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

Chitosan-metal and metal oxide nanocomposites for active and intelligent food packaging; a comprehensive review of emerging trends and associated challenges

In recent years, significant advancements in biopolymer-based packaging have emerged as a response to the environmental challenges posed by traditional petroleum-based materials. The drive for sustainable, renewable, and degradable alternatives to fossil-based components in the packaging industry has led to an increased focus on chitosan, the second most abundant biopolymer after cellulose. Chitosan offers intrinsic properties such as biodegradability, biocompatibility, antimicrobial activity, excellent barrier and film-forming capabilities, positioning it as an ideal candidate for food packaging applications. However, limitations including inferior mechanical, thermal, barrier properties, and brittleness compared to conventional plastics have limiting its widespread adoption in the food packaging industry. Chitosan has been extensively utilized in various forms, particularly as nanocomposites incorporating metal nanoparticles, leading to chitosan-based nanocomposite films/coatings that synergistically combine the advantageous properties of both chitosan and metal nanoparticles. Through an in-depth analysis of the current research (primarily the last 5 years), this review delves into the physicochemical, mechanical, sensing, and antimicrobial properties of chitosan nanocomposite as an innovative food packaging material. This review will provide insights into the potential toxicity and environmental impact of nanoparticle migration, as well as the prospects and challenges associated with chitosan-metal/metal oxide nanocomposite films in the development of sustainable packaging solutions.

Development and characterization of sustainable chitosan film enriched with ashwagandha extract as an alternative packaging material for enhancing shelf life of fresh-cut fruits

The current study aimed to develop biodegradable chitosan (Cs) films enriched with Ashwagandha (ASH) extract as an active packaging material to extend the shelf life of fresh-cut strawberries. The ASH extract, obtained through methanolic extraction, demonstrated significant antimicrobial and antioxidant activities, as confirmed by Gas Chromatography-Mass Spectrometry (GC-MS), which identified 12 bioactive compounds, including n-hexadecanoic acid (30.42%) and cis-13-octadecenoic acid (31.68%). The ASH loaded Cs films, prepared at varying concentrations of ASH extract, were characterized for surface morphology, water vapor transmission rate (WVTR), oxygen permeability (OP), and water contact angle (WCA). The films' hydrophilicity was improved with increasing ASH concentration, reducing the WCA from 112.4° (Cs) to 77.3° (ASH6/Cs). Antibacterial evaluation of the ASH3/Cs film revealed potent inhibition against Salmonella typhi (35.49 mm), Pseudomonas aeruginosa (34.85 mm), Bacillus subtilis (31.64 mm), Listeria monocytogenes (31.71 mm), and Candida albicans (29.25 mm). When tested over a 9-day storage period, the ASH3/Cs film effectively preserved fresh-cut strawberries, reducing microbial growth, weight loss, and decay compared to polyethylene (PE) packaging. These results highlight the potential of ASH3/Cs film as a sustainable and efficient alternative for food packaging, offering enhanced preservation and safety for perishable fruits.

Preparation and characterization of polyvinyl alcohol and chitosan composite film with cassia oil encapsulated in β-cyclodextrin and its application in fresh banana

In this study, composite films were developed by encapsulating cassia oil (CO) with β-cyclodextrin through a microencapsulation technique and incorporating it into a chitosan (CS), polyvinyl alcohol (PVA) and glycerol matrix. The primary objective of the film was to inhibit bacterial growth on the surface of fresh bananas and extend their shelf life. Characterization methods were employed to evaluate the physical properties and functionality of the composite films. FTIR, XRD, and SEM analyses demonstrated that cassia oil microcapsules (COM) were uniformly dispersed throughout the film and exhibited excellent compatibility with the matrix. The inclusion of 30 % COM improved the film's UV-blocking properties from 86.15 % to 91.03 %. Additionally, due to its hydrophobic nature, CO significantly reduced the water content to 9.02 % and 10.67 %. Furthermore, the COM enhanced the film's tensile strength from 21.18 MPa to 43.21 MPa, and increased its antioxidant capacity to 36.87 %. The results also indicated that 30 % COM significantly enhanced the film's antimicrobial activity against Escherichia coli and Staphylococcus aureus with inhibition zone diameters of 12.5 mm and 11.5 mm, while maintaining biosafety, as evidenced by unaltered cell survival rates in BEAS-2B and L02 cells. The film containing 30 % COM exhibited excellent preservation capacity for bananas, effectively extending their shelf life. These findings suggest that films containing COM have the potential to replace traditional plastic packaging in practical applications.

