Chitosan, a Biopolymer With Triple Action on Postharvest Decay of Fruit and Vegetables: Eliciting, Antimicrobial and Film-Forming Properties

The dual function of calcium ion in fruit edible coating: Regulating polymer internal crosslinking state and improving fruit postharvest quality

The edible coating is proved to be a convenient approach for fruit preservation. Among these published explorations, naturally sourced macromolecules and green crosslinking strategies gain attention. This work centers on edible coatings containing Ca2+ as crosslinker for the first time, delving into crosslinking mechanisms, include alginate, chitosan, Aloe vera gel, gums, etc. Additionally, the crucial functions of Ca2+ in fruit's quality control are also elaborated in-depth, involving cell wall, calmodulin, antioxidant, etc. Through a comprehensive review, it becomes evident that Ca2+ plays a dual role in fruit edible coating. Specifically, Ca2+ constructs a three-dimensional dense network structure with polymers through ionic bonding. Moreover, Ca2+ acts directly with cell wall to maintain fruit firmness and serve as a second messenger to participate secondary physiological metabolism. In brief, coatings containing Ca2+ present remarkable effects in preserving fruit and this work may provide guidance for Ca2+ related fruit preservation coatings.

Physicochemical Evaluation of Coated Ginger during Long-Term Storage: Impact of Chitosan and Beeswax Bilayer Coatings at Different Temperatures

Fresh ginger can spoil quickly owing to a variety of factors, including inappropriate postharvest handling, microbial and enzymatic activities, and chemical reactions during storage. This study evaluated the physicochemical properties of ginger coated with chitosan and beeswax during storage for 6 months at different temperatures (18°C and 25°C). Fresh ginger was treated with chitosan coating (1.5 and 3.5%), followed by beeswax coating (3 and 6%). The coated ginger was wrapped in a plastic net and stored at ambient (25°C) and low temperatures (18°C) for six months. The results confirmed that coating treatment slowed down the changes in physicochemical properties (moisture, phenolic content, and so on) of ginger during storage. Ginger stored at 25°C showed shorter shelf lives than those stored at 18°C. Coating ginger with 3% chitosan followed by 6% beeswax exhibited the best results in maintaining the moisture and phenolic content, reducing weight loss, and increasing total soluble solid (TSS) and cell compartment size for six months of storage. This study provides a promising approach to delaying the spoilage of fresh ginger by applying coating treatments useful for developing handling protocols for fresh ginger during storage and distribution.

Pre- and postharvest chitosan coatings extend the physicochemical and bioactive qualities of minimally processed 'Crimson Seedless' grapes during cold storage

BACKGROUND

Food marketers desire residue-free fresh grapes although grapes have a short postharvest life. This study was performed to determine the influences of pre- and/or postharvest chitosan (Ch) coatings on postharvest quality of minimally processed (stem-detached) organic 'Crimson Seedless' berries. Berries were sorted as: (a) control (untreated berries); (b) preharvest Ch (dipping the clusters on the vine into 1% Ch 10 days before harvest at 20% soluble solid content (SSC)); (c) postharvest Ch (dipping the stem-detached berries into 1% Ch); and (d) pre + postharvest Ch. Berries were stored in 12 × 15 cm rigid polypropylene cups for up to 42 days at 1.0 ± 0.5 °C.

RESULTS

Pre- and/or postharvest Ch coating reduced weight loss during storage. Pre- + postharvest Ch was the best treatment for restricting polygalacturonase (PG) activity, extending the visual quality, color features (L*, C and h°), skin rupture force, biochemical (SSC, titratable acidity, maturity index and pH) and bioactive (total phenol content, antioxidant activity) features. Pre- or postharvest Ch was also significantly effective in maintaining many quality features.

CONCLUSION

Pre- and/or postharvest 1% Ch coatings effectively maintained the quality of minimally processed grape berries of organically produced 'Crimson Seedless' grapes by delaying weight loss and PG activity and keeping the postharvest physical, biochemical and bioactive features for 42-day cold storage at 1.0 ± 0.5 °C. The combined use of pre- and postharvest Ch found to be more effective than single treatment. Thus, pre- + postharvest 1% Ch coating could be recommended as an ecofriendly sustainable methodology for extending the postharvest quality of minimally processed fresh grapes. © 2024 The Author(s). Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Influence of chitin nanofibers and gallic acid on physical-chemical and biological performances of chitosan-based films

In this work, chitosan films loaded with gallic acid and different content of chitin nanofibers were prepared and subjected to different characterization techniques. The results showed that the inclusion of gallic acid to chitosan films caused moderate decrease in water vapor permeability (by 29 %) and increased tensile strength of films (by 169 %) in comparison to the neat chitosan films. Furthermore, it was found that the addition of chitin nanofibers up to 30 % into chitosan/gallic acid films additionally improved tensile strength (by 474 %) and reduced plasticity of films (by 171 %), when compared to the chitosan/gallic acid films. Increased concentration of chitin nanofibers in films reduced the overall water vapor permeability of films by 51 %. In addition, gallic acid and chitin nanofibers had synergic effect on high chitosan film's antioxidant and antifungal activity toward Botrytis cinerea (both above 95 %). Finally, chitosan/gallic acid/chitin nanofibers films reduced decay incidence of strawberries, increased total soluble solid content, and promoted high production of some polyphenols during cold storage, in comparison to the control chitosan films and uncoated strawberry samples. Hence, these results suggest that chitosan/gallic acid/chitin nanofibers can present eco-sustainable approach for preservation of strawberries, giving them additional nutritional value.

Increasing vineyard sustainability: innovating a targeted chitosan-derived biocontrol solution to induce grapevine resistance against downy and powdery mildews

The European Green Deal aims to reduce the pesticide use, notably by developing biocontrol products to protect crops from diseases. Indeed, the use of significant amounts of chemicals negatively impact the environment such as soil microbial biodiversity or groundwater quality, and human health. Grapevine (Vitis vinifera) was selected as one of the first targeted crop due to its economic importance and its dependence on fungicides to control the main damaging diseases worldwide: grey mold, downy and powdery mildews. Chitosan, a biopolymer extracted from crustacean exoskeletons, has been used as a biocontrol agent in many plant species, including grapevine, against a variety of cryptogamic diseases such as downy mildew (Plasmopara viticola), powdery mildew (Erysiphe necator) and grey mold (Botrytis cinerea). However, the precise molecular mechanisms underlying its mode of action remain unclear: is it a direct biopesticide effect or an indirect elicitation activity, or both? In this study, we investigated six chitosans with diverse degrees of polymerization (DP) ranging from low to high DP (12, 25, 33, 44, 100, and 470). We scrutinized their biological activities by evaluating both their antifungal properties and their abilities to induce grapevine immune responses. To investigate their elicitor activity, we analyzed their ability to induce MAPKs phosphorylation, the activation of defense genes and metabolite changes in grapevine. Our results indicate that the chitosans with a low DP are more effective in inducing grapevine defenses and possess the strongest biopesticide effect against B. cinerea and P. viticola. We identified chitosan with DP12 as the most efficient resistance inducer. Then, chitosan DP12 has been tested against downy and powdery mildews in the vineyard trials performed during the last three years. Results obtained indicated that a chitosan-based biocontrol product could be sufficiently efficient when the amount of pathogen inoculum is quite low and could be combined with only two fungicide treatments during whole season programs to obtain a good protection efficiency. On the whole, a chitosan-based biocontrol product could become an interesting alternative to meet the chemicals reduction targeted in sustainable viticulture.

