Release of nanoclay and surfactant from polymer-clay nanocomposites into a food simulant

Enhanced antifungal properties of poly(butylene succinate) film with lignin nanoparticles and trans-cinnamaldehyde for mango packaging

Sustainable poly(butylene succinate) (PBS) films incorporating lignin nanoparticles (LN) and trans-cinnamaldehyde (CN) have been developed to preserve mango freshness and provide food safety. PBS/LN, PBS/CN, and PBS/LN/CN composite films were produced by blown film melt extrusion. This study investigated the effect of CN-LN on the CN remaining content, thermal, mechanical, and barrier properties, diffusion coefficient, and antifungal activity of PBS films both in vitro and in vivo. Results showed that LN in the PBS/LN/CN composite film contained more CN than in the PBS/CN film. The compatibility of CN-LN with PBS produced homogeneous surfaces with enhanced barrier properties. PBS/LN/CN composite films demonstrated superior antifungal efficacy, inhibiting the growth of Colletotrichum gloeosporioides and preserving mango quality during storage. Results suggested that incorporating LN into PBS composite films prolonged the sustained release of antifungal agents, thereby inhibiting microbial growth and extending the shelf life of mangoes. Development of PBS/LN/CN composite films is a beneficial step toward reducing food waste and enhancing food safety.

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.

Sulfides mediate the migration of nanoparticle mass out of nanocomposite plastics and into aqueous environments

We show that inorganic sulfides strongly influence transfer (migration) of nanoparticle mass out of polymer nanocomposites (PNCs) and into aqueous environments. We first manufactured two families of PNCs: one incorporating silver nanoparticles (AgNPs) and one incorporating CdSe quantum dots (QDs). Then, we assessed migration out of these PNCs and into aqueous media containing Na₂S at concentrations ranging from 0 to 10^-4 M. Results show that Na₂S strongly suppressed migration of Ag from AgNP-based PNCs: the migration into water spiked with 10^-6 M Na₂S was 79% less than migration into water without Na₂S, and no migration was detected (LOD ≈ 0.01 ng/cm²) in water spiked with Na₂S at 10^-5 M or 10^-4 M. With CdSe QD-based PNCs, Na₂S suppressed Cd migration but enhanced Se migration, resulting in only a small net effect on the total QD migration but a large shift of the leachate composition (from favoring Cd by an average of 5.8 to 1 in pure water to favoring Se 9.4 to 1 when Na₂S was present at 10^-4 M). These results show that common inorganic substances like sulfides may play a strong role in determining the environmental fate of polymer-dispersed nanoparticles and imply that migration tests conducted in purified water may not always accurately reflect migration into real environments.

Effect of Organic Modifier Types on the Physical-Mechanical Properties and Overall Migration of Post-Consumer Polypropylene/Clay Nanocomposites for Food Packaging

The deterioration of the physical-mechanical properties and loss of the chemical safety of plastics after consumption are topics of concern for food packaging applications. Incorporating nanoclays is an alternative to improve the performance of recycled plastics. However, properties and overall migration from polymer/clay nanocomposites to food require to be evaluated case-by-case. This work aimed to investigate the effect of organic modifier types of clays on the structural, thermal and mechanical properties and the overall migration of nanocomposites based on 50/50 virgin and recycled post-consumer polypropylene blend (VPP/RPP) and organoclays for food packaging applications. The clay with the most hydrophobic organic modifier caused higher thermal stability of the nanocomposites and greater intercalation of polypropylene between clay mineral layers but increased the overall migration to a fatty food simulant. This migration value was higher from the 50/50 VPP/RPP film than from VPP. Nonetheless, clays reduced the migration and even more when the clay had greater hydrophilicity because of lower interactions between the nanocomposite and the fatty simulant. Conversely, nanocomposites and VPP/RPP control films exhibited low migration values in the acid and non-acid food simulants. Regarding tensile parameters, elongation at break values of PP film significantly increased with RPP addition, but the incorporation of organoclays reduced its ductility to values closer to the VPP.