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.

Preparation and characterization of active packaging film containing chitosan/gelatin/brassica crude extract

Chitosan (CS), gelatin (GE), and brassica (BR) were utilized as the primary components to develop an active packaging film with outstanding properties. Active film-forming solutions were prepared using the solution casting method to produce these films. The resulting active films were characterized through various techniques, including X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared (FT-IR) spectroscopy, and light transmittance (T%), opacity, water solubility (WS), water vapour transmittance rate (WVTR), oxygen permeability (OP), mechanical properties, and antioxidant and antimicrobial properties. Orthogonal test results indicated that the optimal preparation ratio for the composite film was achieved with 2.5 g CS, 3.5 g GE, 6 g glycerol (GL) dissolved in distilled water. Under these conditions, the active packaging film exhibited excellent mechanical properties. In summary, the chitosan/gelatin/brassica crude extract-based active packaging film developed in this study presents a promising option for practical applications.

Effects of Ɛ-Polylysine Combined with Plant Extract on the Microbiological and Sensory Qualities of Grapes

Grapes are prone to rot and deterioration during storage, seriously affecting their food value. The effects of five extracts, cinnamon, perilla, green tea, pomegranate peel, and ginger, on the microbial growth, weight loss, and sensory quality of grapes were investigated using colony counting and sensory scoring methods. The results showed that perilla and cinnamon extracts had the best effect on maintaining the overall freshness of grapes on the 35th day of storage. The sensory scores were 82 and 80, respectively, and the number of microorganisms was below 6.13 log CFU/g. Further studies revealed that the combination of perilla and cinnamon extracts with Ɛ-polylysine resulted in better inhibition of microbial growth, reduced weight loss, maintained grape quality, and extended storage period to 40 days. An analysis of the active ingredients of the perilla and cinnamon extracts revealed that both extracts contained active antioxidant and antimicrobial ingredients, such as protocatechuic acid, coumaric acid, protocatechuic aldehyde, and rutin. The active ingredients of the perilla extract also included luteolin and apigenin, and those of the cinnamon extract included pinocembrin and epicatechin. These ingredients were deduced to have contributed to preserving the freshness of grapes by the plant extracts.

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.

Strong, tough, antibacterial, antioxidant, biodegradable multi-functional intelligent hydrogel film for real-time detection and maintenance of salmon freshness

In this study, we prepared a new multi-functional intelligent hydrogel preservation film using soy hull nanocellulose (SHNC), polyvinyl alcohol (PVA), chitosan (CS), and anthocyanin (Anth) as raw materials. The physicochemicals of the hydrogel preservation film, and its role in monitoring the freshness and freshness of salmon was evaluated. The results showed that the monomers were crosslinked by hydrogen, ester bonds, and electrostatic interactions in the hydrogel film, and there were three-dimensional pores in the hydrogel film. Meanwhile, SHNC/PVA/CS/Anth-3 exhibited excellent mechanical properties (elongation: 345.26 %; tensile strength: 26.84 MPa; compressive strength: 139.27 MPa) and excellent biodegradation performance. Additionally, the hydrogel film displayed excellent antioxidant and antibacterial properties (90.59 %). The preservation experiment showed that, at 4 °C, the hydrogel film could not only inhibit the growth and reproduction of bacteria on the surface of salmon meat, but it could also detect the freshness of salmon meat in real time, Meanwhile, the film could extend the shelf life of salmon meat from 6 d to 14 d. This study provides a new perspective for constructing a multi-functional intelligent hydrogel preservation film.

