Abstract:Carbohydrates exist widely in nature, mainly from plants, animals, microorganisms. Carbohydrates are generally divided into four groups:monosaccharides, disaccharides, oligosaccharides and polysaccharides. Carbohydrate is one of the three essential nutrients of human body, and the basic physiological function is to provide energy for the life activities of human body. However, with the rapid development of global social economy in recent years, people's health awareness has gradually increased, which makes everyone have a new demand for carbohydrate intake, and carbohydrates with various functions have become a hot spot for people to study. Meanwhile, more and more functional carbohydrates are being discovered and used in food. Functional carbohydrates mainly include dietary fiber, resistant starch, resistant dextrin, active polysaccharide, functional oligosaccharides, sugar alcohols and other sugar substitutes. They have a variety of physiological functions closely related to human health, and play an important role in providing energy, constituting body components, regulating protein metabolism, anti-ketogenesis, protecting the liver and regulating intestinal flora. The common physiological functions of carbohydrates and the research progress of common functional carbohydrates were reviewed. The development trend of functional carbohydrates in the future was prospected. This paper aimed to enrich people's scientific understanding of functional carbohydrates and provide theoretical reference for further research on functional carbohydrates and related food development.

Abstract:Isomaltolose, also known as palatinose, is a reductive disaccharide formed by the α-1,6 glycosidic linkage of one glucose molecule and one fructose molecule. Isomalt (palatinit) can be obtained by hydrogenating and reducing isomaltulose and is an emerging functional edible sugar alcohol. Isomalt consists of two stereoisomers, α-D-pyranose glucose-(1,6)-D-sorbitol (GPS), and α-D-pyranose glucose-(1,1)-D-mannitol dihydrate (GPM), forming a white crystalline mixture. Depending on the ratio of GPS to GPM, isomalt can be classified into four primary products:ISOMALT ST, ISOMALT GS, ISOMALT DC, and ISOMALT LM. Isomalt is the only disaccharide sugar alcohol entirely derived from sucrose, with a taste profile resembling sucrose. It exhibits approximately 45% of the sweetness of sucrose and provides 50% of its calorific value. Notably, isomalt offers advantages such as chemical stability, non-cariogenic properties, and minimal impact on blood glucose and insulin levels after consumption, making it a viable and healthy alternative to sucrose. The physiological functions, industrial manufacturing, and current applications of isomalt were reviewed. The production processes (biocatalysis and hydrogenation technology) of isomalt were systematically introduced. The research progress on the key enzyme sucrose isomerase, involved in isomalt biosynthesis, including its structure, catalytic mechanism, and molecular modification were elaborated, providing valuable guidance for further research and industrial-scale production in this field.

Abstract:D-Tagatose is an important rare ketohexose. Its sweetness is 92% of sucrose, and its calories are only one third of sucrose. D-Tagatose was approved as a new raw material for safe food by the America's Food and Drug Administration and China's Health and Family Planning Commission in 2001 and 2014, respectively. D-Tagatose has the functions of lowering blood sugar, reducing obesity, improving gut microbiota, anti-caries, anti-oxidation and so on. D-tagatose, as an ideal functional sweetener, has extensive application value. However, the production cost and yield of D-tagatose have always been an important reason limiting the development and application of D-tagatose. The methods for D-tagatose synthesis mainly include chemical route and biological conversion. Although it is cost-effective to produce D-tagatose by chemical approach, it requires high temperature and pressure in the production process, and is easy to generate miscellaneous sugars such as sorbose and mannose, which is not conducive to separation and purification. In order to overcome these shortcomings, the biological conversion of D-tagatose has received extensive attention. Therefore, the research progress, advantages and disadvantages of D-tagatose biosynthesis from different substrates such as hexoses (galactitol, D-galactose and D-fructose), lactose, polysaccharide (maltodextrin and starch) were systematically reviewed, and the research trends in the future were also prospected, which provided reference for the research and production of D-tagatose.

