Loading...

Table of Content

25 March 2022, Volume 43 Issue 6
Food Chemistry
Properties of Soybean Protein Peptide Aggregates and (–)-Epigallocatechin Gallate Composite Nanoparticles and Emulsion Stabilized with It
DONG Yabo, LAN Tian, FU Yuantao, SUN Shujing, LI Meng, JIANG Lianzhou, SUI Xiaonan, ZHANG Yan
2022, 43(6):  1-7.  doi:10.7506/spkx1002-6630-20210422-313
Asbtract ( 244 )   HTML ( 56)   PDF (2566KB) ( 148 )  
Related Articles | Metrics
In this paper, composite nanoparticles consisting of soybean peptide aggregates (SPA) and (-)-epigallocatechin gallate (EGCG) were successfully prepared by ultrasonic treatment and its particle size, zeta potential, fluorescence spectrum and X-ray diffraction pattern were measured. Furthermore, the droplet size and oxidation stability of emulsions stabilized with SPA or the composite nanoparticles were evaluated. The results showed that ultrasound and EGCG had a synergistic effect in reducing particle size. The nanoparticles with 0.80% (m/m) EGCG had the smallest particle size and the largest absolute value of zeta potential. After addition of EGCG, nanoparticles changed from a crystalline to an amorphous state, and its fluorescence intensity was quenched in a EGCG concentration-dependent manner. Compared with the SPA stabilized emulsion, the emulsifying activity, emulsion stability and oxidation stability of the emulsion stabilized with the composition nanoparticles were improved.
Effect of Hydroxyl Radical Oxidation on the Structure and Emulsifying Properties of Beef Myofibrillar Protein
MA Sili, YANG Bo, LI Yalei, LUO Ruiming, MA Xuhua
2022, 43(6):  8-16.  doi:10.7506/spkx1002-6630-20210324-299
Asbtract ( 180 )   HTML ( 36)   PDF (2927KB) ( 263 )  
Related Articles | Metrics
After different degrees of oxidation in the Fenton system, the changes in the structure and emulsification properties of beef myofibrillar proteins were investigated and the relationship between them were evaluated. The results showed that with increasing H2O2 concentrations from 0 to 20 mmol/L, the oxidation of myofibrillar protein became more serious, the carbonyl content, dimer tyrosine content and surface hydrophobicity increased gradually, and the contents of total sulfhydryl and free sulfhydryl groups decreased gradually; the percentage of α-helix exhibited a downward trend and the percentage of β-sheet showed an upward trend; solubility, emulsification activity and emulsion stability all tended to first increase and then decrease, while the opposite trend was observed for turbidity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that oxidation induced protein cross-linking. Correlation analysis found that the contents of carbonyl, sulfhydryl and dimer tyrosine, surface hydrophobicity and secondary structure indicators had significant correlations with solubility, turbidity and emulsification properties. In summary, the oxidation degree of myofibrillar protein increased gradually with increasing H2O2 concentration in the Fenton oxidation system, causing changes in its structure and emulsification properties.
Preparation and Stability of β-Acids-Lycopene/HP-β-CD Inclusion Complex
LI Wanrong, TIAN Bingren, XU Dan, WANG Jie, CHENG Jianhua, LIU Yumei
2022, 43(6):  17-26.  doi:10.7506/spkx1002-6630-20210324-298
Asbtract ( 181 )   HTML ( 31)   PDF (4508KB) ( 113 )  
Related Articles | Metrics
β-acids-lycopene/hydroxypropyl-β-cyclodextrin (HP-β-CD) inclusion complex was prepared by a grinding method, and its structure was characterized by ultraviolet/visible (UV-Vis) absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR). Then the stability of β-acids and lycopene in an aqueous solution of the inclusion complex was evaluated under light, thermal and acidic-alkaline conditions. The results showed that the inclusion complex was successfully prepared, which significantly increased the water solubility of β-acids and lycopene to 3.47 and 0.53 mg/mL, respectively. The inclusion complex could retain more than 80% of β-acids and 60% of lycopene after 16 days of storage in the dark compared to UV and natural light, and more than 70% of both compounds were retained in the inclusion complex held at 10–90 ℃ for 12 h. Under acidic condition (pH < 5), β-acids was crystallized, while acid-base conditions had no significant effect on lycopene. These results indicated that HP-β-CD inclusion had a positive effect on improving the photothermal stability of β-acids and lycopene, and it could be more suitable for neutral and alkaline foods.
Effect of Fenton Oxidation Treatment on Structural and Functional Properties of Myofibrillar Proteins in Esox lucius Muslce
DENG Xiaorong, LEI Yongdong, LIU Juan, LU Shiling, ZHANG Jian
2022, 43(6):  27-33.  doi:10.7506/spkx1002-6630-20210331-387
Asbtract ( 120 )   HTML ( 23)   PDF (2802KB) ( 52 )  
Related Articles | Metrics
The present study investigated the effects of different oxidation degrees (0, 1, 5, 10 and 20 mmol/L H2O2) induced by a Fenton oxidation system on the functional properties of myofibrillar proteins (MP) from Esox lucius muscle. Increasing oxidation degree caused an increase in carbonyl group content and turbidity and a significant decrease in protein solubility (P < 0.05). Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis revealed a greater degree of cross-linking and protein aggregation in oxidized MP. Fourier transform infrared spectroscopic (FTIR) analysis suggested that oxidation caused conformational changes in MP. The results of functional characterization indicated that moderate oxidation (1 and 5 mmol/L H2O2) substantially increased the foaming capacity of MP by 280% (P < 0.05) while having little effect on the emulsifying stability (which remained at above 90%). However, oxidation decreased the emulsifying properties of MP; the influence of moderate oxidation (1 and 5 mmol/L H2O2) was small, while excessive oxidation (> 10 mmol/L H2O2) led to a significant decrease in emulsifying capacity and emulsion stability. These results indicated that mild oxidation could improve the foaming capacity, and provide better functional properties of MP.
Impact of the Structure of Polyglycerol Fatty Acid Esters on the Stability and Functional Performance of Curcumin-Loaded Nanoemulsions
ZHANG Shangwei, YANG Jiguo, XU Xiaofei, REN Jie
2022, 43(6):  34-41.  doi:10.7506/spkx1002-6630-20210310-133
Asbtract ( 175 )   HTML ( 30)   PDF (3399KB) ( 130 )  
Related Articles | Metrics
The effects of the aliphatic chain length of polyglycerol fatty acid esters (PGFEs) on physicochemical characteristics, storage stability, antioxidant activity and antimicrobial activity of curcumin-loaded nanoemulsions were evaluated. It turned out that longer aliphatic chain of PGFEs increased the droplet size and decreased the zeta potential of nanoemulsions, but had little impact on the encapsulation efficiency of curcumin. Moreover, PGFE-stabilized nanoemulsions were stable for 28 days at 4 or 30 ℃, while the particle size of nanoemulsions drastically increased over time at 50 ℃, accompanied by rapid degradation of curcumin. Compared to other PGFEs, nanoemulsions formulated with polyglycerol capric acid esters (PGC) displayed greater thermal stability. Nanoemulsions stabilized by medium-chain PGFEs significantly (P < 0.05) enhanced the radical-scavenging activity of curcumin, and showed antimicrobial activity against Staphylococcus aureus and Escherichia coli. There was a synergistic inhibitory effect between PGFEs and curcumin.
Effect of β-Lactoglobulin on the Thermal Stability of Vitamin E
LI Meng, KANG Jiaxin, NING Xuenan, WEI Zikai, LIAO Minhe, JU Huanhuan, XIN Qiuyan, LIU Ning
2022, 43(6):  42-48.  doi:10.7506/spkx1002-6630-20201231-358
Asbtract ( 139 )   HTML ( 22)   PDF (3022KB) ( 107 )  
Related Articles | Metrics
In order to improve the thermal stability of vitamin E (VE) in ultra-high temperature sterilized (UHT) milk, a complex of β-lactoglobulin (β-LG) with VE was prepared. Turbidity, particle size, zeta potential, scanning electron microscopy, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), infrared spectroscopy and fluorescence spectroscopy were used to explore whether β-LG combined with VE. The degree of binding was further analyzed by bio-layer interferometry. The contents of VE in common fortified milk (with VE) and complex fortified milk (with β-LG/VE complex) before and after ultra-high temperature sterilization were determined by high performance liquid chromatography (HPLC) and the loss rate of VE was calculated to determine the effect of β-LG on the thermal stability of VE. The results showed that β-LG combined with VE to form a complex through hydrogen bonds and hydrophobic interaction, and that binding to β-LG reduced the aggregation of VE in aqueous solution and increased its solubility. Bio-layer interferometry corroborated the binding between β-LG and VE, and the binding constant was 7.493 × 10-2 mol/L. The loss rate of VE in complex fortified milk was significantly lower than that in common fortified milk, (4.01 ± 0.18)% versus (10.90 ± 0.17)% (P < 0.05). The above results showed that β-LG/VE could effectively improve the thermal stability of VE, which provides a theoretical basis for the development of vitamin fortified dairy products.
