Chitosan-based melatonin bilayer coating for maintaining quality of fresh-cut products

An insect lac blanket-mimetic and degradable shellac hydrogel/chitosan packaging film with controllable gas permeation for fresh-cut vegetables preservation

Fresh-cut products are extremely perishable due to the processing operations, and the atmosphere environment, especially CO2, O2 and H2O, could profoundly affect their shelf life. Herein, an insect "lac blanket"-mimetic and facile strategy was proposed for fresh-cut vegetables preservation, employing porous shellac hydrogel microparticles as gas "switches" in chitosan film to regulate CO2, O2 and H2O vapor permeability. Thus, the shellac hydrogel/chitosan hybrid film presented the controllable and wide range of gas permeability, compared with the chitosan film. The shellac-COOH nanoscale vesicles aggregated to form shellac hydrogel network via hydrophobic binding. The shellac hydrogel microparticles played a certain lubricating effect on the hybrid film casting solution. The hydrogen bond network between shellac hydrogel and chitosan contributed to the excellent mechanical properties of the hybrid film. The hybrid film also exhibited remarkable water-resistant, antifogging properties, optical transparency and degradability. The hybrid packaging films prepared through this strategy could adjust the internal gas (CO2, O2, H2O and ethylene) contents within the packages, and further exhibited admirable preservation performance on three fresh-cut vegetables with different respiratory metabolisms. This gas permeation-controlled strategy has great potential in fresh food preservation and various other applications that need a modified atmosphere.

Nanovehicles for melatonin: a new journey for agriculture

The important role of melatonin in plant growth and metabolism together with recent advances in the potential use of nanomaterials have opened up interesting applications in agriculture. Various nanovehicles have been explored as melatonin carriers in animals, and it is now important to explore their application in plants. Recent findings have substantiated the use of silicon and chitosan nanoparticles (NPs) in targeting melatonin to plant tissues. Although melatonin is an amphipathic molecule, nanocarriers can accelerate its uptake and transport to various plant organs, thereby relieving stress and improving plant shelf-life in the post-harvest stages. We review the scope and biosafety concerns of various nanomaterials to devise novel methods for melatonin application in crops and post-harvest products.

Postharvest melatonin and chitosan treatments retain quality of 'Williams' bananas during ripening

The effect of postharvest dipping treatments with 0.5 mM melatonin (MT) and 1% chitosan (CT) either alone or in combination on quality of pre-climacteric 'Williams' bananas during ripening at ambient conditions were investigated. MT or CT treatments delayed ripening by retaining greener peel, higher firmness, titratable acidity (TA), but lower total soluble solids (TSS) and TSS/TA, weight loss, browning and electrolyte leakage than the control. Total phenol (TPC) and flavonoid contents (TFC) in both peel and pulp increased up to 6 days and then decreased and was higher in treated fruit than the control. Vitamin C content decreased up to 3 days, then increased and was higher in treated fruit than control. MT and CT combination exhibited the highest TPC, TFC and vitamin C contents compared to other treatments. Radical scavenging capacity (RSC) of peel and pulp increased up to 6 days, then decreased and was higher in treated fruit than the control. The treated fruit exhibited lower polyphenoloxidase (PPO) and hydrolytic enzymes but higher peroxidase (POD) activities in both peel and pulp than the control. Postharvest treatments with 0.5 mM MT and 1% CT alone or in combination could be used to retain quality of 'Williams' bananas during ripening.

Injectable adhesive carboxymethyl chitosan-based hydrogels with self-mending and antimicrobial features for the potential management of periodontal diseases

Treating periodontal diseases is a great challenge owing to the motion and wet conditions, bacterial infection, and tissue defects. Therefore, designing bioactive materials with outstanding wet-tissue adhesion, antimicrobial features, as well as favorable cell responses, is highly desirable to meet practical necessity. In this work, bio-multifunctional melatonin-loaded carboxymethyl chitosan/polyaldehyde dextran (CPM) hydrogels have been developed through the dynamic Schiff-base reaction. Our results demonstrate that the CPM hydrogels display injectability, structural stability, and high tissue adhesion in the wet and motional state, as well as self-healing features. In addition, the designed hydrogels show great antibacterial properties and excellent biocompatibility. The prepared hydrogels display a slow release of melatonin. Moreover, the in vitro cellular assay indicates that the developed hydrogels containing 10 mg per mL melatonin significantly promote cell migration. Thus, the synthesized bio-multifunctional hydrogels show great promise in the treatment of periodontal disease.

