Precooling and ozone treatments affects postharvest quality of black mulberry (Morus nigra) fruits

Influence of different pre-cooling methods on the freshness preservation of bok choi(Brassica rapa var. chinensis)

Several pre-cooling methods for bok choi were used, such as natural convection pre-cooling (NCPC), strong wind pre-cooling (SWPC), vacuum pre-cooling (VPC), cold water pre-cooling (CWPC), electrolyzed water pre-cooling (EWPC), and fluid ice pre-cooling (FIPC), in order to determine the most suitable precooling method. It was found that VPC reduced the respiration rate, inhibited the increase of malondialdehyde (MDA) and relative electrolyte leakage, and significantly decreased the total bacterial count. This may be due to the rapid decompression process during vacuum pre-cooling, which disrupts the microbial structure and has a certain sterilizing effect. Bok choi pre-cooled by VPC had the best color, hardness value, chlorophyll, titratable acid (TA) content, vitamin C (VC) content, total phenolic (TP) content, soluble sugar content, superoxide dismutase (SOD) activity, ascorbate peroxidase (APX) activity, and catalase (CAT) activity. Therefore, the most suitable pre-cooling method for bok choi among the above pre-cooling methods was the VPC method.

The impact of ozone and equilibrium-modified atmosphere packaging on storage stability and health-promoting indicators of fresh "Angelino" plums

Effectiveness of ozone concentrations (2, 5, and 10 ppm) and exposure time (3 and 9 min) on selected physicochemical properties (pH, soluble solids, color values (L*, a*, and b*), and texture) and health-promoting indicators such as organic acids, total phenolics (TP), and anthocyanins of "Angelino" fresh plums was evaluated during storage (0, 30, 90, and 120 days) in equilibrium modified atmosphere packaging (EMAP). Total anthocyanin contents and organic acid profiles were significantly affected by storage times. Malic acid (MA) was the main organic acid in "Angelino" plums. MA content (4663 and 4764 mg/L) was the highest value in the ozonated 2-ppm/9-min and 5-ppm/3-min than other ozonated groups and also control at 120 days of the storage. The ozone treatments especially 2-ppm/9-min and 5-ppm/3 min can significantly retard the degradation of MA content (8294 to 2688-2694 mg/L) during the storage (p < .05). Total phenol content were most significantly decreased in the control during storage, with the loss at the level of 31.7% of TPs, while the lowest one 2-ppm/9-min (20.8%) and 5-ppm/-3 min (21.9%). The color and texture are maintained for the ozone applications compared to the control during storage. Ozonation with 2-ppm/9-min and 5-ppm/-3 min showed the best performance while maintaining the storage stability based on the physicochemical properties including hardness and bioactive compounds (such as anthocyanins and organic acids), visual appearance due to the more attractive color (L*, a*, b*) the plums.

Sponge-like porous polyvinyl alcohol/chitosan-based hydrogel with integrated cushioning, pH-indicating and antibacterial functions

Developing a packaging material with integrated cushioning, intelligent and active functions is highly desired but remains challenging in the food industry. Here we show that a sponge-like porous hydrogel with pH-indicating and antibacterial additives can meet this requirement. We use polyvinyl alcohol and chitosan as the primary polymers to construct a hydrogel with hierarchical structures through a freeze-casting method in combination with salting-out treatment. The synergy of aggregated polymer chains and the sponge-like porous structure makes the hydrogel resilient and efficient in energy absorption. It also enables rapid movement of molecules/particles and fast reaction due to the large specific surface area of the pore structures and the large amount of free water in it, leading to a sensitive pH-indicating function. The hydrogel shows an obvious color variation within a wide pH range in 3 min. The silver nanoparticles are fixed in the dense polymer networks, enabling a lasting release of silver ions. The porous structure makes the silver ion reach the protected item in a short time, achieving an antibacterial effect against S. aureus and E. coli with little cytotoxicity. This work paves the way for fabricating multifunctional hydrogels for diverse advanced packaging systems.

