To establish a method for determination of fipronil and its metabolites in meat by amino functionalized magnetic nanomaterials purification-high performance liquid chromatography-mass spectrometry.

The samples were ultrasonically extracted with acetonitrile-water. The extract was purified by amino-functionalized magnetic nanoparticles, and then concentrated under nitrogen. The residue was dissolved in acetonitrile-water (7:3, V:V) to a final volume. The analyte solution was analyzed using a C₁₈ column with methanol and water as the mobile phase under negative electrospray ionization mode. The data was collected using the multi reaction monitoring mode. The samples were analyzed based on the external standard method.

Under the established conditions, the target substances were well separated and showed a good linear relationship within the range of 1.0–20.0 ng/mL, with a correlation coefficient (r²) greater than 0.99. The limit of detection was 0.2 µg/kg and the limit of quantitation was 0.5 µg/kg. Through spiked recovery experiments, the recovery rates at 3 spiked levels ranged from 79.94% to 94.52%, with relative standard deviations of 2.95% to 8.22%.

Compared with traditional pretreatment methods, the proposed method utilizes a magnetic suction frame to absorb magnetism,which can eliminate the centrifugation steps, save time, ensure good reproducibility and reduce detection costs. The proposed method can be used to determine fipronil and its metabolites in meat. The establishment method can provide technical support for monitoring the residues of fipronil and its metabolites in meat on the market supervision.

To elucidate the differences in molecular epidemiological characteristics, antibiotic resistance and virulence properties of methicillin-resistant Staphylococcus aureus (MRSA) ST59 and ST398 in retail pork in the Hanzhong, and assess their potential public health risks.

Whole-genome sequencing was used to perform multilocus sequence typing (MLST), staphylococcal protein A gene (spa) typing, and staphylococcal cassette chromosome mec (SCCmec) typing for the isolates, and their resistance and virulence gene profiles were predicted. Antimicrobial susceptibility testing was conducted using the broth microdilution method; sheep red blood cell hemolysis test was used to evaluate hemolytic activity, and microplate crystal violet staining was employed to assess biofilm-forming ability.

Among the 43 MRSA isolates, ST59 (51.16%, 22/43) and ST398 (46.51%,20/43) were the dominant types. ST59 strains showed high homogeneity in molecular typing, mainly clustering in spa t437 (81.82%) and SCCmec IVa(2B) (90.91%); in contrast, ST398 strains exhibited high genetic diversity with various spa types and SCCmec types. The resistance rates of ST398 strains to gentamicin, tetracycline, levofloxacin,clindamycin and trimethoprim-sulfamethoxazole were significantly higher than those of ST59 strains (P<0.01).ST398 strains carried more abundant acquired resistance genes, including high carriage rates of tet(M) (95.00%),lnu(B) (75.00%), lsa(E) (90.00%) and dfrG (90.00%). Additionally, 3 strains carried the poxtA gene; while the resistance gene profile of ST59 strains was relatively simple. In terms of virulence characteristics, ST398 strains showed strong hemolytic activity; ST59 strains had stronger biofilm-forming ability and carried a more complex virulence gene profile, with significantly higher carriage rates of immune escape genes sak, scn, and enterotoxin genes seb, sek, seq compared to ST398 strains.

The main prevalent clones of MRSA in retail pork products in Hanzhong are ST59 and ST398. The different biological characteristics pose differential challenges to public health, requiring targeted monitoring and prevention measures.

To explore the microbial diversity among 4 kinds of Kefir granules from different regions.

Traditional separation and purification, molecular biology technology, high-throughput sequencing and other methods were used to explore the microbial diversity in Kefir granules from different sources. The 4 kinds of Kefir yogurt were fermented with 8% inoculum. The protein content, total acid, pH and water holding capacity of yogurt were analyzed and compared, and their texture characteristics were determined by texture analyzer.

At the species level, the dominant fungi shared by Kefir granules from 4 kinds of regions were Kazachstania unispora and Kluyveromyces marxianus, and the dominant bacteria were Lactobacillus kefiranofaciens and Lactobacillus kefir. There were a total of 35 operational taxonomic units (OTUs) in fungi, among which 4 kinds of Kefir granules had a total of 3 OTUs. There were 12 bacterial OTUs in total, of which 3 were common to the 4 kinds of Kefir granules. German fermented yogurt had good viscosity but with high acidity, and Chinese fermented yogurt had high chewiness but with poor water holding capacity. Russian fermented yoghurt had good water holding capacity and most texture properties, but its chewiness was poor. Fermented milk in the United States had the highest protein content, but poor texture properties.

