Volume 32,Issue 11,2016 Table of Contents

1 Effect of Large Yellow Croaker Roe Phospholipid on Lipid Metabolism in Hyperlipidemic Mice

LIANG Peng , XU Yan-ping , CHENG Wen-jian , CHEN Li-jiao

2016, 32(11):1-7. DOI: 10.13982/j.mfst.1673-9078.2016.11.001

[Abstract](827) [HTML](0) [PDF 1.70 M](1141)

Abstract:
The hypolipidemic effect of large yellow croaker roe phospholipids was studied using a mouse model of hyperlipidemia. Mice were randomly divided into six groups: model, blank, soybean phospholipid (negative control), and low-dose (5 g/kg), medium-dose (15 g/kg) and high-dose (30 g/kg) large yellow croaker roe phospholipid group. After four weeks of feeding, the pathological changes of liver and phospholipid metabolism indices in the serum were investigated. The results indicated that large yellow croaker roe phospholipids suppressed mouse body weight gain. Compared with model group, medium-dose and high-dose large yellow croaker roe phospholipids significantly reduced levels of total cholesterol (TC), triglycerides (TG), and the values of atherogenic indexes 1 (AI1) and 2 (AI2) (p<0.05), but had no marked impact on levels of low-density lipoprotein-cholesterol (LDL-C) and high-density lipoprotein-cholesterol (HDL-C). The findings suggest that medium- and high-dose large yellow croaker roe phospholipids regulated lipid metabolism in hyperlipidemic mice. Based on the results of pathological histology of mouse liver, low-dose large yellow croaker roe phospholipid did not show significant effect on hepatocytes (p>0.05), whereas medium- and high-dose large yellow croaker roe phospholipids showed a significant effect on repairing hepatocellular degeneration. The results indicate that large yellow croaker roe phospholipids can prevent fatty degeneration of mouse liver and help reducing the risk of atherosclerosis.

2 Effects of Flavonoids from Rhizoma Smilacis glabrae on Lipid Metabolism and Antioxidation Status in Mice

ZHANG Qing-feng , FU Ying-juan , HUANG Zhan-wang , ZHENG Guo-dong

2016, 32(11):8-15. DOI: 10.13982/j.mfst.1673-9078.2016.11.002

[Abstract](602) [HTML](0) [PDF 947.74 K](1240)

Abstract:
The effects of total flavonoids from Rhizoma Smilacis glabrae (RSG) and its main ingredient–astilbin–on the lipid metabolism and antioxidation level in mice were investigated. Eighty ICR mice were randomly assigned to eight groups. Group I was a control group fed with a normal diet, and group II was a control group fed with a high-fat diet. T otal flavonoids and astilbin from RSG at concentrations of 1, 2, and 4 mg/mL were added to the drinking water for the other six groups, respectively. After eight weeks, the mice were dissected, the intraperitoneal adipose tissue (IPAT) and liver were collected and weighed, and the serum triglyceride (TG), total cholesterol, high-density cholesterol, and glucose levels were determined. The results showed that compared with the high-fat control group, RSG flavonoids had no effect on the food and water intake in mice, but could significantly reduce body weight gain and IPAT weight, as well as the TG content in serum. The mechanism study indicated that RSG flavonoids significantly improved the activities of carnitine acyltransferase and fatty acid beta-oxidase in mouse liver, but had no effect on the activity of fatty acid synthase, indicating that RSG flavonoids may reduce fat accumulation by promoting fat decomposition. RSG flavonoids could significantly enhance the activity of antioxidant enzymes and decrease the level of malondialdehyde (MDA), indicating that RSG flavonoids have in vivo antioxidant activity.