(Bio)nanotechnology in Food Science-Food Packaging

Background: Bionanotechnology, as a tool for incorporation of biological molecules into nanoartifacts, is gaining more and more importance in the field of food packaging. It offers an advanced expectation of food packaging that can ensure longer shelf life of products and safer packaging with improved food quality and traceability. Scope and approach: This review recent focuses on advances in food nanopackaging, including bio-based, improved, active, and smart packaging. Special emphasis is placed on bio-based packaging, including biodegradable packaging and biocompatible packaging, which presents an alternative to most commonly used non-degradable polymer materials. Safety and environmental concerns of (bio)nanotechnology implementation in food packaging were also discussed including new EU directives. Conclusions: The use of nanoparticles and nanocomposites in food packaging increases the mechanical strength and properties of the water and oxygen barrier of packaging and may provide other benefits such as antimicrobial activity and light-blocking properties. Concerns about the migration of nanoparticles from packaging to food have been expressed, but migration tests and risk assessment are unclear. Presumed toxicity, lack of additional data from clinical trials and risk assessment studies limit the use of nanomaterials in the food packaging sector. Therefore, an assessment of benefits and risks must be defined.

Food and Beverage Ingredients Induce the Formation of Silver Nanoparticles in Products Stored within Nanotechnology-Enabled Packaging

Nanotechnology-based packaging may improve food quality and safety, but packages manufactured with polymer nanocomposites (PNCs) could be a source of human dietary exposure to engineered nanomaterials (ENMs). Previous studies showed that PNCs release ENMs to foods predominantly in a dissolved state, but most of this work used food simulants like dilute acetic acid and water, leaving questions about how substances in real foods may influence exposure. Here, we demonstrate that food and beverage ingredients with reducing properties, like sweeteners, may alter exposure by inducing nanoparticle formation in foods contacting silver nanotechnology-enabled packaging. We incorporated 12.8 ± 1.4 nm silver nanoparticles (AgNPs) into polyethylene and stored media containing reducing ingredients in packages manufactured from this material under accelerated room-temperature and refrigerated conditions. Analysis of the leachates revealed that reducing ingredients increased the total silver transferred to foods contacting PNC packaging (by as much as 7-fold) and also induced the (re)formation of AgNPs from this dissolved silver during storage. AgNP formation was also observed when Ag⁺ was introduced to solutions of natural and artificial sweeteners (glucose, sucrose, aspartame), commercial beverages (soft drinks, juices, milk), and liquid foods (yogurt, starch slurry), and the amount and morphology of reformed AgNPs depended on the ingredient formulation, silver concentration, storage conditions, and light exposure. These results imply that food and beverage ingredients may influence dietary exposure to nanoparticles when PNCs are used in packaging applications, and the practice of using food simulants may in certain cases underpredict the amount of ENMs likely to be found in foods stored in these materials.

Nanotechnology-based approaches for food sensing and packaging applications

The rapid advancement of nanotechnology has provided opportunities for the development of new sensing and food packaging solutions, addressing long-standing challenges in the food sector to extend shelf-life, reduce waste, assess safety and improve the quality of food. Nanomaterials can be used to reinforce mechanical strength, enhance gas barrier properties, increase water repellence, and provide antimicrobial and scavenging activity to food packaging. They can be incorporated in chemical and biological sensors enabling the design of rapid and sensitive devices to assess freshness, and detect allergens, toxins or pathogenic contaminants. This review summarizes recent studies on the use of nanomaterials in the development of: (1) (bio)sensing technologies for detection of nutritional and non-nutritional components, antioxidants, adulterants and toxicants, (2) methods to improve the barrier and mechanical properties of food packaging, and (3) active functional packaging. The environmental, health and safety implications of nanomaterials in the food sector, along with an overview of regulation and consumer perception is also provided.

The advancement of nanotechnology has provided opportunities for the development of new sensing and food packaging solutions, addressing long-standing challenges to extend shelf-life, reduce waste, assess safety and improve the quality of food.