Novel 4-Chromanone-Derived Compounds as Plant Immunity Inducers against CMV Disease in Passiflora spp. (Passion Fruit)

This study involved the design and synthesis of a series of novel 4-chromanone-derived compounds. Their in vivo anti-cucumber mosaic virus (CMV) activity in field trials against CMV disease in Passiflora spp. was then assessed. Bioassay results demonstrated that compounds 7c and 7g exhibited remarkable curative effects and protection against CMV, with inhibition rates of 57.69% and 51.73% and 56.13% and 52.39%, respectively, surpassing those of dufulin and comparable to ningnanmycin. Field trials results indicated that compound 7c displayed significant efficacy against CMV disease in Passiflora spp. (passion fruit) after the third spraying at a concentration of 200 mg/L, with a relative control efficiency of 47.49%, surpassing that of dufulin and comparable to ningnanmycin. Meanwhile, nutritional quality test results revealed that compound 7c effectively enhanced the disease resistance of Passiflora spp., as evidenced by significant increases in soluble protein, soluble sugar, total phenol, and chlorophyll contents in Passiflora spp. leaves as well as improved the flavor and taste of Passiflora spp. fruits, as demonstrated by notable increases in soluble protein, soluble sugar, soluble solid, and vitamin C contents in Passiflora spp. fruits. Additionally, a transcriptome analysis revealed that compound 7c primarily targeted the abscisic acid (ABA) signaling pathway, a crucial plant hormone signal transduction pathway, thereby augmenting resistance against CMV disease in Passiflora spp. Therefore, this study demonstrates the potential application of these novel 4-chromanone-derived compounds as effective inducers of plant immunity for controlling CMV disease in Passiflora spp. in the coming decades.

Post-harvest ultraviolet irradiation induces changes in physical-chemical properties and levels of polycyclic aromatic hydrocarbons and gene expression in mulberry fruit

BACKGROUND

Earlier studies reported that post-harvest ultraviolet (UV) irradiation could increase the health-promoting compounds in fruit but the effects of UV irradiation on the reduction of the polycyclic aromatic hydrocarbon (PAH) content in mulberries remain less known. Black mulberry fruit were exposed to two UV illumination dosages (3.5 and 7 kJ m-2 ) and were stored for 4, 8, and 12 days.

RESULTS

Mulberries treated in this way displayed higher antioxidant enzyme activity and phenolic compound content in comparison with a control condition. The transcription factors (TFs) MdoMYB121, MdoMYB155, MdbZIP2, and MdbZIP48 were strongly expressed in two UV illumination dosages (about 45-95% higher than the control). The fluorine (Flu) and naphthalene (Nap) content in treated fruit decreased by 21-85% in comparison with the control condition.

CONCLUSION

The findings of this study indicate that UV irradiation can be considered as a promising technique to remove some PAHs in black mulberries, to increase their health-promoting potential, and indirectly to improve their aesthetic quality due to the resulting desirable color parameters. © 2023 Society of Chemical Industry.

Ozone micro-nano bubble water preserves the quality of postharvest parsley

The production and use of ozone micro-nano bubble water (O₃-MNBW) is an innovative technology that prolongs the reactivity of aqueous-phase ozone and maintains the freshness and quality of fruits and vegetables by removing pesticides, mycotoxins, and other contaminants. The quality of parsley treated with different concentrations of O₃-MNBW was investigated during storage at 20 ℃ for 5 d, and found that a ten-minute exposure of parsley to 2.5 mg·L^-1 O₃-MNBW effectively preserved the sensory quality of parsley, and resulted in lower weight loss, respiration rate, ethylene production, MDA levels, and a higher level of firmness, vitamin C, and chlorophyll content, relative to untreated parsley. The O₃-MNBW treatment also increased the level of total phenolics and flavonoids, enhanced peroxidase and ascorbate peroxidase activity, and inhibited polyphenol oxidase activity in stored parsley. Five volatile signatures identified using an electronic nose (W1W, sulfur-compounds; W2S, ethanol; W2W, aromatic- and organic- sulfur compounds; W5S, oxynitride; W1S, methane) exhibited a significant decrease in response to the O₃-MNBW treatment. A total of 24 major volatiles were identified. A metabolomic analysis identified 365 differentially abundant metabolites (DMs). Among them, 30 and 19 DMs were associated with characteristic volatile flavor substance metabolism in O₃-MNBW and control groups, respectively. The O₃-MNBW treatment increased the abundance of most DMs related to flavor metabolism and reduced the level of naringin and apigenin. Our results provide insight into the mechanisms that are regulated in response to the exposure of parsley to O₃-MNBW, and confirmed the potential use of O₃-MNBW as a preservation technology.