Silk protein: A novel antifungal and edible coating for strawberry preservation

In this study, an antimicrobial component, silk protease inhibitors (SPIs), was extracted from discarded silkworm cocoons, and a suitable degumming method for obtaining regenerated silk fibroin (SF) was screened. An edible antimicrobial coating was prepared by mixing SPIs with SF for evaluation of potential in strawberries preservation. Results demonstrated that SPI could effectively inhibit mycelial growth and spore germination. The alkaline protease method exhibited the highest degumming rate of 24.4 %. The SPI-SF coating exhibited excellent mechanical properties, high water vapor permeability, and easy washability. Within 10 days, seedlings treatment with SPI-SF coating solution showed a germination rate of 94.3 %, and exhibited good biocompatibility with HepG2 cells. Coating with SPI-SF led to increase in the storage period of strawberries to 10-14 days, concurrent with considerable reduction in decay rate at room temperature. Conclusively, this study demonstrates the potential of SPI-SF edible coating in strawberries preservation.

Chitosan-ginger essential oil nanoemulsions loaded gelatin films: A biodegradable material for food preservation

The alarming issue of food waste, coupled with the potential risks posed by petroleum-based plastic preservation materials to both the environment and human health necessitate innovative solutions. In this study, we prepared nanoemulsions (NEs) of chitosan (CS) and ginger essential oil (GEO) and systematically evaluated the effects of varying NEs concentrations (0, 10 %, 30 %, 50 %) on the physicochemical properties and biological activities of gelatin films. These films were subsequently applied to blueberry preservation. The scanning electron microscopy confirmed that the NEs were well-integrated with the Gel matrix, significantly enhancing the performance of the Gel films, including improvements of mechanical properties (tensile strength from 7.71 to 19.92 MPa; elongation at break from 38.55 to 113.65 %), thermal, and barrier properties (water vapor permeability from 1.52 × 10-9 to 6.54 × 10-10 g·m/Pa·s·m2). The films exhibited notable antibacterial and antioxidant activities due to the gradual release of GEO, thereby extending the storage life of blueberries. Moreover, the prepared composite films demonstrated excellent biodegradability and environmental friendliness, with the majority of the material decomposing within 30 days under soil microbial action. In conclusion, the active films loaded with NEs exhibit superior performance and hold significant potential for developing biodegradable materials for food preservation.

Application of chitosan in fruit preservation: A review

Fruit preservation after harvest is one of the key issues in current agriculture, rural areas, and for farmers. Using chitosan to keep fruits fresh, which can reduce the harm caused by chemical preservative residue to human health. It also helps avoid the disadvantages of the high cost of physical preservation and the challenges associated with difficult operation. This review focuses on the application progress of chitosan in fruit preservation. Studies have shown that chitosan inhibits the growth of bacteria and fungi, and delays fruit aging and decay. Furthermore, it can regulate the respiration and physiological metabolism of fruit, helping to maintain its quality and nutritional value. The preservation mechanism of chitosan includes its antibacterial properties, film-forming properties, and its effects on the physiological processes of fruit. However, in practical applications, issues such as determining the optimal concentration and treatment of chitosan still require further research and optimization.

Antimicrobial guar gum films optimized with Pickering emulsions of zein-gum arabic nanoparticle-stabilized composite essential oil for food preservation

In this study, composite essential oil Pickering emulsion stabilized with zein-gum arabic (GA) nanoparticles (ZGCEO) was prepared to improve the characteristics of guar gum (GG) films. ZGCEO exhibited commendable stability and compatibility with GG, while leading to a noticeable improvement in the light barrier (from 3.98 A mm-1 to 17.09 A mm-1) and water vapor barrier characteristics of GG films, concomitantly mitigating their hydrophilic nature, with decreasing moisture content (from 17.70 % to 10.50 %), water solubility (from 84.41 % to 71.79 %), water vapor permeability (from 5.64 × 10-11 g (m s Pa)-1 to 4.97 × 10-11 g (m s Pa)-1), and an increasing water contact angle (from 69.8° to 94.2°). The addition of 2 % ZGCEO yielded a notable increase in the tensile strength of the GG-ZGCEO films, but the elongation at break decreased with increasing ZGCEO concentration. Moreover, the incorporated ZGCEO demonstrated outstanding antioxidant and antimicrobial characteristics, featuring a slow-release behavior of essential oil. The GG-ZGCEO coating also showed an excellent preservation effect in pork and "Huangguan" pears during storage. Collectively, we substantiated the efficacy of ZGCEO in augmenting the functional attributes of GG films, thereby establishing their potential utility as antimicrobial packaging materials conducive to food preservation.

