Volume 33,Issue 9,2017 Table of Contents

1 Effects of n-Hexane Extract of Green Garlic on H22 Tumor-bearing Mice

LIU Wei , WANG Jing-ya , CHEN Hai-xia

2017, 33(9):1-7. DOI: 10.13982/j.mfst.1673-9078.2017.9.001

[Abstract](827) [HTML](227) [PDF 590.22 K](900)

Abstract:
To study the antitumor effects of the hexane extract derived from 75% ethanol green garlic extract (hereafter referred to as green garlic n-hexane extracts: GGHE) and its effect on immune function in H22 tumor-bearing mice, H22 transplanted mouse models were established. Sixty mice were divided into six groups: blank control group, model group, positive control (cyclophosphamide (CTX): 20 mg/kg), and low-, medium-, and high-dose GGHE (L-GGHE: 75 mg/kg, M-GGHE: 150 mg/kg, and H-GGHE: 300 mg/kg) groups. The drugs were continuously administered for 14 days. Mouse body weight; food/water intake; the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), alanine transaminase (ALT), and aspartate aminotransferase (AST); and the content of malondialdehyde (MDA) in liver tissue were determined. Moreover, the levels of tumor necrosis factor (TNF)-α, interleukin (IL)-2, and vascular endothelial growth factor (VEGF) in serum were detected. The food and water efficiency, tumor volume, tumor inhibition rate, and spleen and thymus indices were calculated. The pathological characteristics of tumor tissues were also analyzed. The results showed that the tumor growth inhibition rate of M-GGHE was 71.48%. Compared with the model group, the treatment with GGHE significantly increased the food and water efficiency rate, spleen and thymus indices, increased the levels of IL-2 and TNF-α; reduced the level of VEGF; increased the activities of SOD, GSH-Px, and CAT, and decreased the MDA content as well as the activities of ALT and AST. In conclusion, GGHE exhibited antitumor effects on H22 tumor-bearing mice, improved their quality of life, and improved the antioxidant level and immune function. The results suggest that GGHE could be used as a candidate drug for treating hepatocellular carcinoma.

2 Effect of Sea Buckthorn Powder on Hepatic Lipid Metabolism and Oxidative Stress in Rats

DU Juan , XI Yan-li , SONG Chun-mei

2017, 33(9):8-12. DOI: 10.13982/j.mfst.1673-9078.2017.9.002

[Abstract](968) [HTML](304) [PDF 364.20 K](877)

Abstract:
The effects of sea buckthorn powder on the hepatic lipid metabolism and oxidative stress in rats were studied in this paper. Fifty male Wistar rats were randomly divided into five groups: the control group; the high fat/cholesterol diet group; and sea buckthorn powder low-, medium-, and high-dose groups. The control group was fed with basal diet, and other groups were fed with high fat/cholesterol diet during the experiment. The rats in both control and high fat/cholesterol diet groups were given distilled water, and those in low-, medium-, and high-dose treated groups were given sea buckthorn powder at doses of 0.5 mg/g?body weight (bw), 2.5 mg/g?bw, and 5 mg/g?bw, respectively. The animals were sacrificed after four weeks, and livers were collected to measure the liver lipid content, lipid metabolism-related enzyme activity, and oxidative stress level. The results indicated that compared with the high fat/cholesterol diet group, sea buckthorn powder reduced the levels of hepatic total cholesterol (TC), total triglyceride (TG), and malondialdehyde (MDA), and increase the levels of high density lipoprotein-cholesterol (HDL-C) and glutathione (GSH) and the activities of hepatic lipase (HL), lipoprotein lipase (LPL), and total superoxide dismutase (T-SOD). These results demonstrated that sea buckthorn powder could reduce the liver lipid levels, improve lipid metabolism enzyme activities in the liver, increase antioxidant capacity, and slow down lipid peroxidation in hepatocytes of high-fat diet-fed rats.

3 Exploration of the Involvement of the S2P Protease Slr1821 of Synechocystis sp. PCC6803 in Heat Stress Response

CHEN Gu , LI Shi-liang , LIU Xiao-fang , LIN Shi-qi , DING Qing-long

2017, 33(9):20-27. DOI: 10.13982/j.mfst.1673-9078.2017.9.004

[Abstract](817) [HTML](194) [PDF 854.38 K](1171)

Abstract:
With the rising emission of carbon dioxide(CO2), the greenhouse effect is becoming increasingly obvious, and global warming has caused more severe damage to the growth of crops and the ecological environment. Thus, investigation of the response mechanism of photosynthetic autotrophs to heat stress is of scientific significance and has potential applications. Synechocystis sp. PCC6803 is a model cyanobacterium used to study photosynthesis and the response to abiotic stress. In this paper, the coding gene of the site-2-protease Slr1821 of Synechocystis sp. PCC6803 was knocked out completely by homologous recombination to generate the Δslr1821 mutant. The results showed that after heat treatment at 44 ℃, the Δslr1821 mutant could not grow at all, whereas the wild-type recovered from thermal damage quickly, indicating that Slr1821 protein played an important role in heat acclimation. Through analysis of changes in the relative content of phycobiliprotein and the content of chlorophyll, the results showed that heat treatment-induced deficiency of slr1821 inhibited the resynthesis of photosynthetic pigments, including phycobiliprotein and chlorophyll. These findings provide important insights into analysis of the mechanisms through which photosynthetic autotrophs adapt to heat stress.

4 Antimicrobial Mechanisms of the n-Butanol Phase from Tea Mistletoe Viscum articulatum Burm.F. Ethanol Extracts Against Staphylococcus aureus

LI Juan , XUE Qiao-li , XIAO Rong , LIN Qi , XU Zhi-qiang , HU Yong-jin

2017, 33(9):28-36. DOI: 10.13982/j.mfst.1673-9078.2017.9.005

[Abstract](1047) [HTML](224) [PDF 775.28 K](1280)

Abstract:
The antibacterial activity of each phase from tea mistletoe Viscum articulatum Burm.F. ethanol extracts and the antibacterial mechanism of the n-butanol phase from V. articulatum Burm.F. ethanol extracts (NVBEs) against Staphylococcus aureus were studied. The antibacterial activities of each phase from V. articulatum Burm.F. ethanol extracts against food spoilage and pathogenic bacteria, including Staphylococcus aureus, Escherichia coli, Salmonella typhimurium, and Listeria monocytogenes, were determined by measuring the diameter of inhibition zone (DIZ) using the disc diffusion method, the minimum inhibitory concentration (MIC), and the minimum bactericidal concentration (MBC), as measured using a doubling dilution series. Furthermore, the antibacterial mechanism of NVBEs was explored using light microscopy, scanning electron microscopy, cell membrane permeability and integrity analysis, and enzyme activity assays. The results showed that each phase from V. articulatum Burm.F. ethanol extracts had significant antagonistic activity against four food-spoilage and pathogenic bacteria. Moreover, NVBEs showed relatively strong antibacterial activity, and the strongest antibacterial effect was observed for Staphylococcus aureus. The DIZ, MIC, and MBC values were 9.84 ± 0.57 mm, 3.52 mg/mL, and 7.04 mg/mL, respectively. The results showed that the NVBEs increased the permeability of the bacterial cell wall and membrane, destroyed the bacterial cell structure, and caused leakage of cellular contents, such as nucleic acids and proteins. The genetic material was altered, the cell morphology appeared to be abnormal, and the enzyme metabolic activity was affected, thus inhibiting bacterial growth.

5 Dissolution Behavior and Structural Changes of Silk Fibroin in Calcium Chloride-Ethanol-Water Solvent Systems

CHEN Jia-hong , JIANG Hong-rui , YU Lian , WANG Cheng-hua , ZHAO Mou-ming , LIU Xiao-ling

2017, 33(9):37-45. DOI: 10.13982/j.mfst.1673-9078.2017.9.006

[Abstract](1245) [HTML](582) [PDF 868.00 K](1487)

Abstract:
Conditions for the transformation of insoluble silk fibroin into soluble regenerated silk fibroin and the effect of structural changes in silk fibroin on its solubility were examined to enable preparation of soluble silk fibroin for use in food products. The effects of solvent system, temperature, salt concentration, and ethanol concentration on the dissolution of silk fibroin, as assessed by dissolution time and the nitrogen solubility index of the regenerated silk fibroin, were analyzed. The results showed that insoluble silk fibroin could be dissolved in calcium chloride-ethanol-water systems; soaking of silk fibroin in a solution of 4 mol/L calcium chloride and 30% (V/V) ethanol and heating at 95 ℃for 9 min led to complete dissolution, and the nitrogen solubility index of the regenerated silk fibroin reached 91%. Structural changes in silk fibroin upon dissolution were also examined using low-field nuclear magnetic resonance (NMR) spectroscopy, circular dichroism spectroscopy, X-ray diffractometry, and scanning electron microscopy. In the calcium chloride-ethanol-water system, interactions between silk fibroin and water gradually increased in strength, the silk fibroin fibers swelled and gradually broke into a lamellar shape, and the crystal structure of the silk fibroin was destroyed. In solution, the structure of the regenerated silk fibroin changed from a β-sheet structure to a random coil structure, resulting in an improvement in solubility.

