Composite films based on chitosan and epigallocatechin gallate grafted chitosan: Characterization, antioxidant and antimicrobial activities

Enhanced antioxidant activity of low-molecular-weight hyaluronan-based coatings amended with EGCG for Torreya grandis kernels preservation

Polysaccharide coating protection technology has always been a research hotspot in the field of food preservation. In this study, hyaluronic acid (HA), the widely used green polysaccharide was optimized by a free radical mediated method for covalent grafting high antioxidant epigallocatechin gallate (EGCG) to prepare copolymers (HA-EGCG) and applied to the preservation of Torreya grandis kernels. The physicochemical properties, antioxidant activities and application effect of HA-EGCG were investigated. The results found that low-molecular-weight HA (LHA) could obtain a higher grafting rate than high-molecular-weight HA (HHA), reaching 93.5 %. For structural character, the LHA-EGCG showed good stablility, which improved the surface roughness of the edible coating and the addition of EGCG significantly enhanced the antioxidant activities (p < 0.01). For application effect, LHA-EGCG coating significantly inhibit the change of appearance color, and increase of malonaldehyde, acid value, and peroxide value during long-term storage of T. grandis kernels, and could maintain its flavor to prolong quality retention. Collectively, the edible coating of HA grafted EGCG significantly prolong the quality of the kernel and has broad application potential in the field of food preservation.

Effects of keto acid crosslinking on the structure and properties of chitosan based casted and hot-pressed films

Crosslinking is one of the most effective ways to enhance the performance of bio-based films, and suitable crosslinking agents are crucial for the enhancement. In this study, four α-ketoacids, namely glyoxylate, pyruvate, oxaloacetate, and α-ketoglutarate were used to crosslink chitosan at room temperature. The effects of crosslinking on the structure and properties of chitosan films were studied, and the reaction mechanism was explored. Fourier Transform Infrared spectroscopy and X-ray Photoelectron Spectroscopy indicated that ion attraction and Schiff base reactions occurred between keto acids and chitosan. Glyoxylate developed the most effective covalent crosslinking with chitosan, whereas α-ketoglutarate had the highest ionic crosslinking ratio. Keto acid crosslinking reduced the orderliness of chitosan, improved the uniformity of the film matrix and increased its UV-blocking capacity. Glyoxylate-crosslinked chitosan film demonstrated excellent tensile strength (160 MPa), water stability (water solubility about 11.71 %), and extremely low oxygen permeability (2.65 × 10-16 cm3·cm/cm-2·s-1· Pa-1). Despite the weakened thermal stability and water barrier property, glyoxylate crosslinking shows great potential for the preparation of high-strength and high‑oxygen-resistance chitosan films. Furthermore, the glyoxylate-crosslinked chitosan film could be produced by hot pressing and performed satisfactorily.

Application of chitosan/Nano-TiO₂/Daisy essential oil composite film for the preservation of Actinidia arguta: Inhibition of spoilage microorganisms and induction of resistance

This study explores the inhibitory effects of a chitosan/nano-TiO₂/Daisy Essential Oil (CSTD) composite film on spoilage microorganisms affecting Actinidia arguta. Owing to its high nutritional value and water content, Actinidia arguta is highly susceptible to microbial spoilage, leading to a significantly shortened shelf life. Traditional chemical preservation methods are ineffective against microbial spoilage and raise concerns about safety and environmental sustainability, highlighting the demand for natural, effective alternatives. Chitosan, a natural polysaccharide, shows promise due to its biocompatibility and biodegradability. However, its mechanical, antimicrobial, and antioxidant properties require enhancement. To address these limitations, this study incorporates nano-TiO₂ and Daisy Essential Oil into chitosan to develop a composite film. Key spoilage microorganisms of Actinidia arguta were isolated and identified, with Rhizopus stolonifera reported for the first time as one of the spoilage organisms. The composite film demonstrated significant inhibitory effects against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Bacillus amyloliquefaciens, Aspergillus niger, Neopestalotiopsis clavispora, Aspergillus piperis, and Rhizopus stolonifera. Resistance induction experiments further revealed that CSTD effectively delayed oxidative stress and enzymatic degradation linked to fruit spoilage, significantly extending the shelf life of Actinidia arguta. These findings provide theoretical support for developing effective preservation techniques for Actinidia arguta.

Antimicrobial Potential of Polyphenols: Mechanisms of Action and Microbial Responses-A Narrative Review

Polyphenols (PPs) are recognized as bioactive compounds and antimicrobial agents, playing a critical role in enhancing food safety, preservation, and extending shelf life. The antimicrobial effectiveness of PPs has different molecular and biological reasons, predominantly linked to their hydroxyl groups and electron delocalization, which interact with microbial cell membranes, proteins, and organelles. These interactions may reduce the efficiency of metabolic pathways, cause destructive damage to the cell membrane, or they may harm the proteins and nucleic acids of the foodborne bacteria. Moreover, PPs exhibit a distinctive ability to form complexes with metal ions, further amplifying their antimicrobial activity. This narrative review explores the complex and multifaceted interactions between PPs and foodborne pathogens, underlying the correlation of their chemical structures and mechanisms of action. Such insights shed light on the potential of PPs as innovative natural preservatives within food systems, presenting an eco-friendly and sustainable alternative to synthetic additives.

Photo-responsive Cu-tannic acid nanoparticle-mediated antibacterial film for efficient preservation of strawberries

The existing films used for fruit preservation suffer from insufficient preservation abilities. This study introduces Cu-tannic acid (Cu-TA) nanoparticles, synthesized from tannic acid (TA) and Cu2+, to enhance food packaging properties. Integrated into a chitosan-gelatin (CG) matrix, the resultant Cu-TA nanocomposite films exhibit superior antibacterial efficacy and killing rates of Escherichia coli and Staphylococcus aureus more than 99 %, and double the shelf life of strawberries, underscoring the exceptional freshness preservation capabilities of film. Additionally, the tensile strength of the Cu-TA nanocomposite films increased by 1.75 times, the DPPH radical scavenging percentage increased from 29.4 % to 68.4 %, and the water vapor permeability (WVP) decreased by about 60 % compared to the pure CG films. Comprehensive cytotoxicity and migration assessments confirm the safety of film, paving the way for their application in food packaging. The excellent performance of the Cu-TA nanocomposite films positions them as a formidable solution for protecting perishable food items.

