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25 January 2018, Volume 39 Issue 2
Food Chemistry
Effect of Complex Interface on Lipid Digestion in Food Emulsion
YAO Xiaolin, NIE Ke, CHEN Yu, ZHANG Kun, FANG Yapeng
2018, 39(2):  1-7.  doi:10.7506/spkx1002-6630-201802001
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In this study, emulsion was prepared with medium-chain triglyceride (MCT) as oil phase, and gum arabic (GA), whey protein isolate (WPI) and Tween 80 (T80) as emulsifiers to design complex emulsion interface. The interfacial structure of emulsions was varied by controlling the sequence of adsorption of the components at the interface using layer-by-layer adsorption or mixed adsorption. The effect of interfacial structure on the rate of lipid digestion was evaluated using a simulated intestinal lipolysis model by interfacial rheology. The results showed that individual GA or WPI interface presented higher interface modulus than T80 interface along with good viscoelasticity, and the ability to resist bile salt displacement and delay lipid digestion was as follows: GA < WPI < T80. In complex emulsions, the interface dominated by T80 showed a better ability to delay lipolysis and resist of bile salt displacement than the interface composed of GA (WPI) and T80.
Preparation and Application of Nano Nickel Catalyst for Hydrogenation of Soybean Oil
WANG Liqi , LI Zhongbin, LIU Fang, YU Dianyu, SUI Yulin
2018, 39(2):  8-13.  doi:10.7506/spkx1002-6630-201802002
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Nano-sized nickel catalyst was prepared by the liquid phase reduction method and characterized by X-ray diffraction, scanning electron microscopy, particle size analysis and N2 adsorption-desorption isotherms. The results indicated that the specific surface area of the catalyst was 42.35 m2/g, the average particle size was 30.0 nm, and the entrance capacity was 0.029 cm3/g. The surfactant adhering to the catalyst surface endowed it with good sphericity and dispersivity, being beneficial to improve its activity. Nano nickel was 2.01 times more active in hydrogenating first-grade soybean oil than raney nickel. When the iodine value of hydrogenated oil was about 90 g I/100 g, the selectivity of nano nickel catalyst was 0.51 for linoleic acid and 0.35 for trans fatty acids isomerization, and the trans fatty acid content of the hydrogenated oil was decreased by 10.79% compared with that hydrogenated with raney nickel.
Relationship between Protein Oxidation and Water Holding Capacity of Yak Meat under Freeze-Thaw Cycles
LI Wanzhu, LIANG Qi, ZHANG Yan, WEN Pengcheng
2018, 39(2):  14-19.  doi:10.7506/spkx1002-6630-201802003
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This study was designed to explore the effect of freeze-thaw cycles on the protein oxidation and water holding capacity of yak meat and also to investigate the relationship between the two parameters. Longissimus dorsi samples were collected from the carcass of 3-year-old Gannan yaks, and the changes in pH, thawing loss, cooking loss, pressurized water loss, carbonyl group and total sulfydryl group contents and protein solubility of repeatedly frozen-thawed yak meat were analyzed. The results showed that with an increase in the number of freeze-thaw cycles, pH was significantly decreased as well as water holding capacity (thawing loss, pressurized water loss and cooking loss) were significantly decreased (P < 0.05), the degree of protein oxidation (carbonyl group and total sulfydryl group contents) was significantly increased (P < 0.05), and total, myofibrillar and sarcoplasmic protein solubility were significantly decreased (P < 0.05). pH was significantly correlated with water holding capacity and protein oxidation (P < 0.05). During 7 freeze-thaw cycles, pH decreased at a rate similar to water holding capacity. Moreover, after the fourth cycle, the rate of decrease in water holding capacity was slowed down and the rate of protein oxidation was speeded up. All these results demonstrated that freeze-thaw cycles gave a rise to a significant rise in the degree of protein oxidation and caused a significant reduction of the water holding capacity of yak meat. Therefore, controlling protein oxidation during storage is effective in enhancing the quality of yak meat.
Effect of Sodium D-Isoascorbate on the Quality of Blueberry Jam
XIA Qile, CHEN Jianbing, GAO Haiyan, XING Jianrong
2018, 39(2):  20-24.  doi:10.7506/spkx1002-6630-201802004
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In order to improve the quality of blueberry jam during its processing, changes in anthocyanin content, total phenol content and 1,1-dipheny1-2-picryl-hydrazyl (DPPH) and 2,2’-amino-di(3-ethyl-benzothiazoline sulphonic acid-6) ammonium salt (ABTS) radical scavenging activities of blueberry jam at different stages of processing such as pulping, formulation, filling and sterilization were detected. The effect of added sodium D-isoascorbate on the functional components of blueberry jam was studied as well as its inhibitory effect on the loss of antioxidant activity. Meanwhile, changes in anthocyanin content, total phenol content, and L*, a* and b* values were measured during storage. Anthocyanin content, total phenol content and antioxidant activity gradually decreased during the whole production process. This decrease was slowed down by addition of sodium D-isoascorbate. During incubation at constant temperature, the degree of fading was reduced by about 21.07% by adding sodium D-isoascorbate. Thus, addition of sodium D-isoascorbate can improve the nutritional quality and stability of blueberry jam and prolong its shelf life.
Effects of Rutin and Quercetin on the Physicochemical Properties of Wheat Starch
REN Shuncheng, SUN Xiaosha
2018, 39(2):  25-30.  doi:10.7506/spkx1002-6630-201802005
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Changes in the thermal properties, microstructure, rheological properties, gelatinization properties and texture of wheat starch were examined in the presence of low-dose rutin or quercetin, as well as the effect of rutin and quercetin on wheat starch-iodine complex. It was found that the onset gelatinization temperature (T0), peak gelatinization temperature (TP) and gelatinization conclusion temperature (TC) of wheat starch did not change significantly after adding rutin or quercetin. The retrogradation enthalpy (ΔH2) increased significantly by 85.71% and 85.71%, respectively, and the retrogradation degree (R) also increased significantly by 156.09% and 93.24%, respectively. At the same time, electron microscopy showed that rutin and quercetin accelerated the retrogradation process, decreasing the storage modulus and loss modulus. Rapid visco analysis (RVA) results showed that rutin and quercetin decreased the peak viscosity of wheat starch by 5.56% and 18.10%, minimum viscosity by 6.41% and 21.32%, final viscosity by 3.28% and 14.22%, and peak time by 1.93% and 4.16%, and increased setback by 3.36% and 0.52%, and pasting temperature by 0.63% and 3.25%, respectively. Moreover, rutin and quercetin reduced the hardness of wheat starch by 44.60% and 34.52%, adhesiveness by 60.79% and 30.95%, and springiness by 2.94% and 3.13%, and increased cohesion by 16.13% and 16.13%, respectively. Quercetin could interact strongly with wheat starch, form V-type inclusion complex. In general, rutin and quercetin can significantly influence the physicochemical properties of wheat starch.
Structural Analysis and Anti-Pancreatic Lipase Activity of Flavonoids from Moringa oleifera Lam. Leaves
WANG Yuan, ZHENG Wen, CAI Junjun, YUAN Tianqing, GONG Xingwen
2018, 39(2):  31-37.  doi:10.7506/spkx1002-6630-201802006
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The structure of flavonoids from Moringa oleifera Lam. leaves (FML) was analyzed. Meanwhile, the inhibitory effect of FML on pancreatic lipase was determined and the type of inhibition was investigated. The extraction yield of flavonoids reached (5.53 ± 0.11)% with microwave-assisted extraction using 70% ethanol as the extraction solvent. The obtained crude extract was purified by polyamide column chromatography and freeze-dried to obtain a powder. The total flavonoid content of the powder was (661.10 ± 9.20) mg/g. A total of 11 flavonoids were identified from FML by ultra performance liquid chromatography-quadrupole/electrostatic field orbital trap mass spectrometry (UPLC-Q-Orbitrap MS). The inhibitory activity of FML on pancreatic lipase was determined with p-nitrophenyl butyrate as substrate. The results showed that the purified FML had a strong inhibitory effect on pancreatic lipase, with an IC50 of 0.94 mg/mL, and the type of inhibition was determined as non-competitive inhibition by the Lineweaver-Burk double reciprocal plot method.
