Effects of in-package atmospheric cold plasma treatment on the qualitative, metabolic and microbial stability of fresh-cut pears.

BACKGROUND: The greatest hurdle to commercial marketing of fresh-cut fruits and vegetables is limited shelf life due to microbial hazards and quality deterioration. Atmospheric cold plasma (ACP) is an emerging non-thermal technology with significant potential to improve the safety and storability of fresh products. The objective of this study was to evaluate the effects of ACP, generated in sealed packaging, on the qualitative, metabolic and microbial stability of fresh-cut pears during simulated cold storage. RESULTS: ACP treatments were effective in inhibiting the growth of mesophilic aerobic bacteria, yeast and mold, particularly CP3 (65 kV, 1 min), which could prolong shelf life to the greatest extent. While decontamination was not always associated with an increase in plasma intensity. Moreover, at 65 kV for 1 min, ACP treatment had the potential to retard respiration, and maintain organoleptic properties and other quality attributes. Additionally, peroxidase and pectin methylesterase (PME) activities were reduced immediately after treatments. These effects were dependent on treatment voltage and time, while a subsequent recovery in activity was only observed for PME. CONCLUSION: The results obtained from this study will contribute to an understanding of the effects of in-package ACP treatments on the storability and microbial safety of fresh-cut pears. This knowledge could be beneficial in reducing quality losses for fresh-cut pears and the preservation of other products. © 2021 Society of Chemical Industry.

Methane delays the senescence and browning in daylily buds by re-established redox homeostasis.

BACKGROUND: During the postharvest senescence of fruits and vegetables, redox imbalance occurs. Although the release of methane (CH4 ) has been observed for a long time and its antioxidant properties have recently been demonstrated in animals and plants, the corresponding physiological role of CH4 in regulating plant senescence has not yet been elucidated. RESULTS: Our results indicate that the postharvest deterioration of daylily buds during storage is greatly ameliorated by the exogenous application of CH4 , particularly in the inhibition of tissue browning. The results are supported by a decrease in the degree of browning and by the corresponding phenotype, which are correlated with the suppressed polyphenoloxidase activity. CH4 also maintains the re-establishment of redox balance, as indicated by the lower relative leakage rate, lipid peroxidation level, and reactive oxygen species accumulation in daylily buds. Furthermore, the decrease of the unsaturated/saturated fatty acid ratio and energy charge during storage was also attenuated. CONCLUSION: These results clearly suggest that the postharvest treatment with CH4 is an effective means of prolonging the storage life of daylily buds. © 2017 Society of Chemical Industry.

Control of postharvest soft rot caused by Erwinia carotovora of vegetables by a strain of Bacillus amyloliquefaciens and its potential modes of action.

Erwinia carotovora subsp. carotovora (Ecc), the causal agent of bacterial soft rot, is one of the destructive pathogens of postharvest vegetables. In this study, a bacterial isolate (BGP20) from the vegetable farm soil showed strong antagonistic activity against Ecc in vitro, and its twofold cell-free culture filtrate showed excellent biocontrol effect in controlling the postharvest bacterial soft rot of potatoes at 25 °C. The anti-Ecc metabolites produced by the isolate BGP20 had a high resistance to high temperature, UV-light and protease K. Based on the colonial morphology, cellular morphology, sporulation, and partial nucleotide sequences of 16S rRNA and gyrB gene, the isolate BGP20 was identified as Bacillus amyloliquefaciens subsp. plantarum. Further in vivo assays showed that the BGP20 cell culture was more effective in controlling the postharvest bacterial soft rot of green peppers and Chinese cabbages than its twofold cell-free culture filtrate. In contrast, the biocontrol effect and safety of the BGP20 cell culture were very poor on potatoes. In the wounds of potatoes treated with both the antagonist BGP20 and the pathogen Ecc, the viable count of Ecc was 31,746 times that of BGP20 at 48 h of incubation at 25 °C. But in the wounds of green peppers, the viable count of BGP20 increased 182.3 times within 48 h, and that of Ecc increased only 51.3 %. In addition, the treatment with both BGP20 and Ecc induced higher activity of phenylalanine ammonia-lyase (PAL) than others in potatoes. But the same treatment did not induce an increase of PAL activity in green peppers. In conclusion, the present study demonstrated that the isolate BGP20 is a promising candidate in biological control of postharvest bacterial soft rot of vegetables, but its main mode of action is different among various vegetables.

