Preparation of a multifunctional silver nanoparticles polylactic acid food packaging film using mango peel extract

Green synthesized silver nanoparticles, a sustainable approach for fruit and vegetable preservation: An overview

Nanotechnology in which silver nanoparticles (AgNPs) have received more interest in fruits and vegetables (FaV) preservation due to their anti-microorganism properties. There are various approaches to synthesizing AgNPs, in which biological reduction, especially plant extraction containing bioactive compounds, is considered non-toxic, eco-friendly, and economically viable. AgNPs can be applied for FaV preservation by immersing or incorporating AgNPs into the edible coating or wrapper film. Depending on the type of coating and the kind of FaV, choosing the coating components is necessary to ensure the anti-microorganism ability and improve preservation efficiency. This review highlights green-synthesized AgNPs for preserving FaV. The study covered the materials employed in the green synthesis of AgNPs, their effectiveness against microorganisms, the influence of AgNPs on film structure, safety properties, and various preservation strategies. Using plant or bacterial-synthesized AgNPs in edible coatings offers a sustainable approach to enhance safety, edibility, environmental friendliness, and FaV quality during storage.

Surface Heterogeneity at the Polymer-Food Interface Influences Ag Migration from Plastic Packaging Incorporating Ag-Exchanged Zeolites

Silver-enabled polymers, with their antimicrobial properties, could prolong the shelf life and maintain quality in packaged foods. However, there is limited understanding about how the Ag form in the polymer, food chemistry, and other factors affect the transfer (migration) of Ag from the polymer to the food under the intended conditions of use. In this study, we investigated the release of Ag from polymer composites (PCs) incorporating two different Ag-exchanged zeolites (Ag-Y), which have been explored as potential scaffolds for loading high concentrations of Ag within common polymers. We manufactured two Ag-Y films based on low-density polyethylene (LDPE): one incorporating ionic Ag (Ag+) and one incorporating nanoparticulate Ag (AgNPs), each with similar initial Ag concentrations. Then, we assessed the migration of Ag out of these PCs into food simulants under accelerated room temperature storage conditions. In all simulants investigated, the Ag+-Y/LDPE film exhibited a higher migration of Ag compared to the AgNP-Y/LDPE film, suggesting a lower fraction of readily releasable Ag in the latter material. Total Ag migration from AgNP-Y/LDPE over 10 days at 40 °C was 11.10 ± 2.05 ng cm-2 of packaging surface area in water, 7.63 ± 1.59 ng cm-2 in a 9 wt % aqueous sucrose solution, and 21.29 ± 1.98 ng cm-2 in a commercial sweetened carbonated beverage (Squirt). In contrast, Ag migration from Ag+-Y/LDPE was measured at 49.61 ± 3.46, 57.48 ± 9.65, and 91.54 ± 5.58 ng cm-2 in water, sucrose solution, and Squirt drink, respectively. Surface characterization techniques, including atomic force microscopy (AFM), scanning electron microscopy (SEM), and conductivity measurements, revealed the presence of exposed zeolite particles at the surface of the films, suggesting that direct interactions between Ag-exchanged zeolites and food components at the simulant-polymer interface play an important role in determining Ag migration from Ag-Y/LDPE PCs.

Utilization of the waste aqueous phase from tea residue hydrothermal carbonization for preparing active food packaging films

Hydrothermal carbonization (HTC) is an effective strategy for high-value utilization of tea residue (TR), and it was noticed the aqueous phase (AP) has not been extensively studied. This study aimed to investigate the chemical components and characteristics of the AP, and applied it in active food packaging films. The results showed that the total phenolic content of AP was 1.86 mg GAE/mL, and the main compounds in AP were organic acids, alcohols, and amino acids. The AP showed excellent antibacterial activity and antioxidant capacity. The active films were prepared using the casting method. The 4:7-AP/PVA film showed outstanding mechanical properties (tensile strength = 34.18 MPa, elongation at break = 458.67%), antioxidant ability (DPPH scavenging capacity 92.01%), antibacterial activity, water resistance and biocompatibility. The banana preservation test showed the AP/PVA films could successfully prolong the shelf-life of bananas and have the potential to be food packaging films.