Chitosan inhibits Penicillium expansum possibly by binding to DNA and triggering apoptosis

Chitosan is a natural polysaccharide that is abundant, biocompatible and exhibits effective antifungal activity against various pathogenic fungi. However, the potential intracellular targets of chitosan in pathogenic fungi and the way of activity of chitosan are far from well known. The present work demonstrated that chitosan could inhibit Penicillium expansum, the principal causal agent of postharvest blue mold decay on apple fruits, by binding to DNA and triggering apoptosis. UV-visible spectroscopy, fluorescence spectroscopy and electrophoretic mobility assay proved the interaction between chitosan and DNA, while atomic force microscope (AFM) observation revealed the binding morphology of chitosan to DNA. Chitosan could inhibit in vitro DNA replication, and cell cycle analysis employing flow cytometry demonstrated that cell cycle was retarded by chitosan treatment. Furthermore, the reactive oxygen species (ROS) assay and membrane potential analysis showed that apoptosis was induced in P. expansum cells after exposure to chitosan. In conclusion, our results confirmed that chitosan interacts with DNA and induces apoptosis. These findings are expected to provide a feasible theoretical basis and practical direction for the promoting and implementing of chitosan in plant protection and further illuminate the possible antifungal mechanisms of chitosan against fungal pathogens.

Genetic and molecular landscapes of the generalist phytopathogen Botrytis cinerea

Botrytis cinerea Pers. Fr. (teleomorph: Botryotinia fuckeliana) is a necrotrophic fungal pathogen that attacks a wide range of plants. This updated pathogen profile explores the extensive genetic diversity of B. cinerea, highlights the progress in genome sequencing, and provides current knowledge of genetic and molecular mechanisms employed by the fungus to attack its hosts. In addition, we also discuss recent innovative strategies to combat B. cinerea.

TAXONOMY

Kingdom: Fungi, phylum: Ascomycota, subphylum: Pezizomycotina, class: Leotiomycetes, order: Helotiales, family: Sclerotiniaceae, genus: Botrytis, species: cinerea.

HOST RANGE

B. cinerea infects almost all of the plant groups (angiosperms, gymnosperms, pteridophytes, and bryophytes). To date, 1606 plant species have been identified as hosts of B. cinerea.

GENETIC DIVERSITY

This polyphagous necrotroph has extensive genetic diversity at all population levels shaped by climate, geography, and plant host variation.

PATHOGENICITY

Genetic architecture of virulence and host specificity is polygenic using multiple weapons to target hosts, including secretory proteins, complex signal transduction pathways, metabolites, and mobile small RNA.

DISEASE CONTROL STRATEGIES

Efforts to control B. cinerea, being a high-diversity generalist pathogen, are complicated. However, integrated disease management strategies that combine cultural practices, chemical and biological controls, and the use of appropriate crop varieties will lessen yield losses. Recently, studies conducted worldwide have explored the potential of small RNA as an efficient and environmentally friendly approach for combating grey mould. However, additional research is necessary, especially on risk assessment and regulatory frameworks, to fully harness the potential of this technology.

Advancements in coating technologies: Unveiling the potential of chitosan for the preservation of fruits and vegetables

Post-harvest losses of fruits and vegetables pose a significant challenge to the agriculture industry worldwide. To address this issue, researchers have turned to natural and eco-friendly solutions such as chitosan coatings. Chitosan, a biopolymer derived from chitin, has gained considerable attention due to its unique properties such as non-toxicity, biodegradability, biocompatibility and potential applications in post-harvest preservation. This review article provides an in-depth analysis of the current state of research on chitosan coatings for the preservation of fruits and vegetables. Moreover, it highlights the advantages of using chitosan coatings, including its antimicrobial, antifungal, and antioxidant properties, as well as its ability to enhance shelf-life and maintain the quality attributes of fresh product. Furthermore, the review discusses the mechanisms by which chitosan interacts with fruits and vegetables, elucidating its antimicrobial activity, modified gas permeability, enhanced physical barrier and induction of host defense responses. It also examines the factors influencing the effectiveness of chitosan coatings, such as concentration, molecular weight, deacetylation degree, pH, temperature, and application methods.

Layer by layer application of chitosan and carboxymethyl cellulose coatings delays ripening of mango fruit by suppressing cell wall polysaccharides disassembly

Mango is a climacteric fruit that ripens quickly after harvest due to its climacteric nature. Edible coatings have been reported to delay the ripening of various harvested fruit. The efficacy of the applied edible coatings could be improved by using in combination as a layer-by-layer (LBL) approach. So, the influence of LBL application of chitosan (CH) and carboxymethyl cellulose (CMC) was studied on mangoes during postharvest storage at 15 °C for 20 days. Mangoes were coated with monolayers of CH (1 % w/v) and CMC (1 % w/v) as well as LBL application of CH and CMC and were compared with control. The treatment of mangoes with CH and CMC-based LBL treatment resulted in lower decay percentage and weight loss along with higher total chlorophyll pigments and suppressed total carotenoid accumulation. The LBL application of CH and CMC showed lower activity of chlorophyll degrading such as chlorophyllase (CPS), pheophytinase (Phe), Mg-dechalatase (MGD) and chlorophyll degrading peroxidase (Chl-POD) enzymes as well as reduced changes in b*, a* and L* along with a suppressed increase in ethylene (EP) and CO2 production (CPR) rates having higher antioxidant such as catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD) and superoxide dismutase (SOD) enzymes activity. In addition, mangoes coated with LBL treatment of CH and CMC exhibited lower water-soluble pectin (WSP) and higher protopectin (PP) having higher concentrations of chelate soluble (CSP) and sodium carbonate-soluble pectin (SCP). Similarly, LBL-coated mangoes showed significantly higher hemicellulose (HCLS) and cellulose (CLS) contents in contrast with control. It was observed that mangoes coated with CH and CMC-based LBL coating exhibited higher flesh firmness and showed suppressed cellulase (CS), pectin methylesterase (PME), polygalacturonase (PG) and β-galactosidase (β-Gal) enzymes activity. The concentrations of total soluble solids and ripening index were markedly lower and titratable acidity was higher in the LBL-based coating treatment in comparison with control. In conclusion, LBL treatment based on CH and CMC coatings could be used for the delay of ripening and softening of harvested mangoes.

