, and sensory characteristics, increasing the shelf life of strawberries from 6 (control) to 15 d (coated fruits).     

Increasing Cold Tolerance of Cactus Pear Fruit by High-Temperature Conditioning and Film Wrapping

Pre-storage high-temperature conditioning (HTC, 38 °C, and 95% RH for 24 h) and individual film wrapping (IFW) with a perforated polyolefinic heat-shrinkable film were used as individual treatments or in combination to mitigate chilling injury of first crop cactus pear cv ‘Gialla’. The fruit was stored for 21 days at either 2 or 8 °C (CS) plus 1 week of simulated marketing conditions (SMC) at 20 °C. The reduction in peel disorders and decay in HTC-treated fruit stored at 2 °C was comparable to that detected in control fruit stored at 8 °C. IFW was more efficient than HTC in reducing peel disorders, almost completely inhibited weight loss, and preserved freshness in fruit stored at 8 °C as well as in those stored at 8 °C. The internal quality of the fruit (pH, total soluble solids, titratable acidity, vitamin C, polyphenols, betaxanthins, antioxidant capacity, acetaldehyde, and ethanol) was slightly affected by treatments. Combining HTC with IFW did not improve fruit tolerance to low temperature but reduced decay with respect to individual treatments. IFW with a perforated film in combination with HTC is a good means of overcoming the stringent conditions of cold quarantine treatments, maintaining fruit freshness and reducing decay in cold-stored cactus pears.     

Determining the physical stability and water–solid interactions responsible for caking during storage of glucose monohydrate

A free flowing crystalline powder can develop severe caking if held under humid and/or high temperature storage. In addition, a crystalline hydrate material can experience compositional changes due to hydrate formation or loss if held at too high or low of a storage RH, respectively. Thus, the critical RH values for caking and compositional changes of glucose monohydrate (GM) and GM partitioned into three particle sizes were assessed using saturated salt slurries ranging from 0 to 84 % RH at 25 °C for 20 weeks. Caking was measured using a five-point visual physical stability scale, from free flowing to fully caked, and sample composition was determined using X-ray powder diffraction. Caking was observed in GM during storage at 53–84 % RH at 25 °C and fine particle GM caked at lower RH values than medium and large particle GM. For all GM samples, hydrate loss (via conversion of GM to alpha-anhydrous glucose) occurred at 0 and 11 % RH and hydrate formation (via mutarotation of beta-anhydrous glucose to alpha-anhydrous glucose and conversion to GM) occurred at 53–84 % RH at 25 °C. Particle size did not affect compositional changes during GM storage, but greatly affected caking. Neither deliquescence nor amorphous content were detected in this study and hydrate formation and β-AG content did not cause caking in GM, therefore, decreased flowability was the result of capillary condensation caking. At 25 °C, GM should be stored above 11 % RH to avoid hydrate loss and below 53 % RH to avoid caking.     

Storage quality of strawberry fruit treated by pulsed light: Fungal decay,water loss and mechanical properties

The effect of different pulsed light (PL) doses (2.4–47.8 J/cm²) on water loss, fungal spoilage, mechanical properties and structure of strawberries stored for up to 8 days at 6 °C was studied. Incidence of postharvest molds on strawberry fruits was reduced by over 16–42% with PL application. There were no significant differences in maximal rupture force (F_R), mechanical work (W) and deformability modulus (E_d) values between treated and untreated fruits immediately after treatments. After 8 days storage at 6 °C, untreated strawberries showed a pronounced softening (≈ 48% reduction in F_R), but stored strawberries exposed for 10 s and 40 s to PL presented slight or not significant changes in the mechanical parameters regarding day 0, while F_R and W values of 20 s-PL treated samples were increased by 35% and 88% compared to those at 0 day storage. Micro and ultrastructure changes evaluated by LM and TEM images demonstrated ITW cell wall strengthening and a major integrity of walls of hypodermis cells induced by PL stress, while cell wall disassembly and reduction of cell-to-cell contact were detected in stored untreated fruit. There were no significant differences in weight loss among untreated and PL treated fruits after storage, excepting at the highest PL dose. PL technique would be able to simultaneously provide disinfection and delete softening of the tissues along cold storage. Present results make this non-thermal, residue-free alternative promising for extending shelf-life of traditional and organic strawberry production.Industrial relevanceThe present results demonstrated that pulsed light (PL) treatment is a promising alternative for extending the shelf-life of strawberries. A decrease in fungal incidence and a depletion of softening, important factors which limit the strawberry postharvest storage life, were achieved by the application of PL.     

