Postharvest Quality of Strawberry Fruit (Fragaria x Ananassa Duch cv. Albion) as Affected by Ozone Washing: Fungal Spoilage, Mechanical Properties, and Structure

Strawberries treated with biodegradable film containing plant extracts

Strawberry (Fragaria x ananassa Duch.) is a highly perishable fruit whose characteristics make it susceptible to developing microorganisms. Plant extracts have been studied as an alternative to pesticides to control spoilage microorganisms, responding to the expectation of the population seeking a healthier way of life. The fungus Botrytis cinerea is a facultative pathogen of vegetables, which can affect all stages of the development of several fruits, such as the strawberry, where it causes gray rot. Trichilia catigua (catuaba), Paullinia cupana (guarana), Stryphnodendron barbatiman (barbatimão), and Caesalpinia peltophoroides (sibipiruna) are planted in the Brazilian flora and have demonstrated pharmacological properties in their extracts. This work aimed to treat strawberries with a biodegradable film containing extracts of these species to evaluate strawberry conservation. There were notable distinctions in mass loss between the extract-treated and control samples. The pH, total acidity (TA), and soluble solids parameters exhibited consistently significant means across both sets of samples. Luminosity increased over the course of days in the color parameters, with the exception of strawberries coated with guarana. The red color showed greater intensity, except for those coated with barbatimão extract. Considering the results, it is possible to conclude that the coatings used can become an alternative to enhance the conservation of strawberries.

Effect of Gaseous Ozone and Storage Time on Polyphenolic Profile and Sugar Content in Fruits of Selected Vaccinium corymbosum L. Genotypes

One of the best sources of antioxidant and health-promoting bioactive substances is the fruit of V. corymbosum. A potent oxidizing agent, ozone (O3), can effectively eliminate bacteria. The application of ozone gas to V. corymbosum fruit during storage had a favorable impact on the fruit's phenolic component and sugar content in the current investigation. After 7 days of storage, phenolic content in all highbush blueberry cultivars and clones tested increased on average by 28.60%, including anthocyanins by 34%. After 14 days of storage, an average increase of 16.50% in phenolic compounds was observed, including a 20.53% increase in anthocyanins. Among all the tested varieties, clone BOR-21 treated with a dose of 0.01 mL·L-1 ozone for 30 min after 14 days had the highest TPC-143.73 mg·100 g-1 f.w. The sugar content of berries treated with a dose of 0.01 mL·L-1 ozone for 30 min, on day 7 and day 14 of storage increased by 9.2% and 6.3%, respectively. On day 7, the highest amount of total sugar (22.74 g·100 g-1) was observed in Duke cultivar after being exposed to 0.01 mL·L-1 ozone for 15 min. The ozonation treatments enhanced the fruit's saturation with nutrients, which raises the fruit's value as food.

Effect of cell size distribution on mechanical properties of strawberry fruit tissue

Strawberry fruit are high value, but also perishable products, because of their soft texture. Better insight on the strawberry mechanics are requested for understanding postharvest decay due to bruising. To gain data on the volumetric cell size distribution of strawberry tissue capturing the volume of 10 * 5 * 5 mm, fruit cells were suspended in 0.3 M mannitol solution. Cell size of 'Flair', 'Malwina', and 'Sonata' strawberry fruit, each in three commercially marketed ripeness stages (N = 135), was measured with particle size analyzer based on laser light scattering density analysis (LSD). The strawberry cell size distribution showed a wide range from 30-500 µm with frequency peak between 200 and 240 µm. The cell size of 'Flair' and 'Malwina' was smaller compared to 'Sonata' strawberry fruit. The volumetric cell size distribution obtained by LSD was correlated to microscopy results (R² = 0.97-0.99) obtained on single cells (N = 1215), indicating that LSD can be used for measuring the percentages of different cell size ranges of volumetric fruit sample. The three ripeness stages were classified with Gaussian Naïve Bayes approach considering absorption coefficient of anthocyanins at 405 nm (GNBa) and percentage frequency of peak cell size (GNBc). For GNBa classes, ripening stage showed no interaction with failure stress, strain, and elastic modulus. Considering GNBc classes, the failure stress and elastic modulus of strawberry tissue increased with enhanced percentage frequency of peak cell size for all three cultivars. An enhanced percentage frequency of large cells resulted in increased susceptibility of the strawberry tissue. Overall, this study showed that LSD cell size distribution data from a volumetric tissue sample are related to fruit tissue mechanics, which is conducive to a better analysis of the actual stress and damage problems of strawberry fruit tissue specimens during compression in supply chain processes.