Preparation and application of chitosan/nano-TiO₂/daisy essential oil composite films in the preservation of Actinidia arguta

Chitosan, a natural polysaccharide, is widely recognized for its biocompatibility, biodegradability, and film-forming properties, making it an ideal candidate for food preservation applications. This study focuses on the development of chitosan-based nanocomposite films incorporating nano-TiO2 and Daisy Essential Oil for the preservation of Actinidia arguta. The composite films were synthesized and characterized using FT-IR, XRD, SEM, TGA, UV-Visible spectroscopy, and contact angle measurements to evaluate their structural, thermal, and physical properties. The films exhibited enhanced mechanical strength, antimicrobial activity, and antioxidant capacity. Application of these films on Actinidia arguta demonstrated significant improvements in weight loss, hardness, decay rate, total microbial count, respiration rate, soluble solids content, vitamin C, titratable acidity, and enzyme activities during storage. The results indicate that chitosan/nano-TiO2/DEO composite films effectively extend the shelf life and maintain the quality of Actinidia arguta, providing a promising approach for natural and sustainable food preservation.

Development of anti-bacterial bio-transfer double sheet layer of polyvinyl alcohol/carboxymethyl cellulose films infused with Astragalus tribuloides leaf extract for beef burgers preservation

This study was conducted to develop biodegradable films using a combination of carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA) and purified leaves extract of Astragalus tribuloides (ATE). Various traits of the films, including their morphology description, thermal behavior, tensile/elongation properties and physical characteristics were examined. The scanning electron microscope (SEM) photographs showed smooth surface with small amounts of ATE, but rougher with higher concentrations of 1.4 %. The Fourier-transform infrared spectroscopy (FTIR) showed a direct relationship between the ATE extract and the PVA/CMC matrix. The films also showed thermal stability behaviors. The study found that the addition of ATE up to 0.8 % caused the films to become opaquer in color and raised their opacity up to 3.909. As a result, the films exhibited reduced moisture absorption (8.21 %) and solubility (27.11 %), making them retard penetrating water vapor up to (1.785 × 10-10 g.m-1 s-1 Pa-1) and could preserve the thiobarbituric acid reactive substances (TBARS) and overall color discrepancies of burger in refrigerated storage.

Recent advances in chitosan-based active and intelligent packaging films incorporated with flavonoids

Biopolymer-based films are promising packaging materials to maintain food quality, reduce food waste and ensure food safety. Chitosan, a biopolymer with excellent film-forming ability, can act as the carrier for plant-derived bioactive compounds. In the past decade, several studies have reported chitosan-based films incorporated with different classes of flavonoids, including flavones, flavanones, isoflavones, flavonols, flavanols and anthocyanidins. These films, based on their functionality, can be divided into chitosan/flavonoid active packaging films and chitosan/anthocyanin (the glycosylated anthocyanidin) intelligent packaging films. This paper presents a comprehensive review on active and intelligent packaging films prepared from chitosan and different classes of flavonoids, with special attention being paid to the preparation, physical and functional properties, stabilization, and application of the films. Factors affecting the physical and functional properties of the films are summarized. In addition, the challenges for the commercial production and application of the films in active and intelligent packaging fields are discussed.

Preparation and characterization of polyphenol-chitosan conjugate-eugenol essential oil microcapsule and its effect on storage behavior of cherry tomato

Given the high volatility, low water solubility, and oxidative sensitivity of essential oils, this study synthesized microcapsules of essential oil (EEO) (quercetin-chitosan-EEO [QE-CS-EEO]) using a QE-CS graft copolymer as the wall material and EEO as the core material. Research findings indicate that QE-CS exhibits superior in vitro antioxidant activity, with scavenging abilities for 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) ABTS+ radicals being 58.71% and 77.03% greater than those of CS, respectively, thereby providing more effective protection for the essential oil. In comparison to CS essential oil, microcapsules (CS-EEO), QE-CS-EEO demonstrated an 18.65% increase in EEO encapsulation efficiency, achieving a total encapsulation efficiency of 41.29%. Based on these results, various edible coating solutions were formulated, including Control, E1 (1% CS), E2 (0.5% CS + 0.5% CS-EEO), E3 (0.5% CS + 0.5% QE-CS-EEO), and E4 (1% EEO), to extend the shelf life of cherry tomatoes. Notably, cherry tomatoes treated with the E3 formulation maintained superior freshness indicators, exhibiting an extended shelf life of approximately 9-12 days compared to the control group. This study aims to explore a novel microcapsule wall material and provide a strategy for extending the shelf life of fruits and vegetables, thereby minimizing food waste.

Biopolymer-polyphenol conjugates: Novel multifunctional materials for active packaging

The development of natural active packaging materials and coatings presents a promising alternative to petroleum-based packaging solutions. These materials are engineered by incorporating functional ingredients with preservative capabilities. Concurrently, research has highlighted the diverse physicochemical, functional, and health-promoting properties of protein-polyphenol, polysaccharide-polyphenol, and protein-polysaccharide-polyphenol conjugates within various food formulations. However, a critical gap exists regarding the exploration of these biopolymers as active packaging materials. In contrast to conventional approaches for developing active packaging materials, this review presents a novel perspective by focusing on biopolymer-polyphenol conjugates. In this work, we delve into the realm of active packaging materials and coatings constructed from these conjugates, highlighting their potential as multifunctional active components in food packaging and preservation. This review comprehensively investigates the physicochemical properties, functionalities, and health-promoting activities associated with biopolymer-polyphenol conjugates. Their emulsification, antioxidant, and antimicrobial activities, coupled with enhancements in mechanical strength and permeability properties, contribute to their multifunctional nature. Furthermore, we explore the potential advantages and limitations of utilizing these conjugates in active packaging applications. Finally, the review concludes by proposing crucial research avenues for further exploration of biopolymer-polyphenol conjugates within the domain of active food packaging.

