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BACKGROUND: Nε‐carboxymethyllysine (CML), Nε‐carboxyethyllysine (CEL) and α‐aminoadipic acid (AAA) are important foodborne hazards and their intake can cause a variety of diseases in humans. It is extremely important to investigate the formation mechanism of CML, CEL and AAA, as well as their association with each other when aiming to control their production. RESULTS: A multi‐response kinetic model was developed within the glucose‐lysine Maillard reaction model system. The concentrations of glucose, lysine, glyoxal (GO), methylglyoxal (MGO), CML, CEL and AAA were quantified at different temperature (100–160 °C) and at different intervals (0–60 min). The experimental data were fitted to the proposed model to calculate kinetic parameters for the corresponding steps. The results indicated that the production of CML was primarily relied on the direct oxidative cleavage of the Amadori product, rather than the reaction between GO and Lys, whereas CEL and AAA were generated through the reaction of MGO with Lys. Significantly, the reaction between α‐dicarbonyl compounds and Lys preferentially generated CML and CEL, resulting in the lower concentrations of AAA compared to CML and CEL. CONCLUSION: The multi‐response kinetic model developed in the present study can be applied well to the Maillard reaction. The relationship between the formation mechanisms of CML, CEL and AAA is also explained. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

BACKGROUND: Flexible surface‐enhanced Raman spectroscopy (SERS) substrates such as paper‐based substrates show great potential for rapid detection of residual chemicals on food surfaces. However, controlling the density and distribution of metallic nanoparticles adsorbed on the paper is still challenging. RESULTS: The amount of gold (Au) nanospheres (51 ± 4 nm) attached on the filter paper modified with 3‐aminopropyltriethoxysilane (APTES) was tunable, increasing as the level of APTES (2.5–15.0 g kg−1) applied for paper modification increased. Moreover, the Au nanospheres were relative evenly distributed on the filter paper modified with 2.5–10.0 g kg−1of APTES, which resulted in excellent intra‐ and inter‐reproducibility of SERS signals for pesticides including thiram, diquat dibromide, and paraquat dichloride (relative standard deviation = 2.2–10.1%). The modified paper‐based substrate could be used to detect as low as 0.05–0.2 mg L−1 of pesticides in standard solutions, and as low as 5–20 ng cm−2 of residual pesticides on apple skins with minimum sample pretreatment. CONCLUSION: This paper‐based substrate with tunable feature for the density and distribution of nanoparticles is applicable for rapid SERS detection of residual pesticides in fruits and vegetables. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

BACKGROUND: Surface‐enhanced Raman scattering (SERS) substrates based on metallic nanoparticles locked in some flexible materials have great potential for rapid detection of pesticide residues in foods, but these substrates are generally not reusable. RESULTS: A bendable and reusable sponge based on polydimethylsiloxane (PDMS) and Au nanospheres was synthesized and employed as SERS substrate to analyze thiram on the surfaces of apples and grapes (20–1000 ng cm−2) and in their juices (0.5–5.0 mg L−1) with minimum sample pretreatments. The lowest detectible concentrations for thiram in fruit juices and on fruit skins were 0.5 mg L−1 and 20 ng cm−2, respectively. The Au‐PDMS substrate had acceptable intra‐reproducibility for SERS analysis of thiram in fruit juices and on fruit skins, resulting in 3.6–16.9% relative standard deviation (RSD) for the SERS signal of the primary peak of thiram. Moreover, the Au‐PDMS substrate exhibited distinguished reusability and stability, which could provide a reproducible SERS signal of thiram in apple juice even after the substrate being reused ten times (RSDs for the three major characteristic peaks of thiram were 2.7–10.5% during the ten reused cycles). CONCLUSION: This flexible and reusable Au‐PDMS SERS substrate for thiram detection could be readily extended to the analysis of other trace chemicals in a broad range of foods, providing a new possibility for SERS application. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: Paraquat, a highly efficient herbicide, is widely used in agricultural practices throughout the world. However, paraquat residues in food pose a threat to human health. In order to develop a rapid and sensitive method, surface‐enhanced Raman spectroscopy (SERS) coupled with gold nanoparticles was applied to analysis of paraquat in apple juice. RESULTS: Natural organic compounds (sugars and organic acids) in apple juice interfered with SERS measurement. Sample preparation was needed. Paraquat could be detected at concentrations as low as 0.02 and 0.1 µg mL− 1 with the weak cation‐exchange solid‐phase extraction (WCX‐SPE) method and dilution method for sample preparation, respectively. For quantitative analysis, the R2 cv of the partial least‐squares regression model with the dilution method (0.939) was not as good as with the WCX‐SPE method (0.984), but the dilution method is much less costly, simpler and time saving. Satisfactory recovery values were obtained ranging from 94.73% to 114.81%, with the exception of 56.55% for the lowest concentration. CONCLUSION: This work showed that SERS combined with gold nanoparticles could determine paraquat in apple juice. As a simple, rapid and ultrasensitive method, it has great practical potential for detection of other contaminants in a variety of foods. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]