Eugenol treatment delays the flesh browning of fresh-cut water chestnut (Eleocharis tuberosa) through regulating the metabolisms of phenolics and reactive oxygen species

The relationship between cell wall and postharvest physiological deterioration of fresh produce

Postharvest physiological deterioration (PPD) reduces the availability and economic value of fresh produces, resulting in the waste of agricultural products and becoming a worldwide problem. Therefore, many studies have been carried out at the anatomical structural, physiological and biochemical levels and molecular levels of PPD of fresh produces to seek ways to manage the postharvest quality of fresh produce. The cell wall is the outermost structure of a plant cell and as such represents the first barrier to prevent external microorganisms and other injuries. Many studies on postharvest quality of crop storage organs relate to changes in plant cell wall-related components. Indeed, these studies evidence the non-negligible role of the plant cell wall in postharvest storage ability. However, the relationship between cell wall metabolism and postharvest deterioration of fresh produces has not been well summarized. In this review, we summarize the structural changes of cell walls in different types of PPD, metabolic changes, and the possible molecular mechanism regulating cell wall metabolism in PPD of fresh produce. This review provides a basis for further research on delaying the occurrence of PPD of fresh produce.

Pulsed-control plasma-activated water: An emerging technology to assist ultrasound for fresh-cut produce washing

In this study, we explored the use of plasma-activated water (PAW) in combination with ultrasound (US) for food disinfection. Our research introduces a novel approach that utilizes a pulsed-control (PC) method to modify the PAW. The resulting PCPAW exhibits significantly higher concentrations of key reactive oxygen and nitrogen species (RONS) compared to conventional PAW. The disinfection efficacy of US-PCPAW against fresh-cut lettuce was compared to that of US-PAW, US, and PCPAW. The combination of US and PCPAW was highly effective in reducing food-borne pathogens, surpassing single treatments in count reduction and minimizing cross-contamination. Furthermore, our study demonstrates that US-PCPAW effectively controls browning appearance without compromising sensory attributes. These findings suggest that PCPAW, as a novel disinfectant, can be a valuable addition to US to enhance the quality and safety of fresh-cut produce.

Effects of antimicrobial nanocomposite films packaging on the postharvest quality and spoilage bacterial communities of mushrooms (Chanterelles)

Poly (lactic acid) (PLA) composite films with the addition of mesoporous silica nanoparticles MSN (0, 2, 4 and 6 wt%) loaded with 10 wt% citral (CIT) were prepared for application in Chanterelles packaging. Composite films with added MSN/CIT showed good mechanical properties, especially 4MSN/CIT/PLA. Changes in physicochemical properties and bacterial flora of Chanterelles during packaging and storage were tested. Compared with CIT/PLA, Chanterelles packed with 4MSN/CIT/PLA showed about 1.62-times lower browning value, 1.53-times lower electrolyte permeability, and 1.83- and 1.78-times lower PPO and POD, respectively, at 12 day. Better physicochemical properties of Chanterelles can be maintained. For bacterial flora changes, Chanterelles packaged with 4MSN/CIT/PLA had more stable flora (p < 0.05) and lower species diversity during storage (p < 0.05), effectively controlling the growth and reproduction of their dominant spoilage bacteria (Enterobacteriaceae spp). In conclusion, the composite membranes obtained by the addition of MSN/CIT to PLA have great potential in the storage of Chanterelles.

Essential oil-grafted copper nanoparticles as a potential next-generation fungicide for holistic disease management in maize

