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To solve the problem of difficult hazelnut harvesting in mountainous areas of Liaoning, China, a small pneumatic hazelnut harvesting machine was designed, which can realize negative pressure when picking up hazelnut mixtures and positive pressure when cleaning impurities. The key structure and parameters of the harvesting machine were determined by constructing a mechanical model of the whole machine and combining theoretical analysis and operational requirements. To explore the harvesting machine scavenging performance, Liaoning hazelnut No. 3 with a moisture content of 7.47% was used as the experimental object. Firstly, the terminal velocity of hazelnuts and fallen leaves was measured using a material suspension velocity test bench. Secondly, the gas–solid two-phase flow theory was applied comprehensively, and the motion state, particle distribution, and air flow field distribution of hazelnuts from the inlet to the outlet of the pneumatic conveying device were simulated and analyzed using the coupling of computational flow fluid dynamics method (CFD) and discrete element method (DEM) to evaluate the cleaning performance from the perspective of the net fruit rate of hazelnuts in the cleaning box. Finally, a Box–Behnken design experiment was conducted with the sieve plate angle, the distance of the sieve plate, and the air flow velocity as factors and the net fruit rate of hazelnuts as indicators to explore the influence of the three factors on the net fruit rate of hazelnuts. The parameter optimization module of Design-Expert software was used to obtain the optimal combination of parameters for the factors. The experimental results show that the test factors affecting the test index are the following: the air flow rate, the angle of the screen plate, and the distance of the screen plate. The best combination of parameters was an air flow velocity of 14.1 m∙s−1, a sieve plate angle of 55.7°, and a distance of the sieve plate of 33.2 mm. The net fruit rate of hazelnuts was 95.12%. The clearing performance was stable and can guarantee the requirements of hazelnut harvester operation, which provides a certain theoretical basis for the design of a nut harvester.

Yellowing is one of the main problems of quality deterioration in the storage, transportation, and sales of post-harvested broccoli, which seriously affects the commodity value of broccoli. Therefore, it is of significance to understand the mechanism of the process and develop effective regulation technology. In this review, we expounded the changes in the appearance of the flower ball, bud morphology, and calyx cell structure, as well as endogenous pigment metabolism, accompanying the yellowing process of broccoli. In addition, recent research on the molecular mechanism of yellowing was summarized from the aspects of transcriptome analysis and transcription regulation. Finally, the progress on the control technology of broccoli yellowing was reviewed.

Bell peppers are susceptible to chilling injury (CI). To uncover the metabolism of membrane lipid fatty acids (FAs) accompanying CI, a gas chromatography-mass spectrometry (GC-MS)-based approach was used to quantitatively profile major membrane lipid FAs in bell peppers. RT-qPCR was performed to investigate the expression of the key genes that regulate the synthesis of unsaturated FAs. Additionally, we used microstructural, organoleptic, and physicochemical investigations to monitor the primary physiological metabolism of bell peppers. The study revealed that CI symptoms mostly resulted from the destabilization of the cytomembrane, which was induced by decreasing FA desaturation. Moreover, three times lower level of the double bond index in chilled fruits, than the control, further proved that membrane FA unsaturation can be considered a key factor during CI. In conclusion, this study revealed that the metabolism of membrane lipid FAs is involved in responses to CI.

To explore the effect of 24-epibrassinolide (EBR) on the postharvest yellowing of broccoli (Brassica oleracea var. italica) florets, these were treated with 0–20 μM EBR and kept at 4 °C for 24 days (shelf life). Changes in color, chlorophyll fluorescence, chloroplast ultrastructure, and in the activities of enzymes and expression of genes related to ethylene synthesis and chlorophyll degradation were determined. Low EBR concentrations (2–5 μM) effectively inhibited the yellowing of broccoli, while high EBR concentrations (15–20 μM) accelerated it. On the 24th day, the grana thylakoids of the chloroplasts of 2 μM EBR-treated florets were neatly arranged and clearly visible, while the chloroplast membrane and grana thylakoids of the chloroplast of 20 μM EBR-treated florets were dissolved. Chlorophyll fluorescence was significantly higher in broccoli florets treated with low EBR concentrations than in control broccoli; the opposite was found for broccoli treated with high EBR concentrations. In 20 μM EBR- treated broccoli, the expressions of the genes coding for 1-aminocyclopropane-1-carboxylic acid (ACC) synthase 4 (BoACS4), ACC oxidase 3 (BoACO3), pheophytinase (PPH), and polyamine oxidase (PaO) were increased, accelerating the degradation of chlorophyll, while in 2 μM EBR-treated broccoli the expressions of BoACS4 and BoACO3 were lower than in control broccoli, thereby reducing the production of endogenous ethylene and delaying yellowing. Thus, treatment with 2 μM EBR extends the shelf life of broccoli.