Preparation, physicochemical and biological evaluation of chitosan Pleurotus ostreatus polysaccharides active films for food packaging

The aim of this study was to create CS-POP composite films by blending Pleurotus ostreatus stalk polysaccharides (POP) and chitosan (CS). The effects of adding different concentrations (0 %, 0.25 %, 0.5 %, 0.75 %, and 1 %) of POP on the mechanical, barrier, and optical properties of the CS films were investigated. When the POP content is at 0.5 %, the tensile strength of the composite film reaches its maximum value at 13.691 MPa, showing a significant improvement compared to the tensile strength of the pure CS film. The structure of the CS and CS-POP composite films was characterized by FT-IR spectroscopy, XRD, TGA and SEM. The results indicate that due to the interaction between the two types of CS and POP, the formation of Schiff base, and the intermolecular hydrogen bonds between CS and POP, the addition of POP to CS films can result in a smoother and more stable crystalline structure in the composite film. The CS-POP composite films exhibited enhanced antioxidant and antibacterial activity compared to the CS films alone, with the highest DPPH scavenging activity of 72.43 %. The composite films also showed significant inhibitory effects on the growth of E. coli.

6-deoxy-6-amino chitosan: a preventative treatment in the tomato/Botrytis cinerea pathosystem

6-deoxy-6-amino chitosan (aminochitosan) is a water-soluble chitosan derivative with an additional amine group at the C-6 position. This modification has improved aqueous solubility, in vitro antifungal activity and is hypothesized to have enhanced in vivo antifungal activity compared to native chitosan. Gray mold disease in tomatoes is caused by the fungus, Botrytis cinerea, and poses a severe threat both pre- and post-harvest. To investigate the optimal concentration of aminochitosan and its lower molecular weight fractions for antifungal and priming properties in the tomato/B. cinerea pathosystem, different concentrations of aminochitosan were tested in vitro on B. cinerea growth and sporulation and in vivo as a foliar pre-treatment in tomato leaves. The leaves were monitored for photosynthetic changes using multispectral imaging and hydrogen peroxide accumulation using DAB. Despite batch-to-batch variations in aminochitosan, it displayed significantly greater inhibition of B. cinerea in vitro than native chitosan at a minimum concentration of 1 mg/mL. A concentration-dependent increase in the in vitro antifungal activities was observed for radial growth, sporulation, and germination with maximum in vitro inhibition for all the biopolymer batches and lower MW fractions at 2.5 and 5 mg/mL, respectively. However, the inhibition threshold for aminochitosan was identified as 1 mg/mL for spores germinating in vivo, compared to the 2.5 mg/mL threshold in vitro. The pre-treatment of leaves displayed efficacy in priming direct and systemic resistance to B. cinerea infection at 4, 6 and 30 days post-inoculation by maintaining elevated Fv/Fm activity and chlorophyll content due to a stronger and more rapid elicitation of the defense systems at earlier time points. Moreover, these defense systems appear to be ROS-independent at higher concentrations (1 and 2.5 mg/mL). In addition, aminochitosan accumulates in the cell membrane and therefore acts to increase the membrane permeability of cells after foliar spray. These observations corroborate the notion that aminochitosan biopolymers can exert their effects through both direct mechanisms of action and indirect immunostimulatory mechanisms. The contrast between in vitro and in vivo efficacy highlights the bimodal mechanisms of action of aminochitosan and the advantageous role of primed plant defense systems.

Eco-sustainable coatings based on chitosan, pectin, and lemon essential oil nanoemulsion and their effect on strawberry preservation

Films and coatings manufactured with bio-based renewable materials, such as biopolymers and essential oils, could be a sustainable and eco-friendly alternative for protecting and preserving agricultural products. In this work, we developed films and coatings from pectin and chitosan to protect strawberries (Fragaria x ananassa Duch.) from spoilage and microbial contamination. We developed three coatings containing equal amounts of glycerol and Sicilian lemon essential oil (LEO) nanoemulsion. We identified seventeen chemicals from LEO by GC-MS chromatogram, including d-limonene, α-Pinene, β-Pinene, and γ-Terpinene. The pectin and chitosan coatings were further characterized using different physicochemical, mechanical, and biological methods. The films demonstrated satisfactory results in strength and elongation at the perforation as fruit packaging. In addition, the coatings did not influence the weight and firmness of the strawberry pulps. We observed that 100 % essential oil was released in 1440 min resulting from the erosion process. Also, the oil preserved the chemical stability of the films. Antioxidant activity (AA), measured by Electron Paramagnetic Resonance (EPR), showed that the coatings loaded with 2 % LEO nanoemulsion (PC + oil) showed that almost 50 % of AA from LEO nanoemulsion was preserved. The chitosan and the pectin-chitosan coatings (PC + oil) inhibited filamentous fungi and yeast contaminations in strawberries for at least 14 days, showing a relationship between the AA and antimicrobial results.

Application of a Chitosan-Cinnamon Essential Oil Composite Coating in Inhibiting Postharvest Apple Diseases

The purpose of this study was to explore the film-forming properties of cinnamon essential oil (CEO) and chitosan (CS) and the effect of their composite coating on postharvest apple diseases. The results demonstrated that the composite coating exhibits favorable film-forming properties at CEO concentrations below 4% (v/v). The effectiveness of the composite coating in disease control can be attributed to two factors: the direct inhibitory activity of CEO against pathogens in vitro and the induced resistance triggered by CS on the fruits. Importantly, the incorporation of CEO did not interfere with the induction of resistance by CS in harvested apples. However, it is noteworthy that the inhibitory effect of the CS-CEO composite coating on apple diseases diminished over time. Therefore, a key aspect of enhancing the preservation ability of fruits is improving the controlled release properties of CEO within CS coatings. This will enable a sustained and prolonged antimicrobial effect, thereby bolstering the fruit preservation capabilities of the composite coatings.

Induced Resistance in Fruit and Vegetables: A Host Physiological Response Limiting Postharvest Disease Development

Harvested fruit and vegetables are perishable, subject to desiccation, show increased respiration during ripening, and are colonized by postharvest fungal pathogens. Induced resistance is a strategy to control diseases by eliciting biochemical processes in fruits and vegetables. This is accomplished by modulating the progress of ripening and senescence, which maintains the produce in a state of heightened resistance to decay-causing fungi. Utilization of induced resistance to protect produce has been improved by scientific tools that better characterize physiological changes in plants. Induced resistance slows the decline of innate immunity after harvest and increases the production of defensive responses that directly inhibit plant pathogens. This increase in defense response in fruits and vegetables contributes to higher amounts of phenols and antioxidant compounds, improving both the quality and appearance of the produce. This review summarizes mechanisms and treatments that induce resistance in harvested fruits and vegetables to suppress fungal colonization. Moreover, it highlights the importance of host maturity and stage of ripening as limiting conditions for the improved expression of induced-resistance processes.

Are Basic Substances a Key to Sustainable Pest and Disease Management in Agriculture? An Open Field Perspective

Pathogens and pests constantly challenge food security and safety worldwide. The use of plant protection products to manage them raises concerns related to human health, the environment, and economic costs. Basic substances are active, non-toxic compounds that are not predominantly used as plant protection products but hold potential in crop protection. Basic substances' attention is rising due to their safety and cost-effectiveness. However, data on their protection levels in crop protection strategies are lacking. In this review, we critically analyzed the literature concerning the field application of known and potential basic substances for managing diseases and pests, investigating their efficacy and potential integration into plant protection programs. Case studies related to grapevine, potato, and fruit protection from pre- and post-harvest diseases and pests were considered. In specific cases, basic substances and chitosan in particular, could complement or even substitute plant protection products, either chemicals or biologicals, but their efficacy varied greatly according to various factors, including the origin of the substance, the crop, the pathogen or pest, and the timing and method of application. Therefore, a careful evaluation of the field application is needed to promote the successful use of basic substances in sustainable pest management strategies in specific contexts.