6 Structure and Activity of Sulfide:Quinone Oxidoreductase and Its Mutants from Thiobacillus denitrificans ATCC25259

CHEN Xin , MENG Zhi-zhong , LUO Yi , RONG Xiang , LI Shan

2017, 33(9):46-55. DOI: 10.13982/j.mfst.1673-9078.2017.9.007

[Abstract](739) [HTML](243) [PDF 866.51 K](1144)

Abstract:
The wild-type protein and mutant protein models of sulfide:quinone oxidoreductase (SQR) from Thiobacillus denitrificans ATCC25259 were generated by homology modeling using Discovery Studio 3.5. All models were optimized by molecular mechanics and molecular dynamics using GROMACS 5.1.2, yielding protein models in a stable state with a relatively low energy. Three methods, i.e., PROCHECK, Verify 3D, and ProSA, were used to evaluate the models, and the results indicated that the models were reasonable and reliable. The protein models were used to calculate the interactions between proteins and ligands, as well as the solvent accessible surface (SAS) and energy values. The expression vectors of SQR and mutants were constructed and transferred into Escherichia coli BL21 (DE3) to express the proteins with a molecular weight of about 65 ku. Several wild-type and mutant proteins containing the 6× His tag were purified by nickel-affinity chromatography. The SQR enzyme activity was determined using established methods, and the results showed that the activity of the mutants was lower than that of the wild-type SQR. Both simulation calculations and experimental verification suggested that the structural stability of the alpha helix in the C-terminal of SQR had an important influence on the structural stability of the protein. If the structural stability of the protein decreased, the enzyme activity also decreased.

7 Inhibitory Effect of Polysaccharides from Pholiota adiposa on Tumor Cell Proliferation

ZHOU Cong , SUN Yue , LI De-hai , GU Jia-lin , GONG Jin-hua

2017, 33(9):56-62. DOI: 10.13982/j.mfst.1673-9078.2017.9.008

[Abstract](927) [HTML](194) [PDF 629.01 K](848)

Abstract:
To study the effects of extraction solvent acidity on the preparation of Pholiota adiposa polysaccharides (e.g., yield and purity) and their inhibitory effects on tumor cell proliferation, three types of P. adiposa polysaccharides (SPAP1, WPAP1, and JPAP1) were prepared using 0.1 mol/L HCl (aq), distilled water, and 0.1 mol/L sodium hydroxide (aq), respectively. The deproteinized P. adiposa polysaccharides (SPAP2, WPAP2, and JPAP2) were obtained from the deproteinization of SPAP1, WPAP1, and JPAP1, respectively. The effects of the extraction yield and purity of P. adiposa polysaccharides on the proliferation of tumor cells were investigated, and the differences in the structures of P. adiposa polysaccharides were preliminarily analyzed by infrared spectrometry. The result indicated that the acidity of the extraction solvent considerably impacted the extraction yield and purity of P. adiposa polysaccharides, and the highest extraction yield and the highest purity were found in JPAP1 (11.02%) and SPAP2 (73.91%), respectively. The inhibitory effect of SPAP2 on tumor cell proliferation was significantly higher than those of other P. adiposa polysaccharides (p<0.05) and dose- and time-dependent effects of polysaccharide treatment were observed. SPAP2 exhibited thestrongest inhibitory effect on the proliferation of HeLa cells, with an inhibition rate of 90.88%. Infrared spectroscopy results showed that SPAP2 had strong absorption peaks at 1078±4 cm-1 and 759.83 cm-1, which indicated that the content of C-O-H and C-O-C groups in SPAP2 were higher than those in other polysaccharides. These results may provide a theoretical basis for further development of P. adiposa polysaccharide products and an in-depth study on the mechanism of P. adiposa polysaccharide-induced tumor cell apoptosis.

8 Purification of Different Phenolic Compounds from Sorghum Bran on AB-8 Macroporous Resin and Protective Effects against Oxidative-stress-induced Erythrocyte Hemolysis

CHEN Hua-min , LAI Fu-rao , SUN Chong-zhen , ZHANG Meng-meng , WU Hui , TANG Yu-qian , LI Xiao-feng

2017, 33(9):63-70. DOI: 10.13982/j.mfst.1673-9078.2017.9.009

[Abstract](1092) [HTML](219) [PDF 746.53 K](1326)

Abstract:
Different types of phenols extracted from sorghum bran were purified on the AB-8 macroporous resin and then analyzed by high performance liquid chromatography (HPLC). The inhibitory effects of the phenols on human-erythrocyte hemolysis caused by 2,20-azobis-(2-amidinopropane) dihydrochloride (AAPH) were studied. The results showed that after purification on the AB-8 macroporous resin, phenol concentrations were in the following order: free phenols > insoluble bound esterified phenols > insoluble bound glycosidic phenols > soluble glycosidic phenols > soluble esterified phenols. According to the results of HPLC, the concentrations of 18 phenolic compounds were in the following order: insoluble bound esterified phenols > free phenols > insoluble bound glycosidic phenols > soluble esterified phenols > soluble glycosidic phenols. After the treatment with 200 μg/mL insoluble bound esterified, free, insoluble bound glycosidic, or soluble esterified phenols, the rate of AAPH-induced hemolysis of erythrocytes decreased to ~10%, which was close to that of the negative control group; the AAPH hemolysis rate of erythrocytes in the soluble glycosidic phenolic (200 μg/mL) treatment group was still 28.84%. Pretreatments with five different types of phenols effectively reduced the concentration of malondialdehyde (MDA), increased the glutathione/glutathione disulfide (GSH/GSSG) ratio in the AAPH-treated erythrocytes, and restored the erythrocytes to the normal state. The erythrocytes with relatively low superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activities were also protected. In conclusion, the different types of phenols from sorghum bran after purification on the AB-8 macroporous resin may protect human erythrocytes from the damage caused by AAPH-generated free radicals, and their intracellular antioxidant activity is related to their total phenolic content and composition of a mixture of phenolic compounds.

9 24-Epibrassinolide Enhances Disease Resistance in Apricot Fruits via Regulation of Phenylpropanoid Metabolism

LI Li-hua , ZHANG Rui-jie , YAO Yuan-li , ZHU Xuan

2017, 33(9):71-76. DOI: 10.13982/j.mfst.1673-9078.2017.9.010

[Abstract](798) [HTML](211) [PDF 532.54 K](885)

Abstract:
The effects of 24-epibrassinolide (24-EBR) treatment on disease resistance and phenylpropanoid metabolism in apricot fruits were investigated. Mature-green Xinjiang ‘Saimaiti’ apricot fruits were processed by vacuum osmotic treatment with 0.9 mg/L 24-EBR, or distilled water as a control, at a pressure of 0.05 MPa. Twenty-four hours after treatment, the apricot fruits were inoculated with Alternaria alternata and stored at a temperature of 4 ℃ and a relative humidity of 90%~95%. The phenylalanine ammonia lyase (PAL), cinnamic acid hydroxylase (C4H), and 4-p-coumaric acyl coenzyme A ligase (4-CL) activities and lignin, total phenolic, and flavonoid content of the apricot fruits were measured periodically. The disease incidence and lesion diameters of the apricot fruits were also recorded. The results showed that 24-EBR treatment significantly increased the activities of PAL, C4H, and 4-CL and the lignin and total phenolic content, increased the flavonoid content towards the end of the storage period, and decreased the disease incidence and lesion diameter of apricot fruits. These results indicate that 24-EBR treatment can enhance the resistance of fruits to postharvest disease by inducing phenylpropanoid metabolism.

10 Expression of Creatininase from Pseudomonas putida in Escherichia coli and Its Enzymatic Characteristics Analysis

HOU Gan-sheng , LIN Ying , LIANG Shu-li

2017, 33(9):77-82. DOI: 10.13982/j.mfst.1673-9078.2017.9.011

[Abstract](914) [HTML](317) [PDF 522.00 K](1230)

Abstract:
Creatininase is the key enzyme used for creatinine enzymatic detection. The Cre gene from Pseudomonas putida was cloned into the prokaryotic expression vector pET-28a (+) and expressed in the soluble form by Escherichia coli BL21 (DE3) after induction of isopropyl β-D-1-thiogalactopyranoside. The expressed product was purified and isolated using heat treatment at 60℃, nickel-nitrilotriacetic acid affinity chromatography, and Sephadex G-200 gel filtration to yield recombinant creatininase. The recovery rate was 29.3%, and the specific activity was 489.17 U/mg, which was the highest level reported to date. The enzymatic characteristics of Cre were further analyzed, and the results showed that the optimum temperature was 60 ℃. Additionally, the recombinant Cre showed good thermal stability and could be stably stored at less than 50 ℃; the optimum pH value was 7.0, and the enzyme was relatively stable at pH 7.0~8.0. The activity of Cre could be inhibited by copper (II), but significantly increased by manganese (II), zinc (II), and cobalt (II). (Ethylenedinitrilo) tetraacetic acid(EDTA), sodium dodecyl sulfate(SDS), Tween-20, Tween-80, and Triton-100 had almost no effect on Cre activity, and sodium azide did not have any effect on Cre activity. When creatine was used as a substrate, the enzyme kinetic constant Km value of Cre was 47.38 mM. In summary, the expression of the soluble form of creatininase was successfully achieved in an E. coli system, and purification and analysis of the enzymatic characteristics of the creatininase were performed, establishing a theoretical foundation for the expression and potential industrial applications of creatininase.