The glucosinolate profiles of Brassicaceae vegetables responded differently to quick-freezing and drying methods.

Glucosinolates (GLS) are bioactive compounds found in Brassicaceae vegetables. Industrial food processing treatments, such as blanching, quick-freezing (QF), vacuum freeze-drying (VFD), vacuum-drying (VD) and oven-drying (OD), significantly affect the degradation and ingestion of GLS. Here, the effects of these treatments, followed by boiling, on the GLS content and mimicking ingestion level of isothiocyanate from Brassicaceae vegetables (broccoli, cauliflower, white and red cabbages, Chinese and baby cabbages, white and red radish roots) were investigated. The results showed that blanching-QF maintained or increased the GLS content as well as preserved the ingestion level of isothiocyanate, an optimum treatment for GLS preservation. Blanching-VFD was recommended for these vegetables, while blanching-VD and blanching-OD caused relatively high GLS losses and low isothiocyanate production. Additionally, stabilities of individual GLS during processing rely on their chemical structures and species. Generally, aliphatic GLS from Brassicaceae showed lower loss than indole GLS, indicating differences in their stabilities during processing.

Post-harvest Application of Methyl Jasmonate or Prohydrojasmon Affects Color Development and Anthocyanins Biosynthesis in Peach by Regulation of Sucrose Metabolism.

The roles of methyl jasmonate (MeJA) and prohydrojasmon (PDJ) in postharvest color development and anthocyanins biosynthesis in the skin of peach fruit remain unclear. In this study, peach fruit were infiltrated with MeJA (200 µM) or PDJ (40 µM) and stored at 22°C for 7 days. The results showed that treatment with MeJA or PDJ had a positive effect on red color formation in peach fruits due to anthocyanins accumulation (∼120% increase). This was attributed to increased enzyme activities, and enhanced transcript abundance of the genes associated with anthocyanins biosynthesis, induced by MeJA or PDJ. Both MeJA and PDJ promoted sucrose biosynthesis, and the subsequently elevated levels of the sucrose during storage were positively correlated with anthocyanins accumulation (0.49) and the activities of key biosynthesis enzymes (0.42-0.79). Based on these findings, we proposed that MeJA or PDJ treatments promote anthocyanins biosynthesis by regulating sucrose metabolism during the postharvest storage of peach fruit.

Nondestructive Detection of Weight Loss Rate, Surface Color, Vitamin C Content, and Firmness in Mini-Chinese Cabbage with Nanopackaging by Fourier Transform-Near Infrared Spectroscopy.

A nondestructive optical method is described for the quality assessment of mini-Chinese cabbage with nanopackaging during its storage, using Fourier transform-near infrared (FT-NIR) spectroscopy. The sample quality attributes measured included weight loss rate, surface color index, vitamin C content, and firmness. The level of freshness of the mini-Chinese cabbage during storage was divided into three categories. Partial least squares regression (PLSR) and the least squares support vector machine were applied to spectral datasets in order to develop prediction models for each quality attribute. For a comparative analysis of performance, the five preprocessing methods applied were standard normal variable (SNV), first derivative (lst), second derivative (2nd), multiplicative scattering correction (MSC), and auto scale. The SNV-PLSR model exhibited the best prediction performance for weight loss rate (Rp2 = 0.96, RMSEP = 1.432%). The 1st-PLSR model showed the best prediction performance for L* value (Rp2 = 0.89, RMSEP = 3.25 mg/100 g), but also the lowest accuracy for firmness (Rp2 = 0.60, RMSEP = 2.453). The best classification model was able to predict freshness levels with 88.8% accuracy in mini-Chinese cabbage by supported vector classification (SVC). This study illustrates that the spectral profile obtained by FT-NIR spectroscopy could potentially be implemented for integral assessments of the internal and external quality attributes of mini-Chinese cabbage with nanopacking during storage.