Effect of Calcium Foliar Spray Technique on Mechanical Properties of Strawberries

The calcium fertilization of strawberry plants (Fragaria × ananassa Duchesne) was evaluated using two types of nozzles, with two liquid pressure levels and two driving speeds. The calcium content of the leaves and fruit were analyzed via flame photometry. Higher leaf calcium content was found in plots sprayed with standard nozzles, while higher fruit calcium content was observed for those sprayed with air induction nozzles. The fruit quality was assessed by determining the basic physical and mechanical properties, using uniaxial compression tests integrated with surface pressure measurements. Different spraying techniques influenced the mechanical resistance of the fruit. A spraying speed of 5 km/h and an operating pressure of 0.4 MPa significantly increased the firmness of the fruit by ~66%, the critical load level by 36%, and the maximum surface pressure by up to 38%, but did not increase the geometrical parameters of the strawberries. Regular foliar feeding during harvest could improve the mechanical strength of strawberries. An appropriate spraying technique with a calcium agent could effectively improve the mechanical properties of the delicate fruit, which is particularly important for limiting losses during harvesting, transportation, and storage.

Screening of Different Essential Oils Based on Their Physicochemical and Microbiological Properties to Preserve Red Fruits and Improve Their Shelf Life

Strawberries and raspberries are susceptible to physiological and biological damage. Due to the consumer concern about using pesticides to control fruit rot, recent attention has been drawn to essential oils. Microbiological activity evaluations of different concentrations of tested EOs (cinnamon, clove, bergamot, rosemary and lemon; 10% DMSO-PBS solution was used as a diluent) against fruit rot fungal strains and a fruit-born human pathogen (Escherichia coli) indicated that the highest inhibition halos was found for pure cinnamon and clove oils; according to GC-MS analysis, these activities were due to the high level of the bioactive compounds cinnamaldehyde (54.5%) in cinnamon oil and eugenol (83%) in clove oil. Moreover, thermogravimetric evaluation showed they were thermally stable, with temperature peak of 232.0 °C for cinnamon and 200.6/234.9 °C for clove oils. Antibacterial activity evaluations of all tested EOs at concentrations from 5-50% (v/v) revealed a concentration of 10% (v/v) to be the minimum inhibitory concentration and minimum bactericidal concentration. The physicochemical analysis of fruits in an in vivo assay indicated that used filter papers doped with 10% (v/v) of cinnamon oil (stuck into the lids of plastic containers) were able to increase the total polyphenols and antioxidant activity in strawberries after four days, with it being easier to preserve strawberries than raspberries.

Effect of Ozone Treatment on Mechanical and Chemical Properties of Sea-Buckthorn (Hippophaë rhamnoides L.) Fruit

During storage, sea-buckthorn berries which are a valuable source of bioactive compounds, gradually lose their optimum mechanical properties and chemical characteristics. Mechanical and chemical properties of sea-buckthorn berries were examined in fruit exposed to gaseous ozone at a rate of 10 and 50 ppm for 15 minutes. Ozonation process did not impact mechanical properties (except for elastic modulus) or morphological characteristics, but it resulted in decreased water loss, on average by 5.21%, in fruit kept in cold storage for 14 days, as well as increased pH and reduced acidity of sea-buckthorn berries on average by 9.03% and 20.0% (for ozone concentration of 50 ppm) compared to the control sample. Polyphenol contents in sea-buckthorn berries were identified using UPLC-PDA-MS/MS. Out of all the identified polyphenols, the findings showed the highest contents of flavone glycosides, represented e.g., by isorhamnetin-3-O-rutinoside. The contents of bioactive compounds (ascorbic acid, total polyphenols or polyphenol profile) as well as antioxidant activity (measured using DPPH. and ABTS+. assays) were different, depending on the variety and possibly were affected by the timing of sea-buckthorn fruit harvest.

