Carbamate pesticides are synthesized by substituting amino group onto the carbonyl group of carbamic acid derivatives, and are widely used in agriculture because of their short environmental persistence and low residue accumulation. However, due to unreasonable use, the residues of such pesticides and their metabolites in agricultural products far exceed the national standard limits. Long-term consumption of food containing carbamate pesticide residues will induce nervous system diseases, along with carcinogenic, teratogenic and mutagenic effects on the human body, and lead to death in serious cases. Therefore, it is very important to monitor the residues of carbamate pesticides and their metabolites in agricultural products in real time to ensure food safety. This paper summarized and analyzed the commonly used pre-treatment technologies and detection methods of carbamate pesticides in agricultural products, introduced the characteristics of different pre-treatment technologies such as liquid-liquid extraction, solid-phase extraction and QuEChERS method for the extraction of these pesticides, and introduced the detection methods of enzyme inhibition assays and instrument analysis method respectively. The application characteristics of different detection methods for pesticide residues were analyzed, and new detection technologies and methods were prospeced, in order to provide references for the detection and safety supervision of carbamate pesticide residues in agricultural products, so as to ensure food safety and public health.

Objective To analyze the quality characteristics of Ripe Pu-erh tea from Pu'er City. Methods A total of 43 local fermented Ripe tea samples were collected from Pu'er City, and the quality characteristics of this batch of products were systematically analyzed by sensory evaluation combined with biochemical component detection. Results The color dry tea leaves were brown or reddish brown; the infusion were brown red or reddish brown; the aroma were mellow aged fragrance; the taste had typical pure characteristics of stale aroma; the infused leaves were reddish-brown and soft. Biochemical detection data showed that the content of tea sample water extract, tea polyphenols, free amino acids, soluble sugar and theabrownin in these tea samples were 38.7%-51.5%, 4.55%-11.16%, 1.56%-2.89%, 3.49%-8.27% and 6.84%-12.82%, respectively. The total content of catechins and flavonols were 6.76-18.23 mg/g and 0.18-1.90 mg/g, respectively. The content of theophylline and caffeine were 0.01-0.12 mg/g and 15.21-27.31 mg/g, respectively. The content of gallic acid was 1.22-6.56 mg/g. Conclusion Compared with the Ripe Pu-erh tea from other regions, Pu'er City-fermented tea samples demonstrates significantly higher levels of water extract, soluble sugars and free amino acids, coupled with relatively lower caffeine content. This distinctive biochemical composition corresponds to their sensory profile characterized by a thick mellow taste, pronounced sweetness, and reduces bitterness in the tea infusion. The study systematically delineates the sensory quality attributes and biochemical reference ranges of Ripe Pu-erh tea fermented in Pu'er City, providing scientific data support for future cross-regional comparative studies on the quality characteristics of Pu-erh tea.

Objective To establish a method for the determination of 9 kinds of organic acids (oxalic acid, tartaric acid, quinic acid, malic acid, lactic acid, citric acid, fumaric acid, succinic acid and gallic acid) in fruits and vegetable crisps by liquid chromatography-high resolution mass spectrometry (LC-HRMS). Methods The samples were cleaned up by a SAX solid-phase extraction column. The samples were eluted with 0.1% formic acid in water and methanol as mobile phases and separated on an Eclipse Plus C₁₈ column (4.6 mm×250 mm, 5 μm), and monitored in electron spray ionization (ESI)- mode and quantified by external standard method. Results The calibration curves for 9 kinds of organic acids showed good linearity in the concentration range of 50-5000 ng/mL. The correlation coefficients (r) were all greater than 0.9991, the limits of detection (LODs) were in the range of 1-10 ng/mL, the limits of quantitation (LOQs) were in the range of 10-50 ng/mL, the spiked recoveries were in the range of 96%-98%, and the relative standard deviations (RSDs) were in the range of 1.5%-4.9%. Among them, lactic acid [(16.16±0.30) mg/g] and citric acid [(15.53±0.11) mg/g] were the main organic acids in the fruit and vegetable crisps, and their content was significantly higher than those of other organic acids. In contrast, tartaric acid [(1.29±0.11) mg/g] and oxalic acid [(1.56±0.25) mg/g] were found at lower levels. Conclusion The method is simple, rapid, and accurate and can be used for the qualitative and quantitative determination of organic acids (oxalic acid, tartaric acid, quinic acid, malic acid, lactic acid, citric acid, fumaric acid, succinic acid and gallic acid) in fruit and vegetable crumbles as well as other food.

