Table of Content

25 October 2023, Volume 44 Issue 20
Food Chemistry
Effect of Toughening Treatment on the Structural and Physicochemical Properties of Potato Starch and the 3D Printing Performance of Potato Starch Gel
MA Shu, GUO Shuangfeng, LIN Qian, JIANG Hao
2023, 44(20):  1-7.  doi:10.7506/spkx1002-6630-20221114-165
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In this study, we investigated the effect of toughening treatment (55 ℃ for 0, 12, 24, 36, 48 and 60 h) on the microstructure, pasting properties, thermal properties, rheological properties and 3D printability of potato starch. The results showed that the toughening treatment roughened the surface of starch granules and increased the viscosity and pasting temperature of the starch. The toughened potato starch gel showed greater mechanical strength and a more stable and ordered internal structure than the native starch gel. It was found that toughening treatment for 36 h had a significant effect on the printing characteristics of potato starch gels, resulting in the highest printing accuracy and height as well as the best printing performance.
Effect of Degree of Polymerization of Amylose on in Vitro First-Order Digestion Kinetics of Ternary Complexes of Seedless Breadfruit Starch, Lauric Acid and β-Lactoglobulin
LI Bo, ZHANG Yanjun, ZHAO Yuan, HUANG Chongxing
2023, 44(20):  8-19.  doi:10.7506/spkx1002-6630-20221114-155
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Objective: This study aimed to investigate the influence of degree of polymerization of amylose on the digestibility characteristics of its ternary complexes. Methods: Ternary complexes of seedless breadfruit starch, prepared by separately mixing amyloses extracted from five cultivars (GJS, FSS, SMS, SS and CS) with amylopectin extracted from GJS, having the highest degree of polymerization among amylopectins from these cultviars, at a 1:1 ratio were prepared with lauric acid (LA) and β-lactoglobulin (β-LG) and characterized for supramolecular structure and digestion kinetics by high-performance size-exclusion chromatography (HPSEC), X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), atomic force microscopy (AFM), and Fourier transform infrared (FTIR) spectroscopy. All five complex samples displayed obvious characteristic peaks of ternary complexes, V-type crystalline structure and rodlike molecular configuration. As the degree of polymerization of amylose increased, the complexing index (CI) (from 68.81% to 83.55%), relative crystallinity (from 21.10% to 28.35%), short-range order (from 0.44 to 0.63), molecular mass (from 2.90 × 106 to 8.02 × 106 Da), molecular density index (from 3.50 to 23.07 g/(mol·nm3), gelation temperature (from 98.52 to 103.71 ℃), and gelation enthalpy (from 13.95 to 18.73 J/g), second-order kinetic rate constant (from 1.00 × 10-2 to 2.92 × 10-2 min-1) increased, while the semicrystalline lamellae thickness (from 3.20 to 4.82 nm), mass fractal dimension (from 1.28 to 1.81), characteristic length of crystallite unit (from 6.33 to 7.01 Å), radius of gyration (from 70.31 to 93.94 nm), and nanosurface “blocklet” size (from 7.05 to 15.03 nm) dropped, which led to a decrease of in vitro glycemic index (from 78.83 to 85.71). Statistical analysis showed that the degree of polymerization of amylose could remarkably affect the multiscale superstructure of the ternary complexes, which in turn could change its digestion kinetics. The results provide new theoretical guidance for the production of starch-based multicomponent foods.
Structural Modification and Solubility Enhancement of Glutenin by pH-Shifting
RONG Yujuan, HOU Yuwei, CAO Xiaoqian, ZHANG Jiajia, ZHOU Bin
2023, 44(20):  20-27.  doi:10.7506/spkx1002-6630-20230209-088
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Glutenin (Glu) was modified by pH-shifting to improve its properties. The effect of pH-shifting treatment on the structure and micromorphology of glutenin was investigated by dynamic light scattering (DLS), transmission electron microscopy (TEM), fluorescence spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. The results showed that pH-shifting could significantly reduce the particle size of Glu aggregates and increase the surface charge of Glu granules. Meanwhile, it increased the hydrophobicity and sulfhydryl group content, and decreased the disulfide bond content, and the effect of alkaline pH-shifting was more significant than that of acidic pH-shifting. In addition, alkaline pH-shifting significantly improved the solubility of Glu, which could play an active role in broadening the application range of Glu in the food industry.
Mechanism of Action of Quercetin-3-O-glucoside against the Non-enzymatic Glycosylation of α-Lactalbumin
ZHANG Lu, XU Linju, PENG Chunyan, WANG Peixin, XIE Zuohua, XIE Xing, JIA Xiaoyan, TU Zongcai
2023, 44(20):  28-34.  doi:10.7506/spkx1002-6630-20221004-027
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In this study, the effect of quercetin-3-O-β-D-glucuronide (Q3G) on the formation of fructosamine and 5-hydroxymethylfurfural (5-HMF), the amount of free amino groups and browning degree in a non-enzymatic glycosylation model consisting of bovine α-lactalbumin (α-La) and fructose were evaluated. In addition, the inhibitory mechanism of Q3G against non-enzymatic glycosylation was explored by molecular docking and mass spectrometry (MS). The results indicated that Q3G could significantly reduce the browning degree, increase the free amino groups, inhibit the formation of fructosamine and 5-HMF, and delay the process of glycosylation reaction. The effect was most pronounced at 2 mmol/L Q3G. Molecular docking analysis indicated that Q3G could bind with the active amino acid residues of α-La through hydrogen bonds, van der Waals force and hydrophobic interactions, delaying the process of glycosylation reaction. Meanwhile, by ultra-high performance liquid chromatography-quadrupole-orbitrap tandem mass spectrometry (UPLC-Q-Orbitrap MS/MS) analysis, it was found that Q3G shielded the potential glycosylation sites Lys93 and Lys108, and the activity of the glycosylation site Lys98 was weak, indicating inhibited non-enzymatic glycosylation reaction. This study can provide a theoretical basis for the development of Q3G as a potential anti-glycosylation agent.
Effects of Different Treatment Methods on the Structure and Properties of High Internal Phase Emulsion Stabilized by Chitosan/Arabic Gum Composite Particles
XU Tianlin, HAN Jing, CHEN Fenglian, DOU Xinlai, GAO Chengcheng, TANG Xiaozhi
2023, 44(20):  35-42.  doi:10.7506/spkx1002-6630-20221110-106
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This study was executed in order to further improve the emulsion stability of chitosan/gum arabic composite particles and to regulate the rheological properties of high internal phase emulsions stabilized by it. Chitosan/gum arabic composite particles were prepared by different treatments and were used to stabilize high internal phase emulsions. The effects of the structure and properties of the particles on the structure, rheological properties and stability of high internal phase emulsions were explored. The results showed that compared with the control group (pH 5.0), ultrasonic and heat treatments significantly increased the yield of composite particles. There was no significant difference in the particle size or stability of the high internal phase emulsions stabilized by the treated and control composite particles, while the oil binding capacity and viscoelasticity were significantly improved. pH increase to 7.0 and sodium tripolyphosphate crosslinking had a negative effect on the yield of particles, making the composite particles exhibit poor emulsion stability and oil binding ability. The above findings showed that ultrasonic and heat treatments could improve the stability and adjust the rheological properties of chitosan/gum arabic composite particle-stabilized high internal phase emulsion, which shows potential in food texture regulation and fat substitutes with different textures.
Effects of Combined Addition of Modified Starch and Non-Muscle Protein on Gel Properties and Protein Conformation of Squid Surimi Products
ZHANG Xiaohui, GUO Quanyou, ZHENG Yao, BAO Hairong, WEI Banghong, ZHUANG Xiaomei, YANG Xu
2023, 44(20):  43-52.  doi:10.7506/spkx1002-6630-20221219-194
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To improve the gel properties of squid surimi products, we optimized the addition of modified corn starch acetylated distarch phosphate (ADSP) and the non-muscle proteins egg white protein (EWP) and soy protein isolate (SPI), and we evaluated the effects of the addition of ADSP, EWP and SPI on the texture, intermolecular force, protein secondary structure and microstructure of squid surimi products. Furthermore, we explored the mechanism by which modified starch and non-muscle protein improve the gel quality of squid surimi products. The results showed that the gel properties of squid surimi products with 10% ADSP, 7% EWP and 6% SPI were the best. Compared with the control group, the addition of modified starch or non-muscle protein decrease the relative contents of random coil and α-helix in proteins, and increased the contents of β-sheet and β-turn. Their combined addition was beneficial for the retention of β-sheet and β-turn structures during the gelation process, and promoted the hydrophobic interaction between proteins, resulting in the formation of a denser gel network structure, which in turn improved the gel strength and water holding capacity of squid surimi products. Correlation analysis showed that the gel strength and water holding capacity, hydrophobic interaction, and relative contents of β-turn and immobilized water of squid surimi products were significantly positively correlated with each other (P < 0.01), and significantly negatively correlated with the contents of free water and random coil (P < 0.01). Therefore, the addition of 10% ADSP, 7% EWP and 6% SPI improved the gel quality of squid surimi products by affecting protein secondary structure and water distribution.