3 Anticancer and Immunoregulation Activities of a Polysaccharide from Russula vinosa

CHEN Jian , SHEN Chao-qun , HE Ting , YAN Sheng-fan

2016, 32(11):16-21. DOI: 10.13982/j.mfst.1673-9078.2016.11.003

[Abstract](808) [HTML](0) [PDF 1.68 M](1208)

Abstract:
Human cervical squamous cell carcinoma (SiHa) cells were chosen to study the in vitro antitumor activities of a Russula vinosa polysaccharide (HAP-I), and the results were confirmed using the scratch assay. Furthermore, an in vitro proliferation test with spleen cells from Kunming mice, neutral red uptake experiments, and analyses of the secretion of nitric oxide (NO) and interleukin-6 (IL-6) by RAW264.7 macrophages were conducted to study the anticancer and immunomodulatory activities of HAP-I. The results showed that in a concentration range of 125~2000 μg/mL, the inhibitory effect of HAP-I on SiHa was increased with increasing concentration and was dose-dependent to some extent. The scratch assay also demonstrated the inhibitory effect of HAP-I on the proliferation of SiHa. HAP-I could promote the proliferation of spleen cells from Kunming mice over a concentration range of 10~500 μg/mL, and this proliferation was dramatically promoted by the synergistic effect of concanavalin A (ConA) and lipopolysaccharide (LPS). The combination of HAP-I (at a concentration of 50 μg/mL or 100 μg/mL) and LPS had a significant effect on the proliferation; the optimal synergistic effect of HAP-I with ConA was found at 100 μg/mL. HAP-1 not only enhanced the ability of macrophages for neutral red uptake, but also increased the secretion of NO and IL-6 by macrophages, indicating that HAP-I has strong immunological activities.

4 Mechanism of Sensitization Induced by Nut Allergens

ZHANG Ai-lin , DUAN Xiao-jun , WANG Xiao-kun , MIAO Ying

2016, 32(11):22-28. DOI: 10.13982/j.mfst.1673-9078.2016.11.004

[Abstract](905) [HTML](0) [PDF 849.24 K](1804)

Abstract:
Nut allergenic protein was used as the antigen here to construct a mouse model of sensitization. The mechanism of sensitization of nut allergen was explored to provide an effective experimental basis for the safe development of nut foods and the evaluation of their safety. Six kinds of nuts were used as raw material and Kunming mice were used as test animals, which were fed with 0.01 mg/g nut protein extract by gavage to induce sensitization. On days 33 and 34, the mice were stimulated with 0.02 mg/g nut protein extract to induce sensitization, and pathological features were studied by measuring the serum IgE and IgG levels, the number of peritoneal mast cells, tryptase level, and hematological parameters in the mice. The results showed that the highest levels of IgE and IgG after sensitization in mice were 0.91 and 0.93, respectively, and histamine release rates in the positive, medium-dose, and high-dose groups were 58%, 40%, and 55%, respectively. The highest number of peritoneal mast cells in mice after in vitro stimulation of degranulation was found in the high-dose group, which also showed the highest tryptase activity. The medium- and high-dose groups, and the positive group exhibited high white blood cell counts (9.7±6.1, 9.6±2.4, and 9.2±2)×109/L, respectively, and the platelet counts were in descending order of low-dose group, medium-dose group, and high-dose group. The results indicated that after sensitization, the coagulation function of mice was significantly impaired, and the immune system was affected; the in vivo production of IgE antibody was induced, and the release mechanism of allergy mediators was activated, leading to the occurrence of anaphylactic reactions (type I hypersensitivity).

5 Comparative Study of High Fat Diet in Induced C57BL/6J Pseudo Germ-free Mice and Specific-pathogen-free (SPF) Mice

BIAN Heng-juan , ZENG Ben-hua , WANG Li , ZHONG Qing-ping , LI Wen-xia , WEI Hong , FANG Xiang , LIAO Zhen-lin

2016, 32(11):29-34. DOI: 10.13982/j.mfst.1673-9078.2016.11.005

[Abstract](2616) [HTML](0) [PDF 833.56 K](2726)

Abstract:
Gut microbiotas are closely related with the obesity of their host. Pseudo germ-free mice are a useful animal model for studying the relationship of gut microbiota with obesity and other related diseases. Twenty C57BL/6J eight-week-old male mice were administered with antibiotic cocktails in drinking water to remove the gut microbiota to establish the pseudo germ-free mouse model. These mice were randomly divided into two groups: control (CONV) group and high fat (HF) group, which were fed with a normal diet and a high-fat diet for eight weeks, respectively. Meanwhile, 20 specific-pathogen-free (SPF) mice were used as controls. Body weight, serum glucose levels, serum lipid levels, and insulin concentrations of the mice were measured by normal methods, and the areas of fat cells were calculated using software. The results revealed that body weight, fat pad, and perirenal fat weight of the HF pseudo germ-free mouse group were significantly lower than those of the HF SPF mouse group (p<0.001), and the insulin level and areas of fat cells in the HF pseudo germ-free mouse group were also significantly lower than those of SPF mice（p<0.01）. Pseudo germ-free mice in the HF diet group showed low bodyweight and a low-fat phenotype, which were extremely similar to those of germ-free mice. As a result, the pseudo germ-free mouse model, established using antibiotic cocktails, can be used to predict modulation results in germ-free mice and is an ideal animal model for exploring the relationship between gut microbiota and diseases.