Gallic Acid Based Polymers for Food Preservation: A Review

The extensive usage of nonbiodegradable plastic materials for food packaging is a major environmental concern. To address this, researchers focus on developing biocompatible and biodegradable food packaging from natural biopolymers, such as polysaccharides, proteins, and polyesters. These biopolymer-based packaging materials extend the shelf life of food due to their inherent antimicrobial and antioxidant properties. An important additive that enhances these beneficial effects is gallic acid (GA), a naturally occurring phenolic compound. GA exhibits potent antioxidant activity by scavenging free radicals and excellent antimicrobial activity against a wide range of bacteria by disrupting cell membranes. These gallic acid based active packaging solutions have demonstrated remarkable abilities to inhibit lipid oxidation, enzymatic browning, and microbial contamination and even retard the ripening processes in mushrooms, walnuts, strawberries, fresh-cut apples, bananas, fish, pork, and beef. This review focuses on the antioxidant, antibacterial, and food preservation capabilities of GA-incorporated biodegradable food packaging materials as an eco-friendly alternative to conventional plastic packaging.

Chitosan Extracted from the Biomass of Tenebrio molitor Larvae as a Sustainable Packaging Film

Waste from non-degradable packaging materials poses a serious environmental risk and has led to interest in developing sustainable bio-based packaging materials. Sustainable packaging materials have been made from diverse naturally derived materials such as bamboo, sugarcane, and corn starch. In this study, we made a sustainable packaging film using chitosan extracted from the biomass of yellow mealworm (Tenebrio molitor) shell waste. The extracted chitosan was used to create films, cross-linked with citric acid (CA) and with the addition of glycerol to impart flexibility, using the solvent casting method. The successful cross-linking was evaluated using Fourier-Transform Infrared (FTIR) analysis. The CA cross-linked mealworm chitosan (CAMC) films exhibited improved water resistance with moisture content reduced from 19.9 to 14.5%. Improved barrier properties were also noted, with a 28.7% and 10.2% decrease in vapor permeability and vapor transmission rate, respectively. Bananas were selected for food preservation, and significant changes were observed over a duration of 10 days. Compared to the control sample, bananas packaged in CAMC pouches exhibited a lesser loss in weight because of excellent barrier properties against water vapor. Moreover, the quality and texture of bananas packaged in CAMC pouch remained intact over the duration of the experiment. This indicates that adding citric acid and glycerol to the chitosan structure holds promise for effective food wrapping and contributes to the enhancement of banana shelf life. Through this study, we concluded that chitosan film derived from mealworm biomass has potential as a valuable resource for sustainable packaging solutions, promoting the adoption of environmentally friendly practices in the food industry.

Active Packaging Film Developed by Incorporating Starch Aldehyde-Quercetin Conjugate into SPI Matrix

In this study, soy protein isolate (SPI) films incorporating quercetin-grafted dialdehyde starch (DAS-QR) and DAS/QR, respectively, were developed. The structural, physical, and functional properties of the composite films were determined. The results suggested that DAS-QR and DAS/QR formed hydrogen bonding with the SPI matrix, which improved the structural properties of the films. The light-blocking capacity, thermal stability, hydrophobicity, tensile strength, elongation at break, and antioxidant and antibacterial abilities of SPI films were improved by DAS-QR and DAS/QR. Notably, SPI films incorporated with DAS-QR exhibited better performance than those with DAS/QR in terms of antioxidant (SPI/DAS-QR: 79.8% of DPPH and 62.1% of ABTS scavenging activity; SPI/DAS/QR: 71.4% of DPPH and 56.0% of ABTS scavenging activity) and antibacterial abilities against S. aureus (inhibition rate: 92.7% for SPI/DAS-QR, 83.4% for SPI/DAS/QR). The composite coating film SPI/DAS-QR effectively maintained appearance quality, delayed the loss of weight and total soluble solids, postponed malondialdehyde accumulation, and decreased peroxidase activity and microbial contamination in fresh-cut potatoes. These good performances highlight SPI/DAS-QR as a promising active packaging material for fresh-cut product preservation.

Preparation of nanocellulose light porous material adsorbed with tannic acid and its application in fresh-keeping pad

This study fabricated nanocellulose lightweight porous material (TOCNF-G-LPM-TA) as absorbent fresh-keeping pad for meat products, using TEMPO-oxidized cellulose nanofibril (TOCNF) and gelatin as structural skeleton and tannic acid (TA) as antibacterial component of TOCNF lightweight porous material (TOCNF-G-LPM). The adsorption kinetics, capacity and mechanism of TOCNF-G-LPM in different initial concentrations of TA solutions were investigated, the antioxidant and antibacterial properties of TOCNF-G-LPM-TA and its fresh-keeping effect on refrigerated pork at 4 ℃ were studied. Due to strong hydrogen bonding and porous structure, TOCNF-G-LPM exhibited excellent TA adsorption ability (230 mg/g) conforming with pseudo-second-order kinetic and Langmuir isotherm models. TA endowed TOCNF-G-LPM with good antioxidant and antibacterial activities. According to changes in appearance, pH and TVB-N values of pork during storage at 4 ℃, TOCNF-G-LPM-TA effectively extended the shelf life of refrigerated pork. This work provides a facile method for preparing nanocellulose based absorbent fresh-keeping pads.

Fabrication of biodegradable and antibacterial films of chitosan/polyvinylpyrrolidone containing Eucalyptus citriodora extracts

The main objective of this work is to develop biodegradable active films through the combination of the extracts with different solvents sourced from Eucalyptus citriodora leaves, with films made of chitosan (Cs) and polyvinylpyrrolidone (PVP). Chromatographic profiling investigations were carried out to examine the antibacterial characteristics of E. citriodora extracts before their direct incorporation into the polymer films. At this point, the potent antimicrobial properties of the phenol compounds and bioactive components demonstrated an antibacterial activity that was particularly noticeable at a hexane resolution. Different morphological characteristics were seen on films made from these solvent extracts, such as Cs/PVP-AE, Cs/PVP-EAE, and Cs/PVP-HE, when scanning electron microscopy was used. Numerous other outcomes of all the interactions between the extract particles and the film were shown by the pores defined by the Cs/PVP film's porous nature. The addition of the extracts, either alone or in combination, greatly enhanced the Cs/NC/PVP films' mechanical characteristics. It has also been shown that adding plant extracts greatly increased the antibacterial activity of these films. These findings reveal that Cs/PVP films loaded with extract may be utilized as more environmentally acceptable substitutes for possible food packaging application by increasing shelf life of food products.