Antioxidant Capacity and Anthocyanins of Purple-Fleshed Sweet Potato Cultivars
ZOU Bo, ZENG Dan, WU Jijun, YU Yuanshan, XIAO Gengsheng, XU Yujuan
2018, 39(2):  38-44.  doi:10.7506/spkx1002-6630-201802007
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The antioxidant activities and anthocyanin composition of purple sweet potatoes from nine varieties cultivated in Guangdong were determined. The results indicated that total phenolic contents and antioxidant activities of different varieties were different. The total phenolic content of Guangzi 9 was 578 mg GAE/100 g fresh weight, and the 2,2’-amino-di (3-ethyl-benzothiazoline sulphonic acid-6) ammonium salt (ABTS+·) radical scavenging activity, oxygen radical absorbance capacity, and reducing power were 4.36, 10.38, and 11.23 μmol TE/g fresh weight, respectively, which were superior to those of the other varieties. Sixteen anthocyanins, including 8 cyanidins and 8 peonidins, were identified by high performance liquid chromatography-quadrupole-time of flight mass spectrometry (HPLC-QTOF-MS). The content of total anthocyanins was in the range of 77.17–1 125.06 mg/kg fresh weight, and Guangzi 9 showed the highest anthocyanin content. Acylated anthocyanins were the main anthocyanin constituents in purple sweet potatoes. Acylated anthocyanins were 89 times more abundant than non-acylated ones in Guangzi 9, which showed a significantly higher content of acylated anthocyanins than the other varieties. Taken together, the antioxidant activities and anthocyanin composition of different purple sweet potato varieties were different with Guangzi 9 exhibiting the highest content of anthocyanins and highest antioxidant capacity.
Preparation, Structural Characterization and Properties of Carboxymethyl Cassava Starch by Mechanical Activation-Assisted Solid-State Reaction
CHEN Yuan, YANG Jiatian, XIE Qiuji, WEI Qingmin, SU Feijing, LIANG Hongpian, HUANG Zuqiang
2018, 39(2):  45-52.  doi:10.7506/spkx1002-6630-201802008
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Carboxymethyl cassava starch was synthesized from cassava starch with monochloroacetate (MCA) as an etherifying agent and sodium hydroxide (NaOH) as a catalyst by mechanical activation-assisted solid-state reaction. One-factor-at-a-time and orthogonal array design methods were used to optimize the preparation conditions for higher degree of substitution (DS). The structure of carboxymethyl cassava starch was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscope (SEM) and its physicochemical properties were systematically investigated. The optimal process parameters that provided maximum DS of 0.540 1 were obtained as follows: molar ratio of starch to sodium chloroacetate 1:1, reaction temperature 50 ℃, reaction time 1.5 h, sodium hydroxide concentration 18.8%, stirring speed 380 r/min, and volume of?ball milling medium 500 mL. The etherification reaction of cassava starch was confirmed by FTIR, XRD and SEM. Results of the physicochemical properties showed that the solubility of carboxymethyl cassava starch and the viscosity of starch paste and were significantly increased; water-absorbing capacity, water-retaining capacity, freeze-thaw stability, and acid, alkali and enzyme resistance were also improved compared with the native starch.
Properties and Structure of Dietary Fiber from Tillering Onion
WANG Dawei, SONG Yunyu, LIU Yang, ZHANG Jing, CAO Chenyu
2018, 39(2):  53-57.  doi:10.7506/spkx1002-6630-201802009
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The water-holding capacity, oil-holding capacity, cation exchange capacity and cholesterol adsorption capacity of dietary fiber from tillering onion with different particle sizes were studied and the structure was determined by scanning electron microscopy (SEM), infrared spectroscopy and X-ray diffraction analysis. The results showed that the soluble dietary fiber content of tillering onion was 5.79%. The water-holding capacity, oil-holding capacity, swelling capacity and the cation exchange capacity of the dietary fiber were 14.83 g/g, 19.57 mL/g, 1.95 g/g and 0.62 mmol/g, respectively. The cholesterol adsorption capacity was 126.73 mg/g at pH 2, and 159.50 mg/g at pH 7. Under SEM, the dietary fiber exhibited an irregular fluffy network structure. Fourier transform infrared spectroscopy analysis suggested that the dietary fiber had the characteristic absorption peaks of cellulose and hemicelluloses, such as C=O, O—H, C—H. The results of X-ray diffraction indicated that the crystallinity of the dietary fiber was better and the crystalline and amorphous regions were preserved.
Bioengineering
Heterologous Expression and Characterization of Recombinant L-Glutamate Oxidase from Kitasatospora setae
CHEN Wen, LI Youran, GU Zhenghua, DING Zhongyang, ZHANG Liang, SHI Guiyang
2018, 39(2):  58-65.  doi:10.7506/spkx1002-6630-201802010
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In order to achieve efficient bioconversion of L-glutamic acid to alpha ketoglutaric acid (α-KG), the L-glutamate oxidase (LGOX) gene from Kitasatospora setae KM-6054 was expressed in Escherichia coli BL21. According to the known LGOX sequence from K. setae and the codon bias of E. coli, the optimized LGOX gene sequence was synthesized and cloned into the pET28a (+) vector, which was then transferred into E. coli BL21(DE3) to obtain a recombinant LGOX. And enzymatic properties of the recombinant LGOX were also investigated. Results showed that the recombinant LGOX activity could reach 49.10 U/mL after induction at an IPTG concentration of 0.1 mmol/L at 20 ℃ for 18 h. Subsequently, the recombinant LGOX was purified by affinity column chromatography to a specific activity of 45.98 U/mg and its molecular weight was about 70 kDa as determined by SDS-PAGE analysis. The enzymatic properties showed that the optimal reaction temperature and pH value were 40 ℃ and 6.0, respectively. The Michaelis-Menten constant Km was 1.23 mmol/L, and the maximum reaction rate Vmax was 76.24 μmol/(min·mg). L-glutamic acid was the optimal substrate for the LGOX. The heterologous expression and characterization of recombinant L-glutamate oxidase in this study can provide a new way for biosynthesis of α-KG.
Prokaryotic Expression of a 2-Ketogluconate Epimerase Gene from Pseudomonas plecoglossicida
SUN Wenjing, YANG Li, LUAN Fang, HE Xiaoyong, CUI Fengjie, WANG Daming, QIAN Jingya, QI Xianghui
2018, 39(2):  66-72.  doi:10.7506/spkx1002-6630-201802011
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The complete nucleotide sequence of the gene (kguE) encoding 2-ketogluconate epimerase was cloned by touchdown polymerase chain reaction (TD-PCR) from an industrial 2-ketogluconic acid producer, Pseudomonas plecoglossicida JUIM01. A recombinant vector was constructed by ligating the restriction enzymes digested products of the target gene to pET-28a(+) vector and then transferred into the expression host E. coli BL21(DE3). A specific fusion protein with molecular weight of about 30.5 ku was expressed in the recombinant strain E. coli BL21(DE3)/pET-28a(+)-kguE after isopropyl β-D-1-thiogalactopyranoside (IPTG) induction with a positive Western-blot result. Bioinformatic analysis showed that the protein was predicted to be a hydrophilic protein with molecular weight of 28.5 ku located in the cytoplasm, sharing 78% amino acid sequence identity with the 2-ketogluconate epimerase from P. putida. The predicted secondary structure consisted of 40.62% of α-helix, 17.19% of extended strand and 42.19% of random coil. This study is expected to provide a basis for further elucidating the function of 2-ketogluconate epimerase in P. plecoglossicida.
Optimization of Enzymatic Preparation of Protein Hydrolysate from Fruiting Bodies of Grifola frondosa for Improved Ferrous Chelating Ability and Its Antioxidant Activity
ZHAO Cong, CHENG Chen, YIN Shiyu, LI Yun, ZHU Can, HUANG Xiaoling, CHEN Guitang
2018, 39(2):  73-79.  doi:10.7506/spkx1002-6630-201802012
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In this study, we optimized the conditions for the enzymatic preparation of iron-chelating peptides from the fruiting bodies of Grifola frondosa and evaluated their antioxidant capacities. Six commercial proteases were screened for their suitability to hydrolyze Grifola frondosa protein, which was evaluated according to iron-chelating activity. One-factor-at-a-time and orthogonal array designs were employed to optimize the hydrolysis conditions based on iron-chelating activity. Meanwhile, the antioxidant capacity was studied using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radical scavenging assays. The results showed that peptides with the highest iron-chelating activity were obtained with alkaline protease. The optimal hydrolysis conditions were determined as follows: pH value, 9; alkaline protease dose, 1 800 U/g; temperature, 55 ℃; substrate concentration, 0.5 g/100 mL; and hydrolysis time, 2.5 h. Under these conditions, the iron-chelating activity and the degree of hydrolysis were 1.854 mg/g and 6.14%, respectively. The prepared peptides showed scavenging activity against DPPH and hydroxyl radicals in a concentration-dependent manner. In addition, the peptides possessed good iron-chelating ability and antioxidant activities, and could thus hold promise as a novel dietary supplement.