Effect of Addition of Soy Protein Isolate on the Gelation Properties of Low-salt Wooden Chicken Breast Meat Batter
ZHAO Zerun, XING Tong, ZHAO Xue, XU Xinglian
2022, 43(6):  49-56.  doi:10.7506/spkx1002-6630-20210417-242
Asbtract ( 181 )   HTML ( 43)   PDF (2150KB) ( 105 )  
Related Articles | Metrics
The purpose of this work is to study the effect of addition of soy protein isolate (SPI) at 0%, 1% and 2% on the gelation properties of low-salt and normal-salt (1% and 2%, respectively) wooden chicken breast meat batters. Normal chicken breast meat batter was set as a control. Textural properties, color characteristics, cooking loss, water distribution and secondary structure of heat-induced gels from chicken breast meat were measured. The results indicated that different NaCl contents had more significant effects on the heat-induced gel hardness and cooking loss of wooden breast meat than normal meat. No significant variation in gel harness was found between wooden chicken meat batter with 2% SPI and normal meat batter without added SPI (P > 0.05), whereas addition of 2% SPI caused a significant decrease in gel whiteness (P < 0.05). Meanwhile, the T22 relaxation time of immobile water of both wooden and normal meat batters was shorten (P < 0.05) by salt or SPI addition. Despite barely affecting protein secondary structure in normal meat, SPI led to conformational transformation of proteins in wooden chicken breast from an ordered (α-helix and β-sheet) to a disorder state (β-turn and random coil). In conclusion, addition of SPI can improve the textural properties and water-holding capacity of low- and normal-salt wooden breast meat batters by modifying protein structural properties and promoting water retention in heat-induced protein gels.
Preparation and Structural Characterization of Water-soluble Polysaccharide from Garlic Skin
JIANG Maoting, RAN Yanhong, LIU Na, HUANG Xuesong
2022, 43(6):  57-65.  doi:10.7506/spkx1002-6630-20210323-289
Asbtract ( 222 )   HTML ( 43)   PDF (4224KB) ( 136 )  
Related Articles | Metrics
A water-soluble polysaccharide from garlic skin (GSWSP) was extracted and purified by sequential water extraction and alcohol precipitation, DEAE-52 cellulose chromatography and Sephadex G-100 gel chromatography, and its primary, spatial, and mesoscopic structure of GSWSP were analyzed using chromatography, spectroscopy, and scanning electron microscopy (SEM). The results showed that the molecular mass of GSWSP was 2 969 Da, which was composed of fructose, glucose, galacturonic acid, galactose, mannose, arabinose and rhamnose with a molar ratio of 81.8:17.6:15.6:14.5:6.5:4.2:1. Six sugar residues, →1)-β-D-Fruf-(2→; →1,6)-β-D-Fruf-(2→; →6)-β-D-Fruf-(2→; β-D-Fruf-(2→; α-D-Glc-(1→; and β-D-Gal-(1→, and three groups, β-D-GalA, α-D-Man and α-D-Ara, were found in GSWSP. GSWSP exhibited a three-strand helical structure in solution. Its solid powder existed in a crystalline state. Spherical conformation of GSWSP was observed under atomic force microscope, and it showed an irregular broken lumpy structure as observed under SEM. In summary, GSWSP can be used as a homogeneous polyfructan in foods and cosmetics.
Bioengineering
High-level Expression of an Engineered Thermostable Xylanase B from Thermotoga maritima and Its Application in Beer Brewing
LIU Xueqiang, JIANG Zhengqiang, YU Jing, MA Junwen, YANG Hang, YAN Qiaojuan
2022, 43(6):  66-73.  doi:10.7506/spkx1002-6630-20210504-021
Asbtract ( 174 )   HTML ( 25)   PDF (3451KB) ( 127 )  
Related Articles | Metrics
The extremely thermostable xylanase B (TmXynB) from T. maritima was successfully engineered by directed evolution. After two steps of screening, one mutant (mTmXynB) with high specific activity in acidic and high-temperature conditions was obtained. The optimal pH and temperature of mTmXynB were 5.5 and 90 ℃, respectively, which were 0.5 and 10 ℃ lower than those of the wild-type enzyme, respectively. The specific activity toward wheat arabinoxylan was increased from 529 (TmXynB) to 1 565 U/mg (mTmXynB). Three amino acid residues were substituted in mTmXynB, namely Asn91Ser, Trp129Arg, and Arg143Glu. Arg143Glu improved the acid tolerance by changing the charge distribution on part of the protein surface. Trp129Arg decreased the optimal temperature by destroying the hydrophobic platform. Asn91Ser improved the enzyme activity by changing the conformation of the substrate-binding site Trp89. mTmXynB was then successfully expressed in Pichia pastoris, and after 180 h high-cell density fermentation, the maximal xylanase activity of 18 000 U/mL was obtained. Furthermore, TmXynB and mTmXynB were separately added in the mashing process. Under the standard mashing conditions, the addition of mTmXynB at 150 U/g of malt decreased filtration time by 45% and viscosity by 8.7%. In contrast, the addition of TmXynB at 600 U/g of malt decreased filtration time by 39% and viscosity by 8.1%. Thus, the engineered mTmXynB may be a promising candidate for the brewing industry owing to its favorable properties.
Synergistic Enzymatic Degradation of Colloidal Chitin and Its Mechanism
WU Hao, LIU Jiali, YANG Jingwen, HU Xueqin, ZHANG Hongbin
2022, 43(6):  74-80.  doi:10.7506/spkx1002-6630-20210205-106
Asbtract ( 166 )   HTML ( 23)   PDF (2925KB) ( 80 )  
Related Articles | Metrics
In this study, a synergistic catalytic system of chitinase (ChiA) and β-N-acetylhexosaminase HJ5N that can degrade colloidal chitin to prepare N-acetylglucosamine (GlcNAc) in one-step reaction was established. The effects of different factors on the catalytic efficiency and the mechanism of the synergistic action of the enzymes were discussed. The results showed that the optimum reaction conditions were 30 ℃, pH 6 and concentration ratio ChiA to HJ5N of 2:1. Under these conditions, 17.55 mg/mL of GlcNAc was produced with a yield of 58% when 90 g/L of (containing 30.3 g/L of colloidal chitin) was used as the substrate. HJ5N could ensure quick conversion of the intermediate product (GlcNAc)2 into GlcNAc, thus removing the inhibitory effect of (GlcNAc)2 on ChiA and ultimately allowing the efficient degradation of colloidal chitin into GlcNAc. This study provides an effective strategy for the industrial application of enzymatic degradation of colloidal chitin to prepare N-acetylglucosamine.
Construction of Escherichia coli Chassis for Efficient Production of L-Homoserine
ZHANG Yu, XIA Li, LIN Beibei, ZHANG Wenjie, XU Haoran, ZHANG Chenglin
2022, 43(6):  81-88.  doi:10.7506/spkx1002-6630-20210220-219
Asbtract ( 232 )   HTML ( 35)   PDF (3612KB) ( 144 )  
Related Articles | Metrics
Nutrients such as L-threonine need to be added during the fermentation of L-homoserine by auxotrophic strains. In this study, a non-auxotrophic Escherichia coli chassis for the high-yield production of L-homoserine was constructed. The expression of thrB and thrC were down-regulated to attenuate the degradation of L-homoserine; then the overexpression of thrA, ppc and pntAB was performed to reinforce the synthetic flux and improve precursor supply and NADPH generation; finally, rhtA was overexpressed to elevate L-homoserine efflux. After 48 h fermentation in a 5 L fermenter, the constructed strain H-10 produced 52.1 g/L of L-homoserine with a percentage transformation of glucose of 43%, which is higher than the values reported in the literature.
Isolation and Identification of Predominant Fungi in Fuzhuan Tea and Their Application for Fermentation of Low-Grade Green Tea
ZHAO Hongpeng, HUANG Sichen, SHI Lijuan, WANG Yiqi, REN Dabing, HU Yongdan, YI Lunzhao
2022, 43(6):  89-95.  doi:10.7506/spkx1002-6630-20210415-211
Asbtract ( 191 )   HTML ( 27)   PDF (3376KB) ( 110 )  
Related Articles | Metrics
The dominant fungi in Fuzhuan tea produced in Hunan were isolated and identified by morphological analysis and comparative analysis of internal transcribed spacer (ITS) sequences. Then, single-strain fermentation of low-grade Yunnan large-leafed green tea was carried out using the isolated fungi, and changes in the contents of the main components of green tea were analyzed before and after fermentation. The results showed that four dominant strains named as J1–J4 were isolated from Fuzhuan tea. J1 was identified as Aspergillus chevalieri, and J2, J3 and J4 as Aspergillus cristatus. The contents of tea polyphenols and total flavonoids in green tea significantly fell after fermentation, whereas the content of theabrownin increased significantly. The total alkaloid content significantly increased after fermentation with A. chevalieri, but significantly decreased after fermentation with A. cristatus. The contents of catechin components varied significantly after fermentation; ester catechin content decreased significantly, while the contents of three non-ester catechins (epicatechin, gallocatechin, and epigallocatechin) increased significantly. Theaflavin content was significantly decreased by strains J1, J2 and J3 but significantly increased by strain J4. The contents of amino acids also changed significantly. The results of this study can provide a theoretical basis for the development of high-value products from low-grade Yunnan large-leafed green tea.