Comparison of properties and aquatic arsenic removal potentials of organically modified smectite adsorbents

Arsenic (As) poses a tremendous threat to human health due to exposure through arsenic-contaminated drinking water and/or food. We aimed to develop organically modified clay adsorbents for the removal of As from aqueous solution. We modified a smectite sample using three organic agents, namely hexadecyl trimethylammonium (HDTMA), chitosan and citric acid, and characterized the products using X-ray diffraction, infrared spectroscopy, and scanning electron microscopy techniques. The characterization techniques suggested successful organic modifications of the smectite sample. The surfactant-modified smectite was the most efficient (66.9%) As removing adsorbent with a maximum adsorption capacity of 473.2 μg g^-1. Kinetic study showed that the adsorbents reached As adsorption equilibrium within 3 h, and the data fitted reasonably well to power function and simple Elovich equations (R² > 0.89). The adsorption data were explained well by the Freundlich and Sips isothermal models. The surfactant-modified and chitosan-grafted organoclays adsorbed As by electrostatic attraction and anion exchange, whereas the citric acid activated smectite followed ligand exchange and simple anion exchange mechanisms. This study thus demonstrated the potential of surfactant-modified clays in removing As from contaminated waters.

Migration of Quaternary Ammonium Cations from Exfoliated Clay/Low-Density Polyethylene Nanocomposites into Food Simulants

Clay/polymer nanocomposites (CPNs) are polymers incorporating refined clay particles that are frequently functionalized with quaternary ammonium cations (QACs) as dispersion aids. There is interest in commercializing CPNs for food contact applications because they have improved strength and barrier properties, but there are few studies on the potential for QACs in CPNs to transfer to foods under conditions of intended use. In this study, we manufactured low-density poly(ethylene) (LDPE)-based CPNs and assessed whether QACs can migrate into several food simulants under accelerated storage conditions. QACs were found to migrate to a fatty food simulant (ethanol) at levels of ∼1.1 μg mg^-1 CPN mass after 10 days at 40 °C, constituting about 4% total migration (proportion of the initial QAC content in the CPN that migrated to the simulant). QAC migration into ethanol was ∼16× higher from LDPE containing approximately the same concentration of QACs but no clay, suggesting that most QACs in the CPN are tightly bound to clay particles and are immobile. Negligible QACs were found to migrate into aqueous, alcoholic, or acidic simulants from CPNs, and the amount of migrated QACs was also found to scale with the temperature and the initial clay concentration. The migration data were compared to a theoretical diffusion model, and it was found that the diffusion constant for QACs in the CPN was several orders of magnitude slower than predicted, which we attributed to the potential for QACs to migrate as dimers or other aggregates rather than as individual ions. Nevertheless, the use of the migration model resulted in a conservative estimate of the mass transfer of QAC from the CPN test specimens.

Interaction of nanoclay-reinforced packaging nanocomposites with food simulants and compost environments

The production of engineered nanomaterials (ENMs) has increased exponentially over the last few decades. ENMs, made from use of engineered nanoparticles (ENPs), have been applied to the food, agriculture, pharmaceutical, and automobile industries. Of particular interest are their applications in packaging nanocomposites for consumer and non-consumer goods. ENPs in nanocomposites are of interest as a packaging material because they reduce the amount of polymer needed, while improving the physical properties. However, the transformation of ENPs in nanocomposite production, their fate, and their toxicity remain unknown while in contact with the package content or after the end of life. The objectives of this chapter are (a) to provide an overview of the main nanoclays used in packaging; (b) to categorize the main polymeric packaging nanocomposites; (c) to provide an overview of the fate and mass transport of ENPs, especially nanoclays; (d) to describe the mass transfer of nanoclays in food simulants and in compost environments; and (e) to identify current and future research needs.