Abstract:Galactooligosaccharides are important prebiotics. β-Galactosidases from Bacillales sp. can catalyze the transfer of galactoside, which can be used for the synthesis of galactooligosaccharides. The expression, enzymatic properties and application in the synthesis of galactooligosaccharides of a novel β-galactosidase from Bacillales sp. were investigated. A glycoside hydrolase (GH) family 35 β-galactosidase gene (BABgal35A) from Bacillales sp. was cloned and expressed in E. coli BL21(DE3). The results of multiple sequence alignment showed that BABgal35A shared the highest identity of 79.9% with a β-galactosidase from Bacillus circulans, and was a novel β-galactosidase (named BABgal35A). Crude enzyme was purified through Ni-IDA affinity chromatography to obtain electrophpresis-grade pure enzyme. SDS-PAGE showed that the molecular weight of purified enzyme was about 60kDa. The optimal pH and temperature of BABgal35A were determined to be 5.0 and 55℃, respectively. The enzyme was stable at pH 4.5-8.0 and temperature 20-45℃. BABgal35A exhibited the highest specific activity towards oNP-β-galactopyranoside. A maximum yield of 34% for galactooligosaccharides production was obtained by BABgal35A using lactose as substrate. The study showed that a GH family 35 β-galactosidase from Bacillales sp. was potentially suitable for the preparation of galactooligosaccharides.

Abstract:Hierarchical porous zeolitic imidazolate framework-8 (ZIF-8) materials have larger pore sizes compared with conventional ZIF-8 materials, and show better application prospects in the field of immobilized enzymes. At present, the effect of immobilizing Rhizopus oryzae lipase (ROL) using hierarchical porous ZIF-8 material remains unclear. In this study, an amorphous zeolitic imidazolate framework-8 (aZIF-8) material was prepared by adjusting the initial molar ratio of the precursor of ZIF-8 material, and the immobilized lipase ROL@ZIF-8 and ROL@aZIF-8 were prepared by in situ self-encapsulation based on the ZIF-8 and aZIF-8 materials, respectively. The morphological and structural differences of ZIF-8, aZIF-8, ROL@ZIF-8 and ROL@aZIF-8 were investigated by using infrared spectroscopy, X-ray diffractometer and scanning electron microscope, etc. The enzyme activities of ROL@aZIF-8 prepared under different ROL mass concentrations were compared with those of the same mass concentration of ROL. The acid-alkali stability, temperature tolerance, storage stability, and hydrolysis ability of ROL and ROL@aZIF-8 against dibutyl phthalate (DBP) and diisobutyl phthalate (DIBP) were investigated. The results showed that the aZIF-8 material presented an amorphous morphology containing various forms such as cruciate flower-like, square, and spherical, and was a hierarchical porous material with micropores and mesopores. ROL@aZIF-8 prepared at ROL mass concentration of 4mg/mL showed the maximum enzyme activity of 5.69U/mg. The hydrophobicity and hierarchical porous properties of the aZIF-8 material contributed to the higher enzyme activity of ROL@aZIF-8 than that of ROL at the same mass concentration of ROL. ROL@aZIF-8 showed better alkali stability, temperature tolerance, storage stability, and higher hydrolytic capacity for DBP and DIBP than ROL.