Carbon Utilization Profile and Growth Kinetics of Shewanella putrefaciens Isolated from Spoiling Fish
XIU Yanhui, GUO Quanyou, HAN Chengyi, CHEN Qingrong
2018, 39(2):  80-87.  doi:10.7506/spkx1002-6630-201802013
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In order to investigate the carbon source utilization profile of Shewanella putrefaciens at different temperatures, a kinetic model describing the growth of S. putrefaciens in multi-well plates at 5, 15, 25 and 33 ℃ was developed using modified Gompertz equation and the kinetic parameters maximum specific growth rate (μmax) and lag phase duration (λ) were obtained. Moreover, based on average well color development (AWCD) and utilization area, the carbon utilization rate of S. putrefaciens was analyzed. The results showed that S. putrefaciens presented the highest μmax and lowest λ at 25 ℃. Moreover, at this temperature, the highest carbon utilization and cell viability were observed followed by growth at 15 ℃; the cell viability at 5 ℃ was one-sixth of that at 25 ℃, and the lowest cell viability was found at 33 ℃. Temperature in the range of 5?25 ℃ exhibited a good linear relationship with and . The utilization rates of of carbohydrates and carboxylic acids were 30% and 29% at 5?33 ℃, respectively. Carbohydrates (dextrin, D-maltose, α-D-glucose, D-arabinol and stachyose), carboxylic acids (L-malic acid, L-lactic acid and acetoacetic acid), amino acids (L-serine, amino-acetyl-L-proline, L-aspartic acid and L-glutamic acid), fatty acids/lipids, amines/amides and other substances (gelatin, methyl pyruvate, Tween 40 and L-histamine) could be better utilized by the strain.
Effect of Endogenous Enzymes on Autolysis of Sea Cucumber Stichopus japonicus Guts
LI Aoting, DU Yinan, DUAN Xiuhong, CHAI Xiaoqian, WU Chao, TANG Yue, YU Cuiping, WU Haitao
2018, 39(2):  88-92.  doi:10.7506/spkx1002-6630-201802014
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The effect of endogenous enzymes on the autolysis of sea cucumber (Stichopus japonicas) guts was studied by addition of various protease inhibitors. The autolysis was evaluated by the release of trichloroacetic acid (TCA)-soluble oligopeptides and reducing sugar, and detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The results indicated that different inhibitors, including pepsin inhibitor, trypsin inhibitor, serine protease inhibitor, amylase inhibitor and β-1,3-glucanase inhibitor showed inhibitory effects on the autolysis of S. japonicus guts in a certain range of concentration. The serine protease inhibitor N-tosyl-L-phenylalaninyl-chloromethyl ketone (TPCK) showed relatively higher inhibitory effect than the other inhibitors. These results suggest endogenous enzymes, including pepsin, trypsin, serine proteases, amylase and β-1,3-glucanase, may be involved in the autolysis of S. japonicus guts.
Screening and Identification of Lactic Acid Bacterium with Antimicrobial and Antioxidant Activity
ZHANG Xiangmei, ZHAO Yuxing, YAN Xiaojing, CUI Na
2018, 39(2):  93-98.  doi:10.7506/spkx1002-6630-201802015
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In this study, lactic acid bacteria were isolated from pickle samples. All the isolates were primarily screened for their antimicrobial activity against six indicator strains such as Lactobacillus plantarum PL2 and Escherichia coli As1.184. Then the scavenging activities against hydroxyl radicals, superoxide anion and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals were measured to evaluate antioxidant activity of the isolates with antimicrobial activity. The results showed that eight strains with both antimicrobial and antioxidant activity were screened from pickles. The highest levels of antimicrobial activity and antioxidant activity were recorded in strain b-2, which was identified as L. plantarum by its physiological, biochemical and molecular characteristics. According to the results of antioxidant activity, the cell-free extract of b-2 showed the highest hydroxyl radical-scavenging activity, which scavenged 67.6% hydroxyl radical, while the intact cells exhibited the highest superoxide anion-scavenging activity, which scavenge 62.8% superoxide anion radical, and the highest DPPH radical-scavenging activity was seen in the cell-free supernatant, which scavenged 91.3% DPPH radical. To conclude, L. plantarum b-2 has good bacteriostatic ability and antioxidant capacity, and holds great potential as a functional lactic acid bacterial starter.
Prokaryotic Expression, Purification and Identification of Phospholipid Binding Activity of Anas platyrhynchas HSP90α
ZHANG Yumei, LI Pengpeng, ZHANG Muhan, WANG Jingjing, WANG Daoying, XU Weimin
2018, 39(2):  99-104.  doi:10.7506/spkx1002-6630-201802016
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The present study was conducted to express and purify the heat shock protein 90 alpha (HSP90α) of Anas platyrhynchas in prokaryotic expression system for further study of the mechanism of interaction between HSP90α and phospholipids and inhibition of phospholipid hydrolysis by HSP90α. The HSP90α gene was cloned from A. platyrhynchas skeletal muscle cDNA by RT-PCR. The gene sequence and its amino acid sequence were analyzed with bioinformatic tools. An inducible expression vector was constructed by enzyme digestion-ligation reactions and transformed into Escherichia coli for expression using isopropyl β-D-1-thiogalactopyranoside (IPTG) as an inducer. The recombinant protein was purified by Ni-NTA affinity chromatography and gel chromatography. As results, the open reading frame of HSP90α was 2 187 bp in length, and the deduced protein was composed of 728 amino acids with 5 glycosylation sites and 67 phosphorylation sites; its predicted isoelectric point was about 5. The E. coli vector pCold1-HSP90α successfully expressed the recombinant HSP90α protein in the supernatant of bacterial lysate. Thin-layer chromatography demonstrated that the recombinant HSP90α could stably bind to phosphatidylcholine. Lipolysis assay showed that HSP90α significantly restrained the hydrolysis of phospholipid. In conclusion, this study may provide a foundation for further study of the interaction between HSP90α and phospholipids and the potential of HSP90α to protect phospholipids in processed meat.
High Cell Density Fermentation of Tumor-Targeting Engineered Strain and Development of Lyoprotectant Formulation for Its Freeze-Drying
WANG Can, MO Xiangtao, ZHANG Feng, WU Liujuan, LI Tang, XIA Liqiu
2018, 39(2):  105-111.  doi:10.7506/spkx1002-6630-201802017
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The present study aimed to optimize the medium formulation for high cell density culture of an invasive tumor-targeting engineered strain, EcNA. Using one-factor-at-a-time method and a Plackett-Burman design, yeast extract and dipotassium phosphate were found to be the most important factors affecting cell concentration. The optimal medium, as determined using central composite design and response surface methodology, was composed of soluble starch 2 g/L, yeast extract 50.3 g/L, K2HPO4 14.26 g/L, KH2PO4 3 g/L, MgSO4 0.3 g/L, and trace element stock solution 2 mL/L, and the inoculum amount was 3%. The optical density at 600 nm (OD600 nm) of the bacterial culture obtained using the optimized medium reached 7.602 and the biomass was 2.96 × 109 CFU/mL, which was 78.3% higher than that before optimization. Moreover, using orthogonal array design, a lyoprotectant formulation consisting of skim milk 14.25 g/100 mL, sucrose 3 g/100 mL, VC-Na 3 g/100 mL was found to be optimal for the freeze-drying of the strain. The survival rate of the engineered bacterium was up to 86.32% during freeze-drying using the lyoprotectant, being beneficial for of prolonged storage life of oral capsules.
Optimization of the Preparation Process for Soluble Dietary Fiber from Rice Bran by Aspergillus niger Fermentation and Its Physicochemical Properties
MIN Zhongman, GAO Lu, GAO Yuzhe, XU Caihong, DENG Xuexue, XIAO Zhigang
2018, 39(2):  112-118.  doi:10.7506/spkx1002-6630-201802018
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Rice bran was fermented to produce soluble dietary fiber (SDF) with Aspergillus niger. The optimum fermentation conditions for higher yield of SDF were determined by one-factor-at-a-time method and Box-Behnken response surface methodology and the structural and physicochemical change of SDF before and after fermentation was examined. The maximum yield of SDF of 38.23% was achieved after fermentation at 26 ℃ and pH 5.0 with a solid-to-solvent ratio of 1:11 (g/mL) at a shaking speed of 150 r/min, which was improved by 29.58% compared with that before optimization. The swelling force, water-holding capacity and oil-holding capacity of SDF were increased respectively by 84.44%, 79.30% and 73.25% after fermentation. The result of scanning electron microscopy showed that fermented SDF displayed a rough surface and porous structure.
Production and Inhibitory Effect of Specific Egg Yolk Antibody Fab’ Fragment against Tyrosinase
ZHONG Xinxin, CAO Limin, LIN Hong, SHI Peiyu, SUI Jianxin
2018, 39(2):  119-123.  doi:10.7506/spkx1002-6630-201802019
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The production of Fab’ fragment from specific egg yolk antibody against tyrosinase and its inhibitory activity on tyrosinase were investigated in this paper. The optimal conditions were obtained as follows: pH 4.0, ratio of egg yolk antibody to pepsin 1:150 (mg/U), and reaction time 8 h. Fab’ fragment purified by immunoaffinity column chromatography to a purity of over 95% exhibited good physicochemical stability. It was demonstrated as a non-competitive inhibitor with an IC50 value of 11.16 μmol/L and a binding constant of 5.79 × 105, whose inhibitory effect was much higher than that of IgY. The results of this study can provide a theoretical basis for the application of egg yolk antibody Fab’ fragments in food, cosmetics and pharmaceutical industries as a potential enzyme inhibitor.