Sustainable food production is necessary to meet the demand of the incessantly growing human population. Phytopathogens pose a major constraint in food production, and the use of conventional fungicides to manage them is under the purview of criticism due to their numerous setbacks. In the present study, essential oil-grafted copper nanoparticles (EGC) were generated, characterized, and evaluated against the maize fungal pathogens, viz., Bipolaris maydis, Rhizoctonia solani f. sp. sasakii, Macrophomina phaseolina, Fusarium verticillioides, and Sclerotium rolfsii. The ED₅₀ for the fungi under study ranged from 43 to 56 μg ml^-1, and a significant inhibition was observed at a low dose of 20 μg ml^-1 under in vitro conditions. Under net house conditions, seed treatment + foliar spray at 250 and 500 mg L^-1 of EGC performed remarkably against maydis leaf blight (MLB), with reduced percent disease index (PDI) by 27.116 and 25.292%, respectively, in two Kharif seasons (May-Sep, 2021, 2022). The activity of enzymatic antioxidants, viz., β-1, 3-glucanase, PAL, POX, and PPO, and a non-enzymatic antioxidant (total phenolics) was increased in treated maize plants, indicating host defense was triggered. The optimum concentrations of EGC (250 mg L^-1 and 500 mg L^-1) exhibited improved physiological characteristics such as photosynthetic activity, shoot biomass, plant height, germination percentage, vigor index, and root system traits. However, higher concentrations of 1,000 mg L^-1 rendered phytotoxicity, reducing growth, biomass, and copper bioaccumulation to high toxic levels, mainly in the foliar-sprayed maize leaves. In addition, EGC and copper nanoparticles (CuNPs) at 1,000 mg L^-1 reduced the absorption and concentration of manganese and zinc indicating a negative correlation between Cu and Mn/Zn. Our study proposes that the CuNPs combined with EO (Clove oil) exhibit astounding synergistic efficacy against maize fungal pathogens and optimized concentrations can be used as an alternative to commercial fungicides without any serious impact on environmental health.

Structural Characteristics, Rheological Properties, and Antioxidant and Anti-Glycosylation Activities of Pectin Polysaccharides from Arabica Coffee Husks

As primary coffee by-products, Arabica coffee husks are largely discarded during coffee-drying, posing a serious environmental threat. However, coffee husks could be used as potential material for extracting pectin polysaccharides, with high bioactivities and excellent processing properties. Thus, the present study aimed to extract the pectin polysaccharide from Arabica coffee husk(s) (CHP). The CHP yield was calculated after vacuum freeze-drying, and its average molecular weight (Mw) was detected by gel permeation chromatography (GPC). The structural characteristics of CHP were determined by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), proton nuclear magnetic resonance (¹H NMR), and scanning electron microscopy (SEM). Additionally, the rheological and antioxidant properties of CHP and the inhibition capacities of advanced glycation end products (AGEs) with different concentrations were evaluated. The interaction mechanisms between galacturonic acid (GalA) and the AGE receptor were analyzed using molecular docking. The results demonstrated that the CHP yield was 19.13 ± 0.85%, and its Mw was 1.04 × 10⁶ Da. The results of the structural characteristics results revealed that CHP was an amorphous and low-methoxyl pectic polysaccharide linked with an α-(1→6) glycosidic bond, and mainly composed of rhamnose (Rha, 2.55%), galacturonic acid (GalA, 45.01%), β-N-acetyl glucosamine (GlcNAc, 5.17%), glucose (Glc, 32.29%), galactose (Gal, 6.80%), xylose (Xyl, 0.76%), and arabinose (Ara, 7.42%). The surface microstructure of CHP was rough with cracks, and its aqueous belonged to non-Newtonian fluid with a higher elastic modulus (G'). Furthermore, the results of the antioxidant properties indicated that CHP possessed vigorous antioxidant activities in a dose manner, and the inhibition capacities of AGEs reached their highest of 66.0 ± 0.35% at 1.5 mg/mL of CHP. The molecular docking prediction demonstrated that GalA had a good affinity toward AGE receptors by -6.20 kcal/mol of binding energy. Overall, the study results provide a theoretical basis for broadening the application of CHP in the food industry.

Widely Targeted Metabolomics Was Used to Reveal the Differences between Non-Volatile Compounds in Different Wines and Their Associations with Sensory Properties

In this study, metabolites from six varieties of wines, including 'Haasan' (A1), 'Zuoshaner' (A2), 'Beibinghong' (A3), 'Shuanghong' (A4), 'Zijingganlu' (A5), and 'Cabernet Sauvignon' (A6), were identified and quantified using widely targeted metabolomics analysis techniques. Based on the test results, 1172 metabolites were detected and classified into 18 categories. These include 62 amino acids, 178 alkaloids, 189 flavonoids, 106 phenols, 148 terpenoids, etc. Comparing the differential metabolites between the comparison groups of each variety, differences between varieties based on P-values and VIP values were shown. Among these differential metabolites, Trimethoprim and Crotonoside were screened out as core differential metabolites. Multiple comparisons also screened the biomarkers for each species. We used widely targeted metabolomics to reveal the differences between non-volatile compounds in different wines and their associations with sensory properties. We also used the simultaneous weighted gene co-expression network analysis (WGCNA) to correlate metabolites with sensory traits, including color difference values and taste characteristics. Two of the six key modules were screened by WGCNA for relevance to sensory traits (brown module and turquoise module). This study provides a high-throughput method for linking compounds to various sensory characteristics of food, opening up new avenues for explaining differences in different varieties of wine.

