Objective To establish an enzyme-linked immunosorbent assay method for detecting soybean agglutinin in legume foods. Methods After washed the sample, added phosphate buffer solution and homogenize it thoroughly. After centrifugation and purification, collected the supernatant and determine it by enzyme-linked immunosorbent assay. Quantify it used an enzyme-linked immunosorbent assay reader. Result In the linear range of 0-400 μg/mL, the linear equation of soybean agglutinin obtained was Y=0.0021X+0.0528, r=0.9998. The detection limit of this method was 125 mg/kg, the recovery rate was between 99.17% and 101.20%, and the relative standard deviation was between 1.27%-2.24%. Conclusion This method is easy to operate, has good specificity, and the antigen concentration is directly proportional to the OD₄₅₀ value. Applicable to the detection of soybean agglutinin poisoning incidents by grassroots disease control centers.

Objective To establish a novel electrochemical sensing platform based on multi-walled carbon nanotube (MWNT) modified electrode for rapid detection of melamine (MEL) in dairy products. Methods An electrochemical sensor for MEL detection was constructed by employing cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques, using a MWNT-modified glassy carbon electrode (GCE) as the sensing probe. The constructed sensor was successfully applied to detect and analyze melamine in real-world milk powder samples.Results After modification with MWNT, the effective surface area of the bare GCE increased by 1.3 fold. The MWNT-modified electrode significantly enhanced the electrochemical reaction kinetics of the system. The MEL electrochemical sensor, using the MWNT-modified GCE as the probe, exhibited a linear detection range of 10-40 μmol/L and a sensitivity of 23.85 (μA/mmol)/cm². The detected MEL content in real milk powder samples complied with the Chinese national standard requirements. Conclusion The construction of the MEL electrochemical sensor using MWNT-modified electrodes has been demonstrated to be feasible. The construction method of the MEL sensor is simple, the good repeatability and stability of the MEL sensor are exhibited, the anti-interference capability and accuracy of the MEL sensor are excellent. Based on above advantages, the MEL sensor is applied widely.

Objective To study the effects of different concentrations of 1-methylcyclopropene (1-MCP) and phytic acid (PA) on the physiology and storage quality of Lycopersicon esculentum Mill.. Methods Based on the optimal concentration of 1-MCP and PA alone, the study was carried out under the conditions of room temperature (20±1) ℃ and relative humidity (80%-90%), and Lycopersicon esculentum Mill. without preservative treatment were used as the control, the full factorial composite experiments of 0.8 μL/L and 1 μL/L 1-MCP and 0.05% and 0.1% PA were carried out, and measured the mass loss rate, hardness, soluble solids content (SSC), ethylene release, peroxidase (POD) activity, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging rate, and sensory evaluation of Lycopersicon esculentum Mill. during the storage period. Results The 1 μL/L 1-MCP+0.1% PA treatment group had a sensory evaluation score of 85.6 after 12 d of storage, with a weight loss of 0.93%, hardness of 5.04 kg/cm², SSC content of 8.4%, ethylene release of 0.4398 μL/(kg·h), and POD vigour and DPPH radical scavenging rates of 96.9 U/g FW and 82.60%. Conclusion This study show that 1 μL/L 1-MCP+0.1% PA compound treatment is more helpful for the improvement of POD activity and DPPH radical scavenging rate, which in turn delayed the loss of quality, hardness and SSC, low ethylene release, and the overall maintenance of higher sensory scores, which effectively maintained a better storage quality and prolonged the freshness period of Lycopersicon esculentum Mill., and provided technical references for the freshness preservation of more categories of fruits and vegetables. It provides a technical reference for more categories of fruits and vegetables.

Objective To compare the bactericidal effects of high pressure (HP), slightly acidic electrolyzed water (SAEW) their combination (HP-SAEW) and thermd treatment (T), slightly acidic electrolyzed water combination treatment (T-SAEW) on Escherichia coli at the surface of Panax notoginseng fresh slices. Methods The E. coli was being used as the model bacteria and the standard plate counting method was adopted to determine the colony count of E. coli. The bactericidal effects of the two parallel treatment methods (HP-SAEW and T-SAEW) on Panax notoginseng fresh slices under different factors (solid-liquid ratio, processing times, available chlorine concentration (ACC), pressure and temperature) were studied and the synergistic effect analysis were further measured. Results The HP-SAEW parallel processing exhibited synergistic effect on the Panax notoginseng fresh sliced within a certain range of ACC (27.6-52.2 mg/L), pressure (98.5-297.5 MPa), solid-liquid ratio (1.76-5.88 g/mL), and processing time (5.56-9.48 min). The bactericidal effect of the HP-SAEW parallel treatment was better than that treated alone (SAEW or HP). The T-SAEW parallel processing exhibited synergistic effect on the Panax notoginseng fresh sliced within a certain range of ACC (25.44-46.88 mg/L), temperature (39.78-53.85 ℃), solid-liquid ratio (2.27-4.42 g/mL), and processing time (5.02-9.84 min). The bactericidal effect of the T-SAEW parallel treatment was better than that treated alone (SAEW or T). Conclusion The parallel combined effect has synergistic enhancement effect in the specific processing parameter range, T-SAEW parallel technology can more effectively inhibit the growth of surface microorganisms in fresh slices. On this basis, the quality change in the storage process of fresh Panax notoginseng can be carried out and applied in the actual production process in the future work.