Preparation of Whey Protein-Oligosaccharide Complex and Its Application as Fat Substitute in Processed Cheese
LI Qianwen, LIANG Ying, WANG Xiaonan, ZHANG Chuan, LIU Zhiqin, CHEN Shuxing, LÜ Mingqi
2023, 44(20):  53-61.  doi:10.7506/spkx1002-6630-20230109-055
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Glycosylated whey protein (GWP) was prepared from whey protein and xylooligosaccharide by wet glycosylation method. Its advantages for use as a fat substitute were analyzed, and the application of this fat substitute in reduced-fat processed cheese was explored. The results showed that the optimal preparation conditions were determined as: xylooligosaccharide concentration of 6%, reaction temperature of 85 ℃ and reaction time of 2 h. The grafting degree of GWP prepared using these conditions was (29.28 ± 1.53)%, and a browning phenomenon occurred during the preparation process. Compared with whey protein, the contents of α-helix, β-fold, β-turn and random coil structures changed in GWP, and the water and oil-holding properties increased by 60.18% and 103.97%, respectively; the emulsifying capacity and emulsion stability increased by 30.81% and 13.57%, respectively. The surface of GWP was smoother. The surface hydrophobicity at pH 7.0 was 2.48 times higher than that of whey protein. After shearing at 10 000 r/min for 10 minutes, the median particle diameter of GWP was 7.57 µm, and the stability of the solution was obviously improved, so that GWP could be used to simulate fat. The hardness of reduced-fat processed cheese with 60% butter replacement by GWP was significantly lower than that of full-fat processed cheese (P < 0.05), and the meltability increased significantly (P < 0.05), but the texture characteristics such as elasticity, chewiness and brightness value (L*) were not significantly different from those of full-fat processed cheese (P > 0.05), and the total sensory score was equivalent to that of full-fat processed cheese. These results proved that the glycosylated whey protein has a potential application as a fat substitute in reduced-fat food while guaranteeing that the quality of the product is good.
Interfacial Properties of Octenyl Succinic Anhydride-Starch Decorated Zein Particles and Stability of Pickering Emulsion Stabilized with It
LEI Dandan, WANG Limin, ZHANG Wen, ZHAO Pei, QIAN Xiaoqing, QU Ao, WU Zijian
2023, 44(20):  62-70.  doi:10.7506/spkx1002-6630-20230421-209
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In order to improve the ability of solid zein particles to stabilize Pickering emulsions, octenyl succinic anhydride (OSA)-modified starch was used to modify zein. Zein-OSA starch composite particles were prepared by solvent-antisolvent precipitation method. The interaction between zein and OSA starch and the size and structure of the composite particles were studied, and the effects of the mass ratio of zein to OSA starch on the particle size distribution, storage stability, pH stability and rheological properties of Pickering emulsion stabilized with the composite particles were explored. The results showed that OSA starch could modify zein through non-covalent interactions including electrostatic interaction, hydrogen bonding and hydrophobic interaction, changing the secondary structure of zein and improving its hydrophilicity. The composite particles with zein to OSA starch ratio of 1:3 had the smallest average particle size (163.3 nm) and PDI (0.177), and its contact angle was 87.4°, which indicated that the particles had nearly neutral wettability and were more suitable for stabilizing Pickering emulsions. Meanwhile, Pickering emulsions stabilized by the composite particles had the smallest particle size distribution and the highest storage modulus, loss modulus and apparent viscosity, indicating that OSA starch modification could regulate the interfacial properties of zein composite particles and consequently of Pickering emulsions. The above studies show that the interfacial modification of zein can improve the stability of its solid particles and consequently of Pickering emulsions. This study provides theoretical support for further expanding the comprehensive utilization of zein in emulsion systems.
Preparation and Crosslinking Capacity of Dialdoxylose
JING Shutong, LI Zhengsheng’ao, LI Han, CAO Honghua, LI Xuecong, LIU Yonghao, YU Jiaqi, WEN Jingru, SUN Xun
2023, 44(20):  71-78.  doi:10.7506/spkx1002-6630-20221203-032
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Objective: To design and synthesize dialdoxylose, a glutaraldehyde analogue which is expected to have a low toxicity, and to characterize its performance in crosslinking chitosan in 1% acetic acid solution. Methods: Dialdoxylose was obtained by sodium periodate oxidation and deprotection of monoacetone glucose and used to form crosslinked chitosan gels. The gel strength, fluid properties, water activity and thermal stability of chitosan gels were analyzed by texture profile analysis (TPA), low field-nuclear magnetic resonance (NMR) spectroscopy and differential scanning calorimetry (DSC). Results: It was found that dialdoxylose exhibited two structures in water, (α,β) and (β,β), with a ratio of 44.4:65.6. The hardness, viscosity and water-holding capacity of the chitosan gel crosslinked with 0.002 g/mL dialdoxylose were highest. Conclusion: Dialdoxylose has an obvious crosslinking effect on chitosan, which is greatly affected by its concentration. The results of this study are of theoretical guiding significance for the development of new low-toxicity small-molecule crosslinking agents.
Multistep Molecular Distillation for the Preparation of Glyceride-Type Fish Oil High in Omega-3 Polyunsaturated Fatty Acid by Enzymatic Transesterification
SHEN Linjie, LIN Rongfa, ZHANG Lianyue, FENG Chuanzhi, FU Hong
2023, 44(20):  79-86.  doi:10.7506/spkx1002-6630-20230207-065
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The separation of glyceride fish oil high in omega-3 polyunsaturated fatty acid (ω-3 PUFA) produced by multistage enzymatic transesterification was studied by multistep molecular distillation. Firstly, glycerides and by-products in the transesterification products were separated by primary molecular distillation. When the distillation pressure was 5 Pa, the distillation temperature was 140 ℃, the scraper speed was 240 r/min, and the feeding rate was 0.2 mL/min, the yield of the first-stage heavy phase was 47.13% and the content of ω-3 PUFA in it was 53.76%. Meanwhile, high-temperature gas chromatography (HTGC) and nuclear magnetic resonance hydrogen (1H-NMR) spectroscopy consistently showed that the heavy phase did not contain fish oil ethyl ester. Secondly, the ω-3 PUFA content of the light phase increased from 60.73% to 78.01% by molecular distillation at a distillation pressure of 5 Pa, a distillation temperature of 110 ℃, a scraper speed of 240 r/min, and a condensation temperature of 20 ℃. After conducting secondary enzymatic transesterification reaction and molecular distillation separation on the enriched first-stage light phase, the yield of the second-stage heavy phase was 78.01% and its ω-3 PUFA content was 51.38%. When the enrichment step was omitted, the content of ω-3 PUFA in the second-stage heavy phase was only 42.37%. Multistep molecular distillation combined with multistage enzymatic transesterification can be used to prepare glyceride-type fish oil products with different ω-3 PUFA contents, with maximal utilization of raw materials and by-products.
Effect of Acetic Acid Pretreatment on Oil Content of Potato Chips
SHI Bingyan, DONG Nan, WANG Mei, LÜ Du, LOU Jiaqin, LIU Jia
2023, 44(20):  87-93.  doi:10.7506/spkx1002-6630-20230207-057
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In the present work, we applied acetic acid pretreatment (ACP) to reduce the oil absorption and improve the quality characteristics of potato chips (PC) and we explored the underlying mechanism. The variation of water distribution in fresh potato slices pretreated with acetic acid for 1–8 hours and the variations of the water and oil contents, oil composition and distribution, pore diameter, color and texture of PC made from the pretreated potato samples were studied. After ACP, both oil and water contents of PC were significantly decreased (P < 0.05). An ACP time of 4 h gave the lowest oil content of PC (17%). Microscopic observation of the cell structure of PC revealed that pectin gelation occurred between the cell walls, and the cell structure remained relatively intact with few empty spaces after ACP. Moreover, ACP significantly improved the sensory characteristics of PC, endowing it with a brighter color and better crispness. This study provides a new strategy for the production of low-fat potato chips.
Selenization Modification and Physicochemical and Structural Characterization of Polysaccharides from Perilla frutescens L. Leaves
ZHAO Yana, GUO Jiangtao, ZHOU Tiantian, LI Menghao, LI Huizhen
2023, 44(20):  94-99.  doi:10.7506/spkx1002-6630-20230206-048
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In this study, polysaccharides (PFPS) were extracted form Perilla frutescens L. and modified by HNO3-Na2SeO3 method, and the physicochemical and structural characteristics of PFPS and selenized PFPS (Se-PFPS) was analyzed by Fourier transform infrared (FTIR) spectroscopy, nanoparticle size analyzer, high performance gel permeation chromatography (HPGPC), scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermal gravimetric analyzer (TGA). The selenium content of Se-PFPS was (1 004.33 ± 48.60) μg/g as determined by atomic fluorescence spectrometry (AFS). The FTIR spectrum showed a characteristic absorption peak of Se‒O‒C at 620 cm-1, indicating that sodium selenite was chemically bound to PFPS and seleniumin in Se-PFPS existed in the form of selenite. HPGPC and particle size analysis showed that selenization modification reduced the particle size, and increased the molecular mass of PFPS. The results of SEM and XRD showed that selenization modification changed the morphology and crystalline state of PFPS, and Se-PFPS mainly existed in polycrystalline and amorphous forms. TGA analysis showed that PFPS had stronger thermal stability than did Se-PFPS.