Effect of an Outer Membrane Protein of Lactobacillus salivarius on the Adhesion of Staphylococcus aureus
YANG Le, YANG Liu, LI Yue, LIU Jinqiu, REN Dayong
2022, 43(6):  96-103.  doi:10.7506/spkx1002-6630-20210416-232
Asbtract ( 151 )   HTML ( 33)   PDF (5822KB) ( 60 )  
Related Articles | Metrics
This study aimed to evaluate the adhesion of the elongation factor G (EF-G) from Lactobacillus salivarius to Staphylococcus aureus through gene recombination and gene knockout. The effect of prokaryotically expressed protein on the adhesion of S. aureus was examined. The results showed that EF-G increased the in vitro adhesion rate of S. aureus by 43% compared to the control group. As demonstrated by the ef-g gene knockout test using a mucin adhesion model method and fluorescent labeling, knockout of the ef-g gene did not affect colonization of the intestinal tract by L. salivarius Δef-g, and L. salivarius Δef-g reduced the in vitro and in vivo adhesion rate of S. aureus by 40% and 20%, respectively. These findings were validated by scanning electron microscopy (SEM). Therefore, we concluded that EF-G plays a role in promoting the adhesion of S. aureus, which provides a scientific basis for the application of probiotics.
Effect of Coreopsis tinctoria Essential Oil on Tyramine Production and Related Gene Expression in Enterococcus hirae
LI Yazhuo, HUANG Yali, YU Honghong, WANG Jingyun, LU Shiling
2022, 43(6):  104-111.  doi:10.7506/spkx1002-6630-20210403-043
Asbtract ( 138 )   HTML ( 21)   PDF (2535KB) ( 45 )  
Related Articles | Metrics
The aim of this study was to investigate the effect of different concentrations of Coreopsis tinctoria essential oil on tyramine production by Enterococcus hirae N47. Reverse transcription quantitative real-time polymerase chain reaction (real-time PCR) was used to analyze the expression of the genes involved in the tyrosine decarboxylase (TDC) pathway in E. hirae treated with C. tinctoria essential oil. High performance liquid chromatography (HPLC) was used to detect tyramine. The changes in pH, total viable count and tyramine accumulation in smoked horse sausage with different concentrations of C. tinctoria essential oil inoculated with E. hirae were evaluated during the 28-day fermentation period. The results showed that for both the pure culture of E. hirae and smoked horse sausage, C. tinctoria essential oil significantly reduced tyramine accumulation by inhibiting the growth of microorganisms and the expression of the tyr DC and tyr P genes in the tyrosine decarboxylation pathway (P < 0.05). Tyramine contents in smoked horse sausage with C. tinctoria essential oil at the minimal inhibitory concentration (MIC) and 1/2 MIC were 78.52 and 45.83 mg/kg, respectively, which were 64.72% and 79.41% lower than that in the control group (not added with C. tinctoria essential oil, inoculated with E. hirae), respectively.
Separation and Characterization of Polyphenol Oxidase from Unfermented and Fermented Liupao Tea
LONG Junyao, HUANG Li, XIA Ning, TENG Jianwen, WEI Baoyao, HU Peiran
2022, 43(6):  112-117.  doi:10.7506/spkx1002-6630-20210512-129
Asbtract ( 161 )   HTML ( 21)   PDF (2703KB) ( 68 )  
Related Articles | Metrics
In order to explore the source and activity of polyphenol oxidase (PPO) in the fermentation process of Liupao tea, PPO from unfermented and fermented Liupao tea was extracted by using buffer solutions at different pHs and different types and amounts of protective agents at different liquid-to-solid ratios, and was purified through sequential (NH4)2SO4 precipitation, dialysis, and Sephadex G-100 gel filtration chromatography. The results showed that two PPO isozymes with molecular masses of 59 (PPO1) and 70 kDa (PPO2) were purified from Liupao tea. PPO1 may be derived from tea leaves, and PPO2 may be produced by microbial fermentation. When catechol was used as the substrate, the optimum pHs of PPO1 and PPO2 were 6.5 and 6.0, and the optimum temperatures were 40 and 35 ℃, respectively. The thermal stability of PPO1 was better than that of PPO2, although both were almost completely inactivated after heating at 90 ℃ for 5 min. Our data indicated that new isozymes produced during the fermentation of Liubao tea can synergistically improve the quality of dark tea, which will provide a theoretical basis for the control of dark tea processing conditions and the study of polyphenol oxidase of dark tea.
Oxidative Polymerization of Dihydromyricetin Catalyzed by Laccase
LIU Xiaoling, HE Chengyun, CHEN Chungang, SUN Junliang, LIU Benguo
2022, 43(6):  118-124.  doi:10.7506/spkx1002-6630-20210210-160
Asbtract ( 146 )   HTML ( 21)   PDF (3474KB) ( 56 )  
Related Articles | Metrics
The effects of laccase catalysis conditions on the color, α-glucosidase inhibitory activity and antioxidant activity of dihydromyricetin derivatives were systematically investigated, and the structures of the derivatives were also characterized. It was found that the oxidative polymerization of dihydromyricetin was achieved by using laccase. Laccase concentration, pH, reaction time and temperature had regular effects on the color of the derivatives. The α-glucosidase inhibitory activity of the derivatives was significantly higher than that of dihydromyricetin, with half-maximal inhibitory concentration (IC50) of 6.2 versus 85.95 μg/mL, but the 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2’-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) radical cation scavenging capacities were inferior to those of dihydromyricetin. Spectral analysis indicated that laccase catalyzed the oxidation of the phenolic hydroxyl groups of dihydromyricetin, consequently leading to the polymerization of dihydromyricetin by ether bonding. These results can promote the application of dihydromyricetin in foods, and the development of new functional foods.
Cytotoxicity of Formic Acid to Saccharomyces cerevisiae
ZENG Lingjie, HUANG Jinxiang, FENG Pixue, AN Jiaxing, SI Zaiyong, LONG Xiufeng, WU Shihua, YI Yi
2022, 43(6):  125-131.  doi:10.7506/spkx1002-6630-20210217-176
Asbtract ( 188 )   HTML ( 18)   PDF (3214KB) ( 85 )  
Related Articles | Metrics
To evaluate the toxic effect of formic acid on Saccharomyces cerevisiae GGSF16, the influence of fomic acid at different concentrations on the growth and metabolism of S. cerevisiae were determined. The results showed that formic acid at 1.8 g/L significantly inhibited the growth of yeast cells, reduced ethanol production, and extended cell fermentation cycle. The contents of extracellular nucleic acid, protein and malondialdehyde, and the activity of intracellular hexokinase in the treated cells were 1.4, 1.67, 5.3 and 3.95 (P < 0.05) times as high as those in the control group, respectively. Scanning electron microscopic (SEM) images showed that a large number of wrinkles and cavities appeared on the surface of intact and smooth yeast cells, and that and cell-cell adhesion was observed. Fourier transform infrared spectra demonstrated that formic acid could destroy the cell wall and increase the permeability of the cell membrane, thus leading to the leakage of cellular contents and cell death finally.
Host-derived Proteomics Analysis of Exosomes Secreted by Intestinal Epithelial Cells Infected with Salmonella typhimurium
ZHANG Biao, LU Juan’e, HAN Wenying, LIU Suke, WU Tao, RUAN Haihua
2022, 43(6):  132-140.  doi:10.7506/spkx1002-6630-20210217-174
Asbtract ( 158 )   HTML ( 25)   PDF (4267KB) ( 85 )  
Related Articles | Metrics
In our present study, the human intestinal epithelial cell line Henle-407 was used as a host model. Label-free quantitative proteomics was used to explore the change of host proteome in exosomes secreted by host cells infected with S. typhimurium. A total of 2 490 proteins were quantitated, including 321 differentially expressed proteins (DEPs) in exosomes from S. typhimurium-infected and uninfected Henle-407 cells. Seven DEPs were common to both, three of which were up-regulated and the rest were down-regulated. The remaining 314 DEPs were not shared between them, nine of which were specifically present in the exosomes from S. typhimurium-infected Henle-407 cells, while 305 were missing. Gene Ontology (GO) analysis indicated that the DEPs were mainly distributed in organelles and membrane, involved in metabolism and biological regulation processes, and related to molecular functions such as binding, catalytic activity and transport. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the DEPs were associated with 17 specific KEGG pathways. By comparing the host proteomics data of exosomes from S. typhimurium-infected and uninfected Henle-407 cells, it was found that infected S. typhimurium led to a sharp reduction in the amount of host cell-derived proteins in exosomes in addition to altering the expression of a few shared DEPs. Considering that exosome have been reported as double-layered membrane vesicles with a particle size of 30–150 nm, we speculated that in a limited space, Salmonella infection may inhibit the transport of host cell proteins to exosomes by unknown mechanisms. The specific proteins and lipopolysaccharides of Salmonella enter exosomes and promote the infection and spread of Salmonella in host cells by changing the susceptibility of neighboring cells to Salmonella.