Functions of Melatonin during Postharvest of Horticultural Crops

Melatonin, a tryptophan-derived molecule, is endogenously generated in animal, plant, fungal and prokaryotic cells. Given its antioxidant properties, it is involved in a myriad of signaling functions associated with various aspects of plant growth and development. In higher plants, melatonin (Mel) interacts with plant regulators such as phytohormones, as well as reactive oxygen and nitrogen species including hydrogen peroxide (H2O2), nitric oxide (NO) and hydrogen sulfide (H2S). It shows great potential as a biotechnological tool to alleviate biotic and abiotic stress, to delay senescence and to conserve the sensory and nutritional quality of postharvest horticultural products which are of considerable economic importance worldwide. This review provides a comprehensive overview of the biochemistry of Mel, whose endogenous induction and exogenous application can play an important biotechnological role in enhancing the marketability and hence earnings from postharvest horticultural crops.

Chitosan and its composites-based delivery systems: advances and applications in food science and nutrition sector

Natural bioactive ingredients have lower bioavailability because of their chemical instability and poor water solubility, which limits their applications in functional foods. Among diverse biopolymers that can be used to construct delivery systems of bioactives, chitosan has attracted extensive attention due to its unique cationic nature, excellent mucoadhesive properties and easy modification. In this review, chitosan and its composites-based food-grade delivery systems as well as the factors affecting their performance are summarized. Modification, crosslinking, combination with other biopolymer or utilization of coating material can effectively overcome the instability of pure chitosan-based carriers under acidic conditions, thereby constructing chitosan and its complex-based carriers with conspicuously improved performance. Furthermore, the applications of chitosan-based delivery systems in nutrition and health as well as their future development trends and challenges are discussed. Functional food ingredients, functional food packaging and biological health are potential applications of chitosan-based food-grade delivery systems. The research trends of nutraceutical delivery systems based on chitosan and its composites include co-delivery of nutrients and essential oils, targeted intestinal delivery, stimulus responsive/sustained release and their applications in real foods. In conclusion, food industry will be significantly promoted with the continuous innovation and development of chitosan-based nutraceutical delivery systems.

Chitin Nerve Conduits with Three-Dimensional Spheroids of Mesenchymal Stem Cells from SD Rats Promote Peripheral Nerve Regeneration

Peripheral nerve injury (PNI) is an unresolved medical problem with limited therapeutic effects. Epineurium neurorrhaphy is an important method for treating PNI in clinical application, but it is accompanied by inevitable complications such as the misconnection of nerve fibers and neuroma formation. Conduits small gap tubulization has been proved to be an effective suture method to replace the epineurium neurorrhaphy. In this study, we demonstrated a method for constructing peripheral nerve conduits based on the principle of chitosan acetylation. In addition, the micromorphology, mechanical properties and biocompatibility of the chitin nerve conduits formed by chitosan acetylation were further tested. The results showed chitin was a high-quality biological material for constructing nerve conduits. Previous reports have demonstrated that mesenchymal stem cells culture as spheroids can improve the therapeutic potential. In the present study, we used a hanging drop protocol to prepare bone marrow mesenchymal stem cell (BMSCs) spheroids. Meanwhile, spherical stem cells could express higher stemness-related genes. In the PNI rat model with small gap tubulization, BMSCs spheres exhibited a higher ability to improve sciatic nerve regeneration than BMSCs suspension. Chitin nerve conduits with BMSCs spheroids provide a promising therapy option for peripheral nerve regeneration.

Improving the Berry Quality and Antioxidant Potential of Flame Seedless Grapes by Foliar Application of Chitosan-Phenylalanine Nanocomposites (CS-Phe NCs)

The production and sustainability of grape berries with high quality and health-promoting properties is a major goal. In this regard, nano-engineered materials are being used for improving the quality and marketability of berries. In this study, we investigated the potential role of chitosan–phenylalanine nanocomposites (CS–Phe NCs) in improving the quality of Flame Seedless (Vitis vinifera L.) grape berries, such as titratable acidity (TA), pH, total soluble solids (TSS), ascorbic acid, total phenolics, total flavonoids, anthocyanin, 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) radical scavenging activity, and phenylalanine ammonia-lyase (PAL) activity. In this context, grape berries collected in two growing seasons (2018–2019) were screened. Regarding the experimental design, the treatments included chitosan at a 0.5% concentration (CS 0.5%), phenylalanine at 5 mM and 10 mM concentrations (Phe 5 mM and Phe 10 mM), and chitosan–phenylalanine nanocomposites (CS–Phe NCs) at 5 mM and 10 mM concentrations. The lowest TA was recorded in grape berries treated with CS–Phe NCs with a 10 mM concentration. However, treatments enhanced with TSS, which reached the highest value with 10 mM of CS–Phe NCs, were reflected as the highest ratio of TSS/TA with 10 mM of CS–Phe NC treatment. Nanocomposites (NCs) also increased pH values in both study years compared to the control. Similarly, the ascorbic acid and total phenolic content increased in response to NP treatment, reaching the highest value with 5 mM and 10 mM of CS–Phe NCs in 2018 and 2019, respectively. The highest flavonoid content was observed with 5 mM of CS–Phe NCs in both study years. In addition, the anthocyanin content increased with 5 and 10 mM of CS–Phe NCs. PAL activity was found to be the highest with 5 mM of CS–Phe NCs in both study years. In addition, in accordance with the increase in PAL activity, increased total phenolics and anthocyanin, and higher DPPH radical scavenging activity of the grapes were recorded with the treatments compared to the control. As deduced from the findings, the coating substantially influenced the metabolic pathway, and the subsequent alterations induced by the treatments were notably appreciated due to there being no adverse impacts perceived.

