Improved antioxidant activity and delivery of peppermint oil Pickering emulsion stabilized by resveratrol-grafted zein covalent conjugate/quaternary ammonium chitosan nanoparticles.

Novel nanoparticles (Z-R/H) were successfully fabricated by a resveratrol-grafted zein covalent conjugate (Z-R) combined with quaternary ammonium chitosan (HTCC), which were used as stabilizers to prepare peppermint oil (PO) Pickering emulsions with antioxidant activity. HTCC effectively adjusted wettability of Z-R conjugate, and three-phase contact angle of Z-R/H3:1 was moderate (95.01°). The influencing factors of Pickering emulsion formation, including volume fraction of PO, concentration of Z-R/H, and mass ratio of Z-R to HTCC, were evaluated by droplet size, ζ-potential, microscopic observation, and stability index analysis. Pickering emulsions stabilized by Z-R/H3:1 showed excellent physical stability under heat treatment. Z-R/H nanoparticles adsorbed on the oil-water interface yielded a dense filling layer as a physical barrier to improve the emulsion stability, which was validated by confocal laser-scanning microscopy. After 4 weeks of storage, retention rate of PO in Pickering emulsion stabilized by Z-R/H3:1 remained high (72.1 %). Electronic nose analysis showed that Z-R/H3:1-stabilized emulsion effectively prevented volatilization of PO aroma components. Additionally, PO and Z-R/H nanoparticles provided an additive antioxidant effect of Pickering emulsions against DPPH and ABTS free radicals. In summary, these novel Z-R/H nanoparticle offer promising applications as a stabilizer with great potential in preparing functional Pickering emulsions to improve essential oil delivery.

Highly biologically active and pH-sensitive collagen hydrolysate-chitosan film loaded with red cabbage extracts realizing dynamic visualization and preservation of shrimp freshness.

Accurate and efficient detection of food freshness is of great significance to guarantee food safety. Herein, pH sensitive colorimetric films with considerable biological activities have been prepared by combining red cabbage anthocyanin extracts (RCE) with collagen hydrolysate-chitosan (CH-CS) matrix film. The formation mechanism of CH-CS-RCE films was discussed by SEM, FT-IR and XRD, which showed that RCE was successfully fixed in CH-CS film through hydrogen bonding and electrostatic interaction. The CH-CS-RCE films exhibited good mechanical properties, high barrier ability, excellent thermal stability, significant antioxidant and antimicrobial activity, and especially sensitive response to pH and ammonia. Fickian diffusion was the main mechanism for the release of RCE from CH-CS-RCE films and such release mechanism facilitated the maintenance of functional features of films. During the storage of shrimps at 4 °C, CH-CS-RCE2% showed a remarkable preservation effect on shrimps, and their shelf life was prolonged from 2 d to 5 d. Furthermore, CH-CS-RCE2% provided a dynamic visual color switching to detect the freshness of shrimp, realizing real-time monitoring of freshness. Color information (RGB) extracted via smartphone APP was used to enhance the accuracy and universality of freshness indication. Thus, this multifunctional film has great potential in food preservation and freshness monitoring.

Fabrication of Antioxidant Pickering Emulsion Based on Resveratrol-Grafted Zein Conjugates: Enhancing the Physical and Oxidative Stability.

Lipid oxidation is still a major problem complicating the development of food emulsions. In this study, an antioxidant Pickering emulsion stabilized by resveratrol-grafted zein (Z-R) conjugates and pectin (P) complex particles was prepared. The hydrophilic pectin successfully adjusted the wettability of Z-R; when the mass ratio of Z-R to P was 2:1 (Z-R/P2:1), the three-phase contact angle was 90.68°, and the wettability of the particles was close to neutral. Rheological analysis showed that the emulsion formed an elastic gel structure. FTIR spectra indicated that there was a hydrogen bond and electrostatic interaction between Z-R and P. The disappearance of characteristic infrared peaks of corn oil was due to a dense protective film formed on the surface of oil drops by Z-R/P2:1 particles, which was confirmed by confocal laser scanning microscopy. The emulsion stabilized by Z-R/P2:1 had excellent physical stability at a wide range of pH values (4-9), salt ion concentrations (0.04-0.15 mol·L-1) and storage times (0-30 days). The anti-lipid oxidation ability of the emulsion was outstanding; after storage for 14 days at room temperature, the MDA content in the emulsion was only 123.85 µmol/kg oil. In conclusion, the Z-R/P2:1 particles prepared in this study can effectively stabilize a Pickering emulsion and expand the usability of the method for constructing antioxidant Pickering emulsions.

