Objective To establish a visual detection method of Salmonella based on recombinant enzyme polymerase amplification-CRISPR/Cas12a. Methods In this study, recombinase polymerase amplification (PRA) was combined with clustered regularly interspaced short palindromic repeats/associated protein 12a (CRISPR/Cas12a) system. RPA primers and CRISPR-derived RNA (crRNA) were designed and synthesized based on the target invA gene of Salmonella. Fluorescence and test strip methods were employed to read the results. The optimized RPA-CRISPR/Cas12 detection system were evaluated for specificity and sensitivity, and was applied to the detection of food samples. Results Nano gold test strip base on nucleic acid were developed. The established RPA-CRISPR/Cas12 detection method could specifically detecting Salmonella with a sensitivity of 80 CFU/mL within 1.5 h. Used this method to detect 21 kinds of food samples, the results from fluorescence and test strip read were consistent, with a Salmonella detection rate of 4.8%, which was completely consistent with the results of the national standard method. Conclusion The Salmonella RPA-CRISPR/Cas12a visual detection method established in this study has high specificity and sensitivity and is valuable for on-site rapid detection of Salmonella.

Objective To understand the contamination distribution and drug resistance of Enterobacteriaceae bacteria in 3 types of food in Handan Area, and to build a contamination database of foodborne Enterobacteriaceae. Methods Food and drug substances, food for special diet, nuts and seeds and their processed products were collected in Handan City from 2023 to 2024. Enterobacteriaceae were isolated and identified by matrix-assisted laser desorption/ionization-time of flight-mass spectrometry, and quantitative count and drug sensitivity test of Enterobacteriaceae were performed. Results Among 196 food samples, 22 samples were positive for Enterobacteriaceae, positive rate 11.2%. The detection rate of Enterobacteriaceae in bulk food was 20.0% higher than 6.3% in pre-packaged food, and the difference was statistically significant (χ²=8.415, P<0.05). The total contamination of Enterobacteriaceae ranged from 1.00-4.67 lg CFU/g. The 31 strains of Enterobacteriaceae were identified in 22 positive foods, including 17 kinds of bacteria from 9 genera. In the drug susceptibility test of 15 kinds of antibiotics, 32.26% of Enterobacteriaceae bacteria were drug-resistant strains, and the resistance rates of ampicillin (25.81%) and ceftazidime (12.90%) were relatively high, while the resistance rates of chloramphenicol,compound sulfamethoxazole tablets, colistin, cefotaxime, ampicillin/sulbactam and tetracycline were relatively low (all resistance rates≤10.00%). The sensitivity to ertapenem, meropenem, ceftazidime/avibactam, tigacycline, ciprofloxacin, nalidixic acid and amikacin was 100.00%. One strain of Leclercia adecarboxylata was detected in bulk jujube, which was resistant to the most types of antibiotics. Conclusion There is a certain degree of Enterobacteriae bacteria contamination in food in Handan Area, and the contamination rate of bulk food is significantly higher than that of pre-packaged food. A wide variety of Enterobacteriae bacteria are detected, and the drug resistance of different bacteria is significantly different. Targeted monitoring should be further strengthened to prevent and control foodborne diseases.

Objective To understand the metal element contamination in liquid milk in Inner Mongolia region from 2022 to 2023 and assess the metal health exposure risk for the population in Inner Mongolia region. Methods A total of 4103 samples of locally produced liquid milk were collected from Inner Mongolia region. Lead, total mercury, cadmium, chromium and total arsenic were detected using inductively coupled plasma mass spectrometry. The inverno comprehensive pollution index method was used to evaluate the pollution levels of these elements. Considering the actual dietary intake of residents in Inner Mongolia region, the carcinogenic risk assessment (TCR) and non-carcinogenic risk assessment [target hazard quotient (THQ)] were employed to assess the health risks posed by metal elements in liquid milk to the population in Inner Mongolia region. Results In the 4013 samples monitored, all 5 kinds of metal elements were detected. The over-limit detection rate for lead was 22.26% (187/840), for cadmium it was 5.83% (49/840), for total mercury it was 5.12% (43/840), for total arsenic it was 6.54% (55/841), and for chromium it was 40.18% (262/652). Lead, total mercury, and total arsenic all had samples exceeding the limits, with exceedance rates of 5.83% (49/840), 0.119% (1/841), and 0.12% (1/841), respectively. The inverno index for all 5 kinds of metal elements was below 0.7; the TCR for total arsenic and cadmium was less than 10^-4, Within an acceptable risk range; THQ of lead, chromium, and total mercury were all less than 1. Conclusion This study systematically analyzed and comprehensively assessed the sources of heavy metal pollution in liquid milk from different production and processing types, providing a scientific basis for government decision-making, regulation, and the revision of national food safety standards.