Effect of heat treatment and individual shrink packaging on quality and nutritional value of bell pepper stored at suboptimal temperature

The goal of this study was to develop a technology for prolonged storage of pepper fruit at low temperature, based on physical treatments and packaging materials. Physical and compositional changes of red bell pepper fruit (Capsicum annuum L. cv.’Selika’) were monitored during 21 days of cold storage (at 2 °C) plus 3 days at 20 °C (market simulation). Fruits were treated with tap and hot water and stored without packaging or sealing each fruit in individual shrink packaging (Cryovac®). This research revealed that individual shrink packaging following prestorage with hot water rinse (55 °C for 15 s) over brushes, significantly reduced weight loss, softening, decay incidence and chilling injury, while maintaining a quality. The wrapped fruit ripened normally (carotenoid content increased) during shelf‐life period, when shifted to 20 °C after unwrapping. This study showed that antioxidant levels of pepper fruit may be preserved during storage.     

Starch-based coatings: effect on refrigerated strawberry (Fragaria ananassa) quality

Edible coatings can provide an alternative for extending post-harvest life of refrigerated fruit and vegetables. The influence of different starch-based coating formulations on quality attributes of strawberries stored at 0°C and a relative humidity of 84·8% was studied. Starch sources were classified according to the amylose content in starch, with medium amylose content (potato and corn) and high amylose content (amylomaize and amylose-rich product). Quality of fruits was evaluated by weight loss, firmness retention, microbial decay, surface colour development, titratable acidity and sugar content. The effects of starch amylose content and glycerol (plasticiser) concentration on coating properties were also analysed. The coatings reduced the number of infected fruits and extended storage life of strawberries by retarding senescence. The addition of glycerol improved coating performance, with 20 g litre⁻¹ the most effective concentration. The starch source had a significant effect on surface colour development, weight loss and firmness retention. Coated strawberries produced the lowest ratios of chromaticity parameters (a/b, red/yellow) with regard to the control fruits, thus retarding senescence. High amylose content starches reduced weight loss, maintained firmness and reduced decay better than medium amylose content starches. © 1998 SCI.     

Improvement of the Quality and the Shelf Life of Figs (<Emphasis Type="Italic">Ficus carica</Emphasis>) Using an Alginate–Chitosan Edible Film

The consumption of fresh figs (Ficus carica) has long been associated with longevity and health benefits. However, fresh figs are highly perishable. An alternative to extend the shelf life of this fruit might be the application of an edible film. Thus, in this study, fig fruits collected at two maturity stages (referred as stages III and IV) were coated with an alginate–chitosan bilayer edible (A–Ch BE) film and the main physiological and quality attributes were evaluated during storage at low temperature (6 °C) at 0, 3, 6, 9, 12, and 15 days of storage. Ethylene and CO₂ productions were considered as physiological parameters, while firmness, color changes, weight loss, and visual infection were the quality attributes evaluated. The application of the film reduced CO₂ production and increased ethylene emission, regardless of the maturity stage of the figs. Firmness for uncoated figs underwent a significant decrease during storage, exhibiting values lower than 1.0 N. On the contrary, for coated figs, firmness was not only maintained but also even increased up to 3 N, for figs of stage III, and up to 2.5 N for the more mature figs (stage IV). Furthermore, coated figs exhibited better external color retention (ΔE < 2), lower weight loss (～8 %), and also lower visual fungal contamination (<5 %) than uncoated fruits during the 15 days of storage at 6 °C, regardless the maturity stage. Therefore, the results indicate that application of an A–Ch BE film not only can improve the overall quality of figs (F. carica var. Mission) stored at 6 °C but is also able to extend their shelf life.     