Nanotechnology in food packaging materials: role and application of nanoparticles

Global concerns about food security, driven by rising demand, have prompted the exploration of nanotechnology as a solution to enhance food supply. This shift comes in response to the limitations of conventional technologies in meeting the ever-increasing demand for food products. Consequently, nanoparticles play a crucial role in enhancing food production, preservation, and extending shelf life by imparting exceptional properties to materials. Nanoparticles and nanostructures with attributes like expansive surface area and antimicrobial efficacy, are versatile in both traditional packaging and integration into biopolymer matrices. These distinctive qualities contribute to their extensive use in various food sector applications. Hence, this review explores the physicochemical properties, functions, and biological aspects of nanoparticles in the context of food packaging. Furthermore, the synergistic effect of nanoparticles with different biopolymers, alongside its different potential applications such as food shelf-life extenders, antimicrobial agents and as nanomaterials for developing smart packaging systems were summarily explored. While the ongoing exploration of this research area is evident, our review highlights the substantial potential of nanomaterials to emerge as a viable choice for food packaging if the challenges regarding toxicity are carefully and effectively modulated.

Green synthesis of Poria cocos polysaccharides-silver nanoparticles and their applications in food packaging

To reduce pollution caused by traditional plastic packaging and preparation of silver nanoparticles (AgNPs), this work aims to develop biological macromolecular packaging films with green synthesized AgNPs. In this study, a novel P. cocos polysaccharide (PCP) with a unique monosaccharide composition was extracted from Poria cocos (Schw.) Wolf. Then, this polysaccharide containing 24.68 % rhamnose was used as a stabilizer for the green synthesis of PCP-AgNPs for the first time. PCP-AgNPs exhibited excellent antibacterial activity against P. aeruginosa, E. coli, and S. aureus, with the highest antibacterial activity against E. coli (inhibition zone diameter = 11.14 ± 0.79 mm). Subsequently, PCP-AgNPs/chitosan (CS) film was successfully prepared by incorporating PCP-AgNPs into the CS film solution. Several experiments demonstrated that the addition of this nanomaterial promoted the formation of noncovalent interactions between CS and PCP-AgNPs, resulting in a more regular and denser film. Compared to the CS film and control group, the PCP-AgNPs/CS film significantly maintained the quality indexes of strawberries. Therefore, this composite film successfully extended the shelf life of strawberries. Regarding safety, these packaging films were not cytotoxic toward RAW264.7 cells. In conclusion, the environmentally friendly PCP-AgNPs/CS film has the potential to replace some traditional food packaging materials.

Highly flexible carbon nitride-polyethylene glycol-cellulose acetate film with photocatalytic antibacterial activity for fruit preservation

Cellulose acetate film, as a biodegradable and biomass-derived material, has great potential applications in food packaging. However, the poor mechanical and antibacterial properties limit its applications. Herein, a highly flexible carbon nitride-polyethylene glycol-cellulose acetate (CN-PEG-CA) film was successfully prepared by combining graphitic carbon nitride (g-C3N4) photocatalyst with cellulose acetate (CA). The g-C3N4 enables the film with antibacterial activity, as a green photocatalyst. PEG softens the rigid polymer CA and crosslinks CA, PEG, and g-C3N4 together by hydrogen bonding, as a flexible crosslinker. X-ray diffractometer (XRD), scanning electron microscope (SEM), and Fourier transform infrared spectrum (FT-IR) characterizations confirmed the successful preparation of the CN-PEG-CA film. The mechanical property tests demonstrated that adding PEG increased the elongation at break of the film by about 4 times. The composite film had high antibacterial activity, and the bactericidal rates on Escherichia coli and Staphylococcus aureus were 99.98 % and 99.89 %, respectively. It effectively extended the shelf life of strawberries to 96 h and effectively maintained the quality of strawberries during storage. After 96 h, the weight loss rate of strawberries packaged with 15 % CN-PEG-CA film was 21.83 %, vitamin C content was 45.47 %, titratable acidity content was 0.89 %, and color, hardness and total soluble solids were well maintained. And biocompatibility test results showed that the film was safe and nontoxic. From the ecological and economic point of view, the highly flexible and biodegradable films with efficient photocatalytic antibacterial activity synthesized in this paper have great potential in the field of food packaging.