Effect of the Inhibition of PDIDSM_85260 and PDIDSM_08010 Expression by RNA Interference on the Biotransformation of Limonene to α-Terpineol
ZHANG Lulu, FAN Gang, LI Xiao, REN Jingnan, PAN Siyi, HUANG Wen, HE Jin
2022, 43(6):  141-148.  doi:10.7506/spkx1002-6630-20210115-171
Asbtract ( 105 )   HTML ( 20)   PDF (3171KB) ( 47 )  
Related Articles | Metrics
Our previous results have shown that some genes such as PDIDSM_85260 and PDIDSM_08010 may be partly responsible for limonene biotransformation to α-terpineol as determined by analysis of genomic and transcriptomic data, protein separation and purification, and mass spectrometry. In order to explore the biological functions of the genes, RNA interference (RNAi) vectors for PDIDSM_85260 and PDIDSM_08010 were constructed and transformed into Penicillium digitatum DSM62840 by Agrobacterium tumefaciens-mediated transformation. RANi strains were obtained by a series of experiments, and the functions of the two genes were analyzed in P. digitatum DSM62840. It was found that the amount of α-terpineol produced by the silenced transformants obviously decreased compared to the wild-type strain, suggesting that PDIDSM_85260 and PDIDSM_08010 may participate in limonene biotransformation to α-terpineol.
Tolerance of Lactobacillus to Organic Acids and Their Fermentation Performances in Fruit and Vegetable Juices
XIE Han, LIU Ruishan, ZHANG Xiaojuan, FENG Jingyi, CHAI Lijuan, LU Zhenming, SHI Jinsong, XU Zhenghong
2022, 43(6):  149-157.  doi:10.7506/spkx1002-6630-20210112-119
Asbtract ( 215 )   HTML ( 24)   PDF (4698KB) ( 173 )  
Related Articles | Metrics
In this study, the effects of different concentrations and types of organic acids in the medium on the fermentation characteristics of three high-performance strains of Lactobacillus isolated from fermented grains for vinegar brewing were investigated, and their fermentation performances in 12 typical fruit and vegetable juices were compared. The results showed that L. rhamnosus LR-S, L. plantarum LP-D and L. plantarum LP-F had good tolerance to malic acid, citric acid and tartaric acid, respectively, and were consequently superior in fermenting fruit and vegetable juices containing each of these organic acids as the major one. Sequential inoculation of two strains was suitable for raw materials with complicated organic acid composition such as mulberry juice. These results prove the necessity of developing targeted stress-resistant strains according to the characteristics of fruits and vegetables, and that sequential inoculation is an effective method to improve the fermentation performance of lactic acid bacteria on fruits and vegetables.
Purification and Characterization of Esterase from Liver of Blue Round Scads (Decapterus maruadsi)
SUN Lechang, WEN Jiaxin, DU Han, LIN Yichen, LIU Guangming, CAO Minjie
2022, 43(6):  158-164.  doi:10.7506/spkx1002-6630-20210201-014
Asbtract ( 172 )   HTML ( 23)   PDF (2859KB) ( 43 )  
Related Articles | Metrics
In this study, a novel esterase was purified from the liver of blue round scads via ammonium sulfate fractionation followed by a series of column chromatographies on Q-Sepharose, Q-HP, Phenyl Fast Flow and Superdex G75 with a recovery of 0.69% and 1 150-fold purification factor. The esterase was a monomer with a molecular mass of 61.18 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Superdex G75 column chromatography. Peptide mass fingerprint analysis showed that the peptides showed a similarity of 100% to the predicted fatty acyl-CoA hydrolase precursor from Takifugu rubripes with 14 amino acid residues. The esterase showed an optimal activity at pH 8.0 and 50 ℃, and was comparably stable at pH 6.0–10.0 and 4–40 ℃. The metal ions K+, Zn2+, Cu2+, Al3+ and Fe2+ strongly suppressed the esterase activity while Ba2+, Ca2+, Mn2+, Co2+ and Mg2+ showed obvious activation effect on the enzyme’s activity. Moreover, the esterase exhibited strong tolerance against methanol, ethanol, acetone and isopropanol, as well as salt. Interestingly, the esterase preferably hydrolyzed esters with short carbon chain in aqueous solution, and exhibited hydrolytic activity toward long-chain esters in an emulsion system but not in aqueous solution. The results indicated that the esterase has both esterase and lipase activity.
Effect of Lactic Acid Bacterial Fermentation on Protein Degradation and Biological Activity of Peptides in Rubing Cheese
WEI Guangqiang, WANG Daodian, YANG Caiyan, WAN Changjiang, HUANG Aixiang
2022, 43(6):  165-173.  doi:10.7506/spkx1002-6630-20210119-206
Asbtract ( 155 )   HTML ( 27)   PDF (3215KB) ( 62 )  
Related Articles | Metrics
Rubing cheese was manufactured by lactic acid bacterial fermentation or traditional direct acidification. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and liquid chromatography-mass spectrometry (LC-MS) were used to determine protein degradation and free amino acid contents in rubing cheese, respectively. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to identify peptides in rubing cheese. The biological activity of the hydrolysate of rubing cheese was characterized by in vitro antioxidant activity, α-glucosidase-inhibiting activity and angiotensin-converting enzyme (ACE)-inhibiting activity. According to the results of SDS-PAGE, both lactic acid bacterial fermentation and direct acidification could promote the degradation of milk proteins. Lactic acid bacterial fermentation caused a higher degree of degradation of whey protein, promoting the release of free amino acids. From the fermented rubing cheese and the directly acidified one, 23 and 13 potential ACE inhibitory peptides, six and four antioxidant peptides and five and one antiglycemic peptides were identified, respectively. Furthermore, lactic acid bacterial fermentation significantly improved the α-glucosidase-inhibiting activity and ACE-inhibiting activity of rubing cheese peptides (P < 0.05). The half-maximum inhibitory concentration (IC50) values of the fraction separated by ultrafiltration with a molecular mass of less than 3 kDa for α-glucosidase and ACE inhibitory activity were 1.250 and 0.416 mg/mL, respectively. In conclusion, lactic acid bacterial fermentation promotes protein degradation to release biologically active peptides and produce free amino acids, enhancing the biological value of rubing cheese.
Salt-Reducing and Umami-Enhancing Effect of Lactobacillus plantarum on Dry Cured Mackerel
LIANG Jinxin, CHEN Xiaohong, LI Shan, YANG Juan, ZHAO Wenhong, BAI Weidong
2022, 43(6):  174-180.  doi:10.7506/spkx1002-6630-20210203-065
Asbtract ( 184 )   HTML ( 23)   PDF (2028KB) ( 61 )  
Related Articles | Metrics
In this study, Lactobacillus plantarum was used as a partial substitute for sodium salt to produce salt-reduced, umami-enhanced dry-cured mackerel. Through sensory evaluation and comparative analysis of taste substances, it was found that the salty, umami and kokumi taste of the product with a substitution level of 50% was significantly better than that of control groups 1 (with 4% sodium salt) and 2 (with 2% sodium salt) (P < 0.05), indicating that L. plantarum could produce a large amount of umami and kokumi substances as well as salty substances or salty-enhancing substances to replace sodium salt. Moreover, the proportions of umami amino acids and taste-active peptides with molecular mass less than 1 kDa in the sample with L. plantarum were significantly higher than those in the control groups (P < 0.05). These substances could not only have umami and kokumi taste, but also enhance salty taste. In addition, the water activity and pH were significantly lower than those of the control groups (P < 0.05), which could be beneficial for the preservation of dry-cured mackerel, but there was no significant difference in color difference when compared to the control groups (P > 0.05), indicating that the appearance quality of the product was not affected by L. plantarum. The results showed that the addition of L. plantarum could not only reduce the addition of sodium salt in dry-cured mackerel, but also increase its umami and kokumi taste.
Effects of Different Carbon Sources on Decolorization and Degradation of Malachite Green by Klebsiella pneumoniae WA-1
TIAN Xiaoli, LI Chunsheng, CHEN Shengjun, XUE Yong, DENG Jianchao, PAN Chuang, WANG Yueqi
2022, 43(6):  181-188.  doi:10.7506/spkx1002-6630-20210115-166
Asbtract ( 110 )   HTML ( 18)   PDF (3413KB) ( 36 )  
Related Articles | Metrics
In this study, a strain with strong ability to decolorize and degrade malachite green was isolated from a malachite green-contaminated aquaculture pond by the color-changing zone method. By 16S rDNA sequence alignment and phylogenetic tree analysis, as well as using the microbial identification system VITEK 2, the strain was identified as Klebsiella pneumoniae and named as WA-1. The effects of different carbon sources on decolorization and degradation of malachite green by WA-1 were studied by spectrophotometry and KBH4 reduction-high performance liquid chromatography with fluorescence detection (HPLC-FLD). The results showed that this strain potently decolorized and degraded malachite green in the salt medium. The decolorization rate of malachite green at 5–40 mg/L was increased to approximately 100% after the addition of carbon sources including glucose, galactose, and sucrose, while the degradation rate was significantly reduced, especially at 5 mg/L. Malachite green was reduced to leucomalachite green by malachite green reductase outside the cells, which could enter the cells through active transport for decolorization and degradation. The mechanism of the effect of different carbon sources on the decolorization and degradation of malachite green was also revealed. The results of this study provide an important idea to reveal the mechanism of malachite green degradation by K. pneumoniae WA-1, and also provide an important theoretical basis for the application of malachite green degradation in the future.