Fermentation Conditions and Antioxidative Activity of Mixed Extracts from Rhodiola sachalinensis and Codonopsis lanceolata by Lactobacillus pentosus
JIANG Guozhe, QUAN Zhenyu, JIN Runhao, HONG Heedo, HAN Chunji
2018, 39(2):  124-130.  doi:10.7506/spkx1002-6630-201802020
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Objective: To investigate the optimization of the fermentation of mixed extracts from Rhodiola sachalinensis and Codonopsis lanceolata (RCME) by Lactobacillus pentosus and to determine the composition of bioactive compounds and antioxidative activity of fermented RCME. Methods: The pH, acidity and mycelial biomass were evaluated as a function of the ratio between Rhodiola sachalinensis and Codonopsis lanceolata, soluble solid content of RCME and fermentation time. Variations in the total protein, neutral sugar, acidic polysaccharide and total phenolics contents in RCME before and after fermentation were determined using colorimetric method, as well as variations in salidroside and tyrosol contents by HPLC. The antioxidant activity of fermented RCME was evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2’-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt (ABTS) radical scavenging assay. Results: The pH and total acidity were little changed from 24 to 72 h of fermentation when Rhodiola sachalinensis was fermented alone and the viable cell count significantly decreased (P < 0.01). A 3:2 mixture of Rhodiola sachalinensis and Codonopsis lanceolata showed the greatest pH decline and largest increase in acidity at 24 h of fermentation, which remained little changed from 48 h onward, but the viable cell count dropped. Soluble solid content was in the range of 1.0%–3.0%, and the conversion rate of salidroside to tyrosol was not changed significantly from 48 to 72 h. However, salidroside content significantly decreased at 24 h compared with that at 0 h (P < 0.01), whereas tyrosol, acidic polysaccharide, total phenolics and protein significantly increased (P < 0.05 or P < 0.01). DPPH and ABTS+· scavenging activity of fermentation product were significantly higher than those of RCME (P < 0.01). Conclusion: The optimum fermentation conditions of RCME were determined as follows: ratio between Rhodiola sachalinensis and Codonopsis lanceolata ratio, 3:2; soluble solid concentration of RCME 1.0%–3.0%, temperature 37 ℃, and time 24 h.
Effect of Assimilable Nitrogen and Reducing Sugar Concentrations of Synthetic Grape Must on the Fermentation Characteristics of Saccharomyces cerevisiae
JIANG Yue, PAN Ting, XI Zhumei
2018, 39(2):  131-137.  doi:10.7506/spkx1002-6630-201802021
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In this study, fifteen combination treatments were designed using five yeast assimilable nitrogen (YAN) concentrations (150, 240, 330, 420, and 500 mg/L) and three reducing sugar concentrations (170, 200, and 230 g/L) to study the effects of different concentrations of assimilable nitrogen and reducing sugar in synthetic grape must on the fermentation characteristics of Saccharomyces cerevisiae. For this purpose, yeast growth, sugar consumption rate and nitrogen consumption were measured. The results showed that 150 mg/L of YAN nitrogen in the synthetic grape must was too low to support yeast growth and simultaneously restricted the consumption rate of reducing sugar by yeast. The rate of alcoholic fermentation was increased by increasing the initial concentration of reducing sugar to 200 g/L. Yeast could grow normally in the synthetic grape must with initial assimilable nitrogen concentrations of higher than 240 mg/L. In this case, initial reducing sugar and assimilable nitrogen concentration had no significant effect on yeast growth, and reducing sugar concentration had the most direct effect on the fermentation characteristics of S. cerevisiae strains, determining the fermentation time. In the synthetic grape must with low initial reducing sugar concentration (170 g/L), the yeast growth rate increased with increasing the initial assimilable nitrogen concentration, while at high initial reducing sugar concentration (200–230 g/L), the yeast growth rate was not affected by the initial assimilable nitrogen concentration. An initial assimilable nitrogen concentration of higher than 330 mg/L was not completely consumed, and the remaining amount increased with the increase in the initial concentration of assimilable nitrogen, providing enough assimilable nitrogen for yeast to grow. Moreover, yeast could decrease assimilable nitrogen consumption with increasing the initial reducing sugar concentration.
Virulence Gene Expression of Listeria monocytogenes Grown in Salmon Matrix
ZHU Yahui, ZHU Hongri, WANG Jiaying, ZHANG Gongliang, HAO Hongshun, HOU Hongman
2018, 39(2):  138-143.  doi:10.7506/spkx1002-6630-201802022
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The aim of the present study was to assess the influence of storage temperature on virulence gene expression of Listeria monocytogenes (Lm) grown in a food matrix. Lm ATCC 19115 was grown in a salmon matrix or tryptone soya agar containing 0.6% yeast extract (TSA-YE) (control) at different temperatures (0, 4 and 7 ℃) for 24 and 48 h, respectively. Then, the bacterial cells were collected by centrifugation for RNA extraction using a commercial kit (TianGen, Dalian), and the expression levels of hlyA, inlB, prfA and sigB were assessed by RT-qPCR. The RT-qPCR data showed that the expression of all four major virulence genes was up-regulated when the strain was grown in a salmon matrix compared to TSA-YE at each temperature. In addition, hlyA possessed the highest expression level among these four genes. The expression levels of prfA and sigB in Lm from salmon stored at 4 ℃ were significantly higher than those at 0 and 7 ℃ (P < 0.01). The expression levels of inlB and hlyA in salmon stored for 24 h at different temperatures were in the descending order of 7 ℃ > 4 ℃ > 0 ℃ (P < 0.01). In the salmon matrix, the expression levels of all four major virulence genes at 48 h were significantly higher than those at 24 h (P < 0.01). The results of this study can provide basic information for risk assessment and control of Lm in food matrices.
Heterologous Expression of the Bacillus tequilensis L-Aspartate α-Decarboxylase in Escherichia coli and Its High Cell Density Fermentation
FAN Xueping, FENG Zhibin, FANG Meifang, ZHANG Juan, CHEN Guozhong, LI Lina
2018, 39(2):  144-150.  doi:10.7506/spkx1002-6630-201802023
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L-aspartate α-decarboxylase is an important industrial enzyme which can stereo-selectively transform L-aspartate acid into β-alanine. In the present study, we cloned and expressed the L-aspartate α-decarboxylase gene (panD) from Bacillus tequilensis to construct an L-aspartate α-decarboxylase-producing Escherichia coli strain and optimized the culture conditions for high cell density fermentation. Using the genome of B. tequilensis PanD37 as template, the panD gene was amplified, and the recombinant plasmid pET32a(+)-panD was constructed and transformed into E. coli BL21(DE3) for expression. For high cell density growth and efficient L-aspartate α-decarboxylase expression, the optimum fermentation conditions in shake flasks were determined as follows: a pH-stat fed-batch culture was performed using glucose as the carbon source at an initial concentration of 5 g/L; after 8 h of culture at 37 ℃, isopropyl-β-D-thiogalactopyranoside (IPTG) was added to a final concentration of 0.5 mmol/L as an inducer and the temperature was reduced to 26 ℃. Maximum L-aspartate α-decarboxylase activity of 1 109.8 U/mL and OD600 nm value of 106.3 were obtained when the fermentation was carried out in a 5 L fermentor. Whole-cell catalysis of 100 g/L L-aspartate gave a molar conversion rate of 99.2% after 10 h of reaction. This work can provides a promising basis for further application of L-aspartate α-decarboxylase in industrial β-alanine production.
Mining of New Specific Molecular Targets and Development of a PCR Assay for Specific Detection of Salmonella Paratyphi A
ZHAI Ligong, WANG Junying, ZHANG Xiaoyu, MENG Xin, CUI Bao, ZHAO Wanqing, NIU Ping
2018, 39(2):  151-157.  doi:10.7506/spkx1002-6630-201802024
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In this study, four serotype-specific genes of Salmonella Paratyphi A were identified by comparative genomics and PCR. A PCR assay based on the gene_3105 and invA gene was developed and evaluated for the detection of S. Paratyphi A. The electrophoresis pattern showed only two bright specific bands at 284 bp and 384 bp in S. Paratyphi A. The PCR protocol was optimized and the specificity, sensitivity, anti-jamming capability and limit of detection (LOD) for artificially contaminated food were evaluated.The specificity results showed two bright specific bands for S. Paratyphi A, only one specific band at 284 bp for other Salmonella serotypes, no specific bands for non-Salmonella strains. The sensitivity of the PCR assay was 32.4 pg/μL and 4.3 × 103 CFU/mL for genomic DNA and pure colonies, respectively. In the presence of natural background flora enriched from chicken and pork breast samples, the detection limit was 6.43 × 104 CFU/mL. In artificially contaminated chicken and pork, the detection limit was N CFU/25 g after 10 h enrichment (0 < N < 10). In conclusion, the PCR assay for the detection of S. Paratyphi A is specific and sensitive, and has a good application value and can be widely used in the field of food safety.