Preparation, characterization and application of antioxidant packaging films based on chitosan-epicatechin gallate conjugates with different substitution degrees

In this study, chitosan (CS) was conjugated with epicatechin gallate (ECG) to prepare CS-ECG conjugates with different substitution degrees (5.18 %, 6.36 % and 7.74 %). Then, antioxidant packaging films were fabricated by blending CS and CS-ECG conjugates. The impact of CS-ECG conjugates' substitution degree on the functionality of CS/CS-ECG films was determined. CS-ECG conjugates showed UV absorption at 275 nm, proton signal at 6.85 ppm and infrared absorption at 1533 cm-1, assigning to the conjugated ECG. As compared with CS, CS-ECG conjugates exhibited less crystalline state but higher antioxidant activity. The structural characterization of CS/CS-ECG films showed CS and CS-ECG conjugates formed hydrogen bonds. CS/CS-ECG films displayed 26.35 %-29.23 % water solubility, 85.61°-86.96° water contact angle, 3.11-3.41 × 10-11 g m-1 s-1 Pa-1 water vapor permeability, 0.29-0.34 cm3 mm m-2 day-1 atm-1 oxygen permeability, 31.54-36.20 MPa tensile strength, 50.12 %-56.40 % elongation at break, as well as potent antioxidant activity and oil oxidation inhibitory ability. Notably, the film containing CS-ECG conjugate with 7.74 % substitution degree had the strongest barrier ability, mechanical property, antioxidant activity and oil oxidation inhibitory ability. Results suggested the substitution degree of CS-ECG conjugates was positively correlated with the barrier, mechanical and antioxidant properties of CS/CS-ECG films.

Biodegradable bio-film based on Cordyceps militaris and metal-organic frameworks for fruit preservation

In this study, Cordyceps militaris matrix was employed for the first time to fabricate a biodegradable food packaging. Carmine and Ag@CuBTC were introduced to cross-link with mycelium and were uniformly dispersed within the matrix to enhance the water resistance, antimicrobial, and antioxidant properties of the bio-films. The bio-film displayed high biodegradability, with nearly 100 % degradation achieved after three weeks. The bio-film exhibited exceptional resistance to oxidation (49.30 % DPPH and 93.94 % ABTS•+), as well as effective inhibitory capabilities against E. coli and S. aureus, respectively. The composite film maintained a high CO2/O2 selective permeability, which was advantageous for mitigating fruit metabolism and extending shelf life. Simultaneously, food preservation experiments confirmed that these bio-films can decelerate the spoilage of fruits and effectively prolong the shelf-life of food. The experimental findings indicated that the prepared Bio-R-Ag@Cu film held promise as an environmentally friendly biodegradable material for food packaging.

Electrospinning Silk-Fibroin-Based Fibrous Membranes with AgNPs for Antimicrobial Application

Silk fibroin (SF) has excellent biocompatibility and is one of the most commonly used polymer materials. However, SF fibers have serious drawbacks as antibacterial materials due to their lack of stability and bacterial resistance. Therefore, it is of paramount significance to enhance the stability and bolster the bacterial resistance of SF fibers. In this study, SF fibers were fabricated and loaded with Ag nanoparticles (AgNPs) to improve the antimicrobial properties of the fibers. The impact of reduction conditions on the size of AgNPs was also investigated. In an antibacterial test, the fibers that were prepared exhibited over 98% bacterial resistance against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Therefore, as an efficient antibacterial material, these fibers are expected to become a candidate material in medical and textile fields. This study offers a novel approach for the utilization of SF fibers in the realm of antibacterial applications.

Enhanced physical properties, antioxidant and antibacterial activity of bio-composite films composed from carboxymethyl cellulose and polyvinyl alcohol incorporated with broccoli sprout seed extract for butter packaging

This study investigated the development of biodegradable films made from a combination of carboxymethyl cellulose (CMC), Polyvinyl alcohol (PVA), and purified extract of broccoli sprout seed (BSSE). The films were characterized for their color, physical properties, surface morphology, crystallinity, mechanical properties, and thermal properties. The addition of BSSE up to 1.4 % to the film matrix imparted opaque color and increased opacity up to 3.652. The films also became less moisture-absorbent 8.21 %, soluble 19.16 %, and permeable to water vapor 1.531 (× 10-10 g.m-1 s-1 pa-1). By utilizing 0.7 % from BSSE inside films, the surface of the films became smoother but became rough with higher concentrations 2.1 % of BSSE. Fourier transform infrared (FT-IR) analysis showed that there was physical interaction between the BSSE extract and the PV/CM matrix. The films showed good thermal stability, and the incorporation of BSSE improved their ability to preserve the acidity, TBARS, peroxide value, and total color differences of butter during cold storage.

Development of biobased multifunctional films incorporated with essential oils@polydopamine nanocapsules for food preservation applications

A novel multifunctional soy protein isolate-carboxymethyl cellulose (SPI-CMC) based nanocomposite film was successfully prepared by introducing the polydopamine encapsulated essential oils (EOs@PDA) nanocapsules for food packaging. The EOs@PDA nanocapsules possessed smooth spherical morphology with good dispersion, and the particle size was about 283 nm. The influence of EOs@PDA nanocapsules on the physical, chemical and biological properties of EOs@PDA/SPI-CMC nanocomposite film was investigated. The EOs@PDA nanocapsules were crosslinked with SPI-CMC matrix and distributed uniformly in the matrix. The nanocomposite film with 1 wt% nanocapsules (EP/S-C) also showed excellent antioxidant activity (66.6 ± 0.3 % on DPPH and 98.6 ± 0.1 % on ABTS), superior UV-blocking properties (100 %), advanced antibacterial ability against E. coli and S. aureus, favorable biodegradability (>90 %) and relatively low In vitro cytotoxicity. Also, the EP/S-C nanocomposite film displayed potential to extend the shelf life of fresh cut apple slices (>24 h), perishable cherry tomatoes and blueberries (>6 days). The results suggested that the EOs@PDA/SPI-CMC nanocomposite film had a great possibility in the field of biodegradable and antimicrobial materials for food packaging.