Effect of Ozonation on the Mechanical, Chemical, and Microbiological Properties of Organically Grown Red Currant (Ribes rubrum L.) Fruit

Red currant fruits are a valuable source of micro- and macronutrients, vitamins, and chemical compounds with health-promoting properties, the properties of which change depending on the harvest date and the time and method of storage. This study analysed the effect of applying 10 ppm ozone gas for 15 and 30 min on the mechanical properties, chemical properties and microbiological stability of three organic-grown red currant fruit cultivars. Fruits harvested at the time of harvest maturity had significantly larger diameters and weights and lower water contents compared with fruits harvested seven days earlier, and the ozonation process, regardless of its harvesting date, reduced the physical parameters in question (diameter, weight, and water content). The ascorbic acid content of the ozonated fruit varied, with the highest decreases observed for fruit harvested 7 days before the optimal harvest date and stored for 15 days under refrigeration (an average decrease of 13.31% compared with the control fruit without ozonation). In general, the ozonation process had a positive effect on the variation of fruit antioxidant activity, with the highest average values obtained for fruit harvested 7 days before the optimum harvest date and stored for 15 days under refrigeration conditions; in addition, it also had an effect on reducing the development of microorganisms, including mesophilic aerobic bacteria, yeasts, and moulds, mainly for the cultivar 'Losan'.

Quality characteristics of strawberry fruit following a combined treatment of laser sterilization and guava leaf-based chitosan nanoparticle coating

Background

Strawberry fruit is a rich source of antioxidants that are beneficial for human health. However, the rapid decline of strawberries dramatically reduces the shelf life and raises postharvest losses. To develop an efficient and ecological approach for maintaining the quality, strawberries (Fragaria x ananassa, cv. Festival) were treated with 0.5% chitosan coating (0.5% Ch), guava leaf-based chitosan nanoparticles coating (Gl-ChNps), and a combination treatment of 1.3 mW/cm2 laser light followed by Gl-ChNps coating (combined treatment), then stored for 12 days at 10 °C and 85–90% RH. The untreated fruit served as a control.

Results

Semi-spherical particles with an average size of 21.92 nm, a monodisperse nature, and high solution stability were formed. The findings revealed that the combined treatment completely suppressed fungal decay compared to 50% decay in control, and significantly reduced weight loss percentage to 4.68% compared to 27.35% in control. In accordance, the combined treatment had the maximum anthocyanin content and vitamin C, at 42 and 81.1 mg/100 g, respectively. The results showed that treated strawberries had less change in color, total soluble solids, titratable acidity, and pH during storage than untreated strawberries, which exhibited higher chemical changes.

Conclusions

The edible film of chitosan nanoparticles acted as a semi-permeable barrier that modified and restricted gas exchange, reduced water loss, and delayed fruit senescence. In addition, the combination of laser light with chitosan nanoparticles has been shown to control the pathogens and retain the freshness of strawberries.

Graphical Abstract

Preliminary Studies on Endotherapy Based Application of Ozonated Water to Bobal Grapevines: Effect on Wine Quality

The application of ozonated water in the vineyard is an increasingly popular tool for disease management, but the quality of grapes and resulting wines is likely to be affected. Endotherapy, or trunk injection, is a particularly useful method to apply phytosanitary products since many fungal pathogens colonize the grapevine woody tissues. Thus, the present study aimed to evaluate the effect on wine quality of the ozonated water applied to Bobal grapevines, one of the most cultivated red varieties in Spain, through endotherapy (E) or its combination with spraying (E + S). Endotherapy was carried out four times before harvest for both E and E + S treatments, and spraying was performed 2 days before and after each endotherapy application. Grapes were harvested, vinified, and the quality of the finished wines was evaluated through several enological parameters and the phenolic and volatile composition. Both treatments resulted in less alcoholic and more acidic wines. The E treatment, although it reduced the content of phenolic acids, stilbenes and flavanols, significantly increased anthocyanins, whereas E + S decreased the overall amount of phenolics, which had different implications for wine colour. In terms of aroma, both treatments, but E to a greater extent, reduced the content of glycosylated precursors and differentially affected free volatiles, both varietal and fermentative. Thus, the dose of ozonated water, frequency and/or method of application are determining factors in the effect of these treatments on wine quality and must be carefully considered by winegrowers to establish the optimum treatment conditions so as not to impair the quality of wines.