Effect and mechanism of eugenol on storage quality of fresh-peeled Chinese water chestnuts

The study aimed to investigate the effect and mechanism of eugenol treatment on fresh-peeled Chinese water chestnuts (CWCs). The results found that eugenol treatment maintained the appearance of fresh-peeled CWCs, accompanied by higher L* value, total solids and O₂ contents, as well as lower browning degree, weight loss rate, CO₂ content, a* and b* values. In addition, eugenol treatment significantly reduced the activities of peroxidase, phenylalanine ammonia-lyase, and polyphenol oxidase, as well as the total content of soluble quinone in fresh-peeled CWCs. Meanwhile, fresh-peeled CWCs treated with eugenol showed markedly lower content of total flavonoids, which may be related to yellowing. Furthermore, eugenol treatment suppressed the rates of O₂·^- and OH·^- production as well as the contents of H₂O₂ and malondialdehyde in fresh-peeled CWCs. During the storage, eugenol treatment not only increased the activities of catalase, superoxide dismutase, ascorbate peroxidase and glutathione reductase as well as the DPPH free radical scavenging rate, but also increased the total phenolics, ascorbic acid and glutathione contents. In summary, eugenol treatment delayed the surface discoloration of fresh-peeled CWCs by improving the antioxidant capacity, inhibiting the phenolic compound metabolism and scavenging ROS, thus effectively maintaining the quality of fresh-peeled CWCs while extending their shelf life.

Anti-browning effects of citronellal on fresh-cut taro (Colocasia esculenta) slices under cold storage condition

The browning on the cut surface is a big problem reducing the quality of fresh-cut taro (FCT), which causes severe postharvest losses and may raise environmental impacts. Citronellal (CA) is a natural compound in several aromatic plants. This study investigated the effects of CA treatments in different concentrations (0.2, 0.5, and 1 mL/L) on the browning of FCT under cold storage at 5°C. The results indicated that low-dose (0.2 mL/L) CA treatment showed best anti-browning effects, reflecting at the maintained L* values but the reduced a*, b* and browning index values by CA treatment during cold storage. A repeated experiment using 0.2 mL/L CA confirmed fine anti-browning effects again. Furthermore, CA (0.2 mL/L) treatment markedly reduced the contents of total phenolic compounds and soluble quinones, restrained the activities of phenylalanine ammonia lyase, peroxidase and polyphenol oxidase, down-regulated the gene expression of 18 browning-related enzymes in FCT. These results together strongly demonstrate the validity of CA on FCT browning prevention. Given that CA is a natural compound existing in plants, low concentration of CA possesses strong anti-browning effects on FCT and also inhibitory effects on pathogens, implying that its application has potentiality to preserve high quality of fresh-cut produce for processing and storage. Moreover, CA treatment significantly decreased malondialdehyde contents and lipoxygenase activity. Correlation analysis indicated that the lipid peroxidation of cell membrane was mostly correlated with FCT browning. The results suggest that membrane lipid peroxidation was a possible reason for FCT browning and CA treatment reduced browning, in part, through alleviating the lipid peroxidation of cell membrane. Overall, our results demonstrate that CA is a novel browning mitigator for FCT under cold storage condition.

Mangifera indica L. Leaves as a Potential Food Source of Phenolic Compounds with Biological Activity

It is well recognized that functional foods rich in antioxidants and antiinflammation agents including polyphenols, probiotics/prebiotics, and bioactive compounds have been found to have positive effects on the aging process. In particular, fruits play an important role in regular diet, promoting good health and longevity. In this study, we investigated on biological properties of extract obtained from Mangifera indica L. leaves in preclinical in vitro models. Specifically, the profile and content of bioactive compounds, the antimicrobial potential toward food spoilage and pathogenic bacterial species, and the eventually protective effect in inflammation were examined. Our findings revealed that MLE was rich in polyphenols, showing a content exclusively in the subclass of benzophenone/xanthone metabolites, and these phytochemical compounds demonstrated the highest antioxidant capacity and greatest in vitro antibacterial activity toward different bacterial species such as Bacillus cereus, B. subtilis, Pseudomonas fluorescens, Staphylococcus aureus, and St. haemolyticus. Furthermore, our data showed an in vitro anti-inflammatory, antioxidant, and antifibrotic activity.