An antimicrobial film of silver/nanocellulose crystal/oxalic acid/polyvinyl alcohol with real-time bactericidal and prevention of biofilm formation properties

Silver nanoparticles (AgNPs) is an excellent antibacterial agent, which is widely used in medical, food, environmental and other fields, but AgNPs are easy to accumulate in aqueous solution, so their application in various fields is limited. Therefore, it is particularly important to propose a new application method or to prepare a new composite material. In this study, OA/PVA was obtained by cross-linking oxalic acid (OA) with polyvinyl alcohol (PVA). Then Ag/NCC was obtained by in situ reduction of AgNPs on nanocellulose crystals (NCC). Finally, Ag/NCC/OA/PVA composite antimicrobial films with good waterproofing effect were prepared by mixing Ag/NCC with OA/PVA. Subsequently, the films were characterized using SEM, UV-vis, FTIR and XRD, as well as physicochemical properties such as mechanical strength and hydrophilic properties were determined. The results indicated that the Ag/NCC/OA/PVA films possess good light transmittance, mechanical properties, water resistance, antibacterial activity, and biodegradability. The results of the mechanism study showed that Ag/NCC/OA/PVA films can destroy cell integrity, inhibit succinate dehydrogenase (SDH) activity, thereby reducing intracellular ATP levels. And induce a large number of reactive oxygen species (ROS) production, eventually leading to the death of C. sakazakii. In summary, Ag/NCC/OA/PVA film has good physical and chemical properties, antibacterial activity and biocompatibility, and has promising applications in food and medical antibacterial fields.

Fabrication of Schiff-base crosslinked films modified dialdehyde starch with excellent UV-blocking and antibacterial properties for fruit preservation

Starch-based films have received considerable attention, owing to their commendable biocompatible and biodegradable properties; however, their poor ultraviolet (UV)-blocking and antibacterial performances limit their application in fruit preservation. Herein, bio-based bifunctional benzoxazine (Bi-BOZ) compounds with different carbon chain lengths were synthesized, and the influence of chain lengths on the antibacterial effect was explored. Benzoxazine with 1,12-dodecanediamine as the amine source (BOZ-DDA) exhibited excellent antibacterial and antibiofilm activities, with minimum inhibitory concentrations of 21.7 ± 2.2 and 23.3 ± 2.6 μg/mL against Escherichia coli and Staphylococcus aureus, respectively, mainly because the electrostatic attraction and hydrophobic effect of BOZ-DDA, effectively disrupted the bacterial integrity. DS/DDA films with hydrophobic, antibacterial, and UV-resistant abilities were prepared by the Schiff-base reaction between BOZ-DDA and dialdehyde starch (DS). The interactions between the films increased with BOZ-DDA content, enhanced mechanical and barrier properties. DS/DDA films exhibited acid-responsive antibacterial activity attributed to the acid hydrolysis of Schiff bases, released of BOZ-DDA from the films, and the protonation of BOZ-DDA. DS/DDA films exhibited commendable antibacterial and anti-ultraviolet characteristics compared to commercially available films, allowing them to prevent the degradation of mangoes and grapes. As sustainable antibacterial materials, the multifunctional DS/DDA films manifest promising prospects in fruit preservation packaging applications.

