Abstract:Thermo-reversible gels are widely applied in the processing of baking, meat, and snack products including cakes, candies, jelly, aspic, and steamed custard buns. Currently, the most effective thermo-reversible gel is gelatin, which can combine with water to form a transparent gel that melts when it is close to the temperature of the human oral cavity. However, gelatin is expensive. Therefore, researchers have turned their attention to polysaccharide gels, hoping to obtain more thermo-reversible food raw materials with different properties. The author reviews thermo-reversible polysaccharide gels from natural sources such as plants, algae, and microorganisms and those modified by physical, chemical, and enzymatic methods and summarizes the sources, structures, gelatinization mechanisms, and product applications of polysaccharide gels. It is expected to provide a reference for developing new thermo-reversible polysaccharide raw materials and promoting the application of new thermo-reversible polysaccharide gels in the food industry.

Abstract:The antioxidant properties of lactic acid bacteria are related to various probiotic activities, which can prevent and alleviate a variety of chronic diseases caused by oxidation in the host. The antioxidant mechanisms of lactic acid bacteria, including the action mechanisms of antioxidant enzymes and non-enzymatic antioxidants and regulation of host signaling pathways, were expounded. Furthermore, the application status of antioxidant properties of lactic acid bacteria in diseases of the nervous system, digestive system, and skin system were summarized. The aim is to explore how to enhance the antioxidant activity of lactic acid bacteria in oxidative stress-related diseases and give new insights into the development of related treatment strategies.

Abstract:[Objective] A genome-scale metabolic model (GSMM) of the high L-malic acid-producing strain Aspergillus oryzae (A. oryzae) FMME-S-38 was constructed and analyzed. [Method] The new GSMM iJW1333 was established for A. oryzae FMME-S-38 through a two-step process of draft reconstruction and model refinement. [Result] The model integrated 1 723 biochemical reactions, 1 723 metabolites, and 1 333 functional genes, achieving the prediction accuracy of 94.6% for substrate metabolism and 92.0% for cell growth. Comparative genomic analysis revealed that mutations in the genes involved in the hexose monophosphate pathway (HMP) and oxidative phosphorylation underpinned the enhanced L-malic acid production of A. oryzae FMME-S-38. Nitrogen source and cofactors (NADH and ATP) were identified as key determinants of efficient L-malic acid biosynthesis. Reducing the mass concentration of nitrogen source and the level of dissolved oxygen (DO) attenuated HMP while strengthening the reductive tricarboxylic acid (rTCA) branch, enabling A. oryzae FMME-S-38 to achieve an L-malic acid titer of (154.2±1.8) g/L.[Conclusion] This study clarifies the critical pathways and physiological mechanisms responsible for high L-malic acid production, providing a solid foundation for employing A. oryzae FMME-S-38 in the biosynthesis of other valuable metabolites.

Abstract:[Objective] Asprosin (ASP), an adipokine produced from fibrillin-1 (FBN1) cleavage, is closely linked to type 2 diabetes mellitus and obesity when its level is abnormal, demonstrating significant effect on human health. Therefore, monitoring the ASP level is crucial. The author aims to screen the nanobodies specifically binding to ASP via phage display technology, offering a new antibody component for the research on ASP. [Method] The antigenic epitopes of ASP were predicted by the online tools ABCpred and NovoPro, and then coupled with bovine serum albumin (BSA) to form the coating antigen (ASP-Epitope-BSA). After five rounds of bio-panning, the nanobodies specifically binding to ASP were screened from a nanobody phage display library. The selected nanobodies were induced for expression in Escherichia coli. The half median effect concentration (EC₅₀) values with ASP-Epitope-BSA and whole ASP antigen were determined, and the specificity was evaluated. Finally, homology modeling and molecular docking were performed to study the binding mode between the nanobody and ASP. [Result] One ASP-specific nanobody (VHH-19) was successfully screened out, with the induced expression level of 2.4 mg/dL in the LB culture with Escherichia coli. Performance evaluation showed that VHH-19 had EC₅₀ values of (87.49±0.27) ng/mL and (128.94±0.48) ng/mL for ASP-Epitope-BSA and whole ASP antigen, respectively, demonstrating good specificity. Homology modeling and molecular docking revealed that ASP was adsorbed in an active pocket formed by the CDR1 and CDR3 regions of VHH-19, forming a sandwich-like binding mode. The Try116, Gly126, Lys115, and Glu124 of ASP form hydrogen bonds and electrostatic interactions with Glu107, Arg31, and Arg33 of VHH-19, respectively. [Conclusion] This study rapidly obtained the ASP-specific nanobody VHH-19 by bio-affinity panning based on a natural nanobody phage display library.