11 Effects of Colletotrichum musae Infection on the Postharvest Quality and Related Enzymatic Activities of Banana Fruit

LI Li , HE Xue-mei , LI Chang-bao , SUN Jian , LING Dong-ning , SHENG Jin-feng , RAO Chuan-yan , XIAO Zhan-shi , LI Jie-min , ZHENG Feng-jin , LIU Guo-ming , TANG Ya-yuan

2017, 33(9):83-90. DOI: 10.13982/j.mfst.1673-9078.2017.9.012

[Abstract](865) [HTML](278) [PDF 656.44 K](945)

Abstract:
The effects of artificial inoculation with Colletotrichum musae on the postharvest quality of banana fruit were determined. Two banana cultivars (Musa acuminata L. AAA Cavendish ‘Formosana’ and Musa spp. ABB) were inoculated with C. musae, and changes in the hardness, chlorophyll content, total soluble solid content, reducing sugar content, titratable acid content, respiration intensity, and activities of enzymes related to disease resistance (polyphenol oxidase and peroxidase) were analyzed. The results showed that fruit hardness decreased rapidly after inoculation with C. musae, and was significantly lower than that of the control after four days of storage. C. musae infection led to a significant increase in the rate of chlorophyll decomposition in banana pericarp and the rate of the green-brown color change in banana fruit. Furthermore, C. musae infection promoted the continuous transformation of polysaccharides (e.g., starch) in fruit into soluble sugars, resulting in a significant increase in soluble solid and reducing sugar content; these changes were more pronounced in the Musa spp. ABB cultivar. C. musae infection accelerated the increase in titratable acid content during storage, enhanced the respiration rate and the rate of infection, and significantly increased the activities of polyphenol oxidase and peroxidase in banana fruit. These results indicate that infection with C. musae can accelerate the maturation, softening, senescence, and decay of banana fruit.

12 Bioactive Compounds of Different Hawthorn Cultivars and Their Antioxidant Activities

ZHANG Xiao-bo , DENG Jie , WEN Ling-rong , YOU Li-jun

2017, 33(9):91-95. DOI: 10.13982/j.mfst.1673-9078.2017.9.013

[Abstract](1158) [HTML](240) [PDF 444.99 K](1158)

Abstract:
The antioxidant properties of two common hawthorn cultivars, Shanlihong and Dajinxing, which are widely grown in the Shandong province of China, were examined. The total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activity of hawthorn powder prepared by freeze-drying were measured. Antioxidant activity was assessed based on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity, oxygen radical absorbance capacity (ORAC), and rapid peroxyl radical scavenging capacity (PSC). Moreover, differences in the identity and quantity of active components with antioxidant activities between the two cultivars were analyzed by high performance liquid chromatography (HPLC). The TPC and TFC of the Shanlihong extract (61.91 mg gallic acid equivalents/g DW and 55.96 mg catechin equivalents/g DW, respectively) were significantly higher than those of the Dajinxing extract. While both of the hawthorn fruit extracts had high antioxidant activity, the Shanlihong extract showed higher antioxidant activity than the Dajinxing extract, with a 1.54-fold higher ORAC and a two-fold higher PSC. Analysis of the hawthorn fruit extracts by HPLC led to the identification of seven polyphenols. Procyanidin B2 and epicatechin were the predominant phenolic compounds in both the Shanlihong and Dajinxing cultivars, and the polyphenol content of the Shanlihong cultivar was significantly higher than that of the Dajinxing cultivar. This comprehensive evaluation shows that the quantity and type of bioactive components in hawthorn differ between different cultivars, and that the Shanlihong cultivar, which has stronger antioxidant activity than the Dajinxing cultivar, is a potential source of natural antioxidants.

13 Hypoglycemic Activity of Phyllanthus emblica L extracts and Analysis of its Main Components

LI Ming-xi , HUANG Wei-feng , YAO Liang-liang , WAN Chun-peng

2017, 33(9):96-101. DOI: 10.13982/j.mfst.1673-9078.2017.9.014

[Abstract](906) [HTML](409) [PDF 657.83 K](1083)

Abstract:
The effects of Phyllanthus emblica L extract on mRNA expressions of GLUT-2 (glucose transporter type 2) and PPARγ (peroxisome proliferator-activated receptor-γ) and the activities of PPRE (peroxisome proliferator response element) and NF-κB in LO2 cells were studied to elucidate the hypoglycemic mechanism and the main active components of this extract. The methanol extracts of P. emblica L were first isolated using a D101 macroporous resin column to yield three fractions. Real-time polymerase chain reaction (PCR) and luciferase reporter gene methods were applied to study the effects of the extracts of P. emblica L and their active components on the mRNA expressions of GLUT-2 and PPARγ and the activities of PPRE and NF-κB. The extracts of P. emblica L significantly enhanced the mRNA expression of GLUT-2 and PPARγ and activity of the PPRE reporter gene (p<0.05), inhibited the lipopolysaccharide (LPS)-induced inflammation (p<0.05), and reduced the activity of the NF-κB reporter gene; the inhibitory effect was dose-dependent (p<0.05). The 30% ethanol-eluted fraction from the macroporous resin column was the active fraction. Sephadex LH-20, C18 (ODS), semi-preparative high performance liquid chromatography (HPLC) columns were used, and one main component was isolated and identified as gallic acid. P. emblica L might exert its hypoglycemic effect by increasing the expressions of GLUT-2 and PPARγ and inhibiting the inflammation-related pathway. Gallic acid may be the major active component.

14 Construction of Attenuated Listeria monocytogenes Strain EGDe-sigB and Preliminary Identification of Biological Activity of sigB

CHEN Guo-wei , LIU Wu-kang , DING Cheng-chao , XIE Man-man , GUO Liang , DONG Qing-li , LIU Qing

2017, 33(9):102-108. DOI: 10.13982/j.mfst.1673-9078.2017.9.015

[Abstract](1261) [HTML](272) [PDF 721.40 K](1286)

Abstract:
Listeria monocytogenes is a foodborne pathogen infectious to both humans and animals. L. monocytogenes can cross the human intestinal barrier, placental barrier, and blood-brain barrier, thereby causing gastroenteritis, meningitis, miscarriage, and other diseases. Sigma B factor, encoded by the gene sigB, is an important regulatory factor for the environmental stress response in many Gram-positive bacteria, and directly and indirectly controls the expression of important virulence genes, such as prfA and inlA. The sigB gene of L. monocytogenes strain EGDe was knocked out by homologous recombination, and the resulting deletion strain (EGDe-ΔsigB) was used to study the effect of sigB deletion on growth, expression of 13 virulence genes (including inlA, inlB, and prfA), and invasion of Caco-2 intestinal epithelial cells. The results showed that the growth rate of the EGDe-ΔsigB strain was equivalent to that of the wild-type EGDe strain. Deletion of sigB caused a significant reduction in the expression levels of inlA and inlB, but a significant (four- to five-fold) increase in the expression levels of the virulence genes actA and plcA, demonstrating that sigB has a relatively large influence on the expression of some virulence genes in L. monocytogenes. Furthermore, invasion assays indicated that deletion of sigB caused a decline in the ability of L. monocytogenes strain EDGe to invade Caco-2 cells.

15 Isolation and Identification of Compounds with Antioxidant Activity from Gynostemma pentaphyllum Makino

SHI Man-man , JIANG Jian-guo

2017, 33(9):109-114. DOI: 10.13982/j.mfst.1673-9078.2017.9.016

[Abstract](953) [HTML](263) [PDF 532.95 K](926)

Abstract:
Compounds with radical-scavenging and antioxidant activities were isolated from Gynostemma pentaphyllum Makino, and their antioxidant properties were studied. The compounds were purified using various column chromatography techniques, the structures of the compounds were determined mainly by proton and carbon-13 nuclear magnetic resonance (1H-NMR and 13C-NMR) spectroscopy, and the fingerprints of the compounds were analyzed by high performance liquid chromatography (HPLC). The radical-scavenging and antioxidant activities of the compounds were evaluated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and ferric reducing antioxidant power (FRAP) assays. Two compounds with strong antioxidant activity were obtained from the n-butanol and ethyl acetate fractions of G. pentaphyllum and identified as kaempferol 3-O-[2G-(E)-coumaroyl-3G-O-β-D-glucosyl-(3R)-O-β-D- glucosylrutinoside] (compound 1) and 3,4-dihydroxyphenyl-O-β-D-glucopyranoside (compound 2). The presence of compounds 1 and 2 in the n-butanol and ethyl acetate fractions, respectively, was verified by HPLC fingerprinting. DPPH assays revealed that both compound 1 and compound 2 have strong radical-scavenging activity against DPPH. In the concentration range of 400~800 μg/mL, the antioxidant activity of compound 1 was stronger than that of vitamin C (Vc). ABTS assays showed that in the concentration range of 12.5~100 μg/mL, the radical-scavenging activities of compound 1 and compound 2 were stronger than that of Vc. Finally, FRAP assays indicated that the antioxidant activities of compounds 1 and 2 at low concentrations were weaker than that of Vc, but the activities of these compounds at a concentration of 800 μg/mL were comparable to that of Vc.