Synthesis, characterization, and biological evaluation of new chitosan derivative bearing diphenyl pyrazole moiety

This work reports the synthesis of a new pyrazole derivative by reacting 5-amino-1,3-diphenyl pyrazole with succinic anhydride and bearing the product chemically on the chitosan chains via amide linkage to achieve a new chitosan derivative (DPPS-CH). The prepared chitosan derivative was analyzed by IR, NMR, elemental analysis, XRD, TGA-DTG, and SEM. As compared with chitosan, DPPS-CH showed an amorphous and porous structure. Coats-Redfern results showed that the thermal activation energy for the first decomposition of DPPS-CH is 43.72 KJ mol^-1 lower than that required for chitosan (88.32 KJ mol^-1), indicating the accelerating effect of DPPS on the thermal decomposition of DPPS-CH. The DPPS-CH manifested a powerful wide spectrum antimicrobial potential against pathogenic gram-positive and gram-negative bacteria and Candida albicans at minute concentrations (MIC = 50 μg mL^-1) compared to chitosan (MIC = 100 μg mL^-1). The MTT assay proved the toxic properties of DPPS-CH against a cancer cell line (MCF-7) at a minute concentration (IC50 = 15.14 μg mL^-1) while affecting normal cells (WI-38) at seven times this concentration (IC50 = 107.8 μg mL^-1). According to the current findings, the chitosan derivative developed in this work appears to be a promising material for use in biological domains.

Protective Properties of Copper-Loaded Chitosan Nanoparticles against Soybean Pathogens Pseudomonas savastanoi pv. glycinea and Curtobacterium flaccumfaciens pv. flaccumfaciens

Soybeans are a valuable food product, containing 40% protein and a large percentage of unsaturated fatty acids ranging from 17 to 23%. Pseudomonas savastanoi pv. glycinea (Psg) and Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff) are harmful bacterial pathogens of soybean. The bacterial resistance of soybean pathogens to existing pesticides and environmental concerns requires new approaches to control bacterial diseases. Chitosan is a biodegradable, biocompatible and low-toxicity biopolymer with antimicrobial activity that is promising for use in agriculture. In this work, a chitosan hydrolysate and its nanoparticles with copper were obtained and characterized. The antimicrobial activity of the samples against Psg and Cff was studied using the agar diffusion method, and the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined. The samples of chitosan and copper-loaded chitosan nanoparticles (Cu²⁺ChiNPs) significantly inhibited bacterial growth and were not phytotoxic at the concentrations of the MIC and MBC values. The protective properties of chitosan hydrolysate and copper-loaded chitosan nanoparticles against soybean bacterial diseases were tested on plants in an artificial infection. It was demonstrated that the Cu²⁺ChiNPs were the most effective against Psg and Cff. Treatment of pre-infected leaves and seeds demonstrated that the biological efficiencies of (Cu²⁺ChiNPs) were 71% and 51% for Psg and Cff, respectively. Copper-loaded chitosan nanoparticles are promising as an alternative treatment for bacterial blight and bacterial tan spot and wilt in soybean.

Assessing Copper-Alternative Products for the Control of Pre- and Postharvest Citrus Anthracnose

Citrus production is worldwide threatened by Colletotrichum spp., causal agents of pre- and postharvest anthracnose. The recent limitation on the use of copper-based antimicrobials, due to its demonstrated noxious effect on the environment, makes the control of this pathogen difficult. Thus, alternative products able to reduce/phase out copper in organic citrus farming are needed. In this study, the efficacy of 11 commercial alternative products were evaluated in vitro, in growth chamber, in open field and in postharvest environments. In vitro, mineral fertilizers, basic substances, essential oils, plant defense stimulators and biological control agents were able to inhibit the mycelial growth with variable efficacy. On artificially infected citrus fruit, almost all tested products significantly reduced disease incidence and severity, but with lower efficacy than copper. The efficacy of mineral fertilizers-based Kiram and Vitibiosap 458 Plus, citrus essential oil-based Prev-Am Plus and chitosan-based Biorend was confirmed in open field trials, in naturally infected citrus fruits. In these trials Biorend was the best alternative product, significantly reducing disease incidence (71% DI reduction) with better results than copper (47.5%). Field treatments reduced the incidence and severity of the disease in postharvest conditions, especially in fruits field-treated three times. Overall, selected products tested in open field can represent a good alternative to copper compounds in the view of future limitation of its use.

Chitosan Based Materials in Cosmetic Applications: A Review

This review provides a report on the properties and recent advances in the application of chitosan and chitosan-based materials in cosmetics. Chitosan is a polysaccharide that can be obtained from chitin via the deacetylation process. Chitin most commonly is extracted from cell walls in fungi and the exoskeletons of arthropods, such as crustaceans and insects. Chitosan has attracted significant academic interest, as well as the attention of the cosmetic industry, due to its interesting properties, which include being a natural humectant and moisturizer for the skin and a rheology modifier. This review paper covers the structure of chitosan, the sources of chitosan used in the cosmetic industry, and the role played by this polysaccharide in cosmetics. Future aspects regarding applications of chitosan-based materials in cosmetics are also mentioned.

Preharvest Application of Commercial Products Based on Chitosan, Phosphoric Acid Plus Micronutrients, and Orange Essential Oil on Postharvest Quality and Gray Mold Infections of Strawberry

Strawberry is a perishable fruit with a limited shelf life after harvest due to deterioration of quality and the development of gray mold, Rhizopus rot and other minor diseases. In this study, the effectiveness of commercial compounds based on chitosan, phosphoric acid plus micronutrients, and sweet orange essential oil (EO) in reducing decay and optimizing the quality of strawberries was analyzed. The plant canopy of a greenhouse crop was sprayed once and strawberry fruit were harvested three days later. Gray mold infections were evaluated after chilled storage for seven days at 4 ± 0.5 °C followed by five days shelf life. The qualitative parameters were recorded at harvest (initial day) and after three days of storage at room temperature (RT, 20 °C) or after cold storage and shelf life (CS, 4 °C). The application of sweet orange EO increased the antioxidant and flavonoid content at harvest, while a decrease was reported following three days of storage at RT. At the same time, increased ethylene production and weight loss were observed during CS three days after harvesting. Chitosan treatment maintained the harvest fruit quality and was effective in the control of postharvest decay. Our results suggest that the investigated natural compounds could improve strawberry quality after harvest. Since chitosan performed best in terms of maintaining quality and reducing postharvest decay, it could be considered as a good substitute for chemical-synthetic fungicides for the preservation of strawberry postharvest gray mold.