Abstract:[Objective] This study aims to improve the properties of chestnut starch. [Method] Tea polysaccharides were added to chestnut starch in different proportions, and the effects of tea polysaccharides on the water-holding capacity, digestive properties, textural properties, and other properties of chestnut starch were investigated. [Result] The water-holding and oil-holding properties of chestnut starch were the largest when tea polysaccharides were added at 1% and then gradually decreased with the increase in the proportion of tea polysaccharides added. The transparency of chestnut starch gradually increased when tea polysaccharides were added from 1% to 8% and decreased significantly when tea polysaccharides were added at 16%. Adding tea polysaccharides at appropriate proportions significantly increased the solubility and swelling of chestnut starch. The addition of tea polysaccharides significantly reduced the water precipitation rate and improved the freeze-thaw stability of chestnut starch. The viscosity of chestnut starch gradually decreased with the increase in the proportion of tea polysaccharides added. The digestion test results indicated that the content of slowly digested starch and resistant starch in chestnut starch increased with the increase in the proportion of tea polysaccharides added. The hardness and elasticity of chestnut starch gradually decreased with the increase in the proportion of tea polysaccharides added. [Conclusion] Tea polysaccharides can significantly improve the properties of chestnut starch to a certain extent. The results provide a reference for the application of tea polysaccharides in the modification of chestnut starch and the development and utilization of chestnut starch resources.

Abstract:[Objective] This study aims to explore the ameliorating effects of flavonoids on atopic dermatitis (AD) and their structure-activity relationships. [Method] Flavonoids were selected through network pharmacology with interleukin-4 (IL-4) and interleukin-13 (IL-13) as key targets. The immunoglobulin E (IgE)-induced RBL-2H3 cell model was employed to evaluate the effects of flavonoids on inflammatory factors, degranulation activities, and calcium ion influx, and the structure-activity relationships were analyzed. Finally, molecular docking was utilized to assist in exploring the action mechanism. [Result] All of the six flavonoids (luteolin, apigenin, chrysin, quercetin, kaempferol, and fisetin) screened by network pharmacology had significant inhibitory effects on the expression of IL-4, IL-13, tumor necrosis factor-α (TNF-α), cell degranulation, and calcium ion influx. Among them, flavonoids with a hydroxyl group at the C-5 position and without hydroxyl groups at the C-3 and C-3’ positions (apigenin and chrysin) exhibited the strongest inhibitory activities. Flavonoids without a hydroxyl group at the C-3 position of the C ring (luteolin, apigenin, and chrysin) had relatively strong binding energy with signal pathways such as PLCγ, Lyn, and ERK. [Conclusion] This study provided new ideas for the development of dietary therapies for preventing and ameliorating AD.