Equilibrium modified atmosphere packaging of wild strawberries

Wild strawberries (Fragaria vesca L.) are high‐added‐value fruits but their marketing is complex owing to their short postharvest life. In this work, equilibrium modified atmosphere packaging (EMAP) technology was used to maintain their quality and consequently to extend their life. Fresh strawberries were packaged with two continuous and three microperforated films (with different gas permeabilities) with the purpose of obtaining equilibrium atmospheres of diverse compositions. Weight loss, pH and acidity, solid content, colour, firmness, fungal decay and development of off‐flavours were selected to monitor fruit quality during 6 days at 10 °C. Among the five packages tested, microperforated films with one and three perforations provided adequate CO₂ and O₂ equilibrium concentrations in view of the evolution of chemical and physical quality parameters. These results were confirmed by sensory analysis. Copyright © 2007 Society of Chemical Industry     

Heat Treatment at 38 °C and 75–80 % Relative Humidity Ameliorates Storability of Cactus Pear Fruit (Opuntia ficus-indica cv “Gialla”)

Cactus pear fruit cv. Gialla were exposed to 38 °C and 75–80 (low relative humidity (LRH)) or 100 % relative humidity (saturated relative humidity (SRH)) for 36 h to evaluate their effect on decay incidence, peel disorders, and overall quality during 4 weeks’ storage at 5 °C plus 1 week at 20 °C or 5 weeks at 20 °C. Both treatments were equally effective in reducing peel disorders in cold-stored fruit, whereas decay incidence was significantly lower in fruit exposed to LRH than to SRH. The better LRH decay control was attributed to faster desiccation and fall-off the cladode piece left at harvest on the stem, which is a major onset site of infection. Both treatments reduced weight loss, had only a transient effect on respiration activity, ethylene production rate, and did not affect chemical composition, eating quality, or visual appearance of fruit.     

Extending shelf-life of persimmon (<Emphasis Type="Italic">Diospyros kaki</Emphasis> L.) fruit by hot air treatment

‘Qiandaowuhe’ persimmon fruits (Diospyros kaki L.) were stored at 20 °C after exposed to 20 °C (control), 44 °C (T ₄₄), 48 °C (T ₄₈) or 52 °C (T ₅₂) hot air for 3 h, respectively. Firmness, weight loss, peel color, total carotenoids content, soluble solids content (SSC), titratable acidity (TA), respiration, and ethylene production and cell wall hydrolysis enzymes activities were monitored to determine the efficacy of hot air treatment in delaying persimmon fruit ripening. Results showed that ‘Qiandaowuhe’ persimmon fruit displayed a typical climacteric pattern of respiration and ethylene production. Peak of CO₂ and ethylene production was observed after 4 days. Fruit softening was accompanied by a progressive increase in weight loss, total carotenoids content and decrease in h°. The activities of pectinmethylesterase (PME) and polygalacturonase (PG) sharply increased and reached maximal values after 4 and 6 days, respectively. Hot air treatment significantly delayed the onset of climacteric ethylene production, respiration, PME and PG activities in persimmon fruit. Moreover, it also significantly retarded the increase in carotenoids content and SSC, while decreased the firmness, h°, and TA. The hot air treatment promoted fruit weight loss. The shelf-life of persimmon ripening increased 4 days by T ₄₄, and 6 days by T ₄₈ or T ₅₂. Results suggest that hot air treatments can greatly extend the postharvest life of ‘Qiandaowuhe’ persimmon fruit.     