Function of Penicillium digitatum V-ATPase Subunit H Protein
YAN Deng, PENG Litao, LI Jie, YANG Shuzhen
2022, 43(6):  189-194.  doi:10.7506/spkx1002-6630-20210218-194
Asbtract ( 166 )   HTML ( 17)   PDF (3136KB) ( 59 )  
Related Articles | Metrics
Objective: This work aims to study the physiological function of V-ATPase membrane subunit H (VMAH) protein in the growth of the citrus green mold fungus Penicillium digitatum and to evaluate its feasibility as a target of anti-citrus green mold drugs through gene interference and overexpression. Methods: The effect of silencing and overexpression of the VMAH gene was investigated on the growth characteristics of P. digitatum cells under normal and stress conditions, as measured by mycelial growth and spore germination. Results: Under normal growth conditions, VMAH silencing significantly inhibited the growth of P. digitatum mycelia, while VMAH overexpression showed a significant promoting effect. Under different pH environments, VMAH silencing significantly inhibited the growth of P. digitatum hyphae, especially under acidic (pH lower than 2) and alkaline (pH higher than 8) conditions, while overexpression of the VMAH gene promoted mycelial growth to a certain extent, especially at pH 6. Compared with the wild-type strain, silencing of the VMAH gene increased the sensitivity to the stress of extracellular Ca2+, Cu2+, Fe2+ and other metal ions and to proton pump inhibitor fungicides, especially the V-ATPase specific inhibitor bafilomycin A1, while VMAH overexpression significantly reduced the sensitivity to proton pump inhibitor fungicides. Conclusion: VMAH plays an important role in the growth of P. digitatum and is a potential target for the development of low-resistant postharvest citrus fungicides.
Purification and Identification of Dipeptidyl Peptidase IV Inhibitory Peptide from Sturgeon Skin Collagen
YIN Jian, WU Ruiyun, HU Jinrong, LI Pinglan
2022, 43(6):  195-203.  doi:10.7506/spkx1002-6630-20210131-374
Asbtract ( 193 )   HTML ( 55)   PDF (3591KB) ( 91 )  
Related Articles | Metrics
In order to prepare dipeptidyl peptidase IV (DPP-IV) inhibitory peptide, sturgeon skin collagen was hydrolyzed by protease. A combination of one-factor-at-a-time method and response surface methodology was used optimize the preparation conditions based on percentage of DPP-IV inhibition. The optimal enzymatic hydrolysis conditions were determined as follows: temperature 50 ℃, solid-to-liquid ratio 1:100 (g/mL), pH 6.12, enzyme dosage 10 170.35 U/g, and enzymatic hydrolysis time 12.12 h. The hydrolysate prepared under the optimized conditions was separated and purified by sequential ultrafiltration, gel filtration chromatography and reverse-phase high performance liquid chromatography (RP-HPLC). As identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS), the amino acid composition of the purified peptide with DPP-IV inhibitory activity was GPSGLDGAK, and its half-maximum inhibitory concentration (IC50) value was (61.27 ± 1.16) μmol/L. The results of this study can provide a reference for the production of new bioactive components from sturgeon skin.
Screening and Application of Aspergillus oryzae in Koji-making for Manufacturing of Fermented Watermelon-Soybean Paste
SUN Xiaohan, JIANG Xuewei, XIAO Zhiyu, OU Dechong, LI Kai, ZHOU Hui, FANG Qinjun
2022, 43(6):  204-211.  doi:10.7506/spkx1002-6630-20210203-059
Asbtract ( 215 )   HTML ( 30)   PDF (3220KB) ( 124 )  
Related Articles | Metrics
A strain with high amylase activity, designated as CS3.04, and another strain with high protease activity, designated as CS3.22, were isolated from koji for fermented soybean paste by the Oxford-cup double-layer plate method. Both strains were identified as Aspergillus oryzae by morphological characterization and internal transcribed spacer (ITS) rRNA sequence analysis. The two strains were used to make single-strain and mixed-strain koji for the manufacturing of fermented watermelon-soybean paste. Commercial A. oryzae was served as the control. The results showed that physicochemical indexes of the fermented product exhibited a consistent trend with fermentation time. The contents of reducing sugar and ammonia nitrogen in the mixed-strain fermented product were the highest, which were 107.37 and 6.76 g/kg and increased by 11.02% and 5.56% compared with that fermented by commercial A. oryzae, respectively. The qualitative and quantitative analysis of volatile flavor compounds was performed using liquid-liquid extraction and gas chromatography-mass spectrometry (GC-MS). It was found that the mixed-strain fermentation was superior to the single-strain fermentations in producing aldehydes, alcohols, ketones and short-chain esters, while fermentation with CS3.04 alone was more conducive to the production of acids and phenols. Moreover, the mixed-strain fermentation resulted in higher overall sensory score and better aroma and taste. We concluded that the mixed-strain fermentation improves the quality of fermented watermelon-soybean paste through the complementary effect between the enzymes of strains CS3.04 and CS3.22.
Effect of Solid-state Fermentation on Antioxidant Properties of Wheat Bran and Sensory Quality of Whole Wheat Bread
PEI Fei, DU Yifei, SUN Lei, LI Wen, FANG Yong, HU Qiuhui
2022, 43(6):  212-220.  doi:10.7506/spkx1002-6630-20210712-121
Asbtract ( 246 )   HTML ( 39)   PDF (3377KB) ( 129 )  
Related Articles | Metrics
Solid-state fermented wheat bran with Lactobacillus plantarum LB-1 and Saccharomyces cerevisiae was used to prepare whole wheat bread. The antioxidant properties of fermented bran and the sensory quality of whole wheat bread such as color, specific volume, texture, flavor and mouthfeel were analyzed. The results showed that the contents of total free amino acids, soluble protein, soluble polyphenols and soluble arabinoxylan in wheat bran increased by 1.44, 1.82, 2.67 and 2.68 times after 36 h mixed culture fermentation, respectively. The total reducing power, 1,1-dipheny1-2-picryl-hydrazyl (DPPH) radical and superoxide anion radical scavenging capacity increased by 1.88, 1.42 and 3.1 times, respectively. The L* values of whole wheat bread crumb and crust with fermented bran decreased significantly as compared to those with unfermented bran. Moreover, addition of bran fermented for 36 h increased bran bread specific volume by 1.24 times, decreased significantly hardness, gumminess and chewiness, and cohesiveness and elasticity increased significantly, resulting in a more soft and palatable mouthfeel. In addition, solid-state fermentation of wheat bran produced 15 new volatile flavor compounds, and increased the contents of acetic acid and ethanol significantly, thus enhancing the flavor characteristics of whole wheat bread. The sensory score of whole wheat bread with bran fermented for 36 h was the highest. In conclusion, 36 h solid-state fermentation by Lactobacillus LB-1 and yeast effectively enhances the antioxidant activity in vitro of wheat bran, slows down the aging of starch in whole wheat bread and consequently improves texture properties including viscoelasticity as well as sensory attributes such as color, flavor and taste, and thus it has great application potential.
Label-free Quantitative Proteomics Analysis of Developing Winter Jujube Fruit
TIAN Yan, HOU Zhaohua
2022, 43(6):  221-228.  doi:10.7506/spkx1002-6630-20210420-292
Asbtract ( 167 )   HTML ( 26)   PDF (3454KB) ( 57 )  
Related Articles | Metrics
In this work, the proteomes of winter jujube at different ripening stages were studied, and the differentially expressed proteins (DEPs) and their functions were analyzed in order to provide a theoretical basis for understanding the mechanism of the maturation and development of winter jujube. Samples of Zhanhua winter jujube at 55 days (young fruit), 76 days (enlarging), 96 days (white mature) and 116 days (crisp ripe) after flowering were collected and analyzed by label-free quantitative proteomics. Compared with the previous stage, DEPs were obtained for each stage and analyzed using bioinformatics tools including Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. The results showed that a total of 2 107 proteins were identified and 1 986 proteins were quantified. Compared with the previous stage, 96, 185 and 138 proteins were differentially expressed in fruits at the enlarging, white mature and crisp ripe stages, respectively. GO annotation showed that the DEPs were mainly enriched in biological processes such as single biological cell process, single biological metabolic process, chemical response, and pressure response. KEGG metabolic pathway analysis showed that the DEPs were significantly enriched in photosynthesis, flavonoid biosynthesis, limonene and pinene degradation, phenylpropanol biosynthesis, glyoxylic acid and dicarboxylic acid metabolism, and ribosome biosynthesis. We concluded that there are significant differences in the proteome of winter jujube fruits at different developmental stages, and that the differentially expressed proteins are mainly involved in energy metabolism, genetic information processing and biosynthesis of other secondary metabolites.