Fabrication of antimicrobial and high-toughness poly (lactic acid) composite films using tung oil derivatives

Tung oil derivatives are promising alternatives to traditional toxic plasticizers for improving the toughness of poly (lactic acid) (PLA) films. In this study, a tung oil-based quaternary ammonium salt (Q-ETO) was synthesized using a multi-step process involving epoxidation, ring opening, and substitution reactions. PLA based composite films with various amounts of Q-ETO were prepared by solvent casting. The impact of various amount of Q-ETO on PLA/Q-ETO composite films were evaluated with regard to their mechanical properties, hydrophilicity, water vapor permeability, optical properties, thermal stability, antibacterial properties, and leaching properties. The PLA/5%Q-ETO composite film yielded the highest elongation at break (82.52 ± 9.53 %), which was 153.67 % higher than that of pure PLA. All PLA composite films showed an antibacterial efficiency exceeding 90 % against both S. aureus and E. coli. Moreover, the PLA/Q-ETO composite film blocked the transmission of both ultraviolet and visible light while preventing the permeation of water vapor. The addition of Q-ETO only weakly affected the color and thermal stability of the PLA/Q-ETO composite film. Given the numerous advantages of the PLA composite film, it has significant potential for application as a food packaging material.

Novel pH-responsive indicator films based on bromothymol blue-anchored chitin for shrimp freshness monitoring

The cellulose nanofibers (CNFs) based pH-sensitive indicator films were developed by mixing guar gum (GG) with bromothymol blue-anchored chitin (BTB-Chitin) as an indicator to monitor shrimp freshness. The BTB-Chitin was prepared by grafting hydroxypropyltriethylamine groups (HPTA) to chitin first, then anchoring bromothymol blue (BTB) to prepare intelligent pH response BTB-Chitin. The 0.08 BTB-Chitin films had a good tensile strength of 11.76 MPa and the water contact angle values were 125°, which displayed obvious color response to pH buffers and acid base volatile gas. Besides, the homogeneous and flexible composite films showed good color stability and reversibility. The released amount of BTB was very low from the BTB-Chitin films in heptane and corn oil. The composite films had been degraded completely in 15 days in soil. The pH and volatile base nitrogen were measured to determine the degree decay of shrimp (Litopenaeus vannamei), and the prepared pH-sensitive films changed from yellow (fresh) to cyan (spoiled) with the freshness of shrimp decreased, indicating the BTB-Chitin films could detect the shrimp freshness in real-time and high visibility.

Multifunctional polylactic acid biocomposite film for active food packaging with UV resistance, antioxidant and antibacterial properties

Antibacterial packaging used to control the growth of microorganisms in food is of great value for prolonging the shelf life of food. In this study, a bio-based antibacterial agent PDI based on zwitterionic and stereochemical synergistic antibacterial was designed and synthesized, and it was simultaneously introduced into polylactic acid (PLA) matrix with antioxidant o-vanillin (oVL) and plasticizer glycerol (GL). A series of PLA/oVL/PDI composite membranes with antibacterial, antioxidant and anti-ultraviolet properties were prepared by solution casting method. The results showed that the mechanical properties of the composite film were significantly improved compared with pure PLA (tensile strength increased by 37 %, elongation at break increased by 209 %), which was mainly attributed to the microphase separation structure induced by synthetic bio-based antibacterial agent, which improved the mechanical strength of PLA matrix, and the hydrogen bond formed by glycerol, o-vanillin and carbonyl group in PLA molecules plasticized PLA matrix. At the same time, the antibacterial rate of PLA/oVL/PDI composite membrane against Escherichia coli and Staphylococcus aureus can reach >95 %. Packaging experiments showed that PLA/oVL/PDI series composite films could effectively extend the shelf life of fresh bananas and apples for 5 days, and had great application prospects in preservative food packaging.