6 Anti-colitis Effect of Fecal Microbiota Crude Extract via Suppressing the Nuclear Factor-κB Signaling Pathway

XU Min , MENG Yue-yue , JIN Da , ZHAO Li , HUO Gui-cheng

2016, 32(11):35-40. DOI: 10.13982/j.mfst.1673-9078.2016.11.006

[Abstract](758) [HTML](0) [PDF 1.01 M](1023)

Abstract:
The effect of crude extract of fecal microbiota on artificially-induced ulcerative colitis in mice was investigated in this study. A total of 64 healthy mice were randomly divided into four groups: blank (n=20), enteritis blank (n=20), sulfasalazine (SASP, n=12), and fecal microbiota transplantation (FMT, n=12). Mice assigned to the treated groups were allowed to freely drink 3% dextran sulfate sodium salt (DSS) solution for seven days, to establish the ulcerative colitis (UC) model. Subsequently, mice in the SASP and FMT groups were treated with SASP solution and crude extract of fecal microbiota for four weeks, respectively. Mice were observed for two weeks with a gavage performed once every two days. The results showed that compared with the enteritis blank group, crude extract of fecal microbiota significantly decreased serum interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α levels (p<0.05), reduced nuclear factor (NF)-κB protein expression, and increased the level of IκB protein expression. The results indicate that crude extract of fecal microbiota exerts an anti-colitis effect by suppressing activation of the NF-κB signaling pathway and has potential applications in clinical medicine.

7 Protective Effect of Plastein Reaction-modified Casein Hydrolysates on H2O2-induced Injury in Human Umbilical Vein Endothelial Cells

XU Jin-long , CHEN Fang-fang , PANG Jia-nan , LI Tie-jing

2016, 32(11):41-47. DOI: 10.13982/j.mfst.1673-9078.2016.11.007

[Abstract](813) [HTML](0) [PDF 695.02 K](1254)

Abstract:
Casein was hydrolyzed by neutrase (0.8 L), and then the hydrolyzed casein (HC) was modified with phenylalanine (PHE), histidine (HIS), and proline (PRO) through plastein reaction. In vitro 2,2-diphenyl-1-picrylhydrazyl (DPPH?) radical-scavenging abilities, hydroxyl radical-scavenging abilities, and reducing powers of the corresponding products (HCPHE, HCHIS, and HCPRO) were significantly higher than those of HC by 42.81%, 45.83%, and 30.51%, respectively (p<0.05). The modified products (HCPHE, HCHIS, and HCPRO) were incubated with human umbilical vein endothelial cells (HUVECs) for 24 h, and the protective effect of the modified products was evaluated after the HUVECs were injured using 300 μmol/L H2O2. Cell viability was measured using the CCK-8 method. The results showed that the cell viability of the groups treated with a high dose of HCPHE, HCHIS, or HCPRO was significantly higher than that of the group treated with HC by 7.86%, 5.21%, or 10.52% (p<0.05), respectively, and there was no significant difference between the high dose group and the group treated with tea polyphenols (TP) (p>0.05); furthermore, the relationship was dose-dependent. HCPHE, HCHIS, and HCPRO effectively decreased the leakage of lactate dehydrogenase (LDH), malondialdehyde (MDA) content, and superoxide dismutase (SOD) activity, compared with the HC group at the same concentration. Furthermore, HCPHE, HCHIS, and HCPRO significantly enhanced the activities of glutathione reductase (GSH-Rd) and catalase (CAT), while the change in the content of glutathione (GSH) in the cells did not significantly change. The study showed that HCPHE, HCHIS, and HCPRO had a good protective effect on H2O2-induced injury in HUVECs, with the protective effect being better than that of HC.