Chitosan-based sustainable packaging and coating technologies for strawberry preservation: A review

Strawberry fruits are popular all over the world due to their rich organoleptic properties and enormous health benefits. However, it is highly susceptible to postharvest spoilage due to various factors, including moisture loss, nutrient oxidation, and microbial spoilage. Recently, various researchers have studied the effect of chitosan-based flexible films and surface coatings on the shelf life of strawberries. Despite various reviews providing general information on the effects of chitosan-based films and coatings on various food products, no review has focused solely on their effects on postharvest preservation and the shelf life of strawberries. The purpose of this review is to summarize the current research on chitosan-based formulations for extending the shelf life of strawberries. Chitosan, a cationic carbohydrate polymer, possesses excellent properties such as film formation, mechanical strength, non-toxicity, biodegradability, edibility, UV-blocking ability, antioxidant activity, and antibacterial functionality, justifying its potential as packaging/coating material for fresh agricultural products, including strawberries. This review covers the various factors responsible for strawberry spoilage and the properties of chitosan that help counteract these factors. Additionally, the advantages of chitosan-based preservation technology compared to existing strawberry preservation methods were explained, efficiency was evaluated, and future research directions were suggested.

Incorporation of carbon dots into polyvinyl alcohol/corn starch based film and its application on shiitake mushroom preservation

Developing eco-friendly edible packaging films with multi-functional properties is highly required. This study involved synthesizing carbon dots (CDs) from dragon fruit, then incorporating them into a composite film based on polyvinyl alcohol (PVA)/corn starch (CS) to create a functional package to extend the shelf life of fresh shiitake mushrooms. Functional composite films with varying levels of CDs were formulated. The films' characteristics of morphology, mechanical properties, antioxidant properties, etc. were then determined, as well as their preservation effect on the fresh shiitake mushrooms. The results showed that the PVA/CS/CDs composite film showed excellent mechanical property, Ultraviolet (UV) barrier capability, antioxidant and antimicrobial properties. Specifically, addition of 8 mg/mL CDs in the composite films reduced weight loss of shiitake mushrooms by 30.74 %, decreased the decline in soluble solids content by 10.48 %, and halved the reduction in total sugar content after a 7-day storage period compared to films without added CDs. Furthermore, the films effectively lowered the respiratory intensity and browning of the mushrooms. This research demonstrates that CDs can serve as an effective component for the development of eco-friendly edible packaging films, as well as for their application in food preservation.

Modified Chitosan-Based Coating/Packaging Composites with Enhanced Antibacterial, Antioxidant, and UV-Resistant Properties for Fresh Food Preservation

Chitosan-based biomass packaging materials are a promising material for food preservation, but their limited solubility, antioxidant capacity, UV resistance, and mechanical properties severely restrict their application. In this study, we developed a novel chitosan-based coating/packaging composite (QCTO) using quaternary ammonium salt and tannic acid (TA)-modified chitosan (QCS-TA) and oxidized chitosan (OCS). The introduction of quaternary ammonium salt and TA effectively improves the water solubility and antibacterial, antioxidant, and UV-resistant properties of chitosan. The Schiff-base bond formed between OCS and QCS-TA, along with the TA-mediated multiple interactions, conferred the prepared composite film with good mechanical properties (69.9 MPa tensile strength) and gas barrier performance to water (14.3 g·h-1·m-2) and oxygen (3.5 g·mm·m-2·h-1). Meanwhile, the prepared QCTO composites demonstrate excellent biocompatibility and safety and are applied as coatings for strawberries and bananas as well as packaging films for mushrooms. These preservation experiments demonstrated that the prepared composites are able to effectively reduce weight loss, prevent microbial growth, maintain color, and significantly prolong the shelf life of fresh products (bananas, strawberries, and mushrooms extended shelf life by 6, 5, and 6 days, respectively). Therefore, the developed QCTO coating/packaging film shows great potential for applications in the field of food preservation and packaging.