Chitosan encompassed Aniba rosaeodora essential oil as innovative green candidate for antifungal and antiaflatoxigenic activity in millets with emphasis on cellular and its mode of action

The present study demonstrates first time investigation on encapsulation of Aniba rosaeodora essential oil into chitosan nanoemulsion (AREO-CsNe) with the aim of improvement of its antifungal, and aflatoxin B₁ (AFB₁) inhibitory performance in real food system. The GC–MS analysis of AREO revealed the presence of linalool (81.46%) as a major component. The successful encapsulation of EO into CsNe was confirmed through SEM, FTIR, and XRD analysis. The in-vitro release study showed the controlled release of AREO. AREO-CsNe caused complete inhibition of Aspergillus flavus (AFLHPSi-1) growth and AFB₁ production at 0.8 and 0.6 μl/ml, respectively, which was far better than AREO (1.4 and 1.2 μl/ml, respectively). Impairment of ergosterol biosynthesis coupled with enhancement of cellular materials leakage confirmed plasma membrane as the possible antifungal target of both AREO and AREO-CsNe. Significant inhibition of methylglyoxal (AFB₁ inducer) synthesis in AFLHPSi-1 cells by AREO and AREO-CsNe confirmed their novel antiaflatoxigenic mode of action. In-silico molecular docking studies revealed effective interaction of linalool with Ver-1 and Omt-A proteins, leading to inhibition of AFB₁ biosynthesis. Further, AREO-CsNe showed enhanced antioxidant activity with IC₅₀ values 3.792 and 1.706 μl/ml against DPPH^• and ABTS^•+ radicals, respectively. In addition, AREO-CsNe caused 100% protection of stored millets (Setaria italica seeds) from AFB₁ contamination and lipid peroxidation over a period of 1 year without compromising its sensory properties and exhibited high safety profile with LD₅₀ value 9538.742 μl/kg body weight. Based on enhanced performance of AREO-CsNe over AREO, it can be recommended as a novel substitute of synthetic preservative for preservation of stored millets.

The Effect of the Addition of Ozonated and Non-Ozonated Fruits of the Saskatoon Berry (Amelanchier alnifolia Nutt.) on the Quality and Pro-Healthy Profile of Craft Wheat Beers

Research into the suitability of domestic raw materials, including, for example, new wheat cultivars and fruit additives for the production of flavoured beers, is increasingly being undertaken by minibreweries and craft breweries. The fruits of the Saskatoon berry are an important source of bioactive compounds, mainly polyphenols, but also macro- and microelements. The fruits of two Canadian cultivars of this species, 'Honeywood' and 'Thiessen', were used in this study. Physicochemical analysis showed that wheat beers with the addition of non-ozonated fruit were characterised by a higher ethanol content by 7.73% on average. On the other hand, enrichment of the beer product with fruit pulp obtained from the cv. 'Thiessen' had a positive effect on the degree of real attenuation and the polyphenol profile. Sensory evaluation of the beer product showed that wheat beers with the addition of 'Honeywood' fruit were characterised by the most balanced taste and aroma. On the basis of the conducted research, it can be concluded that fruits of both cvs. 'Honeywood' and 'Thiessen' can be used in the production of wheat beers, but the fermentation process has to be modified in order to obtain a higher yield of the fruit beer product.

Ozone Treatment Improves the Texture of Strawberry Fruit during Storage

The major aim of this study was to check whether a cyclic ozonation process will affect the preservation of the texture of strawberries stored at room temperature. Strawberry fruit was stored for 3 days at room temperature and ozonated with gaseous ozone at a concentration of 10 and 100 ppm for 30 min, every 12 h of storage. Research showed that the ozonation process inhibited the texture deterioration of the fruit during storage. The positive effect of ozone was directly related to the inhibition of the activity of enzymes involved in the degradation of the fruit cell walls, as well as indirectly from the improved energy metabolism of the fruit. The higher level of energy charge corresponded to the higher resistance of ozonated fruit to abiotic stress, leading to the maintenance of the integrity of cell membranes and, consequently, to maintaining good hardness of the fruit throughout the storage period.