Objective To optimize two kinds of detection methods in GB/T 37514—2019 Animal and vegetable fats and oils-Determination of mineral oils. Methods The saponification time was extended from 5 min to 10 min; a turbidimeter was introduced to measure the turbidity value of the saponified sample solution; a commercially available aluminum foil plate was used instead of the homemade alumina thin-layer plate; and 3 kinds of mineral oils were added to compare with the liquid paraffin in the standard. Results The turbidity values of some edible oils decreased to different degrees after prolonging the saponification time; the lowest limits of detection of diesel and liquid paraffin could reach 0.2% after replacing the aluminum foil plate; the limits of detection of different mineral oils by different methods were all different. Although the sensitivity of the optimized method was improved, it still did not fully meet the ideal standard for the detection of very small amounts of mineral oil residues in food safety regulation. Conclusion We call on the relevant departments to accelerate the improvement of the standardization system for the detection of mineral oil in food, and to promote the establishment of a more sensitive and scientific standard for the detection of mineral oil, so as to ensure the safety and quality of the edible oil market and to safeguard public health.

Objective To deeply analyze the sensory quality of flavor during the ripening process of red cheese through various methods for measuring food flavor quality. Methods The volatile flavor compounds and sensory quality of red cheese at different ripening periods were analyzed by solid phase microextraction arrow-gas chromatography-mass spectrometry (SPME arrow-GC-MS), electronic nose, electronic tongue, and quantitative descriptive analysis (QDA). Results The results showed that there were differences in the flavor profiles of red cheeses at different ripening periods. A total of 85 kinds of volatile flavor compounds were identified in red cheese by GC-MS. The total content of acids, alcohols, aldehydes, and ketones first increased and then decreased, while the total content of esters continued to increase. Combined with the relative odor activity value (ROAV) analysis, 28 kinds of characteristic volatile flavor compounds were identified. QDA yielded that yogurt flavor, wine flavor, and sour flavor would enhance significantly (P<0.05) during cheese ripening. In addition, electronic tongue analysis demonstrated significant differences in sourness and bitter aftertaste among red cheeses at different ripening periods (P<0.05). Conclusion This study analyzes and compares the sensory quality of flavor during the ripening process of red cheese from multiple perspectives by combining various methods for measuring food flavor quality. This study not only improves the understanding of the sensory qualities of red cheese but also provides a reference for the development, quality control, and flavor improvement of novel fermented dairy products.

Objective To screen lactic acid bacteria strains with strong ethanol stress resistance and investigate the effects of their biofilms under different ethanol concentrations and environmental disturbances. Methods The growth, biofilm formation, morphological changes and hydrophobicity of various lactic acid bacteria under ethanol stress were examined. The effects of different metal ions and D-galactose on the growth and biofilm formation of lactic acid bacteria were also explored. Results After 48 h of fermentation under 10% ethanol stress, the biomass and biofilm amount of Lacticaseibacillus paracasei were 1.16 and 0.12, respectively. After 24 h of fermentation, its hydrophobicity reached 42.80%, significantly higher than that of Lactiplantibacillus plantarum, Lacticaseibacillus casei, and Limosilactobacillus fermentum, indicating better ethanol stress resistance. Scanning electron microscopy showed that the thickness of the biofilm decreased significantly with increasing ethanol concentration. The addition of D-galactose and metal ions (Ca²⁺, Na⁺) significantly inhibited biofilm formation. Conclusion Lactic acid bacteria resist ethanol stress through biofilm formation, with ethanol stress resistance correlating closely to biofilm production. D-galactose and metal ions affect the growth and biofilm formation of lactic acid bacteria. This study reveals the relationship between ethanol stress resistance and biofilm formation in lactic acid bacteria, provides a theoretical basis and data support for developing lactic acid bacteria biopreparations suitable for high-ethanol food fermentation environments.