Soy protein isolate-based active films functionalized with Zanthoxylum bungeanum by-products: Effects on barrier, mechanical, antioxidant and cherry tomato preservation performance

In this work, soy protein isolate (SPI)-based films enriched with naturally sourced Zanthoxylum bungeanum leaf extract (ZBLE) were prepared. Different ZBLE contents (0, 1, 3, 5, and 7 % w/w SPI) were incorporated into the SPI matrix to investigate the effect of ZBLE on various properties of the obtained films. ZBLE exhibited excellent compatibility with SPI in terms of tensile strength, water barrier properties, UV-light resistance capability, and antioxidant activities. The films with 5 % ZBLE addition presented the most comprehensive performance. The release of total phenolic compounds in two different aqueous food simulants was analyzed. Furthermore, the films were employed to preserve fresh cherry tomatoes at 25 ± 1 °C for 18 days. The changes in the physicochemical properties (mass loss rate, decay rate, and vitamin C content) of cherry tomatoes revealed that the addition of ZBLE to films significantly extended the storage time. Therefore, the SPI/ZBLE composite film has the potential as an eco-friendly active packaging material for food preservation.

Construction of protein-, polysaccharide- and polyphenol-based conjugates as delivery systems

Natural polymers, such as polysaccharides and proteins, have been used to prepare several delivery systems owing to their abundance, bioactivity, and biodegradability. They are usually modified or combined with small molecules to form the delivery systems needed to meet different needs in food systems. This paper reviews the interactions of proteins, polysaccharides, and polyphenols in the bulk phase and discusses the design strategies, coupling techniques, and their applications as conjugates in emulsion delivery systems, including traditional, Pickering, multilayer, and high internal-phase emulsions. Furthermore, it explores the prospects of the application of conjugates in food preservation, food development, and nanocarrier development. Currently, there are seven methods for composite delivery systems including the Maillard reaction, carbodiimide cross-linking, alkali treatment, enzymatic cross-linking, free radical induction, genipin cross-linking, and Schiff base chemical cross-linking to prepare binary and ternary conjugates of proteins, polysaccharides, and polyphenols. To design an effective target complex and its delivery system, it is helpful to understand the physicochemical properties of these biomolecules and their interactions in the bulk phase. This review summarizes the knowledge on the interaction of biological complexes in the bulk phase, preparation methods, and the preparation of stable emulsion delivery system.

Tea-break with epigallocatechin gallate derivatives - Powerful polyphenols of great potential for medicine

Epigallocatechin gallate (EGCG) is a polyphenol present in green tea (Camellia sinensis), which has revealed anti-cancer effects toward a variety of cancer cells in vitro and protective potential against neurodegenerative diseases such as Alzheimer's and Parkinson's. Unfortunately, EGCG presents disappointing bioavailability after oral administration, primarily due to its chemical instability and poor absorption. Due to these limitations, EGCG is currently not used in medication, but only as a dietary supplement in the form of green tea extract. Therefore, it needs further modifications before being considered suitable for extensive medical applications. In this article, we review the scientific literature about EGCG derivatives focusing on their biological properties and potential medical applications. The most common chemical modifications of epigallocatechin gallate rely on introducing fatty acid chains or sugar molecules to its chemical structure to modify solubility. Another frequently employed procedure is based on blocking EGCG's hydroxyl groups with various substituents. Novel derivatives reveal interesting properties, of which, antioxidant, anti-inflammatory, antitumor and antimicrobial, are especially important. It is worth noting that the most promising EGCG derivatives present higher stability and activity than base EGCG.

Preparation and characterization of egg white protein film incorporated with epigallocatechin gallate and its application on pork preservation

The aim of this study was to develop the composite films with antioxidant and biodegradable activity based on egg white protein (EWP) and epigallocatechin gallate (EGCG). Water susceptibility, light transmittance, microstructure and antioxidant properties of the composite films without and with EGCG were fully characterized. It was noted that the addition of EGCG might decrease the moisture content, water solubility and swelling capacity. SEM micrographs revealed that discontinuous blocks and rough surfaces were caused by increasing concentration of EGCG, whereas compact and homogeneous particles appeared when the concentration of EGCG reached to 80 μmol/L. Moreover, the biodegradability of the composite films was demonstrated by the soil degradation properties that they can be almost completely degraded within ten days. Experimental results on the application in chilled fresh pork showed that the EWP-based films could play an antioxidant role when incorporated with EGCG, indicating their great potential for food packaging.

Water-resistance chitosan film through enzymatic treatment and layer-by-layer assembly with bacterial cellulose for food packaging materials

The pervasive presence of plastic packaging has led to significant environmental contamination due to excessive reliance on petrochemicals and the inherent non-biodegradability of these materials. Both bacterial cellulose (BC) and chitosan (CT) films offer a promising option for food packaging purposes due to their sturdy mechanical strength, biodegradability, environmentally friendly manufacturing process, and non-toxic composition. However, the considerable moisture absorption capacity of these eco-friendly materials has hindered their extensive use, as it leads to a reduction in their strength and ability to serve as a barrier. In the present study, we introduced a composite material of BC reinforced with a lauryl gallate grafted CT coating. After grafting CT with lauryl gallate (CT-LG) through enzymatic modification, it showed excellent hydrophobic properties also in a green route of chemistry synthesis. Based on the results of the study, the duration of the water droplet test of the pure CT-LG film and BC coated with CT-LG (BC/CT-LG) films was more than 15 min, showing that water droplets can be completely blocked by the CT-LG coating without water penetration. For the mechanical properties, the wet flexural strength and wet tensile strength of BC/CT-LG films have improved 400% and 70% compared with the original BC. This method produces a composite material with enhanced hydrophobicity and green properties and shows great potential for use in drinking straws or packaging bags.