Heterologous Expression and Physicochemical Properties of Plantaricin LPL-1
WANG Yu, WANG Yao, LI Pinglan
2023, 44(20):  100-106.  doi:10.7506/spkx1002-6630-20221130-354
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The present study aimed to express soluble recombinant class IIa bacteriocin in Escherichia coli. The plantaricin LPL-1 gene was cloned into an arabinose promoter, and the C-terminus was fused with the his-tag sequence for expression. The inhibitory activity of recombinant plantaricin LPL-1 against Listeria monocytogenes 54002 was used as the response variable. A novel cell factory, E. coil (ΔtrxB + Δgor + ahpCM), suitable for class IIa bacteriocin expression was established by CRISPR gene editing technology. It was derived from E. coil BW25331 by deleting the thioredoxin reductase (trxB) gene and glutathione reductase (gor) gene and mutating the gene encoding peroxidase (ahpC). The recombinant plantaricin LPL-1 was purified by affinity chromatography, and its physicochemical properties were analyzed. The purified plantaricin LPL-1 possessed wide pH stability (2–11), high thermal stability (60–100 ℃), and surfactant stability. The recombinant bacteriocin has wide potential for food industrial applications.
Analysis of Mixed-Species Biofilm Formation between Meat-Derived Escherichia coli and Pseudomonas
JI Junke, MI Xiaoyu, YUAN Yangyang, CHENG Yu, ZHANG Wendong, ZHANG Chen, JIANG Yun
2023, 44(20):  107-118.  doi:10.7506/spkx1002-6630-20221101-010
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This study aimed to explore mixed-species biofilm formation (BF) between meat-derived Escherichia coli and Pseudomonas. The biofilm-forming capacity of isolates was evaluated by means of microplate crystal violet staining and the process of mixed-species biofilm formation between representative strains was investigated. The dynamic changes of biofilm amount, microstructure and the composition of extracellular polymeric substances (EPS) were examined. Absolute quantitative real-time PCR was used to analyze the difference in the expression of BF-related genes. The results showed that there were significant inter-strain differences in the biofilm-forming capacity of E. coli and Pseudomonas (P < 0.05), in which the strains with strong biofilm-forming capacity accounted for 25.81% and 23.08%, respectively. The results of plate counting showed that the BF processes of E. coli D4-18 + Pseudomonas Y2-2 10, and E. coli C-13 + Pseudomonas Y2-1 1 were different on stainless steel sheet, and the interaction between the two species changed with BF time. Similar changes in the microstructure were observed by confocal laser scanning microscope (CLSM). The secretion of protein and polysaccharide in EPS was inhibited during mixed-species BF; the amount of protein decreased by 31% and 48%, respectively, and the amount of polysaccharide decreased by 38% and 56%, respectively, at 72 and 168 h of culture compared with the total EPS of the two single-species biofilms. The results of gene expression per unit cell number showed that the expression of BF-related genes was significantly up-regulated in the biofilm compared with the planktonic cells (P < 0.05). Compared with the single-species biofilm, the papC and csgA genes of E. coli in the mixed biofilm were significantly up-regulated at 72 and 168 h (P < 0.01), while the phoR and cbrA genes of Pseudomonas were significantly down-regulated at 72 h (P < 0.01). The absolute amount of genes expression per unit area in mixed-species BF changed compared with that in single-species BF. This study can provide a scientific basis for understanding the mixed-species BF of meat-derived spoilage microorganisms and for the risk assessment and control of microbial contamination in meat production and processing.
Whole Genome Sequencing and Sequence Analysis of a Yak Milk-Derived Bacteriocin-Producing Weissella confusa ZW21
2023, 44(20):  119-126.  doi:10.7506/spkx1002-6630-20221126-303
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In order to explore the antibacterial mechanism of Weissella confusa ZW21, a strain of lactic acid bacteria from yak milk with good antibacterial activity, its whole genome sequence was analyzed and its antibacterial activity-related functional genes were mined. In this study, the whole genome of W. confusa ZW21 was sequenced and analyzed on the Illumina NovaSeq PE150 platform, and the basic functions of the genome were annotated in the Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), Cluster of Orthologous Groups, Non-Redundant Protein databases. The results showed that: (1) the genome size of W. confusa ZW21 was 2.44 Mb, and the GC content was 45.66 %; (2) 2 175 encoding genes were predicted, with a total length of 1 947 771 bp and an average length of 896 bp; and (3) the encoding genes were annotated in the functional database for basic functional annotation and metabolic pathway gene information annotation of the strain’s genome, revealing that the genome contained eight bacteriocin-related genes (such as Colicin V and Lactococcin); three antioxidant activity-related genes; signaling pathways that regulate immunity and inflammation such as the nucleotide oligomerization domain (NOD)-like receptor and peroxisome proliferators-activated receptor (PPAR) signaling pathways, and antifolate encoding genes. In summary, the whole genome sequencing and analysis of W. confusa ZW21 can provide a basis for studying its antibacterial mechanism.
Isolation, Purification, Identification, and Analysis of Jug r 1, a Major Allergenic Protein in Walnut
SHEN Mingjuan, LI Yunqian, YANG Xi, WANG Yongqin, SHA Xiaomei, ZHANG Xuechun
2023, 44(20):  127-135.  doi:10.7506/spkx1002-6630-20230408-070
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In this study, by using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and double-sandwich enzyme-linked immunosorbent assay (ELISA), Juglans sigillata kernels from seven different production areas in Yunnan province were screened for their Jug r 1 contents. The preparation of Jug r 1 through ammonium sulfate precipitation, gel filtration chromatography (GFC), and liquid chromatography-tandem mass spectrometry (LC-MS/MS) was optimized and the product was identified. Its structure was characterized by circular dichroism (CD) spectroscopy. Finally, Jug r 1 content in walnut protein was measured by ELISA. The results showed that walnuts from Baoshan, which had the highest contents of total protein and Jug r 1, were used for subsequent experiments. The optimal concentration of ammonium sulfate saturation was in the range from 40% to 80%, and the optimal conditions for GFC were sample concentration of 30 mg/mL, loading volume of 4 mL, and elution flow rate of 1 mL/min. Under these conditions, the recovery of Jug r 1 was 16.58%. Mass spectrometry analysis showed that this protein had the typical characterisitcs of Jug r 1. Circular dichroism spectroscopy indicated that the secondary structure of Jug r 1 was dominated by α-helix and consisted of multiple conformations. After separation and purification by a two-step process, Jug r 1 with purity more than 96% was obtained. This study can provide a scientific basis for further research on Jug r 1 and also provide a reference for the separation and purification of allergic proteins from other nuts.
Effects of Biodynamic Vineyard Management on Yeast Community and Aroma Components in ‘Cabernet Sauvignon’ Wine
CHEN Xuelian, ZANG Wei, LIU Yu, JIANG Zhanzhan, PENG Shuai, WANG Jing
2023, 44(20):  136-145.  doi:10.7506/spkx1002-6630-20221024-244
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In order to explore the effects of biodynamic vineyard management on the yeast community structure and volatile aroma components during wine fermentation, Cabernet Sauvignon grapes from biodynamic (BD) and conventional (CV) vineyards were naturally fermented, and the composition and succession of yeast community and aroma components were analyzed during the fermentation process, and the correlation between yeast communities and aroma components was analyzed by redundant analysis (RDA). The results showed significant differences in the yeast community composition between the BD and CV samples at different fermentation stages. At the early stage, Hanseniaspora uvarum, Starmerella bacillaris, Pichia kudriavzevii, Issatchen kiaorientalis and Cryptococus flavescens were the dominant species in BD, while H. uvarum, Metschnikowia pulcherrima and C. flavescens were the dominant species in CV. As the fermentation proceeded, the yeast species in BD and CV increased to 9 and 7 at the middle stage, respectively. H. uvarum was the dominant yeast in both samples. The non-Saccharomyces species decreased at the later and final stages of fermentation, Saccharomyces cerevisiae gradually became the dominant species, but Hanseniaspora opuntiae and S. bacillaris were found in CV but not BD at the end of fermentation. During the alcoholic fermentation process, the total content of aroma compounds was significantly higher in BD than in CV. Meanwhile, at all stages of fermentation, the contents of alcohols, aldehydes, and terpenes were higher in BD than in CV. However, the content of esters was lower in BD than in CV. RDA analysis showed that S. cerevisiae was positively correlated with the contents of all characteristic aroma components except benzaldehyde, and non-Saccharomyces yeasts (H. opuntiae, P. kudriavzevii, etc.) were positively correlated with the contents of 1-hexanol, benzaldehyde and ethyl acetate. In summary, this study provides data support for understanding the influence of different vineyard managements on the microbial diversity of vineyard and the aroma quality of grape and wine.