Chitosan and other edible coatings to extend shelf life, manage postharvest decay, and reduce loss and waste of fresh fruits and vegetables

Fresh fruits and vegetables contain high percentage of water and continue metabolic activity after being harvested, resulting in ripening, increased sensitivity to decay-causing fungi, and consequent loss and waste. Edible coatings are prepared from naturally occurring renewable sources and can contribute to reducing waste, respecting environment, and consumer health. Chitosan and other edible coatings form a thin layer surrounding fresh produce that acts as a protective agent, extending shelf life, and have the potential to control their ripening process and maintain nutritional properties of the coated product. This review discusses recent research on the application of chitosan and other edible coatings to prevent fungal decay, keep the quality, and reduce fresh product waste.

Influence on grape aromatic compounds of natural fungicides used for the control of downy mildew

BACKGROUND

The grape volatile fraction determines to a great extent its aroma, which is one of the most important characteristics influencing wine quality and consumer preferences. Grapevine downy mildew (GDM) is one of the most important and devastating diseases of grapevines worldwide. In this study, the impact on the volatile composition of cv. Verdicchio grapes of classical copper formulations, was compared to that of alternative products. Thus, 11 treatments were foliar applied throughout one grapevine cycle.

RESULTS

Most of the volatile compounds present in the grapes were not affected by the treatments used in order to prevent GDM. In the case of the total C₁₃ norisoprenoids, some differences were found between grapes untreated control and those applied with the grapefruit seed extract. Moreover, the content of alcohols was smaller in grapes from Bordeaux mixture treatment and higher in the samples from chitosan application.

CONCLUSION

Therefore, from the qualitative point of view of the berry, treatment with tested products alternative to copper is recommended, which minimize the environmental and health problems that this heavy metal brings to the soil and in the winery, since it means that their applications did not affect the grape aroma. © 2022 Society of Chemical Industry.

Copper Monitoring in Vineyard Soils of Central Italy Subjected to Three Antifungal Treatments, and Effects of Sub-Lethal Copper Doses on the Earthworm Eisenia fetida

The extensive employment of copper-based fungicides has increased copper concentration in vineyard soils. The present study's objectives were to monitor copper concentration in two vineyard soils during two cropping seasons and study the ecotoxicological effects on the earthworm Eisenia fetida. Total, soluble, and bioavailable copper fractions were measured at the end of two cropping seasons and different depths in two vineyards of central Italy, characterised by three anticryptogamic control methods: copper compounds, chitosan, and combined treatments of them. A laboratory experiment to assess the effects on Eisenia fetida was conducted with soil samples collected in the vineyards with a mean copper concentration of 60 mg/kg and two higher concentrations of 90 and 150 mg/kg. Results showed low levels of total copper concentration in the first 20 cm of soils, regardless of antifungal treatment, highlighting prudent management of the vineyards under study, but the soluble fractions showed a significant increase in all samples during the two cropping seasons. At the dose of 150 mg/kg, earthworms suffer during the first two days, showing weight loss and DNA damage, but they are able to recover until day 28, showing no permanent harm at this copper concentration in soil.

Basic Substances, a Sustainable Tool to Complement and Eventually Replace Synthetic Pesticides in the Management of Pre and Postharvest Diseases: Reviewed Instructions for Users

Synthetic pesticides are widely used to protect crops from pathogens and pests, especially for fruits and vegetables, and this may lead to the presence of residues on fresh produce. Improving the sustainability of agriculture and, at the same time, reducing the adverse effects of synthetic pesticides on human health requires effective alternatives that improve the productivity while maintaining the food quality and safety. Moreover, retailers increasingly request fresh produce with the amounts of pesticides largely below the official maximum residue levels. Basic substances are relatively novel compounds that can be used in plant protection without neurotoxic or immune-toxic effects and are still poorly known by phytosanitary consultants (plant doctors), researchers, growers, consumers, and decision makers. The focus of this review is to provide updated information about 24 basic substances currently approved in the EU and to summarize in a single document their properties and instructions for users. Most of these substances have a fungicidal activity (calcium hydroxide, chitosan, chitosan hydrochloride, Equisetum arvense L., hydrogen peroxide, lecithins, cow milk, mustard seed powder, Salix spp., sunflower oil, sodium chloride, sodium hydrogen carbonate, Urtica spp., vinegar, and whey). Considering the increasing requests from consumers of fruits and vegetables for high quality with no or a reduced amount of pesticide residues, basic substances can complement and, at times, replace the application of synthetic pesticides with benefits for users and for consumers. Large-scale trials are important to design the best dosage and strategies for the application of basic substances against pathogens and pests in different growing environments and contexts.

Assessing the Use of Aloe vera Gel Alone and in Combination with Lemongrass Essential Oil as a Coating Material for Strawberry Fruits: HPLC and EDX Analyses

Strawberry is a non-climacteric fruit but exhibits a limited postharvest life due to rapid softening and decay. A strawberry coating that is natural and safe for human consumption can be used to improve the appearance and safeguard the fruits. In this study, 20% and 40% Aloe vera gel alone or in combination with 1% lemongrass essential oil (EO) was used as an edible coating for strawberries. After application of all the treatments, the strawberry fruits were stored at a temperature of 5 ± 1 °C at a relative humidity (RH) of 90%–95% for up to 16 days and all the parameters were analyzed and compared to control (uncoated fruits). The results show that A. vera gel alone or with lemongrass EO reduced the deterioration and increased the shelf life of the fruit. Treatment with A. vera gel and lemongrass EO decreased acidity and total anthocyanins and maintained fruit firmness. Treatment with A. vera gel 40% + lemongrass EO 1% led to the lowest weight loss, retained firmness and acidity, but increased the total soluble solids and total anthocyanins compared to uncoated fruits during storage of up to 16 days. The phenolic compounds of A. vera gel were analyzed by HPLC, and the most abundant compounds were found to be caffeic (30.77 mg/mL), coumaric (22.4 mg/mL), syringic (15.12 mg/mL), sinapic (14.05 mg/mL), ferulic (8.22 mg/mL), and cinnamic acids (7.14 mg/mL). Lemongrass EO was analyzed by GC–MS, and the most abundant compounds were identified as α-citral (neral) (40.10%) ꞵ-citral (geranial) (30.71%), γ-dodecalactone (10.24%), isoneral (6.67%), neryl acetal (5.64%), and linalool (1.77%). When the fruits were treated with 20% or 40% A. vera gel along with 1% lemongrass, their total phenolic content was maintained during the storage period (from 4 to 8 days). The antioxidant activity was relatively stable during the 8 days of cold storage of the fruits coated with A. vera gel combined with lemongrass EO because the activity of both 20% and 40% gel was greater than that for the other treatments after 12 days of storage in both experiments. Moreover, all the treatments resulted in lower numbers of total microbes at the end of the storage period compared with the control treatment. This study indicates that the use of Aloe vera gel with lemongrass EO as an edible coating considerably enhances the productivity of strawberry fruits and the treatment could be used on a commercial scale.