This study reveals the microbial diversity of Kefir granules from different sources and its significant impact on the quality of yogurt. Chinese Kefir granules, with Kluyveromyces maximus as the dominant strain, endow yogurt with unique flavor and high chewiness. German samples show excellent stickiness,but their too high acidity required process optimization. The differences in microbial communities directly lead to regional characteristics in the physicochemical and textural properties of yogurt, providing a theoretical basis for the targeted screening of Kefir agents.

To investigate the contamination level of phthalate esters (PAEs) plasticizers in marketed liquors, compare the content of PAEs in different types of alcohol samples and samples collected from different sampling links, evaluate the exposure risk of citizens of Hanghzou.

The contamination status of PAEs in 97 marketed liquors samples was investigated using gas chromatography-tandem mass spectrometry (GC-MS/MS),and a point estimate method was applied to assess the dietary exposure of Hangzhou residents to PAEs.

The 7 kinds of plasticizers including dimethyl phthalate (DMP), diethyl phthalate (DEP), diisobutyl phthalate (DIBP),dibutyl phthalate (DBP), bis(2-ethoxyethyl) phthalate (DEEP), bis(2-ethylexyl) phthalate (DEHP) and bis(2-ethylhexyl) terephthalate (DOTP) were detected in liquors, the detection rates of DBP was the highest, it was 67.0%, but the detection rates of DEEP and DOTP were only 3.1% and 1.0%. The mean concentration values of DEP,DEEP and DOTP were blow the limit of detection (LOD). The 5 sample was detected above the limit value of DBP.The types, detection rate and concentration of the detected PAEs were different among the 6 kinds of liquors;meanwhile, the detection rate and concentration of PAEs were also different among the samples collected from the 3 kinds of different sampling links. The mean dietary exposure values for DMP, DIBP, DBP and DEHP were 0.01, 0.02,0.08 and 0.006 μg/(kg bw·d), hazard index (HI) was 1.2×10^–3.

The max exposure values of DIBP,DBP and DEHP in liquors are 0.1, 0.9 and 0.1 μg/(kg bw·d), respectively, all of which are less than the tolerable daily intake (TDI), HI is far less than 1 and the health risk of PAEs caused to drinking is low.

To investigate the contamination status of Burkholderia gladioli in edible fungi in Yunnan Province from 2022 to 2024, perform whole-genome sequencing on isolated strains, and analyze the genetic characteristics of toxin-producing strains.

A total of 724 samples were collected from Yunnan Province.The isolated and identified strains were subjected to second-generation whole-genome sequencing to analyze their genetic characteristics and the presence of bon gene clusters related to bongkrekic acid biosynthesis.

The detection rate of Burkholderia gladioli in the 724 samples was 12.85% (97/724), the detection rates of Auricularia auricula and Tremella fuciformis were 13.20% (61/462) and 12.87% (26/202) (P>0.05), respectively, with no statistical difference (P<0.05). The contamination of this bacterium had obvious regional differences (P>0.05), and the detection rate in the circulation link had no difference. The 17 samples were found to contain Burkholderia gladioli pathovar cocovenenans carrying complete bon gene clusters, but with varying toxin-producing abilities, 2 highly toxic cocovenenans variants were identified. Phylogenetic analysis showed that the 97 isolates were distributed on multiple branches of the evolutionary tree, with some isolates from Auricularia auricula and Tremella fuciformis showing a clear tendency to cluster. The bon gene clusters were highly consistent with the core genome phylogenetic tree.

There are significant regional differences in the contamination of Burkholderia gladioli in commercially available Auricularia auricula and Tremella fuciformis across Yunnan Province. Targeted food monitoring shall be implemented in high-risk prefectures.

To investigate and study the pesticide residue situation of fresh fruits and vegetables in Xining City from 2024 to 2025.

This study employed the enzyme inhibition method to conduct rapid detection and analysis of organophosphorus and carbamate pesticide residues in samples from a fresh agricultural product trading market and production sources in Xining City, involving 185 fresh vegetables and 125 fresh fruits.Specifically, 13464 batches of fresh vegetables and 5712 batches of fresh fruits, totaling 310 varieties and 19176 batches of samples were tested.

There were 30 vegetable varieties and 7 fruit varieties, and 60 batches of samples had been tested for pesticide residues exceeding the standard. Among them, the top 5 fruits and vegetables with the highest over-standard rates were cucumbers, stem lettuce, fragrant asparagus, drought-tolerant melon and eggplant. The inhibition rates of the samples with pesticide residues exceeding the standard ranged from 51.30% to 99.89%. The overall qualitative preliminary screening positive rate was 0.33%, and the pass rates were between 98.92%–99.94%. The overall sample pass rate was 99.67%, which was relatively high.

The pesticide residue situation of fresh fruits and vegetables in Xining City from 2024 to 2025 is at a relatively safe level, but there are still cases of pesticide residues exceeding the standard. It is recommended to strengthen detection continuously and monitoring to ensure food safety for citizens further.