Effects of Different Pre-Cooling Methods on the Shelf Life and Quality of Sweet Corn (Zea mays L.)

The strong wind pre-cooling (SWPC), ice water pre-cooling (IWPC), vacuum pre-cooling (VPC), natural convection pre-cooling (NCPC), and slurry ice pre-cooling (SIPC) techniques were used to pre-cool the fresh sweet corn (Zea mays L.), and then the pre-cooling treated sweet corn samples were stored at 4 °C for 28 days. During refrigeration, quality indicators, such as hardness, water loss, color, soluble solids content, and soluble sugar, were determined. In addition, oxidation indicators, such as peroxidase, catalase, ascorbic acid-peroxidase activity, and carotene content, were also measured. The results showed that the main problems of sweet corn during cold storage were water loss and respiration. The pre-cooling speed of SWPC is the fastest, and the latent heat of sweet corn can be removed in only 31 min. SWPC and IWPC could reduce the loss of fruit quality, maintain good color and hardness, inhibit the decrease of water, soluble solids, soluble sugars, and carotenoid contents, maintain balance between POD, APX, and CAT, and extend the shelf life of sweet corn. The shelf life of SWPC and IWPC corn reached 28 days, 14 days longer than SIPC and VPC treated samples, and 7 days longer than NCPC treated samples. Therefore, SWPC and IWPC are the appropriate methods to pre-cool the sweet corn before cold storage.

Chitosan oligosaccharide as a plant immune inducer on the Passiflora spp. (passion fruit) CMV disease

Cucumber mosaic virus (CMV), one of the main viruses, is responsible for Passiflora spp. (passion fruit) virus diseases, which negatively affect its planting, cultivation, and commercial quality. In this study, a laboratory anti-CMV activity screening model for Passiflora spp. CMV disease was first established. Then, the effects of different antiviral agents of chitosan oligosaccharide (COS), dufulin (DFL), and ningnanmycin (Ning) on CMV virulence rate in Passiflora spp. were determined. The virulence rate and anti-CMV activity in Passiflora spp. treated with COS were 50% and 45.48%, respectively, which were even better than those of DFL (66.67% and 27.30%, respectively) and Ning (83.30% and 9.17%, respectively). Field trials test results showed COS revealed better average control efficiency (47.35%) against Passiflora spp. CMV disease than those of DFL (40.93%) and Ning (33.82%), indicating that COS is effective in the control of the Passiflora spp. CMV disease. Meanwhile, the nutritional quality test results showed that COS could increase the contents of soluble solids, titratable acids, vitamin C, and soluble proteins in Passiflora spp. fruits as well as enhance the polyphenol oxidase (PPO), superoxide dismutase (SOD), and peroxidase (POD) activity in the leaves of Passiflora spp. seedlings. In addition, the combined transcriptome and proteome analysis results showed that COS mainly acted on the Brassinosteroids (BRs) cell signaling pathway, one of plant hormone signal transduction pathway, in Passiflora spp., thus activating the up-regulated expression of TCH4 and CYCD3 genes to improve the resistance to CMV disease. Therefore, our study results demonstrated that COS could be used as a potential plant immune inducer to control the Passiflora spp. CMV disease in the future.

Ozone: a promising alternative to prochloraz for cold storage of pomegranate

There is no detailed study on the effects of different ozone doses, in comparison with fungicide, on the quality losses of pomegranates during cold storage. In the present study, the use of ozone as an alternative to fungicide during cold storage of pomegranate was investigated. Pomegranates were exposed to 1, 2 and 3 ppm gaseous ozone for 3 h and dipped into Prochloraz solution (0.9%) for 10 s. Control samples were only treated with air at the same condition. The fruit were packaged in modified atmosphere bags and stored at 6 ºC and 90 ± 5% relative humidity for 4 months. All ozone doses and fungicide treatment suppressed respiration rate and retarded acidity loss in pomegranates. Fungicide and 1 ppm ozone treatments maintained vivid red color of pomegranates during storage. The 1 ppm ozone was the best treatment for decreasing decay rate of fruit, while high doses had a negative effect. Ozone exposure (1 ppm for 3 h) in air can be an alternative to fungicide during cold storage of pomegranate.