16 Effects of Temperature and Microfluidization Treatments on the Particle Properties of Whey Protein Isolate(WPI)

CHEN Ye-bao

2017, 33(9):115-121. DOI: 10.13982/j.mfst.1673-9078.2017.9.017

[Abstract](905) [HTML](289) [PDF 640.59 K](879)

Abstract:
The aim of this paper was to study the effect of microfluidization treatment on the particle properties of whey protein isolate (WPI) at different temperatures. With the microfluidization treatment and temperature as variables, the WPI was analyzed here by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and differential scanning calorimetry, and the average particle size, zeta-potential, surface hydrophobicity (Ho) and emulsifying activity index (EAI) of the WPI were characterized and measured. The results showed that both the average particle size and Ho of the WPI treated with microfluidization were smaller than those of the WPI without microfluidization treatment at all temperatures, whereas the zeta-potential of the WPI treated with microfluidization was higher than that of the control WPI . Regardless of whether the WPI was treated with microfluidization, Ho of the WPI was basically unaffected by the temperature when it was below 60 ℃, increased with the increasing temperature when it was above 60 ℃, and reached a maximum at 80 ℃. For example, the Ho values of WPI treated without or with microfluidization at 80℃ were 3786 and 3082, respectively. Besides, the EAI of the WPI was basically unaffected by the temperatures when the temperature was below 60℃, increased with increasing temperature when the temperature was above 60 ℃, and reached a maximum at 80 ℃. For example, EAI values of the WPI treated without or with microfluidization at 80 ℃ were 130.5 and 120 m2/g, respectively. The changes in the average particle size and EAI without and with microfluidization treatment may be associated with the synergistic effect of the zeta-potential and Ho of the WPI.

17 Screening and Identification of Aroma-producing Microorganisms in Pottery-flavor Daqu

CHEN Meng-en , FAN Jian-hui , HOU Jian-guang , HAN Su-na , NIU Jiao , YANG Fang-yu

2017, 33(9):122-127. DOI: 10.13982/j.mfst.1673-9078.2017.7.018

[Abstract](825) [HTML](189) [PDF 505.39 K](977)

Abstract:
Aroma-producing microorganisms were screened from the microbial resources of pottery-flavored daqu. The relationship between aroma-producing microorganisms and flavoring substances in Luzhou-flavored daqu was also investigated. Functional aroma-producing microorganisms were identified using various molecular biology techniques. Multiple strains of bacteria (37) and yeast (22) were isolated and purified from the various fermentation stages of pottery-flavored daqu by traditional microbial separation. Each strain was separately cultured in wheat solid growth medium. The sensory evaluation (smell test) showed that the individual strain YSY04 could produce strong flavors after fermentation. The volatile components present in the fermentation products of the strains were identified by headspace solid-phase micro extraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). This analysis identified a number of flavor substances in the fermentation products of the strain. Among them, pyrazine, phenylethanol, guaiacol, 2,3-butanediol, and terpenes were identified as important flavor substances present in pottery-flavored daqu. Therefore, the strain was primarily identified as the functional aroma-producing microorganism present in pottery-flavored daqu. Morphological observation and molecular biology identification analysis confirmed that the YSY04 strain belonged to the species Wickerhamomyces anomalus.

18 A Comparative Study of Three Types of Vegetables During the Vacuum Precooling Process

WU Xin-wei , ZHU Zhi-wei , SUN Da-wen

2017, 33(9):128-133. DOI: 10.13982/j.mfst.1673-9078.2017.9.019

[Abstract](644) [HTML](177) [PDF 745.78 K](1073)

Abstract:
Cabbage (Brassica oleracea L. var. capitata L), Chinese cabbage (B. rapa pekinensis), and flowering cabbage (B. campestris L. ssp.chinensis var.utilis Tsen et Lee) were treated with vacuum precooling under different precooling final pressures and processing loads. The effects of leaf wrapping shape, compactness, non-vein leaf ratio, and leaf thickness on the precooling time, weight loss rate, and temperature difference were investigated. The results showed that three types of leafy vegetables (2400 g) were quickly cooled by vacuum precooling to 4℃ in less than 25 min with a precooling final pressure of 500 Pa. Significant differences (p < 0.05) in cooling time, weight loss, and temperature differences among cabbage, Chinese cabbage, and flowering cabbage were observed during the vacuum cooling process at various pressures and processing loads. The wrapping shape and compactness of cabbages affected the precooling time and temperature, and the other tissue characteristics of leaves, including the non-vein ratio and thickness, had major effects on weight loss during vacuum precooling. The morphological structure of the leaf was an important factor affecting the vacuum precooling process, and the final pressure and processing load during vacuum cooling could be determined based on the morphological characteristics of the specific vegetable.

19 Analysis of the Forecasting Model and Optimization route to Extract Syringin From Branches of Syringa reticulata

JIANG Zhi-hui , LI Gui-rong , ZHENG You-lan

2017, 33(9):134-139. DOI: 10.13982/j.mfst.1673-9078.2017.9.020

[Abstract](798) [HTML](334) [PDF 611.46 K](862)

Abstract:
The ultrasonic process to extract syringin from the branches of Syringa reticulata was optimized using a central composite design and response surface methodology. With the ethanol volume fraction, ultrasonic extraction time, and solvent ratio as the independent variables and the extraction rate of syringin as the dependent variable, multiple linear regression analysis and binomial fitting were performed with the independent variables. Ridge analysis and response surface methodology were used to optimize the extraction process, and predictive analysis was performed. The analysis indicated that the optimum conditions to extract syringin were as follows: 17.03-fold amount of 54.64% ethanol, and ultrasonic extraction for three times. Each extraction was carried out for 85.23 min with an ultrasonic power of 80 W at 30 ℃. The deviation between the observed verification results obtained under optimal conditions and the values predicted by the model was 1.26%, and the correlation coefficient of the binomial fitting complex model was 0.9047. The results showed that the quadratic polynomial model could accurately describe the relationships between the extraction rate of syringin and the influencing factors and had a high reliability. Moreover, these findings demonstrated that the extraction process optimized by central composite design and response surface methodology was simple and stable for extracting syringin from the branches of S. reticulata, with high precision. Thus, this method can be used for actual production.

20 Preparation of Chitooligosaccharides with the Degree of Polymerization below Six by Oxidative Degradation of Chitosan

WU Li-hua , ZHOU Meng , ZHENG Bi-sheng , YE Sheng-quan

2017, 33(9):140-146. DOI: 10.13982/j.mfst.1673-9078.2017.9.021

[Abstract](974) [HTML](315) [PDF 635.24 K](1185)

Abstract:
Chitooligosaccharides can be obtained by chitosan (COS) degradation. Chitooligosaccharides have a low molecular weight, good water solubility, and high biological activity, and can be easily absorbed. In this work, Chitosan with a deacetylation degree of over 95% underwent oxidative degradation by hydrogen peroxide to prepare chitooligosaccharides with a degree of polymerization below six, which was qualitatively and quantitatively analyzed by ion chromatography and pulsed amperometric detection. The effect and degradation characteristics of hydrogen peroxide concentration, reaction time, and reaction temperature on chitosan degradation were investigated using gel permeation chromatography and using the product of the total peak area of chitooligosaccharides in the ion chromatogram of the degradation products and the yield of products as the response index. In addition, the oxidation conditions were optimized by a response surface analysis method. The results showed that in terms of methodology, it was feasible to use ion chromatography to determine chitooligosaccharides, and the method had good precision, stability, and reproducibility. The optimum degradation conditions were as follows: hydrogen peroxide concentration 4.50%, reaction time 6 h, and reaction temperature 56 ℃. From the chromatographic analysis of the degradation products under optimal conditions, the chitooligosaccharides with a lower degree of polymerization were easier to obtain, and the degradation process of chitosan could be controlled by ion chromatography.