Impact of Specific IgY on the Interaction between Tyrosinase and Its Substrate Analyzed by Surface Plasmon Resonance
SHI Peiyu, CAO Limin, LIN Hong, SUI Jianxin
2018, 39(2):  158-162.  doi:10.7506/spkx1002-6630-201802025
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Aim: Surface plasmon resonance (SPR) was used to investigate the impact of specific egg yolk immunoglobulin (IgY) on the interaction between tyrosinase and its substrate L-dopa. Methods: Bare gold chip was modified by self-assembly. 3-Mercaptopropionic acid (MPA) was used as the basement membrane to immobilize tyrosinase, and the SPR response signals of tyrosinse binding to specific IgY and L-dopa were monitored in real time. The CLAMP software was used to fit the experimental data to determine the kinetic constants. Results: The affinity constant of tyrosinase to specific IgY (4.50 × 106 L/mol) was higher than that to L-dopa (4.95 × 103 L/mol), and after binding to specific IgY, the binding constant between tyrosinase and L-dopa was decreased significantly. Conclusion: Compared with the substrate L-dopa, tyrosinase was more likely to specifically bind to IgY, and the specific IgY could significantly inhibit the binding of tyrosinase to its substrate and consequently inhibited the enzyme activity on the basis of binding kinetics.
Identification of Six Eel Species Using Polygenic DNA Barcoding
CHEN Wenbing, SHAO Biying , MIAO Tingyu, PENG Juan, CHEN Bin, ZHANG Zhideng, JIANG Shuxun
2018, 39(2):  163-169.  doi:10.7506/spkx1002-6630-201802026
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This paper develops an accurate method to identify six eel species including Anguilla rostrata, A. anguilla, A. japonica, A. mossambica, A. marmorata, and A. bicolor pacifica using polygenic DNA barcoding. Three pairs of universal primers were used to amplify partial fragments of the 16S rRNA, Cyt b and COⅠgenes of the eel species with the total genomic DNA from eel as a template and the amplified products were sequenced. As a result, 16S rDNA (638–643 bp), Cyt b (464–466 bp) and COⅠ(705–707 bp) gene fragments were obtained for each species. Homologous sequences of these genes were found. Three new primer pairs were designed to amplify 638–643, 400 and 609 bp fragments of the 16S rRNA, Cyt b and COⅠ genes by PCR, respectively. The specific 16S rRNA, Cyt b and COⅠfragments of 262, 280 and 300 bp were selected as standard DNA barcodes for the identification of eel species. Homology analysis was performed using DNAMAN software (version 6) and the homology for species discrimination was developed by aligning the DNA barcodes with the GenBank database. Analysis of 30 samples from six eel species by the developed method showed that the species were consistently identified using the DNA barcodes. In conclusion, the method is stable, precise and easy to operate and can be applied to the identification of six species of eels.
Screening and Identification of a Strain with Broad-Spectrum Antimicrobial Activity and Isolation and Purification of Antimicrobial Protein
ZHAO Shengming, ZHAO Yanyan, MA Hanjun, HE Hongju
2018, 39(2):  170-176.  doi:10.7506/spkx1002-6630-201802027
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A new strain with broad-spectrum antimicrobial activity, named as HLR-13, was isolated from traditional smoked bacon from Hunan province. The cell-free supernatant produced by the strain HLR-13 showed a high inhibitory activity towards many foodborne pathogenic bacteria and fungi such as Bacillus cereus, Pseudomonas fluorescens, Mirococcus luteus, and Salmonella enteritidis. Based on its morphological, physiological and biochemical characteristics as well as 16S rDNA sequence analysis, the strain HLR-13 was identified as Bacillus subtilis subsp. spizienii. Then the antimicrobial protein produced by the strain was isolated and purified through ammonium sulfate precipitation, ion exchange chromatography (Q Sepharose FF) and gel filtration chromatography (Sephadex G-75). Sodium dodecyl sulfate- polyacrylamide gel electrophoresis (SDS-PAGE) revealed a single band and the antimicrobial protein was preliminary identified as a hypothetical protein with molecular weight of 31 494 Da by matrix-assisted laser desorption ionization time-of-flight tandem mass spectrometry (MALDI-TOF-MS/MS) analysis through comparison with NCBI non-redundant (NR) protein database. This research can provide a theoretical basis for developing new biological preservatives.
Isolation, Identification and Evaluation of Dominant Spoilage Bacteria from Vacuum-Packaged Nonrehydrated Dougan, a Chinese Traditional Rod-Shaped Soybean Product Prepared with Protein-Lipid Film
ZHENG Lijun, SHEN Guanghui, ZHANG Zhiqing, LI Chenfeng, CHEN Anjun, LI Shanshan, WU Hejun, LUO Songming
2018, 39(2):  177-184.  doi:10.7506/spkx1002-6630-201802028
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The purpose of this study was to isolate and identify the bacteria responsible for spoilage of vacuum-packaged nonrehydrated dougan (a Chinese traditional rod-shaped soybean product prepared with protein-lipid film) and to evaluate the spoilage potential of the heat-resistant bacteria. The bacteria were isolated using various selective media. The dominant spoilage bacteria were identified by morphological observation, physiological and biochemical characterization, and 16S rRNA and gyrB gene sequence analysis. The heat-resistant spoilage bacteria with higher protease-producing capacity were inoculated into sterilized dougan to evaluate the spoilage potential according to the sensory quality, textural properties, total volatile basic nitrogen (TVB-N) content, protease activity and pH of dougan. A total of 20 bacterial strains were isolated from spoiled nonrehydrated dougan, and among these isolates, 12 strains with higher protease-producing capacity could survive autoclaving at 110 ℃ for 20 min. The dougan inoculated with strains DY1a, DY1b, DY2a and DY3 showed obvious signs of spoilage after storage at 37 ℃ for 7 days. The TVB-N, protease activity and pH value of the inoculated samples were significantly higher than those of the non-inoculated control. Texture profile analysis indicated that hardness, springiness, gumminess and chewiness of the inoculated sample decreased significantly compared with control samples. All four specific spoilage bacteria belonged to the Bacillus genus. According to the TVB-N yield factors (Y (TVB-N/CFU) values), the spoilage potential of B. amyloliquefaciens DY1a was the strongest among the spoilage bacteria isolated, followed subsequently by B. amyloliquefaciens DY1b, B. subtilis DY2a and B. subtilis DY3.
Analysis of Expression Profiles of Chitinase and β-1,3-Glucanase Genes in Muskmelon Fruit Tissue Inoculated with Alternaria alternata
BAI Yujia, ZHANG Peiling, HUANG Wei, FENG Zuoshan, LI Meng
2018, 39(2):  185-191.  doi:10.7506/spkx1002-6630-201802029
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Two different disease resistance muskmelon cultivars (Jiashi and 86-1) were analyzed for the expression profiles of chitinase (CHT) and β-1,3-glucanase (GLU) genes in fruit tissues inoculated with Alternaria alternata. Lesion size was measured and the expression levels of CmCht1, CmCht2 and CmGlu genes were investigated by fluorescent quantitative PCR after subsequent storage at 7 ℃. The results revealed that lesion appeared on the 9th d after infection and expanded until the 24th day. Lesion size in 86-1 muskmelon was 1.12 times greater than in Jiashi muskmelon on the 24th day, illustrating that the latter was more resistant to infection with A. alternate than the former. During the storage period, the relative expression levels of CmCht1, CmCht2, and CmGlu genes were significantly increased, initially rising and then declining. The peak expression levels of CmCht1, CmCht2, and CmGlu genes in the cultivars appeared at intervals of 3, 6 and 3 days, respectively. Moreover, the relative expression levels of CmCht1 and CmCht2 were higher in Jiashi muskmelon than in 86-1 muskmelon during the whole storage period, while the relative expression level of CmGlu was higher in Jiashi muskmelon than in 86-1 muskmelon during 12–24 days of storage. The expression profiles of these three genes were different during the storage period. The relative expression levels of CmCht1 and CmCht2 were high during the early period suggesting that A. alternata induced CHT gene expression, whereas that of CmGlu gene was high during the middle and late period suggesting that A. alternata induced GLU gene expression. Disease resistance in muskmelon was due to the coordination of CHT and GLU expression. Therefore, Jiashi muskmelon revealed stronger disease resistance than 86-1 muskmelon, which was closely related to the expression of CHT and GLU.