Degradation, migration, and removal of trichlorfon on harvested apples during storage at room temperature

Dissipation of an organophosphorus pesticide, trichlorfon, in natural and waxed apples during storage was studied. The results showed that the trichlorfon content in natural and waxed apples decreased by 85% and 64%, respectively, during storage. The morphology of the surface film was dense and regular, which resulted in a higher water vapor resistance and a lower respiration rate in the waxed apples. This indicates that waxing affected the dissipation of pesticide residues in the apple storage environment, increasing food safety risk. Ozone was used to remove the residual pesticides on the apple surface. The trichlorfon degradation rate reached 73%. The ozone treatment had no effect on the surface color of the apple, which means that the fruit can be pre-treated with ozone prior to waxing or storage.

Phytochemical Composition of Different Botanical Parts of Morus Species, Health Benefits and Application in Food Industry

In recent years, mulberry has acquired a special importance due to its phytochemical composition and its beneficial effects on human health, including antioxidant, anticancer, antidiabetic and immunomodulatory effects. Botanical parts of Morus sp. (fruits, leaves, twigs, roots) are considered a rich source of secondary metabolites. The aim of our study was to highlight the phytochemical profile of each of the botanical parts of Morus tree, their health benefits and applications in food industry with an updated review of literature. Black and white mulberries are characterized in terms of predominant phenolic compounds in correlation with their medical applications. In addition to anthocyanins (mainly cyanidin-3-O-glucoside), black mulberry fruits also contain flavonols and phenolic acids. The leaves are a rich source of flavonols, including quercetin and kaempferol in the glycosylated forms and chlorogenic acid as predominant phenolic acids. Mulberry bark roots and twigs are a source of prenylated flavonoids, predominantly morusin. In this context, the exploitation of mulberry in food industry is reviewed in this paper, in terms of developing novel, functional food with multiple health-promoting effects.

Impacto do retardo do resfriamento na manutenção da qualidade de morangos ‘San Andreas’

Resumo O objetivo deste trabalho foi avaliar o efeito do retardo de resfriamento de morangos ‘San Andreas’ sobre a manutenção da qualidade dos frutos, bem como sobre os compostos fenólicos totais (CFT) e a atividade antioxidante total (AAT), após o armazenamento refrigerado. Os tratamentos consistiram no resfriamento nos tempos de 0 (controle, resfriamento imediato), 3, 6, 9 e 12 horas (em temperatura ambiente), após a colheita. Após a aplicação dos tratamentos, os frutos foram armazenados sob refrigeração (4 ± 0,5 °C e 92 ± 2% de UR), durante 5, 6, 7 e 8 dias, seguidos por mais 2 dias de exposição, em condição ambiente (20 ± 2 °C e 65 ± 5% de UR). Os morangos com o maior retardo de resfriamento apresentaram maior perda de massa fresca, além de menor firmeza, a partir de 7 dias de armazenamento. De maneira geral, os menores valores de incidência e severidade de podridões foram observados nos frutos do tratamento com resfriamento imediato após a colheita, quando armazenados por 7 e 8 dias, seguidos por mais 2 dias em condições ambiente. O retardo do resfriamento por até 6 horas não causa aumento de podridões até 5 dias de armazenamento refrigerado, mais 2 dias em condições ambiente. Os valores de CFT e AAT apresentaram aumento com o retardo de até 6 horas do resfriamento dos frutos, aos 6 dias de armazenamento seguidos por mais 2 dias em condições ambiente, e a AAT aumentou com o aumento do atraso no resfriamento dos frutos em até 12 horas, após 8 dias de armazenamento mais 2 dias em condições ambiente. O atraso no resfriamento causa perdas na qualidade dos frutos de morango, de acordo com o tempo de armazenamento.

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.

Improving Shelf Life, Maintaining Quality, and Delaying Microbial Growth of Broccoli in Supply Chain Using Commercial Vacuum Cooling and Package Icing

