Abstract:[Objective]This study aims to investigate the application potential of okra polysaccharides(OPs)as a novel green humectant in tobacco and elucidate their dual mechanisms of moisture retention and pyrolysis-induced aroma enhancement.[Methods]Multiple detection and analytical techniques were employed to investigate on the monosaccharide composition of OPs,the microstructure of tobacco cut surface,the occurrence state of water,humectant performance,and the mechanism of pyrolysis-induced aroma enhancement.[Results]OPs were primarily composed of galactose(44.6%),rhamnose(25.8%)and galacturonic acid(15.6%),with abundant hydroxyl functional groups.After the application of OPs,the tobacco cut surface became fuller,with a significant increase in the proportion of bound water under low-humidity conditions(temperature(22±1)℃,relative humidity(32±2)%).The equilibrium moisture content of OPs-treated tobacco under the high-humidity environment(temperature(22±1)℃,relative humidity(84±2)%)and low-humidity conditions was 41.93%and 6.98%,respectively.The drying rate constant(k=0.684 5)decreased by 7.5%compared to the blank control group,indicating that its humectant performance was superior to propylene glycol and close to that of glycerol.Pyrolysis analysis revealed that OPs could generate various aromatic substances,including 5-hydroxymethylfurfural,furfuryl alcohol,2,5-dimethylpyrazine,and guaiacol,helping to enhance the richness of cigarette aroma and improve sensory comfort.[Conclusion]OPs possess dual functions of efficient humectant property and pyrolysis-induced aroma enhancement,demonstrating potential to replace traditional polyol-based humectants,thus providing a reference for the development of natural functional tobacco additives.

Abstract:[Objective]This study aims to improve the oxygen(O2)utilization rate of strains in the whole-cell catalytic reaction system and efficiently catalyze the synthesis of phenyllactic acid(PLA)from phenylalanine(PHE).[Methods]Based on the effect of heterologous expression of Vitreoscilla hemoglobin(VHb)on the growth of host Escherichia coli,genetic engineering technology was used to construct a multi-enzyme coupled expression system including VHb,L-amino acid deaminase(L-AAD)and lactate dehydrogenase(LDH).Subsequently,the expression regulation strategies of key enzymes were optimized,and the genetic stability of recombinant strains was evaluated by continuous passage experiments.[Results]Heterologous expression of VHb could improve the oxygen utilization rate of strains and significantly promote the growth rate and maximum biomass of host E.coli.In shake flask culture,the time for the strain to enter the logarithmic growth phase during the scale-up culture stage was shortened by 1.5 h,and the maximum biomass was increased by 46%when VHb expression was induced alone.The dominant recombinant strain E.coli BL21(pRSFDuet-aad-ldh-T7-rbs2-2vhb)was obtained by optimizing the VHb expression regulation strategy.Furthermore,the whole-cell catalytic reaction system was optimized,and the optimal reaction conditions were determined as follows:0.010 mol/L PBS buffer,pH 7.0,temperature 37℃,and rotation speed 250 r/min.Under these conditions,the maximum PLA yield of the dominant recombinant strain was 53.7 g/L;The dominant recombinant strain had good stability;after 10 consecutive passages,the change rate of PLA yield in each generation was less than 5%,showing potential to become an industrial strain.[Conclusion]Heterologous co-expression of VHb can promote the growth of E.coli and improve the yield of PLA via whole-cell catalysis.

Abstract:[Objective]This study aims to further elucidate the characteristics of volatile compounds,key aroma compounds,and differential components across four basic flavor-types and two blended flavor-types of Chinese Baijiu.[Methods]Using headspace solid-phase microextraction-gas chromatography-mass spectrometry(HS-SPME-GC-MS),relative odor activity value(ROAV)method,and orthogonal partial least squares-discriminant analysis(OPLS-DA),the distribution patterns of volatile compounds,identified key aroma compounds,and determined significant differential compounds among the six flavor-types were analyzed.[Results]A total of 207 volatile compounds were identified across the six flavor-types Chinese Baijiu,spanning 10 chemical categories—primarily esters,aromatic compounds,alcohols,alkenes,aldehydes,and ketones.Volatile compound composition exhibited significant differences among flavor-types:26 compounds were common to all types,77 compounds were unique to a single type,and 104 compounds were present in 2～5 types.Light flavor-type and Rice flavor-type Baijiu showed fewer volatile compound types,while both Taorong flavor-type and Mixed flavor-type Baijiu demonstrated greater similarity to Strong flavor-type and Soy Sauce flavor-type Baijiu in volatile compound composition.10 volatile compounds,including ethyl caproate,ethyl octanoate,and ethyl phenylacetate,were identified as key aroma compounds for one or more flavor-types.13 volatile compounds,such as ethyl caproate,ethyl myristate,ethyl hexadecanoate,and ethyl acetate,were classified as important differential compounds for distinguishing the six flavor-types.[Conclusion]Significant differences exist in volatile compound composition across Chinese Baijiu flavor-types,with key aroma compounds and differential compounds predominantly comprising ethyl esters.The scientific integration of production processes for basic flavor-types represents a critical technical pathway for developing innovative Chinese Baijiu flavor-types.