Chitooligosaccharide-catechin conjugate loaded liposome using different stabilising agents: characteristics, stability, and bioactivities

AIM

To determine the optimum condition for preparing chitooligosaccharide-catechin conjugate (COS-CAT) liposomes using different stabilising agents.

METHODS

COS-CAT liposomes (0.1-1%, w/v) were prepared using soy phosphatidylcholine (SPC) (50-200 mM) and glycerol or cholesterol (25-100 mg). Encapsulation efficiency (EE), loading capacity (LC), physicochemical characteristics, FTIR spectra, thermal stability, and structure of COS-CAT liposomes were assessed.

RESULTS

COS-CAT loaded liposome stabilised by cholesterol (COS-CAT-CHO) showed higher stability as shown by the highest EE (76.81%) and LC (4.57%) and the lowest zeta potential (ZP) (-76.51 mV), polydispersity index (PDI) (0.2674) and releasing efficiency (RE) (53.54%) (p < 0.05). COS-CAT-CHO showed the highest retention and relative remaining bioactivities of COS-CAT under various conditions (p < 0.05). FTIR spectra revealed the interaction between the choline group of SPC and -OH groups of COS-CAT. Phase transition temperature of COS-CAT-CHO was shifted to 184 °C, which was higher than others (p < 0.05).

CONCLUSION

SPC and cholesterol-based liposome could be used as a promising vesicle for maintaining bioactivities of COS-CAT.

Preparation of chitosan/Enoki mushroom foot polysaccharide composite cling film and its application in blueberry preservation

In this study, the composite cling film was prepared by solution casting method using chitosan and golden mushroom foot polysaccharide as substrates, and the structure and physicochemical indexes of the composite cling film were characterized by Fourier infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The results showed that compared with single chitosan film, the composite cling film has better mechanical properties and antioxidant properties, and the barrier of UV light and water vapor is also stronger. Due to its high nutritional value, blueberry has a short shelf life due to its thin skin and poor storage resistance. Therefore, in this study, blueberry was used as the object of freshness preservation, and the single chitosan film group and the uncovered group were used as controls, and the weight loss, total bacterial colony, decay rate, respiration intensity, malondialdehyde content, hardness, soluble solids, titratable acid, anthocyanin content, and VC content of blueberry were used as freshness preservation indexes for experiments. The comprehensive results showed that the freshness preservation effect of the composite film group was significantly higher than that of the control group, with better antibacterial properties, antioxidant properties, etc., which could effectively delay fruit decay and deterioration, thus prolonging the shelf life, and thus the chitosan/Enoki mushroom foot polysaccharide composite preservation film has a high potential as a new freshness preservation material for blueberry.

Antibacterial and antioxidant properties of phenolic acid grafted chitosan and its application in food preservation: A review

Chitosan is a bio-renewable natural polymeric material. The antibacterial and antioxidant activity of chitosan can be enhanced by grafting with phenolic acids to further expand its application in food. Therefore, this paper focuses on reviewing the structure, antimicrobial and antioxidant activities and their mechanisms with phenolic acid-g-CS, evaluating its cytotoxicity, and describing its application in various food preservation. In general, different reaction mechanisms of phenolic acid-g-CS synthesis lead to different product structures. Compared to chitosan, phenolic acid-g-chitosan exhibited enhanced antibacterial and antioxidant activities. The toxicity assessment showed that phenolic acid-g-CS is not cytotoxic. Moreover, phenolic acid-g-CS has been applied to a variety of food products such as fruits, vegetables and meat with good results. Overall, this review provides a certain reference for subsequent researchers to design phenolic acid-g-CS more rationally and for the subsequent development of phenolic acid-g-CS in food preservation.

Chitosan and chito-oligosaccharide: a versatile biopolymer with endless grafting possibilities for multifarious applications

Chito-oligosaccharides (COS), derived from chitosan (CH), are attracting increasing attention as drug delivery carriers due to their biocompatibility, biodegradability, and mucoadhesive properties. Grafting, the process of chemically modifying CH/COS by adding side chains, has been used to improve their drug delivery performance by enhancing their stability, targeted delivery, and controlled release. In this review, we aim to provide an in-depth study on the recent advances in the grafting of CH/COS for multifarious applications. Moreover, the various strategies and techniques used for grafting, including chemical modification, enzymatic modification, and physical modification, are elaborated. The properties of grafted CH/COS, such as stability, solubility, and biocompatibility, were reported. Additionally, the review detailed the various applications of grafted CH/COS in drug delivery, including the delivery of small drug molecule, proteins, and RNA interference therapeutics. Furthermore, the effectiveness of grafted CH/COS in improving the pharmacokinetics and pharmacodynamics of drugs was included. Finally, the challenges and limitations associated with the use of grafted CH/COS for drug delivery and outline directions for future research are addressed. The insights provided in this review will be valuable for researchers and drug development professionals interested in the application of grafted CH/COS for multifarious applications.

Composite films based on carboxy methyl cellulose and sodium alginate incorporated Thymus vulgaris purified leaves extract for food application: Assessment, antimicrobial and antioxidant properties

The current study was conducted to develop biodegradable films with matrix composed from carboxymethyl cellulose (CMC), sodium alginate (SA) and different concentrations from Thymus vulgaris purified leaves extract (TVE). The color properties, physical properties, shape of surface, manners of crystallinity, mechanical properties and thermal properties of produced films were investigated. The continuous addition of TVE up to 1.6 % inside films matrix imparted the yellow color of extract that increased opacity to 2.98 and reduced moisture, swelling, solubility and water vapor permeability (WVP) of films up to 10.31 %, 30.17 %, 20.18 % and (1.12× 10^-10 g.m^-1 s^-1 pa^-1), respectively. Furthermore, the surface micrographs showed smoother surface after using small concentrations of TVE and turned to irregular with rough surface at higher concentrations. The FT-IR analysis indicated typically bands that demonstrated physical interaction between TVE extract and CMC/SA matrix. The fabricated films showed suitable thermal stability with decreasing trend by incorporation of TVE inside CMC/SA films. Furthermore, the developed CMC/SA/TVE2 showed significant effects on preserving the levels of moisture content, titrable acidity, force to puncture and sensory properties of cheddar cheese during cold storage days compared with commercial packaging materials.