Abstract:Yak milk has nutritional properties of high protein and high fat content, and has good functional activities, such as anti-fatigue. However, due to the low production of yak milk and the scattered production area, there was limited research on the development of cheese products and other deep processing aspects. Penicillium roqueforti (P.roqueforti) was used as a secondary starter to develop blue style-yak milk cheese, and its ripening characteristics and flavor characteristics were analyzed. Results showed that P. roqueforti could grow rapidly in yak milk cheese, promoted the degradation of proteins, and formed a large number of peptides, amino acids, etc. The content of free amino acids, especially unami amino acids, was significantly increased at the end of yak milk cheese maturity (P＜0.05). SPME-GC/MS analysis showed that a total of 53 flavor components were detected in yak milk cheese. OPLS-DA analysis revealed that compared with the early stage of ripening, the composition of flavor components in yak milk cheese at the end of ripening was significantly different, and the total content was significantly increased (P＜0.05). The volatile aliphatic esters in yak milk cheese were mainly methyl esters, and the content was relatively stable in end stage (25d, 46d) of ripening. The content of volatile fatty acid was highest in the middle stage of ripening, but significantly decreased at the end of ripening (P＜0.05). The concentration of volatile aliphatic ketones, especially methyl ketones, increased significantly in the end ripening stages (P＜0.05). 2-Nonanone, 2-heptane, methyl octanoate, 2-pentanone, ethyl caprate, methyl caprate, caproic acid, 2-octanone, butyric acid and other volatile compounds were quantitatively dominant flavor components of blue style-yak milk cheese. The study showed that P. roqueforti could promote the ripening of yak milk cheese, which could significantly affect the nutrition and flavor characteristics of yak milk cheese. The research aimed to lay a theoretical foundation for the deep processing of characteristic dairy products such as yak milk in China, and provide reference for promoting the development of China's characteristic dairy deep processing industry.

Abstract:To evaluate the effect of degradation on the structure and properties of sea buckthorn polysaccharides (SBP), the H₂O₂ combined with Fe²⁺ method was used to degrade SBP. The effects of degradation on the molecular weight, monosaccharide composition, particle size, structural characteristics and antioxidant capacity of sea buckthorn degraded polysaccharides (SBDP) were investigated. The results showed that, the molecular weight of SBDP (2.902×10⁴Da) was significantly lower than that of SBP (3.016×10⁵Da). Ion chromatography analysis proved that both SBDP and SBP were composed of the same monosaccharides (fucose, rhamnose, arabinose, galactose, glucose, mannose and galacturonic acid) in different molar ratios. SBDP showed similar structural characteristics to SBP as confirmed by FTIR and NMR spectroscopy. The solubility of SBDP was increased by 20.72%, and SBDP had better hygroscopicity and moisture retention. SBDP had lower apparent viscosity (5.0mg·mL-1) and shear thinning behavior. SBDP exhibited higher antioxidant activity, with the DPPH radical, ABTS⁺ radical and hydroxyl radical scavenging rates of 89.44%±0.12%, 96.09%±0.22% and 73.26%±1.16%, respectively. The H₂O₂ combined with Fe²⁺ treatment significantly reduced the molecular weight of SBP and enhanced its functional properties and antioxidant activity. This research aimed to expand the application of SBP in food applications.

Abstract:Segment drying is the major physiological disorder that deteriorates fruit quality and results in loss of flavor and edible value of fruits, including mainly granulation-type segment drying and collapse-type segment drying. Few research had been focused on the latter. Using Tarocco blood orange upon collapse-type segment drying as study material, widely targeted metabolomics was used to analysis primary metabolite and metabolic pathway changes of collapse-type segment drying, amino acid content analysis, enzyme activity assay, and gene expression analysis were utilized to elucidate the mechanism underlying the rapid deterioration of citric acid during segment drying. The results showed that a total of 193 differentially primary metabolites were identified in juice vesicles upon segment drying, citric acid content significantly decreased by 53.1%, the metabolites relative to the acetyl-CoA synthesis pathway (such as serine, linoleic acid and other lipids) increased significantly, the gene expression of lipid metabolism was up-regulated upon segment drying, while the expression of gene CsACLs encoding ATP-citrate lyase remained unchanged. Glutamine synthetase activity increased by 75.3% in vesicles upon segment drying. γ-Aminobutyric acid content remained unchanged, glutamine decarboxylase activity was not changed, the expression of gene CsGADs encoding glutamine decarboxylase was down-regulated upon segment drying. In conclusion, the acetyl coenzyme A synthesis pathway was the main pathway for the rapid degradation of citric acid in vesicles of blood orange during collapse-type segment drying. The results aimed to provide a reference for clarifying the mechanism of collapse-type segment drying in citrus fruit.