Preparation and characterization of pectin/hydroxyethyl cellulose/clay/TiO2 bionanocomposite films for microbial pathogen removal from contaminated water

Some of conventional wastewater disinfectants can have a harmful influence on the environment as well as human health. The aim of this investigation was synthesis and characterizes ecofriendly pectin/hydroxyethyl cellulose (HEC)/clay and pectin/HEC/clay incorporated with titanium dioxide nanoparticles (TiO2NPs) and use the prepared bionanocomposite as microbial disinfectants for real wastewater. Pectin/HEC/clay and pectin/HEC/clay/TiO2 bionanocomposite were characterized by various methods including X-ray diffraction (XRD), scanning electron microscope (SEM), and Fourier-transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA). Mechanical properties and water vapor permeability (WVP) were carried out. The results of SEM showed that, the prepared bionanocomposite had a smooth surface. Additionally, TiO2 nanoparticles to the pectin/HEC/clay composites may lead to changes in the FTIR spectrum. The intensity of XRD peaks indicated that, TiO2NPs was small size crystallite. TGA illustrated that pectin has moderate thermal stability, while HEC generally exhibits good thermal stability. The TEM showed that, TiO2 nanoparticles have diameters <25 nm. On the other hand, antimicrobial activities of pectin/HEC/clay against Escherichia coli (E. coli), Staphylococcus aureus and Candida albicans have been enhanced by adding TiO2NPs. The minimum inhibitory concentration (MIC) of pectin/HEC/clay/TiO2 against E. coli was 200 mg/mL. Moreover, complete eradication of E. coli, Salmonella and Candida spp. from real wastewater was observed by using pectin/HEC/clay/TiO2 bionanocomposite. Finally, it can be concluded that, the synthesized bionanocomposite is environmentally friendly and considered an excellent disinfectant matter for removal of the microbial pathogens from wastewater to safely reuse.

Multifunctional konjac glucomannan/xanthan gum self-healing coating for bananas preservation

Damage to the integrity of the preservation coating on the fruit surface will seriously affect the shelf life of the fruit. In this work, the strong hydrogen bond interaction between xanthan gum (XG) and konjac glucomannan (KGM) could form hydrogel films with self-healing properties. The introduction of gallic acid (GA) was beneficial to further improve the antioxidant activity and UV shielding performance of the composite films. Surprisingly, the mechanical properties and gas (water vapor, O2 and CO2) barrier properties of the KGM film crosslinked by XG were significantly improved. The experiment of banana preservation showed that the composite coating could effectively delay the water loss and browning of bananas, slow down the decomposition of pectin and starch in the flesh, and extend the shelf life of bananas for >6 days. Therefore, this multifunctional coating is an excellent packaging material and has a very broad application prospect in the field of food preservation.

Preparation of modified chitosan-based nano-TiO2-nisin composite packaging film and preservation mechanism applied to chilled pork

Here, we developed a nano-TiO2-nisin-modified chitosan composite packaging film and investigated its properties and antibacterial activity, as well as its effect on chilled pork preservation time. The results indicated that the preservation time of chilled pork coated with a nano-TiO2-nisin-modified chitosan film (including 0.7 g/L nano-TiO2, irradiated with ultraviolet light for 40 min, and dried for 6 h) followed by modified atmosphere packaging (50% CO2 + 50% N2) increased from 7 to 20 days at 4 °C. Both nano-TiO2 and nisin enhanced the mechanical strength of the chitosan film, and nisin promoted nano-TiO2 dispersion and compatibility in chitosan. Treatment with 0.4 g/L nano-TiO2 for 60 min considerably inhibited spoilage bacteria, particularly Acinetobacter johnnii XBB1 (A. johnnii XBB1). As nano-TiO2 concentration and photocatalytic time increased, K+, Ca2+, and Mg2+ leakage in A. johnnii XBB1 increased but Na+/K+-ATPase and Ca2+/Mg2+-ATPase activities decreased. In A. johnnii XBB1, TiO2 significantly downregulated the expression of putrefaction-related genes such as cysM and inhibited cell self-regulation and membrane wall system repair. Therefore, our nano-TiO2-nisin-modified chitosan film could extend the shelf life without the addition of any chemical preservatives, demonstrating great potential for application in food preservation.