Abstract:[Objective] The extraction efficiency of different methods and the effects of these methods on the composition of mannoproteins extracted from yeast cell walls were compared. Furthermore, the anti-inflammatory activities of the extracted mannoprotein were evaluated. [Method] Three yeast mannoproteins (MP-W, MP-B, and MP-E) were extracted via high-temperature water, alkali, and enzyme-assisted extraction methods and purified via ethanol precipitation. The identification of monosaccharide composition and amino acid composition, distribution of relative molecular mass, and Fourier transform infrared spectroscopy were employed to analyze the composition and chemical structures of yeast mannoproteins. A cell experiment was carried out to examine the anti-inflammatory activity. [Result] The yields of yeast mannoproteins extracted by the three methods were 9.7%, 11.5%, and 23.1%, respectively. The yield of MP-E was significantly higher than those of MP-W and MP-B. The yeast mannoproteins obtained were composed of mannose, glucose, and glucosamine, and the peak area proportion of glucose in MP-E was significantly higher than those in MP-W and MP-B. MP-E had significantly lower mass fractions of total amino acids and aspartate (Asp) and significantly higher mass fraction of threonine (Thr) than MP-W and MP-B. The weight-average molecular weights of the extracted yeast mannoproteins were 103 493, 106 579, and 118 286, respectively. Fourier transform infrared spectroscopy showed that all the three yeast mannoproteins were glycoproteins, with no significant difference in the main functional groups. At the mass concentration of 150 μg/mL, MP-E extremely outperformed MP-W (P<0.001) and MP-B (P<0.001) in increasing interleukin-10 secretion and inhibiting tumor necrosis factor-α secretion in RAW264.7 cells. [Conclusion] There is no significant difference in the main functional groups of yeast mannoproteins obtained by the three extraction methods. However, the enzyme-assisted extraction method can significantly improve the yield of yeast mannoprotein, and the obtained yeast mannoprotein shows higher anti-inflammatory activity. The findings provide a theoretical basis for the development and application of yeast mannoproteins.

Abstract:[Objective] This study aims to investigate the in vitro antioxidant and anti-inflammatory activities of Yunnan tea flower extract (TFE) and its Inhibitory effect on cell aging. [Method] The main active components in TFE were determined by ultraviolet (UV)-visible spectrophotometry and high performance liquid chromatography (HPLC). The antioxidant and anti-inflammatory activities of TFE were determined by the free radical scavenging assay and UV-induced photoaging model of human keratinocytes (HaCaT), respectively. After the aging model of fibroblasts was established, the aging level of cells was assessed by the β-galactosidase (β-gal) staining assay, and the expression of matrix metalloproteinase-1 (MMP-1), matrix metalloproteinase-3 (MMP-3), and type Ⅰ procollagen (PC-1) were determined by enzyme-linked immunosorbent assay. [Result] The mass fractions of total flavonoids, tea polyphenols, total proteins, and total sugars in TFE were 14.51%, 12.83%, 9.57%, and 50.34%, respectively. Ester-type catechins were the main tea polyphenols. The IC₅₀ in scavenging DPPH and ABTS free radicals were 34.32 μg/mL and 227.79 μg/mL, respectively. TFE significantly inhibited reactive oxygen species (ROS) production-induced by UV in HaCaT cells, down-regulated the expression of IL-6 and TNF-α, up-regulated the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1). In addition, TFE inhibited the aging of fibroblasts, down-regulated the expression of MMP-1 and MMP-3, and up-regulated the expression of PC-1. [Conclusion] TFE had strong antioxidant and anti-inflammatory activities. It can down-regulated the expression of MMP-1 and MMP-3 and up-regulated the expression of PC-1 to prevent cell aging, demonstrating potential anti-aging activity.

Abstract:[Objective] This study aims to establish the biosynthesis process of N-acetyl-trans-4-hydroxyproline (N-ATHOP). [Method]Escherichia coli (E. coli) BL21 (DE3) was selected as the host to heterologously express the acyltransferase (MsAcT) derived from Mycobacterium smegmatis. A semi-rational design was employed to construct the mutant MsAcT(S11C) capable of catalyzing the synthesis of N-ATHOP. [Result] The catalytic reaction conditions of the mutant MsAcT(S11C) were optimized as pH 6.9, reaction temperature 49 ℃, initial trans-4-hydroxyproline (THOP) concentration of 315.5 mmol/L, and vinyl acetate volume fraction of 10%. Under the optimized conditions, the yield of N-ATHOP synthesized under the catalysis of MsAcT(S11C) reached 4.71 g/L, with a conversion rate of 10.95% after 12 h of reaction. [Conclusion] The mutant MsAcT(S11C) successfully achieved microbial enzymatic biosynthesis from THOP to N-ATHOP.