Abstract:Based on the medicinal and edible dual-purpose characteristics of Cornus officinalis,this review summarizes its main active components,health benefits and corresponding mechanisms of action,and further discusses the current research progress on its applications in health foods and common foods such as alcoholic beverages,beverages,and vinegar.The main active components of Cornus officinalis include polysaccharides,flavonoids,tannins,iridoids,triterpenoids,alcohols,organic acids and steroids,which exhibit various health benefits such as anti-tumor and hypoglycemic effects.Significant progress has been achieved in elucidating the mechanisms of the active components of Cornus officinalis,such as regulating the expression of tumor apoptotic factors,protecting pancreatic β cells,modulating inflammatory signaling pathways,and activating the activity of antioxidant enzymes.Although remarkable achievements have been made in the application research of Cornus officinalis in the food field,it is still confronted with numerous challenges,including the need for continuous exploration of active components,inadequate in-depth elucidation of mechanisms,lack of clinical data,insufficient product diversity,poor stability of active components,and uneven product quality.In the future,it is necessary to rely on modern technologies to systematically excavate the active components of Cornus officinalis,further investigate the efficacy mechanisms,and overcome the bioavailability bottleneck,so as to promote the further development and utilization of Cornus officinalis resources in China.

Abstract:[Objective]This study aims to explore the aroma-producing potential of endophytic bacteria in Ocimum×citriodorum.[Methods]Traditional isolation and culture method combined with morphological and molecular biological method were used to screen and identify the dominant aroma-producing strains from its roots,stems and leaves;then,the fermentation conditions were optimized by the single factor test and response surface method;and volatile oil was extracted by simultaneous distillation extraction(SDE)and subjected to cigarette flavoring evaluation.[Results]A total of 38 strains of endophytic bacteria were isolated.Sensory evaluation confirmed that strain J-3-6 had the best aroma quality,which was identified as Pantoea ananatis exhibiting a sweet jasmine aroma with indole as the main aroma-producing substance.The optimal fermentation conditions were as follows:lactose mass concentration of 10.2 g/L,yeast extract powder mass concentration of 50.7 g/L,liquid volume of 259 mL,inoculation amount of 7%,initial pH value of 7,fermentation temperature of 26℃,shaker rotation speed of 180 r/min,and fermentation time of 48 h.Under these conditions,the indole yield was 5.53 times the initial yield.A total of 45 volatile organic compounds were identified in the fermentation system,mainly composed of alcohols,esters and heterocyclic compounds.The aroma characteristics were based on a fresh fruity aroma,integrated with complex floral and woody notes.Cigarette flavoring evaluation showed that the most suitable addition level was 4 μg/cigarette.[Conclusion]Optimization of the fermentation conditions for Pantoea ananatis J-3-6 by the response surface method significantly enhances indole production,and its metabolites extracted as volatile oils can effectively harmonize tobacco aroma and reduce the offensive odor and irritation of cigarettes.