Properties of modified chitosan-based films and coatings and their application in the preservation of edible mushrooms: A review

Edible mushrooms are prone to deteriorate during storage. A Single chitosan film or coating has limitations in preservation. Therefore, this article focused on the improvement of modified chitosan-based films and coatings on properties related to storage quality of edible mushrooms (e.g.: safety, barrier, mechanical, antioxidant and antibacterial properties). Besides, the application of chitosan-based materials in the preservation of mushrooms was also discussed. The modified chitosan film and coating can slow down the respiration of mushrooms, inhibit the growth of microorganisms, protect antioxidant compositions, and regulate the activity of related enzymes, thus improving the quality and prolonging the shelf life of mushrooms. Meanwhile, the added ingredients improve the water and gas barrier properties of chitosan through volume and group occupation, and reduce the light transmittance of chitosan through light transmission, scattering and absorption. Essential oils and polyphenolic compounds had a better enhancement of antioxidant and antimicrobial properties of chitosan.

Degradable chitosan-based bioplastic packaging: Design, preparation and applications

Food packaging is an essential part of food transportation, storage and preservation. Biodegradable biopolymers are a significant direction for the future development of food packaging materials. As a natural biological polysaccharide, chitosan has been widely concerned by researchers in the field of food packaging due to its excellent film-forming property, good antibacterial property and designability. Thus, the application research of chitosan-based food packaging films, coatings and aerogels has been greatly developed. In this review, recent advances on chitosan-based food packaging materials are summarized. Firstly, the development background of chitosan-based packaging materials was described, and then chitosan itself was introduced. In addition, the design, preparation and applications of films, coatings and aerogels in chitosan-based packaging for food preservation were discussed, and the advantages and disadvantages of each research in the development of chitosan-based packaging materials were analyzed. Finally, the application prospects, challenges and suggestions for solving the problems of chitosan-based packaging are summarized and prospected.

Photocatalytic chitosan-based bactericidal films incorporated with WO3/AgBr/Ag and activated carbon for ethylene removal and application to banana preservation

Ethylene (C2H4) and pathogenic microorganisms are the two major causes of the deterioration of postharvest fruits and vegetables (F&V). Hence, the development of active packaging with C2H4 scavenging and bactericidal activities is urgently desirable. Herein, a novel photocatalytic active film (CS-PC-AC) is developed for banana preservation by incorporating WO3/AgBr/Ag photocatalyst (PC) and activated carbon (AC) into chitosan (CS). The fabricated PC is a ternary Z-scheme heterojunction and its high photocatalytic activity is achieved by the bridge of Ag between WO3 and AgBr through rapid transfer and separation of photogenerated electrons and holes. AC plays an indispensable role in the photocatalytic reaction through molecule adsorption and transport. PC and AC are hydrogen bonded with chitosan and their incorporation has slight effect on film's thermal stability but decreases the film's mechanical and barrier properties to some extent. CS-PC-AC exhibits strong bactericidal activity (killing ~100 % of Escherichia coli and Staphylococcus aureus within 3 h) and good C2H4 scavenging activity (C2H4 scavenging rate of 49 ± 2 %) under visible light irradiation, which can extend the banana shelf-life by at least 50 % at 25 °C. These results indicate the good perspective of CS-PC-AC in the delay of the deterioration of postharvest F&V.

Antibacterial Activity of Modified Sesbania Gum Composite Film and Its Preservation Effect on Wampee Fruit (Clausena lansium (Lour.) Skeels)

The primary challenges in fruit and vegetable preservation include extending storage duration while preserving sensory quality and nutritional value. In this study, sesbania gum (SG) was oxidized to prepare oxidized sesbania gum (OSG). An OSG/ZnO composite film was subsequently prepared, combining OSG, sodium carboxymethyl cellulose (CMC), and nano-zinc oxide (nano-ZnO). The preparation technology was determined via a response surface optimization experiment. When the addition amount of nano-ZnO exceeded 0.3 mg/mL, the composite films exhibited an antibacterial rate of over 90% against E. coli and S. aureus. For wampee (Clausena lansium (Lour.) Skeels) preservation, a OSG/ZnO-0.3 film was directly applied as a coating. The findings demonstrated favorable results in terms of the rate of rotting, soluble solids, and titrable acidity, effectively prolonging wampee fruit storage. This suggests the potential of an OSG composite film with nano-ZnO as a promising fruit packaging material, thereby expanding the application of SG and wampee fruit preservation.