Objective To construct a quality evaluation system for locally-produced grapes in Shanghai based on the key characteristic quality indicators. Methods By measuring 14 sensory and internal nutritional indicators of 57 batches of samples from 4 grape varieties, factor analysis was employed to screen out 8 core indicators, including soluble solids, total acids, solid-acid ratio, tartaric acid, glucose, zinc, vitamin C, and anthocyanins. Based on cluster analysis and the analytic hierarchy process (AHP), a three-level grading standard and weight distribution were determined, and a comprehensive scoring system was constructed. Results Results showed that the quality indicators of soluble solids, glucose, vitamin C and anthocyanins were relatively high in “Ju Meigui” variety, which had the highest average comprehensive score (81.6 points), and was significantly superior to “Zuijinxiang” (68.4 points), “Yangguang Meigui” (64.4 points), and “Shenyuan” (62.8 points). Conclusion The evaluation system established in this study exhibits high discriminant accuracy and can provide a reliable scientific basis for the quality grading, variety optimization, and market promotion of Shanghai-produced grapes.

Objective To study the effects of two kinds of processing techniques, ultrafine grinding and spray drying, on the metabolites of apple powder. Methods Liquid chromatography-tandem mass spectrometry was used to compare the effects of ultrafine grinding and spray drying technologies on the types of metabolites, expression abundance, correlation analysis, and kyoto encyclopedia of genes and genomes (KEGG) pathways of apple powder. Results The results indicated that compared with ultrafine grinding, spray-dried apple powder had reduced particle size D[50] 3.91 μm, D[3,2] 2.62 μm, D[4,3] 5.52 μm, increased specific surface area (850.10 m²/kg), and decreased span value (2.51). Principal component analysis showed that the cumulative variance contribution rate of apple powder under these two processing technologies was 82.7%, suggesting that the processing methods had a significant influence on the metabolite composition. A total of 244 metabolites were identified, including lipids, phenylpropanoids, and benzenoids. Abundance expression showed that ultrafine grinding outperformed spray drying in retaining natural nutritional components. The sample correlation analysis and heatmaps indicated that metabolite expression in spray-dried apple powder had higher uniformity and stability. Univariate statistical analysis revealed that, compared with ultrafine grinding, spray-dried apple powder had 1172 kinds of substances upregulated and 2550 kinds of substances downregulated. Differential metabolite correlation analysis showed that different processing techniques were positively correlated with specific metabolites in apple powder, such as ginsenoside F1 and N-fructosyl pyroglutamate, and negatively correlated with salicylic acid and aspartic acid, among others. KEGG pathway enrichment analysis highlighted the most active pathway as the biosynthesis of unsaturated fatty acids. Conclusion It has been demonstrated that ultrafine grinding is suitable for the production of healthy and special nutritional food products, while spray drying is more appropriate for quick-service foods and the baking industry, laying a theoretical foundation for ensuring food safety and quality control.

Objective To screen risk markers in the storage process of pork using ultra performance liquid chromatography-quadrupole-orbitrap high resolution mass spectrometry (UPLC-Q-Orbitrap HRMS) combined with chemometrics. Methods After sample pretreatment, UPLC-Q-Orbitrap HRMS was employed to detect metabolites in pork, obtaining high precision chromatographic and mass spectrometric data. Principal component analysis (PCA) was applied for dimensionality reduction to explore the distribution characteristics among samples. Orthogonal partial least squares-discriminant analysis (OPLS-DA) was then used to screen differential metabolites with a variable importance factor (VIP)>1.0. The statistical significance of the differences was further evaluated using T-tests (P<0.05), and the final key metabolites were confirmed by combining fold change analysis (fold change, FC>2 or FC<0.5). Results PCA revealed that storage temperature significantly influenced metabolite distribution in different pork cuts (loin, belly, and ham), with samples under different temperatures showing clear separation in the principal component space (total variance R²=0.861, predictive ability Q²=0.478). The OPLS-DA model further optimized the separation of intergroup differences (R²=0.811, Q²=0.653), making the impact of storage temperature on metabolite abundance and type more evident. The R² and Q² values of the real model were significantly higher than those of the permutation model, confirming the reliability of the analysis. Through screening conditions (VIP>1, P<0.05, FC>2 or FC<0.5) and structural verification, N-acetylputrescine and 6-methylquinoline were identified as risk markers. Conclusion UPLC-Q-Orbitrap HRMS combined with chemometrics effectively screens risk markers in pork during storage.