21 Antioxidative Peptides and Angiotensin I-converting Enzyme Inhibitory Peptides Obtained from Soybean by Protease Treatment at Pilot Scale

LIU Wen-ying , CHEN Liang , GU Rui-zeng , LU Jun , PAN Xing-chang , CAI Mu-yi

2017, 33(9):147-158. DOI: 10.13982/j.mfst.1673-9078.2017.9.022

[Abstract](662) [HTML](252) [PDF 421.90 K](1148)

Abstract:
A pilot-scale production of soybean oligopeptides (SOPs) was developed in this study, and the SOPs had a high protein content (91.45%) and low molecular weight (84.37% of the product were less than 1000 u). The in vitro antioxidant activity and angiotensin I-converting enzyme (ACE) inhibitory activity of SOPs were analyzed. SOPs were then separated by reversed-phase high performance liquid chromatography, and six major fractions (numbered from 1?6) were collected and subjected to mass spectrometry to identify the active peptides. The sequences of 41 peptide fragments were identified, and 15 peptide fragments were selected to evaluate the antioxidative and ACE inhibitory activities using the aforementioned methods. The results showed that SOPs contained two novel potent antioxidative peptide fragments (Tyr-Glu, 8.61 ± 0.42 mmol Trolox equivalents/g sample; Asp-Tyr-Arg, 6.53 ± 0.34 mmol Trolox equivalents/g sample) and four potent ACE inhibitory peptide fragments (Leu-Val-Arg, IC50 = 51.75 μM; Leu-Tyr, IC50 = 305.76 μM; Asp-Tyr-Arg, IC50 = 1082.95 μM; Asp-Phe, IC50 = 1106.04 μM). Most of them were novel antioxidant or ACE inhibitory peptides derived from soybeans. This study suggested that SOPs and their active peptides might be used as antioxidative or hypotensive substances in food additives, dietary nutrients, and pharmaceutical agents.

22 Fabrication and Characterization of Gelatin-Lysozyme/ Nano-Zno Nanocomposite Films

HU Er-kun , SHI Wei-jian , YIN Shou-wei

2017, 33(9):159-165. DOI: 10.13982/j.mfst.1673-9078.2017.9.023

[Abstract](932) [HTML](282) [PDF 603.87 K](986)

Abstract:
This work attempted to achieve effective antibacterial gelatin films by incorporating organic / inorganic antibacterials leading to synergistic antibacterial effect and wide antibacterial spectrum. Surface morphology, mechanical and barrier properties as well as antimicrobial activity of the films were evaluated. Gelatin-lysozyme/ nano-ZnO nanocomposite films had selective light absorbance. Obvious absorption peak occurred in the ultraviolet (UV) region, while the transmittance was over 90% in the visible region. The simultaneous incorporation of lysozyme / nano-ZnO resulted in synergistic antibacterial activity against test organism, i.e., Escherichia coli (G–) and Bacillus subtilis (G+). The loading of lysozyme or nano ZnO within the gelatin matrix did not affect the surface morphology of the films, while the simultaneous loading of lysozyme and nano-ZnO resulted in heterogeneous surface morphology, probably due to the formation of the agglomerates via the interaction between lysozyme and nano-ZnO in the filim-forming solution or the casting process. As a result, gelatin network structure as well as the performance of water vapor and oxygen barrier was varied, in an antimicrobial type-and dose- dependent manner. This study provides a theoretical basis for the development of novel organic/ inorganic composite films.

23 Preparation and Identification of Monoclonal Antibody against Isoprocarb

XIONG Bo , LIANG Zu-pei , LIU Gui-zhou , LIU Hui , TANG Qiu-shi , YUAN Li-peng

2017, 33(9):166-170. DOI: 10.13982/j.mfst.1673-9078.2017.9.024

[Abstract](960) [HTML](189) [PDF 437.88 K](792)

Abstract:
Isoprocarb is a common pesticide widely used in fruit, vegetable, and tobaccoin China. However, this pesticide also has strong biological toxicity. The aim of this study was to prepare a monoclonal antibody against isoprocarb, to facilitate rapid detection of this pesticide. In this study, 2-isopropylphenol and other compounds were used as raw materials to synthesize the hapten and artificial antigen of isoprocarb. Then, through immunized mice, cell fusion, cloning and screening, the monoclonal antibody cell was obtained, and monoclonal antibodies were obtained by ascites derivation and caprylic acid-ammonium sulfate precipitation. An indirect competitive enzyme-linked immunosorbent assay (ELISA) method was used to identify antibody specificity. The results showed that the monoclonal antibody detection range was from 1.88~82.8 ng/mL, with a half maximal inhibitory concentration (IC50) value of 11.7 ng/mL and an isoprocarb detection limit of 0.54 ng/mL. The antibody had high specificity, and no obvious cross-reactions with the isoprocarb structural analogs carbofuran, carbaryl, aldicarb, methomyl, or 2-isopropyl phenol. This antibody could be used to develop an ELISA assay for rapid isoprocarb detection. The preparation of this monoclonal antibody lays a solid foundation for the development of products to rapidly detect isoprocarb.

24 Preparation of Polyclonal Antibodies for Patulin

LIU Bing , ZHANG Fu-yuan , GAO Jin , SHENG Wei , WANG Shuo

2017, 33(9):171-175. DOI: 10.13982/j.mfst.1673-9078.2017.7.025

[Abstract](889) [HTML](362) [PDF 477.22 K](1011)

Abstract:
Patulin is a neurotoxin with a strong toxic effect. This toxin is expensive and unstable; the chemical structure of patulin is simple, and the direct preparation of immunogens from patulin has a poor immune effect. As a result, few immunoassay methods for patulin have been reported. Design and preparation of the immunogen is one of the key steps for developing the immunoassay. Here, the structural characteristics of patulin were studied via computer-aided simulation design and methods for virtual screening of drug molecules. A suitable substitute with low toxicity and cost was optimized and screened, and the hapten of patulin was designed and successfully prepared. Two immunogens of patulin were obtained by conjugation with two carrier proteins (BSA and KLH) by the active ester method. The polyclonal antibodies were prepared after the immunization of rabbits, and the antiserum titers reached 1:16000 and 1:64000, respectively. This study lays a foundation for the further establishment of an immunoassay for patulin and also provides new ideas and methods for designing immunogens for toxic small-molecule compounds.

25 Extraction of Anthocyanins from Sugarcane Rind and Co-pigmentation Effect of Co-pigments on Anthocyanins

YAN Huai-feng , ZHAO Zhen-gang

2017, 33(9):176-182. DOI: 10.13982/j.mfst.1673-9078.2017.9.026

[Abstract](698) [HTML](181) [PDF 636.78 K](856)

Abstract:
Anthocyanins were extracted from sugarcane rind with mixed organic reagents as extraction solvents. The optimum extraction conditions were determined by single-factor and orthogonal experiments. The co-pigmentations of anthocyanin extracts were conducted with three co-pigments (ferulic acid, vanillic acid, and p-coumaric acid), and the effect of reaction temperature and pH on the co-pigmentation using co-pigments was determined. The optimum extraction conditions were as follows: extraction solvent composition: Vmethanol:Vacetone:V water = 2:2:1 (pH = 1.0); material to liquid ratio: 1:10 (g/mL); extraction time: 120 min; extraction temperature: 20°C. Under this condition, the total anthocyanin content reached 125.01 ± 1.77 mg/100 g dry rind (dry weight). In the wine model system, an increase in the co-pigmentation effect was observed with increasing mass concentration of co-pigments. A decrease in pH value could promote the co-pigmentation effect of co-pigments on anthocyanins, and co-pigmentation reached an equilibrium when the optimal pH value for co-pigmentation was reached. After the optimal temperature for co-pigmentation was reached, a decrease in co-pigmentation was observed with increasing temperature. The co-pigmentation effects of three co-pigments were in a descending order: p-coumaric acid > ferulic acid > vanillic acid.

26 3D Printing Processing of Potato Starch and the Changes in Its Structure and Properties

FENG Chuan-xing , ZHOU Quan-cheng

2017, 33(9):183-188. DOI: 10.13982/j.mfst.1673-9078.2017.9.027

[Abstract](1052) [HTML](220) [PDF 680.47 K](990)

Abstract:
The aim of this work was to develop a three-dimensional (3D) printing procedure for potato starch and to investigate the changes in physical and chemical structure and properties of potato starch during the 3D printing process. In this paper, a new type of 3D printing principle for potato starch is proposed based on starch gelatinization. The particle structure, crystal structure, molecular structure, thermal properties, and textural properties of 3D-printed starch were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC), and texture analysis. The results showed that the physical and chemical structure and properties of the gelatinized potato starch changed remarkably, and adhesion and gelation occurred among the potato starch molecules. 3D printing significantly reduced the adhesiveness, hardness, and gelling property of gelatinized potato starch but had no significant effects on the thermal properties, crystalline structure, and chemical bonds, and changed only the surface smoothness in the particle structure. These results indicated that 3D printing changed only some of the physical properties of gelatinized potato starch and had no effect on the physical and chemical structure. This study provides a theoretical basis and technical support data for application of the 3D printing technology to food production and should be useful for theoretical research and practical applications.