Abstract:Nicotine is the primary alkaloid in tobacco and its processing waste,featuring strong environmental persistence and high biotoxicity.Its emission poses potential hazards to the ecological environment and human health,rendering nicotine degradation a critical link in the green development of the tobacco industry and tobacco processing waste treatment.Compared with agricultural regulation measures,physical and chemical methods—which have limitations in energy consumption,cost,and aroma quality,microbial degradation has attracted considerable attention due to its high efficiency,specificity,and environmental benignity.This paper systematically summarizes the physicochemical properties of nicotine,treatment methods,as well as the main microbial groups for nicotine degradation,their degradation characteristics,and metabolic pathways.Genera such as Arthrobacter and Pseudomonas are currently the most extensively studied nicotine-degrading microorganisms,and they primarily convert nicotine into small-molecular-weight metabolites that can enter the tricarboxylic acid cycle via the pyridine pathway,pyrrolidine pathway,and VPP pathway,with key degrading enzymes playing a central role in these metabolic pathways.Additionally,this paper outlines the application prospects of microbial degradation of nicotine in fields including bioremediation of tobacco waste,tobacco processing and manufacturing,and biopharmaceuticals.Future research will address issues such as the poor environmental adaptability and unstable degradation efficiency of strains,and will focus on developing customized strains,constructing synthetic microbial communities,conducting multi-omics analysis,and optimizing metabolic processes to promote the industrialization of microbial nicotine degradation technology.

Abstract:[Objective]This study aims to explore the antibacterial effect of phages on Salmonella in food.[Methods]Phages were isolated and purified from wastewater samples collected from a wastewater treatment plant in Zhengzhou,with Salmonella typhimurium as the host bacterium,by the double-layer agar plate method.Their biological characteristics,genomic features,and antibacterial effects on S.typhimurium in artificially contaminated milk and egg white were investigated.[Results]The optimal multiplicity of infection(MOI)of the isolated and purified phage ST-1 was 0.1,with a maximum titer of 10.45 lg PFU/mL.Its latent period was 20 min,the lysis period was 70 min,and the burst size was approximately 106.5 PFU/cell.It had a narrow host range,being able to lyse only S.typhimurium and Streptococcus pneumoniae.It exhibited good stability,maintaining activity within a temperature range of 30～60℃and a pH range of 5～10,while also being insensitive to chloroform.Phage ST-1 belongs to the order Caudovirales.Its genome size is 84 672 bp,with a GC content of 38.82%,and it contains 142 open reading frames(ORFs).It does not carry resistance genes or virulence genes and can significantly inhibit the growth of S.typhimurium in artificially contaminated milk and egg white.[Conclusion]Phage ST-1 has high lysis efficiency,good thermal stability,acid-base tolerance,safety,and control effects,which can provide a reference for the development of targeted biocontrol agents against Salmonella.

Abstract:[Objective]This study aimed to reveal the effects of different fermentation temperatures on the taste quality and microbial flora of zha-chili.[Methods]The taste quality of zha-chili fermented at different temperatures(20℃,25℃,30℃,and 35℃)was evaluated using an electronic tongue technique,while its microbial community structure was analyzed via MiSeq high-throughput sequencing technology.Finally,the correlation between the microbial flora and taste quality was determined based on procrustes analysis.[Results]Significant differences were observed in both the taste quality and microbial flora structure of zha-chili under different fermentation temperatures(P<0.05).The dominant bacterial genera were Lactobacillus and Bacillus,while the major fungal genera included Hyphopichia,Aspergillus,Cladosporium,Gibberella,Kodamaea,and Meyerozyma.Among these,zha-chili fermented at 20℃exhibited a more prominent sour taste and a more favorable microbial composition:Lactobacillus was the dominant bacterial genus,and Hyphopichia was the major dominant fungal genus.Additionally,Acinetobacter,Rosenbergiella,and Cladosporium were identified as the key bacterial genera distinguishing its microbial community structure from the other three temperature groups.A significant correlation was found between the microbial flora and taste indexes of zha-chili fermented at different temperatures(P<0.05),and the interactions among dominant microorganisms collectively shaped the taste characteristics of zha-chili.[Conclusion]Zha-chili fermented at 20℃exhibits both higher microbial flora richness and better taste quality.