Effects of citric acid crosslinking on the structure and properties of ovotransferrin and chitosan composite films

In this study, ovotransferrin/chitosan (OVT/CS) composite films cross-linked by citric acid (CA) were prepared and the effects of CA cross-linking on the structure and physicochemical properties of the composite films were investigated. The cross-linking degree measured by 2,4,6-trinitrobenzenesulfonic acid (TNBS) method confirmed that CA was cross-linked with the matrix, and Fourier transform infrared spectroscopy confirmed that more hydrogen bonds and electrostatic interactions were formed between CA and the matrix. Differential scanning calorimetry, X-ray diffraction and Scanning electron microscope images revealed the compatibility between substances. The synergistic inhibition between the matrix results in a significantly higher antibacterial activity of the composite film than the pure film. Compared with uncross-linked films, the mechanical properties, barrier properties and water resistance of the cross-linked films were significantly improved. When the concentration of CA was 5 wt% (W/W, on a dry basis of the weight of OVT and CS), the most significant improvement in film performance was obtained. The tensile strength of the film increased from 32.05 MPa without cross-linking to 61.99 MPa and the swelling degree decreased from 51.5 % to 24.23 %. The observed phenomena suggest that cross-linking OVT and CS with CA can obtain functional edible films with improved properties.

Antioxidant packaging films developed by in-situ cross-linking chitosan with dialdehyde starch-catechin conjugates

In this study, four dialdehyde starch-catechin (DAS-catechin) conjugates were prepared by conjugating (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG) and (-)-epigallocatechin gallate (EGCG) with dialdehyde starch. Then, DAS-catechin conjugates were used as antioxidant and cross-linking agents to produce chitosan (CS) based antioxidant packaging films. The functionality of CS/DAS-catechin conjugate films was determined. Results showed four DAS-catechin conjugates formed Schiff-base linkages and hydrogen bond interactions with CS, resulting in improved film uniformity. Compared with plain CS film, CS/DAS-catechin conjugate films owned higher UV-vis light, water vapor and oxygen barrier ability, lower swelling degree, and stronger tensile strength, thermal stability and antioxidant activity. The cross-linking between CS and DAS-catechin conjugates delayed the biodegradable process of CS film. CS/DAS-catechin conjugate films showed good performance on inhibiting sunflower seed oil oxidation. Notably, CS/DAS-ECG conjugate film had the highest oxygen barrier, mechanical and antioxidant performances among four CS/DAS-catechin conjugate films. Therefore, CS/DAS-ECG conjugate film is an antioxidant packaging candidate for edible oil.

Polylactic Acid Film Coated with Electrospun Gelatin/Chitosan Nanofibers Containing Betel Leaf Ethanolic Extract: Properties, Bioactivities, and Use for Shelf-Life Extension of Tilapia Slices

Gelatin/chitosan solutions incorporated with betel leaf ethanolic extract (BLEE) at varying concentrations were electrospun on polylactic acid (PLA) films. Nanofibers with different morphologies, as indicated by scanning electron microscopy (SEM), were formed after solutions of gelatin/chitosan with and without BLEE were electrospun on PLA films at a constant voltage (25 kV) and a feed rate of 0.4 mL/h. Beaded gelatin/chitosan nanofibers (GC/NF) were found, particularly when high concentrations of BLEE were encapsulated. PLA films coated with GC/NF, and with BLEE added, showed antioxidant and antibacterial activities, which were augmented by increasing BLEE concentrations. Lower water vapor permeability and enhanced mechanical properties were achieved for GC/NF-coated PLA film (p < 0.05). Microbial growth and lipid oxidation of Nile tilapia slices packaged in PLA film coated with GC/NF containing 2% BLEE were more retarded than those packaged in low-density polyethylene (LDPE) bags over refrigerated storage of 12 days. Based on microbial limits, the shelf-life was escalated to 9 days, while the control had a shelf-life of 3 days. Therefore, such a novel film/bag could be a promising active packaging for foods.

Effect of chitosan/starch aldehyde-catechin conjugate composite coating on the quality and shelf life of fresh pork loins

BACKGROUND

Fresh pork is susceptible to oxidation and spoilage. Edible coating containing antioxidant and antimicrobial agents can create moisture and oxygen barriers around pork and inhibit oxidation and microbial growth in the pork. In this study, chitosan in combination with starch aldehyde-catechin conjugate (SACC) was used as a novel edible coating material for preserving fresh pork loins at chilled storage (4 ± 1 °C) for 14 days. Effect of chitosan/SACC composite coating on the quality of pork loins including weight loss, colour, pH value, microbial spoilage, lipid oxidation, protein oxidation, texture and sensory attributes during chilled storage was determined.

RESULTS

Chitosan and SACC had synergistic antioxidant and antimicrobial actions. As compared with uncoated and chitosan coated pork loins, chitosan/SACC coated pork loins showed lower weight loss (7.16%), pH value (5.99), total viable count (7.11 log CFU g^-1 ), total volatile base nitrogen content (130.2 mg kg^-1 ), lipid oxidation level (0.47 mg malondialdehyde kg^-1 ), protein oxidation level (0.047 mmol free thiol group g^-1 ) and shear force (27.40 N) on day 14. Meanwhile, chitosan/SACC composite coating effectively maintained the colour, micro-structure and sensory attributes of pork loins throughout chilled storage period. The shelf life of pork loins was extended from 8 days (uncoated samples) to 14 days by chitosan/SACC composite coating.

CONCLUSION

Chitosan/SACC composite coating effectively retarded the oxidation and spoilage of pork loins during chilled storage. © 2022 Society of Chemical Industry.

