Tea is deeply loved by consumers for its unique aroma and health benefits, which is why tea quality and safety have garnered widespread attention. The quality and safety of tea involves the quality and safety of tea, as well as issues such as pesticide residues, heavy metals, harmful microorganisms, and fluorine. It is closely related to all aspects of tea cultivation, processing and storage. This paper started with tea-related standards and focuses on tea quality and safety issues such as pesticide residues, heavy metals, harmful microorganisms and fluoride, etc. It summarized the pretreatment of tea samples, normal detection technologies, rapid detecting methods, and relevant research progress. The aim is to provide a comprehensive knowledge framework for the tea industry, enhance quality and safety standards, and promote the sustainable development of the tea industry.

Objective To establish a method for the rapid determination of total flavonoids in tartary buckwheat by cerium dioxide/multi-walled carbon nanotubes/acetylene black (CeO₂/MWCNTs/AB) nano-electrochemical sensor. Methods The modified material and these nanoelectrochemical sensors were characterized by scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The electrochemical behavior of rutin on the electrode surface was systematically investigated via CV. Critical parameters were optimized, including electrolyte type, pH, modifier ratio, coating volume, accumulation time and scan rate. Results One pair of well- defined redox peaks were observed at the potential of 0.54 V and 0.57 V, which indicated that the electrochemical oxidation and reduction reaction of flavonoid was reversible. The experimental conditions were optimized, the results as follows: B-R solution with pH 2.0 as the electrolyte solution, V_CeO2/MWCNTs:V_{acetylene black} as 1:3, amounts of modified material, 12 μL, enrichment time as 9 min. At these conditions, the oxidation peak current of flavonoid linearly increased with its concentration, I_p=0.793C+3.508 (r²=0.998), and the limit of detection was 6.5×10^-8 mol/L. The developed method was used to determinate total flavonoids content of tartary buckwheat, the recoveries were in the range of 99.46%-102.15%, the results were superior to ultraviolet-visible spectrophotometry. Conclusion The method is feasible for the rapid and accurate determination of total flavonoids in food with the advantages such as simple pretreatment time saving and convenience, low detection cost, high sensitivity and good accuracy.

Objective To establish a rapid detection model for the nutritional components of Oncorhynchus mykiss based on near-infrared spectroscopy (NIR). Methods Firstly, near-infrared spectral data of 200 Oncorhynchus mykiss were collected. Then, the content of 3 kinds of nutritional components (moisture, fat and protein) of each Oncorhynchus mykiss were determined by national standard methods. The near-infrared spectral data and nutritional component data were matched one by one. The near-infrared rapid detection model was established by combining NIR with partial least squares (PLS), and the best detection model was screened out. Results The pretreatment method of the moisture content detection model was multiple scattering correction (MSC), and the optimal model was obtained when the wavelength range was 4000-10000 cm^-1. The pretreatment method of the fat content detection model was standard normal variable (SNV), and the optimal model was obtained when the wavelength range was 5000-7144 cm^-1 and 7404-10000 cm^-1. The pretreatment method of the protein detection model was second derivative (ds2)+SNV+Savitzky-Golay smoothing (sg9), and the optimal model was obtained when the wavelength range was 4100-5100 cm^-1 and 5400-9000 cm^-1. The Q value, the correlation coefficient of the correlation coefficients, and the correlation coefficient of prediction of the optimal model were all relatively large, and the standard deviation of square error corrected and standard error of cross validation were close to each other, which met the best modeling principle. Conclusion The best model is verified by the prediction set that do not participate in the modeling. The absolute deviation between the predicted value and the true value (determined by the national standard method) is no more than 5.7%. This indicates that the model can be used for the detection of three nutritional components of Oncorhynchus mykiss, and can achieve non-destructive and rapid detection of the nutritional components of Oncorhynchus mykiss, saving detection costs and shortening the detection cycle.

