Objective To construct a carbon nanotube-poly(neutral red) modified electrode for the competitive electrochemical rapid detection of putrescine in Procambarus clarkii samples. Methods Putrescine was selected as a freshness indicator for Procambarus clarkii. A carbon nanotube-poly(neutral red) modified electrode was designed for putrescine detection. The relationship between the electrochemical behavior of the electrode and the concentration of putrescine was explored, and its application in electrochemical sensing of putrescine was investigated. After optimizing factors such as scan rate and electrolyte pH, the putrescine content in Procambarus clarkii was determined. Recovery experiments were conducted, and the results were compared with high performance liquid chromatography. Results The carbon nanotube-poly(neutral red) modified electrode exhibited a significant electrochemical inhibition effect towards putrescine, with a notable inverse relationship between the concentration of putrescine and the peak current of the electrode. The linear range was described by the equation ΔI=3.8ln[c_(PUT)]+8.3, with a correlation coefficient of r=0.99. When applied to the detection of putrescine in crayfish samples, the results obtained by this method were highly consistent with those obtained by the high performance liquid chromatography. Conclusion The method can be employed for the detection of putrescine concentration in Procambarus clarkii and serves as a biosensor for putrescine, a freshness indicator of Procambarus clarkii.

Objective To analyze the characteristics of foodborne disease outbreaks in schools in Zibo City from 2019 to 2023. Methods The school food-borne disease outbreaks reported in Zibo City from 2019 to 2023 were collected through the national foodborne disease outbreak surveillance network for descriptive analysis. Results From 2019 to 2023 a total of 23 school foodborne disease outbreaks were reported, with a total of 337 cases, 35 hospitalized, and no death. Summer and autumn were the most common seasons. The incidents with clear pathogenic factors accounted for 34.78% (8/23), and the incidents caused by microorganisms and their toxins accounted for 75.00% (6/8). Staphylococcus aureus and its enterotoxin were the main pathogenic factors, accounting for 33.33% (2/6) of the outbreaks of microorganisms and their toxins. The most common causes of food were mixed food and other foods, accounting for 30.43% (7/23) and 26.09% (6/23), followed by food products, meat and meat products, accounting for 17.39% (4/23) and 13.04% (3/23). The main source of food was the school canteen (73.91%, 17/23). The main triggering factors were multiple factors, followed by the misuse of poisonous plants. Conclusions Microorganisms and their toxins are the main factors causing foodborne disease outbreaks in schools. Summer and autumn are the high incidence seasons. It is necessary to strengthen the food safety risk control of school canteens and strengthen the collaboration of multi-departments to reduce the occurrence of foodborne disease outbreaks in schools.

Objective To establish a fingerprint spectrum for the volatile compounds of A brand ready-to-eat bird's nest by solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS), and conduct differential analysis on different brands and types of ready-to-eat bird's nest products. Methods Using commercially available ready-to-eat bird's nest as the research object, SPME-GC-MS was used to analyze the volatile substances in 37 batches of A brand ready-to-eat bird's nest samples with different storage periods. The volatile substances were analyzed through the database of NIST 20 and the method of peak area normalization. The “TCM chromatographic fingerprint similarity evaluation system” was used to establish the volatile substances fingerprint spectrum of A brand ready-to-eat bird's nest. Results Under the service of NIST 20 database, 26 kinds of characteristic volatile components were identified in brand A's ready-to-eat bird's nest, mainly including unsaturated compounds such as 5-hydroxymethylfurfural, nonanol, lauryl alcohol, tetrahydro lavender alcohol, benzaldehyde, and so on. A fingerprint spectrum of the volatile substances in this ready-to-eat bird's nest product was established. The evaluation criteria were based on a total of 26 matching peaks, the similarity was greater than or equal to 65.8%, which could be well applied to evaluate the quality of different commercially available ready-to-eat bird's nests. Conclusion By analyzing the composition of volatile substances in ready-to-eat bird's nest and establishing a fingerprint and similarity evaluation method of volatile components for ready-to-eat bird's nest, it is possible to effectively distinguish different quality levels of ready-to-eat bird's nest, providing a scientific basis for quality control and authenticity identification of ready-to-eat bird's nest.