8 Effect of d-Borneol on Promoting the Absorption of Curcuminoids in HepG2 Cells

LUO Jing-jing , CHEN Jian-ping , HUANG Yan-bo , SU Jian-yu

2016, 32(11):48-55. DOI: 10.13982/j.mfst.1673-9078.2016.11.008

[Abstract](966) [HTML](0) [PDF 1.69 M](1424)

Abstract:
Western blotting was used to study the impact of d-borneol on the expression of ABC transporter proteins ABCB1, ABCC1, and ABCG2 in the cell membrane. Furthermore, flow cytometry was used to examine the impact of d-borneol on the membrane permeability of HepG2 cells, and a possible physical model for the action of d-borneol was investigated. The results showed that d-borneol significantly downregulated the expression levels of the transport proteins ABCB1, ABCC1, and ABCG2, and increased HepG2 cell membrane permeability, thus improving the absorption of curcuminoids. When HepG2 cells were pretreated with 20 μg/mL d-borneol for 12 h, followed by 24-h treatment using 20 μM curcumin (Cur), 40 μM demethoxycurcumin (DCur), and 40 μM bisdemethoxycurcumin (BDCur), respectively, the expression levels of ABCB1 in cells reduced from 0.7, 0.9, and 0.7 to 0.4, 0.6, and 0.5, respectively. When HepG2 cells were pretreated with 20 μg/mL d-borneol for 12 h, followed by 24-h treatment using 40 μM BDCur, the expression levels of ABCC1 and ABCG2 in the cells were reduced from 1.0 to 0.7 and from 0.5 to 0.3, respectively. Further flow cytometric analysis indicated that d-borneol could improve the membrane permeability of the HepG2 cell. When HepG2 cells were pretreated with 20 μg/mL d-borneol for 12 h, the fluorescence intensity of YO-PRO-1 in the cells increased from 20.79 (control group) to 45.51, and the fluorescence intensity was positively correlated with the concentration of d-borneol.

9 Isolation and Purification of Lactobacillus acidophilus Extracellular Proteins and Their Inhibitory Effect on the Proliferation of HT-29 Cells

JIA Yan , REN Xiao-dong , JIANG Yan , MING Zhu , ZHAO Pei , PANG Guang-chang , YAN Ya-li , CHEN Qing-sen

2016, 32(11):56-62. DOI: 10.13982/j.mfst.1673-9078.2016.11.009

[Abstract](722) [HTML](0) [PDF 888.41 K](1035)

Abstract:
To explore the related proteins secreted by Lactobacillus acidophilus and their functional roles in promoting gut homeostasis, the extracellular protein crude extract was obtained from L. acidophilus solid culture, and each fraction of the extracellular proteins was collected after purification and isolation using Sephadex G-100 gel chromatography. The amount of protein and molecular mass of each protein fraction were determined by Coomassie brilliant blue method and SDS-PAGE electrophoresis, respectively. Then, the inhibitory effect of each L. acidophilus extracellular protein fraction on the proliferation of HT-29 cells was investigated by 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assay. Two protein peaks were obtained after purification, their molecular weights were 67 ku and 37 ku, respectively, and their protein contents were 0.066 mg/mL and 0.021 mg/mL, respectively. HT-29 cells were treated with both 67 ku and 37 ku extracellular proteins at concentrations of 0.001 μg/mL, 0.01 μg/mL, 0.1 μg/mL, and 1 μg/mL for 12 h, 24 h, 48 h, or 72 h, respectively. Both proteins showed an inhibitory effect on the proliferation of HT-29 cells in a time- and dose-dependent manner. Among the tested concentrations, the inhibition rates of the 67 ku and 37 ku extracellular proteins at μg/mL on HT-29 cells were (38.41±1.94)% and (45.06±1.58)%, respectively. In conclusion, L. acidophilus cultured on solid medium produced two types of extracellular proteins (37 ku and 67 ku), which inhibited the proliferation of HT-29 cells to different degrees, and the 37 ku extracellular protein exhibited a relatively strong inhibitory effect.