Poor and inconsistent quality is a major barrier to increasing produce consumption, and the lack of shelf-life after purchase is the quality issue at retail displays of produce. This research aimed to investigate and identify cooling techniques, namely vacuum cooling and package icing used in supply chains, and any resulting extension of broccoli shelf-life, maintenance of physicochemical quality, and delay in microbial growth at retail stores. Broccoli (Brassica oleracea var. italica cv. Montop) sustainably grown in the highlands of northern Thailand, Chiang Mai Province, under the Royal Project Foundation was experimented on vacuum cooling and package icing were selected to precool broccoli to 4 ± 1 °C. The effects of vacuum cooling using a final pressure of 0.6 kPa for 30 min and package icing using liner Styrofoam boxes (the best ratio of broccoli to crushed ice was 1:1 w/w) on physicochemical qualities, microbial growth, and shelf-life in simulated refrigerated retail displays were examined. The results illustrated that the shelf-life and quality of broccoli could be extended using both vacuum cooling and package icing. Both precooling techniques inhibited the yellowing of florets, provided high sensory scores, delayed microbial growth, and could be able to extend the shelf-life of broccoli. However, package icing offered greater potential for maintaining quality, especially retaining bioactive compounds, and extending shelf-life, thereby increasing the produce market window from 5 to 12 days at 8 ± 1 °C with 85% RH. Therefore, package icing was recommended in the supply chain for fresh broccoli cv. Montop grown in northern Thailand.

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.

Maintaining the Quality and Storage Life of Button Mushrooms (Agaricus bisporus) with Gum, Agar, Sodium Alginate, Egg White Protein, and Lecithin Coating

Button mushrooms have a very short shelf life after harvesting and are sensitive to mechanical damage and browning. This can be a severe problem in enlarging the market and the long-distance exportation of this product. In this respect, edible coatings could be an alternative treatment to extend the shelf life of button mushrooms, maintaining their quality during long-term storage. The aim of this study was to investigate the impact of gum, agar, sodium alginate, egg white protein, and lecithin on the postharvest weight loss, color, browning, respiration rate, ethylene production, and storage life of button mushrooms. The results showed that the above-mentioned edible coatings are a promising way to extend the life and maintain the quality of button mushrooms. Significant differences (p < 0.05) were observed between the control and edible coating-treated samples in all parameters. Sodium alginate and gum were more effective in preventing weight loss, coloring, and browning than other edible coatings. On the other hand, the respiration rate and ethylene production were more suppressed by the agar and lecithin coatings compared to the others. In conclusion, it can be recommended that the above-mentioned edible coatings could be used as novel coatings in commercial treatments for maintaining the quality of button mushrooms during a long-term storage period.

Effect of ozone treatments on the removal of pesticide residues and postharvest quality in green pepper

The use of ozone as a tool in the storage of some horticultural produces is recommended for all steps from harvest to consumption. However, little is known about its effects on the removal of pesticides and postharvest physiology of fresh peppers. In the present study, the effects of ozone treatment on the removal of pesticides, storage life and quality of green peppers were investigated. Malathion, emamectin benzoate and acetamiprid were applied to pepper plants before harvest. Residue contents of peppers were measured at harvest time and after all treatments to determine the effect of ozone on the removal of pesticide residues. Peppers were subjected to four treatments: immersion in ozonated water (2 ppm) and only tap water (control) for 10 min, exposure to 2 ppm ozone gas in air and only air (control) for 45 min. Treated peppers were stored at 20 °C and 60 ± 5% relative humidity for 8 days, and some quality analyses were performed during storage. Ozonated water decreased, remarkable, pesticide residues in peppers compared to harvest time, but there was no meaningful changes in the samples treated with ozone in air. Ozone treatments suppressed clearly respiration rates and decreased weight losses of peppers compared to control groups. Ozonated water also maintained green color of peppers, with minimum change in h° values. Additionally, sensory quality of peppers was retarded by ozone application during storage. These findings revealed that ozone could be an alternative treatment to extend storage life of green peppers and remove pesticide residues.

Comparative transcriptomic analysis of cantaloupe melon under cold storage with ozone treatment

Ozone treatment was found to delay the postharvest cantaloupe melon decay and improve its intrinsic quality during the cold storage. The transcriptomes of cantaloupe peel and pulp in response to ozone treatment were investigated to reveal the mechanisms using a high-throughput RNA sequencing approach. Results showed that 570 and 313 differentially expressed genes were identified in peel and pulp, respectively. According to these identified genes, the gene ontology and pathway enrichment analysis indicated that the ozone treatment could maintain the firmness of the cantaloupe by changing pectin metabolites and reduction of the ethylene production by regulating relevant genes especially in the peel. The total flavonoid content changes in peel and pulp related to the regulation of phenylalanine ammonia lyase, 4-coumarate-CoA ligase and P450 family genes which further leading to the inhibition of phenylalanine metabolic pathway in peel but promotion of secondary metabolism in pulp. The qRT-PCR results were in accordance with our RNA sequencing results which validated the conclusions. The present study for the first time reveals the mechanism of cantaloupe in response to ozone treatment at a transcriptome level which is of importance for cantaloupe storage.