Objective To evaluate the pollution levels of five harmful heavy metals in different tissue parts and whole crabs of imported Cancer pagurus (common yellow crabs), clarify their distribution characteristics and food safety risks. Methods According to the national standard GB 5009.268—2016 National food safety standard-Determination of multielements in food, inductively coupled plasma mass spectrometry (ICP-MS) was used to detect the content of arsenic, cadmium, chromium, mercury, and lead in 9 parts of Cancer pagurus liver, pancreas, crab roe, crab gills, crab body meat, crab leg meat and whole crab. The differences in heavy metal enrichment and exceedance in different parts were analyzed. Results Cadmium pollution was the most prominent, with the highest content in the liver and pancreas (up to 98.60 mg/kg) and a exceedance rate of 95.0%; arsenic was commonly detected but there was no clear limit standard, while mercury and lead only exceed the limit in inedible parts such as crab gills; the overall heavy metal content was cadmium>arsenic>mercury>lead>chromium, and the content of edible parts (crab body meat, crab leg meat) was significantly lower than that of non edible parts; the heavy metal content in whole crabs was significantly affected by highly polluted areas such as the liver and pancreas. Conclusion Imported Cancer pagurus pose a high risk of cadmium enrichment in suspected edible parts such as the liver, pancreas and gonads. It is necessary to improve the definition criteria for edible parts and establish a targeted risk assessment mechanism. It is recommended that consumers reduce their intake of highly contaminated parts. This study provides data support for optimizing the safety supervision strategy and dietary guidance of imported crustacean aquatic products.

Objective To investigate the current status of veterinary drug residues in eggs on sold in Banan District, Chongqing and assess the health risk of residues’ dietary intake residues. Methods In 2024, a total of 208 egg samples were randomly collected from markets and supermarkets in 10 towns and streets of Banan district. The residues of 15 kinds of veterinary drugs were detected using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The point assessment method was employed to calculate the daily estimated exposure and hazard quotient for dietary exposure risk assessment. Results The detection rate of veterinary drug residues in 208 samples of market eggs was 8.65% (18/208), with doxycycline showed the highest detection rate at 3.37% (7/208). The unqualified rate was 0.96% (2/208), with the unqualified samples mainly coming from unbranded bulk eggs sold in markets. The dietary exposure assessment revealed that the daily estimated exposure of veterinary drug residues ranged from 0.00013 to 0.03450 μg/(kg·bw·d), and the hazard quotient ranged from 0.00000 to 0.00872, significantly below the safety threshold. This indicates a low health risk associated with the intake of veterinary drug residues in eggs sold in the market. Conclusion Veterinary drug residues are detected in eggs sold in Banan District, Chongqing, but the residue is generally controllable and the health risk low. Special attention should be given to bulk and unbranded eggs, and standards for veterinary drug use and residue limits should be further refined.

Objective To evaluate the levels of metal elements contamination in Morella ruba Lour. from different production areas in Wenzhou and establish a comprehensive evaluation system. Methods The 121 Morella ruba Lour. samples and 68 soil samples from Morella ruba Lour. planting sites in Wenzhou were studied. The pH of the soil and 6 kinds of metal elements indicators, including chromium, nickel, arsenic, cadmium, mercury and lead, in both the soil and fruits were measured and analyzed. A fruit-soil correlation model (incorporating correlation analysis and principal component analysis of 13 parameters across 54 samples) was established. Results The qualification rate of Morella ruba Lour. samples was 94.21%, while the qualification rate of soil samples was only 39.71%; there was a varying degree of correlation between the metal elements content in Morella ruba Lour. fruits and soil, with a strong positive correlation between mercury in Morella ruba Lour. fruits and chromium and nickel in soil; principal component analysis identified chromium and cadmium in soil, as well as nickel, lead and arsenic in Morella ruba Lour., as the core indicators for evaluating the metal elements quality and safety of Morella ruba Lour.. Conclusion This study established a comprehensive evaluation system for metal elements quality safety in Morella ruba Lour., providing methodological references for regional agricultural product safety regulation.

Objective To investigate the contamination of fungal toxins in locally produced rice in Harbin Area, and conduct a risk assessment. Methods The content of aflatoxin B₁ (AFB₁) and ochratoxin A (OTA) in commercially available locally produced Daohuaxiang No.2 rice were detected using liquid chromatography-tandem mass spectrometry. Through Monte Carlo simulation, non-parametric probabilistic assessment methods and point assessment methods were employed to evaluate the dietary exposure risk of different populations in Harbin to AFB₁ and OTA through the consumption of rice. Results A dietary exposure model for AFB₁ and OTA has been established. This study found that both AFB₁ and OTA pose a high risk to children, especially those with high consumption levels, who had a greater potential risk of developing liver cancer through rice consumption. Conclusion The overall health risk of AFB₁ and OTA exposure through rice consumption among residents in Harbin is relatively low. However, there is a significant potential health risk for high-consuming children, which requires much more attention. Apparent health risks were not found for other populations.