Influence of Marine Yeast Debaryomyces hansenii on Antifungal and Physicochemical Properties of Chitosan-Based Films

Chitosan-based film with and without antagonistic yeast was prepared and its effect against Penicillium italicum was evaluated. The biocompatibility of yeast cells in the developed films was assessed in terms of population dynamics. Furthermore, the impact on physicochemical properties of the prepared films with and without yeast cells incorporated were evaluated in terms of thickness, mechanical properties, color and opacity. Chitosan films with the antagonistic yeast entrapped exhibited strong antifungal activity by inhibiting the mycelial development (55%), germination (45%) and reducing the sporulation process (87%). Chitosan matrix at 0.5% and 1.0% was maintained over 9 days of cell viability. However, at 1.5% of chitosan the population dynamics was strongly affected. The addition of yeast cells only impacted color values such as a*, b*, chroma and hue angle when 1.0% of chitosan concentration was used. Conversely, luminosity was not affected in the presence of yeast cells as well as the opacity. Besides, the addition of antagonistic yeast improved the mechanical resistance of the films. The addition of D. hansenii in chitosan films improve their efficacy for controlling P. italicum, and besides showed desirable characteristics for future use as packaging for citrus products.

Synthesis, characterization and application of chitosan conjugated heterocyclic compounds

Derivatives of formyl pyrazole were synthesized by the reaction of acetophenone, 4-methyl acetophenone, 3-acetyl furan, 3-acetyl thiophen and phenyl hydrazine derivatives. The product was treated with Vilsmeier reagent producing different formyl pyrazole derivatives which were characterized by FT-IR, 1HNMR, Elemental analysis and Mass spectroscopy. The formyl pyrazole derivatives were reacted with chitosan to produce chitosan/ pyrazole Schiff base. These Schiff bases were characterized by FT-IR and TGA.The antimicrobial activity of chitosan/ pyrazol Schiff base (CSB) was evaluated against Gram-positive bacteria (Staphylococcus aureus and Bacillus cereus), gram negative bacterium (Escherichia coli) and fungus (Aspergillus niger). Results indicated agood inhibitory activity for CSB-14 when tested against B.cereus that gave inhibition zone of 7.5 ± 0.6 (mm), however CSB-18 gave a pronounced inhibitory activity against S. aureus and recorded 25 ± 2.0 (mm). All synthesized derivatives have no inhibitory activity against Gram negative E. coli. CSB-14, and CSB-15 exhibited inhibitory activity against tested A. niger that was used as a fungal model which gave 19 ± 0.9 and 18 ± 1.0 inhibition zone (mm) respectively. Thus, these results showed that, functionalization of chitosan with the hetero-cyclic compounds created biological activities of the synthesized derivatives; hence the synthesized pyrazole derivatives have not recorded any inhibitory activity before its immobilization onto chitosan.

Propagation and Postharvest of Fruit Crops

In fruit crops, plant propagation plays an important role as it allows the number of plants produced to be rapidly multiplied while retaining desirable characteristics from the mother plants and shortening the bearing age of plants [...]

Edible Coatings from Opuntia ficus-indica Cladodes Alongside Chitosan on Quality and Antioxidants in Cherries during Storage

The aim of this work was to investigate the effect of edible coatings (ECs) prepared from extracts of Opuntia ficus-indica (OFI) cladodes in comparison with a commercial chitosan formulation on the quality of ‘Regina’ cherries packaged in macro-perforated bags and stored for up to 28 d (1 °C, 90% RH). The coating concentrations were 25% and 50% aqueous OFI extract (approximately 0.59 and 1.18% dry matter, respectively), 1% OFI alcohol insoluble polysaccharide and 1% chitosan. The variables evaluated included weight loss (WL), respiration rates (RR), peel color, firmness, microbial decay, total antioxidants (phenolics, flavonoids, anthocyanins, antioxidant capacity), individual phenolic compounds (anthocyanins, hydroxycinnamic acids, flavan-3-O-ols), and pedicel removal force. The main results show that all coatings reduced WL and RR similarly, enhanced firmness throughout storage and antioxidants after 28 d of storage compared to the controls. Among treatments, chitosan resulted in much higher peel glossiness and firmness in comparison to OFI extracts. On day 28, all ECs resulted in higher antioxidants than controls, OFI extracts resulted in higher cyaniding-3-O-rutinoside than chitosan, while 50% OFI treatment resulted in the highest catechin concentration. Therefore, OFI extracts are promising ECs for cherry storage since they exhibited no negative effect, improved quality and extended storage life by one week compared to the controls.

Single and Combined Effect of Mild-Heat Treatment and Alginate Coatings on Quality Preservation of Minimally Processed Bunching Green Onions

Bunching green onion is an Allium species that has been widely used in food flavorings and seasonings. This vegetable experiences a rapid loss of quality during storage due to physiological changes and microbial spoilage. In the current work, the single and combined effect of mild-heat treatment (55 °C for 60 s) and alginate edible coatings on the quality preservation of minimally processed bunching green onions was studied. Control and treated samples were stored at 4 °C for 15 days and examined periodically in terms of their respiration rate, weight loss, pH, soluble solids content, firmness, total polyphenol content, antioxidant activity, microbial count, decay ratio, and overall visual quality. The results showed that the combination of mild heat and alginate edible coatings was the most effective approach to slow down the respiration rate and the incidence of decay in the minimally processed bunching green onions. In addition, the treatments with alginate coating alone or combined with mild-heat treatment showed the best performance for maintaining the overall visual quality of the products during the storage.

Overexpression and Biochemical Properties of a GH46 Chitosanase From Marine Streptomyces hygroscopicus R1 Suitable for Chitosan Oligosaccharides Preparation

Due to the various biological activities of chitosan oligosaccharides (COSs), they have great potential value for use in many areas. Chitosanase plays an important role in enzymatic preparation of COSs. Herein, a gene encoding a chitosanase (ShCsn46) from marine Streptomyces hygroscopicus R1 was cloned and the sequences encoding ShCsn46 without signal peptide were optimized based on the codon usage of Pichia pastoris (P. pastoris). In addition, the optimized gene was ligated to pPICZαA and transformed to P. pastoris X33. After screening, a recombinant strain named X33-Sh33 with the highest activity was isolated from 96 recombinant colonies. The maximum activity and total protein concentration of the recombinant strain ShCsn46 were 2250 U/ml and 3.98 g/l, respectively. The optimal pH and temperature of purified ShCsn46 were 5.5 and 55°C, respectively. Meanwhile, ShCsn46 was stable from pH 5.0 to 10.0 and 40 to 55°C, respectively. The purified ShCsn46 was activated by Mn²⁺ and inhibited by Cu²⁺, Fe²⁺, and Al³⁺. In addition, substrate specificity of the purified ShCsn46 showed highest activity toward colloidal chitosan with 95% degree of deacetylation. Furthermore, the purified ShCsn46 exhibited high efficiency to hydrolyze 4% colloidal chitosan to prepare COSs. COSs with degree of polymerization of 2–6, 2–5, and 2–4 were controllably produced by adjusting the reaction time. This study provides an excellent chitosanase for the controllable preparation of COSs with a desirable degree of polymerization.