Screening and Evaluation of Amplicons of Maize Endogenous Reference Genes Based on Next-Generation Sequencing Technology
CHEN Lihong, ZHOU Junfei, LIANG Jingang, Li Tiantian, WANG Haoqian, FANG Zhiwei, CHEN Hong, PENG Hai
2023, 44(20):  146-154.  doi:10.7506/spkx1002-6630-20221101-006
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In this study, 13 amplification regions (amplicons) were designed by analyzing the nucleotide sequences of seven endogenous reference genes reported in previous studies. Totally 208 common maize varieties (lines) were used for high-throughput sequencing analysis of these 13 amplicons, and their sequence conservation, specificity, detection stability and dynamic detection range were evaluated to select appropriate amplicons of the endogenous reference genes for quantitative detection of maize DNA content or copy number based on next-generation sequencing technology. The results showed that the detection rates of the 13 amplicons of the seven endogenous reference genes were 94.7%–100% in the 208 maize samples, while they were not detected in 25 non-maize samples of rice, soybean, cotton and Chinese cabbage, indicating that these amplicons met the standards of high intraspecies consistency and interspecies specificity. Intraspecies conservation analysis showed that E3-UBI-1 did not contain single nucleotide polymorphism (SNP) or insertion deletion (InDel), while the remaining 12 amplicons contained at least one SNP or InDel. Stability analysis showed that the most unstable amplicon in these endogenous reference genes was IVR, and the most stable one was ADH1-2. Their dynamic detection range was 0.2–200 ng. Based on these results, ADH1-2 and E3-UBI-1 are suitable amplicons of the endogenous reference genes for quantitative detection of maize DNA content or transgenic maize components on the next-generation sequencing platform.
Characteristics of Soymilk Fermented by Lactic Acid Bacteria with Different β-Glucosidase Activities
LUO Yue, LIU Ruishan, WANG Zhiyuan, CHAI Lijuan, LU Zhenming, SHI Jinsong, ZHANG Xiaojuan, XU Zhenghong
2023, 44(20):  155-164.  doi:10.7506/spkx1002-6630-20221108-079
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This study evaluated the β-glucosidase activities of 10 strains of Lactobacillus plantrum, L. helveticus, L. pentosus, and Streptococcus thermophilus) and compared the fermentation performance of the strains and the antioxidant properties and flavor quality of soymilk fermented by each of these strains. Moreover, the contents of isoflavones in fermented soymilk were analyzed. The results showed differences in the β-glucosidase activity of the different LABs, all of which showed good growth in soymilk, and L. plantarum was more suitable for growth in soymilk. LAB fermentation promoted the conversion of soybean isoflavones to active aglycones, and improved the nutritional characteristics of soymilk. Meanwhile, LAB changed the composition and content of volatile components, and effectively reduced the contents of hexanal, nonanal and 2-pentylfuran, which have been reported to be responsible for beany flavor, while retaining the characteristic aroma compounds of soymilk. Strains LPL044 and LPL051, with the highest β-glucosidase activity, showed the strongest ability to convert soymilk isoflavones, and the fermented soymilk had the highest contents of total phenols and total flavonoids, the strongest antioxidant activity and the best sensory quality, so they have greater research and development value compared with the other LABs.
Comparative Analysis of Microbial Community Diversity and Physicochemical Factors of Nongxiangxing Baijiu Pit Mud at Different Ages and Cellar Locations
XIAO Qin, HE Ping, ZHOU Ruiping, LIU Chao, YUAN Siqi, ZHAO Jinsong
2023, 44(20):  165-174.  doi:10.7506/spkx1002-6630-20221018-173
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In this study, high-throughput sequencing technology, linear discriminant analysis effect size (LEfSe) and redundancy analysis (RDA) were used to investigate the structure of prokaryotic and eukaryotic communities, the differential microbial communities, and the relationship between microorganisms and physicochemical factors in pit mud (PM) from cellars of different ages (5, 10 and 20 years) and from different spatial locations of cellars. The results showed that the diversity of both prokaryotic and eukaryotic microorganisms was higher in the five-year-old PM than in the 10- and 20-year-old PM. Among all samples, a total of 37 phyla, 83 classes, 176 orders, 306 families and 629 genera of prokaryotic microorganisms were detected, with five phyla being the dominant ones. Totally 12 phyla, 37 orders, 74 families, 160 families and 282 genera of eukaryotic microorganisms were detected, including three phyla and 15 genera being dominant. LEfSe identified 12 differential prokaryotic genera and 15 differential eukaryotic species, and the differential microbial communities of each sample played an important role in the fermentation process of baijiu. The results of physicochemical analysis showed that the pH of the PM samples varied from 3.66 to 5.20, and the effective phosphorus content of PM was significantly different among locations. RDA analysis showed that Lactobacillus, unclassified_f__Aspergillaceae, and Thermomyces were negatively correlated with moisture, ammonia nitrogen, and effective phosphorus contents, and Methanobacterium, Clostridium_sensu_stricto_12, Caproiciproducens, Methanobrevibacter, Cryptococcus_f__Tremellaceae and Apiotrichum were positively correlated with moisture, pH, ammonia nitrogen, and effective phosphorus. This study provides theoretical support for the establishment of daily PM maintenance as well as high-quality PM domestication and production.
Cloning and Expression of an Aspartic Protease Gene from Trichoderma asperellum and Its Application to the Hydrolysis of Soy Protein Isolate
ZHOU Di, QIU Xiaoxian, KE Ye, HU Qiuyi
2023, 44(20):  175-182.  doi:10.7506/spkx1002-6630-20230212-105
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In order to explore the application potential of aspartic protease (Asp) of Trichoderma sp., the protease gene (asp) was cloned from Trichoderma asperellum by real-time polymerase chain reaction, and was successfully expressed in Pichia Pastoris GS115. The recombinant protease (rAsp) was isolated and purified, and its biochemical properties and its effectiveness in hydrolyzing soy protein isolate (SPI) were studied. The results showed that the protease encoded by the asp gene belonged to the aspartic protease family, and its sequence identity with other members of this family was up to 47.74%. The protease activity of rAsp in the fermentation broth obtained by induced expression in a conical flask was 25.8 U/mL. The optimal reaction pH and temperature of rAsp were 2.5 and 45 ℃, respectively, and rAsp had strong stability in the pH range of 2.0–6.0 and below 45 ℃. The activity of rAsp was promoted by Cu2+ and Mn2+ but inhibited by Fe3+, sodium dodecylsulfate (SDS) and pepstantin. The hydrolysis efficiency of SPI with rAsp was 7.7% higher than that with commercial pepsin. Moreover, the ability of rAsp to reduce the allergenicity of β-conglycinin and glycinin was 1.4 and 1.8 times greater than that of the pepsin, respectively. Therefore, rAsp has potential application in soy protein processing.
In Vitro Prebiotic Activity of Polysaccharide Fractions from Tangerine Peel
TIAN Changcheng, TAO Zhijie, LI Jing, MAN Yun, ZHAO Daqing
2023, 44(20):  183-188.  doi:10.7506/spkx1002-6630-20221011-104
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Crude water-soluble polysaccharides (Cpp) from 10-year-old tangerine peel were hydrolyzed with sulphuric acid and fractionated by successive ion exchange adsorption and size exclusion chromatography into three major fractions (f1-1, f2-2 and f3-2). The structures and prebiotic activities of Cpp and the fractions were compared. The results showed that f2-2 had the smallest molecular mass of 1.15 × 104 Da and was mainly composed of rhamnose, arabinose and galactose with a molar ratio of 0.21:1.00:0.25. f2-2 could promote the proliferation of Lactobacilli and Bifidobacterium, increasing their counts 3.2 and 2.9 times compared with the control group (with 1 mg/mL glucose), respectively. Cpp could only promote the proliferation of Lactobacilli significantly (P < 0.05). Compared with the control group, the addition of f2-2 significantly increased the production of propionic acid in the culture supernatant of human fecal bacteria (P < 0.05). Moreover, the addition of f1-1 or f2-2 promoted the production of butyric acid. To sum up, the polysaccharides from 10-year-old tangerine peel showed significant prebiotic characteristics, which had a close relationship the structures of the polysaccharides.
Effect of Adding Hyaluronic Acid with Various Molecular Masses on the Quality of Yogurt
ZHOU Haidong, TANG Shanhu, LI Sining, LIAO Binxu, MA Yuan, LUO Zhuoling, WANG Jianxiang, PAN Kun, CHEN Hanshuanglu
2023, 44(20):  189-197.  doi:10.7506/spkx1002-6630-20230105-028
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Fresh milk with added hyaluronic acid (HA) was fermented by inoculating Streptococcus thermophilus and Lactobacillus bulgaricus. By measuring the pH, water holding capacity, viable bacteria count, rheological properties, volatile flavor substances, stability of yoghurt, the effects of HA with various molecular masses and various amounts of HA on the quality of yoghurt were evaluated. The results showed that various molecular masses of HA had different effects on the quality of yoghurt, but all could significantly improve its water holding capacity, smoothness and fineness (P < 0.05). The addition of high molecular mass (1 280 kDa) HA improved the elastic modulus (G’) and viscosity modulus (G”) of yoghurt, enhanced its stability index, promoted the growth and reproduction of L. bulgaricus and S. thermophilus, but caused obvious whey syneresis at the end of fermentation. Medium molecular mass (350 kDa) HA inhibited the growth and reproduction of L. bulgaricus, increased the pH, reduced the titratable acidity, and optimized the sensory quality of yoghurt. Low molecular mass (180 kDa) HA reduced the stability of yoghurt. To sum up, medium molecular mass HA can improve the quality of fermented milk.