Construction of a multifunctional dual-network chitosan composite aerogel with enhanced tunability

Typically, the tailorable versatility of biomass aerogels is attributed to the tunable internal molecular structure, providing broad application prospects. Herein, a simple and novel preparation strategy for developing multifunctional dual-network chitosan/itaconic acid (CSI) aerogel with tunability by using freeze-drying and vacuum heat treatment techniques. By regulating the temperature and duration of amidation reaction, electrostatic interactions between chitosan (CS) and itaconic acid (IA) was abstemiously converted into amide bond in frozen aerogel, with IA acting as an efficient in-situ cross-linking agent, which yielded CSI aerogels with different electrostatic/covalent cross-linking ratios. Heat treatment and tuning of the covalent cross-linking degree of CSI aerogel changed their microstructure and density, which led to enhanced performance. For example, the specific modulus of CSI1.5-160 °C-5 h (71.69 ± 2.55 MPa·cm3·g-1) increased by 119 % compared to that of CSI1.5 (32.73 ± 0.718 MPa·cm3·g-1), converting the material from superhydrophilic to hydrophobic (124° ± 3.6°), exhibiting favorable stability and heat transfer performance. In addition, part of -NH3+ of CS was retained in the electrostatic cross-linked network, endowing the aerogel with antibacterial properties. The findings of this study provide insights and a reliable strategy for fabricating biomass aerogel with good comprehensive performance via ingenious structural design and simple regulation methods.

Essential oils as green promising alternatives to chemical preservatives for agri-food products: New insight into molecular mechanism, toxicity assessment, and safety profile

Microbial food spoilage caused by food-borne bacteria, molds, and associated toxic chemicals significantly alters the nutritional quality of food products and makes them unpalatable to the consumer. In view of potential adverse effects (resistance development, residual toxicity, and negative effects on consumer health) of some of the currently used preservative agents and consumer preferences towards safe, minimally processed, and chemical-free products, food industries are looking for natural alternatives to the chemical preservatives. In this context, essential oils (EOs) showed broad-range antimicrobial effectiveness, low toxicity, and diverse mechanisms of action, and could be considered promising natural plant-based antimicrobials. The existing technical barriers related to the screening of plants, extraction methods, characterization, dose optimization, and unpredicted mechanism of toxicity in the food system, could be overcome using recent scientific and technological advancements, especially bioinformatics, nanotechnology, and mathematical approaches. The review focused on the potential antimicrobial efficacy of EOs against food-borne microbes and the role of recent scientific technology and social networking platform in addressing the major obstacles with EOs-based antimicrobial agents. In addition, a detailed mechanistic understanding of the antimicrobial efficacy of EOs, safety profile, and risk assessment using bioinformatics approaches are summarized to explore their potential application as food preservatives.

In Situ Fermentation of an Ultra-Strong, Microplastic-Free, and Biodegradable Multilayer Bacterial Cellulose Film for Food Packaging

Cellulose-based food packaging has a significant importance in reducing plastic pollution and also ensuring our safety from microplastics. Nonetheless, lignocellulose necessitates sophisticated physical and chemical treatments to be fashioned into a satisfactory food packaging, thus leading to extra consumption and operations. Here, we present a gel-assisted biosynthesis approach for the in situ production of bacterial cellulose (BC) that can be directly applied to food packaging. Komagataeibacter sucrofermentans is homogeneously distributed in the gellan gum (GG)-assisted culture system, and the BC/GG film with an even surface is attained. Then, the BC/GG film is integrated with an antibacterial layer containing a quaternary ammonium chitosan microsphere (QM) through an in situ spray biosynthesis method. The resulting BC/GG/QM multilayer film combines the barrier properties and antibacterial activity. The method for in situ biosynthesis is green, efficient, and convenient to endow the multilayer film with excellent barrier capacity (1.76 g·mm·m-2·d-1·KPa-1 at RH 75%), high mechanical properties (strength 462 MPa), and antibacterial activity (>90% against Escherichia coli O157:H7 and Staphylococcus aureus). In terms of food preservation, the overall performance of the BC/GG/QM multilayer film is better than the commercial petroleum-based film and lignocellulose-derived film. This work proffers a novel strategy to produce a more beneficial and eco-friendly multilayer film via in situ biosynthesis, which manifests great utility in the field of food packaging.