Effect of Ozone-Treated or Untreated Saskatoon Fruits (Amelanchier alnifolia Nutt.) Applied as an Additive on the Quality and Antioxidant Activity of Fruit Beers

Fruit of Saskatoon (Amelanchier alnifolia Nutt.) are a good source of bioactive compounds, such as polyphenols, including anthocyanins, as well as vitamins, macro- and microelements and fibre. By treating Saskatoon fruits with gaseous ozone, and adding the material as an enhancer to barley beers, it is possible to impact the contents of bioactive compounds in the produced fruit beers. Sensory tests showed that beers made from barley with addition of Saskatoon fruit of the ‘Smoky’ cultivar were characterised by the most balanced taste and aroma. Physicochemical analyses of fruit beers, produced with Saskatoon fruit pulp added on the seventh day of fermentation, showed that the beers enhanced with ozone-treated and untreated ‘Smoky’ Saskatoon fruits had the highest contents of alcohol, 5.51% v/v and 5.66% v/v, respectively, as well as total polyphenol contents of 395 mg GAE/L and 401 mg GAE/L, respectively, and higher antioxidant activity (assessed using DPPH^•, FRAP and ABTS^+• assays). It was demonstrated that the ozonation process led to a decrease in the contents of neochlorogenic acid, on average by 91.00%, and of caffeic acid by 20.62%, relative to the beers enhanced with ‘Smoky’ Saskatoon fruits not subjected to ozone treatment. The present study shows that Saskatoon fruits can be used in the production of beer, and the Canadian cultivar ‘Smoky’ is recommended for this purpose.

Effects of Ozone Fumigation on the Main Postharvest Pathogenic Fungi Penicillium sp. and the Storage Quality of Blueberry in Majiang County, China

In this study, the fungus Penicillium sp. was isolated from rotting postharvest blueberry fruits at different storage stages and identified into genera. Inoculation of this strain on the surface of fresh fruits was able to cause rotting. The strain was then used as a reference strain to test the chemical control effect of ozone fumigation during storage. The results showed that ozone fumigation had an obvious inhibitory effect on Penicillium sp. in a dose- and time-dependent manner. Meanwhile, ozone fumigation treatment could prevent the loss of fruit firmness, slow down the decrease of soluble solids, total phenolics, and anthocyanins, and maintain a lower activity of PPO and higher activities of POD and CAT. As far as we know, this is the first report on the effects of ozone fumigation on the postharvest pathogenic fungi Penicillium sp. and on the storage quality of postharvest blueberry collected from Majiang County, Guizhou province, China.

Effects of Gaseous Ozone on Microbiological Quality of Andean Blackberries (Rubus glaucus Benth)

Andean blackberries are highly perishable due to their susceptibility to water loss, softening, mechanical injuries, and postharvest diseases. In this study, the antimicrobial efficacy of gaseous ozone against spoilage (mesophiles, psychrotrophs, and yeasts and molds) and pathogenic (E. coli, S. enterica, and B. cinerea) microorganisms was evaluated during 10 days of storage at 6 ± 1 °C. Respiration rate and mass loss were also determined. Ozone was applied prior to storage at 0.4, 0.5, 0.6, and 0.7 ppm, for 3 min. The best results were observed with the higher ozone dose, with initial maximum reductions of ~0.5, 1.09, and 0.46 log units for E. coli, S. enterica, and B. cinerea, respectively. For the native microflora, maximum reductions of 1.85, 1.89, and 2.24 log units were achieved on day 1 for the mesophiles, psychrotrophs, and yeasts and molds, respectively, and this effect was maintained throughout storage. In addition, the lower respiration rate and mass loss of the blackberries ozonated at 0.7 ppm indicate that this treatment did not induce physiological damage to the fruit. Gaseous O₃ could be effective in maintaining the postharvest quality of blackberries throughout refrigerated storage but higher doses could be advisable to enhance its antimicrobial activity.