Abstract:To elucidate the key antibiofilm components of Zanthoxylum armatum DC. essential oil (ZAEO) against Bacillus amyloliquefaciens and their associated intracellular mode of action, the PharmMapper server was used to screen potential targets and these predicated targets were then refined by genome annotation information, to predict and select the key active components of ZAEO and action targets involved in antibiofilm. The interaction network between ZAEO's active components and potential targets was constructed by using Cytoscape software. The GO function and KEGG pathway enrichment analysis were further performed using the String database. The core targets were obtained through potential target interactions analysis by STITCH database and performed network topology was analysed by Cytoscape software. Additionally, the CB-DOCK2 web server was used to carry out the molecular docking between the active components and the core targets. Finally, the in vitro antibiofilm activity of key components of ZAEO was assessed through culture experiments involving crystal violet staining and bacterial motility test. The results showed that a total of 21 active ZAEO components, 133 potential targets and 8 core targets were obtained by network pharmacology analysis. GO enrichment analysis yielded a total of 17 subcategories, including 6 subcategories related to biological processes, 8 subcategories related to molecular functions, and 3 subcateories related to cellular components. KEGG pathway enrichment analysis revealed 8 signaling pathways, including secondary metabolite biosynthesis, amino acid biosynthesis and other pathways. Molecular docking analysis demonstrated that three key active components, namely uncineol, farnesol acetate and trans-farnesol, exhibited strong binding affinity to the core target OdhA, CarB and PurF through intermolecular forces such as hydrogen bonds and hydrophobic interactions, forming stable complex conformation. Furthermore, the in vitro biofilm culture verification experiment confirmed that the range of 0.32 to 1.28μL/mL of farnesol acetate and trans-farnesol displayed significant antibiofilm effects against Bacillus amyloliquefaciens. These results aimed to provide new technical routes for the intracellular molecular mechanism of the antibiofilm of ZAEO.

Abstract:Moringa oleifera seed antimicrobial peptides MOp2 and MOp3 had good antibacterial effects on Staphylococcus aureus (S. aureus), but their effects on biofilm were still unclear. Therefore, crystal violet semi-quantitative method, fluorescence microscopy, enzymatic digestion experiment and molecular docking technology were used to study the effects of the newly identified antimicrobial peptides MOp2 and MOp3, which were isolated from hydrolysates of Moringa oleifera seeds proteins, on S. aureus biofilm. The results showed that the minimum biofilm inhibitory concentration (MBIC) and minimum biofilm eradication concentration of MOp2 and MOp3 were both 4mg/mL and 8mg/mL, respectively. At 1×MBIC concentration, both MOp2 and MOp3 exhibited biofilm clearance rates of 63.28% and 67.90%, respectively. It was found by fluorescence microscopy that after treatment with MOp2 and MOp3, biofilm adhesion decreased and bacteria numbers reduced. The initial bacterial adhesion rates decreased by 44.19% and 50.77% after treatment with 1×MBIC of MOp2 and MOp3, respectively, and the surface hydrophobicity also decreased. Enzymatic digestion experiments showed that the extracellular proteins (mass fraction 49.01%) were the most abundant component in S. aureus biofilm extracellular polymeric substances, followed by extracellular polysaccharides and extracellular DNA. MOp2 and MOp3 could inhibit the secretion and synthesis of the three components in extracellular polymeric substances. The results of molecular docking showed that MOp2 and MOp3 could both bind to key biofilm formation proteins AgrA, CshA, LuxS and SarA in S. aureus, which might have certain effects on the quorum sensing system of S. aureus and thus inhibit biofilm formation. The study aimed to provide a theoretical basis for the application of Moringa oleifera seed antimicrobial peptides in preservation of food industry.