A New High Selective and Sensitive Fluorescent Probe for Al3+ based on Photochromic Salicylaldehyde Hydrazyl Diarylethene.

A new diarylethene derivative 1O decorated with a salicylaldehyde hydrazine moiety was designed and synthesized successfully, and its structure was confirmed by NMR. Diarylethene 1O showed eminent photochromism and high selectivity and sensitivity for Al3+ with turn-on fluorescent performance. As the concentration of Al3+ in 1O solution increased, the color of solution remarkably changed from dark to bright green with 313-fold fluorescent emission intensity enhancement. The 1:1 combination stoichiometry between 1O and Al3+ was verified by Job's plot and MS analysis. The association constant between 1O and Al3+ was 3.9 × 102 mol-1 L, and the limit of detection toward Al3+ was 7.98 × 10-9 mol L-1. Meanwhile, the probe can be utilized in practical water and logic circuits.

Microplastic additions alter soil organic matter stability and bacterial community under varying temperature in two contrasting soils.

Microplastics can accumulate in soils and strongly affect the biogeochemical cycle. Biodegradable plastic films show potential as sustainable alternatives that could reduce microplastic soil contamination and accumulation. However, the effects of traditional and biodegradable microplastics on soil organic matter (SOM) stability are not sufficiently understood, particularly under varying temperatures. The objective of this study was to examine the effects of polyethylene (PE) and biodegradable polylactic acid (PLA) microplastics on SOM stability and bacterial community in two contrasting soils (Black soil vs. Loess soil) under varying temperature conditions (15 °C vs. 25 °C). Results showed that microplastics addition significantly enhanced cumulative CO2 emissions and DOC contents, particularly 1 % PLA treatment accelerated CO2 emissions by 19 % - 74 %, DOC content by 3 % - 23 % at 25 °C. A higher temperature sensitivity (Q10) at the PLA treatment indicated that PLA is more susceptible to elevated temperature compared to PE. The presence of both PE and PLA microplastics significantly changed the DOC spectral characteristics, i.e., high temperature increased the value of the specific UV absorbance (SUVA) in soil without microplastics, while decreased it in soil with microplastics. In comparison to soil without microplastics, soil exposed to 1 % microplastics had lower MBC concentrations and greater metabolic quotient. 16S rRNA gene sequencing showed that the presence of PLA microplastic significantly alters soil bacterial community. PE and CK had similar Bray-Curtis distances between two temperatures, while PLA increased the dissimilarity between CK compared to PE. Compared to the two soils, loess soil is more sensitive to microplastics addition. Microplastics have a non-ignorable effect on soil organic matter stability, the interaction between microplastics and soil environment should be considered.

Microplastic presence significantly alters soil nitrogen transformation and decreases nitrogen bioavailability under contrasting temperatures.

Plastic mulch is frequently used to increase crop yield, resulting in large quantities of residues accumulating in soil due to low recovery rates. However, the effects of microplastic residues from traditional and biodegradable plastic films on soil nitrogen (N) transformation and bioavailability are not well understood. Here, the main objectives were to examine the effects of micro-sized residues (diameter <5 mm) of polyethylene (PE) and biodegradable plastic mulch films (PLA) on the soil N in two contrasting soils (clay soil and sandy loam soil) in different temperatures (15 °C vs. 25 °C). Results showed that the microplastic presence showed a little effect on soil N transformation and bioavailability at 15 °C, but both microplastics significantly decreased NO3-, mineral N (MN), total dissolved N (TDN), the net cumulative N nitrification (Nn), and the net cumulative N mineralization (Nm) at 25 °C, indicating that microplastics decreased soil N bioavailability at elevated temperature. Meanwhile, the microplastics significantly reduced the temperature sensitivity (Q10) of N mineralization. The presence of microplastics changed the composition of soil mineral N with lower relative NO3- and higher NH4+ compared to the control in clay soil. The sandy loam soil was more susceptible to microplastic pollution compared to clay soil in N transformation, due to different textures and biochemistry properties in the two soils, which showed that microplastics have a significant soil heterogeneity-dependent effect on soil N processes. Therefore, the results underline that the effects of microplastic residues on soil N cycling can be partly linked to soil properties, suggesting the urgent need for further studies examining their impacts on soil nutrient cycling in different soil systems.

