Comparative performance of bio-based coatings formulated with cellulose, chitin, and chitosan nanomaterials suitable for fruit preservation

Synthesis, characterization and antifungal properties of maleopimaric anhydride modified chitosan

Fruit spoilage can cause huge economic losses, in which fungal infection is one of the main influencing factors, how to effectively control mould and spoilage of fruits and prolong their shelf-life has become a primary issue in the development of fruit and vegetable industry. In this study, rosin derivative maleopimaric anhydride (MPA) was combined with biodegradable and antifungal chitosan (CS) to enhance its antifungal and preservative properties. The modified compounds were characterized by FTIR, 1H NMR spectra and XRD, and the in vitro antifungal properties of the modified compounds were evaluated by the radial growth assay and the minimal inhibitory concentration assay. The preservation effect on small mandarin oranges and longan was studied. The analysis revealed that the modification product (CSMA) of MPA access to C6-OH of CS had a better antifungal effect. In addition, CSMA was more environmentally friendly and healthier than the commercially available chemical preservative (Imazalil), and had the same antifungal preservative effect in preserving small mandarin orange, and was able to extend the shelf life to >24 d. In the preservation of longan, CSMA was more effective against tissue water loss and was able to maintain the moisture in the longan pulp and extend the shelf life. Therefore, CSMA has good application potentials in longan keeping-fresh.

Application of hydroxypropyl methylcellulose to improve the wettability of chitosan coating and its preservation performance on tangerine fruits

Hydroxypropyl methylcellulose (HPMC) was employed as an intermediate layer to enhance interfacial interaction between chitosan (CS) coating and tangerine fruits, thereby improving the preservation effect. Owing to the low surface tension of tangerine fruit (26.04 mN/m), CS coating solutions showed poor wetting properties on fruit peels (contact angle > 100°). However, by applying a 1.0 % (w/v) HPMC coating on fruits, the contact angle of CS solutions with concentrations of 0.5 %, 1.0 %, and 1.5 % (w/v) decreased to 47.0°, 47.4°, and 48.5°, respectively, whereas the spreading coefficient increased to -16.0 mN/m, -17.6 mN/m and -19.8 mN/m, respectively. Subsequently, the effects of the coatings on fruit quality were investigated. The results demonstrated the promising performance of HPMC-CS two-layer coating in inhibiting fruit respiration, reducing decay rate, and maintaining nutrient content. Notably, HPMC-1.5%CS coating not only reduced the decay rate of tangerine fruit by 45 % and 31 %, in comparison to the uncoated group (CK) and pure CS coating respectively, but also maintained a high content of ascorbic acid. Therefore, this study confirmed that the use of amphiphilic polymers for improving the surface properties of fruits can effectively facilitate the wetting of hydrophilic coatings on fruits, and significantly improve the fresh-keeping performance of edible coatings.

Recent Highlights in Sustainable Bio-Based Edible Films and Coatings for Fruit and Vegetable Applications

The present review paper focuses on recent developments in edible films and coatings made of base compounds from biological sources, namely plants, animals, algae, and microorganisms. These sources include by-products, residues, and wastes from agro-food industries and sea products that contribute to sustainability concerns. Chitosan, derived from animal biological sources, such as crustacean exoskeletons, has been the most studied base compound over the past three years. Polysaccharides typically constitute no more than 3-5% of the film/coating base solution, with some exceptions, like Arabic gum. Proteins and lipids may be present in higher concentrations, such as zein and beeswax. This review also discusses the enrichment of these bio-based films and coatings with various functional and/or bioactive compounds to confer or enhance their functionalities, such as antimicrobial, antioxidant, and anti-enzymatic properties, as well as physical properties. Whenever possible, a comparative analysis among different formulations was performed. The results of the applications of these edible films and coatings to fruit and vegetable products are also described, including shelf life extension, inhibition of microbial growth, and prevention of oxidation. This review also explores novel types of packaging, such as active and intelligent packaging. The potential health benefits of edible films and coatings, as well as the biodegradability of films, are also discussed. Finally, this review addresses recent innovations in the edible films and coatings industry, including the use of nanotechnologies, aerogels, and probiotics, and provides future perspectives and the challenges that the sector is facing.