Abstract:[Objective] This study aims to characterize the structure and investigate the solution properties of oat β-glucan (OBG). [Method] Two soluble OBGs with different weigh-average molecular weights (M_w), number-average molar weights (M_n), and peak molecular weights (M_p) were prepared by hot water extraction and ethanol classification. The structures and solution properties were characterized by Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), X-ray diffraction (XRD), scanning electron microscopy (SEM), high performance size exclusion chromatography coupled with multi-angle laser light scattering (HPSEC-MALLS), and rheology. [Result] OBG-1 and OBG-2 showed the M_w of 80.73×10⁴ g/mol and 8.05×10⁴ g/mol, the yields of (4.86±0.55)% and (3.32±0.31)%, and the purity of (94.21±0.17)% and (90.43±0.34)%, respectively. Both OBG-1 and OBG-2 were fibrous glucans composed of β-D-glucopyranose molecules linked by β-(1,3)-glycosidic and β-(1,4)-glycosidic bonds. OBG-1 contained more cellotriose and cellotetrose and had a smoother surface than OBG-2. In the aqueous solution, OBG-1 exhibited high viscosity and gel properties. [Conclusion] The method combining multiple instruments to characterize the structure and solution properties of OBG is more reliable than single characterization methods, providing a reference for the research on the activity and physiological functions of OBG.

Abstract:[Objective] This study prepared highly stable high internal phase emulsions (HIPEs) to encapsulate zeaxanthin, thereby improving the stability and expanding the food and pharmaceutical applications of zeaxanthin. [Method] HIPEs were prepared with the gelatin-chitosan suspension for encapsulation of zeaxanthin extracted from goji berries. Ultra-performance convergence chromatography (UPCC) was employed to separate zeaxanthin. Confocal laser scanning microscopy (CLSM) was employed to observe the emulsion structure. The rheological analysis was performed to characterize the emulsion, which was combined with the hydrogen peroxide and storage stability tests to evaluate the performance of encapsulation with HIPEs in improving the stability of zeaxanthin. [Result] The separation of zeaxanthin by UPCC needed only 2.14 min. The optimal preparation conditions for HIPEs were as follows: mass fractions of both gelatin and chitosan solutions were 0.50%, a gelatin-to-chitosan mass ratio of 4∶1, and pH 5. The CLSM results showed that HIPEs were successfully prepared with the gelatin-chitosan suspension. The rheological analysis results showed that HIPEs loaded with zeaxanthin exhibited solid-like elastic behavior, and their storage moduli were higher than loss moduli. The CLSM results showed that with the increase in the mass fraction of zeaxanthin, the oil droplets in zeaxanthin-loaded HIPEs were aggregated, extruded, and deformed, which gradually reduced the stability of the emulsion. The stability test results showed that compared with zeaxanthin directly dissolved in dodecane, the encapsulation in HIPEs effectively reduced the degradation rate of zeaxanthin and increased the retention rate after hydrogen peroxide treatment and storage at 4 ℃ by 17.98% and 90.09%, respectively. [Conclusion] Using HIPEs prepared with the gelatin-chitosan suspension for encapsulation helps to improve the stability and extend the shelf life of zeaxanthin, which provides a new strategy to overcome the limitations of zeaxanthin utilization.

Abstract:[Objective] This study prepared highly stable high internal phase emulsions (HIPEs) to encapsulate zeaxanthin, thereby improving the stability and expanding the food and pharmaceutical applications of zeaxanthin. [Method] HIPEs were prepared with the gelatin-chitosan suspension for encapsulation of zeaxanthin extracted from goji berries. Ultra-performance convergence chromatography (UPCC) was employed to separate zeaxanthin. Confocal laser scanning microscopy (CLSM) was employed to observe the emulsion structure. The rheological analysis was performed to characterize the emulsion, which was combined with the hydrogen peroxide and storage stability tests to evaluate the performance of encapsulation with HIPEs in improving the stability of zeaxanthin. [Result] The separation of zeaxanthin by UPCC needed only 2.14 min. The optimal preparation conditions for HIPEs were as follows: mass fractions of both gelatin and chitosan solutions were 0.50%, a gelatin-to-chitosan mass ratio of 4∶1, and pH 5. The CLSM results showed that HIPEs were successfully prepared with the gelatin-chitosan suspension. The rheological analysis results showed that HIPEs loaded with zeaxanthin exhibited solid-like elastic behavior, and their storage moduli were higher than loss moduli. The CLSM results showed that with the increase in the mass fraction of zeaxanthin, the oil droplets in zeaxanthin-loaded HIPEs were aggregated, extruded, and deformed, which gradually reduced the stability of the emulsion. The stability test results showed that compared with zeaxanthin directly dissolved in dodecane, the encapsulation in HIPEs effectively reduced the degradation rate of zeaxanthin and increased the retention rate after hydrogen peroxide treatment and storage at 4 ℃ by 17.98% and 90.09%, respectively. [Conclusion] Using HIPEs prepared with the gelatin-chitosan suspension for encapsulation helps to improve the stability and extend the shelf life of zeaxanthin, which provides a new strategy to overcome the limitations of zeaxanthin utilization.