An efficient fluorescent nano-sensor of N-doped carbon dots for the determination of 2,4,6-trinitrophenol and other applications.

N-Doped carbon dots (CDs) had been simply produced by a one-pot synthesis process using amygdalic acid and threonine. The resulting product was water-soluble and exhibited strong luminescence emission with a fluorescence quantum yield of 19.25%. The emission of CDs was obviously and selectively decreased upon adding 2,4,6-trinitrophenol (TNP). It was proved that the fluorescence resonance energy transfer was the main mechanism for quenching. An efficient fluorescence probe with satisfied sensitivity for TNP determination was found. The range of the linear response for TNP detection was 0.5-40.0 µmol L-1, and the limit of detection was 20 nmol L-1. The content of trace TNP in water samples was successfully detected with this method. The CDs were also applied in HepG2 cell imaging and the fabrication of fluorescent films by dispersing the solid freeze-drying CD (SCD) powder into PMMA, which exhibited some application value in biology and photovoltaics.

Combined transcriptomics and proteomics analysis provides insight into metabolisms of sugars, organic acids and phenols in UV-C treated peaches during storage.

3Ultraviolet-C (UV-C) irradiation is known for prolonging the shelf life of many fruit by regulating different pathways. To better understand the roles of UV-C treatment in regulating the metabolic pathways in peach fruit during cold storage, transcriptomics and proteomics approaches were applied to investigate changes in peaches treated with UV-C (1.5 kJ m-2). The results showed that most differentially expressed genes (DEGs) and differentially expressed proteins (DEPs) were largely matched to carbohydrates and secondary metabolites. Further analysis found that peaches treated with UV-C exhibited higher sucrose, citric acid, malic acid, phenols, flavonoids and anthocyanins compared with untreated peaches. Proteomics and transcriptomics together indicated that changes of sugars and acids were associated with the expressions of invertase, sucrose synthase, fructokinase, malate dehydrogenase and citrate synthase. UV-C irradiation promoted the synthesis of phenols, flavonoids and anthocyanins by up-regulating expressions of phenylalanine ammonia-lyase, 4-coumarate-CoA ligase, chalcone synthase, dihydroflavonol 4-reductase and UDP-glucose:flavonoid glucosyltransferase. In summary, this research explained the general molecular mechanism of the changes of sugars, acids and phenols in peaches in response to UV-C.

Genome-Wide Identification of the Vacuolar H+-ATPase Gene Family in Five Rosaceae Species and Expression Analysis in Pear (Pyrus bretschneideri).

Vacuolar H+-ATPases (V-ATPase) are multi-subunit complexes that function as ATP hydrolysis-driven proton pumps. They play pivotal roles in physiological processes, such as development, metabolism, stress, and growth. However, there have been very few studies on the characterisation of V-ATPase (VHA) genes in Rosaceae species. Therefore, in the present study, we performed a genome-wide analysis and identified VHA gene family members in five Rosaceae species (Pyrus bretschneideri, Malus domestica, Prunus persica, Fragaria vesca, and Prunus mume). A total of 159 VHA genes were identified, and were classified into 13 subfamilies according to the phylogenetic analysis. The structure of VHA proteins revealed high similarity among different VHA genes within the same subgroup. Gene duplication event analysis revealed that whole-genome duplications represented the major pathway for expansion of the Pyrus bretschneideri VHA genes (PbrVHA genes). The tissue-specific expression analysis of the pear showed that 36 PbrVHA genes were expressed in major tissues. Seven PbrVHA genes were significantly downregulated when the pollen tube growth stopped. Moreover, many PbrVHA genes were differentially expressed during fruit development and storage, suggesting that VHA genes play specific roles in development and senescence. The present study provides fundamental information for further elucidating the potential roles of VHA genes during development and senescence.

Physiological and transcriptomic analysis of 'Whangkeumbae' pear core browning during low-temperature storage.