Smart Packaging Based on Polylactic Acid: The Effects of Antibacterial and Antioxidant Agents from Natural Extracts on Physical-Mechanical Properties, Colony Reduction, Perishable Food Shelf Life, and Future Prospective

Changes in consumer lifestyles have raised awareness of a variety of food options and packaging technologies. Active and smart packaging is an innovative technology that serves to enhance the safety and quality of food products like fruit, vegetables, fish, and meat. Smart packaging, as a subset of this technology, entails the integration of additives into packaging materials, thereby facilitating the preservation or extension of product quality and shelf life. This technological approach stimulates a heightened demand for safer food products with a prolonged shelf life. Active packaging predominantly relies on the utilization of natural active substances. Therefore, the combination of active substances has a significant impact on the characteristics of active packaging, particularly on polymeric blends like polylactic acid (PLA) as a matrix. Therefore, this review will summarize how the addition of natural active agents influences the performance of smart packaging through systematic analysis, providing new insights into the types of active agents on physical-mechanical properties, colony reduction, and its application in foods. Through their integration, the market for active and smart packaging systems is expected to have a bright future.

Development of active packaging film based on poly (lactic acid) incorporated with Piper betel leaf ethanolic extract and its application in the shelf-life extension of tuna meat

Active packaging films based on poly (lactic acid) (PLA) were developed by adding different concentrations (5 wt% and 10 wt%) of betel leaf (Piper betel) ethanolic extract (BLEE). The extract showed excellent antioxidant (80.2 %) and antimicrobial properties (18.05 and 16.05 mm against S. aureus and E. coli respectively). The films' structural, functional, and mechanical attributes were studied, along with their potential for extending the shelf life of tuna meat. The water solubility and water permeability were reduced with the incorporation of BLEE; while the tensile strength showed an inverse relationship with the concentration, 214.5 kg/cm2 (5 wt%), and to 307.6 kg/cm2 (10 wt%). The lipid oxidation in PLA-BLEE-packed tuna meat stored under refrigeration (7 days) showed a significant reduction, which could be attributed to the phenolic migration from the films. The new PLA-BLEE films with significant antibacterial and film attributes could be used in food packaging and to extend the shelf life of commodities that have been packaged.

Nanotechnology in Food and Plant Science: Challenges and Future Prospects

Globally, food safety and security are receiving a lot of attention to ensure a steady supply of nutrient-rich and safe food. Nanotechnology is used in a wide range of technical processes, including the development of new materials and the enhancement of food safety and security. Nanomaterials are used to improve the protective effects of food and help detect microbial contamination, hazardous chemicals, and pesticides. Nanosensors are used to detect pathogens and allergens in food. Food processing is enhanced further by nanocapsulation, which allows for the delivery of bioactive compounds, increases food bioavailability, and extends food shelf life. Various forms of nanomaterials have been developed to improve food safety and enhance agricultural productivity, including nanometals, nanorods, nanofilms, nanotubes, nanofibers, nanolayers, and nanosheets. Such materials are used for developing nanofertilizers, nanopesticides, and nanomaterials to induce plant growth, genome modification, and transgene expression in plants. Nanomaterials have antimicrobial properties, promote plants' innate immunity, and act as delivery agents for active ingredients. Nanocomposites offer good acid-resistance capabilities, effective recyclability, significant thermostability, and enhanced storage stability. Nanomaterials have been extensively used for the targeted delivery and release of genes and proteins into plant cells. In this review article, we discuss the role of nanotechnology in food safety and security. Furthermore, we include a partial literature survey on the use of nanotechnology in food packaging, food safety, food preservation using smart nanocarriers, the detection of food-borne pathogens and allergens using nanosensors, and crop growth and yield improvement; however, extensive research on nanotechnology is warranted.

Effect of Kaolin clay and Ficus carica mediated silver nanoparticles on chitosan food packaging film for fresh apple slice preservation