Developing an LED preservation technology to minimize strawberry quality deterioration during distribution

This study investigated the effect of LED illumination on the inactivation of Rhizopus stolonifer and Botrytis cinerea on strawberries and physicochemical properties of the strawberries. Twelve days of illumination resulted in an antifungal effect of 3.4 and 1.9 log CFU/g on R. stolonifer and B. cinerea respectively. The illumination caused no significant effect (P ≥ 0.05) on the mass, color and texture of strawberries. Furthermore, total phenolic content, trolox equivalent antioxidant capacity and anthocyanin content of the illuminated strawberries significantly increased (P < 0.05). Vitamin C content of illuminated strawberries was only significantly different (P < 0.05) from the control starting from Day 9. These results show that 405 nm LED illumination can potentially complement temperature and humidity control in preventing mold spoilage and preserving physicochemical quality of strawberries during refrigerated storage.

Effect of Ozone Treatment on the Quality of Sea Buckthorn (Hippophae rhamnoides L.)

The aim of this research was to show the effect of the ozonation process on the quality of sea buckthorn (Hippophae rhamnoides L.). The quality of the ozonated berries of sea buckthorn was assessed. Prior to and after the ozone treatment, a number of parameters, including the mechanical properties, moisture content, microbial load, content of bioactive compounds, and composition of volatile compounds, were determined. The influence of the ozonation process on the composition of volatile compounds and mechanical properties was demonstrated. The ozonation had negligible impact on the weight and moisture of the samples immediately following the treatment. Significant differences in water content were recorded after 7 days of storage. It was shown that the highest dose of ozone (concentration and process time) amounting to 100 ppm for 30 min significantly reduced the water loss. The microbiological analyses showed the effect of ozone on the total count of aerobic bacteria, yeast, and mold. The applied process conditions resulted in the reduction of the number of aerobic bacteria colonies by 3 log cfu g-1 compared to the control (non-ozonated) sample, whereas the number of yeast and mold colonies decreased by 1 log cfu g-1 after the application of 100 ppm ozone gas for 30 min. As a consequence, ozone treatment enhanced the plant quality and extended plant's storage life.

Transcriptome Analysis of the Fruit of Two Strawberry Cultivars "Sunnyberry" and "Kingsberry" That Show Different Susceptibility to Botrytis cinerea after Harvest

Gray mold (Botrytis cinerea) is a fungal plant pathogen causing postharvest decay in strawberry fruit. Here, we conducted a comparative transcriptome analysis to identify differences in gene expression between the immature-green (IG) and mature-red (MR) stages of the “Sunnyberry” (gray mold-resistant) and “Kingsberry” (gray mold susceptible) strawberry cultivars. Most of the genes involved in lignin and alkane-type wax biosynthesis were relatively upregulated in “Sunnyberry”. However, pathogenesis-related proteins encoding R- and antioxidant-related genes were comparatively upregulated in “Kingsberry”. Analysis of gene expression and physiological traits in the presence and absence of B. cinerea inoculation revealed that the defense response patterns significantly differed between IG and MR rather than the cultivars. “Kingsberry” showed higher antioxidant induction at IG and upregulated hemicellulose-strengthening and R genes at MR. Hence, “Sunnyberry” and “Kingsberry” differed mainly in terms of the expression levels of the genes forming cuticle, wax, and lignin and controlling the defense responses. These discrepancies might explain the relative difference between these strawberry cultivars in terms of their postharvest responses to B. cinerea.

Effect of Ozonation Process on the Energy Metabolism in Raspberry Fruit During Storage at Room Temperature

The major aim of this research was to investigate the effect of ozone treatment on the energy metabolism in raspberry fruit during storage at room temperature. Raspberries were ozonated with an ozone concentration of 8–10 mg L−1, for 30 min, every 12 h of storage at room temperature for 72 h. The results indicated that ozone treatment significantly enhanced the activities of mitochondrial respiratory enzymes, such as succinate dehydrogenase, cytochrome C oxidase, and H+-ATPase, which contributed to maintain the high level of ATP and energy charge in fruit during storage. Moreover, the energy metabolism in mitochondria was closely correlated with the antioxidant potential of raspberry fruit. This study has given an experimental evidence that ozonation procedure in proposed process conditions significantly affects the mitochondrial respiratory system leading to maintain the high quality of the fruit over a long period of storage at room temperature.

