Maintaining quality of postharvest green pepper fruit using melatonin by regulating membrane lipid metabolism and enhancing antioxidant capacity.

Green pepper quality often deteriorates during storage because of membrane lipid damage and oxidative stress. This study investigated the effects of exogenous melatonin (MT) on green pepper storage quality, membrane lipids, and antioxidant metabolism. The results showed that MT increased the activities of superoxide dismutase, catalase, ascorbate peroxidase, peroxidase, monodehydroascorbate reductase, and dehydroascorbate reductase in green peppers compared to the control group. It upregulated expression of multiple enzymes; reduced accumulation of reactive oxygen species such as dehydroascorbic acid, H2O2, and O2.-; and maintained high ascorbic acid, glutathione, coenzyme II, and nicotinamide adenine dinucleotide while reducing oxidized glutathione levels. In addition, MT decreased lipoxygenase and phospholipase D activities, downregulated ReLOX and RePLD expression, and delayed the degradation of phosphatidylcholine, phosphatidylethanolamine, and oleic, linoleic, and linolenic acids in green peppers. These results suggest that MT helps to improve the chilling injury and quality of green peppers and extends shelf life.

Carboxymethyl chitosan and polycaprolactone-based rapid in-situ packaging for fruit preservation by solution blow spinning.

Nanofiber packaging has not yet gained practical application in fruit preservation because of some limitations, such as low production rate and utilization, and failure due to poor adhesion to the fruit. Herein, to solve this issue, a novel fruit packaging method based on solution blow spinning (SBS), called in-situ packaging, was pioneered. Specifically, carboxymethyl chitosan (CMCH) and polycaprolactone (PCL) were chosen as substrate materials and cherry tomatoes were selected as demonstration subjects. CMCH/PCL nanofibers were deposited directly onto the surface of cherry tomatoes by SBS, forming a tightly adherent and stable fiber coating in 8 min. Also, this in-situ packaging could be easily peeled off by hand. The in-situ packaging was an excellent carrier for active substances and was effective in inhibiting gray mold on cherry tomatoes. The in-situ packaging film formed a barrier on the surface of cherry tomatoes to limit moisture penetration, resulting in reduced respiration of fruits, which led to reduced weight and firmness loss. In addition, metabolomics and color analysis revealed that the in-situ packaging delayed ripening of cherry tomatoes after harvest. Overall, the in-situ packaging method developed in the present work provides a new solution for post-harvest fruit preservation.

Investigating the impact of ultrasound on the structural, physicochemical, and emulsifying characteristics of Dioscorin: Insights from experimental data and molecular dynamics simulation.

This study investigated the impact of ultrasound treatment on dioscorin, the primary storage protein found in yam tubers. Three key factors, namely ultrasound power, duration, and frequency, were focused on. The research revealed that ultrasound-induced cavitation effects disrupted non-covalent bonds, resulting in a reduction in α-helix and ß-sheet contents, decreased thermal stability, and a decrease in the apparent hydrodynamic diameter (Dh) of dioscorin. Additionally, previously hidden amino acid groups within the molecule became exposed on its surface, resulting in increased surface hydrophobicity (Ho) and zeta-potential. Under specific ultrasound conditions (200 W, 25 kHz, 30 min), Dh decreased while Ho increased, facilitating the adsorption of dioscorin molecules onto the oil-water interface. Molecular dynamics (MD) simulations showed that at lower frequencies and pressures, the structural flexibility of dioscorin's main chain atoms increased, leading to more significant fluctuations between amino acid residues. This transformation improved dioscorin's emulsifying properties and its oil-water interface affinity.

Effect of Controlled Atmosphere Packaging on the Physiology and Quality of Fresh-Cut Dictyophora rubrovolvata.