Characterization of a green nanocomposite prepared from soluble soy bean polysaccharide/Cloisite 30B and evaluation of its toxicity

The present paper aims to elucidate the structural, thermal and mechanical properties of soybean polysaccharide (SSPS)/Cloisite 30B. Tensile strength of the nanocomposite films improved with incorporation of nanoparticles, whereas elongation at break decreased. Surface roughness of the samples increased with the addition of nanoclay. Neat SSPS film and SSPS-1% Cloisite 30B had a relatively smooth surface with no irregularities, while for the samples containing 3 and 7% Cloisite 30B, the surface was rough. DSC analysis demonstrated that following an increase in nanoparticles content, the melting temperature of the nanocomposite elevated, whereas, glass transition temperature decreased. The results of antibacterial activity indicated that Cloisite 30B could inhibit the growth of Salmonella typhi PTCC 1609, Staphylococcus epidermis PTCC 1114 (ATCC 12228) and Listeria monocytogenes PTCC 1165. SSPS-Cloisite 30B nanocomposite could not inhibit the growth of Aspergillus niger. The results demonstrated that the migration of nanoparticles might happen into deionized water as a food simulant, but they could not migrate into bread as a food model. Furthermore, it was found that Cloisite 30B nanoparticles had cytotoxicity effect, and thus, it is recommended that Cloisite 30B/SSPS nanocomposites be used only for the packaging of solids foods such as bread.

Influence of Different Acids on the Transport of CdSe Quantum Dots from Polymer Nanocomposites to Food Simulants

We fabricated polymer nanocomposites (PNCs) from low-density polyethylene and CdSe quantum dots (QDs) and used these materials to explore potential exposure after long-term storage in different acidic media that could be encountered in food contact applications. While the low-level release of QD-associated mass into all the food simulants was observed, exposure to dilute acetic acid resulted in more than double the mass transfer compared to that which occurred during exposure to dilute hydrochloric acid at the same pH. Conversely, exposure to citric acid resulted in a suppression of QD release. Permeation experiments and confocal microscopy were used to reveal mechanistic details underlying these mass-transfer phenomena. From this work, we conclude that the permeation of undissociated acid molecules into the polymer, limited by partitioning of the acids into the hydrophobic polymer, plays a larger role than pH in determining exposure to nanoparticles embedded in plastics. Although caution must be exercised when extrapolating these results to PNCs incorporating other nanofillers, these findings are significant because they undermine current thinking about the influence of pH on nanofiller release phenomena. From a regulatory standpoint, these results also support current guidance that 3% acetic acid is an acceptable acidic food simulant for PNCs fabricated from hydrophobic polymers because the other acids investigated resulted in significantly less exposure.

Carbon nanotube release from polymers into a food simulant

The release assessment of multi-walled carbon nanotubes (CNTs) was performed on two types of polymer-CNT nanocomposites: polypropylene (PP) and polyamide 6 (PA6) containing 3 wt% CNT. Nanocomposite films were prepared and then exposed to ethanol as a fatty-food simulant at 40 °C, and the amount of CNT release into ethanol was determined by ultraviolet-visible spectroscopy (UV-Vis) and graphite furnace atomic absorption spectrometry (GFAAS). The CNTs released into ethanol were visualized by transmission electron microscopy (TEM) and verified by Raman spectroscopy. UV-Vis analysis showed a very small amount of CNT release from the nanocomposite films into ethanol over 60 d: maximum CNT concentrations in ethanol were 1.3 mg/L for the PP-CNT film and 1.2 mg/L for the PA6-CNT film. GFAAS results indicated that the amount of CNTs released into ethanol after 12 d was over 20-fold higher than the results obtained by UV-Vis. Overestimation of CNT release by GFAAS suggested aggregation and poor dispersion of CNTs in the solvent. This assumption was verified by TEM images exhibiting the embedded CNTs in the polymer flakes, which could be poorly dispersed in the solvent. In general, CNT release from the nanocomposite films was considered a surface phenomenon, as indicated by detachment of CNT-containing polymer flakes from the film surface.

Effect of organic additives on silver release from nanosilver-polyethylene composite films to acidic food simulant

The effects of organic additives (Irgafos 168, Irganox 1076, Tinuvin 622, Chimassorb 944, UV-P, and UV-531) on silver release from nanosilver-polyethylene composite films into an acidic food simulant (3% acetic acid) were investigated using inductively coupled plasma mass spectrometry. The limits of detection and quantification, coefficient of determination, and recoveries of the method used were 3.7ngL^-1, 12.4ngL^-1, 0.999, and 89-113%, respectively. The results indicated that additives can affect silver release via two simultaneous processes: (i) reactions between organic additives and silver that promote silver release from the composite film to the acidic food simulant; and (ii) the promotion or inhibition of silver release by affecting silver oxidation. High temperature and humidity treatment of the composite films was found to significantly increase silver release by promoting silver oxidation.