Ozone washing decreases strawberry susceptibility to Botrytis cinerea while maintaining antioxidant, optical and sensory quality

This work aimed to evaluate the effect of ozone washing (maximum concentration 3.5 mgL^-1- 5 and 15 min) on Botrytis cinerea decay, physicochemical parameters, bioactive compounds, in vitro and in vivo antioxidant activity, and sensory properties of strawberries cv. Albion throughout refrigerated storage at 5 ± 1 °C. A 5 min long ozonation delayed the onset of B. cinerea infection by 4 days, and significantly reduced its incidence as storage progressed (~17 % lesser than in control at day 8), without impairing physicochemical parameters or sensory quality. This treatment did not affect the antioxidant activity of strawberry extracts neither in in vitro (ORAC and ABTS assays) or in vivo assays using Caenorhabditis elegans as a model organism. Higher ozone doses did not achieve greater reduction of B. cinerea decay throughout the storage period. This study demonstrated that exposing strawberries to a 5 min long aqueous ozone treatment could extend their storability at 5 °C.

Validation of a vapor-phase advanced oxidation process for inactivating Listeria monocytogenes, its surrogate Lactobacillus fructivorans, and spoilage molds associated with green or red table grapes

A method based on vapor-phase advanced oxidation process (AOP) for decontaminating red or green grapes was validated for inactivating Listeria monocytogenes and spoilage molds. A Central Composite Design (CCD) and Response Surface Methodology (RSM) were applied to determine the contribution of UV-C (254 nm) dose, hydrogen peroxide, and ozone concentration on the lethality toward Aspergillus niger spores (biodensiometer) and changes to the grape quality (firmness and color over 14-day post-treatment storage at 4 °C). A high UV-C dose (>129 mJ/cm² ) or >4.0 % v/v hydrogen peroxide induced-blistering and darkening of grapes at the end of the storage period. Yet, an optimized AOP treatment (with regards to preserving grape quality) was derived to be 1.3% v/v hydrogen peroxide (5 mL/10 berries) with 9-mg ozone gas and a UV-C dose of 123 mJ/cm² (10 s at UV-C intensity of 12 mW/cm² ). A predictive model was constructed and verified based on the log reduction of A. niger spores and changes in quality characteristics of red grapes. The optimal AOP treatment supported a 1.6-log CFU/g reduction of Aspergillus spores and decreased L. monocytogenes counts by 3.92 ± 0.17 and 4.77 ± 0.30 log CFU/g on green and red grapes, respectively, that were not significantly different to the surrogate, Lactobacillus fructivorans. There was no significant difference in the reduction of L. monocytogenes with grapes arranged in a single or double layer. Botrytis cinerea counts were reduced by 1.08 to 1.35 log CFU/g using the optimized AOP treatment with no change in grape color or firmness during storage. A sensory panel could not differentiate AOP-treated grapes from nontreated controls although 3 of 15 panelists did note subtle flavor notes. PRACTICAL APPLICATION: Postharvest washing of fresh produce has limited efficacy in removing foodborne pathogens and spoilage microbes. This is especially relevant to berries, such as grapes, that are susceptible to spoilage following washing. The vapor-phase AOP treatment provides a supplemental or alternative approach for produce decontamination. However, the operating parameters need to be optimized to ensure that decontamination of grapes is not at the expense of quality. In the current study, this was achieved by ensuring a balance between hydrogen peroxide, ozone, and UV-C dose that form the elements of an AOP treatment.

Ozone Treatment Induces Changes in Antioxidative Defense System in Blueberry Fruit During Storage

The major aim of this study was to investigate the effect of ozonation process on the level of oxidative stress markers in blueberry fruit during cold storage (4 °C). Blueberry (Vaccinum corymbosum L.) fruit was ozonated with an ozone concentration of 15 ppm for 30 min, every 12 h for 28 days of storage at 4 °C. The results indicated that ozone treatment activated a defense mechanism against oxidative stress in blueberry fruit. Ozonated fruit was characterized by higher activity of antioxidant enzymes i.e. superoxide dismutase, glutathione peroxidase, and phenylalanine ammonia-lyase than non-ozonated fruit, over the first 21 days of storage. In turn, the level of superoxide anion radical and hydrogen peroxide in ozonated fruit was significantly lower compared with the untreated material. However, after 21 days of storage, ozone treatment contributed to the oxidative modification of protein which could be a reason of decreasing enzymes activity, involved in cell protection against oxidative stress.

