Effect of migration on the functionality of zinc oxide nanoparticle in polybutylene adipate terephthalate/thermoplastic starch films: A food simulant study.

Active packaging relies on controlled release of antimicrobials for food protection; however, uncontrolled migration due to environmental factors poses safety and functionality challenges. This study investigated the stability of zinc oxide nanoparticle (ZnONP) in poly(butylene-adipate-co-terephthalate)/thermoplastic starch (PBAT/TPS) biopolymer film for active food packaging applications. While incorporating ZnONP significantly enhanced the properties and active functionalities (UV-light blocking, antimicrobial activity) of PBAT/TPS film, food simulants posed significant stability challenges. Notably, exposure to 3 % acetic acid (acidic food simulant) triggered complete detachment and dissolution of ZnONPs from the film surface, leading to pore formation and subsequent internal ZnO dissolution. This resulted in dramatic alterations to the bionanocomposite films, including increased opacity, water vapor permeability, and decreased thermal stability, mechanical properties, and active functionalities. In contrast, 10 % ethanol (aqueous food simulant) had minimal impact, suggesting higher ZnO stability in neutral environments. Importantly, ZnO migration analysis revealed thresholds for safe application: 1 % ZnONP for acidic food contact and up to 5 % for aqueous foodstuffs. These findings highlight the critical role of environmental factors in ZnONP stability and emphasize the need for strategic optimization of ZnO content for achieving both functionality and safety in active biopolymer packaging.

Colorimetric Freshness Indicator Based on Cellulose Nanocrystal-Silver Nanoparticle Composite for Intelligent Food Packaging.

In this study, a colorimetric freshness indicator based on cellulose nanocrystal-silver nanoparticles (CNC-AgNPs) was successfully fabricated to offer a convenient approach for monitoring the quality of packaged food. AgNPs were directly synthesized and embedded in CNC via a one-pot hydrothermal green synthesis, and CNC-AgNP composited indicator films were prepared using a simple casting method. The AgNPs obtained were confirmed by UV-Vis diffuse reflectance spectroscopy and X-ray diffraction. The ability of the as-prepared CNC-AgNP film to indicate food quality was assessed in terms of the intensity of its color change when in contact with spoilage gases from chicken breast. The CNC-AgNP films initially exhibited a yellowish to dark wine-red color depending on the amount of AgNPs involved. They gradually turned colorless and subsequently to metallic grey. This transition is attributed to the reaction of AgNPs and hydrogen sulfide (H2S), which alters the surface plasmon resonance of AgNPs. Consequently, the color change was suitably discernible to the human eye, implying that the CNC-AgNP composite is a highly effective colorimetric freshness indicator. It can potentially serve as an accurate and irreversible food quality indicator in intelligent packaging during distribution or storage of products that emit hydrogen sulfide when deteriorating, such as poultry products or broccoli.

Effect of Repeated Contact to Food Simulants on the Chemical and Functional Properties of Nano ZnO Composited LDPE Films for Reusable Food Packaging.

The effect of repeated contact with food simulants on the properties and functionality of zinc oxide (ZnO) in nanocomposite films was investigated to examine possible safety hazards from the point of view of long-term use as food packaging. Low-density polyethylene (LDPE) embedded with 5 wt% nano-ZnO was immersed in distilled water, 50% ethanol, 4% acetic acid, and n-heptane. The cycle of immersion-rinse-dry was repeated up to 40 times for same sample under constant condition. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), field emission-scanning electron microscopy (FE-SEM), and UV-Vis spectroscopy analyses were performed to identify the changes in the chemical and functional properties of the nanocomposite film. Acetic acid had the greatest impact on the LDPE-ZnO nanocomposite films, while other food simulants caused little change. A new carboxylate bond was formed by the reaction of ZnO with acetic acid, as evidenced by the FTIR spectra. In addition, XRD and XAS confirmed the phase changes of nano-ZnO into zinc salts such as zinc hydroxy acetate or zinc acetate dihydrate. Furthermore, the light barrier property of the nanocomposite film drastically decreased, owing to the change in the bandgap of ZnO and film morphology.

A Facile Green Fabrication and Characterization of Cellulose-Silver Nanoparticle Composite Sheets for an Antimicrobial Food Packaging.

The present study focused on a facile and green approach for the one-step synthesis of silver nanoparticles (AgNPs) embedded in hard wood bleached kraft fiber. The hydroxyl groups on the cellulose chain induced ionic silver reduction with additional hydrothermal energy, allowing for the in situ formation and deposition of AgNPs on the cellulose fiber. The white color of the bleached fiber transformed to yellow due to the formation of AgNPs. UV-Vis spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy revealed that the AgNPs were uniformly distributed across the surface of the obtained cellulose fibers. The results indicated that the formation and distribution of AgNPs on surface of cellulose fibers was significantly influenced by the amount and concentration of silver nitrate (AgNO3). The antimicrobial activity of the cellulose-AgNP composite sheet against Escherichia coli was found to be inhibiting. These findings imply that cellulose-AgNP composite sheets can be feasibly used as antimicrobial paper for food packaging.

Optical response of photonic cellulose nanocrystal film for a novel humidity indicator.