Objective To establish spectrophotometric method for the rapid determination of the content of 4 kinds of polyethylene nonionic surfactants. Methods The complex formed by the reaction between polyethylene-type nonionic surfactant and iodine solution exhibits corresponding light absorption at a specific wavelength. Based on the direct proportionality between the absorbance value and the concentration of the polyethylene-type nonionic surfactant, this relationship can be utilized for quantitative determination. The influences of absorption wavelength, temperature, time and other factors on the determination of nonionic surfactants were studied to achieve the best reaction conditions. Results The detection conditions were: Wavelength at 525 nm, 10 min and 25 ℃. Good linearity was observed in the range 0-30 mg/L, and the correlation coefficients were ranged from 0.9962 to 0.9988. The limits of detection were ranged from 0.0012 to 0.0022 mg/L. The relative standard deviations of samples were ranged from 0.9% to 5.1%, and the spiked recoveries were ranged from 87.2% to 91.7%. Conclusion The method is simple, accurate and credible, which is suitable for rapid detection of polyethoxylated nonionic surfactants.

Objective To optimize the extraction process of total polyphenols in Artemisia capillaris and study the content of it in Henan Province. Methods A single factor optimization combined with response surface optimization was used to establish the optimal method for extracting total polyphenols from Artemisia capillaris, mainly examining the effects of solid-liquid ratio, ethanol volume fraction, extraction time and extraction temperature on the extraction of total polyphenols from Artemisia capillaris. The samples of Artemisia capillaris were taken from 18 cities in Henan Province, and the total polyphenol content in Artemisia capillaris was analyzed based on soil type and distribution area. Results The best values of 4 factors were as follows: Solid-liquid ratio 1:30 (m:V), ethanol concentration 50%, extraction time 72 min, extraction temperature 63 ℃, and the best extraction rate of total polyphenols was 1.85%. With the best values of 4 factors, the total polyphenols in Artemisia capillaris from 18 regions in Henan was determined and analyzed. The highest value appears in Anyang and the lowest value appears in Zhengzhou. According to the types of soil, the tide soil had the highest value of total polyphenols, which was 7.51 mg/g, and the paddy soil had the lowest value of total polyphenols, which was 6.15 mg/g. Conclusion The method optimized by this study is stable, reliable and economy. The model established can predict the extraction rate of total polyphenols well. The content of total polyphenols in Artemisia capillaris from different regions in Henan is discrepant. But the discrepancy is not significant according to the soil types.

Objective To develop an ultra performance liquid chromatography-tandem mass spectrometry method for the determination of Nisin residues in various foods. Methods The samples were extracted with 0.1% formic acid solution+acetonitrile (80:20, V:V), delipid with n-hexane, eluted with 0.1% formic acid solution and acetonitrile as mobile phase gradient, and separated by ZORBAX Eclipse Plus C₁₈ (100 mm×2.1 mm, 1.8 μm). Electrospray ion source and positive ion multi-reaction monitoring mode were used for detection, and matrix matching standard curve external standard method was used for quantification. Results The linear relationship between Nisin A and Nisin Z was good in the range of 0.5 to 50.0 μg/mL, and the correlation coefficient was greater than 0.995. The limits of detection and quantitation were 0.05 to 0.30 mg/kg and 0.15 to 1.00 mg/kg, respectively. The recoveries ranged from 88.8% to 106.2% and the relative standard deviations were 1.32% to 8.85% at the 3 added levels of 1.0, 5.0 and 200.0 mg/kg. Conclusion The established method is fast, efficient, repeatable, sensitive and accurate, and can be used for the determination of Nisin A and Nisin Z in batch food samples.