Objective To explore the application of the combination of real-time fluorescence quantitative polymerase chain reaction (qPCR) and droplet digital polymerase chain reaction (ddPCR) in the quantitative detection of meat adulteration. Methods This study employed qPCR and ddPCR technologies to develop a detection system with specific primers and probes for beef, lamb and pork samples, aiming to assess meat adulteration in the Beijing market. Results The experimental results revealed that the sample “Chang 5” contained adulteration of lamb and pork at a ratio of 17:10. qPCR demonstrated high sensitivity and specificity in qualitative detection, while ddPCR enabled absolute quantification of adulteration proportions. The combination of these 2 methods significantly improved detection accuracy. Conclusion The established qPCR-ddPCR combined method exhibits high sensitivity and specificity, making it suitable for rapid and precise detection of meat adulteration. This approach provides reliable technical support for food safety regulation.

Objective To develop a rapid and sensitive detection technology for pathogenic microorganisms in food packaging based on the clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated protein 13a (Cas13a) system. Methods The method leveraged the specific recognition and signal amplification characteristics of the CRISPR-Cas13a technology. Multiple guide RNAs were designed to target different sites on pathogenic RNA, enabling a single RNA molecule to activate multiple Cas13a enzymes simultaneously. This cascade triggered trans-cleavage of RNA reporter molecules in the reaction mixture, generating a detectable fluorescent signal. The tandem design synergistically enhanced signal amplification efficiency, thereby improving detection sensitivity. Results The limits of detection of this method for pathogenic and RNA were 800 copies/mL and 18.7 pmol/L, respectively, and the detection could be completed in a short time, accurately distinguishing different pathogens. Testing food packaging samples contaminated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pseudvirus showed recovery rates ranging from 89.71% to 102.56%. Conclusion This study presents a rapid, cost-effective and easy-to-operate method for detecting pathogenic microbial contamination on food packaging surfaces, indicating high accuracy, offering potential application value for monitoring microbial risks in foodborne transmission pathways.

Objective To investigate the protective effects of ethanol extract of Chuangxiong tea on the 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AAPH) (1 mmol/L) on oxidative stress injury of proximal renal tubule epithelial cells of pigs. Methods LLC-PK1 cells were co-cultured with ethanol extract of Chuanxiong tea (labeled CXTEE) with different mass concentrations ranging from 10 to 100 μg/mL for 24 h, and then placed in Dulbecco's modified eagle medium (DMEM) containing AAPH for 4 h to establish the cell damage model. The cell survival rate was measured by tetramethyl azazole blue (MTT) method. The content of malondialdehyde (MDA) and the level of total reactive oxygen species (ROS) were determined by thiobarbituric acid colorimetry and 2',7'-dihydrodichlorofluorescein yellow diacetate (DCFH-DA) probe technique, respectively. In addition, the activity of several antioxidant enzymes, including catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), glutathione S-transferase (GST), γ-glutamylcysteine synthetase (γ-GCs), and the concentration of glutathione (GSH), were also evaluated using specific kits. Results The results showed that the cells pretreated with CXTEE showed a higher survival rate, and the total ROS level and MDA production in the cells were significantly reduced. At the same time, the extract also enhanced the activity of antioxidant enzymes (such as CAT, SOD, GSH-Px and GST) in the damaged cells, promoted the activity of γ-GCS and increased the content of GSH. Further experiments showed that CXTEE could also up-regulate the mRNA expression levels of SOD, GSH-Px and CAT in oxidative damage LLC-PK1 cells. Conclusion The ethanol extract of Chuangxiong tea may reduce the levels of MDA and ROS by strengthening the antioxidant defense system of cells, thus alleviating the oxidative stress damage caused by AAPH to LLC-PK1 cells. This study can provide a basis for further application and development of Chuangxiong tea.

Objective To establish a rapid colorimetric method for the detection of histamine in fish samples based on the oxidase activity of Ag₃PO₄ nanozyme. Methods Ag₃PO₄ nanoparticles were prepared by the hydrothermal method. Utilizing their oxidase catalytic activity, with CH₃COONa as the buffer system and 3,3',5,5'-tetramethylbenzidine as the oxidation substrate, a rapid colorimetric detection method for histamine in fish was established. Results The detection time of this method was about 100 seconds. The limit of detection was 0.58 mg/L, indicating high detection sensitivity. In the detection of multiple competitive targets, this method showed good specificity for histamine molecules. In the spiked experiments on actual samples, the spiked recovery rate of this method ranged from 104.24% to 108.30%, and the relative standard deviations were from 1.81% to 3.44%, which had good detection accuracy. Conclusion This method demonstrates the advantages of being intuitive, rapid, highly sensitive and having good specificity. It can adapt to the complex daily detection environment and provides a new idea for the detection of histamine in fish meat.