Environmental release of core-shell semiconductor nanocrystals from free-standing polymer nanocomposite films

Concomitant with the development of polymer nanocomposite (PNC) technologies across numerous industries is an expanding awareness of the uncertainty with which engineered nanoparticles embedded within these materials may be released into the external environment, particularly liquid media. Recently there has been an interest in evaluating potential exposure to nanoscale fillers from PNCs, but existing studies often rely upon uncharacterized, poor quality, or proprietary materials, creating a barrier to making general mechanistic conclusions about release phenomena. In this study we employed semiconductor nanoparticles (quantum dots, QDs) as model nanofillers to quantify potential release into liquid media under specific environmental conditions. QDs of two sizes were incorporated into low-density polyethylene by melt compounding and the mixtures were extruded as free-standing fluorescent films. These films were subjected to tests under conditions intended to accelerate potential release of embedded particles or dissolved residuals into liquid environments. Using inductively-coupled plasma mass spectrometry and laser scanning confocal microscopy, it was found that the acidity of the external medium, exposure time, and small differences in particle size (on the order of a few nm) all play pivotal roles in release kinetics. Particle dissolution was found to play a major if not dominant role in the release process. This paper also presents the first evidence that internally embedded nanoparticles contribute to the mass transfer, an observation made possible via the use of a model system that was deliberately designed to probe the complex relationships between nanoparticle-enabled plastics and the environment.

Development of new active packaging film made from a soluble soybean polysaccharide incorporating ZnO nanoparticles

This study aimed to develop a soluble soybean polysaccharide (SSPS) nanocomposite incorporating ZnO nanoparticles. The nanocomposites were prepared using the solvent-casting method. SEM, AFM, DSC and X-ray diffraction methods were applied to characterize the resulting films. Furthermore, the antibacterial and anti-mold activities of SSPS/ZN films were assessed against the selected microorganisms. The results indicated that incorporating ZNs into the SSPS film affected the tensile strength and elongation at break significantly. In addition, the antibacterial, antifungal and yeasticidal activities of ZnO/SSPS films have been approved. XRD results showed a crystal plane of hexagonal ZN, while SEM showed that there was not a good affinity between ZN and SSPS. Mono-dispersed particles with clearly spherical morphology and with no voids on the surface were observed using AFM. Fluctuation in Tg and Tm resulted from incorporating ZN. In summary, the potential of ZNs as a functional filler in SSPS film has been demonstrated.

Novel Active Surface Prepared by Embedded Functionalized Clays in an Acrylate Coating

The research on a self-decontaminating surface has received significant attention because of the growth of pathogenic microorganisms on surfaces. In this study, a novel and simple technique for producing an active surface with antimicrobial functionality is demonstrated. A tethering platform was developed by grafting the biocide ampicillin (Amp) to a nanoclay and dispersing the nanoclay in a UV-curable acrylate coating applied on polypropylene films as the substrate. A coupling agent, [3-(glycidyloxy)propyl]trimethoxysilane, was used as a linker between the nanoclay and Amp. The Amp-functionalized clay was further modified with an organic surfactant to improve the compatibility with the coating. Several characterization assays, such as Fourier infrared transform analysis, thermogravimetric analysis, and X-ray diffraction, were conducted to confirm the presence of Amp in the nanoclay. Transmission electron microscopy images revealed that the clay particles were well dispersed in the coating and had a partial exfoliated morphology. The active coating surface was effective in inhibiting the growth of Gram-positive Listeria monocytogenes and Gram-negative Salmonella Typhimurium via contact. These findings suggest the potential for the development of active surfaces with the implementation of nanotechnology to achieve diverse functionalities.