Herein, an optical colorimetric sensor based on photonic cellulose nanocrystals (CNCs) was successfully developed to offer a convenient approach for measuring the qualitative index of high humidity (>85% RH). The addition of monovalent electrolyte (0.11 wt% NaCl) to CNC suspension before gelation enabled CNC film to bear consistent pinkish color, which is far better to readily reflect the visible color appeared as the pitch increases by water uptake. Further study of virtual reality simulation revealed that the increase of ambient humidity alters the color of photonic CNC film to be sufficiently observable either by optical instruments or human eyes. Under polarized optical microscope, CNC films appeared initially green and gradually turned to red color that is in agreement with red shift in UV-Vis absorption spectrum. Whereas, the reflected color change from pinkish to bluish was well-recognized by human eyes indicating photonic CNC is capable of being an effective colorimetric indicator. In a variable circumstance of low and high humidity, consecutive cycle test showed that the as-prepared indicator fully recovered to the original color in 30 min with 99.8% colorimetric response value. This film can be potentially used for an accurate and reversible humidity optical indicator in intelligent packaging for products that undergo deterioration along with high moisture, e.g., pharmaceutical products, cereals and grain seeds, and electronic parts, to monitor the quality during export or storage.

The green fabrication, characterization and evaluation of catalytic antioxidation of gold nanoparticle-lignocellulose composite papers for active packaging.

Gold nanoparticles (AuNPs) were directly synthesized and anchored on lignocellulose fiber without an external immobilizing agent via a facile green approach using unbleached kraft (UBK) softwood pulp. The obtained AuNPs were confirmed by UV-vis diffuse reflectance spectroscopy, field-emission scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The antioxidant behavior of the as-prepared AuNP-UBK fiber nanocomposite was evaluated by free radical scavenging of 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH). The nanocomposite fiber exhibited greatly enhanced radical scavenging activity compared to that of the pure fiber. As a consequence, AuNP-UBK nanocomposite paper showed exceptional antioxidant performance with a radical scavenging rate of over 98%, which is attributed to the synergistic effects of adsorption by the fiber-fiber network and subsequent catalytic activity of the AuNPs. This research indicated that AuNP-UBK fiber nanocomposites could be a new candidate for antioxidant active packaging for use in food preservation.

Applications of Nanomaterials in Food Packaging.

Nanomaterials have drawn great interest in recent years due to their extraordinary properties that make them advantageous in food packaging applications. Specifically, nanoparticles can impart significant barrier properties, as well as mechanical, optical, catalytic, and antimicrobial properties into packaging. Silver nanoparticles (AgNPs) and nanoclay account for the majority of the nano-enabled food packaging on the market, while others, such as nano-zinc oxide (ZnO) and titanium, share less of the current market. In current food packaging, these nanomaterials are primarily used to impart antimicrobial function and to improve barrier properties, thereby extending the shelf life and freshness of packaged food. On the other hand, there is growing concern about the migration of nanomaterials from food contact materials to foodstuffs and its associated potential risks. Indeed, insufficient data about environmental and human safety assessments of migration and exposure of nanomaterials are hindering their market growth. To overcome this barrier, the public believes that legislation from government agencies is critical. This review provides an overview of the characteristics and functions of major nanomaterials that are commonly applied to food packaging, including available and near- future products. Migration research, safety issues, and public concerns are also discussed.

Nano-food packaging: an overview of market, migration research, and safety regulations.

Recently, food packages produced with nanoparticles, "nano-food packaging," have become more available in the current market. However, although the use of nanomaterials is increasing in food packaging applications, concern over toxicity affects consumer perceptions and acceptance. Quite a number of commercialized forms of nano-food packaging are coated or composited product with inorganic materials, for example, nanosilver and nanoclay as representative examples. Several studies have shown the possibility of nanomaterial migration from packaging or containers to foodstuff. The debate is still ongoing among researchers about the extent of migration and whether it is negligible and safe. Government agencies and stakeholders must hurry to determine use limitations and release conclusive legislation and regulations as soon as possible since nano-food packaging may have great impacts on human health. This paper aims to review the availability of nano-food packaging in the current market, report case studies on nanomaterial migration, and present the current status of safety regulations and management of nano-food packaging in leading countries across regions. This review should enable governments and researchers to develop further nanomaterial risk assessment studies.

Photochemical synthesis, characterization and enhanced visible light induced photocatalysis of Ag modified TiO2 nanocatalyst.

Nanocomposite of titania (TiO2) and silver (Ag) has been synthesized by a photochemical deposition method. We investigated the simultaneous enhancement of visible light sensitivity and photocatalytic activities of as-prepared Ag-TiO2 nanocomposite photocatalyst. The resulting Ag-TiO2 nanomaterials were characterized by various analytical techniques including X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL). Photocatalytic activity was evaluated by decomposition of methylene blue (MB) dye solution under simulated visible light irradiation. Ag nanoparticles were well dispersed on the surface of TiO2 and composite nanoparticles were effectively enhanced in visible light-induced photocatalytic activity compared to that of Ag free TiO2. It was found that the enhanced activity is result from simultaneous effects of nano-Ag deposits by increasing the absorption capacity in visible region and by acting as electron trappers to promote charge separation of photoinduced electrons (e-) and holes (h+). The effect of the amount of Ag nanoparticles on its photoactivity under simulated visible light was also investigated.