Synthesis, characterization and antifungal properties of dehydroabietic acid modified chitosan

The bioactivities of pristine chitosan are considerable weak compared with the commercial chemicals, which has restricted its broad application prospects in food packaging and preservation. In order to obtain a safe, biologically derived fruits preservative with excellent antifungal properties, dehydroabietic acid (DHA) was used to modify chitosan (CS). The structural characterization of modified chitosans were identified by FTIR and 1H NMR spectra. The XRD pattern showed the modified chitosan changed the crystal structure due to the modification of the amino and/or hydroxyl groups on the chitosan. Their antifungal activities against Penicillium digitutim and Penicillium italicum were investigated in vitro using the radial growth assay and the minimal inhibitory concentration assay. The study also examined the differences in antifungal effect among three modified chitosans. The results showed that DHA only conjugated thehydroxyl group at C-6, bearing free amino group at C-2, exhibited the strongest antifungal effect, with a minimum inhibitory concentration (MIC) of 200 μg/mL. In addition, a comparison of the antifungal activity of the modified compounds with different concentrations of Imazalil demonstrated that the modified biologic antifungal agent was as effective as Imazalil. CSDA can achieve 100 % inhibition of P. digitutim at concentrations >100 μg/mL and remain unchanged for a long time. Because CSDA can enhance the shelf life of longans, DHA-CS, chitosan derivatives, have tremendous promise for use in fruits preservation.

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.

Active coatings based on oxidized chitin nanocrystals and silk fibroins for the control of anthracnose in 'Hass' avocados

Postharvest avocado losses are mainly due to anthracnose disease caused by Colletotrichum gloeosporioides. Chemical fungicides are effective, but their negative effects on health and the environment have led to the search for sustainable alternatives such as biopolymer-based coatings and natural compounds. Therefore, chitin nanocrystals (NCChit) were extracted using a sustainable deep eutectic solvent (DES) and chemically modified into oxidized chitin nanocrystals (O-NCChit) or deacetylated chitin nanocrystals (D-NCChit) to modulate and increase the charge surface density and the dispersibility of the crystals. The modified NCChits were dispersed with silk fibroins (SF), essential oil (EO), melatonin (MT) and/or phenylalanine (Phe) to elaborate active coatings. Antioxidant and antifungal in vitro analyses showed that the O-NCChit/SF-based coating had the best performance. In addition, in vivo tests were carried out through the artificial inoculation of C. gloeosporioides on coated avocados. O-NCChit/SF/MT-based coatings reduced the severity of anthracnose by 45 %, the same effect as the chemical fungicide (Prochloraz®). Moreover, avocado quality parameters during cold storage and the shelf-life period were also evaluated, where nonsignificant differences were observed. Therefore, this study demonstrates the great potential of O-NCChit and SF in combination with active compounds for the control of anthracnose in 'Hass' avocados.

Highly Antibacterial and Antioxidative Carbon Nanodots/Silk Fibroin Films for Fruit Preservation

The issues of fruit waste and safety resulting from rot have spurred a demand for improved packaging systems. Herein, we present highly antibacterial and antioxidative carbon nanodot/silk fibroin (CD/SF) films for fruit preservation. The films are composed of CDs and SF together with a small amount of glycerol via hydrogen bonding, exhibiting outstanding biosafety, transparency, and stretchability. The films effectively integrate key functionalities (atmosphere control, resistance to food-borne pathogens, and antioxidation properties) and can be manufactured in large sizes (about 20 × 30 cm), boasting a transmission rate of 13 183 cm3/m2·day for oxygen and 2860 g/m2·day for water vapor, favoring the preservation of fresh fruits. A convenient dip-coating method enables in situ fabrication of films with a thickness of approximately 14 μm directly on the fruits' surface providing comprehensive protection. Importantly, the films are washable and biodegradable. This work presents a promising technology to produce multifunctional and eco-friendly antibacterial packaging systems.