Influence of Fermentation by Four Fungi on Chemical Constituents and Pharmacological Activities of Panax notoginseng Leaves
YANG Jinmei, LI Yunqian, HE Xiahong, WANG Zhenxing
2023, 44(20):  198-211.  doi:10.7506/spkx1002-6630-20230416-149
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In this study, Panax notoginseng leaves (PNL) were separately fermented by Rhizopus oryzae, Neurospora crassa, Monascus and Mucor rouxianus, and changes in the contents of total saponins, total polysaccharides, total phenolics, and total flavonoids, as well as in vitro antioxidant activity and α-glucosidase inhibitory activity of PNL during the fermentation process were assessed. Additionally, the metabolite profiles of raw and fermented PNL were analyzed by ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS/MS). The results indicated that the contents of total saponins and total polysaccharides in PNL were significantly reduced by fermentation with each of these four fungi. Interestingly, R. oryzae, N. crassa and Monascus were found to increase the content of total phenols, while Rhizopus oryzae and Mucor rouxianus increased the total flavonoid content. Fermentation for 3–5 days significantly enhanced the antioxidant activity of PNL, and the most pronounced effect was achieved with Monascus fermentation for three days, which increased the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical cation scavenging capacity and ferric reducing capacity by 14.30%, 5.13%, and 18.40%, respectively. Moreover, the α-glucosidase inhibitory activity of PNL initially decreased and then increased during fungal fermentation, which increased by 16.03% after Monascus fermentation for six days. By untargeted metabolomics analysis, 573 metabolites were identified from PNL. After three days of Monascus fermentation, the up-regulated metabolites were significantly less than the down-regulated ones, and the predominant up-regulated metabolites were amino acids, alkaloids, carbohydrates, lipids, phenols, flavonoids, and terpenoids. Furthermore, analysis of the 21 saponins showed that only ginsenoside F2 was significantly up-regulated, while eight other saponins were significantly down-regulated. The Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis indicated that co-factor biosynthesis, flavonoid biosynthesis, purine metabolism, and pyrimidine metabolism were the most probable metabolic pathways during the fermentation process. In conclusion, fungal fermentation, especially Monascus fermentation, can effectively improve the functional activity of P. notoginseng by metabolic alterations through various pathways. Therefore, this study provides a scientific reference for the green processing of PNL.
Component Analysis
Sensomics Analysis of the Changes in Key Taste Components of Trachypenaeus curvirostris during Thermal Treatment
JIA Qiannan, HOU Hu, WANG Cong, SUN Yan, FAN Yan
2023, 44(20):  212-218.  doi:10.7506/spkx1002-6630-20221215-161
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In order to identify the key taste components of Trachypenaeus curvirostris, the flavor characteristics of free amino acids, inorganic ions, quaternary ammonium compounds, saccharides, organic acids, nucleotides, glutathione in raw and cooked shrimps were determined by high performance liquid chromatography (HPLC), atomic absorption spectrometry (AAS), high performance liquid chromatography-mass spectrometry (HPLC-MS), electronic tongue (EN) and taste recombination experiments based on sensomics. The results showed that the total content of free amino acids in shrimp increased by 19.79% from 1 165.94 to 1 396.64 mg/100 g after heat treatment, and the contents of Gly, Arg, Pro, Ser and Tau significantly increased. The contents of Na+ and Cl- were higher in cooked shrimp, and so were betaine, trimethylamine-N-oxide, nucleotide and their derivatives. In addition, the taste activity values (TAV) of glutamic acid, glycine, Na+, Cl-, lactic acid and 5’-IMP were greater than 1, indicating that they might be active compounds contributing to the taste of T. curvirostris. The results of taste recombination experiments showed that the flavor profile of the recombination model was similar to that of the natural extract. The key taste compounds identified were glutamic acid, glycine, alanine, tyrosine, arginine, 5’-IMP, 5’-GMP, Na+, K+, Cl-, betaine and trimethylamine-N-oxide. This study lays a theoretical foundation for the processing of T. curvirostris.
Changes in Volatile Flavor Substances during Postharvest Infection of Fresh Ginger with Fusarium graminearum
MENG Xiuling, NIU Ben, GAO Haiyan, LIU Ruiling, CHEN Huizhi, WU Weijie, CHEN Hangjun
2023, 44(20):  219-226.  doi:10.7506/spkx1002-6630-20230407-057
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In this study, Fusarium graminearum was identified as the pathogen causing the decay of ginger from Jiangshan, Zhejiang Province during postharvest storage by tissue separation, morphological characterization, ribosomal DNA internal transcribed spacer (rDNA-ITS) sequence analysis and phylogenetic tree construction. By using solid phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS), the changes of volatile flavor in fresh ginger during infection with F. graminearum postharvest were studied through the determination of volatile flavor compounds in healthy tissues, the junction between healthy and diseased tissues, and diseased tissues of fresh ginger. Principal component analysis (PCA) was used to evaluate the flavor quality of fresh ginger during postharvest disease development. The results showed that a total of 58 volatile flavor substances were detected in ginger, of which 40 substances were detected in healthy tissues, 35 substances in the junction of diseased and healthy tissues, and 39 substances in diseased tissues. These volatile flavor substances mainly included olefins, alcohols, esters, aldehydes, and ketones. Olefin compounds were the major components contributing to fresh ginger flavor, accounting for more than 80% of all flavor compounds. During disease development, the content of olefin flavor compounds increased significantly (P < 0.05), and the sesquiterpene components zingiberene and β-sesquiterpene were detected in different parts of fresh ginger and their contents continued to increase, which could be used as the indexes for determining whether or not fresh ginger is infected with F. graminearum after harvest. This may be due to the activation of the resistance mechanism of pathogen infected fresh ginger and consequent release of sesquiterpene components in large quantities.
Water Distribution in Starch Hydrogel Systems
LIN Shunshun, SHI Jiaqi, SUN Fucai, JIANG Lili, MA Bingtuan, LI Mengqin
2023, 44(20):  227-235.  doi:10.7506/spkx1002-6630-20221205-044
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The water distribution in hydrogel systems prepared from six different starches at different concentrations was analyzed by low-field nuclear magnetic resonance (LF-NMR) spectroscopy. The results showed that legume (corn and wheat) and legume (pea and mung bean) starch gels exhibited three water forms, while tuber (sweet potato and potato) starch gels exhibited only two water forms. Immobilized water (T23) was the major water form in the six starch gels. With increasing starch concentration (5%–14%), the transverse relaxation time decreased, and the ability of starch gels to bind immobilized water increased. At the same starch concentration, the ability of pea starch gels to bind water was the strongest, while that of potato starch gels was the weakest, and that of cereal starch gels was in the middle. With increasing starch concentration, the relative content of immobilized water in starch gels decreased, and the differences among legume, tuber and cereal starch gels became more obvious. This study provides a theoretical reference for the improvement of sensory texture in starch-based food processing.
Effect of Marination in Papaya Juice on the Flavor Formation of Boiled Wenchang Chicken
ZHANG Zihan, WU Yucan, SONG Yu, ZHAO Guiping, WEI Limin, ZHANG Chunhui, HUANG Feng
2023, 44(20):  236-244.  doi:10.7506/spkx1002-6630-20221209-093
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In order to explore the influence of papaya juice marination on the flavor formation of boiled Wenchang chicken, the physicochemical indexes of e raw chicken breast and drumstick meat were detected, and the changes in the volatile flavor and taste substances of boiled chicken breast and drumstick meat with and without papaya juice marination were analyzed. Results showed that the contents of proteins and reducing sugar were significantly higher and fat content was significantly lower in raw chicken breast meat than in drumstick meat (P < 0.05), while there was no significant difference in thiamine content between them (P > 0.05). The types and contents of aldehydes and alcohols in marinated chicken drumsticks were significantly increased, and nine new aldehydes were produced, including (E)-2-heptanal, (E)-2-octenal, (E)-2-nonaldehyde, (Z)-2-decanal, 2-butyl-2-octenal, 4-ethylbenzaldehyde, 2,5-dimethylbenzaldehyde, (E)-2-undecenal, and (E,Z)-2,4-decandienal. However, there was no significant change in volatile compounds in chicken breast before and after papaya juice marination. The electronic nose could distinguish the difference of chicken drumsticks but not of chicken breast before and after papaya juice marination. The contents of free amino acids and flavor nucleotides in chicken breast and drumstick meat were significantly increased after papaya juice pickling. In conclusion, papaya juice can increase the contents of nucleotides and free amino acids in breast and drumstick meat of Wenchang chicken, increase the contents of volatile flavor substances in chicken drumstick, and impart new flavor substances such as aldehydes and alcohols to drumstick meat.