To investigate the conditions for inducing expression levels of α-L-rhamnose glycosidase RhaB2 and its conversion of rutin, thereby enhancing the conversion rate of rutin to isoquercitrin.

Single-factor experiments examined the effects of induction temperature, duration and inducer concentration on enzyme expression levels. The effects of pH, temperature, incubation time and enzyme loading on RhaB2-mediated rutin conversion were also investigated.

Optimal expression conditions for recombinant α-L-rhamnose glycosidase RhaB2 in Escherichia coli BL21(DE3) were: Induction temperature 28 °C;induction time 20 hours; IPTG concentration 0.1 mmol/L. The optimal temperature for rutin conversion was 50 °C,with an optimal pH of 5.0. Under these conditions, a 2-hour reaction at a 2:1 enzyme-to-substrate mass ratio achieved a conversion rate of 99.96%.

In this study, a highly efficient heterologous expression system for recombinant α-L-rhamnosidase RhaB2 is successfully constructed. Under the technological conditions where the mass ratio of the enzyme to the substrate is 2:1 and the reaction time is 2 hours, the conversion rate of rutin can reach 99.96%, thus enabling the highly efficient and targeted preparation of isorhamnetin.

To investigate the heavy metal pollution and evaluate the dietary exposure risk of soy sauce in 2024.

This study collected 180 portions of soy sauce, including 139 portions of pre-packaged soy sauce and 41 portions of bulk soy sauce. Content of 7 kinds of elements including lead (Pb), cadmium (Cd),chromium (Cr), total arsenic (As), manganese (Mn), nickel (Ni) and copper (Cu) were determined by national standards. The pollution degree of Pb and As was evaluated by single-factor pollution index method (P_i) and nemerow comprehensive pollution index method (P_N). The dietary exposure risk was evaluated by target hazard quotient (THQ) and total target hazard quotient (TTHQ).

The heavy metals were detected in all soy sauces,but there were differences in the types of heavy metals. According to the limited requirements of GB 2762—2022 National food safety standard-Limits of contaminants in food (Pb≤1.0 mg/kg and As≤0.5 mg/kg), only Pb in the 139 portions of pre-packaged soy sauce was detected to have unqualified samples, with an unqualified rate of 2.16%.The average content of other detected heavy metals was sorted as Mn>Ni>Pb>Cr>Cu>As>Cd. The 41 portions of bulk soy sauce Pb and As met the limited quantity requirements. And the average content of other detected heavy metals was sorted as Mn>Ni>Cr>Pb. Out of 180 soy sauce samples, 3 pre packaged soy sauce samples had reached the pollution level for Pb, while the rest were safe. P_N showed that pre packaged soy sauce Pb was mildly contaminated,bulk soy sauce Pb was close to the warning line, and As was safe. The THQ and TTHQ values of heavy metals in all soy sauce were less than 1.

Most soy sauces have low contamination levels, only a small number of soy sauces are in mild and moderate contaminated. Therefore, the quality monitoring of soy sauce condiments should be strengthened. Under normal intake, the risk of dietary exposure of heavy metals in soy sauce is acceptable.

To explore the two-step enzymatic hydrolysis process for preparing walnut meal enzymatic peptides, and study their in vitro antioxidant and anti-fatigue activities.

Single-factor experiments and response surface experiments were used to determine the optimal two-step enzymatic hydrolysis method for preparing walnut meal enzymatic peptides. The antioxidant capacity was evaluated by determining the scavenging effects on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals, hydroxyl radicals, and superoxide anion radicals, as well as the total reducing power. The anti-fatigue effect was assessed using a mouse swimming exhaustion test.

The optimal combination for preparing walnut meal enzymatic peptides through two-step enzymatic hydrolysis was as follows: Alkaline protease at 2000 U/g, pH of 9.0 for alkaline protease, and flavor protease at 1000 U/g. Compared with ascorbic acid, the half-maximal inhibitory concentration for DPPH radical scavenging was (0.25±0.01) mg/mL, the half-maximal inhibitory concentration for hydroxyl radical scavenging was(0.96±0.01) mg/mL, and the half-maximal inhibitory concentration for superoxide anion radicals scavenging was(0.25±0.01) mg/mL, indicating that walnut meal enzymatic peptides had certain in vitro antioxidant activity. The mouse experiments revealed that walnut meal enzymatic peptides had no negative effects on mice and could effectively prolong their swimming time, maintain the levels of glycogen and antioxidant enzymes in the body, and reduce the accumulation of serum metabolic waste and peroxides, demonstrating a certain anti-fatigue effect.

The two-step enzymatic hydrolysis method is successfully used to prepare walnut meal enzymatic peptides with in vitro antioxidant and in vivo anti-fatigue activities, which have great application potential in the development of health foods or functional food ingredients with antioxidant and anti-fatigue functions.