Dictyophora rubrovolvata is a typical edible fungus of Guizhou Province and is very popular due to its unique taste and texture. In this study, the effect of a controlled atmosphere (CA) on fresh-cut D. rubrovolvata shelf life was investigated. Firstly, this study addresses the influence of different O2 concentrations (5%, 20%, 35%, 50%, 65%, 80%, or 95%) with N2 balance on fresh-cut D. rubrovolvata quality while stored at 4 ± 1 °C for 7 d. Then, on the basis of the determined O2 concentration (5%), CO2 (0%, 5%, 10%, 15%, or 20%) was involved and stored for 8 d at 4 ± 1 °C. Evaluations of physiology parameters, texture, browning degree, nutritional, umami, volatile components, and total colony numbers were determined in fresh-cut D. rubrovolvata. From the results of water migration, the sample of 5% O2/5% CO2/90% N2 was closer to 0 d than other groups at 8 days. Meanwhile, the polyphenol oxidase (2.26 ± 0.07 U/(g·min)), and catalase activity (4.66 ± 0.08 U/(g·min·FW)) were superior to the samples of other treatment groups on the eighth day (3.04 ± 0.06 to 3.84 ± 0.10 U/(g·min), 4.02 ± 0.07 to 4.07 ± 0.07 U/(g·min·FW)). Therefore, we found that a gas environment with 5% O2/5% CO2/90% N2 could ensure the membrane integrity, oxidation, and prevent the browning of fresh-cut D. rubrovolvata, thus better maintaining the physiological parameters. Meanwhile, it also maintained the samples' texture, color, nutritional value, and umami taste. Furthermore, it inhibited the increase in total colony numbers. The volatile components were closer to the initial level compared with other groups. The results indicate that fresh-cut D. rubrovolvata could maintain its shelf life and quality when stored in 5% O2/5% CO2/90% N2 at 4 ± 1 °C.

Effects of spray drying and freeze drying on the structure and emulsifying properties of yam soluble protein: A study by experiment and molecular dynamics simulation.

This study focused on the effects of freeze drying (FD) and sprays drying (SD) on the structure and emulsifying properties of yam soluble protein (YSP). The results showed that the surface hydrophobicity (Ho) value, free sulfhydryl group (SH) content, turns content, denaturation temperature and enthalpy value of spray-dried YSP (SD-YSP) were higher than freeze-dried YSP (FD-YSP), but the apparent hydrodynamic diameter (Dh) value of SD-YSP was smaller. The smaller Dh, higher Ho and free SH led to higher percentage of adsorbed proteins and stronger binding between protein and oil droplet in emulsions. Thus, the emulsifying properties of SD-YSP were better, and the SD-YSP-stabilized emulsion had better dynamical rheological properties. Molecular dynamics (MD) simulations suggested that some intramolecular disulfide bonds and hydrogen bonds of dioscorin were broken, and some helices transformed into turns during the SD process. These structural changes resulted in better thermal stability and emulsification properties of SD-YSP.

Revealing the mechanism underlying the effects of γ-aminobutyric acid-dioscorin interactions on dioscorin structure and emulsifying properties by molecular dynamic simulations.

Many studies have shown that γ-aminobutyric acid (GABA) exhibits various beneficial biological activities, including gut-modulating, neuro-stimulating, and cardio-protecting activities. Naturally, GABA exists in small amounts in yam, which is primarily synthesized by the decarboxylation of L-glutamic acid in the presence of glutamate decarboxylase. Dioscorin, the major tuber storage protein of yam, has been shown to have good solubility and emulsifying activity. However, how GABA interacts with dioscorin and affects their properties has yet to be clarified. In this research, the physicochemical and emulsifying properties of GABA-fortified dioscorin, which was dried by spray drying and freeze drying, were studied. As results, the freeze-dried (FD) dioscorin produced more stable emulsions, while the spray-dried (SD) dioscorin adsorbed more rapidly to oil/water (O/W) interface. The fluorescence spectroscopy, ultraviolet spectroscopy and circular dichroism spectroscopy showed that GABA changed the structure of dioscorin, by exposing its hydrophobic groups. The addition of GABA significantly promoted the adsorption of dioscorin to the O/W interface and prevented droplets coalescence. The results of molecular dynamics simulation (MD) showed that GABA destroyed the H-bond network between dioscorin and water, increased surface hydrophobicity and finally improved the emulsifying properties of dioscorin.

Effects of ripening, 1-methylcyclopropene and ultra-high-pressure pasteurisation on the change of volatiles in Chinese pear cultivars.