Effects of Heat Treatment Methods on Nutrient Composition and Antioxidant Activity of Purple-Fleshed Potato
LAI Dengni, ZHU Xiangrong, LI Tao, ZHANG Qun, PENG Qinghui
2023, 44(20):  245-251.  doi:10.7506/spkx1002-6630-20220917-164
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The effects of three cooking methods: microwave (25 W/g for 3.5 min), baking (60 ℃ for 2 h), and water boiling (100 ℃ for 15 min) on the major nutrients and bioactive substances in two varieties of purple-fleshed potato were analyzed so as to provide a scientific basis for the thermal processing of purple-fleshed potato. The results showed that after heat treatment, the contents of vitamin C, ash, starch, and total phenols (calculated as chlorogenic acid) decreased. After microwave treatment, the protein contents of the two varieties increased by 3.29% and 3.21%, but decreased by 2.20% and 1.97% after baking and 1.91% and 1.41% after boiling treatment, respectively. The anthocyanin content of the Black Diamond cultivar increased by 22.92% and 16.67%, respectively, after microwave and water boiling treatment, but decreased after baking treatment. In addition, microwave treatment significantly improved the reducing capacity of purple-fleshed potato anthocyanin extract, and the anthocyanin extract significantly enhanced the expression levels of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) in RIN-m5F pancreatic islet β cells and reduced the expression level of nuclear transcription factor kappa B (NF-κB). In conclusion, microwave treatment was the best heat treatment method for purple-fleshed potato.
Changes in Active Components and Antioxidant Properties of Ginseng Fermented by Lactobacillus plantarum
LIU Shiwei, LIU Shengnan, MI Qianwen, YIN Pei, XUE Tingfang, YU Xiaoran, MENG Xingjian, WANG Lina, BI Yunfeng
2023, 44(20):  252-259.  doi:10.7506/spkx1002-6630-20221127-309
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Ginseng extract was fermented by the probiotic Lactobacillus plantarum to investigate the changes in its active ingredients and antioxidant activities before and after fermentation. The contents of total phenols, polysaccharides, total flavonoids and ginsenosides in raw and fermented ginseng extract were determined, and their antioxidant activities were evaluated by determining three free radical scavenging capacities, reducing power and lipid oxidation inhibitory activity. The results showed that the contents of total phenols, total flavonoids increased, while the contents of polysaccharides and total saponins decreased after fermentation. Ginsenosides Rg1, Re, Rb1 and Rc were hydrolyzed into rare ginsenosides such as Ck, Rk1, Rh4, and Rg5 during the fermentation process, and their contents increased by 0.770 6, 0.734 8, 3.392 4 and 1.364 8 mg/g, respectively. The antioxidant capacity of fermented ginseng extract at concentrations of 0.5–20 mg/mL increased compared with that before fermentation, which was inextricably related to the increase in the contents of total phenols and total flavonoids and the generation of rare ginsenosides. This shows that the fermentation process can produce a large amount of rare saponins and increase the contents of phenols and flavonoids, which makes fermented ginseng extract have stronger antioxidant ability.
Metabolomics Combined with Intelligent Sensory Detection to Investigate Effect of Clinical Mastitis on Flavor and Taste Substances in Milk
LU Xuan, ZHANG Qian, ZHAO Yuxuan, YI Yuwen, TANG Junni, DENG Jing, YANG Falong, ZHU Chenglin
2023, 44(20):  260-267.  doi:10.7506/spkx1002-6630-20221213-131
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In order to deeply understand the impact of clinical mastitis on the physicochemical properties, flavor and taste of cow milk, a milk composition analyzer combined with an electronic nose and an electronic tongue was used to distinguish milk from cows with and without clinical mastitis. Moreover, nuclear magnetic resonance (NMR) spectroscopy was used to identify and quantify small molecules in milk samples. The fat content of mastitic milk was significantly lower than that of milk form healthy cows, while the density, protein and freezing point were significantly higher than those of milk from healthy cows. The electronic nose and the electronic tongue were able to distinguish the differences in the flavor and taste of milk from normal and mastitic milk. A total of 54 small molecules were identified in the two milk samples, including amino acids (17), organic acids (15), carbohydrates (7), nucleosides, nucleotides and their derivatives (5). The concentrations of 23 compounds significantly differed between both milks. A total of 16 predominant compounds were found in normal milk, and seven in mastitic milk. The contents of amino acids and organic acids in mastitic milk significantly increased, resulting in unpleasant sour odor of milk. This study provides a scientific rationale for the discrimination between normal and clinical mastitic milk and for the quality control of raw milk
Analysis of Differences in Chemical Constituents of Rougui Rock Tea with Different Roasting Degrees by Ultra-high Performance Liquid Chromatography-Quadrupole Orbitrap Mass Spectrometry
ZHONG Qiusheng, PENG Jiakun, DAI Weidong, LIN Zhi, LÜ Haipeng, CHEN Quanbin, LI Xinlei, CHEN Changsong
2023, 44(20):  268-282.  doi:10.7506/spkx1002-6630-20221205-052
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In order to investigate the influence of different roasting degrees on the quality and chemical composition of Rougui rock tea (Camellia sinensis (L.) O. Kuntze cv. Rougui), the non-volatile chemical compositions of tea samples processed at different roasting temperatures (low fire: 100 ℃, medium fire: 120 ℃, high fire: 140 ℃) and for different time periods (2, 4, 6, 8 and 10 h) were systematically investigated by metabolomics based on ultra-high performance liquid chromatography-quadrupole orbitrap mass spectrometry (UPLC-Q-Exactive/MS), and their quality was evaluated by sensory evaluation. A total of 144 compounds were structurally identified, belonging to 11 chemical classes including catechins, dimeric catechins, flavonoid glycosides (flavonol-O-glycosides and flavone-C-glycosides), N-ethyl-2-pyrrolidinone-substituted flavan-3-ols (EPSFs), amino acids, phenolic acids, organic acids, alkaloids, and lipids. Partial least squares discriminant (PLSD) analysis and heatmap analysis showed distinct differences in chemical components among rock tea samples with different baking treatments. A total of 84 compounds that significantly differed among treatment groups were identified (P < 0.05). The contents of most amino acids, epicatechins, dimeric catechins (theaflavins and theasinensins), alkaloids (5’-methionosine and adenosine phosphate), phenolic acids (isochlorogenic acid, strictinin and theogallin), and flavonoid glycosides were gradually decreased with roasting time at 120 ℃, while most lipids (MG(18:3), LysoPC(18:3), and palmitic acid), some flavonol aglycones (myricetin, kaempferol, and quercetin), and some organic acids (pyroglutamic acid and 5-hydroxymethyl-2-furfural) showed the opposite trend. The contents of most EPSF compounds were increased linearly with roasting temperature and time, but it was gradually decreased with baking time at 140 ℃. Sensory evaluation showed that low-temperature long-time (8–10 h at 100 ℃) and medium-temperature short-time (2–4 h at 120 ℃) were beneficial for the quality improvement of rock tea. This study provides a theoretical basis for the quality improvement of Wuyi rock tea.
Analysis of Differential Metabolites of Phyllostachys edulis Shoots at Different Growth Stages by Ultra-high Performance Liquid Chromatography-Tandem Mass Spectrometry
GUO Mingyang, HE Yuelin, PAN Kaiting, BAO Fangyan, YING Yeqing
2023, 44(20):  283-291.  doi:10.7506/spkx1002-6630-20230207-060
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The dynamic changes of differential metabolites of Phyllostachys edulis shoots at three stages including ground breaking (S1, 5 cm high), growth (S2, 20 cm high) and rapid growth (S3, 40 cm high) were studied by widely targeted metabolomics combined with basic physiological indices. The results of physiological analyses showed that the nutritional and flavor quality was better at the ground breaking stage than at the other growth stages. A total of 765 metabolites were identified by metabolomics. Multivariate statistical analysis showed that the composition of metabolites varied significantly among growth stages. There were 203 differentially accumulated metabolites identified, among which lipids, amino acids, organic acids, phenolic acids, flavonoids and alkaloids remarkably changed. The nutritional quality at the ground breaking stage could be closely related to the enrichment of most flavonoids, free fatty acids, amino acids and neochlorogenic acid. At the latter two stages, bamboo shoots mainly contained lipids, amino acid derivatives, organic acids, phenolic acids and melatonin as well as a large number of bioactive ingredients, which could be closely related to improving the environmental adaptability of bamboo shoots. The results of this study provide a theoretical basis for understanding the nutritional value of P. edulis shoots and for the exploitation and utilization of bamboo resources.