Gas barrier coating based on cellulose nanocrystals and its preservation effects on mango

Mango is the "king of tropical fruits" because of its attractive appearance, delicious taste, rich aroma, and high nutritional value. However, mango keeps fast metabolizing after harvest, leading to water loss, starch conversion into sugar, texture softening, and decay. Here, a gas barrier coating based on cellulose nanocrystals (CNCs) is proposed to control the post-harvest metabolism of mango. The results of gas barrier permeability show that CNCs enhance the barrier ability of the chitosan (CS) membrane on mango by 202 % and 63 % for oxygen and water vapor, respectively. The gas-barrier coating reduces the climb in pH and the decrease in firmness by 84.9 % and 45.8 %, respectively, decelerating the conversion process from starch to sugar. Besides, introducing clove essential oil (CEO), the CEO mainly adsorbs and crystalizes on the hydrophobic facets of CNCs, presenting high compatibility, increases the antibacterial rate to nearly 100 %. As a consequence, the preservation period of the mango coated by the CNC-based membrane is at least 7-day longer than the control group. Such a gas-barrier coating based on eco-friendly composites must have excellent potential in the preservation of mango, and even for other tropical fruits.

Development of chitin nanofiber coatings for prolonging shelf life and inhibiting bacterial growth on fresh cucumbers

The widespread usage of petroleum-based polymers as single-use packaging has had harmful effects on the environment. Herein, we developed sustainable chitin nanofiber (ChNF) coatings that prolong the shelf life of fresh cucumbers and delay the growth of pathogenic bacteria on their surfaces. ChNFs with varying degrees of acetylation were successfully prepared via deacetylation using NaOH with treatment times of 0-480 min and defibrillated using mechanical blending. With longer deacetylation reaction times, more acetamido groups (-NHCOCH3) in chitin molecules were converted to amino groups (-NH2), which imparted antibacterial properties to the ChNFs. The ChNF morphologies were affected by deacetylation reaction time. ChNFs deacetylated for 240 min had an average width of 9.0 nm and lengths of up to several μm, whereas rod-like structured ChNFs with a mean width of 7.3 nm and an average length of 222.3 nm were obtained with the reaction time of 480 min. Furthermore, we demonstrated a standalone ChNF coating to extend the shelf life of cucumbers. In comparison to the rod-like structured ChNFs, the 120 and 240-min deacetylated ChNFs exhibited a fibril-like structure, which considerably retarded the moisture loss of cucumbers and the growth rate of bacteria on their outer surfaces during storage. Cucumbers coated with these 120 and 240-min deacetylated ChNFs demonstrated a lower weight loss rate of ⁓ 3.9% day-1 compared to the uncoated cucumbers, which exhibited a weight loss rate of 4.6% day-1. This protective effect provided by these renewable ChNFs holds promising potential to reduce food waste and the use of petroleum-based packaging materials.

The characterization of antimicrobial nanocomposites based on chitosan, cinnamon essential oil, and TiO2 for fruits preservation

The freshness and safety of fruits have always been crucial issues in the development of the industry. However, the existing fresh-keeping methods have limited effect, meanwhile, the preservation mechanism of different materials. In this study, Cinnamon essential oil (CEO), TiO_2, and chitosan (CS) were compounded to prepare safe and renewable nanocomposites (CS-T-C) for fruit preservation. The results showed that CEO mainly destroyed the bacterial cell wall through penetration, while TiO₂ is through destruction. The strawberry coated with CS-T-C showed better hardness, lower weight loss and mildew rate, and the shelf-life at 20℃ was extended for four days compared with the control. And all four nanocomposites were not cytotoxic. In summary, nanocomposites can deal with many problems through different mechanisms to maximize the fresh-keeping effect, and the nanocomposites developed in this work might be a good choice for fruit preservation.