Ethylene and ethylene absorber treatments were used to study the effects of ethylene content on the morphology and pigmentation of broccoli. Results showed that untreated broccoli began to turn yellow 8 days after being harvested at 10 °C. Ethylene treatment caused yellowing to occur 2 days earlier, and ethylene absorber treatment delayed and significantly reduced the degree of yellowing. Yellowing first occurred in the base of the bud; at that time, the shape of the bud had not changed significantly and there was no blooming of the florets. Scanning electron microscopy revealed that the increase in ethylene content caused the calyx cells of broccoli to shrink and that the cell arrangement had become disordered. Ethylene treatment caused increases in the content of chlorophyllide b (Chlide b), pheophorbide b (Pheide b), β-cryptoxanthin, lutein, and β-carotene. The increased degree of yellowing resulted in carotenoids rather than chlorophyll becoming the key pigment (β-cryptoxanthin, β-carotene, and lutein were very significantly correlated with h°). During this change, the expression levels of the BoChl2, BoPaO, BoRCCR, BoPSY, and BoLCYB genes were affected to a greater extent by ethylene. Ethylene absorber treatment did not reduce gene expression, but delayed it. These results indicate that the ethylene absorber only absorbed the ethylene produced and did not directly act on the degradation of chlorophyll. Ethylene also stimulated the expression of BoCCD1 and BoCCD7, resulting in the production of an unknown yellow substance that increased the yellow color of broccoli. In comparison, BoCCD7 expression was more sensitive than BoCCD1.

Postharvest yellowing is the main manifestation in the rapid deterioration of broccoli. Here, we monitored the composition and content changes of glucosinolates accompanying the yellowing process of broccoli to reveal the changes of characteristic bioactive substances along with the appearance changes process. Glucosinolates content was greatly reduced in parallel with the yellowing process. The most prominent reduction was among glucoraphanin and its hydrolysate sulforaphane that decreased by 37 % and 69 %, respectively, during slight yellowing, and up to 85 % and 93 %, respectively when severely yellowed. Among the genes involved in glucoraphanin metabolism pathway, the continuous down-regulation of BoCYP83A1, BoTGG1 and BoTGG2 genes had the most serious impact on the reduction of glucoraphanin and sulforaphane content. Postharvest yellowing influenced the appearance of broccoli commodity, while greatly reduced the nutritional value.

Long-term storage of pear fruit at low temperature can retard senescence but may result in pericarp browning. We previously reported that increasing endogenous γ-aminobutyrate (GABA) content by exogenous GABA treatment can maintain mitochondrial structure integrity, thereby alleviating pericarp browning of ‘Nanguo’ pears after cold storage. Here, we tested the effectiveness of Ca2+ treatment on pericarp browning in relation to GABA biosynthesis. Fruit browning was reduced by treatment with Ca2+ after 180 days of storage. Pericarp Ca2+ and calmodulin content in treated fruit increased, and concomitantly, endogenous GABA content, key GABA synthesis-related enzyme activity, and gene expression were upregulated. Moreover, the mitochondrial structure in the pericarp tissue was found to be well preserved. Thus, Ca2+ treatment effectively reduced pericarp browning of refrigerated ‘Nanguo’ pears owing to improvement in the GABA biosynthesis capacity in the fruit.