Effects of ozone treatment on the antioxidant capacity of postharvest strawberry

Strawberries are highly popular around the world because of their juicy flesh and unique taste. However, they are delicate and extremely susceptible to peroxidation of their membrane lipids during storage, which induces water loss and rotting of the fruit. This study investigated the effects of ozone treatment on the physiological traits, active oxygen metabolism, and the antioxidant properties of postharvest strawberry. The results revealed that the weight loss (WL) and respiration rate (RR) of strawberry were inhibited by ozone treatment (OT), while the decline of firmness (FIR) and total soluble solids (TSS) were delayed. Ozone also reduced the generation rate of superoxide radical anions , and the content of hydrogen peroxide (H₂O₂) enhanced the activity of superoxidase (SOD), catalase (CAT), ascorbate peroxidase (APX), and monodehydroascorbate reductase (MDHAR), as well as promoted the accumulation of ascorbic acid (ASA), glutathione (GSH), and ferric reducing/antioxidant power (FRAP). In addition, a total of 29 antioxidant-related proteins were changed between the OT group and control (CK) group as detected by label-free proteomics during the storage time, and the abundance associated with ASA–GSH cycle was higher in the OT group at the later stage of storage, and the qRT-PCR results were consistent with those of proteomics. The improvement of the antioxidant capacity of postharvest strawberry treated with ozone may be achieved by enhancing the activity of the antioxidant enzymes and increasing the expression of the antioxidant proteins related to the ascorbic acid–glutathione (ASA–GSH) cycle.

Strawberries are highly popular around the world because of their juicy flesh and unique taste.

Ozonation as a Method of Abiotic Elicitation Improving the Health-Promoting Properties of Plant Products-A Review

In this review, the primary objective was to systematize knowledge about the possibility of improving the health-promoting properties of raw plant products, defined as an increase in the content of bioactive compounds, by using ozone. The greatest attention has been paid to the postharvest treatment of plant raw materials with ozone because of its widespread use. The effect of this treatment on the health-promoting properties depends on the following different factors: type and variety of the fruit or vegetable, form and method of ozone treatment, and dosage of ozone. It seems that ozone applied in the form of ozonated water works more gently than in gaseous form. Relatively high concentration and long contact time used simultaneously might result in increased oxidative stress which leads to the degradation of quality. The majority of the literature demonstrates the degradation of vitamin C and deterioration of color after treatment with ozone. Unfortunately, it is not clear if ozone can be used as an elicitor to improve the quality of the raw material. Most sources prove that the best results in increasing the content of bioactive components can be obtained by applying ozone at a relatively low concentration for a short time immediately after harvest.

Effects of ozone treatment on SOD activity and genes in postharvest cantaloupe

Ozone has been shown to play a positive role in the storage and preservation of agricultural products. However, there is little research on the cantaloupe preservation mechanism of ozone treatment (OT), especially the effect on superoxide dismutase (SOD) and the mechanism of scavenging superoxide anion In this study, xizhoumi 25 was used as a typical cantaloupe material to detect content, hydrogen peroxide (H₂O₂) and SOD enzyme activity in the pericarp and pulp, respectively, and transcriptomics and qRT-RCR were used for cantaloupe SOD family gene expression. The results showed that the rate of and H₂O₂ content were inhibited and SOD activity was higher in the treatment group compared with the control (CK) group in the pericarp and pulp; SOD was more active in the pericarp and was higher than that in the pulp. The transcription level of Cu/Zn-SOD, identified as the most abundant component of the cantaloupe SOD gene family, was promoted in the OT group, especially the key gene Cu/Zn-SOD-1. The expression level of the Fe-SOD gene was promoted in the pericarp but regulated in the pulp, while the expression of the Mn-SOD gene was down-regulated in the OT group in both pericarp and pulp. In addition, the results of qRT-PCR were consistent with the transcriptome results. Correlation analysis showed that OT not only enhanced the positive correlation between and H₂O₂ in the whole cantaloupe and the negative correlation between and SOD activity in the pericarp but also altered the correlation between SOD genes and The mechanism of regulation in postharvest cantaloupe treated with ozone may be through stimulating the SOD activity and altering the expression of related genes in the pericarp and pulp.