Pulsed Light Mutagenesis and Screening of Bacillus subtilis for Improved Tolerance and Extracellular Enzymatic Activities of Screened Mutants
ZHAO Tianhui, ZHANG Baiqing
2018, 39(2):  192-197.  doi:10.7506/spkx1002-6630-201802030
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Pulsed light was applied to mutagenize Bacillus subtilis. The resulting mutants were screened for improved tolerance. The extracellular enzymatic activity and genetic stability of the selected mutants were analyzed and compared with those of the original strain and the differential protein expression of the original strain and the mutant strains was determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The results showed that 8 resistant mutant strains were generated under the conditions of pulse voltage of 2 450 V, distance of 5 cm and pulse number of 40. After primary and secondary screening, the mutant strains B3 and B7 with good tolerance to high temperature tolerance, acid and high concentration of bile salt were obtained. Their α-amylase activity, protease activity, lipase activity was increased by 67% and 77% (P < 0.01), 56% and 71% (P < 0.01), and 34% and 42% (P < 0.05), compared with those of the original strain, respectively. The enzymatic activity of the obtained mutants was stable (P > 0.05) and showed genetic variation. The protein expression level was different between before and after mutagenesis. These findings proved the feasibility of application of pulsed light to mutagenize B. subtilis.
Quality Changes of Dried Radish during Fermentation by Lactobacillus plantarum
LIU Zongmin, TAN Xinghe, ZHOU Hongli, WANG Feng, GUO Hongying, YAO He1,LIU Chucen, WANG Lanshu, YAN Qinwu, XU Yongbing
2018, 39(2):  198-202.  doi:10.7506/spkx1002-6630-201802031
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In order to accelerate the fermentation process, reduce nitrite content and improve product quality, Lactobacillus
plantarum L4 and B5 were used for the fermentation of dried radish and compared with natural fermentation for their effect
on the quality of fermented radish. The results indicated that the rate of pH decline during fermentation by different strains
was in the decreasing order of L4 > B5 > natural fermentation. Nitrite content increased firstly and then decreased with
fermentation time, and its peak value was (3.23 ± 0.17) mg/kg after about 22 days of fermentation with L4, and (2.04 ± 0.12)
and (3.79 ± 0.25) mg/kg after about 33 days of B5 and natural fermentation (P < 0.05), respectively. The contents of volatile
esters and free amino acid increased with fermentation time. L* and b* values decreased with fermentation time, while a*
value increased. The sensory scores of L4, B5 and natural fermentation were 88.7 ± 2.56, 81.8 ± 1.49 and 74.1 ± 3.88 at the
end of fermentation, respectively. These results suggest that L4 and B5 can shorten the production cycle and improve the
safety and quality of fermented radish, while the performance of L4 is better than that of B5.
Component Analysis
Characterization of Key Aroma Compounds in Pork from Black Pig
ZHAO Jian, WANG Meng, XIE Jianchun, WANG Tianze, XIAO Qunfei, ZHAO Mengyao, FAN Mengdie
2018, 39(2):  203-209.  doi:10.7506/spkx1002-6630-201802032
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The amino acid and fatty acid compositions of hindquarter meat from Yunan black pigs were determined. The major fatty acids were identified as oleic acid (42.89%), palmitic acid (21.62%), eicosenoic acid (8.78%), stearic acid (7.73%), palmitoleic acid (5.93%), myristic acid (5.84%) and linoleic acid (5.51%). The major amino acids were found to be glutamic acid (13.70%) and aspartic acid (8.19%). Volatile flavor components were extracted by simultaneous distillation extraction (SDE), identified by gas chromatography-mass spectrometry (GC-MS) with a polar DB-WAX column and a weakly polar DB-5 column, and evaluated by aroma extract dilution analysis?(AEDA)?combined with gas chromatography-olfactometry (GC-O) with a weakly polar DB-5 column. Based on their retention indices and through mass spectral library search, 98 compounds were identified, mainly including hexadecanal, octadecanal, nonanal, 1-hexanol, and heptadecanal. Twenty-six of these 98 compounds were identified as aroma-active compounds based on their retention indices and odor characteristics by comparison with reference standards. The key aroma compounds (log2FD ≥ 5) were found to be 2-methyl-3-furanthiol, 3-(methylthio)propanal, γ-decalactone, (E)-2-decenal, 1-octen-3-ol, (E,E)-2,4-decadienal, nonanal, (E)-2-nonenal, 3-hydroxy-2-butanone, hexanal, methanethiol, 2-furfurylthiol, dimethyltrisulfide, 2-acetyl-1-pyrroline, (E)-2-hexenal, (E)-2-heptenal, phenylacetaldehyde, and pentanal. The results of this work can provide a useful guideline for fully understanding meat flavor composition and developing meat flavorings.
Determination of Myoglobin in Chilled Beef Based on Raman Spectroscopy
ZHANG Tonggang, LUO Ruiming, LI Yalei, ZHOU Yaling
2018, 39(2):  210-214.  doi:10.7506/spkx1002-6630-201802033
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In this study, we examined the changes in the relative amounts of three chemical forms of myoglobin, deoxymyoglobin (DeoxyMb), oxymyoglobin?(OxyMb) and metmyoglobin (MetMb), in fresh beef meat stored at 4 ℃. For this purpose, one-dimensional Raman spectral data were acquired and analyzed by two-dimensional correlation analysis using 2D-shige software. The optimal formulas for the relative amounts of three chemical forms of Mb were DeoxyMb/% = (?0.305 5x + 19.570) × 100; OxyMb/% = (?2.933 9x + 154.17) × 100; and MetMb/% = (1.574 3x ? 14.369) × 100, respectively. The prediction efficiency of these formulas was in the decreasing order: MetMb > DeoxyMb > OxyMb. When the Raman frequency was 1 033–1 248 cm-1, the root mean square error of prediction of MetMb was minimum, only 4.76%. Therefore, it is feasible to determine the relative amount of myoglobin using Raman spectroscopy.
Effect of Different Harvest Times on Aroma Components of Ecolly Wines and Distillations
LI Nana, SHU Tingting, LIANG Yanying, DUAN Qi, LI Hua, WANG Hua
2018, 39(2):  215-221.  doi:10.7506/spkx1002-6630-201802034
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Purpose: This study aimed to compare the aroma components of Ecolly wines and distillations made from grapes grown in Yangling, Shaanxi and harvested at different dates for the purpose of determining the optimal harvest date for distilled wine. Methods: Ecolly grapes were harvested on August 18, August 28 and September 5, then fermented and distilled. The physicochemical properties and aroma components were determined. Results: The reducing sugar content was the highest in the grapes harvested on August 28, (193.56 ± 0.36) g/L, and the contents of all the identified phenols were the highest in the resulting wine. The total content of aroma components was the highest in the wine made from grapes harvested on September 5, which showed a high diversity. However, for distilled wine, the total content of aroma components was the highest when grapes were harvested on August 18, which were highly diverse. Conclusion: The optimal harvest date for better aroma quality of wine was September 5, while that for better aroma quality of distilled wine was August 18.
Near Infrared Spectroscopic Detection of Gluten Content in Wheat Flour Based on Spectral Pretreatment and Simulated Annealing Algorithm
SUN Xiaorong, ZHOU Zijian, LIU Cuiling, FU Xinxin, DOU Ying
2018, 39(2):  222-226.  doi:10.7506/spkx1002-6630-201802035
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This study aimed to establish a reliable predictive model for quantitative analysis of gluten in wheat flour using near infrared (NIR) spectroscopy. The optimal spectral pretreatment method combined with simulated annealing algorithm (SAA) was obtained by comparison of the partial least squares (PLS) regression models developed after different spectral pretreatments alone and combined with SAA based on their coefficient of determination (R2), root mean square error of calibration (RMSEC) and root mean square error of prediction (RMSEP). The results indicated that the stability and prediction performance of the PLS model were greatly improved by using spectral pretreatment combined with SAA, as demonstrated by an increase in R2 from 0.763 7 to 0.949 1, a reduction in RMSEC from 1.371 2 to 0.589 8, and a decrease in RMSEP from 1.450 2 to 0.534 1. The combination of spectral pretreatment and SAA was feasible for the development of a predictive model for quantitative analysis of gluten. Moreover, the optimized model exhibited better stability and prediction performance than the unoptimized model and the one developed with spectral pretreatment alone.
Effect of Combined Thermal and High Pressure Treatment on Flavor of Pork
HUANG Yechuan, LI Tingting, GONG Daokai, LI Feng
2018, 39(2):  227-232.  doi:10.7506/spkx1002-6630-201802036
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To investigate the effect of combined thermal and high-pressure treatment on the flavor of pork, Longsissimus dorsi muscles were treated in the pressure range of 200–600 MPa and the temperature range of 20–60 ℃ for 10 min. Then the volatile compounds and flavor characteristics of samples were analyzed by gas chromatography-mass spectrometry (GC-MS) and electronic nose, respectively. The results showed that a total of 141 volatile flavor compounds were identified in different samples, including aldehydes, ketones, alcohols, esters, acids and alkanes. Compared with the control group, both the number of compounds and the total peak area of the treated samples were increased, and the total peak area was increased with increasing temperature or pressure, which was mainly resulted from aldehydes, ketones and alcohols. Partial least squares regression (PLSR) analysis showed that the effect of pressure on the flavor was larger than that of temperature; the more drastic the treatment conditions were, the more significantly the flavor was changed. The results of electronic nose showed that the samples treated at 600 MPa had a very different flavor from that of other samples. Thus, pressure should be controlled at around 400 MPa when pork is treated with high pressure, and pork flavor was little affected at temperatures below 60 ℃.