Objective To investigate the effects of Tuo tea flavonoids on D-galactose-induced aging mice in delaying aging and inhibiting inflammation. Methods The anti-aging efficacy of Tuo tea flavonoids were evaluated by measuring weight change, organ index and specific indicators in serum and tissue samples of aged mice treated with Tuo tea flavonoids. Results Tuo tea flavonoids could effectively prevent weight loss caused by aging, and also had a significant effect on preventing the shrinkage of key organs such as the thymus and brain. In addition, the compound also increased the levels of total antioxidant capacity (T-AOC), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in the blood and liver of aging mice, while reducing the concentrations of malondialdehyde (MDA) and nitric oxide (NO). At the same time, the levels of inflammation-related interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) cytokines in serum of aging mice were decreased. Further studies showed that in liver tissues, the expression levels of neuronal nitric oxide synthase (nNOS), endothelial nitric oxide synthase (eNOS), manganese superoxide dismutase (Mn-SOD), copper zinc superoxide dismutase (Cu/Zn-SOD) and catalase (CAT) mRNA increased. The inducible nitric oxide synthase (iNOS) showed a decreasing trend. Especially when the dose reached 100 mg/kg, the Tuo tea flavonoids showed better effects than the same dose of vitamin C. Conclusion As a natural product with potential life-prolonging function, the Tuo tea flavonoids show good biological activity.

Objective To investigate the content of 16 kinds of rare earth elements in commercial vegetables and evaluate the health risks caused by the intake of rare earth elements in vegetables for users in Gansu Province. Methods Samples from 6 categories were collected from 13 areas in Gansu Province, and the content of the 16 kinds of rare earth elements were measured by inductively coupled plasma mass spectrometry. According to the health risk analysis method recommended by United States Environmental Protection Agency (USEPA), the allowable daily intake (ADI) was used to assess the health risk of rare earth elements in commercial vegetables. Results The earth elements of vegetables sold in Gansu were mainly Sc, Y, Ce, La, Nd, Pr, with detection rate exceeds 50%, the total content of rare earth elements in the 6 types of vegetables was 0.1764 mg/kg, ranked from high to low as follows: Melon and fruit vegetables>leafy vegetables>stem vegetables>solanaceous fruit vegetables>root vegetables>bean vegetables. There were no significant differences in the content of rare earth elements among different vegetable categories (P>0.05), but significant differences were observed among vegetables from different areas (P<0.05). The health risks posed by the 16 kinds of rare earth elements varied among different population groups, with adult males and females exhibiting higher risks than children. The daily intake of rare earth elements through vegetable consumption was 0.0025 mg/(kg d), which was below the reference value of 0.07 mg/(kg d). Conclusion The content of rare earth elements in commercial vegetables in Gansu Province is low. The intake of rare earth elements through vegetables by residents will not pose a risk to human health.

Objective To explore the effects of ultrasonic synergistic enzymatic hydrolysis on the antioxidant activity and structure of donkey milk casein, optimize the process parameters of composite treatment, and analyze the promotion mechanism of ultrasonic pretreatment on the enzymatic hydrolysis process. Methods Using donkey milk casein as raw material, the ultrasonic parameters (200 W, 20 min, 6 s/6 s intermittency ratio) were optimized by single factor experiment, the neutral protease and trypsin (the mass ratio was 2:1) were screened, and the enzymatic hydrolysis conditions were optimized by response surface method (enzyme addition amount 4.86%, 55.28 °C, pH 7.76). The changes of protein molecular weight, secondary structure and functional groups were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and infrared spectroscopy. The antioxidant indexes such as 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging rate were determined. Results Ultrasonic synergistic enzymatic hydrolysis resulted in antioxidant ability of 69.77% and a 65.3% increase in Fe³⁺ reducing capacity, which was significantly better than that of the single treatment. The structure showed that the α-helix decreased to 26.70%, the random coil increased to 28.35%, the aromatic amino acids were exposed, the sulfhydryl groups were oxidized to disulfide bonds, and the molecular weight was reduced. The predicted value of the response surface model was in good agreement with the measured value (R²=0.9937). Conclusion The results of ultrasonic pretreatment significantly improves the antioxidant activity by destroying the structure of protein micelles and releasing antioxidant short peptides in synergy with enzymes, which provides a reference process parameter for the production of high value-added donkey milk antioxidant products, which is helpful to promote the development of donkey milk industry and improve the economic value of donkey milk.