Ozone has been shown to play a positive role in the storage and preservation of agricultural products.

Evaluation and optimization of air-based precooling for higher postharvest quality: literature review and interdisciplinary perspective

Precooling is of significant importance for postharvest fruits and vegetables to control the quality degradation and prolong the shelf-life. Current precooling methods include room cooling, forced-air cooling, hydrocooling, vacuum cooling, contact or package icing, and cryogenic cooling, all of which have their advantages and disadvantages. The first two methods with the cooling medium of air are extensively used because of the wide applicable range of fruits and vegetables. Numerous studies have been devoted to cope with the drawbacks of these two air-based precooling methods with various evaluation criteria and optimization methods. A systematic literature review on these studies is firstly conducted with respect to experimental and numerical investigations respectively for the two methods. The main contributions from the previous studies are also summarized respectively with the research objectives and performance metrics. The literature review indicates that the current performance evaluation is limited to apparent parameters and the optimal design is only proposed based on the performance evaluation and comparison. Furthermore, with inspiration from the research in other domains, a scheme of advanced evaluation and optimization for air-based precooling methods is proposed with thermodynamic evaluation metrics and constructal optimization methods from the interdisciplinary perspective.

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.

Combination of Low Fluctuation of Temperature with TiO2 Photocatalytic/Ozone for the Quality Maintenance of Postharvest Peach

Chilling injury, tissue browning, and fungal infection are the major problems of peach fruit during post-harvest storage. In this study, a precise temperature control cold storage with low-temperature fluctuation (LFT) and internal circulation flow system is designed. An ozone (O₃) generator and a (titanium dioxide) TiO₂ photocatalytic reactor were applied to cold storage to investigate the variation of LFT combined with ozone fumigation and a TiO₂ photocatalytic reactor in the efficiency of delaying ripening and maintaining peach fruit quality. Results showed that the temperature fluctuation with the improved control system was only ±0.1 to ±0.2 °C compared with that of ±0.5 to ±1.0 °C in conventional cold storage. LFT significantly reduced the chilling injury of peach fruit during storage. Although LFT combined with fumigation of 200 mg m⁻³ ozone periodical treatment slightly damaged the peach fruit after 40 d of storage, its combination with the TiO₂ photocatalytic system significantly improved the postharvest storage quality of the fruit. This treatment maintained higher titratable acidity (TA), total soluble solids (TSS), better firmness, color, microstructure, and lower decay rate, polyphenol oxidase (PPO) activities, total phenol accumulation, respiratory intensity, ethylene production, and malondialdehyde (MDA) content during 60 d of storage. All the results show that LFT combined with the TiO₂ photocatalytic system might be a promising technology for quality preservation in peach fruit storage.

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.

Natamycin treatment reduces the quality changes of postharvest mulberry fruit during storage

This study investigated the effect of natamycin (NA) treatment on the quality of mulberry fruit throughout the storage at 8°C and 90% relative humidity. The results of this study showed that NA treatment reduced the decay rate of mulberry fruit, inhibited respiration, decreased malondialdehyde (MDA) content, decreased phenylalanine ammonia-lyase (PAL) and polyphenoloxidase (PPO) activity, and maintained sucrose levels, total soluble solids (TSS), and total acids (TA) contents in the fruits throughout storage. NA treatment maintained the surface color and firmness of fruits throughout storage and suppressed the production of fructose, glucose, total phenolics, and the contents of anthocyanin. NA treatment maintained the quality of mulberry fruit throughout storage by enhancing the enzymatic activity of the reactive oxygen species (ROS) scavengers: catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) and inhibiting the production of hydrogen peroxide (H₂ O₂ ). Treatment of mulberries with increasing concentrations of NA could significantly inhibit the growth of fungal pathogens in mulberry fruits and improve their quality. PRACTICAL APPLICATIONS: The results from our previous study showed that NA was a safe preservative which could effectively inhibit the growth of molds and yeasts in mulberry fruits and improve their quality throughout the postharvest storage. Compared with other treatments for mulberry fruit, NA treatment has the advantages of low cost, simple operation, good application, and extension. The results in this study further prove that application of NA treatment has potential in the food industry to maintain the postharvest quality and extend the shelf life of mulberry fruits throughout storage.