Research on advanced glycation end-products (AGEs) and their formation pathways in food processing has gradually increased because AGEs are associated with human health, especially with involvement of lipids. In this study, radicals and glycation products were detected via electron spin resonance (ESR) and ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) respectively. The correlation of important intermediates was used to explain the effect of oleic acid (OA) on the glycation products and pathways. The results indicated OA participation decreased the content of stable radicals and glycosyl compounds in Maillard Reaction (MR). The oxidation of OA produced active radicals, and electron transfer caused lysine to transform radical form. These radicals participated in the formation of fructosyllysine (FL) with glucose (Glc) via the MR. The participation of OA is acted as inhibiting the way of Glc autoxidation and promoting the glycation pathway from FL to 3-deoxyglucosone (3-DG) to fluorescent-AGEs. Orthogonal projection to latent structures discriminant analysis results indicated that 3-DG, D-glucosone and methylglyoxal are key products in discriminating the glycation reaction.

Chilling injury (CI) restricts the quality and shelf life of bell pepper fruits; reducing these CI-induced detrimental effects is therefore of high economic and agricultural relevance. Here, we investigated the effects of trisodium phosphate (TSP), salicylic acid (SA), and TSP + SA treatments on pepper fruits under cold stress at 4 °C for 25 d. Combined TSP + SA treatment performed an optimal effect. Specifically, TSP + SA treatment enhanced fatty-acid desaturation efficiency, as indicated by the increased expression of key fatty acid desaturase genes, and higher content of unsaturated fatty acids. Meanwhile, TSP + SA treatment inhibited the CI-induced membrane damage, manifested as lower electrolyte leakage and malondialdehyde content. Furthermore, low field-nuclear magnetic resonance and proline content also revealed that TSP + SA treatment mitigated CI through enhancing water retention in pepper fruits. Collectively, our results may shed new light on optimizing the low-temperature storage conditions of post-harvest peppers.

Refrigeration is used to retard senescence and extend the storage life of 'Nanguo' pears, but fruits subjected to long-term refrigeration are prone to pericarp browning during subsequent shelf life. To uncover the potential effects of membrane lipid changes during fruit pericarp browning, changes in fruit appearance and cell ultrastructure were observed after different storage durations. Membrane lipid content as well as the activity and gene expression of enzymes involved in membrane lipid metabolism and membrane stability were analyzed. Results showed that long-term refrigeration increased the activity and expression of PLD, LOX, lipase, and membrane stability-related genes that promoted membrane lipid degradation and peroxidation, reduced membrane lipid unsaturation, and led to severe browning. Overall, membrane instability induced by disordered membrane lipid metabolism under low temperature stress may account for pericarp browning of cold stored 'Nanguo' pears.

The blue honeysuckle is a rich source of bioactive compounds. In this study, we obtained a polyphenol-rich blue honeysuckle extract (BHE) and found that cyanidin 3-glucoside and chlorogenic acid accounted for most of its phenolic content. Administration of BHE to mice alleviated silica particle (SP)-induced lung inflammation and reduced the recruitment of macrophages to lungs. BHE also reduced the pro-inflammatory cytokine levels in the bronchoalveolar lavage fluid. In vitro study showed that BHE reduced pro-inflammatory cytokine secretion by macrophages and reduced apoptosis in macrophages. Cell signaling analysis revealed that BHE inhibited p38 and c-Jun N-terminal kinase phosphorylation and decreased the nuclear expression of nuclear factor-κB. BHE treatment also down-regulated the expression of inducible nitric oxide synthase and up-regulated two antioxidant mediators, nuclear factor (erythroid-derived 2)-like 2 and heme oxygenase-1, in macrophages. The findings demonstrated that BHE may serve as a complementary and alternative functional food to prevent SP-induced pulmonary diseases.

We investigated the effect of exogenous glutathione (GSH) on chilling injury (CI) in postharvest bell pepper fruits stored at low temperature and explored the mechanism of this treatment from the perspective of the ascorbate-glutathione (AsA-GSH) cycle. Compared with the control, fruits treated with exogenous GSH before refrigeration displayed only slight CI symptoms and mitigated CI-induced cell damage after 10 d. Moreover, the treated peppers had lower lipid peroxidation product, H2O2, and O2- content than those did the control. Glutathione treatment enhanced the ascorbate-glutathione cycle by upregulating CaAPX1, CaGR2, CaMDHAR1, and CaDHAR1 and the antioxidant enzymes APX, GR, and MDHAR associated with the ascorbate-glutathione cycle. Glutathione treatment also increased ascorbate and glutathione concentrations. Taken together, our results showed that exogenous GSH treatment could alleviate CI in pepper fruits during cold storage by triggering the AsA-GSH cycle and improving antioxidant capacity.