Melatonin-Loaded Nanocarriers: New Horizons for Therapeutic Applications

The use of nanosized particles has emerged to facilitate selective applications in medicine. Drug-delivery systems represent novel opportunities to provide stricter, focused, and fine-tuned therapy, enhancing the therapeutic efficacy of chemical agents at the molecular level while reducing their toxic effects. Melatonin (N-acetyl-5-methoxytriptamine) is a small indoleamine secreted essentially by the pineal gland during darkness, but also produced by most cells in a non-circadian manner from which it is not released into the blood. Although the therapeutic promise of melatonin is indisputable, aspects regarding optimal dosage, biotransformation and metabolism, route and time of administration, and targeted therapy remain to be examined for proper treatment results. Recently, prolonged release of melatonin has shown greater efficacy and safety when combined with a nanostructured formulation. This review summarizes the role of melatonin incorporated into different nanocarriers (e.g., lipid-based vesicles, polymeric vesicles, non-ionic surfactant-based vesicles, charge carriers in graphene, electro spun nanofibers, silica-based carriers, metallic and non-metallic nanocomposites) as drug delivery system platforms or multilevel determinations in various in vivo and in vitro experimental conditions. Melatonin incorporated into nanosized materials exhibits superior effectiveness in multiple diseases and pathological processes than does free melatonin; thus, such information has functional significance for clinical intervention.

The Combined and Single Effect of Marjoram Essential Oil, Ascorbic Acid, and Chitosan on Fresh-Cut Lettuce Preservation

Increasing demands by consumers for fresh, nutritional, and convenient food has led to the increase of fresh-cut produce market. Nowadays, there is a turn towards the investigation of natural products (i.e., essential oils, organic acids, and edible coatings) in an effort to lower the usage of chemical synthetic compounds (i.e., chlorine) as postharvest sanitizers. The aim of the present study was to assess the effectiveness of Origanum majorana essential oil (EO), ascorbic acid (AA), chitosan, and their combinations on quality attributes of fresh-cut lettuce stored for six days at 7 °C. When applied, Chitosan+AA resulted to a less acceptable product (visual quality and aroma), while the application of marjoram EO was able to preserve the visual quality of fresh-cut lettuce and at the same time resulted in a pleasant aroma. The application of EO+AA and Chitosan+AA increased total phenolics and antioxidant levels of fresh-cut lettuce on the fourth and sixth day of storage. The EO and EO+AA increased damage index (hydrogen peroxide and lipid peroxidation) of fresh-cut lettuce, while at the same time these treatments decreased the activity of enzymes related with plant tissue browning (i.e., peroxidase activity and polyphenol oxidase). Chitosan decreased total valuable counts and yeasts and molds counts on the sixth day of storage, while EO, AA, EO+Chitosan, and Chitosan+AA decreased yeasts and molds after four days of application. The findings of the present work indicating that the combination of marjoram EO, AA, and chitosan could be considered further as alternative means for fresh-cut produce preservation.

Fabrication of novel self-healing edible coating for fruits preservation and its performance maintenance mechanism

Coating damage destroys the integrity features critical for maintaining the modified atmosphere inside the fruit. In this study, we developed a self-healing edible coating that maintains its barrier properties for extending the shelf life of strawberries. The coating was fabricated via the layer-by-layer assembly of chitosan (CS) and sodium alginate (SA). (SA/CS)₃ formed by three assembly cycles could completely heal the visibly damaged area by treating water. The mechanical properties and the water and oxygen rates of the healed coating were 97%, 63%, and 95%, respectively, of the intact coating. (SA/CS)₃ coating effectively delayed strawberry deterioration. Moreover, the coating reduced the impact of coating damage on strawberries by restoring the coating barrier properties. The present findings have important implications for solving the reduction in freshness caused by coating damage.