Abstract:[Objective] This study aims to identify the main spoilage bacteria and evaluate their spoilage capacity in the spoilage process of pickles. [Method] High-throughput sequencing was employed to analyze the microbial community dynamics in the samples of pickles at the early, middle, and late stages of spoilage. The key spoilage bacteria were isolated, purified, and then identified through a combination of colony morphology observation, biochemical analysis, and 16S rDNA/ITS sequencing. Re-inoculation experiments were carried out for further validation of the primary spoilage bacteria in pickles. [Result]Acinetobacter and Bacillus were the dominant spoilage bacterial genera across the three spoilage stages. Notably, Bacillus exhibited rapid growth over time, with the relative abundance of 2.25%, 18.31%, and 44.19%, respectively, at the early, middle, and late stages of spoilage. This result indicated that the increase in the relative abundance of Bacillus might be the main cause of late spoilage in pickles. After isolation, purification, and identification, the five dominant spoilage bacterial strains were Bacillus velezensis, Acinetobacter baumannii, Virgibacillus salarius, Bacillus pumilus, and Pichia membranifaciens. The results of re-inoculation experiments showed that all the five strains affected the crispness of pickles, demonstrating considerable spoilage capacities. [Conclusion] These findings provide a theoretical foundation for targeted control against spoilage bacteria in pickles.

Abstract:[Objective] This study aims to evaluate the potential health risks to consumers from exposure to multiple mycotoxins in grains. [Method] Point and probabilistic assessment models were adopted to analyze the dietary exposure risks of adult residents in Shanghai to aflatoxins (AFs), ochratoxin A (OTA), zearalenone (ZEN), deoxynivalenols (DONs), and fumonisins (FBs) through consumption of rice, maize, soybeans, and wheat flour. [Result] The margin of exposure values (MoE) for AFs in maize and aflatoxin G₁ (AFG₁) in soybeans exceeded 10 000, indicating no dietary exposure risk. In contrast, AFs in rice and wheat flour, as well as aflatoxin B₁ (AFB₁), aflatoxin B₂ (AFB₂), and aflatoxin G₂ (AFG₂) in soybeans, showed MoE below 10 000, suggesting a minor health risk. The estimated daily intake (EDI) values of ZEN, DONs, and FBs from the four grains were below the provisional maximum tolerable daily intake (PMTDI), indicating no dietary risk. At the 95th percentile (P95) exposure level, the EDI of OTA from rice exceeded 100 ng/kg, while the risk quotient (RQ) of OTA in soybeans and DONs in wheat flour surpassed 100% under certain exposure scenarios, indicating a potential minor health risk. [Conclusion] Overall, the exposure to AFs, OTA, ZEN, DONs, and FBs through consumption of four grains among adult residents in Shanghai was within safe limits. However, certain mycotoxins posed potential health risks under high-exposure conditions. These findings provide scientific basis for the risk management of mycotoxins in grains in Shanghai.