Effects of Geographical Environment and Genotype on Nutritional Contents, Texture and Microstructure of Auricularia auricula-judae
ZHANG Yanlong, MU Yue, LI Yuanjing, WAN Peng, FENG Lei, LEI Hong
2018, 39(2):  233-239.  doi:10.7506/spkx1002-6630-201802037
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In this paper, we investigated differences in the nutritional contents, texture and microstructure of Auricularia auricula-judaes from Tibet and Dongning of Heilongjiang province. The results indicated that total sugar, reducing sugar, fiber and fat contents of A. auricula-judaes were significantly affected by genotype, while the unique geographical environment of Tibet influenced the accumulation of mineral elements, such as calcium, iron, zinc and magnesium, and functional compounds, such as polyphenols, flavonoids and melanim. Principal component analysis (PCA) and hierarchical clustering analysis demonstrated that environmental factors had a greater impact on the nutritional contents than genotype. Along with the changes in nutritional contents, geographical environment influenced the springiness, cohesiveness, gumminess, chewiness, and resilience, while genotype influenced only the hardness of A. auricula-judae. Electron microscopy analysis demonstrated that different A. auricula-judae strains from Tibet had similar morphology, while significant morphological differences were observed between A. auricula-judaes cultivated in Dongning and Tibet. These results suggested that the differences in the nutritional contents and texture properties in A. auricula-judae depend more heavily on environmental factors and less on the genetic background. This study can provide an important guidance for A. auricula-judae cultivation and for further studies on the underlying physiological and molecular mechanism.
Processing Technology
Preparation of Daidzein and Genistein by Demethylation Reaction and Their Antioxidant Activity
ZHANG Xiaosong, JIN Hua, YAN Huili, ZHANG Yongzhong, XU Jing
2018, 39(2):  240-246.  doi:10.7506/spkx1002-6630-201802038
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Daidzein and genistein were derived from the demethylation of formononetin and biochanin A in KBr-H3PO4 or KI-H3PO4 solution, respectively. The antioxidant activities of daidzein and genistein were also evaluated. The optimal conditions for preparing daidzein in KBr-H3PO4 solution were determined as follows: reaction time 5 h, reaction temperature 120 ℃, ratio of solid to solvent 1:45 (g/mL), and degree of saturation 75%, providing maximum reaction yield of 89.42%, while those for preparing genistein were 5 h, 120 ℃, 1:45 (g/mL), and 100%, providing maximum reaction yield of 85.98%; the optimal conditions for preparing daidzein in KI-H3PO4 solution were determined as 4 h, 100 ℃, 1:15 (g/mL) and 75% for reaction time, temperature, ratio of solid to solvent and degree of saturation, respectively, providing maximum reaction yield of 87.03%, while those for preparing genistein were 5 h, 100 ℃, 1:45 (g/mL) and 75%, respectively, providing maximum reaction yield of 88.51%. Compared with the traditional synthesis methods, the proposed method in this study had many advantages such as simpler reaction process, milder reaction conditions, shorter reaction time and higher yield. The daidzein and genistein had 1,1-diphenyl-2-picryl-hydrazyl and hydroxyl radical scavenging ability and a potent inhibitory effect on linoleic acid oxidation suggesting good antioxidant activity.
Optimization by Response Surface Methodology and Kinetics of Extraction of Polyphenols from Chinese Prickly Ash
GUO Hongyao, LI Dong, LEI Xiong, WANG Xiaojing, GANG Yong, LI Wenhong
2018, 39(2):  247-253.  doi:10.7506/spkx1002-6630-201802039
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The extraction of polyphenols from Chinese prickly ash was optimized for increased yield of polyphenols. The influence of temperature, extraction time, solvent concentration, solid-to-solvent ratio and pH on extraction efficiency was investigated initially by one-factor-at-a-time method. Using the Box-Behnken response surface methodology, the optimum extraction conditions were obtained as follows: 48.23% (V/V) acidified ethanol (pH 3) as extraction solvent, solid-to-solvent?ratio 1:29.34 (g/mL), temperature 48.99 ℃, and extraction time 1.75 h. Under these optimized conditions, the average yield of polyphenols reached 55.06 mg/g (n = 5). In addition, the mass transfer kinetics during the extraction of polyphenols at different temperatures was investigated. Based on Fick’s first law of diffusion, a kinetic equation was established with the plate model. The key model parameters, including rate constant, relative extraction rate and activation energy, were obtained. These results could provide a theoretical basis for industrial extraction and further study of polyphenols from Chinese prickly ash.
Ultrasonic-Assisted Enzymatic Extraction and Thermal Stability of Collagen from Soft-Shelled Turtle Calipash
ZOU Ye, CAI Panpan, WANG Li, WANG Daoying, ZHOU Tao, XU Weimin
2018, 39(2):  254-259.  doi:10.7506/spkx1002-6630-201802040
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In the current study we optimized the ultrasonic-assisted enzymatic extraction of collagen from soft-shelled turtle calipash. One-factor-at-a-time method was used to investigate four factors affecting the extraction efficiency including enzyme dosage, ultrasonic time, ultrasonic power and solid-to-solvent ratio. Subsequently, a mathematical model with enzyme dosage, ultrasonic time and ultrasonic power as independent variables was established by Box-Behnken design. Meanwhile, we compared the thermostability of collagen extracted by routine enzymatic extraction and ultrasound-assisted enzymatic extraction. The optimal extraction conditions that provided the maximum collagen yield (74.50%) were determined as follows: 0.5 mol/L acetic acid as the extraction solvent, solid-to-liquid ratio 1:20 (g/mL), enzyme dosage 0.8%, ultrasonic time 43 min, and ultrasonic power 176 W. The results of differential scanning calorimetry showed that the thermostability of collagen extracted by the modified method was better than that of collagen prepared by conventional enzymatic extraction. The results of this study can provide a basis for intensitive processing and application of collagen from soft-shelled turtle calipash.
Optimization of Microwave-Assisted Aqueous Enzymatic Extraction of Cyclic Adenosine 3’,5’-Monophosphate (cAMP) from Chinese Jujube (Ziziphus jujuba Mill.) and Its Anti-Fatigue Effect
REN Yanrong, ZHANG Zhongming, XIE Yuejie, XIONG Zhengwei, WANG Zhongming, WU Hongbin
2018, 39(2):  260-266.  doi:10.7506/spkx1002-6630-201802041
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Response surface methodology was used to optimize the microwave-assisted aqueous enzymatic extraction of cyclic adenosine 3’,5’-monophosphate (cAMP) from Chinese jujube (Zizyphus jujuba Mill.) grown in Xinjiang. The anti-fatigue effect of the cAMP extracted was investigated. The optimal extraction conditions was found as follows: enzyme concentration 1.5% (a mixture of cellulase, hemicellulase and pectinase, 1:1:1 (m/m)), temperature 31.3 ℃, time 20 min and microwave power 500 W. Under these conditions, the yield of cAMP was 560.9 μg/g. The results showed that the cAMP could extend exhaustive swimming time and enhance swimming endurance in mice, suggesting good anti-fatigue effect. Therefore, cAMP holds great promise for its application in the food and pharmaceutical industry.
Optimization of Extraction and Characterization of Protein from Allium cepa L. var. agrogatum Don
LIU Tingting, LIU Yang, ZHANG Jing, SONG Yunyu, LI Guijie, ZHANG Yanrong
2018, 39(2):  267-272.  doi:10.7506/spkx1002-6630-201802042
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The extraction of protein from Allium cepa L. var. agrogatum Don by alkali dissolution and acid precipitation was optimized using orthogonal array design method. Along with this, the extracted protein was also characterized. The results showed that the maximum extraction efficiency of protein of 79.38% was obtained after extraction at 50 ℃ and pH 9.0 with a solid-to-solvent ratio of 1:15 (g/mL) for 1.5 h. HPLC analysis demonstrated that the protein consisted of 38.96% essential amino acids and 61.04% non-essential amino acids. Electrophoresis showed that the protein was composed of four components with molecular weights of 61.94, 27.10, 17.62, and 13.34 kDa. The secondary structure consisted of 52.60% α-helix, 8.60% β-sheet, 15.60% β-turn and 22.40% random coil. The characteristic functional groups of the protein were confirmed by infrared spectroscopy.