Comparative volatile compounds and primary metabolites profiling of pitaya fruit peel after ozone treatment

BACKGROUND

Ozone treatment can effectively inhibit fruit decay in many fruits during postharvest storage. However, little information is available for pitaya fruit.

RESULTS

Ozone treatment significantly reduced the decay rate and induced the enzyme activities of peroxidase and polyphenol oxidase, and also reduced the levels of reactive oxygen species. In total, 103 metabolites were detected and changed the content after ozone treatment, including 54 primary metabolites and 49 aromatic compounds. After significance and importance analysis, 37 metabolites were important. Some metabolites were induced by peel senescence to respond to senescence stress, including d-fructose, d-glucose, mannose, inositol, galactonic acid, ethanedioic acid and stearic acid. Some metabolic products of peel senescence were reduced by ozone treatment, including d-arabinose, glucaric acid, galacturonic acid, 1-hexanol, 4-ethylcyclohexanol, β-linalool, palmitoleic acid and 2-hydroxy-cyclopentadecanone. Some metabolites induced by ozone treatment might play a vital role in delaying the senescence and decay, including malic acid, succinic acid, pentenoic acid, eicosanoic acid, 2-hexenal, hexanal, 2-heptenal, 4-heptenal, 2-octenal and nitro m-xylene.

CONCLUSION

Ozone treatment significantly reduced decay and prolonged shelf-life without reducing fruit quality. In total, 37 metabolites might play an important role in ozone delayed fruit decay. © 2018 Society of Chemical Industry.

Forced Air Precooling Enhanced Storage Quality by Activating the Antioxidant System of Mango Fruits

Effects of forced air precooling on storage quality and physiological metabolism of mangoes were evaluated in this study. Mango fruits were forced air precooled for 30 min at 0°C and then stored at 13°C. Control fruits were stored at 13°C directly. Results showed that forced air precooling treatment maintained fruit firmness, inhibited fruit peel coloration, retarded hydrolysis of polysaccharide to soluble sugar, and decreased fruit decay during storage. Biochemical studies revealed that precooling treatment could eliminate reactive oxygen species (ROS) effects by enhancing related antioxidant enzyme activities, such as superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), glutathione reductase (GR), and polyphenoloxidase (PPO). They all contributed to the delay of mango fruit ripening and senescence in storage. These results indicate that forced air precooling treatment could maintain mango fruit quality by enhancing antioxidant activity and delaying fruit ripening.

Label-free quantitative proteomics to investigate the response of strawberry fruit after controlled ozone treatment

To elucidate postharvest senescence in strawberry (Fragaria ananassa Duch. var. 'JingTaoXiang') fruit in response to ozone treatment at different concentrations (0, 2.144, 6.432, and 10.72 mg m-3), a label-free quantitative proteomic investigation was performed. Postharvest physiological quality traits including respiration rate, firmness, titratable acid, and anthocyanin content were characterized. The observed protein expression profile after storage was related to delayed senescence in strawberries. A total of 2413 proteins were identified in differentially treated strawberry fruits, and 382 proteins were differentially expressed between the four treatments on day 7 and the initial value (blank 0). Proteins related to carbohydrate and energy metabolism and anthocyanin biosynthesis, cell stress response, and fruit firmness were characterized and quantified. Ozone treatment at the concentration of 10.72 mg m-3 effectively delayed the senescence of the strawberry. The proteomic profiles were linked to physiological traits of strawberry fruit senescence to provide new insights into possible molecular mechanisms.

Effects of Ozone Treatment on the Storage Quality of Post-Harvest Tomato

Effects of ozone treatment on the storage quality of post-harvest tomato were investigated. The tomatoes packed in microporous film were treated with 4.29 mg·(m3)−1, 8.57 mg·(m3)−1, 12.86 mg·(m3)−1 and 17.14 mg·(m3)−1 ozone gas for 1 h at 0℃. The firmness, ethylene, vitamin C (VC), malonaldehyde (MDA), ascorbate peroxidase (APX), peroxidase (POD) and aromatic compounds were tested to determine the proper ozone concentrations. Compared with other treatments, 17.14 mg·(m3)−1 ozone could maintain the firmness of tomato, depress ethylene, keep the content of VC and aromatic compounds, and inhibit the accumulation of MDA and activity of POD and APX, which had a good fresh-keeping effect on tomato.