Abstract:[Objective]This study aimed to investigate the bacterial community diversity in red vinasse acid(a traditional fermented acidic food from Wuxuan County,Guangxi Zhuang Autonomous Region)and thereby provide potential microbial strain resources for red vinasse acid products.[Methods]MiSeq high-throughput sequencing technology was applied to analyze the bacterial α-diversity,community structure,and functional profiles of 12 red vinasse acid samples collected from Wuxuan County,Guangxi.And a pure culture technique was utilized to isolate and identify lactic acid bacteria(LAB).[Results]The dominant bacterial phyla in the samples were Firmicutes and Proteobacteria,with average relative abundances of 90.17%and 9.17%,respectively.The dominant bacterial genera were Lactobacillus,Pediococcus,and Levilactobacillus,with average relative abundances of 32.18%,20.54%,and 11.62%,respectively.The samples exhibited relatively high abundances in the transport and metabolism of carbohydrates and amino acids.A total of 29 LAB strains were isolated from the 12 samples,which belong to 6 species of 5 genera.Among them,the dominant cultivable LAB species were Lactiplantibacillus pentosus and P.acidilactici,accounting for 44.83%and 24.14%of the total LAB isolates,respectively.[Conclusion]Red vinasse acid from the Wuxuan region exhibits high bacterial diversity and abundant LAB resources,and thus can serve as microbial strain resources for the industrial production of red vinasse acid.

Abstract:[Objective]This study aims to investigate the differences in sensory styles and their formation mechanisms among three medium-sized cigarettes.[Methods]Thermal desorption(TDU)coupled with comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry(GC×GC-TOFMS)was used to detect the volatile aroma compounds in the tobacco cuts of three medium-sized cigarettes.Combined with sensory evaluation,orthogonal partial least squares discriminant analysis(OPLS-DA)and partial least squares regression(PLSR),this study comparatively analyzed the formation mechanisms of aroma style differences among the three medium-sized cigarettes.[Results]The three medium-sized cigarettes have different aroma profiles.,the NX sample features prominent sweet and herbal notes,the LT sample is characterized by distinct fruity notes,and the SD sample highlights fresh and clean notes.A total of 102 volatile aroma compounds were detected in the three medium-sized cigarettes,among which 29 characteristic key aroma compounds had potential effects on the formation of differences in cigarette aroma styles.PLSR analysis revealed that these 29 aroma compounds were respectively correlated with different aroma style characteristics of cigarettes,and the differences in their contents might be the reason for the differences in aroma styles among the three cigarettes.[Conclusion]This study enriches the flavor analysis method and research findings of medium-sized cigarettes and provide a reference for the regulation of aroma styles in medium-sized cigarettes.

Abstract:[Objective]This study aims to explore and optimize a green and efficient extraction technology for Chuanminshen violaceum polysaccharide(CVP)and promote its development and utilization in the field of functional foods.[Methods]A deep eutectic solvents(DES)-based extraction method for CVP was established and optimized via single-factor experiments and response surface methodology.Subsequently,the extracted CVP was purified by ion-exchange chromatography column and gel filtration chromatography column,respectively.The structure of CVP was characterized by combining ion chromatography,high-performance gel permeation chromatography,infrared spectroscopy,and scanning electron microscopy.[Results]The optimal extraction conditions were determined as follows:choline chloride-citric acid DES system(with a molar ratio of 1∶1 and a water content of 30%),liquid-to-solid ratio of 20∶1,extraction temperature of 70℃,and extraction time of 120 min.Under these conditions,the extraction rate of CVP was(44.17±0.19)%,an increase of more than 26%over the traditional extraction method;After purification,two CVP fractions(CVP-1-1 and CVP-2-1)with single relative molecular weight and homogeneous structure were obtained.Among them,CVP-1-1 was composed of glucose and galactose,with a total sugar content of(94.87±0.80)%and a relative molecular weight of 9471 Da;CVP-2-1 was composed of glucose,galactose and rhamnose,with a total sugar content of(92.01±1.77)%and a relative molecular weight of 18 159 Da;Both fractions were pyranose ring polysaccharides containing α-glycosidic bonds and β-glycosidic bonds.Their micro-morphologies were related to relative molecular weight and purification process;the purified polysaccharides exhibited a more porous and loose surface,a higher degree of fragmentation,and differed in relative molecular weight,as well as the degree of fragmentation and aggregation.[Conclusion]Applying DES to CVP extraction,the extraction rate is significantly increased compared with the traditional extraction method.Moreover,the obtained CVP has a lower relative molecular weight,which may have high antioxidant activity,providing a reference for the development of CVP-based functional foods.

