Worldwide, millions of tons of crustaceans are produced every year and consumed as protein-rich seafood. However, the shells of the crustaceans and other non-edible parts constituting about half of the body mass are usually discarded as waste. These discarded crustacean shells are a prominent source of polysaccharide (chitin) and protein. Chitosan is a de-acetylated form of chitin obtained from the crustacean waste that has attracted attention for applications in food, biomedical, and paint industries due to its characteristic properties, like solubility in weak acids, film-forming ability, pH-sensitivity, biodegradability, and biocompatibility. We present an overview of the application of chitosan in composite coatings for applications in food, paint, and water treatment. In the context of food industries, the main focus is on fabrication and application of chitosan-based composite films and coatings for prolonging the post-harvest life of fruits and vegetables, whereas anti-corrosion and self-healing properties are the main properties considered for antifouling applications in paints in this review.

Although polyvinyl alcohol (PVA) is a promising biodegradable packaging material, it presents some disadvantages for food packaging such as poor ultraviolet (UV) and water vapor barrier properties, low mechanical strength, poor water resistance, and lack of antimicrobial properties. To overcome these limitations, novel PVA/cellulose nanocrystals (CNC)/titanium dioxide (TiO₂) nanocomposites were developed, characterized, and demonstrated for potential food packaging applications. The mechanical strength, water vapor barrier, and UV barrier properties of PVA/CNC/TiO₂ 5 % film (5 wt% TiO₂ in the PVA/CNC matrix with 5 wt% of CNCs) increased by 55.8 %, 45.2 %, and 70,056.8 %, respectively, compared to those of a PVA film. In the antibacterial simulation test, PVA/CNC/TiO₂ 5 % film could limit the growth of microorganisms for 14 days. In packaging tests with fresh garlic, PVA/CNC/TiO₂ films effectively prevented weight loss and spoilage by external influences, indicating the potential of the PVA/CNC/TiO₂ nanocomposites for food-packaging applications.

Colorimetric sensors based on polydiacetylene (PDA) materials have been developed for detecting acid-base. Since PDAs often change color upon exposure to organic solvents, most of previous studies used water as a medium. This presents a problem for detecting organic acids and bases with limited solubility in water. In this contribution, we explore the applications of PDA/Zn²⁺/ZnO nanocomposites as colorimetric sensors for detecting organic acid-base in various organic solvents and food products. Owning to its high color stability, this class of PDA materials can be dispersed in tetrahydrofuran, dimethyl sulfoxide, and ethanol while the blue phase remains. We have found that the sensitivity of PDA/Zn²⁺/ZnO nanocomposites to acid-base varies with the solvent properties. The sensors prepared by dispersing in different solvents can detect acid-base at different concentrations. Raman spectroscopy carried out directly in the liquid suspensions reveals the mechanisms of color transition in each system. Fine-tuning of the sensitivity can also be achieved by varying the ZnO ratios within nanocomposites. The ability to control the sensitivity allows the utilization of PDA/Zn²⁺/ZnO nanocomposites for semi-quantitative analysis of acid-base in food products. Solid-state sensors fabricated by embedding in nylon filters can determine the concentration of sorbic acid in fruit juices. The freshness of milk can be indicated via naked-eye detection as well. Our study expands the applications of PDA materials as colorimetric sensors for food industries.

A magnetic covalent organic framework nanocomposite (Fe₃O₄@COF(Tp-NDA)) was synthesized via a solvothermal method, used as a magnetic adsorbent for the extraction of polycyclic aromatic hydrocarbons (PAHs) from lake water, tea, coffee, and fried chicken, and detected using a high performance liquid chromatography-ultraviolet detector. The synthesized magnetic adsorbent was characterized via transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, N₂ adsorption–desorption isotherm analysis and vibrating sample magnetometry. Parameters that affected the extraction conditions and desorption conditions were optimized. Adsorption equilibrium could be attained within 3 min. The prepared magnetic material could be reused 10 times. The limits of detection and quantification were 0.05–0.25 μg L⁻¹ and 0.17–0.83 μg L⁻¹, respectively. The recovery was 74.6–101.8% with a relative standard deviation of below 4.2%. The method was successfully used to detect PAHs in various samples.

In the present work, dispersive micro-solid phase extraction (D-μ-SPE) method using magnetic graphene oxide tert-butylamine (GO/Fe₃O₄/TBA) nanocomposite, as an efficient sorbent, was applied for determining 2,4-dichlorophenoxyacetic acid (2,4-D) in water and food samples. Detection was carried out using high-performance liquid chromatography (HPLC) instrument. Influential parameters of D-μ-SPE such as sorbent and its amount, elution solvent and its volume, adsorption and desorption times and pH of sample solution were investigated and optimized. Under the optimized conditions, limit of detection and quantitation values were 0.007 and 0.02 μg/mL, respectively. Recovery data for several real samples were obtained within the range of 88.0–94.0% with a relative standard deviation (RSD) less than 7.5%. The proposed method was successfully applied to quantitative determination of 2,4-D in several vegetables and water samples.