A highly sensitive fluorescent sensor for Cd2+ and Zn2+ based on diarylethene with a pyrene unit.

A novel multifunctional diarylethene fluorescence sensor 1O containing pyrene unit was designed and synthesized. The photochromism and fluorescence photoswitching properties of this diarylethene were studied in detail by irradiation of UV/Vis lights and response of metal ions in acetonitrile solution. Diarylethene fluorescence sensor 1O has high selectivity and sensitivity for the detections of Cd2+ and Zn2+. The limit of detections (LODs) for Cd2+ and Zn2+ were determined to be 1.85 × 10-9 mol L-1 and 7.68 × 10-9 mol L-1, respectively. The binding constants (Ka) of 1O with Cd2+ and Zn2+ in acetonitrile solution were calculated to be 5.8 × 104 mol-1 L and 6.0 × 104 mol-1 L, respectively. The compound 1O responded to the metal ions (Cd2+/Zn2+) to form complexations with 1 : 1 stoichiometry which were verified by Job's plot and MS analysis, respectively. In addition, the fluorescence sensor 1O has been successfully applied to the detection of Cd2+ and Zn2+ in real water samples and processed into test strips for on-site analysis and testing.

A turn-on fluorescence sensor for the highly selective detection of Al3+ based on diarylethene and its application on test strips.

A novel turn-on fluorescent sensor for Al3+ based on photochromic diarylethene with a 2-hydroxybenzhydrazide unit has been successfully designed and synthesized. The photochromic and fluorescent characteristics were studied methodically in methanol under irradiation using UV/vis light and induced by Al3+/EDTA. This fluorescent sensor was highly selective toward Al3+ with an obvious fluorescent color change from dark blue to blue. The Job's plot and mass spectrometry (MS) analysis indicate a binding stoichiometry of 1 : 1 between the fluorescent sensor and Al3+. Moreover, a test strip containing this fluorescent sensor was prepared to allow for the easy detection of Al3+ in water. Finally, a logic circuit was designed using four input signals (In1: UV; In2: vis; In3: Al3+; In4: EDTA) and one output signal.

Vertical Leaching of Allelochemicals Affecting Their Bioactivity and the Microbial Community of Soil.

Leaching of allelochemicals in soil is one of the fundamental processes that determines allelopathic activities but is often overlooked. In the present study, the vertical leaching of seven putative allelochemicals as well as one pesticide and one herbicide was investigated using polyvinyl chloride columns combined with a bioassay approach. The results indicated that the leachability of pretilachlor and imidacloprid were the best (Lf > 0.8), followed by vanillin and coumarin (Lf > 0.6). The leachability of daidzein, menthol, and m-tyrosine were medium (0.3 < Lf < 0.6). The lowest leachability has been observed on p-coumaric and p-hydroxybenzoic acids (Lf < 0.3). The chemicals were classified into three clusters according to the phospholipid fatty acid profile (i.e., vanillin in one cluster, coumarin and menthol in the second cluster, and the rest in the third cluster). Bioactivities of the chemicals changed dramatically. Germination of lettuce seeds was suppressed by imidacloprid and pretilachlor, and the suppression was concentration-dependent. The bioactivity of most of the allelochemicals were progressively decreased with the downward movement of chemicals. The results indicated that leaching mediated the microbial communities and the interactions of chemical-microorganism and modified the bioavailability of allelochemicals in soil.