Abstract:[Objective]To investigate the effects of plasma-activated water(PAW)treatment on the oxidation characteristics and in vitro digestion behavior of pale,soft,exudative-like chicken protein isolate(PPI).[Methods]PPI was extracted from PSE-like chicken and treated with PAW for different activation times.A systematic analysis was performed to evaluate changes in free radical signal intensity,ultraviolet absorption spectrum,carbonyl content,di-tyrosine content,free amino groups,and free sulfhydryl groups of PPI before and after PAW treatment.In vitro protein digestibility(IVPD),peptide content,and essential amino acid content of digestion products were also quantified.[Results]As activation time increased,PAW exhibited a significant decrease in pH(P<0.05)and significant increases in oxidation-reduction potential(ORP),electrical conductivity,and NO-content(P<0.05).PAW treatment significantly increased free radical signal intensity and ultraviolet absorption intensity of PPI,specifically elevating carbonyl and di-tyrosine contents while reducing free amino and free sulfhydryl contents(P<0.05).Notably,PPI40 showed a 3-fold in carbonyl content and 53.7%reduction in free sulfhydryl content compared to PPI0.For digestion characteristics,PAW treatment significantly increased IVPD,peptide content,and essential amino acid content(P<0.05),with IVPD of PPI40 increasing by 25.15%compared to PPI0.[Conclusion]PAW treatment promotes PPI oxidation and enhances its digestive characteristics.

Abstract:[Objective]To enhance the sensory quality and industrial usability of Shaanxi-origin tobacco leaves.[Methods]Metagenomic sequencing was employed to characterize the dynamic shifts in surface microbiota of tobacco filaments during Bacillus thuringiensis 116 fermentation.This approach aimed to elucidate the functional roles of dominant strains and their correlations with aroma compound profiles,facilitating the identification of optimal mixed-strain fermentation formulations.[Results]During B.thuringiensis 116 fermentation of SXZL tobacco filaments,the dominant bacterial genera included Sphingomonas,Pseudomonas,Enterobacter,Kosakonia,Pantoea,and Methylobacterium.Positive correlations were observed between the relative abundances of Bacillus,B.terrae,Enterobacter,and Kosakonia and the concentrations of 3-oxo-α-ionol,megastigmatrienone,and damascenone.Bacillus abundance also showed positive correlations with B.terrae,Enterobacter,and Kosakonia.Compared to single-strain fermentation,co-fermentation with B.thuringiensis 116 and Bacillus Y7 improved smoke intensity and quality,enhanced aroma volatility,increased sweetness,and refined aftertaste comfort.The concentrations of damascenone,scopoletin,and 3-oxo-α-ionol increased by 140.10%,133.51%,and 104.51%,respectively.Significant elevations were also noted in the relative changes of 3-oxo-α-ionol,4-hydroxy-β-dihydrodamascone,curcumin,and kauraldehyde.[Conclusion]Mixed-strain fermentation significantly increases aroma compound concentrations in tobacco filaments and improves the sensory quality of cigarettes.

Abstract:[Objective]To enhance the efficiency of cigarette blend formulation maintenance,this study proposes a method based on non-parametric kernel density estimation(KDE)for evaluating the similarity of cigarette blend formulations.[Methods]A KDE distribution model for individual chemical components was constructed using historical formulation data to calculate the similarity of individual chemical components.Different weight allocation strategies were employed to compare the similarity between the experimental formulation and historical formulations.The model's performance was evaluated using correlation analysis,and the relationship between the overall similarity of leaf group formulations and sensory quality was analyzed.[Results]The probability density estimation function fitted using KDE effectively reflects the distribution of chemical component data from historical formulations.Compared with the experimental leaf groups,the average overall similarity of the leaf group formulations that passed evaluation to historical formulations in three indicators(sugar-alkaloid ratio,total nitrogen content,and reducing sugar content)increased by 30.57%,18.97%,and 13.06%,respectively.Although the four weighting methods exhibited similar correlation levels,they differed in their tendency regarding the correlation degree of individual chemical component similarity.Specifically,the game theory-based combined weighting method showed correlations with most sensory indicators that were intermediate between those of subjective and objective weighting methods,thereby reducing the overall weight deviation between these two approaches.[Conclusion]Constructed a KDE distribution model using historical formulation data to evaluate the similarity between experimental formulations and historical formulations.The results provide a reference for assessing and controlling the similarity and stability of leaf groups during the formulation maintenance process.