27 Analysis of Moisture Changes in Flos lonicerae at Different Flowering Stages during Infrared Drying Using Low-field NMR

DU Li-ping , CUI li , ZHAO Heng-qiang , YAN Hui-jiao , WANG Tao , WANG Xiao

2017, 33(9):189-194. DOI: 10.13982/j.mfst.1673-9078.2017.9.028

[Abstract](790) [HTML](195) [PDF 492.98 K](826)

Abstract:
Changes in water distribution and water states in Flos lonicerae during infrared drying were assessed at three different flowering stages (three green period, large white period, and golden flowering period). The three F. lonicerae samples were subjected to far-infrared radiation at 45 ℃, and low field-nuclear magnetic resonance (LF-NMR) spectroscopy was employed to evaluate differences in water mobility and distribution. Three water states – bound water, immobilized water, and free water – were detected in F. lonicerae samples at different flowering stages, with volume fraction decreasing in the order: immobilized water > bound water > free water. The proportions of free water and bound water in the F. lonicerae sample at the three green stage were higher than those in the F. lonicerae samples at the big white and whole flowering stages, and the immobilized water content of the F. lonicerae sample at the three green stage was lower than those of the samples at the big white and whole flowering stages. During the drying process, different forms of water also exhibited different patterns of change; the immobilized water content decreased gradually, while the bound water content decreased at first and then increased. The drying process changed the internal water distribution and water content of the F. lonicerae samples, and interconversion between different forms of water occurred. The fluidity of the bound water increased during the initial period of drying, before decreasing during the final stages of the drying process. However, the fluidity of the bound water of the sample at the large white stage continued to decrease throughout the drying process. During the drying process, the water content of F. lonicerae was highly correlated with the peak area of immobilized water and the total peak area (R2 > 0.9). Thus, the NMR technique used in this study provided an intuitive basis for the analysis of water distribution and variation in F. lonicerae at different flowering stages.

28 Effects of Fat and Protein Content on Cream-Whey Fermentation Liquid

LIN Wei-feng , ZHOU Yan , BAO Zhi-ning , XIA Feng-geng

2017, 33(9):195-201. DOI: 10.13982/j.mfst.1673-9078.2017.9.029

[Abstract](1184) [HTML](163) [PDF 493.04 K](1958)

Abstract:
The effects of different fat content (7%, 14%, and 21%) and protein content (2.3% and 4.6%) on cream-whey fermentation liquid and the relationship between the composition of new flavor fermentation systems and fermentation characteristics were studied. Changes in the number of viable bacterial cells, titratable acidity, and pH value during the fermentation process were measured. The volatile flavor components were extracted using headspace solid-phase microextraction (HS-SPME), analyzed by gas chromatography-mass spectrometry (GC-MS) after fermentation for 60 h, and evaluated by sensory tests. The results showed that the increase in fat content had no influence on the proliferation of lactic acid bacteria or on the pH value at low protein levels, but suppressed the proliferation of lactic acid bacteria and prevented the decline in pH at high protein levels. In addition, increased fat content promoted the production of flavor and volatile compounds and inhibited the production of acids by the bacteria. Increased protein content promoted the proliferation of lactic acid bacteria, significantly increased the content of volatile flavor components, and slowed the decline in pH values. Moreover, increased protein content promoted the production of acids at low fat levels, but inhibited the production of acids at high fat levels. After 60 h of fermentation, the main volatile compounds in the system were acetic acid, butyric acid, 2,3-butanedione, and 3-hydroxy-2-butanone. The sensory evaluation showed that the mixed fermentation liquid with 14.0 % fat and 4.6 % protein had the best structural state and the strongest yoghurt flavor.

29 Effect of Superfine Whole Sorghum Flour on the Rheological Properties of Dough and the Quality of Steamed Bread

WANG Jun , CHENG Jing-jing , WANG Zhou-li , YUAN Ya-hong , GUO Kang-quan , YUE Tian-li

2017, 33(9):202-209. DOI: 10.13982/j.mfst.1673-9078.2017.9.030

[Abstract](983) [HTML](295) [PDF 477.76 K](1275)

Abstract:
The rheological properties of dough and the quality of steamed bread prepared using blends of superfine whole sorghum flour and wheat flour were investigated. Superfine whole sorghum flour, prepared by grinding whole sorghum to a superfine powder, was added to wheat flour in different proportions. When the whole sorghum flour content in the flour blend was 5~10%, the values of all viscosity-related parameters and the time to reach peak viscosity increased relative to the control; when the whole sorghum flour content reached 15~20%, the values of these parameters decreased, and no significant change in pasting temperature was observed. The water absorption capacity of the flour blends increased with increasing whole sorghum flour content. When the whole sorghum flour content reached 10%, the development time, stability time, farinograph quality number, area of extensograph curve, resistance to extension, and extensibility all decreased significantly compared with the control. Increases in whole sorghum flour content resulted in significant decreases in all sensory-related indexes (except for color). Texture analysis showed that the hardness and chewiness of steamed bread increased, the adhesiveness and cohesiveness increased at first and then decreased, the springiness decreased, and the resilience did not change significantly with increasing whole sorghum flour content. No significant changes in cell elongation or other indexes measured by image analysis were observed with increasing whole sorghum flour content. The addition of superfine whole sorghum flour changed the main components of the flour blends, particularly the composition and content of starch and protein, and had a significant effect on the rheological properties of dough and the quality of steamed bread.

30 Study on the Brewing Process of Top-Fermented Sorghum Beer

ZHU Feng-jiao , CHEN Ye-fu , WANG Xi-bin , SONG Lu-lu , GUO Xue-wu , XIAO Dong-guang

2017, 33(9):210-216. DOI: 10.13982/j.mfst.1673-9078.2017.9.031

[Abstract](1129) [HTML](321) [PDF 590.65 K](970)

Abstract:
Sorghum beer is a nutrient-rich and gluten-free alcoholic drink with unique taste, and has broad prospects for development. To develop good-quality sorghum beer, sorghum malt was used as a raw material to study the effects of the mashing process on the content of total reducing sugars and α-amino nitrogen in sorghum wort, the effects of fermentation conditions on the production of higher alcohols, and the effects of different clarifiers on the clarity and color of sorghum beer after fermentation. The results showed that the optimal mashing method was decantation, and the detailed process condition was as follows: lixiviation at 35?C for 20 min, pasting at 90?C for 30 min, and saccharification at 65?C for one hour. The content of total reducing sugar in sorghum wort produced by the above techniques was 83.23 g/L, while the content of α-amino nitrogen was moderate and the final content was 180.8 mg/L. The optimum fermentation conditions were determined as follows: sorghum wort concentration: 12 °P, the quantity of inoculated yeast: 2.0 × 107 cells/mL, fermentation temperature: 16?C. The content of higher alcohols was 109.09 mg/L in sorghum beer, and these fermentation conditions could effectively reduce the content of higher alcohols. In addition, the best clarifier was bentonite, and when the proportion of added clarifier was 0.9%, the light transmittance was 90% and the best clarification effect of sorghum beer was achieved. Under this brewing condition, the top-fermented sorghum beer obtained was clear, had a bright color, unique taste, and moderate content of higher alcohols, and was a new type of alcoholic beverage with a unique flavor.

31 Study on the Ethanol Precipitation Process for Sugar Beet Pectin

ZHANG Tao , GUO Xiao-ming , ZHANG Bing-bing , YU Shu-juan

2017, 33(9):217-223. DOI: 10.13982/j.mfst.1673-9078.2017.9.032

[Abstract](928) [HTML](260) [PDF 580.46 K](964)

Abstract:
Ethanol precipitation is widely used for purifying pectin in industrial production. The effects of precipitation pH and ethanol concentration on the ethanol precipitation yield and the physicochemical characteristics of sugar beet pectin (SBP) were studied. Zeta potential was used to characterize the interaction between SBP molecules during the precipitation process. The structure of SBP was analyzed by a series of techniques such as high-performance size exclusion chromatography (HPSEC), high-performance anion exchange chromatography (HPAEC), and high-performance liquid chromatography (HPLC). The results indicated that the highest precipitation rates of unpurified and purified SBPs were reached when the pH was 2.5 and the ethanol concentration in the system was 71.25%, with precipitation rates of 96.81% and 57.23%, respectively. The weight-average molar mass (Mw) of SBP ranged from 145.07 kg/mol to 404.27 kg/mol. Five neutral sugars, including rhamnose, arabinose, galactose, glucose, and xylose, were detected in SBP, and their content ranged from 16.23~17.83%. The I-pH and system ethanol concentration of SBP solution had impacts on SBP hydration to some extent, and the structures of precipitated SBP were affected by the ethanol precipitation conditions.

32 Patterns of the Physiological and Biochemical Changes during the Persimmon Drying Process

SHI Bao-zhu , DUAN Xu-chang , WU Ye-ting , LIANG Lian-you , JIAO Zhong-gao , FENG Suo-lao

2017, 33(9):224-230. DOI: 10.13982/j.mfst.1673-9078.2017.9.033

[Abstract](884) [HTML](253) [PDF 664.30 K](983)

Abstract:
The aim of this study was to explore the pattern of the physiological and biochemical changes in persimmons during the drying process and provide a theoretical basis for the best method to dry and produce persimmons in a factory. The patterns of changes in moisture, tannins, original pectin, soluble pectin, ethanol, and aldehyde content, and the alcohol dehydrogenase and the pectinase activities of persimmon during artificial and natural drying processes were investigated and compared. The changes in the sulfur dioxide content during the natural drying process was determined, and the total number of bacteria in dried persimmon samples prepared by artificial and natural drying processes were compared. The results showed that the moisture, tannins, original pectin, soluble pectin, ethanol, and aldehyde content, and the alcohol dehydrogenase and the pectinase activities of the dried persimmon samples prepared by artificial and natural drying processes were consistent, but the artificial drying process required about one-seventh of the time required for natural drying. Dried persimmons prepared from artificial drying were not affected by the climate and did not contain sulfur dioxide residue, and the total number of bacteria was only 23 CFU/g. Nevertheless, for natural drying process, the persimmon needed to be fumigated six times with SO2 to prevent mildew, the dried persimmon prepared from natural drying contained 150 mg/kg sulfur dioxide residue, and the total number of bacteria was 3500 CFU/g, which was 152 times of that in the dried persimmon prepared by artificial drying. The above findings showed that the artificial drying process could completely replace natural drying for producing dried persimmons.