Objective To understand the levels of veterinary drug residues in chickens and eggs in the diet of Xinjiang residents, and analyze and assess the health risks associated with exposure to veterinary drug residues in this region. Methods Veterinary drug residues were detected in chicken and egg samples from supermarkets and farmers’ markets in Xinjiang Uygur Autonomous Region from 2021 to 2023 by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and then combined with the data on the food intake of the residents of Xinjiang Uygur Autonomous Region, and then assessed the risk of dietary exposure by point assessment method. Results The detection rate of 19 kinds of veterinary drug residues in chicken and egg samples in Xinjiang from 2021 to 2023 was 23.3% (63/270), and the exceedance rate was 6.3% (17/270), and the difference in the detection rate of florfenicol was statistically significant by chi-square test (P=0.002), and the differences in detection and exceedance rates in the Northern, Southern and Eastern regions of Xinjiang were not statistically significant. The food safety index for chicken meat in Xinjiang were much smaller than 1, and the food safety index for veterinary drug residues in eggs were all less than 1, but the food safety index for ofloxacin, enrofloxacin, ciprofloxacin, diclazuril and florfenicolide were much greater than 1. Conclusion The risk of dietary exposure to veterinary drug residues for chicken meats and eggs in Xinjiang is small and in the controllable range.

Objective To analyze the key factors affecting constant weight in the direct drying method and to optimize the experimental conditions for vacuum drying, distillation, and Karl Fischer methods as specified in the GB 5009.3—2016 National food safety standard-Determination of moisture in foods. Methods The determination of moisture content in samples was conducted according to GB 5009.3—2016. The study altered experimental conditions to explore key factors affecting constant weight in the direct drying method, optimized conditions for vacuum drying by adjusting vacuum pressure, and compared the effects of different reagents (xylene, Karl Fischer reagent) on detection results. Results In the direct drying method, sample temperature, cooling time in the desiccator and the degree of sample pulverization were identified as key factors affecting constant weight. For vacuum drying method, increasing the vacuum to -0.1 MPa and adding an effective desiccant to the drying box could rapidly evaporate moisture from the sample, improving detection efficiency. In the distillation method, the preparation and purification of analytical-grade toluene or xylene could be omitted. The Karl Fischer method could use a low-toxicity, pyridine-free Karl Fischer reagent. Conclusion The 4 detection methods in this standard are optimized separately to solve problems such as difficulty in achieving constant weight after repeated drying and the use of toxic and harmful reagents. The rationalization suggestions provide in this study have increased the operability of the standard and improved the testing efficiency of the laboratory.

Objective To establish a pre-amplified quantitative real-time polymerase chain reaction (qPCR) method for the detection of Oncorhynchus mykiss source components. Methods The study developed an enhanced pre-amplified qPCR method, which was based on the validation and improvement of the existing standard qPCR method and compared the performance of both methods. Results Specificity testing of the standard qPCR method revealed cross-reactivity with closely related species, such as Coho salmon and Atlantic salmon. The established improved pre-amplified qPCR method, which incorporated a pre-amplification step, exhibited high specificity and no cross amplification was observed for Coho salmon, Atlantic salmon and other closely related species. The amplification efficiencies of the standard qPCR and the pre-amplified qPCR methods were 90.25% and 104.91%, respectively. The lowest limits of detection of the 2 kinds of methods were 2.99×10^-3 ng/μL (0.83-8.87 pg/μL, 95% confidence interval) for the standard qPCR and 1.50×10^-4 ng/μL (0.09-0.27 pg/μL, 95% confidence interval) for the pre-amplified qPCR. Conclusion The method established in this study has the characteristics of strong specificity, high sensitivity, and is suitable for authenticity and adulteration detection of Oncorhynchus mykiss source components in food products.