Abstract:[Objective]To systematically evaluate the antioxidant properties of cerium oxide and elucidate its protective efficacy against UVA-and simulated sunlight-induced photoaging.[Methods]The antioxidant properties of cerium oxide were assessed through DPPH·,superoxide anion(O2-·),and hydroxyl radical(·OH)scavenging assays.Its recyclable antioxidant capacity was evaluated using an H2O2 recycling scavenging assay.In vitro photodamage models were established in human skin fibroblasts(HFF-1)using UVA irradiation and a solar simulator,followed by measurements of cellular viability and expression levels of type Ⅰ(COL-Ⅰ)and type Ⅲ(COL-Ⅲ)collagen.[Results]Cerium oxide exhibited significant antioxidant capacity.At a concentration of 6 mg/mL,it showed scavenging efficiencies of 83.42％,30.29％,and 48.50％for DPPH·,O2-·,and·OH radicals respectively.After three H2O2 recycling cycles,these efficiencies remained above 90％,confirming excellent recyclable antioxidant properties.Compared to the negative control,cerium oxide at 0.078 mg/mL increased HFF-1 cell viability by 38.78％under UVA irradiation.At this concentration,COL-Ⅰ expression showed a 77.0-fold increase relative to the control group.In simulated sunlight-induced damage,cerium oxide at 0.039 mg/mL increased COL-Ⅲ expression to 14.06 ng/mL,representing a 1.5-fold increase compared to the negative control group.[Conclusion]Cerium oxide demonstrates potent recyclable radical scavenging properties.By upregulating COL-Ⅰ and COL-Ⅲ expression,it significantly mitigates UVA-and simulated sunlight-induced photoaging damage in HFF-1 cells,indicating considerable potential for development as a novel antioxidant and anti-photoaging active ingredient.

Abstract:[Objective]To investigate the moisture-retaining performance of a novel tobacco humectant system based on amino acid-glycerol supramolecular complexes.[Methods]Fourteen amino acid-glycerol complexes were synthesized and screened using techniques including thermogravimetric analysis,Zeta-potential measurement,water adsorption tests,tobacco moisture retention assays,molecular dynamics simulations,and scanning electron microscopy to evaluate their moisture-proof and moisture-retaining properties.[Results]Among the 14 complexes,the L-histidine/glycerol complex demonstrated superior stability.At 20℃and 80%RH,it showed lower water adsorption capacity than glycerol,indicating its moisture-barrier function.At 20℃and 60%RH,its equilibrium moisture content(13.27%)satisfied tobacco moisture protection requirements.[Conclusion]The complex forms via supramolecular interactions,adheres to tobacco leaf surfaces,and promotes stomatal closure to reduce water loss and prevent external moisture intrusion,thereby providing effective moisture-proof and moisture-retaining properties.

Abstract:[Objective]To improve the food processing adaptability and practical value of Japonica rice.[Methods]Heat-moisture treatment(moisture content:25%)was used for the modification of Japonica rice.The effects of ethanol at 40%,80%,and 120%of the moisture content on structural properties(amylose content,morphology,crystalline structure)and functional properties(pasting properties,cooking loss,digestibility)were systematically investigated.[Results]Heat-moisture treatment significantly reduced the amylose content and A-type crystallinity,while promoting the formation of V-type crystalline structures.This enhanced thermal stability and reduced viscosity and cooking loss.The addition of ethanol did not alter the crystalline structure type but induced microstructural disruption,reducing A-type crystallinity while increasing amylose content and V-type crystalline formation.Moderate ethanol concentrations(40%～80%)caused greater disruption of A-type structures and promoted V-type crystallization,thereby improving thermal stability and rapidly digestible starch content while decreasing viscosity and cooking loss.At 120%ethanol concentration,A-type crystallinity remained stable but V-type crystalline formation decreased,leading to reduced thermal stability,increased viscosity and cooking loss,and elevated slowly digestible starch content.[Conclusion]The structural and functional properties of Japonica rice can be precisely modulated by controlling ethanol concentrations during heat-moisture treatment.