Chitosan nanoemulsion: Gleam into the futuristic approach for preserving the quality of muscle foods

Trend for consumption of healthy meat without synthetic additives is blooming globally and has attracted the interest of consumers and research sphere to look for enhancement of quality and safety of food. Chitosan is multi-functional marine biopolymer with several befitting properties such as non-toxicity, ease of modification, antimicrobial activity, biodegradability and bio-compatibility, making it suitable for use in meat based food systems, which are highly prone to putrescence due to availability of high level protein, micronutrients and moisture. Bioactive components from plant extracts on account of their natural lineage are exquisite determinants for meat preservation in association with chitosan to replace synthetic molecules, which are considered to evince toxicological effects. Nanoemulsions are viable systems for integrating a myriad of active constituents framed by microfluidization, high-pressure homogenization, ultra-sonication, phase inversion (PIC and PIT) and spontaneous-emulsification with benefits of droplet size reduction, improved solubility, stability and their biological activity. This article summarizes the most important information on formulation, fabrication and advancements in chitosan-based nanoemulsions highlighting their potential benefit for applications in the muscle food system. Supervising the all-around executions of chitosan nanoemulsions for various food systems, the current review has been framed to lay down understandings regarding improvements made in the production and functionality of chitosan nanoemulsions for quality retention of meat products. Furthermore, it highlights the novel trends in chitosan-nanoemulsions application in meat based food systems from a preservation and shelf-life prolongation perspective.

Heterologous Expression and Characterization of a High-Efficiency Chitosanase From Bacillus mojavensis SY1 Suitable for Production of Chitosan Oligosaccharides

Chitosanase plays an important role in enzymatic production of chitosan oligosaccharides (COSs). The present study describes the gene cloning and high-level expression of a high-efficiency chitosanase from Bacillus mojavensis SY1 (CsnBm). The gene encoding CsnBm was obtained by homologous cloning, ligated to pPICZαA, and transformed into Pichia pastoris X33. A recombinant strain designated X33-C3 with the highest activity was isolated from 120 recombinant colonies. The maximum activity and total protein concentration of recombinant strain X33-C3 were 6,052 U/ml and 3.75 g/l, respectively, which were obtained in fed-batch cultivation in a 50-l bioreactor. The optimal temperature and pH of purified CsnBm were 55°C and 5.5, respectively. Meanwhile, CsnBm was stable from pH 4.0 to 9.0 and 40 to 55°C. The purified CsnBm exhibited high activity toward colloidal chitosan with degrees of deacetylation from 85 to 95%. Furthermore, CsnBm exhibited high efficiency to hydrolyze different concentration of colloidal chitosan to produce COSs. The result of this study not only identifies a high-efficiency chitosanase for preparation of COSs, but also casts some insight into the high-level production of chitosanase in heterologous systems.

Inhibitory Activity of Shrimp Waste Extracts on Fungal and Oomycete Plant Pathogens

(1) Background: This study was aimed at determining the in vitro inhibitory effect of new natural substances obtained by minimal processing from shrimp wastes on fungi and oomycetes in the genera Alternaria, Colletotrichum, Fusarium, Penicillium, Plenodomus and Phytophthora; the effectiveness of the substance with the highest in vitro activity in preventing citrus and apple fruit rot incited by P. digitatum and P. expansum, respectively, was also evaluated. (2) Methods: The four tested substances, water-extract, EtOAc-extract, MetOH-extract and nitric-extract, were analyzed by HPLC-ESI-MS-TOF; in vitro preliminary tests were carried out to determine the minimal inhibitory/fungicidal concentrations (MIC and MFC, respectively) of the raw dry powder, EtOAc-extract, MetOH-extract and nitric-extract for each pathogen. (3) Results: in the agar-diffusion-assay, nitric-extract showed an inhibitory effect on all pathogens, at all concentrations tested (100, 75, 50 and 25%); the maximum activity was on Plenodomus tracheiphilus, C. gloeosporioides and Ph. nicotianae; the diameters of inhibition halos were directly proportional to the extract concentration; values of MIC and MFC of this extract for all pathogens ranged from 2 to 3.5%; the highest concentrations (50 to 100%) tested in vivo were effective in preventing citrus and apple fruit molds. (4) Conclusions: This study contributes to the search for natural and ecofriendly substances for the control of pre- and post-harvest plant pathogens.

Chitosan Coating Enriched With Ruta graveolens L. Essential Oil Reduces Postharvest Anthracnose of Papaya (Carica papaya L.) and Modulates Defense-Related Gene Expression

Anthracnose of papaya (Carica papaya L.) caused by the fungus Colletotrichum spp. is one of the most economically important postharvest diseases. Coating with chitosan (CS) and Ruta graveolens essential oil (REO) might represent a novel eco-friendly method to prevent postharvest anthracnose infection. These compounds show both antimicrobial and eliciting activities, although the molecular mechanisms in papaya have not been investigated to date. In this study, the effectiveness of CS and REO alone and combined (CS-REO) on postharvest anthracnose of papaya fruit during storage were investigated, along with the expression of selected genes involved in plant defense mechanisms. Anthracnose incidence was reduced with CS, REO, and CS-REO emulsions after 9 days storage at 25°C, by 8, 21, and 37%, respectively, with disease severity reduced by 22, 29, and 44%, respectively. Thus, McKinney's decay index was reduced by 22, 30, and 44%, respectively. A protocol based on reverse transcription quantitative real-time PCR (RT-qPCR) was validated for 17 papaya target genes linked to signaling pathways that regulate plant defense, pathogenesis-related protein, cell wall-degrading enzymes, oxidative stress, abiotic stress, and the phenylpropanoid pathway. CS induced gene upregulation mainly at 6 h posttreatment (hpt) and 48 hpt, while REO induced the highest upregulation at 0.5 hpt, which then decreased over time. Furthermore, CS-REO treatment delayed gene upregulation by REO alone, from 0.5 to 6 hpt, and kept that longer over time. This study suggests that CS stabilizes the volatile and/or hydrophobic substances of highly reactive essential oils. The additive effects of CS and REO were able to reduce postharvest decay and affect gene expression in papaya fruit.

Effective In Vitro Control of Two Phytopathogens of Agricultural Interest Using Cell-Free Extracts of Pseudomonas fluorescens and Chitosan

A biofungicide is a natural product that can be derived from various sources such as, among others, microorganisms, higher plants, animal products, phytochemicals, semiochemicals, and antagonist microorganisms. One of the most important approaches for the production of biofungicides is the combination of biocontrol agents. This study showed the inhibition growth of Alternaria alternata and Fusarium solani treated with cell-free extracts of P. fluorescens. Using thin-layer chromatography and plate assays it was also demonstrated that the cell-free extracts of P. fluorescens contained siderophores and derivates of 4-diacetylphloroglucinol and phenazine. Moreover, the combination of cell-free extracts of P. fluorescens and chitosan [50–1.5% (v/v)] had a synergistic effect since they notably inhibited the mycelial growth of A. altenata and F. solani. Various morphological alterations to the mycelia and conidia of the treated fungi as a result of this combination were also observed. The present study could be a starting point to control other fungal phytopathogens using different cell-free extracts and chitosan as biocontrol agents.