Objective To optimize the processing technology of red glutinous sorghum cookies by response surface methodology. Methods Based on single-factor experiments, the sensory score of red glutinous sorghum cookies was taken as the response value, and the process of red glutinous sorghum cookies was optimized by response surface methodology. Results Based on the basic ratio of total flour 500 g, with other ingredients accounting for the proportion of total flour as butter 75.6%, powdered sugar 37.8%, milk 5.5%, and whole egg liquid 16.8%, and using a 12-tooth piping tip for shaping, the optimal process was that the proportion of red glutinous sorghum flour in the total flour was 53%, the baking time was 24 min, and the baking temperature was 158 ℃. Through verification, the cookies made under these conditions had a complete shape, an attractive color, a crispy texture, and the best sensory quality. Conclusion This process is stable and reliable for processing glutinous sorghum cookies, and the research results can provide theoretical support for the processing of glutinous sorghum cookies.

Objective To establish a rapid visual detection method for Aspergillus niger in Zea mays L. by loop-mediated isothermal amplification (LAMP) technology. Methods Based on LAMP technology, specific primers targeting the key ochratoxin A (OTA) biosynthesis gene OTAhal were designed. Through screening of the primers and optimization of conditions such as primer sequence, primer ratio, reaction temperature and visual dye, the optimal detection conditions were determined. Using the total DNA of Aspergillus niger and artificially contaminated corn samples as templates, the sensitivity of the detection method and the feasibility of its practical application were validated. Results The optimal primer ratio was 8:4:1, the optimal reaction temperature was 64 °C, and the method could complete the amplification of target DNA within 30 minutes. The color of the positive sample changed from violet to blue-purple. This method could detect DNA concentrations as low as 6.87×10⁻³ ng/μL. When applied to actual Zea mays L. sample testing, it achieved a detection limit as low as 10¹ spores/mL. Conclusion This method is simple to operate, highly sensitive, and does not require sophisticated instruments. It can be applied to the detection of OTA in actual Zea mays L. samples, indicating broad application prospects.

Objective To study on the improvement of incubation time and plate load capacity for molds enumeration. Methods Mold quality control samples were tested according to GB 4789.15—2016 National food safety standard-Food microbiological examination-Enumeration of moulds and yeasts, with additional colony counting performed on the second day of incubation. The plate size was increased from 90 mm to 150 mm, and statistical analysis was employed to assess the differences between colony counts and the reference value of the quality control samples. Results Significant discrepancies were observed between the fifth-day counting result at the critical dilution (1:10) and the reference value. A sharp decline in colony counts was noted when the colony-forming units exceeded 30 CFU per 90 mm plate, which was defined in this study as the maximum load capacity of mold plates under acceptable accuracy. By adopting 150 mm plates with a 2-day incubation period, the original load capacity was overcome, yielding counting results that aligned well with the reference value. Under these optimized conditions, the linear coefficient of determination (R²) between sample means and dilution factors improved from R²₉₀=0.614 to R²₁₅₀=0.998. Conclusion The optimized testing conditions effectively addressed the issues of colony overgrowth and poor linearity in mold plate count experiments, thereby enhancing the accuracy of test results.

Objective To establish a method for the simultaneous determination of 19 kinds of common preservatives, sweeteners and synthetic colorants in beverages by high performance liquid chromatography (HPLC). Methods HPLC was employed with an ACE Excel 5 C₁₈ column (4.6 mm×250 mm, 5 μm) at a flow rate of 1.0 mL/min. Gradient elution was performed using 20 mmol/L ammonium acetate (pH 7.5) and methanol as the mobile phases, and detection was carried out using a diode array multi-wavelength detector. Results Effective separation of all 19 kinds of food additives was achieved. The linear range of the method was 0.5-50.0 μg/mL, with correlation coefficients above 0.9998. The average recovery rates ranged from 92.26% to 104.59%, with relative standard deviations (RSDs) between 0.45% and 1.67%. The limits of detection were 0.07-0.29 mg/kg, and the limits of quantitation were 0.23-0.96 mg/kg, both of which were below the national standards and met the detection requirements. Conclusion This method is simple to operate, requires short pre-treatment time, provides good separation efficiency, accurate data, and high sensitivity, making it suitable for the simultaneous determination of 19 kinds of food additives in beverages.