Chitosan based film reinforced with EGCG loaded melanin-like nanocomposite (EGCG@MNPs) for active food packaging

In this study, EGCG loaded melanin-like nanoparticles (EGCG@MNPs) were incorporated into chitosan matrix to prepare an active nanocomposite food packaging film, chitosan-EGCG@MNPs (CH-EM). The influence of EGCG@MNPs on the physical and biological properties of the chitosan film was investigated. The EGCG@MNPs nanoparticles were cross-linked with chitosan through intermolecular hydrogen bonds and uniformly distributed in the matrix. Besides, the incorporation of EGCG@MNPs tremendously improved the solubility, swelling ratio and water vapor barrier properties of the film, and permitted superior ultraviolet rays blocking property. In addition, the mechanical properties, thermal stability and surface hydrophobicity have also been significantly improved. The CH-EM^2.0 nanocomposite films also showed excellent oxidation resistance (58.4 ± 4.4%, DPPH and 92.4 ± 1.3%, ABTS⁺), and strong inhibitory ability against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The experimental results comprehensively showed that the prepared chitosan-EGCG@MNPs nanocomposite film offering excellent potential for eco-friendly active food packaging.

Chitosan/rice hydrolysate/curcumin composite film: Effect of chitosan molecular weight

The composite films were prepared by adding rice protein hydrolysate (RH) into chitosan (CH). Effect of four different chitosan molecular weights (MW, 0.8- 1.0, 30, 100, 300 kDa) was evaluated and curcumin was further incorporated into the film to enhance its bioactivities. With increasing MW (<100 kDa), moisture, solubility and water vapor transmission marginally decreased while tensile strength increased. Rice hydrolysate improved the film solubility and extensibility. All films showed extraordinary extensibility ranging from 180.26% to 204.08%. DSC confirmed MW did affect the thermal stability. The lower MW, the higher antioxidant activity of the CH/RH films. The 30 kDa CH/RH film exhibited higher antibacterial activity against both E. coli and S. aureus. Curcumin effectively improved both antibacterial and antioxidant activity of the CH/RH films. Hence, chitosan molecular weight must be chosen carefully according to its application and incorporation of protein hydrolysate into film would be an efficient strategy to modify film performance.

Molecular modifications, biological activities, and applications of chitosan and derivatives: A recent update

Polysaccharides arouse great interest due to their structure and unique properties, such as biocompatibility, biodegradability, and absence of toxicity. Polysaccharides from marine sources are particularly useful due to the wide variety of applications and biological activities. Chitosan, a deacetylated derivative of chitin, is an example of an interesting bioactive marine-derived polysaccharide. Moreover, a wide variety of chemical modifications and conjugation of chitosan with other bioactive molecules are responsible for improvements in physicochemical properties and biological activities, expanding the range of applications. An overview of the synthetic approaches for preparing chitosan, chitosan derivatives, and conjugates is described and discussed. A recent update of the biological activities and applications in different research fields, mainly focused on the last 5 years, is presented, highlighting current trends.

Production of chitosan-based biodegradable active films using bio-waste enriched with polyphenol propolis extract envisaging food packaging applications

Developing biodegradable active films has been a promising green approach to overcoming global concerns over the environmental pollution and human health caused by plastic utilization. This study aimed to develop active films based on chitosan (CS), produced from waste crayfish (Procambarus clarkii) shells enriched with bioactive extract (5-20%) of propolis (PS) and to characterize its properties, envisaging food packaging applications. The chromatographic profile of PS extract confirmed its richness, with 41 phenolic compounds. With increasing extract addition to the chitosan, the thickness of the films increased from 61.7 to 71.7 μm, causing a reduction in the light transmission rate, along with a greenish colour shift. The interactions between PS extract and CS was confirmed by infrared spectroscopy, at the same time that the microstructural integrity of the films was checked on the scanning electron microscopy micrographs. The findings also showed that addition of PS enhanced the films thermal stability and mechanical properties e.g., tensile modulus, yield strength, and stress at break. Besides, it improved the antioxidant and antimicrobial activities. Overall, CS-based composite films seem a promising green alternative to petroleum-based synthetic plastics allowing to extend the shelf life of food products due to their eco-friendly nature.

Functional Properties and Preservative Effect of P-Hydroxybenzoic Acid Grafted Chitosan Films on Fresh-Cut Jackfruit

In the present study, p-hydroxybenzoic acid-grafted chitosan (PA-g-CS) conjugates with different grafting degrees were synthesized by a free radical-regulated grafting approach. The conjugates were further developed into films by casting, and their characteristics and preservative effects on fresh-cut jackfruit were evaluated. Compared to the CS film, the PA-g-CS film showed comprehensive performance improvements, including enhancements of water solubility, anti-ultraviolet capacity, antioxidation, and antibacterial activity. Moreover, compared with CS film, some appreciable and favorable changes of physical properties were observed in the PA-g-CS films, which included water vapor permeability, oxygen permeability, surface morphology, moisture content, and mechanical intensity. Furthermore, compared to CS alone, the application of PA-g-CS films to fresh-cut jackfruit exerted a beneficial effect on the quality of products, as indicated by the inhibition of weight loss, softening, and membrane damage, the maintenance of soluble solids and ascorbic acids contents, as well as a reduced bacterial count and a higher sensory score. Among these PA-g-CS films, the best preservation effect was achieved with the highest degree of grafting (PA-g-CS III). The results suggested that the PA-g-CS film has the potential to be explored as a new type of packaging material for the preservation of fresh-cut fruits and vegetables.

Polyphenol-Polysaccharide Complex: Preparation, Characterization and Potential Utilization in Food and Health

Polysaccharides and polyphenols coexist in many plant-based food products. Polyphenol-polysaccharide interactions may affect the physicochemical, functional, and physiological properties, such as digestibility, bioavailability, and stability, of plant-based foods. In this review, the interactions (physically or covalently linked) between the selected polysaccharides and polyphenols are summarized. The preparation and structural characterization of the polyphenol-polysaccharide conjugates, their structural-interaction relationships, and the effects of the interactions on functional and physiological properties of the polyphenol and polysaccharide molecules are reviewed. Moreover, potential applications of polyphenol-polysaccharide conjugates are discussed. This review aids in a comprehensive understanding of the synthetic strategy, beneficial bioactivity, and potential application of polyphenol-polysaccharide complexes. Expected final online publication date for the Annual Review of Food Science and Technology, Volume 13 is March 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.