Objective To investigate the effects of low-temperature fermentation processes and fermentation duration on the aroma composition and aromatic characteristics of summer-harvested Jingshan black tea. Methods First, headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) combined with sensory evaluation was used to analyze the aroma components of 12 samples fermented at 3 temperatures (25, 28 and 35 ℃) and four durations (2.5, 4.0, 5.5 and 7.0 h). Second, principal component analysis (PCA) and hierarchical cluster analysis (HCA) were employed to explore the differences among samples under varying fermentation conditions (temperature and duration). Finally, Orthogonal partial least squares-discriminant analysis (OPLS-DA) with variable importance projection (VIP) scores and relative odorant activity value (OAV) was conducted to screen differential volatile compounds related to fermentation conditions. Results A total of 86 kinds of aroma components were analyzed and identified by the above-mentioned methods. Among them, 15 kinds of substances, such as dimethyl sulfide, linalool, (E,E)-2,4-heptadienal, indole and geraniol, were identified as the key differential volatile compounds under different fermentation conditions (temperature and time). Compared with other fermentation time samples, 4.0 h samples had higher concentration of volatile compounds and better quality. Among the samples with a 4.0 h fermentation duration, the samples fermented at 25 ℃ and 28 ℃ obtained higher sensory scores and presented distinct aroma profiles. At this duration, 25 ℃ and 4.0 h-fermented samples displayed floral aromas dominated by dimethyl sulfide, dehydro-linalool, linalool and neral, while 28 ℃ and 4.0 h-fermented samples exhibited fruity notes characterized by myrcene, citral and geraniol. Conclusion Low-temperature fermentation processes and fermentation duration critically influence the aromatic quality of Jingshan black tea.

Objective To investigate the effects of Bacillus natto fermentation on the quality characteristics and storage stability of Arachis hypogaea L. natto produced from red Arachis hypogaea L.. Methods A novel Arachis hypogaea L. product, Arachis hypogaea L. natto, was prepared through fermentation using Bacillus natto, and its quality characteristics and storage stability were systematically evaluated. In this study, the protein content, fat content and flavor compounds of Arachis hypogaea L. natto were determined. Sensory scores and L^* were monitored during the storage period. Additionally, the levels of total volatile basic nitrogen (TVB-N), amino acid nitrogen and a^* were assessed. Results The results indicated that compared with unfermented Arachis hypogaea L., the protein content of Arachis hypogaea L. natto decreased to 25.84%, and the fat content reduced to 17.72%. Fermentation promoted the production of alcohol and aromatic compounds, resulting in distinct flavor profiles characterized by sourness, saltiness, umami and bitterness. During fermentation, lipolysis produced linoleic acid, leading to a reduction in fat content. Moreover, some free water became less mobile, transitioning into weakly bound water. Over time, the sensory score and L^* and b^* of Arachis hypogaea L. natto declined, whereas the levels of TVB-N, amino acid nitrogen increased. Conclusion Bacillus natto fermentation significantly alters the nutritional composition and flavor characteristics of Arachis hypogaea L. natto. sensory quality deteriorates during storage. These findings provide a theoretical foundation for utilizing Bacillus natto in Arachis hypogaea L. fermentation and offer new insights into developing innovative Arachis hypogaea L. products.

The safety problem caused by the illegal addition of non edible substances to food has become a major threat to public health. However, there are still some significant limitations in the existing detection technology system, such as blind areas and a lack of detection ability. With the advantages of high-throughput screening and identification of unknown substances, non targeted detection technology has made great progress in the fields of emerging contaminants, multi-residue detection of agricultural and veterinary drugs and among others. This paper introduced the detection techniques of non-edible substances such as spectrum, chromatography and chromatography-mass spectrometry. The principle and application of non targeted detection technology and the application and limitation of non targeted detection screening based on database, mass spectrometry splitting characteristics and metabonomics were described in detail. The problems and challenges of non targeted detection technology in practical application were discussed. And innovatively put forward suggestions to promote the practical transformation of non targeted detection technology and the optimization path based on the fusion of non targeted detection technology analysis strategy and big data algorithm. The purpose of this paper was to provide a theoretical basis for the establishment of an efficient, accurate and green methodology system for non targeted detection of non-edible substances in food.

Silicon is an essential trace element for the human body and generally exists in mineral water in the form of metasilicic acid. The accurate detection of metasilicic acid, a crucial boundary indicator for natural mineral water, is essential for determining compliance within quality standards. The GB 8538—2022 China national food safety standard—Testing methods for natural mineral drinking water specifies 2 kinds of spectrophotometric techniques, the silicomolybdic yellow method and the silicomolybdic blue method, for the detection of metasilicic acid. However, due to factors such as the stability of colorimetric solutions in spectroscopic analysis and differences in absorption wavelengths, the application of these 2 kinds of methods in metasilicic acid detection still presents issues that require further improvement. Researchers have also reported a number of determination methods for metasilicic acid based on different technologies, such as flow injection (FI), inductively coupled plasma optical emission spectrometry (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS), ion chromatography (IC), high performance liquid chromatography (HPLC). This article compared the advantages and existing problems of these methods, so as to provide references for the improvement of existing methods and the development of new methods for metasilicic acid determination.