Melanin nanoparticles (MNP) were isolated from squid ink and used for the preparation of gelatin-based nanocomposite films containing various concentration of MNP (0, 0.25, 0.5, and 1.0 wt%). The MNP was a spherical form with an average diameter of about 100 nm. The MNP was compatible with the gelatin matrix to form uniform nanocomposite films. The surface color of gelatin/MNP nanocomposite films was brown with decreased transparency, but other film properties such as mechanical, water vapor barrier, and thermal stability properties increased significantly compared with the neat gelatin film. All the film properties of the gelatin/MNP nanocomposite films were dependent on the MNP concentration. Also, the gelatin/MNP nanocomposite films exhibited a high antioxidant activity which has great potential for food packaging and biomedical applications.

The presented study investigates the application of MnO₂/3MgO nanocomposite, as a new sorbent for solid phase extraction and determination of trace amounts of Pb²⁺ and Cu²⁺ from various samples using flame atomic absorption spectrometry. After extraction, the analytes were desorbed using 0.01 M ethylenediaminetetraacetic acid. The effects of various parameters were studied and optimized. Under optimized experimental conditions the linear dynamic ranges for Cu²⁺ and Pb²⁺ were 10‒900 and 30‒900 μg/L, respectively, with a preconcentration factor of 20. The detection limits of Cu²⁺ and Pb²⁺ were 4 and 11 μg/L, respectively, and relative standard deviations for eight determinations of 100 μg/L were 3.6 and 3.8% for Cu²⁺ and Pb²⁺, respectively. The method was successfully applied for determination of copper and lead in mushrooms, rice, tap water and refinery wastewater with good spike recoveries ranging between 95‒106%.

A molybdenum disulfide(MoS2)-based core-shell magnetic nanocomposite (Fe₃O₄@MoS₂) was synthesized by the stepwise hydrothermal method. Two-dimension ultrathin MoS₂ sheets with a thickness of approximately 20 nm were grown in situ on the surface of Fe₃O₄ (∼200 nm). They were employed as an adsorbent for the magnetic solid-phase extraction (MSPE) of sulfonamide antibiotics (SAs) from water samples. High-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) was used for SA quantitation. Extraction parameters, including the pH effect, amount of Fe₃O₄@MoS₂, extraction time, temperature, and desorption conditions, were systematically investigated. The electrostatic interaction between the positively charged SAs and negatively charged MoS₂ nanoparticles in the optimal extraction conditions enhanced the adsorption of SAs on the sorbent surface. Under chosen conditions, the proposed strategy achieved wide linear range of 1.0–1000 ng·L⁻¹ SAs, low limits of detection (LOD, 0.20–1.15 ng·L⁻¹, S/N = 3:1), good trueness (recoveries between 85.50–111.5%), satisfactory repeatability and reproducibility (relative standard deviation, <10%, n = 5), and excellent recoveries between 80.20% and 108.6% for SAs determination in spiked waste water samples. The proposed strategy was validated and successfully applied for the analysis of water, milk, pork meat and fish meat. The nanocomposites, which have the combined advantages of magnetic separation and high adsorption affinity toward SAs, are a promising sorbent for antibiotics extraction from real samples.

In Figure 4: should read “Nitric acid (0.1 M)” instead of “Nutric acid (0.1 M)”Figure 6 should be:

Titanium dioxide nanoparticles seem to have a low toxicity to terrestrial organisms, though few studies are published in this area. TiO₂ used in sunscreens are nanocomposites where TiO₂ has been coated with magnesium, silica or alumina, as well as amphiphilic organics like polydimethyl siloxane (PDMS), and these coatings are modified by ageing. We assessed the ecotoxicity and propensity for bioaccumulation of an aged TiO₂ nanocomposite used in sunscreen cosmetics, and its potential effect on the frequency of apoptosis in different earthworm tissues. The earthworm Lumbricus terrestris was exposed to the TiO₂ nanocomposite for 7days in water or 2–8weeks in soil with the nanocomposite mixed either into food or soil at concentrations ranging from 0 to 100mgkg⁻¹. Apoptosis was then measured by immunohistochemistry and Ti localized by XRF microscopy. Results showed no mortality, but an enhanced apoptotic frequency which was higher in the cuticule, intestinal epithelium and chloragogenous tissue than in the longitudinal and circular musculature. TiO₂ nanoparticles did not seem to cross the intestinal epithelium/chloragogenous matrix barrier to enter the coelomic liquid, or the cuticule barrier to reach the muscular layers. No bioaccumulation of TiO₂ nanocomposites could thus be observed.