33 Study on Changes in the Biochemical Properties of Maotai-flavor Daqu during Storage

ZHANG Li , LU Hong-mei , CHEN Li , QIAO Yan , HE Xing , AN Jia-jing

2017, 33(9):231-237. DOI: 10.13982/j.mfst.1673-9078.2017.9.034

[Abstract](760) [HTML](286) [PDF 488.69 K](1036)

Abstract:
Maotai-flavor daqu was used as a research object, and changes in its biochemical properties, such as fermenting power, liquefaction power, saccharification power, esterification power, alcohol-producing power, water content, the total number of microbial colonies, and mold and yeast counts during the storage of daqu were studied. The results revealed that the mold counts, liquefaction power, saccharification power, and esterification power were relatively low at the early stage of the storage of Maotai-flavor daqu; these four parameters showed a downward trend after the initial increase during the first four months of storage, and then the parameters maintained between five and eight months of storage. Water content, the total number of colonies and yeast cells, fermenting power, and alcohol-producing power of Maotai-flavor daqu significantly decreased during the first four months of storage, and then these parameters fluctuated in a relatively small range. The correlation analyses (of water content, the total number of microbial colonies, counts of molds and yeasts, fermenting power, liquefaction power, saccharification power, esterification power, alcohol-producing power, and other parameters) were conducted, and more than 60% of these parameters showed a significant or extremely significant correlation. The biochemical properties of Maotai-flavor daqu began to stabilize between five and six months of storage, and this situation was conducive to stabilization of the yield and quality of Maotai-flavor base liquor and was most suitable for the production of Maotai-flavor liquor.

34 Determination of Mercury (II) Content in Seafood by Cycle DNA Amplification Based on Hybridization Chain Reaction

DU Ping

2017, 33(9):238-242. DOI: 10.13982/j.mfst.1673-9078.2017.9.035

[Abstract](1078) [HTML](230) [PDF 478.06 K](865)

Abstract:
A highly sensitive biosensor based on surface enhanced Raman scattering (SERS) for detecting trace amounts of mercury (II) in seafood was designed by cycle amplification based on hybridization chain reaction of DNA hairpins and the stable structure formed between the nucleotide base thymine (T) and mercury (II). Firstly, the nano-Au bio-barcode with numerous Raman signal DNA molecules was prepared as the Raman signal probe, and then the captured DNA was immobilized on magnetic beads by amide bonds. The nano-Au particles containing numerous Raman signal DNA molecules were combined specifically on the magnetic beads by the stable structure formed by T-mercury (II)-T and the cycle amplification based on hybridization chain reaction. Finally, the detection of mercury (II) in the solution was achieved by the SERS technique. The optimum experimental conditions were also investigated. When the concentration of DNA captured by magnetic beads was 1.0×10-7 mol/L and the hybridization reaction proceeded for three hours at 37 ℃ in pH 7.4 Tris-HCl buffer solution, the mercury (II) concentration and the Raman signal intensity had good linear relationship, with a linear range of 1.0×10-7~1.0×10-13 mol/L and a detection limit of 1.0×10-13 mol/L (S/N=3). The biosensor was applied to determine the mercury (II) content in the seafood samples, and the measured results were consistent with those obtained by inductively coupled plasma atomic emission spectroscopy (ICP-AES).

35 Analysis of Nutritional and Functional Components, Heavy Metals, and Pesticide Residues of Wolfberry (Lycium barbarum L.) Fruits From Minqin, China

Ebeydulla Rahman , LI Ye , YE Li-yue , QIU Jin-qiang , XU Xing-wen , JI Bao-ping , ZHOU Feng

2017, 33(9):243-249. DOI: 10.13982/j.mfst.1673-9078.2017.9.036

[Abstract](895) [HTML](216) [PDF 274.50 K](881)

Abstract:
To evaluate the nutrient content, bioactive constituents, and safety of wolfberries (Lycium barbarum L.) from Minqin county, China, high-performance liquid chromatography, gas chromatography, and other relevant approaches were employed to measure nutritional and functional components, heavy metals and pesticide residues, and the amino acid composition of wolfberries. The results indicated that for the basic nutritional composition of Minqin wolfberries (100 g dry weight), the content of proteins, crude fats, and carbohydrates were 13.71, 3.09, and 60.08 g, respectively; for analysis of functional components, the content of polysaccharides, carotenoids, betaine, ascorbic acid, total phenolics, and flavonoids were 2.11 g, 569.81 mg, 1.57 g, 45.08 mg, 81.95 mg, and 70.23 mg, respectively. The main basic nutritional composition of Minqin wolfberries included proteins and carbohydrates. Moreover, the wolfberry samples analyzed in this study contained abundant functional amino acids, such as aspartic acid, proline, and glutamic acid. High content of tryptophan, aromatic amino acids, and other essential amino acids were found in Minqin wolfberries. Aspartic acid was the most abundant, and lysine was the first limiting essential amino acid in wolfberries. Minqin wolfberries contained relatively high levels of fats, carotenoids, and ascorbic acid compared with wolfberries from other regions, and the levels of heavy metals and pesticide residues did not exceed the limits for wolfberries as a green food. The findings of this study provide a reference for the quality evaluation of wolfberries grown in Minqin county.

36 Effect of Ultrasonic Treatment on the Volatile Components of Gan-pu Tea

ZHENG Min , LIN Li-jing , HUANG Xiao-bing , LI Ji-hua , PENG Zheng

2017, 33(9):250-256. DOI: 10.13982/j.mfst.1673-9078.2017.9.037

[Abstract](820) [HTML](145) [PDF 597.64 K](1051)

Abstract:
Automatic headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) was used to determine and analyze the volatile components of Gan-pu tea before and after ultrasonic treatment. The results showed that the volatile components of Gan-pu tea came from the peel of Citrus reticulata ‘Chachi’ and ripe Pu'erh tea, and the main volatile constituents were limonene, pinene, beta-myrcene, gamma-terpinene, linalool, terpineol, methyl N-methylanthranilate, 1,2,3-trimethoxybenzene, and others. Ultrasonic treatment could affect the relative volatile component content in different parts of Gan-pu tea. Compared with those of the samples before ultrasonic treatment, for the peel of Citrus reticulata ‘Chachi’, the relative content of alpha-thujene, alpha-pinene, and other components were reduced, and the content of o-cymene and decanal were increased. After ultrasonic treatment, for the Pu'erh tea, the content of butyl acetate, N,N-dimethylformamide, alpha-phellandrene, linalool, terpineol, 1,2,3-trimethoxy-benzene, and others were increased, and the content of beta-myrcene, D-limonene, gamma-terpinene, and 4-ketoisophorone were decreased. The magnitude of variation of each component content was increased with increasing ultrasonication time during the experiment.

37 Quantification and Visualization of Total Volatile Basic Nitrogen Content of Cooked Beef by Hyperspectral Imaging Technique

YANG Dong , LU An-xiang , WANG Ji-hua

2017, 33(9):257-264. DOI: 10.13982/j.mfst.1673-9078.2017.9.038

[Abstract](882) [HTML](248) [PDF 672.05 K](880)

Abstract:
To quickly and accurately determine the freshness of cooked beef during cold storage, the hyperspectral imaging (HSI) technique was used here to quantify and visualize total volatile basic nitrogen (TVB-N) content of cooked beef. Hyperspectral images of beef samples were captured in the range of 400–1000 nm, and data at six wavelengths (variables) with spectral characteristics were extracted by variable combination population analysis (VCPA). According to feature band images, 18 texture parameters were extracted using the Tamura algorithm, and nine color characteristics in the red (R), green (G), and blue (B) component images were calculated based on the RGB model. Particle swarm optimization and the least squares support vector machine (PSO-LS-SVM) algorithm were used to construct a TVB-N content prediction model from different combinations of variables. After analysis and comparison, the PSO-LS-SVM model based on a combination of spectral and color features showed the best predictive ability, and the determination coefficient (R2p) and root mean square error of prediction (RMSEP) were 0.955 and 1.093, respectively. Finally, the optimal model was applied to visualize TVB-N content. The study revealed that it is feasible to accurately predict and visualize TVB-N content of cooked beef by combining the spectral and color features of HSI and the PSO-LS-SVM algorithm, and this study can serve as a theoretical reference for analysis of freshness of other meats and meat products.