Abstract:As a common food constituent, fat could interact with cow's milk allergens, and thereby affecting the extraction effect and detection accuracy of allergens. However, research on degreasing methods for high-fat complex food matrices was rarely reported. Chocolates containing cow's milk allergens were used to simulate the high-fat complex matrix and degreased by n-hexane, isopropanol, ethyl acetate and lipase. The degreasing rate and protein loss rate of simulated matrix were determined. The changes of protein structure, particle size, fat distribution and microstructure were compared, and the concentration of major milk allergens extracted from simulated matrix were determined by indirect ELISA before and after degreasing. The results showed that the sample treated with n-hexane had the highest degreasing rate (87.87%), and the lowest protein loss rate (6.86%). Degreasing would change the spatial structure of proteins, with the overall structure changing from compact to loose, and there was no obvious changes in protein in the n-hexane and ethyl acetate treatment groups. The particle size of protein decreased slightly after degreasing, but the isopropanol treatment caused the protein to aggregate into larger particles, and the particle size increased from 297.9nm to 445.1nm. After degreasing by n-hexane and ethyl acetate, the fat distribution in simulated matrix was more uniform and the fat droplets became smaller. The microstructure of the simulated matrix changed from a dense and smooth clump to an incompact and porous structure, while the isopropanol and lipase groups still showed partial agglomeration. The indirect ELISA results showed that the extraction rate of casein in the ethyl acetate group increased by 61.02%, and the concentrations of α-lactalbumin and β-lactoglobulin were the highest in the n-hexane group, which were 0.73mg/mL and 1.89mg/mL, respectively. n-Hexane degreasing treatments could significantly improve the extraction effect of cow's milk allergens in high-fat complex matrix, hoping that the results could provide reference for the accurate detection of allergens in high-fat complex matrix foods.

Abstract:In order to solve the loss of activity of probiotics in the process of storage and feeding, as well as the competition and antagonism that may occur when two or more probiotics are mixed, and to better exert the step-by-step release and synergistic effect of two or more bacteria, Bifidobacterium adolescentis FS2-3 as the inner core microsphere and Bacillus subtilis SN15-2 as the shell microsphere were used to separate and embe the two probiotics. Sodium alginate was used as wall material and sodium mercapto carboxymethyl cellulose (CMC-SH) was added to enhance the adhesion of probiotics in intestinal tract. Probiotics double bacteria multi-core microcapsules were prepared by endogenous emulsification and extrusion. The microcapsule embedding rate was used as the evaluation index, and the optimal conditions for the preparation of probiotic double bacteria microcapsules were determined by single factor and response surface experiments. The results showed that when the concentration of sodium alginate in the inner core was 1.82%, the concentration of CMC-SH in the bacterial solution was 0.9%, the volume ratio of water to oil was 1.0∶2.9, and the concentration of sodium alginate in the outer layer was 2.9%, the embedding rate of probiotics double bacteria microcapsules could reach 72.93%. The probiotic double bacteria microcapsules under this process condition had good acid resistance and intestinal solubility. In the artificial intestinal fluid, the release rate of microcapsules reached 86.3% at 180min, which was basically completely disintegrated, and the ideal effect was achieved. The results of this study provided a reference for solving the technical problems of activity maintenance and synergism of mixed probiotic microecologics in China.

Abstract:Flaxseed oil is rich in α-linolenic acid, and its price is 3 to 20 times higher than that of other edible oils, and it is very vulnerable to be adulterated and counterfeited. The authenticity discrimination model of flaxseed oil based on fatty acid (FAs) fingerprints was established. Eight kinds of edible oil samples (flaxseed oil, rapeseed oil, sunflower oil, soybean oil, peanut oil, corn oil, sesame oil, blended oil), two kinds of waste oil samples (kitchen waste oil and gutter oil) were collected, and 12 FAs were determined by gas chromatography. Principal component analysis (PCA) was conducted to observe the clustering properties of these 10 kinds of oils according to their FAs fingerprint. Orthogonal partial least squares discriminant analysis (OPLS-DA) was applied to evaluate the feasibility of FAs fingerprint on authenticity of species origin, processing methods (cold or hot pressing) and grade of flaxseed oil, and partial least squares (PLS) quantitative prediction model was established to estimate the adulteration dosage of rapeseed oil in flaxseed oil. The FAs fingerprint of flaxseed oil was extremely different from other oils. Content of C18:3ω3[(50.14±9.68)g/100g] was significantly higher than that of other oils, while content of C18:1ω9[(16.62±5.02) g/100g] and C18:2ω6[(14.62±4.64)g/100g] were significantly lower than that of other oils. PCA and OPLS-DA both could distinguish species origin, processing methods and grade of flaxseed oil. OPLS-DA had better discrimination formance. PCA and OPLS-DA showed that flaxseed oil was the closest cluster to rapeseed and soybean oil. Accuracy of OPLS-DA for flaxseed oil species discrimination was 100%, accuracy of cold and hot pressing discrimination was 96.7%, and accuracy of grade discrimination was 90.0%. The key FAs for discrimination of flaxseed oil species, processing methods and grade were C18:3ω3, C18:1ω9 and C18:2ω6. Correlation analysis of five key FAs contents in flaxseed oil and adulteration dosage of rapeseed oil showed that C18:3ω3 content was negatively correlated with rapeseed oil adulteration dosage, C18:1ω9 and C18:2ω6 content were positively correlated with rapeseed oil adulteration dosage. R² of PLS quantitative discrimination model for flaxseed oil adulterated with rapeseed oil was 0.986, RMSEE was 4.2635, while RMSEcv was 4.2648, and the prediction error of adulteration dosage was no more than 10%. The results showed that it was feasible to establish the authenticity discrimination model of flaxseed oil by FAs fingerprint, and there was optimization space of this mold.