Effects of ozone concentration on the postharvest quality and microbial diversity of Muscat Hamburg grapes

Grapevines are widely planted around the world. Although grapes have high nutritional value, they are highly perishable. To explore the effect of ozone concentration on the postharvest quality of Muscat Hamburg grapes, the ethylene production rate, respiratory intensity, soluble solids, titratable acidity, firmness, threshing rate, total yeast and mold counts, and the activities of superoxide dismutase, peroxidase, catalase, polyphenol oxidase and phenylalanine ammonia lyase were determined, and the fungal metagenome on the grape surface was analyzed. Among the ozone treatment groups, 14.98 mg m-3 ozone showed a positive effect on grape preservation. After 80 days of storage, the contents of soluble solids and titratable acidity increased by 3.1% and 0.03%, respectively, compared with the control group. Over the same period, firmness increased by 4.22 N and the threshing rate decreased by 0.5%. During storage, the activity of polyphenol oxidase was inhibited and the activities of superoxide dismutase, peroxidase, catalase, and phenylalanine ammonia lyase were maintained, which delayed the senescence of grapes and maintained freshness. Ozone can reduce the number of fungi on the grape surface, change the colony structure, and reduce the occurrence of diseases. An ozone concentration of 14.98 mg m-3 can delay the senescence of Muscat Hamburg grapes and improve storage quality.

Effect of Ozone Treatment on Flavonoid Accumulation of Satsuma Mandarin (Citrus unshiu Marc.) during Ambient Storage

This study aimed to compare the flavonoid accumulation between ozone-treated and untreated Satsuma mandarin (Citrusunshiu Marc.) fruits. The fruits exposed to gaseous ozone were found to have higher antioxidant activities and content of flavonoid during the storage period by ultra-high performance liquid chromatography (UPLC). To reveal the molecular regulation of flavonoid accumulation by ozone, chalcone synthase (CHS), chalcone isomerase (CHI), β-1,3-glucanase (GLU), chitinase (CHT), phenylalanine ammonia-lyase (PAL), and peroxidase (POD) were identified and their expression was examined by quantitative real-time polymerase chain reaction (q-PCR). These results support the promising application of ozone treatment as a safe food preservation technique for controlling postharvest disease and extending shelf-life of harvested Satsuma mandarin.

Synergistic effects of ascorbic acid and plant-derived ceramide to enhance storability and boost antioxidant systems of postharvest strawberries

BACKGROUND

Excessive reactive oxygen species (ROS) may attack biological macromolecules and induce oxidative stress. The inhibition by ascorbic acid (AsA) on oxidative damage has been reported in fruits, while the barrier effect of ceramide has also been proven. However, there are few reports about the effects of ceramide-AsA interactions to enhance storability and boost antioxidant systems in fruits during storage. This study was conducted to study the synergistic effects of AsA in combination with ceramide on the quality of postharvest strawberry (Fragaria anannasa cv. Tianbao).

RESULTS

Treatment with 100 mg L^-1 AsA plus 1.2 mmol L^-1 ceramide significantly delayed the rot of strawberries, reduced the water loss and the contents of ROS, malonaldehyde (MDA), and proline, however, increased the contents of total flavonoids, total phenols, and anthocyanins compared with other treatments. Also, treatment with 100 mg L^-1 AsA plus 1.2 mmol L^-1 ceramide significantly increased the activities of peroxidase (POD) and superoxide dismutase (SOD) but inhibited the activity of polyphenol oxidase (PPO).

CONCLUSION

It is suggested that treatment with 100 mg L^-1 AsA plus 1.2 mmol L^-1 ceramide could significantly reduce the oxidative damage and maintain the storage quality of strawberries during storage by enhancing the antioxidant systems. © 2019 Society of Chemical Industry.