Evolutionary Relationship, Enzyme Activities and Antibiotic Resistance of Bacillus Isolated from Pixian Broad Bean Paste
LUO Jing, DONG Ling, ZHAO Chi, LIU Yuying, GUO Yunjian, LI Lu, LI Yanlin, CHEN Wang, YANG Guohua, YANG Yong, LI Zhihua, ZHU Yongqing
2022, 43(6):  229-235.  doi:10.7506/spkx1002-6630-20210208-133
Asbtract ( 151 )   HTML ( 28)   PDF (2322KB) ( 90 )  
Related Articles | Metrics
In this study, the pure culture method combined with metagenomic analysis was used to investigate the evolutionary relationship of 66 strains of Bacillus isolated from Pixian broad bean paste. The enzyme activities and antibiotic resistance of the selected representative strains were further analyzed. Totally 24 Bacillus strains were identified by metagenomics and were classified into 13 species according to full-length 16S rDNA gene sequences. As the salt content rose, the protease-producing and amylase-producing abilities of the 29 representative strains decreased. All?the strains?were?susceptible?to neomycin, but their sensitivity to 11 other antibiotics tested was largely different. Among the 12 antibiotics, the incidence of ampicillin resistance was the highest (66%). Our findings motivate the future utilization of the Bacillus strains from Pixian broad bean paste.
Optimized Co-fermentation of Horse Milk by Yeast and Lactic Acid Bacteria to Produce Angiotensin-converting Enzyme-Inhibiting Peptides
TANG Rong, WANG Kang, GUO Yuansheng, LIU Yanmin, SUN Jianping, ZHU Jianjun, CHAGAN Irbis
2022, 43(6):  236-245.  doi:10.7506/spkx1002-6630-20210217-184
Asbtract ( 228 )   HTML ( 41)   PDF (3555KB) ( 132 )  
Related Articles | Metrics
This study aims to obtain biologically active peptides with angiotensin-converting enzyme (ACE)-inhibiting activity by co-fermenting horse milk with lactic acid bacteria and yeasts isolated from traditional Koumiss. Lactococcus lactis L8 and Yarrowia lipolytica Y7, fermented milk with which inhibited ACE activity by 38.67% and 51.33%, were used for mixed-strain fermentation of horse milk. Horse milk fermented under optimum conditions determined using one-fact-at-a-time method and response surface methodology inhibited ACE activity by as high as 80.67%. The ACE-inhibiting activity significantly increased compared with that obtained with single-strain fermentation. An active fraction with ACE-inhibiting rate of 86% was separated from the co-fermented product. In conclusion, fermented horse milk is a potential source of ACE-inhibiting peptides.
Component Analysis
Characterization of Flavor Components of Dry-Cured Ham with Different Salt Substitute Formulations Using Solid Phase Microextraction-Gas Chromatography-Mass Spectrometry, Electronic Nose and Electronic Tongue
LIU Xin, MU Baide, JU Ming, CUI Fushun, LI Guanhao, PIAO Chunxiang, CUI Mingxun
2022, 43(6):  246-256.  doi:10.7506/spkx1002-6630-20210427-381
Asbtract ( 200 )   HTML ( 41)   PDF (2773KB) ( 168 )  
Related Articles | Metrics
This work aimed to study the effects of different salt formulations on the physicochemical properties, bacterial flora changes, volatile flavor compounds, and flavor characteristics of dry-cured ham. For this purpose, four groups were set up, namely, one control group (100% sodium chloride), and three groups of NaCl replacement (K: 30% potassium lactate + 70% sodium chloride; K + L: 18% potassium lactate + 12% lysine + 70% sodium chloride; K + J: 18% potassium lactate + 12% arginine + 70% sodium chloride). Results showed that the contents of moisture and proteins were higher, ash and salt contents were lower (P < 0.05), and salt reduction was greater in the K + L group as compared to the control group. Illumina MiSep sequencing indicated that Staphylococcus and lactic acid bacteria were the dominant microorganisms in dry-cured sausage. Sixty-four volatile compounds were identified by solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS), and the results of electronic nose and electronic tongue showed that K + L group samples were clearly distinguished from the control group on days 0 and 270 of ripening. Sensory evaluation and electronic tongue proved that the K + L group had better acceptance. Partial least squares regression analysis showed that pentadecanal, 2-butyl-1-octanol, and ethyl caproate were the key markers for the formation of ham flavor in the K + L group. Correlation analysis of volatile compounds and microorganisms showed that Staphylococcus and lactic acid bacteria could promote the production of volatile compounds. In conclusion, 18% potassium lactate + 12% lysine is an ideal substitute for sodium chloride in dry-cured ham, which can reduce the salt content of dry-cured ham by 15.71% and impart better flavor for dry-cured ham.
Physicochemical and Functional Properties and Nutritional Value of Flaxseed Protein
MA Dekun, WANG Ruhua, LÜ Xiao, YANG Zitong, WU Shufen, GAO Junwen, CHEN Baoyi, HAN Zhao, GUO Qingbin
2022, 43(6):  257-264.  doi:10.7506/spkx1002-6630-20210331-402
Asbtract ( 338 )   HTML ( 41)   PDF (2991KB) ( 149 )  
Related Articles | Metrics
Although cold-pressed flaxseed meal is rich in protein, it is mainly used as animal feed or discarded, resulting in a serious waste of resource. In this study, protein was extracted from flaxseed meal by alkali dissolution followed by acid precipitation, and its physical properties and nutritional value were evaluated. The results demonstrated that the protein content of the extract was as high as 98.86%. Sodium dodecyl sulfate-polyacrylamide gel?electrophoresis?(SDS-PAGE) analysis showed the darkest bands at 21 and 33 kDa. A total of 11 flaxseed proteins reported in the literature were identified in the protein by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), and the isoelectric point (pI) of the protein was located around at pH 4.0. A total of 17 amino acids including many essential ones were detected in the protein using an automatic amino acid analyzer. The oil-binding capacity of the protein was more than five times as large as its water-holding capacity. Moreover, the protein exhibited high emulsification activity, but its emulsion stability was slightly poor. The stability of the secondary structure was moderate, but it had good thermal stability.
Changes of Volatile Odor Substances in Chilled Tan Sheep Meat Stored for Different Periods and Cooked
SHAN Qimei, LUO Ruiming, YANG Bo, BI Yongzhao
2022, 43(6):  265-271.  doi:10.7506/spkx1002-6630-20210419-253
Asbtract ( 194 )   HTML ( 36)   PDF (2003KB) ( 110 )  
Related Articles | Metrics
The changes of volatile odor substances in chilled Tan sheep meat stored for different periods (0, 2, 4, 6, 8 and 10 days) at 0–4 ℃ and cooked in boiling water were investigated using solid phase micro-extraction (SPME) combined with gas chromatography-mass spectrometry (GC-MS) and an electronic nose system. In total, 38 volatile compounds were detected, including 19 aldehydes, 11 alcohols, 4 ketones, 3 acids and 1 heterocyclic compound. More specifically, the numbers of volatile compounds identified from meat samples stored for 0, 2, 4, 6, 8, and 10 days were 24, 26, 30, 32, 31 and 29, respectively, showing a trend of first increasing and then decreasing with storage period. The key aroma components in cooked meat were identified by relative odor activity value (ROAV). Among them, hexanal, octanal, heptanal, (E)-2-octenal, nonanal, benzaldehyde, 1-pentanol, 1-hexanol, 1-octene-3-ol, and 2-pentyl furan were common to all six samples with aldehydes being the predominant ones, contributing a lot to the flavor of cooked Tan sheep meat. The ROAV of aldehydes increased initially and then decreased, reaching the highest level on the 4th day. The results of the electronic nose showed that cooked four-day stored meat had greater odor intensity and better flavor.
Effect of Browning Reaction on the Metabolite Profile of Yogurt Analyzed by Untargeted Metabolomics Based on Ultra-high Performance Liquid Chromatography-Quadrupole Electrostatic Field Orbitrap Mass Spectrometry
LI Meng, NING Xuenan, KANG Jiaxin, LIAO Minhe, REN Haowei, LIU Ning
2022, 43(6):  272-278.  doi:10.7506/spkx1002-6630-20210504-019
Asbtract ( 191 )   HTML ( 30)   PDF (2450KB) ( 84 )  
Related Articles | Metrics
In this study, untargeted metabolomics based on ultra-high performance liquid chromatography-quadrupole electrostatic field orbitrap mass spectrometry (UPLC-QE-MS) was used to explore the differences in metabolite profiles between ordinary yogurt and brown yogurt, and the differences between them were evaluated from the perspective of metabolites. The metabolite information of yogurts was collected in both the positive and negative ion modes, and the metabolites were screened by multivariate statistical analysis. A total of 117 differential metabolites were obtained. Compared with ordinary yogurt, the relative contents of 106 metabolites were up-regulated and 11 metabolites were down-regulated in brown yogurt. Compared with ordinary yogurt, the contents of 3 flavor amino acids, 8 peptides, 12 sugars, 2 Maillard reaction products and one quinone in brown yogurt changed significantly. The results of this study can provide some theoretical support for the future research and development of brown yogurt.