Chitosan-based nanocomposites as coatings and packaging materials for the postharvest improvement of agricultural product: A review

The perishability nature of harvested fruits and vegetables, along with the effect of environmental factors, storage conditions, and transportation, reduce the products' quality and shelf-life. Considerable efforts have been allocated to alternate conventional coatings based on new edible biopolymers for packaging. Chitosan is an attractive alternative to synthetic plastic polymers due to its biodegradability, antimicrobial activity, and film-forming properties. However, its conservative properties can be improved by adding active compounds, limiting microbial agents' growth and biochemical and physical damages, and enhancing the stored products' quality, shelf-life, and consumer acceptability. Most of the research on chitosan-based coatings focuses on antimicrobial or antioxidant properties. Along with the advancement of polymer science and nanotechnology, novel chitosan blends with multiple functionalities are required and should be fabricated using numerous strategies, especially for application during storage. This review discusses recent developments in using chitosan as a matrix to fabricate bioactive edible coatings and their positive impacts on increasing the quality and shelf-life of fruits and vegetables.

Advances in formulation, functionality, and application of edible coatings on fresh produce and fresh-cut products: A review

With the increasing population of the world food demand is also increasing but unfortunately, many countries in the world are lacking suitable and economical postharvest preservation techniques to minimize increasing postharvest losses. To ensure food security advanced production technologies, distribution systems and minimum losses should be ensured to give accessibility of food to all population groups. Innovative preservation techniques should be adopted by the agriculture sector to meet intercontinental distribution and demand for fresh produce. The application of the edible coating is a novel technique in postharvest preservation due to its simple application, ecofriendly nature, and effectiveness. Edible coatings can also improve the quality and safety aspects of fresh produce and thus extends shelf life. This review aimed to update information about recent advances in edible coating formulation and application mainly on fresh-cut /minimally processed fruits and vegetables. This information will be helpful for processors to select the best coating material and its effective concentration for different fresh and minimal processed vegetables.

Optimization of the Formulation of Sago Starch Edible Coatings Incorporated with Nano Cellulose Fiber (CNF)

This study aimed to produce new edible coatings based on the mixture of sago starch, cellulose nanofiber (CNF), glycerol, and tween-80.The effect of sago starch (5–10 g of starch/100 ml of distilled water), CNF (0.5–20% w/w), glycerol (10–30% w/w), and tween-80 (0.5–10% w/w) based on sago starch concentration on contact angle (CA), water vapor permeability (WVP), oxygen permeability (PO2) and tensile strength (TS) properties of the edible coatings were optimized using factorial experimental design (2k).The result showed that the linear model for all independent variables was significant (<i>P</i><0.05) on all responses (dependent variable).The sago starch concentration depicted a significant (p < 0.001) positive effect on contact angle; CNF showed a statistically significant effect on WVP, PO2, and TS; tween-80 showed a significant effect on all dependent variables, whereas glycerol only affected WVP. The optimum concentrations of sago starch, CNF, glycerol, and tween-80 were predicted to be 5 g/100 ml distilled water, 20% w/w, 10% w/w, and 0.5% w/w based on sago starch, respectively to obtain the minimum contact angle, WVP, PO2, and the maximum TS. The predicted data for the optimized coating formulation were in good agreement with the experimental value. This work revealed that the potential of sago starch/CNF based coating formulation could be effectively produced and successfully applied for coating of food.