BACKGROUND: Aroma is one important fruit sensory attribute influenced by the volatile constituents related to species, variety and technological treatments. We analysed the variations of volatile compounds in five pear cultivars and investigated their changes related to different pear organs, different ripening stages, 1-MCP treatment and ultra-high-pressure pasteurisation. RESULTS: Considerable variations exist in the quantity of 10 volatile compounds among five pear cultivars. Their levels generally showed an increasing trend when collected at later harvest time in Ya pear. In Whangkeumbae pear, most volatile compounds reached their maximum levels in skin and pulp. After treating pears with 42 µmol L(-1) 1-methylcyclopropene (1-MCP), the levels of volatiles remained basically unchanged or only slightly increased in Ya pear during a shelf life of 21 days. When Huangguan pear juice was pasteurised by using ultra-high pressure, the levels of volatiles significantly changed during the shelf life. CONCLUSION: The volatile compositions of five different Chinese pear cultivars differ considerably. The levels of these volatiles vary along with ripening stages and pear tissues. A moderate concentration of 1-MCP could keep the levels of volatile compounds basically unchanged during storage and ultra-high-pressure pasteurisation could change the levels of volatiles significantly during the following shelf life.

Chilling injury of tomato fruit was alleviated under low-temperature storage by silencing Sly-miR171e with short tandem target mimic technology.

In this study, the role of Sly-miR171e on post-harvest cold tolerance of tomato fruit was researched. The results showed that overexpression of Sly-miR171e (miR171e-OE) promoted postharvest chilling injury (CI) of tomato fruit at the mature red (MR) and mature green (MG) stage. Contrasted with the wild type (WT) and miR171e-OE fruit, the knockdown of Sly-miR171e (miR171e-STTM) showed a lower CI index, lower hydrogen peroxide (H2O2) content, and higher fruit firmness after harvest. In the fruit of miR171e-STTM, the expression level of GRAS24, CBF1, GA2ox1, and COR, and the GA3 content were ascended, while the expression levels of GA20ox1 and GA3ox1 were descended. The research demonstrated that CI in tomato fruit was alleviated at low temperature storage by silencing Sly-miR171e with short tandem target mimic (STTM) technology. Furthermore, it also provided helpful information for genetic modification of miR171e and control of CI in the postharvest fruit.

Chitosan/PCL nanofibrous films developed by SBS to encapsulate thymol/HPßCD inclusion complexes for fruit packaging.

In this work, the solution blow spinning (SBS) technique was used to rapidly fabricate the thymol (THY)/2-hydroxypropyl-ß-cyclodextrin (HPßCD) inclusion complexes loaded chitosan (CS)/polycaprolactone (PCL) nanofibrous films for fruit preservation and packaging. XRD results indicated that the THY/HPßCD inclusion complexes were successfully incorporated into the CS/PCL nanofibers. The nanofibrous films had an increase of average diameters of nanofibers from 243.84 nm to 560.55 nm, an enhancement of water vapor permeability, a decrease of the crystallinity, and a hydrophilic surface after the incorporation. FTIR and thermal analysis showed that the thermal stability was also improved due to the formation of hydrogen bonds between THY/HPßCD inclusion complexes and CS/PCL nanofibers. The developed films obtained a long-term continuous release of THY during 240 h, and had a good antifungal activity in vitro and in vivo. The above results indicated the promising prospects of SBS in developing antifungal nanofibrous films for postharvest fruit.

Melatonin maintained higher contents of unsaturated fatty acid and cell membrane structure integrity in banana peel and alleviated postharvest chilling injury.

Exogenous melatonin confers the chilling tolerance of banana fruit by promoting reactive oxygen species (ROS) scavenging system and inducing the unsaturated fatty acid synthesis. The results showed that melatonin treatment increased the contents of phospholipids, promoted the ROS scavenging enzyme, and restrained the activities of lipoxygenase (LOX), and thus reduced the lipid peroxidation of banana peel. In addition, melatonin treatment increased the flavonoids and proline contents, which was conducive to antioxidant capacity. Interestingly, the enhanced antioxidant capacity is conducive to the stability of unsaturated fatty acids and reduce the enzymatic browning reaction. Moreover, melatonin treatment induced the expression of omega-3/6 fatty acid desaturase and triggered the fatty acid metabolism activity, by which maintained higher contents of unsaturated fatty acid in banana peel. Moreover, melatonin treatment stimulated the accumulation of fatty acids in banana peel, and was involved in alleviating fruit chilling injury.