Use of Chitosan and Other Natural Compounds Alone or in Different Strategies with Copper Hydroxide for Control of Grapevine Downy Mildew

Grapevine downy mildew (GDM) is one of the most serious diseases of grapevines. Limitations to the use of copper-based products in organic agriculture according to the European Union (EU) regulation EU/2002/473 and the later EU Commission implementing regulation 2018/1981 have promoted a search for alternatives. This 5-year field trial evaluated the effectiveness of several strategies against GDM using different chitosan-based formulations and application rates in comparison with other natural compounds applied individually or with copper hydroxide. Trials were performed in commercial vineyards with different environmental conditions and grapevine cultivars. For the natural compounds applied as individual treatments, a 0.5%/0.8% chitosan formulation provided the best protection against GDM; the other compounds and formulations were less effective. When copper hydroxide use was halved by combining it with the natural compounds according to three different strategies, the GDM incidence, severity, and McKinney index were reduced, particularly for copper hydroxide applied in combination with the 0.5%/0.8% chitosan formulation. The 0.5%/0.8% chitosan formulation alone and with copper hydroxide provided good protection against GDM during both high-pressure and low-pressure disease seasons. Therefore, chitosan represents a good alternative to copper formulations for the control of GDM and both organic and integrated disease management.

Improving Fruit Quality, Bioactive Compounds, and Storage Life of Date Palm (Phoenix dactylifera L., cv. Barhi) Using Natural Elicitors

“Barhi” date fruit is highly appreciated and widely consumed at the Bisr stage (first edible stage) of maturity. However, maintaining its quality for long periods of time after harvest and throughout marketing is a substantial challenge. Therefore, the objective of this study was to investigate the effects of preharvest spray treatments of 1% chitosan (Ch) in conjunction with 3% calcium chloride (Ca) and 2 mM salicylic acid (SA) on “Barhi” fruit’s shelf life, quality, and phytochemical composition at harvest and during cold storage. All treatments significantly delayed the ripening and decay of “Barhi” dates compared to controls. Ch treatment, followed by Ch + SA and Ch + SA + Ca, showed the lowest weight loss. Ch + Ca, Ch + SA + Ca, and Ch + SA treatments showed significantly lower levels of total soluble solids (TSS) compared to the control fruit. Ch + Ca and Ch + Ca + SA treatments showed no decayed fruit after 60 days of cold storage. At the end of storage time, the Ca treatment, followed by Ch + Ca + SA, showed the greatest total phenolic (TPC), flavonoids (TFC), and tannin (TTC) contents. Ch + SA + Ca, Ch + SA, and Ch showed significantly higher antioxidant and antimicrobial activities compared to controls. Based on these findings, these treatments may be recommended to prolong the shelf life of “Barhi” date fruit.

A Comprehensive Review on the Impact of Edible Coatings, Essential Oils, and Their Nano Formulations on Postharvest Decay Anthracnose of Avocados, Mangoes, and Papayas

Subtropical fruit such as avocados (Persea americana), mangoes (Mangifera indica L.), and papayas (Carica papaya L.) are economically important in international trade and predominantly exported to European destinations. These fruits are highly consumed due to their health benefits. However, due to long-distance shipping and the time required to reach the retail department stores, postharvest losses, due to postharvest decay occurring during the supply chain, affect the fruit quality on arrival at the long-distance distribution points. Currently, the use of synthetic fungicide, Prochloraz^®, is used at the packing line to reduce postharvest decay and retain the overall quality of mangoes and avocados. Due to the ban imposed on the use of synthetic fungicides on fresh fruit, several studies have focused on the development of alternative technologies to retain the overall quality during marketing. Among the developed alternative technologies for commercial adoption is the use of edible coatings, such as chitosan biocontrol agents and essential oil vapors. The objective of this review is to summarize and analyze the recent advances and trends in the use of these alternative postharvest treatments on anthracnose decay in avocados, mangoes, and papayas.

Polysaccharide Matrices for the Encapsulation of Tetrahydrocurcumin-Potential Application as Biopesticide against Fusarium graminearum

Cereals are subject to contamination by pathogenic fungi, which damage grains and threaten public health with their mycotoxins. Fusarium graminearum and its mycotoxins, trichothecenes B (TCTBs), are especially targeted in this study. Recently, the increased public and political awareness concerning environmental issues tends to limit the use of traditional fungicides against these pathogens in favor of eco-friendlier alternatives. This study focuses on the development of biofungicides based on the encapsulation of a curcumin derivative, tetrahydrocurcumin (THC), in polysaccharide matrices. Starch octenylsuccinate (OSA-starch) and chitosan have been chosen since they are generally recognized as safe. THC has been successfully trapped into particles obtained through a spray-drying or freeze-drying processes. The particles present different properties, as revealed by visual observations and scanning electron microscopy. They are also different in terms of the amount and the release of encapsulated THC. Although freeze-dried OSA-starch has better trapped THC, it seems less able to protect the phenolic compound than spray-dried particles. Chitosan particles, both spray-dried and lyophilized, have shown promising antifungal properties. The IC₅₀ of THC-loaded spray-dried chitosan particles is as low as 0.6 ± 0.3 g/L. These particles have also significantly decreased the accumulation of TCTBs by 39%.

Synergistic Effect of Preharvest Spray Application of Natural Elicitors on Storage Life and Bioactive Compounds of Date Palm (Phoenix dactylifera L., cv. Khesab)

Despite the immense capabilities of the date palm, maintaining the fruit’s quality, marketability, and shelf life is still a challenge. This study aimed to assess the synergistic effect of a preharvest spray application of a natural elicitor chitosan, (Ch) 1% alone and in combination with salicylic acid (SA) 2 mM and calcium chloride (Ca) 3%; (Ch,SA, Ca,Ch+Ca, Ch+SA, Ch+SA+Ca), on the quality parameters, storage life, and bioactive compounds content of date fruit from ‘Khasab’ cultivar during cold storage for 60 days. The obtained results revealed that all treatments significantly retard senescence/decay of the fruit compared to the control. Ch+SA treated fruit followed by Ch, and Ch+SA+Ca had the lowest weight loss, color change, and the least decay after 60 days of storage. Ch+Ca, SA, Ca treated fruit had significantly lower levels of total soluble solids and highest total phenolic, tannins, and flavonoids contents compared to the control fruit. Antioxidant activities were found in all treatments, with significantly higher effect in Ch+SA+Ca and Ch+SA compared to the control. Our results provide an evidence for a synergistic effect of elicitors combination to extend the shelf life of date fruit during cold storage by preserving its quality and decreasing senescence/decay and recommend it as a promising strategy.

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.

Multifunctional Role of Chitosan Edible Coatings on Antioxidant Systems in Fruit Crops: A Review

Chitosan-based edible coatings represent an eco-friendly and biologically safe preservative tool to reduce qualitative decay of fresh and ready-to-eat fruits during post-harvest life due to their lack of toxicity, biodegradability, film-forming properties, and antimicrobial actions. Chitosan-based coatings modulate or control oxidative stress maintaining in different manner the appropriate balance of reactive oxygen species (ROS) in fruit cells, by the interplay of pathways and enzymes involved in ROS production and the scavenging mechanisms which essentially constitute the basic ROS cycle. This review is carried out with the aim to provide comprehensive and updated over-view of the state of the art related to the effects of chitosan-based edible coatings on anti-oxidant systems, enzymatic and non-enzymatic, evaluating the induced oxidative damages during storage in whole and ready-to-eat fruits. All these aspects are broadly reviewed in this review, with particular emphasis on the literature published during the last five years.