Novel Approaches for Sustainable Horticultural Crop Production: Advances and Prospects

Reduction of plant growth, yield and quality due to diverse environmental constrains along with climate change significantly limit the sustainable production of horticultural crops. In this review, we highlight the prospective impacts that are positive challenges for the application of beneficial microbial endophytes, nanomaterials (NMs), exogenous phytohormones strigolactones (SLs) and new breeding techniques (CRISPR), as well as controlled environment horticulture (CEH) using artificial light in sustainable production of horticultural crops. The benefits of such applications are often evaluated by measuring their impact on the metabolic, morphological and biochemical parameters of a variety of cultures, which typically results in higher yields with efficient use of resources when applied in greenhouse or field conditions. Endophytic microbes that promote plant growth play a key role in the adapting of plants to habitat, thereby improving their yield and prolonging their protection from biotic and abiotic stresses. Focusing on quality control, we considered the effects of the applications of microbial endophytes, a novel class of phytohormones SLs, as well as NMs and CEH using artificial light on horticultural commodities. In addition, the genomic editing of plants using CRISPR, including its role in modulating gene expression/transcription factors in improving crop production and tolerance, was also reviewed.

Recent Advancements of Polysaccharides to Enhance Quality and Delay Ripening of Fresh Produce: A Review

The freshness of fruits and vegetables plays a significant role in consumers' decision to purchase a product at the supermarket. Fresh-cut products are the latest trend in fulfilling society's restless needs, and the food industry is faced with the challenge of maintaining the quality of fresh produce. The food industry is concerned with the natural maturation and degradation of fruits and vegetables, primarily due to enzymatic reactions. It has been demonstrated that polysaccharide coatings effectively preserve the freshness of these products, extending their shelf life depending on the preservation method used. This review informs readers about the different types of polysaccharides and their novel applications as natural food preservatives in the past five years (2018-2022). The key findings summarized the properties of the antimicrobial agent, the molecular mechanism of action, coating methods, and formulation for the preservation approach. Additionally, we discuss the scientific factors influencing polysaccharide processing and preservation efficacy, allowing it to be used in post-harvest management.

Impact of Biodegradable Materials on the Quality of Plums

Edible starch-based materials have shown a positive impact on quality parameters. In this study, plums (Prunus domestica cv. Jojo) were divided into five groups: a control, two coating treatments (starch and starch-whey protein (80–20%), and two film systems (starch and starch-whey protein (80–20%). Biodegradable packaging, particularly the coating treatment, had no negative effect on color parameters. After 28 days of performed tests, firmness was boosted with starch and starch-whey protein (80–20%) films. With the coated materials, there was no significant difference compared to control group. The lowest transpiration velocity was of plums wrapped in starch films. In the case of respiration rate, no significant difference was observed between the packaging and control samples. After the conducted trials, the weight loss of untreated plums was at 10%, while 5% of weight loss was noticed for plums wrapped in starch materials, and around 6% was noticed for the other materials. Oxygen permeability was higher for S-WP films, the thickness of S and S-WP films were comparable and thickness of starch coating was around 60% higher than S-WP. Both films have an affinity to water and both show typical behavior of water vapor sensitive hydrophilic biopolymers. The starch film with the addition of 20% of proteins increased the resistance of gas exchanges, which represents one of its great benefits.

Potential of engineered nanostructured biopolymer based coatings for perishable fruits with Coronavirus safety perspectives

Fresh fruits are prioritized needs in order to fulfill the required health benefits for human beings. However, some essential fruits are highly perishable with very short shelf-life during storage because of microbial growth and infections. Thus improvement of fruits shelf-life is a serious concern for their proper utlization without generation of huge amount of fruit-waste. Among various methods employed in extension of fruits shelf-life, design and fabrication of edible nanocoatings with antimicrobial activities have attracted considerable interest because of their enormous potential, novel functions, eco-friendly nature and good durability. In recent years, scientific communities have payed increased attention in the development of advanced antimicrobial edible coatings to prolong the postharvest shelf-life of fruits using hydrocolloids. In this review, we attempted to highlight the technical breakthrough and recent advancements in development of edible fruit coating by the application of various types of agro-industrial residues and different active nanomaterials incorporated into the coatings and their effects on shelf-life of perishable fruits. Improvements in highly desired functions such as antioxidant/antimicrobial activities and mechanical properties of edible coating to significantly control the gases (O₂/CO₂) permeation by the incorporation of nanoscale natural materials as well as metal nanoparticles are reviewed and discussed. In addition, by compiling recent knowledge, advantages of coatings on fruits for nutritional security during COVID-19 pandemic are also summarized along with the scientific challenges and insights for future developments in fabrication of engineered nanocoatings.