Facile microfluidic fabrication and characterization of ethyl cellulose/PVP films with neatly arranged fibers.

Much attention and endeavor have been paid to developing biocompatible food packaging films. Here, ethyl cellulose (EC) and polyvinylpyrrolidone (PVP) were fabricated into films through a facile method, microfluidic spinning. Morphology observations showed that the fibers were neatly arranged with an average diameter of 1-4 µm. FTIR and X-ray diffraction analysis suggested the existence of good compatibility and interaction between EC and PVP. Thermogravimetric analysis demonstrated that PVP ameliorates the thermal properties; moreover, the tensile properties were improved, with tensile strength (TS) and Young's modulus up to 11.10 ± 1.04 MPa and 350.16 ± 45.46 MPa, respectively. The optimal formula was EC/PVP (2:3), of which the film displayed an enhanced TS of 4.61 ± 1.15 MPa and a modified water contact angle of 61.8 ± 4.4°, showing fine tensile and hydrophilic performance. This study provides a facile and green film fabrication method promising to be used for food wrapping.

Cell wall polysaccharides and mono-/disaccharides as chemical determinants for the texture and hygroscopicity of freeze-dried fruit and vegetable cubes.

In order to select the critical factors on the texture and hygroscopic characteristics of freeze-dried fruit and vegetable cubes, the correlation analysis was performed on the major chemical compositions of 12 fresh materials, and the microstructure, texture, hygroscopicity of corresponding freeze-dried samples. The dry proportion of starch-rich materials, such as taro, was mainly composed of polysaccharides (0.76-0.89 g/g db), while the dry proportion of starch-poor materials such as apple was mainly composed of mono-/disaccharides (0.70-0.95/g db). Data from the microscopy showed that cell wall polysaccharides constituted the scaffold of freeze-dried cubes and natural starch granules attached to the scaffold as fillers. Both of them inhibited structural collapse. Mono-/disaccharides were accountable for the hardness and crispiness of freeze-dried cubes, however, excessive mono-/disaccharides could reduce the size of the pores and cause severe shrinkage. Polysaccharides reduced the hygroscopicity of freeze-dried cubes, on the contrary, mono-/disaccharides promoted hygroscopicity, especially fructose.

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.

Preparation, Shelf, and Eating Quality of Ready-to-Eat "Guichang" Kiwifruit: Regulation by Ethylene and 1-MCP.

The acceptance of kiwifruit by consumers is significantly affected by its slow ripening and susceptibility to deterioration. Ready-to-eat "Guichang" kiwifruit and its preparation technology were studied by the regulation of ethylene and 1-MCP. Harvested kiwifruits were treated with 100-2000 µl L-1ethylene for 36 h (20°C) and then treatment with 0-0.5 µl L-1 1-MCP. The results showed that the preservation effect of 0.5 µl L-1 1-MCP is inefficient when the soluble solid content of kiwifruit exceeded 15%. The ethylene-treated fruits reached an "edible window" after 24 h, but a higher concentration of ethylene would not further improve ripening efficiency, while the optimal ethylene concentration was 250 µl L-1. Moreover, after 250 µl L-1 ethylene treatment, 0.5 µl L-1 1-MCP would effectively prolong the "edible window" of fruits by approximately 19 days. The volatile component variety and ester content of 0.5 µl L-1 1-MCP-treated fruits were not different from those of the CK group. Principal component analysis and hierarchical cluster analysis indicated that the eating quality of fruits treated with 0.5 µl L-1 1-MCP was similar to that of fruits treated with ethylene. Consequently, ready-to-eat "Guichang" kiwifruit preparation includes ripening with 250 µl L-1 (20°C, 36 h) ethylene without exceeding the 1-MCP threshold and then treated with 0.5 µl L-1 1-MCP (20°C, 24 h). This study highlights the first development of a facile and low-cost preparation technology for ready-to-eat "Guichang" kiwifruit, which could reduce the time for harvested kiwifruit to reach the "edible window" and prolong the "edible window" of edible kiwifruit.

[Research on nondestructive measurement of soluble tannin content of astringent persimmon using visible and near infrared diffuse reflection spectroscopy].