Optimization of Extraction of Polysaccharide from Dendrobium officinale and Its Antioxidant Effect on Drosophila melanogaster
QIU Xianchuang, ZHAO Ning, LI Chen, WANG Jingxue
2018, 39(2):  273-280.  doi:10.7506/spkx1002-6630-201802043
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The ultrasonic-assisted extraction of polysaccharide from Dendrobium officinale at a 250 W low power was optimized by response surface methodology based on central combination design. Extraction temperature, solvent-to-solid ratio, and ultrasonic treatment time were considered as independent variables. The optimum extraction conditions were determined as follows: extraction temperature 41.74 ℃, solvent-to-solid ratio 50.26:1 (mL/g), and ultrasonic treatment time 28.65 min. Under these conditions, the maximum extraction yield of 25.39% was obtained, which was increased by 18% compared with the value obtained using conventional hot water extraction with a simultaneous reduction in extraction time of 75%. Moreover, the DPPH and hydroxyl radical scavenging activities of polysaccharide from D. officinale were not reduced during ultrasonic-assisted extraction. Drosophila melanogaster were fed with different doses of the extracted polysaccharide, and the results showed that the polysaccharide at moderate dose provided the best antioxidant activity as evidenced by a 30% increase in superoxide dismutase (SOD) and catalase (CAT) activity and a 46% decrease in malondialdehyde (MDA) content of male D. melanogaster, as well as an increase of 60% in CAT activity and 6% in SOD activ ity and a 20% decrease in MDA content of female D. melanogaster, extending the lifespan by an average of 20%.
Safety Detection
Prediction Model for Typical Alcohols in Base Liquor Based on Near Infrared Spectroscopy
LIU Jianxue, YANG Guodi, HAN Sihai, LI Xuan, LI Peiyan, XU Baocheng
2018, 39(2):  281-286.  doi:10.7506/spkx1002-6630-201802044
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In this paper, the contents of n-propanol, n-butanol, amyl alcohol and isoamyl alcohol in base liquor were determined by gas chromatography and used as chemical values for the establishment of calibration and validation?sets for a rapid predictive model based on near infrared spectroscopy (NIR) to measure typical alcohols in base liquor. The model was developed using partial least squares (PLS) regression with internal cross validation and optimized. The optimal spectral pretreatment method and the optimal spectral region were determined. The coefficients of determination (R2) between the actual and the NIR predicted values of n-propanol, n-butanol, amyl alcohol and isoamyl alcohol for the calibration set were 0.952, 0.981, 0.963 and 0.981, and the root mean square error of cross-validation (RMSECV) were 0.27, 0.49, 0.101 and 0.67 mg/100 mL, respectively; the R2 values for the validation set were 0.947, 0.980, 0.928 and 0.952, and RMSEPs were 0.40, 0.81, 0.49 and 1.35 mg/100 mL, respectively. Results showed that the predictive model exhibited good accuracy, stability and prediction performance and could provide a new approach for the analysis of alcohols in base liquor.
Analysis of Virus Diversity in Drinking Source Water by Using Illumina MiSeq Sequencing Technology
GE Yingliang, YU Shuili, SHI Wenxin
2018, 39(2):  287-292.  doi:10.7506/spkx1002-6630-201802045
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The viruses in drinking source water from east Tai Lake were separated and concentrated by gradient-series connection-circulation-tangential flow ultrafiltration (GSC-TFF). The viral genome was amplified by sequence independent single primer amplification (SISPA), sequenced by Illumina Miseq, and compared with the NCBI gene database using the basic local alignment search tool (BLAST). After quality control, 1 190 914 928 bp gene data were obtained, which could be assembled into 5 554 scaffold sequences. Viral genome function was found and annotated to Caudovirales, Herpesvirales and Ligamenvirales at the family level. A total of 40 families of homologous sequences were annotated, Microviridae (27.590 1%), Siphoviridae (23.010 7%), Phycodnaviridae (5.322 2%), Retroviridae (1.691 2%), Mimiviridae (1.960 8%) being the dominant ones. A total of 102 112 reads (21.572 8%) were identified as no rank at the family level. The approach proposed in this study can allow high throughput analysis of virus diversity in source water, paving the foundation for?detecting virus in water.
Rapid Determination of Synthetic Pigments in Fruit-Flavored Beverage by Near Infrared Spectroscopy
TIAN Jing, LI Qiaoling
2018, 39(2):  293-297.  doi:10.7506/spkx1002-6630-201802046
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A rapid method based on near infrared (NIR) spectroscopy was developed for the determination of synthetic pigments in fruit-flavored beverage. NIR spectra of sunset yellow, tartrazine, ponceau 4R and amaranth solutions at different concentrations were recorded in the wavenumber range of 1 100–1 650 nm at a 0.2 nm interval, respectively and preprocessed by first derivative and second derivative. The modified partial least square (MPLS) regression models were established after spectral preprocessing by standard normal variate (SNV) + detrending and applied to predict the synthetic pigment contents in beverage. The results showed that the maximum correlation coefficient of prediction (Rp) was 0.991, the minimum standard error of prediction (SEP) was 0.009%, and the maximum standard deviation ratio (SDR) was 3.51. Accordingly, NIR spectroscopy can be used as a simple, rapid, nondestructive and reliable method to determine the contents of synthetic pigments in beverage.
Migration of Fluorescent Whitening Agents from Polyethylene Food Packaging Materials
ZHANG Yun, Lü Shuiyuan, ZHANG Xinren, LIN Jing
2018, 39(2):  298-302.  doi:10.7506/spkx1002-6630-201802047
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The migration of fluorescent whitening agents from polyethylene (PE) food packaging films into water, acetic acid, ethanol, and vegetable oil was investigated using high performance liquid chromatography (HPLC). The dissolution of fluorescent whitening agents was studied as a function of food contact medium, acetic acid concentration, ethanol concentration, soaking temperature and time. The results showed that coumarin-containing fluorescent whitening agent could be dissolved by the aqueous food simulant, and the effect was weaker than that of the acidic food stimulant. The alcoholic and fatty food simulants could better dissolve most fluorescent whitening agents in a concentration-dependent manner. The migration of fluorescent whitening agents in plastic packaging materials was significantly promoted at higher temperature. Moreover, the possibility of migration of fluorescent whitening agents from plastic packaging materials into the foods increased with contact time.
Determination of Eight Antiviral Drug Residues in Animal-Derived Food by Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry
ZHANG Yingying, LI Huichen, WU Yanchao, LI Yingying
2018, 39(2):  303-309.  doi:10.7506/spkx1002-6630-201802048
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An efficient ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was established for the simultaneous analysis of residues of 8 antiviral drugs (arbidol, amantadine, rimantadine, famciclovir, peramivir, imiquimod, oseltamivir, and lamivudine) in chicken meat and liver and pork meat and liver. Samples were extracted with 1% formic acid-acetonitrile, and the extract was subjected to chromatographic separation on MCX solid-phase extraction column. Quantification of the analytes was achieved by UPLC-MS/MS using the internal standard method. The limit of detection (LOD) and limit of quantification (LOQ) of the method were lower than 1.0 and 3.0 μg/kg for all the antiviral drugs, respectively. The average recoveries of 8 antiviral drugs in blank chicken meat, pork meat, chicken liver and pork liver at spiked levels of 5.0, 10.0, and 20.0 μg/kg ranged from 70% to 120%, with relative standard deviation (RSD) of less than 10%. The method had the advantages of small matrix interference, high sensitivity and good recovery. Therefore, it can be used for the detection of antiviral drugs residues in animal-derived food.
Accumulation Characteristics and Safety Evaluation of Heavy Metals in Four Kinds of Aquatic Products from Lake Taihu
ZHANG Xiaowen, SHAO Liuyi, LIAN Bin
2018, 39(2):  310-314.  doi:10.7506/spkx1002-6630-201802049
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In order to investigate the current status of heavy metal pollution and food safety of aquatic products from Lake Taihu, atomic absorption spectrophotometry (AAS) was used to determine the contents of Pb, Cd, Cu, and Zn in the head, muscle and viscera of farmed and wild aquatic products. The results showed that the distribution patterns of heavy metals in different parts of aquatic products were quite different. Heavy metals were mainly distributed in the head and viscera of all investigated aquatic products except wild crucian carp (Carassius auratus). The contents of heavy metals in each part of aquatic products generally decreased in the following order: Zn > Cu > Pb > Cd. The levels of heavy metal pollution in the muscle tissue of farmed and wild aquatic products were different, with higher levels being found in the muscle tissue of wild aquatic products. Furthermore, the content of each heavy metal in muscle tissue were also different among different kinds of aquatic products, with both farmed and wild Metapenaeus ensis having the strongest Cu accumulation capacity while wild crucian carp having the strongest Zn accumulation capacity. The heavy metal pollution in the muscle tissue of aquatic products from Lake Taihu was generally at slight levels, and only a few of them were seriously polluted with heavy metals. The main pollution factors were Pb and Zn.