Abstract:[Objective]This study aims to establish a rapid immunoassay method for the quantitative detection of eugenol.[Method]The eugenol monoclonal antibody was conjugated to the surface of quantum dots by the 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxy-succinamide (NHS) (EDC-NHS) coupling method, with quantum dots as fluorescent markers. Bovine serum albumin (BSA) was used for blocking, and fluorescence microscopy, agarose gel electrophoresis, and a microplate reader were used for identification. Furthermore, the established method was compared with high performance liquid chromatography (HPLC).[Result]The optimal synthesis conditions were as follows: quantum dot activation time of 30 min, conjugation pH with 8.0, antibody addition of 21 μL, and conjugation incubation time of 3.0 h. The optimal buffer system was as follows: carbonate buffered solution (CBS) with the coating buffer solution of 0.05 mol/L and pH 9.6, phosphate buffered solution (PBS) with the quantum dots-monoclonal antibody (QDs-mAb) concentration of 0.01 mol/L and pH 7.4. The quantum dots-fluorescence immunoassay (QDs-FIA) method was established under optimized conditions, with the linear equation of y=13.098ln x+9.625 8, R²=0.993 1. The IC₂₀, IC₅₀, and IC₈₀ were 2.21, 21.81, and 215.49 ng/mL, respectively. Recovery test were performed on water samples and bass meat samples, with recovery rate ranging from 96.32% to 103.01% for water samples and 94.16%~102.28% for bass meat samples, and the coefficients of variation were less than 7%.[Conclusion]The established QDs-FIA method has good sensitivity and accuracy, which can provide a theoretical basis for the development of fluorescent assay kit in the future.

Abstract:[Objective] This study aims to establish a magnetic bead enzyme-linked immunosorbent assay (MELISA) method for olaquindox (OLA) based on immunomagnetic beads.[Method] First, olaquindox-hapten conjugated with horseradish peroxidase (OLA-HS-HRP) and immunomagnetic beads were synthesized. Then, the conjugated immunomagnetic beads and OLA-HS-HRP were used to screen and optimize the reaction conditions of MELISA.[Result] The optimal working dilution factors for the immunomagnetic beads and OLA-HS-HRP were 100 times and 8 000 times, respectively, with the antibody dilution buffer being PBS solution (0.010 mol/L, pH 7.0) containing methanol at a volume fraction of 5%. Under the optimized conditions, the established standard equation was y=13.593ln x+17.173 (R²=0.994 3), with IC₁₀, IC₂₀, IC₅₀, and IC₈₀ values of 0.59, 1.23, 11.19, and 101.70 ng/mL, respectively. The recovery rate of this method was 93.17%~106.83%, and the coefficient of variation (CV) was <7%.[Conclusion]The MELISA established in this study is highly sensitive and reliable, providing a new method for the detection of OLA residues and offering a theoretical basis and reference for the detection of other small molecule drugs in food safety.

Abstract:[Objective] This study aims to comprehensively investigate the risk of veterinary drug residues inblack bone chicken. [Method] A method for rapid and simultaneous analysis of 39 veterinary drugs and theirmetabolites in three categories was established based on low-temperature ultrasonic extraction, solid-phaseextraction pretreatment, and ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The samples were extracted by Mcllvaine-Na2EDTA and phosphate buffer via ultrasonictreatment at low temperatures, purified by Oasis HLB solid-phase extraction column, separated by T3chromatographic column, and quantified by the matrix matching external standard method. [Result] The 39veterinary drugs and their metabolites showed good linear relationships in the matrix matching external standardsolutions with the mass concentration range of 2.0~500.0 μg/L, with the correlation coefficients greater than0.990. The limits of detection and quantification were 2.0 μg/kg and 10.0 μg/kg, respectively. The spike recoveryrates of the method ranged from 68% to 111% at fortified mass fractions of 10.0~100.0 μg/kg, and the relativestandard deviation (n=5) ranged from 0.65% to 15.12%. The method had high sensitivity and reliable qualitativeand quantitative results, meeting the requirements for the detection and analysis of veterinary drug residues inblack bone chicken. This method was then used to test 60 samples of black bone chicken sold on the market. Theresults showed that fluoroquinolones, tetracyclines, and sulfonamides were detected in commercial black bonechicken. The mass fraction of enrofloxacin, trimethoprim, and diaveridine exceeded the maximum residue limitsin two (153.187, 174.979 μg/kg), two (55.007, 111.391 μg/kg), and two (153.779, 189.801 μg/kg) samples,respectively. [Conclusion] There is a certain risk of the residues of sulfonamides in black bone chicken on themarket, and it is necessary to strengthen the supervision on use of antibiotics in black bone chicken breeding.