The objectives of the present study were to establish the relationships of the visible and near infrared diffuse reflection (Vis/NIR) spectroscopy and the soluble tannin content of internal quality index of astringent persimmon, and to evaluate the value of Vis/NIR spectroscopy in measuring the soluble tannin content of internal quality index of astringent persimmon. In the spectral region between 570 and 1 848 nm, calibration results for the soluble tannin content of astringent persimmon were compared with different regression techniques, different derivative treatments and different scatter and standard treatments. The results showed that the modified partial least squares(MPLS) model, with respect to the first derivative D1 log(1/R) and detrend only, provided better prediction performance for the soluble tannin content of astringent persimmon fruit, with the correlation coefficient of cross validation of calibration (R(cv)) and correlation coefficient of prediction (R(p2)), the root mean square error of cross validation of calibration (RMSECV) and the root mean square error of prediction (RMSEP) of 0.722 7, 0.678 5, 0.148, and 0.176 3 respectively. The preliminary research on the built models indicated that nondestructive measurement of the soluble tannin content of astringent persimmon using Vis/NIR spectroscopy technique was feasible, but the precision of the models could be improved further.

Effects of inside-out heat-shock via microwave on the fruit softening and quality of persimmon during postharvest storage.

Rapid postharvest softening largely limits the shelf-life of persimmon (Diospyros kaki L.) fruit. Microwave is a new environmental-friendly inside-out heat-shock approach, whose effect on the fruit softening and quality has not yet been investigated. The current study applied two kinds of microwave treatments (low-power long-time, LPLT, or high-power short-time, HPST) to persimmon fruit with comparison to the hot water (HW) treatments. The results showed both microwave treatments maintained firmness, facilitated the deastringency, and increased soluble solid contents (SSC) and sugar-acid ratio of persimmon fruit. The microwave treatments reduced the cellulose and pectin degradation, and inhibited the cellulase activity, resulting in a significantly higher firmness than HW treatment and control after 2 and 4 days of storage. Moreover, application of HPST treatment down-regulated gene expression of DkPG1, DkPE2 and DkEGase1 compared with untreated fruits. These results indicated that microwave treatment is a promising soft-delaying method for the preservation of persimmon fruit.

Dynamic Changes of DNA Methylation Induced by Heat Treatment Were Involved in Ethylene Signal Transmission and Delayed the Postharvest Ripening of Tomato Fruit.

Deoxyribonucleic acid (DNA) methylation plays an important role in fruit ripening and senescence. Here, the role of DNA methylation of the CpG island of SlACS10, LeCTR1, LeEIN3, LeERT10, and SlERF-A1 genes induced by heat treatment (37 °C) in postharvest ripening of tomato fruit was studied. After heat treatment, the firmness and vitamin C content showed higher levels, the loss of aldehydes in volatile components was delayed, and the activities of methylase and demethylase decreased in tomato fruit. Moreover, in heat-treated fruit, significant changes in DNA methylation of SlACS10, LeCTR1, LeEIN3, LeERT10, and SlERF-A1 were induced, the expression of LeERT10 and LeEIN3 was inhibited, the expression of SlERF-A1 was increased, by which ethylene signal transmission might be suppressed and the postharvest ripening of tomato fruit was delayed. The present study provided valuable information for understanding the essential role of DNA methylation in the postharvest ripening of tomato fruit.

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.

Antifungal activity of 1-methylcyclopropene (1-MCP) against anthracnose (Colletotrichum gloeosporioides) in postharvest mango fruit and its possible mechanisms of action.

Anthracnose caused by Colletotrichum gloeosporioides is one of the most important postharvest diseases in mango fruit, often causing huge economic losses. In this study, the effect of 1-methylcyclopropene (1-MCP) against anthracnose in postharvest mango fruit and the mechanisms involved were investigated. 1-MCP induced reactive oxygen species (ROS) generation, damaged the mitochondria and destroyed the integrity of plasma membrane of spores of C. gloeosporioides, significantly suppressing spore germination and mycelial growth of C. gloeosporioides. 1-MCP also decreased the decay incidence and lesion expansion of mango fruit caused by C. gloeosporioides. For the first time this study demonstrated that 1-MCP suppressed anthracnose of postharvest mango fruit by directly inhibiting spore germination and mycelial growth of C. gloeosporioides, thus providing a promising strategy for disease control.