Core browning of 'Whangkeumbae' pear has become an urgent problem in the Chinese pear industry, which often appears after several months of low-temperature storage. However, little is known regarding the crosstalk between physiology and molecular mechanisms regulating the core browning process of the pear. In this study, the physiological and genetic responses of the core were identified during storage. The results showed that the malonyldialdehyde (MDA) content, electrolyte leakage, hydrogen peroxide (H2O2) content and superoxide anion (O2·-) production rate progressively increased during the browning process. Polyphenoloxidase (PPO), phospholipase D (PLD) and lipoxygenase (LOX) activity initially slightly increased but then sharply increased during the later storage stage. A total of 33,265 unigenes was generated via high-throughput sequencing, and 5121 differentially expressed genes (DEGs) were identified. These DEGs were functionally annotated and some core browning-related DEGs involved in the redox reaction, membrane lipid metabolism and enzymatic browning were also determined. We found that the changes in the gene expression accorded with the physiological variation, indicating the close crosstalk between physiological and genetic response during storage. Our study provides a basis for future research on the core browning mechanism during pear storage.

Potential of jasmonic acid (JA) in accelerating postharvest yellowing of broccoli by promoting its chlorophyll degradation.

Chlorophyll degradation is the main reason for postharvest yellowing of broccoli. To uncover the role of jasmonic acid (JA) on the degradation of chlorophyll, broccoli flowers were treated with exogenous methyl jasmonate (MeJA) and diethyldithiocarbamic acid (DIECA). We found a surge of endogenous JA content with the yellowing process, and a significant correlation between JA and chlorophyll content. MeJA treatments led to increased endogenous JA, increased allene oxide cyclase (AOC) activity, and enhanced expression of JA synthesis genes. MeJA caused a stronger reduction in the maximum quantum yield (Fv/Fm), fluorescence decline ratio (Rfd), and total chlorophyll content, advanced the peak of pheide a oxygenase (PAO) activity, and up-regulated the expression of chlorophyll degradation genes. The DIECA treatment resulted in lower endogenous levels of JA, and AOC and 12-oxo-phytodienoic acid reductase (OPR) activity. This study revealed that the potential role of JA on broccoli yellowing is to promote the chlorophyll degradation.

One-pot synthesis of aqueous soluble and organic soluble carbon dots and their multi-functional applications.

Two kinds of carbon dots (CDs) with different solubility, aqueous soluble CDs (ACDs) and organic soluble CDs (OCDs), were produced at the same time by one step hydrothermal synthesis method using sorbic acid and proline as carbon precursor and nitrogen dopant, respectively. The synthesized CDs were characterized by means of UV, fluorescence, TEM, elemental analysis, IR and XPS et al. Based on the effective and proportional fluorescence quenching by Cr(VI), ACDs were successfully used as a high sensitive and selective probe for Cr(VI) detection. Internal filtration effect (IFE) played an important role in the quenching process. Under the optimal conditions, linear response for Cr(Ⅵ) was observed in the range of 0.5-100 µmol/L, and the calculated detection limit was 34 nmol/L. The method has been satisfactorily applied to detect Cr(VI) ions in real water samples of our campus. Then, the ACDs were further applied for cell imaging in B16F10 cells. Furthermore, OCDs were well dispersed into PMMA to fabricate OCDs/PMMA composites as fluorescent films.

Endogenous Hydrogen Sulfide Homeostasis Is Responsible for the Alleviation of Senescence of Postharvest Daylily Flower via Increasing Antioxidant Capacity and Maintained Energy Status.

There are limited data concerning the role of endogenous H2S in prolonging the postharvest of vegetables and fruits. Using a fluorescence microscope with a specific probe, we discovered that, during the senescence of postharvest daylily flower, endogenous H2S homeostasis was impaired. The activities of two important synthetic enzymes of H2S, l- and d-cysteine desulfhydrase, exhibited decreasing tendencies. However, NaHS (a H2S donor) not only blocked the decreased H2S production but also extended the postharvest life of daylilies. These beneficial roles were verified by the alleviation of lipid peroxidation and the increased activities of antioxidant enzymes. Meanwhile, the energy status was sustained, and the respiration rate was decreased. In contrast to NaHS, the addition of an inhibitor of H2S synthesis alone aggravated lipid peroxidation and lowered energy charge. Together, the present study implies that endogenous H2S alleviates senescence of postharvest daylilies via increasing antioxidant capacity and maintained energy status.