Analysis of the Flavor Quality of Coffee Using Multiple Omic Technologies Combined with Electronic Sensory Detection Technology
LI Yulian, ZHENG Jianyi, HUANG Xuhui, DONG Xiuping, ZHAO Baomin, QIN Lei
2023, 44(20):  292-299.  doi:10.7506/spkx1002-6630-20230306-053
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By the combined use of metabolomics, flavoromics, and rapid electronic sensory detection technology, this study identified and analyzed the differences in flavor quality of six coffees. The results suggested that 2,6-dimethylpyrazine, 2-ethylhexan-1-ol, acetoin, isovaleric acid, and methyl valerate could be employed as aroma markers to distinguish coffees with different degrees of roasting. Additionally, 48 compounds, including guanine, tryptophan-alanine, crotonic acid, and 1-methyladenosine, were found to be the metabolic difference indicators to distinguish coffee powder from different geographical origins and their mixed samples. The major taste compounds of lightly roasted coffee were 1,4-D-xylose, alanine, isoleucine, and phenylalanine. Maltotriose was found to be a major compound in moderately roasted coffee, which also contained a lesser amount of inosine. The combination of electronic nose and electronic tongue detection with principal component analysis (PCA) could be used for rapid classification and variety identification of coffee. These results provide a theoretical basis and technical support for the production of coffee as well as a reference for establishing standards to evaluate the flavor and quality of coffee.
Effect of Fermentation Temperature on the Main Flavor Substances in Low-Salt Shrimp Paste
YANG Bingbing, WANG Liwen, CHEN Zhihui, LIU Yangliu, CHEN Chunjiang, SUN Jilu
2023, 44(20):  300-308.  doi:10.7506/spkx1002-6630-20221122-253
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In order to study the effect of fermentation temperature on the flavor substances in low-salt shrimp paste, the natural fermentation of shrimp paste was carried out at 10, 15, 20 or 25 ℃. The contents of free amino acids, free fatty acids and volatile compounds in shrimp paste were determined by high performance liquid chromatography (HPLC), gas chromatography (GC) and gas chromatography-ion mobility spectrometry (GC-IMS), respectively. The results showed that 17 free amino acids and 26 free fatty acids were detected in each shrimp paste sample. The content of flavor amino acids was highest in shrimp paste fermented at 10 ℃, and the content of free fatty acids was highest in shrimp paste fermented at 20 ℃. A total of 69 volatile compounds were identified in all samples, including 19 alcohols, 13 aldehydes, 13 ketones, 12 esters, 2 alkenes, 2 ethers, 1 acid and 7 other compounds. The relative contents of alcohols and ketones were higher in shrimp paste fermented at 10 ℃ and 15 ℃. The relative contents of ammonia were higher in shrimp paste fermented at 20 or 25 ℃. Principal component analysis (PCA) showed that volatile compounds were significantly distinguishable in low-salt shrimp pastes fermented at different temperatures. A total of six differential volatile compounds (variable importance in projection (VIP) >1, P < 0.05) were identified by orthogonal partial least squares-discriminant analysis (OPLS-DA), namely 3-methyl-1-butanol (monomer and dimer), ethyl acetate dimer, ethyl acrylate, 2-methylbutanal dimer and ammonia. Cluster heatmap analysis showed that the flavor of low-salt shrimp paste fermented at 10 and 15 ℃ was similar, and the flavor of low-salt shrimp paste fermented at 20 and 25 ℃ was similar. The results of this study may provide a theoretical basis for promoting the thermostatic fermentation of commercialized low-salt shrimp paste.
Composition and Digestion Characteristics of Starch in Endosperm of Glutinous Rice Varieties
CHEN Shuangqin, GU Xue, HUANG Juyuan, LI Dandan, LI Juan, MA Yangyongjie, PU Shihuang, LI Jizhang, YANG Guoming, WEN Jiancheng
2023, 44(20):  309-314.  doi:10.7506/spkx1002-6630-20221209-090
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In this study, the starch components, digestible sugar contents (glucose content produced by starch digestion) and expected glycemic index (eGI) values of 65 glutinous rice varieties were analyzed by an in vitro enzyme digestion method. The results showed that starch composition varied greatly among the 65 varieties, with total starch contents ranging from 70.63% to 76.72%, resistant starch contents ranging from 0.17% to 3.79%, rapidly digestible starch contents ranging from 40.51% to 52.37%, and slowly digestible starch contents ranging from 19.92% to 32.47%. Glucose was released quickly from digested glutinous rice starch and the release process lasted for a long time. The amount of sugar released increased sharply within 30 min after meals and then decreased continuously, and the glucose content was minimum during 60–90 min and increased slightly during 90–180 min. eGI values ranged from 67.1 to 79.1, and 80% of the varieties had eGI values above 70, belonging to high sugar varieties. The eGI value of Bananuo 18 was the highest, and that of Dehui 2290 was the lowest. Starch content was correlated with the amount of released glucose and eGI. Rapidly digestible starch contributed to the rapid increase of blood glucose in the early stage, and slowly digestible starch and resistant starch were beneficial to the slow increase of blood glucose. The results can provide data reference for people who need to control their blood glucose levels and pay attention to the quality of glutinous rice.
Simultaneous Determination of Vitamins A, D and E in Foods for Special Medical Purposes by Online Solid Phase Extraction Combined with Two-Dimensional Liquid Chromatography
ZHAI Hongwen, MA Hongyu, MA Junmei, CAO Meirong, WANG Jing, WANG Juan, LI Qiang
2023, 44(20):  315-320.  doi:10.7506/spkx1002-6630-20220923-241
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A rapid method for the determination of VA, VD (VD2, VD3) and VE (α-, β-, γ-, and δ-vitamin E) in foods for special medical purposes was established using online solid phase extraction (SPE) combined with two-dimensional liquid chromatography (2D-LC). After saponification, enrichment and purification of VA, VD and VE from samples were accomplished on an online SPE cartridge. VA and four VEs were quantitatively analyzed by the first-dimensional LC, and VD was transferred by heart-cutting to the second-dimensional chromatographic system for separation and detection. SPE columns with different fillings, sample loading solvents, and eluent composition were evaluated, and 2D-LC conditions were systematically optimized. Good linearity was achieved for all vitamins tested with correlation coefficients (R2) greater than 0.997. The mean recoveries of the developed method were 84.4%–109.0% with relative standard deviation (RSD) of 0.34%–6.55% (n = 6). This method was highly automated with low detection errors and high detection efficiency, and could be used for the analysis of vitamins in foods for special medical purposes.
Identification of Panax notoginseng Powders from Different Root Parts Using Electronic Nose and Gas Chromatography-Mass Spectrometry
LI Lixia, ZHANG Hao, LIN Yuhao, SHI Lei, LI Shanshan, ZHANG Fujie, WANG Jun
2023, 44(20):  321-329.  doi:10.7506/spkx1002-6630-20221129-332
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In order to identify Panax notoginseng powders from different root parts, an electronic nose and gas chromatography-mass spectrometry (GC-MS) were used to analyze the volatile components of the whole root powder, rhizome powder, taproot powder, lateral root powder and fibrous root powder of P. notoginseng. The data obtained were analyzed by multiple comparison. The statistical learning method was used to extract eight time-domain features from the response curves of the electronic nose, and correlation analysis was carried out. Three feature selection algorithms were used to reduce the dimension of the feature data. Classification models were built using support vector machine (SVM), least square support vector machine (LSSVM) or extreme learning machine (ELM) based on the original feature data or the three kinds of feature selection data. The grey wolf optimization (GWO) algorithm was introduced to optimize the parameters gam and sig2 in the classification model. The results showed that a total of 31 volatile compounds were detected in the five P. notoginseng powders. The best GWO-IRIV-LSSVM model could effectively distinguish the electronic nose data, with 97.5% accuracy for the test set. Moreover, the volatile composition of the five samples differed mainly in terms of the contents of total volatiles, alkanes, and aromatic compounds, which was consistent with the results of GC-MS. The method used in this study can be used for the detection of high-quality P. notoginseng powder from geo-authentic production areas mixed with low-quality P. notoginseng powder.
Effect of Co-fermentation with the Apple Endophyte Torulaspora delbrueckii on the Synthesis of the Flavor Substances of Apple Vinegar
SONG Xuemiao, MA Shiyuan, LI Zijian, LUO Huibo, HUANG Dan
2023, 44(20):  330-342.  doi:10.7506/spkx1002-6630-20221030-306
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Torulaspora delbrueckii S1, an endophyte isolated from apples, was used in the fermentation of apple vinegar to explore its influence on the flavor of apple vinegar. The volatile flavor substances and organic acids of apple vinegar co-fermented with T. delbrueckii S1 and Saccharomyces cerevisiae (experimental) and that fermented with S. cerevisiae (control) were detected by headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) and high performance liquid chromatography (HPLC), respectively, and their differences in flavor substances were compared through biometric analysis. Heatmap cluster analysis showed that T. delbrueckii S1 had no significant effect on the synthesis of volatile substances in apple vinegar, and the apple vinegars could be well distinguished by orthogonal partial least squares-discriminant analysis (OPLS-DA). The results of differential metabolites showed that phenethyl acetate, contributing to the typical apple aroma; and phenyl ethanol, benzaldehyde and benzyl alcohol, contributing to floral and fruity aromas, were more prominent in the experimental group, while ethyl caproate, ethyl decanoate and ethyl laurate, responsible for fruit and laurel oil-like aromas, were more prominent in the control group. The results of co-occurrence network analysis showed that T. delbrueckii S1 could enhance the transmissibility of volatile flavor compounds, and consequently increase the complexity of metabolites. In addition, the box plot of organic acids showed that T. delbrueckii S1 could increase the contents of L-lactic acid, L-malic acid and acetic acid. In this study, the effects of apple endophytic fungus T. delbrueckii S1 on the synthesis of flavor compounds in apple vinegar were analyzed, and it provided a basis for further utilization of this strain.