Abstract:[Objective]To investigate differences in aroma components of tobacco leaves before and after bacterial-enzyme synergistic treatment.[Methods]A strain of Bacillus velezensis YUNM-4,isolated from the surface of Yunyan 87 tobacco leaves,was combined with cellulase,lipase,and neutral protease to formulate a composite enzyme preparation.This preparation was applied in synergistic fermentation of upper low-grade flue-cured tobacco leaves.Conventional chemical components and aroma components of fermented tobacco leaves were analyzed using a continuous flow analyzer and gas chromatography-mass spectrometry(GC-MS),respectively.Orthogonal partial least squares discriminant analysis(OPLS-DA)and independent t-tests(P<0.05)were employed to identify components with significant content differences between pre-and post-fermentation samples,while relative odor activity values(ROAV)were applied to analyze differences in aroma component contributions.[Results]1)Compared to the control group,fermented tobacco leaves exhibited significant decreases in total potassium,nicotine,total sugar,reducing sugar,and K/Cl ratio,while the sugar/nicotine ratio increased significantly.2)The total content of volatile aroma components in post-fermentation samples increased significantly to 498.09 μg/g,representing a 53.66%increase,primarily due to alcohols,ketones,hydrocarbons,organic acids,furans,and phenols.The OPLS-DA model demonstrated excellent reproducibility and no overfitting,as confirmed by cross-validation,identifying 32 components with significant content differences that effectively distinguished pre-and post-fermentation aroma profiles.3)Twelve volatile aroma components in post-fermentation samples showed higher ROAV values than pre-fermentation samples,with 11 components(including benzyl alcohol,phenylethyl alcohol,damascenone,β-ionone,acetophenone,and dihydroactinidiolide)having ROAV>1,indicating their role as key aroma components.[Conclusion]Treatment of upper low-grade flue-cured tobacco leaves with bacterial-enzyme synergistic fermentation significantly improves cigarette sensory quality.

Abstract:[Objective]To investigate the structure-activity relationship between the antioxidant activities of EGCG/theaflavin and their molecular structures.[Methods]The molecular structures and corresponding free radicals of the main functional components—epigallocatechin gallate(EGCG)and theaflavin—in green/black tea were theoretically calculated using the density functional theory(DFT)method.The differences in antioxidant activity and solvation effects between EGCG and theaflavin were analyzed based on multiple antioxidant indices.[Results]Theaflavin exhibited higher antioxidant activity than EGCG,with a frontier molecular orbital energy gap ΔE(LUMO-HOMO)of 5.67 eV,a bond dissociation energy(BDE)of the C7′—OH phenolic hydroxyl of 321.9 kJ/mol,an ionization potential(IP)of 461.4 kJ/mol,and a spin population of the Cb—OH oxygen atom of 0.218.In non-polar solvents,sequential proton-loss electron transfer(SPLET)is preferred as the dominant reaction mechanism,while in polar solvents,single electron transfer followed by proton transfer(SET-PT)is preferred.The C5′—OH of the B ring may be the active site of EGCG,while the C7′—OH of the A′ ring may be that of theaflavin.[Conclusion]Theaflavin exhibits stronger antioxidant activity than EGCG,with the position of phenolic hydroxyl groups significantly influencing its activity.The DFT method offers a novel perspective for investigating the antioxidant activity of functional components in tea.

Abstract:γ-glutamyl transpeptidase(GGT,EC 2.3.2.2)is a pivotal enzyme that catalyzes γ-glutamyl group transfer and hydrolysis reactions,playing a critical role in bioactive substance synthesis and food flavor modulation.Against the backdrop of national salt reduction policies,GGT enhances the bioavailability of natural umami compounds,offering innovative solutions for"salt reduction without compromising flavor"in the food industry.This review systematically examines GGT's sources,catalytic mechanisms,preparation methods,enzymatic characteristics,molecular modification strategies,and immobilization techniques,along with its current applications in food processing.GGT exhibits broad distribution across animal,plant,and microbial sources.Its catalytic mechanism adheres to the"ping-pong"model,generating γ-glutamyl peptides via acylation-deacylation reactions that synergistically enhance saltiness perception and umami intensity.Molecular modification and immobilization techniques significantly improve GGT's catalytic efficiency,stability(thermal and pH stability),and recyclability.In food processing,GGT has been successfully applied in soy sauce umami enhancement,flavor compound synthesis,and low-salt meat product flavor optimization.However,large-scale implementation faces challenges including low microbial enzyme production yields and high immobilization carrier costs.Future studies should focus on:Exploring GGT's application potential,engineering high-yield microbial strains and developing efficient immobilized catalysts,and establishing metabolomics-based flavor modulation models to fully realize GGT's potential in sustainable food processing and quality enhancement.