Effects of Frying Time on Volatile Flavor Compounds in Fried Pepper (Zanthoxylum bungeanum) Oil as Analyzed by Gas Chromatography-Ion Mobility Spectrometry and Multivariate Statistical Analysis
NI Ruijie, ZHAN Ping, TIAN Honglei
2022, 43(6):  279-286.  doi:10.7506/spkx1002-6630-20210429-417
Asbtract ( 179 )   HTML ( 41)   PDF (3134KB) ( 118 )  
Related Articles | Metrics
In order to investigate the effect of frying time on the aroma of fried Hancheng pepper oil (HPO), four HPOs (HPOs 1, 2, 3 and 4) were prepared by frying Dahongpao pepper at 130 ℃ for 5, 15, 25 and 35 minutes with rapeseed oil as the carrier oil, respectively. Descriptive sensory analysis (DSA), an electronic nose (E-nose) system and gas chromatography-ion mobility spectrometry (GC-IMS) were employed to compare and analyze the volatile flavor compounds of the HPOs, and multivariate statistical analysis was used to explore differential volatile compounds between these four HPOs. Both DSA and E-nose results indicated that significant differences were observed between the HPOs; among them, HPO2 showed very strong herbal, lemon-like and pine-like aromas, with moderate fatty and green attributes and a very weak burnt. A total of 46 volatile compounds, including 19 aldehydes, 15 terpenes, 8 alcohols, 3 esters and 1 ketone, were identified from the four HPOs by GC-IMS. The types of volatile compounds in the HPOs were similar, in spite of significant differences in peak intensities. The contents of aldehydes including hexanal, heptanal and (E)-2-heptanal showed an increasing trend with increasing frying time; the contents of α-terpinene, phellandrene, 4-terpineol, ethyl 3-methylbutyrate and acetal showed an increasing and then decreasing trend, while a reverse trend was observed for alcohols and esters; however, the contents of terpenoids did not change so much. Principal component analysis (PCA) showed that the four HPOs were classified into two groups; one group contained HPO1 and HPO2, and another group contained HPO3 and HPO4, which was consistent with the results of linear discriminant analysis (LDA) from the E-nose data. The results of partial least square discriminant analysis (PLS-DA) showed that limonene, α-phellandrene, acetal, α-pinene and ethyl 3-methylbutyrate were the characteristic aroma compounds of HPO2, and 20 compounds were identified as differential markers, mainly including linalool, β-pinene, α-pinene, limonene, α-phellandrene, hexanal, heptanal, (E)-2-hexanal, (E)-2-heptenal, furfural, 2-methylbutanal, methylpropanal, 2-propenal, 1-propanol and ethyl-3-methylbutanoate.
Effect of Roasting on Moisture Migration and Key Aroma Compounds of Mutton Tallow
WANG Yongrui, BAI Shuang, LUO Ruiming, WANG Songlei
2022, 43(6):  287-294.  doi:10.7506/spkx1002-6630-20210406-067
Asbtract ( 193 )   HTML ( 31)   PDF (2400KB) ( 70 )  
Related Articles | Metrics
Moisture distribution and migration in the tallow of Tan sheep from Yanchi, Ningxia roasted for different periods were analyzed by low field-nuclear magnetic resonance (LF-NMR). Head space solid phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) and an electronic nose (E-Nose) were used to analyze the volatile components of mutton tallow. The results showed that the L* value of mutton tallow decreased, and the a* and b* values increased with roasting time. The percentage of weakly bound water showed an increasing trend, and the percentage of immobile water showed a decreasing trend. The relaxation time T23 showed a significantly decreasing trend with roasting time, indicating tighter binding of water molecules to macromolecular substances. A total of 78 volatile compounds were detected in 10 samples, including 12 aldehydes, 11 alcohols, 9 ketones, 4 alkanes, 10 acids, 12 esters, 12 heterocyclic compounds and 8 other compounds, with hexanal, nonanal, 1-octene-3-ol, 3-hydroxy-2-butanone, 7-methyl-3-methylene-1,6-octadiene and toluene being the major ones. Esters were found mainly in the early stage of roasting, while heterocyclic compounds, especially pyrazine compounds, mainly in the late stage. Principal component analysis performed on E-nose data showed that different roasting periods had significant effects on the contents of nitrogen oxides, benzenes, organic sulfur compounds and alcohols in mutton tallow, but little effect on alkanes, hydrides and ammonia compounds.
Principal Component Analysis for Comprehensive Evaluation of Free Amino Acids in Cultivated and Wild Morchella
FAN Tingting, ZHAO Xiaoyan, LI Xiaobei, ZHANG Yanmei, LI Jianying, ZHOU Changyan
2022, 43(6):  295-302.  doi:10.7506/spkx1002-6630-20210308-096
Asbtract ( 211 )   HTML ( 23)   PDF (2216KB) ( 154 )  
Related Articles | Metrics
The composition and content of free amino acids (FAAs) in cultivated and wild Morchella collected from Yunnan, Sichuan, Jilin and Gansu provinces were detected using an automatic amino acid analyzer, and their taste characteristics were evaluated by taste activity value (TAV). Additionally, comprehensive evaluation was conducted by principal component analysis (PCA) and cluster analysis. The results showed that wild Morchella contained abundant FAAs, with total contents of 18 FAAs ranging from 29.04 to 35.48 mg/g. Neither Trp nor Pro was detected in cultivated Morchella, and the total FAA content of cultivated Morchella greatly varied obviously among the samples from different provinces, ranging from 20.77 to 43.07 mg/g. The total FAA content of wild Morchella was generally higher than that of cultivated Morchella from the same provinces, and thus the former could taste better than the latter. The contents of sweet, bitter and aromatic amino acids in cultivated Morchella from Jilin were relatively high. Glu had the greatest effects on the umami taste of Mochella. The TAV of wild and cultivated Morchella were in the range of 13.75–17.79, and 5.28–11.02, respectively. Wild Morchella from Yunnan had the highest content of umami amino acids. Arg had the highest TAV of the bitter amino acids. The content of bitter amino acids in wild Morchella was lower than that in cultivated Morchella. In conclusion, wild Morchella has a strong umami taste, and cultivated Morchella from Jilin has the best nutritional quality in terms of amino acids.
Quality Analysis and Evaluation of Five Cultivars of Chimonobambusa quadrangularis Shoots with Color Shell from Jinfoshan Mountain
YANG Jinlai, GAO Guibin, ZHANG Fusheng, ZHENG Jiong, WU Liangru
2022, 43(6):  303-308.  doi:10.7506/spkx1002-6630-20210414-199
Asbtract ( 308 )   HTML ( 44)   PDF (2034KB) ( 128 )  
Related Articles | Metrics
The quality of five cultivars of Chimonobambusa quadrangularis shoots with color shells (black, yellow, brown, red and green) from Jinfoshan Mountain was systematically analyzed and evaluated in terms of texture, color, protein and amino acid, fat, crude fiber, total sugar, vitamin C, selenium, and aroma. The results showed that there were obvious differences in the color of shell and flesh among cultivars. The a* value of red shoot shells was ?0.07 ± 0.01 and the b* value of green shoot shells was 27.40 ± 0.99; the flesh of green-shelled shoots had a minimum a* value of ?6.50 ± 0.04. Brown-shelled shoots had moderate hardness ((1 934 ± 90) g) and better crispness and chewiness. The five cultivars had water content of more than 92%, protein content of 2.21%–3.16%, fat content of 0.11%–0.21%, and crude fiber content of 1.31%–1.72%. The lowest and highest content of total sugar of (0.62 ± 0.01)% and (1.62 ± 0.03)% were found in green- and brown-shelled shoots, respectively. The content of vitamin C in all five cultivars was 1.22–1.63 mg/100 g, and selenium content ranged from 0.78 to 1.65 μg/100 g. In addition, the content of essential amino acids was as high as (735.53 ± 11.09) mg/100 g in fresh brown-shelled shoots, containing a higher level of protein and total sugar, but a lower level of crude fiber. In contrast, green-shelled shoots had a higher level of crude fiber and selenium but a lower level of total sugar. Hexanal, 2-hexenal, hexanol, trans-2-nonen-1-ol, 2-heptanol, 2-heptanone, and 2,5-heptanedione were identified as the major volatile components of Chimonobambusa quadrangularis shoots, and the volatile composition varied depending on the cultivar. The above findings will provide data support for the consumption, development and utilization of C. quadrangularis shoots with different shell colors.