In this work, a novel antioxidant, antibacterial, and biodegradable food packaging film was elaborated, by incorporating natural kaolin clay (KC) and Ficus carica mediated silver nanoparticles (AgNPs) into Chitosan (Cht). A comparison of the physico-chemical and functional characteristics of the Cht/KC/AgNPs film was performed with those of Cht, Cht/KC, and Cht/AgNPs. SEM analysis showed a rough surface in the composite films containing KC particles because of their large diameter (50-120 μm) compared to AgNPs (20-80 nm). The FTIR analysis suggested that the interactions between Cht and AgNPs were stronger than those between Cht and KC. The tensile strength of Cht film increased from 16 MPa to ∼24 MPa in Cht/KC/AgNPs film. The introduction of KC and/or AgNPs considerably improved the light and moisture barrier capacity of the Cht film. The UV light transmittance decreased by 50 % for Cht film when incorporated by KC and AgNPs. Moreover, Cht/AgNPs was better in terms of antioxidant, antibacterial, and mechanical compared to Cht/KC, which was superior in biodegradability and water vapor barrier capacity. In particular, the Cht/KC/AgNPs film presented good barrier, antioxidants, antibacterial, mechanical, and biodegradable properties, owing to the synergistic effect between KC and AgNPs. For the packaging properties, all the films were tested for their ability to keep the freshness of apple slices as wrapping material. The films exhibited good results, and the Cht/KC/AgNPs showed promising performance regarding the moisture loss, browning index, total phenolic compound, and antioxidant activity of the apple slices. Moreover, the Cht/KC/AgNPs film exhibited a migration of silver meeting the standards set by EFSA and ECHA, which makes this film safe for food packaging.

Recent advances in biobased and biodegradable polymer nanocomposites, nanoparticles, and natural antioxidants for antibacterial and antioxidant food packaging applications

Inorganic nanoparticles (NPs) and natural antioxidant compounds are an emerging trend in the food industry. Incorporating these substances in biobased and biodegradable matrices as polysaccharides (e.g., starch, cellulose, and chitosan) and proteins has highlighted the potential in active food packaging applications due to more significant antimicrobial, antioxidant, UV blocking, oxygen scavenging, water vapor permeability effects, and low environmental impact. In recent years, the migration of metal NPs and metal oxides in food contact packaging and their toxicological potential have raised concerns about the safety of the nanomaterials. In this review, we provide a comprehensive overview of the main biobased and biodegradable polymer nanocomposites, inorganic NPs, natural antioxidants, and their potential use in active food packaging. The intrinsic properties of NPs and natural antioxidant actives in packaging materials are evaluated to extend shelf-life, safety, and food quality. Toxicological and safety aspects of inorganic NPs are highlighted to understand the current controversy on applying some nanomaterials in food packaging. The synergism of inorganic NPs and plant-derived natural antioxidant actives (e.g., vitamins, polyphenols, and carotenoids) and essential oils (EOs) potentiated the antibacterial and antioxidant properties of biodegradable nanocomposite films. Biodegradable packaging films based on green NPs-this is biosynthesized from plant extracts-showed suitable mechanical and barrier properties and had a lower environmental impact and offered efficient food protection. Furthermore, AgNPs and TiO₂ NPs released metal ions from packaging into contents insufficiently to cause harm to human cells, which could be helpful to understanding critical gaps and provide progress in the packaging field.

Poly (lactic acid)-based pH responsive membrane combined with chitosan and alizarin for food packaging

A poly (lactic acid) (PLA) -based functional partition composite membrane (PLA/CA) containing chitosan (CS) and alizarin (AL) was designed by solution casting method. The PLA/CA membrane contains the antibacterial zone of the edge part (PLA/CS) and the pH response detection zone of the central part (PLA/AL). At the same time, the environmentally friendly plasticizer tributyl citrate (TBC) was added to make the prepared PLA/CA composite membrane have good flexibility and high transparency. The results of FE-SEM and FTIR showed that CS and AL were uniformly dispersed in PLA matrix and had good compatibility with PLA. The antioxidant activities of PLA/CS and PLA/AL composite films were 43.3 % and 72.8 %, respectively. At the same time, the inhibitory rates of PLA/CS membrane against Escherichia coli and Staphylococcus aureus were as high as 87.91 % and 75.17 %, respectively. PLA/AL films exhibit excellent UV barrier properties. When the environmental pH (ammonia and acetic acid vapor) changed repeatedly, the PLA/AL membrane showed reversible color change of yellow under acidic condition and purple under alkaline condition. During the packaging and storage of chicken breast meat, the freshness of chicken breast meat can be detected by the color change of functional PLA/CA composite membrane.