Recently, food-grade Pickering particles, particularly plant proteins, have attracted tremendous attention because they are biobased, environmentally-friendly and edible. To explore the potential of tea water-insoluble protein (TWIP) nanoparticles from tea residues for stabilizing Pickering emulsions, the average hydrodynamic diameter (DH), zeta potential and morphologic profiles of TWIP nanoparticles were characterized using dynamic light scattering (DLS), laser Doppler velocimetry (LDV) and atomic force microscopy (AFM), respectively. The results indicated that TWIP nanoparticles were irregular colloidal particles with a DH greater than 300 nm and a negative charge of more than −30 mV at ionic strengths of 0–400 mM and a fixed TWIP nanoparticle concentration (2.0%). Furthermore, the effect of the TWIP nanoparticle concentration (0.5–4.0%, w/v) and oil-water ratio (2:8–6:4) on the characteristics of the Pickering emulsions stabilized via TWIP nanoparticles was investigated. Increasing the TWIP nanoparticle concentration generated a firm and thick TWIP nanoparticle-based interfacial layer, as verified by Cryo-scanning electron microscopy imaging, and decreased the droplet size of Pickering emulsions at an oil-water ratio of 4:6. Additionally, an increase of the oil-water ratio to 6:4 favored the formation of emulsions with extraordinary creaming stability at the fixed TWIP nanoparticle concentration of 2.0%. The present study is the first to suggest TWIP nanoparticles as a type of food-grade Pickering particle.

A facile and novel nanosensor analytical strategy was developed for the colorimetric detection of pencycuron fungicide in rice, potato, cabbage, and water samples based on the pencycuron-induced aggregation of 6-aza-2-thiothymine-functionalized gold nanoparticles (ATT-AuNPs). The ATT-AuNPs exhibited good stability and were characterized with UV-visible spectroscopy, Fourier transform infrared (FT-IR) spectrometry, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), and zeta potential techniques. The addition of pencycuron facilitated strong non-covalent interactions (electrostatic, van der Waals, and H bonding) between pencycuron and ATT-AuNPs, inducing a significant red shift in the surface plasmon resonance (SPR) peak of ATT-AuNPs along with a color change from red to blue. A linear equation was established between absorption ratio (A720/A528) and pencycuron concentration (2.5–100 μM) with a correlation coefficient (R2) of 0.9915. The detection limit was calculated to be 0.42 μM, which was much lower than that of other analytical methods. The designed ATT-AuNP serves as a promising nanosensor for the rapid, simple, and selective label-free colorimetric detection of pencycuron in rice, potato, cabbage, and water samples, is highly sensitive, and does not require sophisticated instruments, tedious sample preparations, and time-consuming separation and pre-concentration procedures.