Untargeted Analysis of Flavor Differences among Fermented Capsicum frutescens from Different Cultivars Based on Headspace Solid Phase Microextraction-Gas Chromatography-Mass Spectrometry
YE Zi, SHANG Zhixun, LI Meiqi, REN Hongbing, QU Yonghan, HU Xiaosong, YI Junjie
2022, 43(6):  309-316.  doi:10.7506/spkx1002-6630-20210308-098
Asbtract ( 214 )   HTML ( 27)   PDF (2877KB) ( 138 )  
Related Articles | Metrics
In this study, aroma profiles of fresh and fermented chili pepper from nine Capsicum frutescens cultivars were compared using untargeted analysis based on headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). Furthermore, multivariate data analysis was adopted to identify the characteristic aroma compounds of fermented chili pepper. The results showed that esters and terpenes were the major characteristic volatile components in fresh chili pepper. The number and amount of esters and terpenes increased significantly after fermentation (P < 0.05). Ocimene, hexanal, (E)-2-hexanal, 1-hexanol, linalool, methyl salicylate, and 4-methylpentyl 3-methylbutanoate were common to fresh chili pepper from the nine cultivars, while the volatile aroma compounds common to fermented chili pepper were (E)-2-heptanal, (E)-2-octenal, 1-octene-3-one, (E)-linalool oxide (furanoid), ethyl salicylate and α-terpineol. 1-Octene-3-one and (Z)-3-hexenyl hexanoate were the most predominant aroma-active compounds in fresh and fermented chili pepper, respectively. Moreover, a significant difference was observed among cultivars in terms of the profile of aroma compounds. The multivariate data analysis indicated that esters (benzyl 2-methylbutanoate, pentyl 3-methylbutanoate, benzyl pentanoate) and terpenes (D-limonene, ocimene, anethole) contributed to the difference in the flavor of fermented chili pepper among cultivars. The aroma profile of fermented chili pepper described in this study can provide theoretical support for flavor evaluation of and variety selection for fermented chili pepper.
Analysis of Volatile Components in Potatoes with Dry Rot by Headspace-Gas Chromatography-Ion Mobility Spectrometry
ZHANG Fan, ZHANG Yufan, SU Xinyue, XU Wenya, AN Huanjiong, MA Qianyun, SUN Jianfeng, WANG Jie, WANG Wenxiu
2022, 43(6):  317-323.  doi:10.7506/spkx1002-6630-20210403-039
Asbtract ( 134 )   HTML ( 23)   PDF (3686KB) ( 91 )  
Related Articles | Metrics
In this study, headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) was employed for the analysis of volatile substances in healthy potatoes and those with different degrees of dry rot (light, moderate and heavy). The results showed that 43 volatile components were identified, including 18 aldehydes, 9 alcohols, 5 ketones, 5 alkenes, 2 esters, 2 amines, 1 furan and 1 ether. The contents of octene, α-carcelene, cyclohexanone, heptyl aldehyde and acetaldehyde went up with increasing severity of dry rot, and dipropyl disulfide, styrene, isobutanol and nonenal were produced in samples with heavy soft rot as the specific volatile components related to metabolites of Fusarium sambucinum. Fingerprints were developed that allowed to visually discern the differences in volatile components between samples with different degrees of rot severity. Principal component analysis (PCA) showed that the healthy and rotten potatoes could be effectively distinguished based on volatile components. We concluded that HS-GC-IMS allows visual comprehensive identification of the differences in volatile components between potatoes with different degrees of rot severity and effective identification of the specific volatile components of potatoes with dry rot, which can provide the theoretical basis for the diagnosis and identification of dry rot in potatoes based on odor sensing information.
Effects of Different Drying Methods on Volatile Flavor Components of Daylily Powder Analyzed by Gas Chromatography-Mass Spectrometry Combined with Electronic Nose
MA Yao, HAO Huihui, ZHANG Haihong, YANG Jinghui, MA Xuemei
2022, 43(6):  324-330.  doi:10.7506/spkx1002-6630-20210316-216
Asbtract ( 176 )   HTML ( 38)   PDF (2539KB) ( 142 )  
Related Articles | Metrics
In order to clarify the effect of drying methods on the volatile composition of daylily powder, an electronic nose system and headspace solid phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) were used to analyze the volatile components of daylily subjected to natural drying, hot air drying, vacuum freeze drying or spray drying. Principal component analysis (PCA) was performed on the volatile composition data of the four dried samples. The results showed that a total of 68 volatile substances were detected in these samples, including 41 in the natural dried sample, 41 in the hot air dried sample, 35 in the vacuum freeze dried sample, and 26 in the spray dried sample. Among them, the vacuum freeze-drying sample had the highest content of total volatile components of 56.36 μg/g. PCA and linear discriminant analysis (LDA) clearly distinguished the different drying methods. In conclusion, hot air drying retains the volatile flavor compounds of daylily and thus imparts a better flavor. Our findings can provide a theoretical basis for the utilization of daylily powder in the future.
Safety Detection
Inorganic Arsenic Analysis in Rice by Hydride Generation Inductively Coupled Plasma-Tandem Mass Spectrometry
LI Aiyang, HUANG Jianhua
2022, 43(6):  331-336.  doi:10.7506/spkx1002-6630-20210503-013
Asbtract ( 170 )   HTML ( 14)   PDF (2021KB) ( 85 )  
Related Articles | Metrics
A high throughput analytical method for the direct determination of inorganic arsenic content in rice by hydride generation (HG) inductively coupled plasma-tandem mass spectrometry (ICP-MS/MS) was established. Inorganic arsenic was extracted from rice samples with a mixture of nitric acid and hydrogen peroxide. Arsenic (V) was pre-reduced into arsenic (III) by adding 5 mol/L hydrochloric acid, and then 2 g/100 mL sodium borohydride solution was used to reduce inorganic arsenic (III) into volatile arsenic hydride (AsH3) in a multimode sample introduction system (MSIS). Finally, AsH3 was injected into the ICP-MS/MS system and directly detected. In the MS/MS mode, arsenic was transferred to arsenic oxide using oxygen as reaction gas to eliminate the mass spectral interference. The limit of detection (LOD) for arsenic was 0.004 μg/L. The results of the method for inorganic arsenic in standard reference materials of rice flour (GBW(E)100348a, GBW(E)100349a, and NIST SRM1568b) were consistent with the certified values, indicating good accuracy of the method. Inorganic arsenic in rice could be detected using this method without chromatographic separation of different arsenic species. This method was characterized by simple and rapid operation, high sensitivity, good accuracy and high reliability, and applicable for the determination of inorganic arsenic content in rice.
Comparative Analysis of Three Accelerated Lipid Oxidation Methods
YANG Yifang, LUO Manni, HU Qiuhong, ZHU Xuncun, LI Qi, ZHANG Lin, YU Qinxin, XIAO Zihan, YANG Yong
2022, 43(6):  337-346.  doi:10.7506/spkx1002-6630-20210121-233
Asbtract ( 176 )   HTML ( 22)   PDF (2934KB) ( 77 )  
Related Articles | Metrics
The effects of high-temperature heating, repeated freezing and thawing, and ultraviolet (UV) irradiation on the acceleration of lipid oxidation in pork backfat were compared. Changes in the acid value (AV), free fatty acid (FFA) content and composition, peroxide value (POV), thiobarbituric acid reactive substances (TBARS) value, lipid oxidation products (LOP) and microbial load of pig backfat were measured to obtain the most suitable accelerated lipid oxidation method. The results showed that high-temperature heating treatment was the most effective way to promote lipid oxidation, increasing the POV from (0.008 3 ± 0.00) to (0.053 0 ± 0.00) g/100 g and the TBARS value from (0.24 ± 0.01) to (0.65 ± 0.00) mg/kg. Repeated freezing-thawing treatment increased the POV from (0.018 0 ± 0.00) to (0.034 7 ± 0.00) g/100 g and the TBARS value from (0.13 ± 0.00) to (0.25 ± 0.00) mg/kg, and UV irradiation increased the POV from (0.008 1 ± 0.00) to (0.019 8 ± 0.00) g/100 g and the TBARS value from (0.07 ± 0.00) to (0.21 ± 0.00) mg/kg. No microorganisms were detected in the high-temperature heating treatment. In the repeated freezing-thawing and UV irradiation treatments, the number of microorganisms gradually increased with the number of freezing-thawing cycles or irradiation time. This does not rule out the influence of microbial growth on lipid oxidation. Therefore, high-temperature heating treatment is the most suitable method to accelerate lipid oxidation among these three methods.
Analysis of Foodborne Pathogenic Bacteria in Rice Noodles by High-throughput 16S rDNA Sequencing
WU Yi, LIU Lulu, WU Yongmin, DAI Shiqiong, SHANG Ying, CAO Jianxin, HAN Peng
2022, 43(6):  347-352.  doi:10.7506/spkx1002-6630-20210115-165
Asbtract ( 194 )   HTML ( 19)   PDF (2684KB) ( 94 )  
Related Articles | Metrics
In order to understand foodborne pathogen contamination in rice noodles, the temporal trend in the bacterial flora structure in rice noodles from raw material to table was investigated. High-throughput 16S rDNA sequencing was used to analyze the bacterial community in ten rice noodle samples. The results showed that the sequencing data were annotated into 5 phyla, 11 classes, 19 orders, 24 families and 29 genera. Also, it was found that the relative abundance of Proteobacteria was more than 50% in all samples, followed by Firmicutes. Salmonella and Bacillus were found in all samples. Staphylococcus, Escherichia and Listeria were found in the raw materials and final products. Bacillus cereus and Salmonella were detected in each sample. Staphylococcus aureus, Escherichia coli O157:H7 and Listeria monocytogenes were also detected in the raw materials and products, suggesting that there is a safety risk on the consumption of rice noodles.