Effect of Yeast Co-culture on Phenols, Antioxidant Activity and Flavor Volatiles of Crown Pear Wine
CHEN Jiangkui, YIN Chunyan, ZHANG Xianzhong, YANG Mingjian
2023, 44(20):  343-349.  doi:10.7506/spkx1002-6630-20230221-195
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To enrich the flavor and enhance the quality of crown pear wine, Saccharomyces cerevisiae (Sc) and Torulaspora delbrueckii (Td) were selected for co-culture. Changes in the phenolic composition and antioxidant activity of crown pear wine were investigated during single and mixed yeast fermentation and the correlation between them was investigated. Besides, the organic acid and volatile compounds of the two wines were compared. The results showed that the contents of total polyphenols (TP) and total flavonoids (TF) in pear wine increased first and then decreased during fermentation, and so did the scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. Compared with pure Sc, the contents of TP and TF in the co-fermented wine increased significantly by 16.5% and 15.9%, respectively. The DPPH radical scavenging capacity significantly increased by 8.3% and the total acid content decreased by 10.05%, with malic acid being the major one. The predominant phenolic compounds in pear wine were arbutin, chlorogenic acid and catechin, whose contents changed in a complex manner during the fermentation process. The phenolic profiles of the two samples were different. Pearson correlation coefficients showed that there was a strongly positive correlation between the DPPH radical scavenging capacity and the contents of TP, arbutin and epicatechin (P < 0.01). The co-fermented wine had higher concentrations of volatile compounds, especially acetate esters contributing to fruity aroma, compared with that obtained with pure Sc. Overall, mixed fermentation of Sc with Td can improve the quality and flavor intensity of crown pear wine. This study provides a support for the deep-processing of crown pear.
Safety Detection
Rapid Machine Vision Method for Detection of Primary Dermatitis in Broiler Carcass
WU Jiangchun, WANG Huhu, XU Xinglian
2023, 44(20):  350-356.  doi:10.7506/spkx1002-6630-20221010-084
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A machine vision system was used to collect 948 three-dimensional images of chicken carcasses on the broiler slaughter line. This study aimed to develop a rapid method for the identification of primary dermatitis in chicken carcasses. The acquired images were preprocessed and segmented into 128 × 128 pixel pictures with grids. A total of 762 pictures of dermatitic skin and 775 pictures of normal skin were selected. A total of 24 feature values were extracted including third-order color moments, mean and variance of gray-level co-occurrence matrix features, Tamura texture features from the 1 537 pictures and the segmentation threshold and area of dermatitis region. Based on dimensionality reduction by principal component analysis (PCA), linear discriminant analysis model, quadratic discriminant analysis model, support vector machine, random forest, back propagation neural network (BPNN) and GoogLeNet models were established, and their classification performances were compared. Among these models, the GoogLeNet model was the most effective in classifying dermatitic skin samples with an overall accuracy of 90.5% and an average detection speed of 122.65 sheets per second. The prediction accuracy of the model for chicken carcasses with dermatitis was 100%, while that for qualified chicken carcasses was 90%.
Nondestructive Detection of Pear with Early-stage Core Browning Based on Empirical Mode Decomposition of Vibro-acoustic Signals
LI He, ZHAO Kang, ZHA Zhihua, WU Jie
2023, 44(20):  357-371.  doi:10.7506/spkx1002-6630-20230214-131
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In this study, a nondestructive vibro-acoustic setup was employed to acquire the vibro-acoustic signals of pear fruit. The signals were decomposed using the empirical mode decomposition (EMD). Different methods were used to suppress the end effect and mode mixing to achieve the optimal signal decomposition components. Then, the decomposition components of the vibro-acoustic signals were used as the input to construct a discriminant model based on convolution neural networks with spatial pyramid pool (CNN-SPP). The results showed that the improved slope-based method was better able to suppress the EMD end effect for the vibro-acoustic signals. The complementary complete ensemble empirical mode decomposition with adaptive noise (CCEEMDAN) method could exhibit better performance for suppressing mode mixing after end effect suppression. Thus, the obtained components were used as the input to construct a CCEEMDAN-CNN-SPP-based discriminant model. The overall classification accuracy of the model was 93.66% for pears with core browning, the discrimination accuracy was 94.44% for sub-healthy pears, and the misjudgment rate was 6.35% for diseased fruit. This improved the accuracy of vibro-acoustic identification of pears with early-stage mild disease. This study lays a foundation for the development of an online detection system for sub-healthy fruits in the future.
Determination of Triazine Residues in Fruits and Vegetables by Dual-Template Molecularly Imprinted Solid Phase Extraction Combined with High Performance Liquid Chromatography
LIU Jianhui, GONG Bichuan, HU Qiuhui, SU Anxiang, XU Hui, XIE Minhao, YANG Wenjian
2023, 44(20):  372-379.  doi:10.7506/spkx1002-6630-20221130-348
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A new dual-template molecularly imprinted polymer (MIPs) for efficient adsorption of triazines was prepared with cyromazine and melamine as template molecules, and its adsorption performance was evaluated for triazine residues in fruits and vegetables. Under the optimized condition of molar ratio of cyromazine to melamine = 3:2, the highest adsorption capacity of MIPs was achieved. The maximum adsorption capacity of MIPs at two specific binding sites 2.85 and 5.46 mg/g, and the binding constants were 26.688 and 80.775 mg/L, respectively. The adsorption process attained equilibrium in 100 minutes and showed a higher adsorption capacity than did non-imprinted polymers (NIPs). Molecular imprinting-based solid-phase extraction (MI-SPE) combined with high performance liquid chromatography (HPLC) was used for the measurement of four triazine residues including atrazine, prometryn, ametryn, and simetryn in cucumber, apple, and corn. The limit of detection of this method was 0.01–0.03 ng/mL, and the average recoveries of spiked samples at concentrations ranging from 0.1 to 0.5 μg/mL were 83.2%–102.3% (n = 3), with relative standard deviation (RSD) between 2.3% and 6.8%. The proposed method, therefore, is suitable for the trace detection of triazine residues in fruit and vegetable samples.
Fluorescence Resonance Energy Transfer between UiO-66-NH2 and Aptamer for Cadmium Ion Detection in Rice
CHENG Jing, QI Zhenli, XU Zhou, DING Li, CHENG Yunhui, CHEN Maolong
2023, 44(20):  380-386.  doi:10.7506/spkx1002-6630-20221003-021
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A simple, sensitive and accurate method for the detection of Cd2+ was established based on fluorescence resonance energy transfer to quench fluorescently labeled Cd2+ aptamers. Among three metal-organic framework materials (UiO-66-NH2, MIL-101(Cr), and ZIF-8), UiO-66-NH2, with larger positive charges, suitable particle size and stable dispersion in water, was selected as a fluorescence quencher. Fluorescence resonance energy transfer was generated by the interaction between positively charged UiO-66-NH2 and negatively charged aptamers to achieve fluorescence quenching. A fluorescent sensor for the detection of Cd2+ was constructed by using the specific interaction between Cd2+ and the aptamer to release the fluorescently labeled aptamer and restore the fluorescence. The fluorescence intensity of the sensor showed a good linear relationship with Cd2+ concentration in the range of 0.01–10 µmol/L. The biosensor had good selectivity and specificity for Cd2+, and could detect Cd2+ in actual samples. Most importantly, by adjusting the aptamer sequence, it is convenient to explore and construct fluorescent sensors for the detection of other heavy metal ions, so the sensor has wide applicability.
Determination of Organophosphorus Pesticide Residues in Vegetables by Carbon Aerogel Dispersive Solid Phase Extraction Combined with Gas Chromatography
CAO Jiangfei, XIE Chunsheng, LI Zhi’an, HUANG Xiangjin, WEI Shoulian
2023, 44(20):  387-392.  doi:10.7506/spkx1002-6630-20220928-311
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A method for the determination of sulfotep, dimethoate, fenitrothion, parathion, methidathion, triazophos and azinos residues in vegetables and fruits by dispersive solid phase extraction (SPE) using a carbon aerogel-based sorbent combined with gas chromatography (GC) was developed. Solvent type, extraction time, the amounts of sodium chloride and purifying agent, and purification time were optimized. The results showed that the optimum conditions were determined as follows: acetonitrile as extraction solvent, 15 mg of carbon aerogel, 2.0 g of sodium chloride, extraction time 6 min, and purification time of 0.5 min. Under these conditions, good linearity was observed for all analytes in the concentration range of 0.01–3.0 μg/mL, with correlation coefficients of 0.999 0–0.999 8, and the detection limit at a signal to noise ratio of 3 was 0.4–1.0 μg/kg. The mean recoveries of spiked samples at three concentrations were 85.5%–102%. The developed method is simple, rapid, low-cost and suitable for the determination of organophosphorus pesticide residues in fruit and vegetable samples.