Hydrogen-rich water delays postharvest ripening and senescence of kiwifruit.

The effect of hydrogen-rich water (HRW) on prolonging the shelf life of kiwifruit and possible underlying mechanisms were assessed. Our results revealed that HRW (30%, 80%, and 100%) displayed different effects in inhibiting the rot of kiwifruit. Among these treatments, 80% HRW had the most significant effect by decreasing the rot incidence and preserving the firmness of kiwifruit. This conclusion was supported by the fact that 80% HRW treatment could effectively alleviate pectin solubilization and reduce the activities of cell wall-degrading enzymes. On the other hand, HRW treatment was able to reduce the respiration intensity, increase the activity of superoxide dismutase, decrease lipid peroxidation level, and maintain the radical (DPPH,O2(-),andOH)-scavenging activity of kiwifruit. Moreover, the inner membrane of mitochondria exhibited higher integrity. Thus, our results demonstrate that HRW treatment could delay fruit ripening and senescence during storage by regulating the antioxidant defence.

Separation and identification of anthocyanin extracted from mulberry fruit and the pigment binding properties toward human serum albumin.

Purple pigments were isolated from mulberry extracts using preparative high-speed countercurrent chromatography (HSCCC) and identified by ESI-MS/MS and high performance liquid chromatography (HPLC) techniques. The solvent system containing methyl tert-butyl ether, 1-butanol, acetonitrile, water, and trifluoroacetic acid (10:30:10:50:0.05; %, v/v) was developed in order to separate anthocyanins with different polarities. Cyanidin 3-O-(6″-O-α-rhamnopyranosyl-ß-galactopyranoside) (also known as keracyanin) is the major component present in mulberry (41.3%). Other isolated pigments are cyanidin 3-O-(6″-O-α-rhamnopyranosyl-ß-glucopyranoside) and petunidin 3-O-ß-glucopyranoside. The binding characteristics of keracyanin with human serum albumin (HSA) were investigated by fluorescence and circular dichroism (CD) spectroscopy. Spectroscopic analysis reveals that HSA fluorescence quenched by keracyanin follows a static mode. Binding of keracyanin to HSA mainly depends on van der Waals force or H-bonds with average binding distance of 2.82 nm. The results from synchronous fluorescence, three-dimensional fluorescence, and CD spectra show that adaptive structure rearrangement and decrease of α-helical structure occur in the presence of keracyanin.

Neuroprotective effects of macranthoin G from Eucommia ulmoides against hydrogen peroxide-induced apoptosis in PC12 cells via inhibiting NF-κB activation.

Oxidative stress-mediated cellular injury has been considered as a major cause of neurodegenerative diseases including Alzheimer and Parkinson diseases. The scavenging of reactive oxygen species (ROS) mediated by antioxidants may be a potential strategy for retarding the disease's progression. Macranthoin G (MCG), isolated from Eucommia ulmoides, is a derivative from chlorogenic acid methyl ester and caffeic acid. This study is aimed to investigate the protective role of MCG against the cytotoxicity induced by hydrogen peroxide (H2O2) and to elucidate potential protective mechanisms in rat pheochromocytoma (PC12) cells. The results showed that the treatment of PC12 cells with MCG prior to H2O2 exposure effectively increased the cell viability, and stabilized the mitochondria membrane potential (MMP); furthermore, it enhanced the antioxidant enzyme activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) and the levels of intracellular glutathione (GSH); it also decreased the malondialdehyde (MDA) content, intracellular ROS, caspase-3 activation, as well as cell apoptosis. In addition, the MCG treatment minimized the cell injury by H2O2 via down-regulation of the NF-κB pathway as well as activation of phosphorylation of IκBα, p38, and the extracellular signal-regulated kinase (ERK). These results showed that that MCG is promising as a potential therapeutic agent for neurodegenerative diseases induced by oxidative damage and should be encouraged for further research.