Objective To investigate the vitamin content in common 48 kinds of desserts in Gansu Province based on the requirements of national nutritional monitoring. Methods A total of 48 kinds of common desserts from Gansu Province were analyzed. The content of vitamin A, carotene, vitamin B₁, vitamin B₂, vitamin C, vitamin E and vitamin E fractions, i.e. (α-tocopherol, β-tocopherol, γ-tocopherol and δ-tocopherol) were determined by high performance liquid chromatography method as specifiedin the national standard for food safety. Results The results showed that among the 48 kinds of desserts, except for vitamin B₁, the detection rates of other vitamins ranged from high to low: Vitamin E>vitamin B₂>vitamin A>carotene>vitamin C; the content of vitamin A in the sample is ND-549.000 μg/100 g, median of 20.000 μg/100 g; the content of carotene was ND-142.650 μg/100 g, median of 0.250 μg/100 g. The content of vitamin B₂ was ND-0.226 mg/100 g, median of 0.090 mg/100 g; The content of vitamin C was ND-4.740 mg/100 g, median of 0.250 mg/100 g. The detected content of vitamin E (sum of various subtypes) ranges was ND-549.000 mg/100 g, median of 21.650 mg/100 g; the content of α-tocopherol was ND-2.690 mg/100 g, median of 1.015 mg/100 g; the content of β-tocopherol was ND-1.240 mg/100 g, median of 0.020 mg/100 g; the content of γ-tocopherol was ND-11.810 mg/100 g, median of 1.135 mg/100 g; the content of δ-tocopherol was ND-2.040 mg/100 g, median of 0.020 mg/100 g. Conclusion The fat-soluble vitamins are generally detected at higher levels in the samples from Gansu Province, while the water-soluble vitamins are detected at lower levels.

Objective To establish a high-throughput sequencing method for detecting cereal allergen species based on next-generation sequencing technology. Methods Taking Hordeum vulgare, Triticum aestivum, Fagopyrum esculentum and Fagopyrum tataricum as research objects, next-generation sequencing technology was used for the high-throughput identification of cereal allergen samples with different proportions and mixing methods and commercially available samples were collected to verify the method’s applicability. Results In different proportions of simulated samples, Hordeum vulgare, Triticum aestivum, Fagopyrum esculentum and Fagopyrum tataricum were detected, the limit of detection was as low as 0.1%, but the measured relative abundance of species and the actual amount of different additives; in different mixing methods but the same proportion of simulated samples, cereal allergens had been detected; the relative abundance of DNA mixing and mixing of raw materials and raw material mixing methods were different from the actual amount of species, and raw material mixing methods of species relative abundance closer to the exact amount of additives; commercial samples contained varying degrees of grain allergens, while a small number of samples with the ingredient list or label. Conclusion The detection method established in this study enables specific and simultaneous identification of 4 cereal allergens (Triticum aestivum, Hordeum vulgare, Fagopyrum esculentum and Fagopyrum tataricum). By conducting relative quantitative analysis of species abundance, the method can effectively determine the content of cereal allergens in samples.

Objective To optimize the acid hydrolysis-Fehling reagent titration method and the acid hydrolysis-3,5-dinitrosalicylic acid (DNS) colorimetric method to compare the consistency of different methods for measuring starch content in grain crop samples. Methods Experimental conditions, including ethanol washing volume, acid addition volume, acid hydrolysis time, sample solution pH, detection wavelength, chromogenic agent volume, color development time and color development temperature, were optimized to determine the optimal processing conditions for determining the starch content in such products. Results The optimal conditions for the acid hydrolysis-Fehling reagent titration method were as follows: After weighing the sample, fats and soluble sugars were removed using an appropriate amount of petroleum ether and ethanol; 25 mL of hydrochloric acid was added, followed by condensation reflux for 120 minutes; the hydrolyzed sample solution was neutralized with sodium hydroxide, filtered, and the filtrate was titrated with alkaline copper tartrate methyl and ethyl solution at a rate of one drop every 2 seconds. The optimal conditions for the acid hydrolysis-DNS colorimetric method were as follows: After removing fat, sugar and acid hydrolysis, the sample solution pH was adjusted to 8-9; for samples with color and high protein content, 10 mL of lead acetate was added to reduce or eliminate pigment interference; after filtration, 2 mL of DNS was added to the filtrate, followed by color development in a water bath at 90-100 °C for 12 minutes; the absorbance was measured at 540 nm using a spectrophotometer, and the determination was completed within 4 hours. Both methods had a relative standard deviation (RSD) of less than 2% and a relative error (RE) of less than 4%. The measurement results had passed mean consistency test and paired samples t-test. Conclusion The 2 kinds of optimized methods are more efficient and accurate compared to the national standard method, with good accuracy and precision making them suitable for starch content determination in grain crops.