Fabricating an anti-shrinking κ-carrageenan/sodium carboxymethyl starch film by incorporating carboxylated cellulose nanofibrils for fruit preservation

A stronger and dimension-stabilized film was obtained using κ-carrageenan and sodium carboxymethyl starch (CMS) with carboxylated cellulose nanocrystals (C-CNC) as a reinforcing agent and anti-shrinkage agent. C-CNC endowed the films with better mechanical properties as well as excellent dimensional stability. The film solutions showed shear thinning and acted as a pseudoplastic fluid. When C-CNC content was increased from 0% to 12%, the tensile strength and elongation at break of the films improved from 23.89 MPa to 38.37 MPa and 21.00% to 27.31%, respectively. The films maintained good thermal stability and barrier performance. The Zeta potential of the film suspension can reach below -30 mV, indicating C-CNC enhanced the electrostatic repulsion in the film-forming system, which favored the network structure more continuous and stable. By virtue of the excellent mechanical properties and dimensional stability, strawberries can be tightly wrapped without cracks by the coatings to delay the deterioration greatly. By comparing the weight loss rate, Vc, total soluble solid, hardness, titratable acid and pH, CCC12-coated strawberries were closer to fresh ones. Therefore, this study has developed a feasible, low-cost and green fruit coating that can be potentially utilized on a large-scale.

Latest Developments in Edible Coatings on Minimally Processed Fruits and Vegetables: A Review

The food industry nowadays is facing new challenges in terms of sustainability and health implications of packaging and processing techniques. Due to their desire for new and natural products coupled with changes in lifestyle, consumers are looking for food products that have been less processed but possess longer shelf life and maintain nutritional and sensorial proprieties during storage. These requirements represent real challenges when dealing with highly perishable food products, such as fruits and vegetables. Thus, in recent years, edible coatings have been intensively developed and studied because of their capacity to improve the quality, shelf life, safety, and functionality of the treated products. Edible coatings can be applied through different techniques, like dipping, spraying, or coating, in order to control moisture transfer, gas exchange, or oxidative processes. Furthermore, some functional ingredients can be incorporated into an edible matrix and applied on the surface of foods, thus enhancing safety or even nutritional and sensory attributes. In the case of coated fruits and vegetables, their quality parameters, such as color, firmness, microbial load, decay ratio, weight loss, sensorial attributes, and nutritional parameters, which are very specific to the type of products and their storage conditions, should be carefully monitored. This review attempts to summarize recent studies of different edible coatings (polysaccharides, proteins, lipids, and composites) as carriers of functional ingredients (antimicrobials, texture enhancers, and nutraceuticals) applied on different minimally processed fruits and vegetables, highlighting the coating ingredients, the application methods and the effects on food shelf life and quality.

Chitosan as a Coating for Biocontrol in Postharvest Products: A Bibliometric Review

The aim of this work was to carry out a systematic literature review focused on the scientific production, trends, and characteristics of a knowledge domain of high worldwide importance, namely, the use of chitosan as a coating for postharvest disease biocontrol in fruits and vegetables, which are generated mainly by fungi and bacteria such as Aspergillus niger, Rhizopus stolonifera, and Botrytis cinerea. For this, the analysis of 875 published documents in the Scopus database was performed for the years 2011 to 2021. The information of the keywords' co-occurrence was visualized and studied using the free access VOSviewer software to show the trend of the topic in general. The study showed a research increase of the chitosan and nanoparticle chitosan coating applications to diminish the postharvest damage by microorganisms (fungi and bacteria), as well as the improvement of the shelf life and quality of the products.