38 Virulence Characteristics and Drug Resistance of Milk-derived Staphylococcus aureus Isolates from the Shihezi Region

TIAN Hui-li , YUAN Jun , LIAO Chao , MENG Yun , MI Wei-yu , JI Hua , WANG Zhou-ping

2017, 33(9):265-270. DOI: 10.13982/j.mfst.1673-9078.2017.9.039

[Abstract](824) [HTML](167) [PDF 535.67 K](780)

Abstract:
The aim of this work was to investigate the contamination, virulence characteristics, and drug resistance of milk-derived Staphylococcus aureus in the Shihezi region. The quantitative detection of S. aureus was carried out on 24 retail milk samples, and the presence of nuc, 16S rRNA, and virulence genes was confirmed by polymerase chain reaction (PCR). The Kirby–Bauer method was used to test the sensitivity of S. aureus to 12 antibiotics. A total of 55 suspected isolates of milk-derived S. aureus were obtained, and 20 isolates were positive in nuc and 16S rRNA gene PCR amplification assays. The virulence gene detection revealed five (5/20; 25%) S. aureus isolates carrying virulence genes, [three isolates carrying Coa (3/5; 60%), one isolate carrying Sei (1/5; 20%), and one isolate carrying Sea + Sec + Coa (1/5; 20%)]. Nineteen out of 20 isolates of S. aureus were found to be resistant to one or more of the tested antibiotics by the disk diffusion method. All the 19 isolates were sensitive to imipenem and chloramphenicol. This paper provides important reference data for rational application of antibiotics in clinical practice and animal breeding and provides the theoretical basis for the risk assessment of harmful S. aureus strains in dairy products.

39 Study on Rapid Quantification of Benzo[a]pyrene in Edible Oil by Surface Enhanced Raman Spectroscopy

WANG Shan , LI Zhong , PAN Liang , LIU Lu , XUE Liang-chen , ZENG Chuan , PENG Bi-ning , XU Xi-lin

2017, 33(9):271-275. DOI: 10.13982/j.mfst.1673-9078.2017.9.040

[Abstract](992) [HTML](277) [PDF 564.96 K](1089)

Abstract:
Benzo[a]pyrene (BaP) is widespread in the industrial sewage from coal tar and oil refining; vegetable oil subjected multiple times to a high temperature as well as charred food may also contain BaP. The permissible limit of BaP in China for edible vegetable oil products is below 10 μg/kg. At present, the most widely used methods for quantification of BaP in food are high performance liquid chromatography, gas chromatography with mass spectrometry, and some others. Nonetheless, in the above methods, sample pretreatment is complicated, measurement time is long, and measurement efficiency is low; therefore, they still cannot meet the requirements for real-time and in situ analysis.Rapid quantification of BaP in edible oil by surface enhanced Raman spectroscopy (SERS) was studied here by means of nanogold-modified porous materials as a SERS substrate. A linear relation between the peak area of SERS and the concentration of BaP was obtained in the range of 0~200 μg/L. The linear equation was y= 134.98x–571.77 (R2=0.9942). At a concentration of 10 μg/kg, the recovery rates of samples ranged from 93.2% to 125.7%, and the relative standard deviations (RSDs) were between 10% and 18%. The detection limit of the SERS method was 5.6 μg/L. The analysis of BaP by the SERS method could be carried out on site using a portable Raman spectrometer, and measurement time was short (generally tens of seconds to one or two minutes). The SERS method provides a new option for rapid quantification of BaP in edible oils if the analytical sensitivity meets the requirements.

40 GC-MS Analysis of Components Extracted from Oat Oil by Two Extraction Methods

ZHANG Chen , LV Zhen-yue , GE Fa-huan , MA Jin-fang , YU Rong-min

2017, 33(9):276-282. DOI: 10.13982/j.mfst.1673-9078.2017.9.041

[Abstract](686) [HTML](162) [PDF 527.72 K](901)

Abstract:
To study the effect of different extraction methods on the chemical composition of oat oil, the components of oat oil were extracted by conventional methods and by using supercritical carbon dioxide, and the composition of the resulting oat oils was determined and analyzed by gas chromatography-mass spectrometry (GC-MS). GC-MS analysis results showed that after the data were analyzed and searched against the National Institute of Standards and Technology (NIST) library, 6 and 13 components were identified in the oat oil extract obtained by traditional extraction and the methyl esterification product of fatty acids in the oat oil extract obtained by traditional extraction, respectively. There were 16 and 10 components identified from the oat oil extract obtained using supercritical carbon dioxide and the methyl esterification product of fatty acids in the oat oil extract obtained using supercritical carbon dioxide, respectively. The peak area normalization method was used to calculate the relative contents of the compounds; the chemical content of four samples accounted for 82.7%, 99.65%, 64.26%, and 99.71% of the total area, respectively. Among them, the compounds with a relatively high content in the oat oil were N-(2-hydroxyethyl)-decanamide, (Z)-6-octadecenoic acid, linoleic acid, oleic acid, hexadecanoic acid, and others. The study aims to provide a reference for further study and development of oat oil for edible or medicinal uses.

41 Research Progress of Detection and Separation Methods for Foodborne Microorganisms at VBNC State

NIE Xin-ying , ZHANG Rui-rui , JIANG Li-fen , LI Qun-ying , XIA Bi-bang , LIAO Hong-mei

2017, 33(9):283-292. DOI: 10.13982/j.mfst.1673-9078.2017.9.042

[Abstract](953) [HTML](288) [PDF 662.98 K](1148)

Abstract:
Under environmental stress, some food-borne microorganisms (Escherichia coli, Salmonella spp., Staphylococcus aureus, lactic acid bacteria, yeast, and others) can stay alive by entering a viable but non-culturable (VBNC) state. Microorganisms entering the VBNC state change in terms of cell morphology, metabolic activity, and pathogenicity, and cannot be detected by conventional methods, thus posing great challenges to food quality and safety. In this study, the development trends of foodborne microorganisms in the VBNC state were summarized and the various environmental induction factors, physiological and biochemical characteristics, and recovery conditions were briefly introduced. The molecular detection technology and phage detection methods that are applied to food-borne microorganisms at VBNC state were mainly discussed, and the advantages and disadvantages of these methods and possible optimization protocol were examined. In addition, the detection and separation methods for microorganisms at VBNC state were summarized and the feasibility of these methods was analyzed. The purpose of this paper was to provide a reference for the further investigations of the physiological characteristics of foodborne microorganisms at VBNC state, and the development of faster, simpler, and more efficient detection methods.

42 Potato as a Staple Food in China: Issues and Solutions

ZENG Fan-kui , LIU Gang

2017, 33(9):293-298. DOI: 10.13982/j.mfst.1673-9078.2017.9.43

[Abstract](1859) [HTML](272) [PDF 307.15 K](1030)

Abstract:
The Ministry of Agriculture of the People’s Republic of China (MOA) has announced that potato will soon be the newest staple food in China. Potato tubers are a rich source of starch, high-quality protein, essential vitamins, minerals, and trace elements, but many problems need to be solved to upgrade potato culturally, technically, environmentally, and economically to a staple food status in China. Overcoming these problems requires the use of domestic and international experiences and technical strategies as references; expanding the potato-growing areas at the expense of the ecological environment is undesirable. Inner Mongolia, northwest China, and southwest China, the major potato production areas, are not suitable for continued expansion of the potato-growing areas because this process causes grassland desertification and soil erosion, and the government has proposed that some farmlands be returned to grasslands or forest. In southern China, cultivation of potatoes in fallow fields in winter is the most promising method for increasing China’s potato production and is worth promoting by the government. In addition, some technical issues need to be solved, such as how to develop potato into a Chinese traditional staple food, how to use dehydrated mashed potatoes as a semifinished food product, how to improve dry matter content of potato tubers, and how to process potato into a semifinished food product at a low temperature.

43 Progress on the Hazards of and Detection Methods for Nε-(1-Carboxymethyl)-L-lysine in Foods

HAN Wen-feng , TAN Xing-he , LIN Xiao-li , QIU Po , MENG Hong-chang

2017, 33(9):299-305. DOI: 10.13982/j.mfst.1673-9078.2017.9.044

[Abstract](1211) [HTML](432) [PDF 1.16 M](1554)

Abstract:
Nε-(1-Carboxymethyl)-L-lysine (CML) in food is one of the main components of advanced glycation end-products, which are produced from the Maillard reaction of the carbonyl group in reducing sugars and the amino group in proteins and/or amino acids. CML has high acid stability and can be used as an important indicator to evaluate protein modifications, carbonyl stress, and lipid oxidation during the Maillard reaction in food systems. After CML enters the human body through food as a medium, it can accumulate in different tissues and organs. When the concentration of CML reaches a certain level, CML will directly affect the function of tissues and organs and lead to pathological changes in the body. CML is closely related to the occurrence of many diseases in the human body and can accelerate the progression of diabetes, nephrosis, and atherosclerosis and the aging of human organs. Quantitative detection of CML can guide the reductions in the intake of CML, which may lower the risk of related diseases. In order to provide a reference for developing highly sensitive, highly selective, fast, and efficient methods for detection of CML content, the hazards of and detection methods for CML were reviewed herein.

Home

About the journal

Notes for submission

Acceptable topics

Author garden

Open access

中文

Volume 33,Issue 9,2017 Table of Contents