Histamine is a class of potentially harmful biogenic amines produced during the storage and processing of meat products. Its content is a key indicator for evaluating food freshness and safety. In order to meet the needs of rapid and sensitive detection of histamine in meat products, an electrochemical biosensor based on diamine oxidase (DAO) and graphite carbon nitride/titanium dioxide (g-C₃N₄/TiO₂) heterojunction was constructed. The g-C₃N₄/TiO₂ heterojunction material was prepared by one-step calcination method, and the structure was characterized by scanning electron microscopy, transmission electron microscopy and Fourier transform infrared spectroscopy. It was confirmed that TiO₂ nanoparticles were uniformly loaded on the surface of g-C₃N₄ nanosheets, and a stable heterojunction interface was formed between them. Density functional theory calculations further confirmed that the heterojunction interface could effectively enhance histamine adsorption and promote interfacial charge transfer. Based on the theoretical calculation, the analysis of the heterojunction enhanced histamine adsorption mechanism showed that the sensor enhanced the enzyme immobilization efficiency and constructed an efficient electron transport channel, thereby realizing the effective conversion and amplification of the biological recognition signal to the electrochemical signal. The results showed that the sensor had a good linear relationship in the range of 0.05-9.00 mmol/L, the detection limit was 0.226 μmol/L(S/N = 3), and the response interference deviation was less than 8% in the anti-interference experiment. In the actual meat sample detection, the relative standard deviation was less than 5%, showing good accuracy and reproducibility. The DAO/g-C₃N₄/TiO₂ biosensor constructed in this study can be used for rapid screening and quantitative detection of histamine in meat products, aiming to provide a stable and reliable technical means for the accurate detection of histamine in food.

Based on transition metal nickel-based basic carbonate (Ni-CHs) grown in situ on carbon paper (Ni-CHs/CP), prepared by one-step hydrothermal method, a highly sensitive and selective enzyme-free sensor to detect glucose was developed. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to identify the phase and characterize the morphology of the material. Cyclic voltammetry (CV) and time-current curve were used to evaluate the performance of the sensor. The results showed that Ni-CHs/CP had the best detection ability for glucose at a low potential of 0.5 V, and the oxidation peak current of the sensor showed an excellent linear relationship with glucose concentration in the range of 0.95 μmol/L–2.623 mmol/L, with a correlation coefficient of 0.998. The detection limit was 0.31 μmol/L (R_SN = 3) and response time was 3.5 s. This sensor has good stability and has been successfully used in the detection of actual samples with spiked recoveries of 95.65%–105.56%.

The moisture distribution and key volatile flavor compounds of beef tallow from Qinchuan cattle roasted for different periods were analyzed by low field-nuclear magnetic resonance (LF-NMR) spectroscopy and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The results showed that the L* value significantly decreased (P < 0.05), the a* and b* values first increased and then decreased with roasting time. The proportion of bound water in beef tallow did not change significantly (P > 0.05), while the proportion of immobile water first increased and then decreased, and the proportion of free water showed an overall downward trend (P > 0.05). The relaxation time T₂₃ and T₂₄ showed a significant decreasing trend as roasting time increased (P < 0.05), indicating that the binding between water molecules and macromolecular substances such as protein and lipid became tighter. Beef tallow samples roasted for different periods could be effectively distinguished by electronic nose and the roasting process had a significant effect on the contents of alcohols, aromatic compounds, terpenes, and organic sulfur compounds in beef tallow according to principal component analysis (PCA) of the electronic nose data. A total of 95 volatile compounds were identified in all samples. The contents of 1-methoxy-2-propanol, 1-octene-3-ol, hexanal, nonanal, acetic acid, nonanoic acid, and acetamide were relatively higher in each sample, whereas ketones, heterocycles and amine compounds occurred mostly in the later stages of roasting. In total 19 key aroma components were identified based on odor activity value (OAV) and most of the substances have the largest OAV at 12 min of roasting.