Effect of Chilling Exposure of Tomatoes During Subsequent Ripening

Mature green tomatoes were stored at 4°C, ≥ 90% RH, for up to 39 days and transferred to 21°C, ≥ 90% RH, for further ripening. After 15 days of chilling exposure, stimulation of C₂H₂ production and increased susceptibility to decay were observed when the fruit was ripened at ambient temperatures. As chilling exposure increased, C₂H₄, production upon removal to 21°C returned to the level of the control. Irreversible inhibition of color development was observed in fruit exposed to 4°C for 34 days and an increase in CO₂ production was noted upon warming of tomatoes chilled for 39 days.     

Development and Evaluation of a Film and Edible Coating Obtained from the <Emphasis Type="Italic">Cajanus cajan</Emphasis> Seed Applied to Fresh Strawberry Fruit

The aim of this work was to develop and evaluate the effect of an edible coating produced with protein isolate and gum from the Cajanus cajan seed to be applied to strawberries (Fragaria spp.). The films were formulated using 1 and 2% gum, and 5 and 10% protein isolate, as well as glycerol (2%) as a plasticizer. The formulated films were evaluated in terms of water vapor permeability (WVP), opacity, color, scanning electron microscopy, and texture. Once the ideal formulation with sufficiently low WVP and opacity was selected, it was applied to the strawberries, which were evaluated in terms of mass loss, color, firmness, acidity, pH, soluble solids, anthocyanin content, vitamin C content, and acceptability degree by an untrained consumer panel. Results showed that film made from 5% of protein isolate and 1% of gum had the lowest WVP of all treatments. Applied to strawberries, the coating resulted in a reduction of the total soluble solid content, the consumption of citric acid, and the mass loss of coated with respect to uncoated strawberries after 10 days of storage at 5 °C, without causing sensorial changes.     

Role of calcium content in antibacterial activity of donkeys’ milk toward E. coli

The objective of this study was to investigate the effect of calcium content in raw donkeys’ milk (DM) on its antibacterial activity against Escherichia coli. Antibacterial assay was performed in artificially contaminated milk samples (without and with added CaCl₂ and EDTA) incubated at 38 °C (donkeys’ body temperature). The EDTA was added to DM to bind its calcium ions, while CaCl₂ was used as the donor of calcium ions. The content of calcium, lysozyme (LYZ) and lactoferrin (LF) as well as pH value were determined in all of the tested milk samples. DM samples showed varying degrees of antibacterial activity against the tested E. coli strains. The milk samples with higher calcium content possessed stronger antibacterial potential toward the tested bacteria. The determinated calcium-dependant antibacterial activity of DM was proved thorough addition of CaCl₂ and EDTA to DM. Calcium content in tested samples was in the range from 377.1 to 1,231 mg/l. The LYZ and LF in tested DM were present at concentrations between 0.98–3.74 g/l and 2.2–54.3 mg/l, respectively. LF was not detected in five of the tested samples, and pH values of the samples were in range from 7.11 to 7.25.     

POSTHARVEST CHANGES IN STRAWBERRY FRUIT STORED UNDER SIMULATED RETAIL DISPLAY CONDITIONS1

‘Cardinal’ strawberry fruit were placed in plastic boxes with plastic dome lids (PDL) or with polyethylene wrap (PE), warmed to 25C for 8 h and stored at 1C or 5C to simulate retail storage temperature conditions. For all treatments, fruit held at 5C decayed and deteriorated more than fruit held at 1C. During storage at 1C or 5C, fruit in boxes with PE accumulated CO₂ (0.75–2 % CO₂/mg), had less weight loss and better color retention than fruit in boxes with PDL. After 3 days of storage, precooled strawberries exposed to 8 h of warming had more weight loss and worse appearance than fruit held continuously at 1C; these differences were not apparent after 7 days.