Low-temperature storage is the primary postharvest method employed to maintain fruit quality and commercial value. However, pitting can develop during refrigeration, especially during the shelf life. In this study, a membrane lipidomic approach was employed to analyze the potential relationship between pitting and membrane lipid metabolism during post-cold-storage shelf life. We also determined the changes in ultrastructure and water distribution by low-field nuclear magnetic resonance (LF-NMR) and assessed the permeability of membrane, membrane lipid peroxidation, proline and malondialdehyde contents, and the activity and gene expression of phospholipase D and lipoxygenase, which are involved in membrane lipid metabolism. The results indicated that the changes in blueberry phospholipids during storage could be caused by cold stress. Furthermore, dehydration is a manifestation of chilling injury. Finally, the significant increase in electrolyte leakage, content of malondialdehyde and proline, and activity of phospholipase D and lipoxygenase in chilled blueberry also indicated that membrane lipid metabolism plays an important role in cold stress response.

Melatonin is a kind of indoleamine that plays an important role against abiotic stress. In the current study, we investigated the effect of exogenous melatonin (100 μM) on bell pepper during storage at 4 °C for 20 d and afterward shelf at 20 °C for 3 d. Melatonin treatment reduced cell structure damage and lightened the increase in chilling injury incidence, membrane permeability, and malonaldehyde (MDA) content under cold stress. The membrane lipid content and the ratio of unsaturated to saturated fatty acids increased by reducing the enzymatic activity and transcripts of phospholipase D (PLD) and lipoxygenase (LOX). Besides, melatonin application also inhibited the transcription of CaNAC1, which is the direct targeted regulator of the CaPLD gene. In addition, peppers treated with melatonin had a higher proline content than untreated peppers. Moreover, melatonin triggered the antioxidation protection system in peppers to resist oxidative damage by up-regulating the transcription level of the CaSOD, CaPOD, CaCAT, and CaAPX genes. Our results show that melatonin treatment may be a reliable method to relieve chilling injury in bell pepper fruit via the alleviation of cold-induced membrane lipid peroxidation and activating an antioxidant defense system.

Harvested broccoli is prone to decline in quality with regard to its appearance and nutrition. In this study, freshly harvested broccoli was treated with methyl jasmonate (MeJA) and melatonin (MT) and stored at 20 °C and the changes in sensory qualities and bioactive compounds were analyzed. The control samples began yellowing on day 2, whereas MeJA and MT treatments delayed the yellowing by 2 and 4 days, respectively. Upon yellowing, sweetness and bitterness of control samples increased sharply, accompanied by the accumulation of bioactive compounds, except for sulforaphane; however, no significant change in volatile components was detected. When the samples started losing their green color, MeJA alleviated the bitterness while increasing the sweetness and sulforaphane content. The bitterness, astringency, umami level, and the content of sulfurous volatiles improved significantly in the MT-treated samples. Moreover, these samples showed high antioxidant activity; the protective effect on VC and carotenoids was extremely significant.

The contents of glucose, Ne-(carboxymethyl) lysine (CML), and two main intermediate products, glyoxal (GO) and fructoselysine (FL), were determined, and the corresponding mathematical models were established to investigate the formation and kinetics of CML in a glucose-lysine model heated at 80 °C for 50 h. The effects of oleic acid (OA), temperature, and energy on CML formation were considered in the kinetic models. The mathematical modeling results suggested that glucose consumption was incomplete at 50 h and 80 °C. Although OA contributed to the formation of GO, CML was primarily formed from FL via the Maillard reaction, not from GO. The Arrhenius model was used to deduce that FL is the main pathway in the glucose-lysine-OA system because 88.39 kJ/mol of activation energy via the GO pathway was significantly higher than the 73.97 kJ/mol of activation energy via the FL pathway, and because the rate constant k4 was higher than k3 at different temperatures. OA (50 mmol/L) acted as a catalyst as well as a reactant in CML formation. This is the first study in which CML formation has been determined by both multi-response modeling and kinetic models based on glycation and lipid oxidation.