Abstract:In order to screen japonica rice varieties suitable for processing fresh instant rice and establish a simple and practicable method for evaluating the adaptability of raw materials, a total of 30 japonica rice varieties from northeast China were selected as the test samples, followed by the production of fresh instant rice. The effect of appearance, main components, pasting and cooking properties of japonica rice on eating quality of fresh instant rice were investigated by descriptive and correlation analysis. The results showed that there were differences in 22 evaluation indicators among different japonica rice varieties. Six indicators with variable coefficients exceeding 10%, in descending order were iodine color value, dry matter of rice soup, breakdown value, holding strength, length-width ratio and b*. This indicated that the six indicators were more representative. Correlation analysis showed that the length-width ratio was significantly positively correlated with adhesiveness, chewiness, and cohesiveness (P<0.05), and the breakdown value was significantly negatively correlated with cohesiveness, adhesiveness, and chewiness (P<0.05). The iodine blue value and dry matter of rice soup were extremely significantly positively correlated with elasticity and stickiness (P<0.01).Two representative quality indexes of fresh instant rice were iodine color value and breakdown value selected by factor analysis and stepwise regression analysis. And the comprehensive quality evaluation model of fresh instant rice was obtained.The fitting degree between the comprehensive scores of the model and the sensory scores was 0.7064, indicating that the model could accurately evaluate the eating quality of fresh instant rice. And 11 kinds of japonica rice were suitable for processing fresh instant rice by cluster analysis. This study aimed to provide a scientific basis for effectively selection of raw materials for the production of fresh instant rice.

Abstract:In order to solve the problems of high cost of model maintenance, insufficient model scalability and poor sharing of spectral resources in spectral detection technology, and to improve the limitations of detection and analysis objects of dedicated portable spectrometers, a real-time online spectral detection system consisting of portable spectrometers, mobile terminals and cloud servers was developed using Android development tools and Java language by decoupling the spectral data collection and analysis functions. Based on cloud computing services, the establishment and analysis of cloud spectral models were completed. Taking the quantitative analysis of wheat flour gluten as an example, the quantitative analysis model of wheat flour gluten was established by using multiple scattering correction, competitive adaptive reweighted sampling method, and partial least squares regression algorithm. 25 wheat flour samples were tested and the analysis results were returned to verify the reliability of the system. The results showed that the error range of the gluten content of 25 wheat flour samples was 0-0.7%, and the average analysis time was 7.09s. The error range of gluten content and the time consumption of analysis results were both within the acceptable range, which verified that it was feasible to realize real-time online detection and analysis of spectra based on cloud computing services. By deploying quantitative analysis models of the main components of different foods to the cloud, the system could realize real-time online detection and analysis of various food qualities, hoping to provide technical support for rapid and non-destructive testing of food quality in multiple scenarios.