10 Screening and Tracing of Anti-alzheimer Related Bioactive Constituents from Marine Fungi

ZHANG Yi , BAO Hai-Yan , NIE Ying-Ying , LUN Yan-Ling , DANG Zi-Wen , SONG Cai , SHAO Hai-Yan , HU Xue-Qiong

2016, 32(11):63-71. DOI: 10.13982/j.mfst.1673-9078.2016.11.010

[Abstract](970) [HTML](0) [PDF 1.20 M](1409)

Abstract:
Active constituents having anti-Alzheimer’s effects were screened and traced in 44 marine fungal strains. Acetylcholinesterase (AChE) inhibitory and antioxidant activities were assessed using the 5,5-dithio-bis-2-nitrobenzoic acid method and the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free-radical scavenging method, respectively. Bioautography and specific color-developing reagents were applied to investigate the diversity of bioactive substances and their structural types, respectively. HPLC-Q-TOF-ESI-HRMS was used to characterize representative fungal bioactive metabolites. The fermentation extracts of 32 strains in different culture media showed remarkable dual bioactivity against AChE and DPPH. These dual-bioactive strains originated from different fungal taxa. Bioautography revealed their diverse bioactive constituents. Chemical colorization further suggested that their active components were nitrogenated compounds (alkaloids), phenols, and other types of natural products. Based on HPLC-Q-TOF-ESI-HRMS analysis, a metabolite with molecular formula C16H13NO2 of a strain exhibited relatively strong inhibition effect against AChE. The present study revealed that marine fungi were an important source of diverse anti-Alzheimer’s active substances, and provided a foundation for future studies involving the isolation and elucidation of bioactive compounds.

11 Efficient Overexpression of Recombinant Nattokinase in Bacillus subtilis by Tandem Promoters

GE Chun-lei , LIU Zhong-mei , CUI Wen-jing , ZHOU Li , GUO Jun-ling , HU Yun-feng , ZHOU Zhe-min

2016, 32(11):72-77. DOI: 10.13982/j.mfst.1673-9078.2016.11.011

[Abstract](1282) [HTML](0) [PDF 930.74 K](1857)

Abstract:
In Bacillus subtilis WB800, the efficient secretory expression of nattokinase by tandem promoters was investigated. Several previously reported strong promoters were compared and arranged in tandem repeat sequence, and the optimal promoter for nattokinase and its maximum yield were determined. In this study, five recombinant strains harboring five different strong promoters were successfully constructed in Bacillus subtilis WB800, including pSG101 (PHpaII), pSG102 (PBcaprE), pSG103 (PluxS), pSG104 (PgsiB), and pSG105 (PyxiE), the secretory expression of nattokinase was achieved and the fibrinolytic activity was measured. The results indicated that the fibrinolytic activity of nattokinase mediated by promoter PHpaII (110.80 FU/mL) was higher than that mediated by the other four promoters. Subsequently, three plasmids were built by arranging the promoter PHpaII in multi-tandem sequences, including pSG106 (PHpaII-PHpaII), pSG107 (PHpaII-PHpaII-PHpaII), and pSG108 (PHpaII-PHpaII-PHpaII-PHpaII). The data showed that the highest yield of nattokinase (213.30 FU/mL) was achieved under promotion mediated by PHpaII-PHpaII-PHpaII, which increased the production of nattokinase by 92.51% compared with that achieved by mediation by the single promoter PHpaII. Through comparing five strong promoters and arranging them in tandem repeat sequences, the efficient expression of nattokinase was successively achieved in B. subtilis WB800. The highest fibrinolytic activity reached 213.30 FU/mL, significantly higher than that reported in the literature.

12 Changes in the Bioactive Content and Antioxidant Activity of Natto during Fermentation and In Vitro Digestion

XU Chun-ming , CHEN Ying-ying , PANG Gao-yang

2016, 32(11):78-84. DOI: 10.13982/j.mfst.1673-9078.2016.11.012

[Abstract](1038) [HTML](0) [PDF 567.42 K](1296)

Abstract:
Changes in the contents of active substances (including total phenols and isoflavones) during the fermentation of natto with Bacillus subtilis natto were studied. Levels of total phenols and isoflavones during the digestive process were measured in an in vitro digestion experiment, and the pattern of changes in antioxidant activity was studied. The results showed that after bacterial fermentation at high temperature, total phenolic content and isoflavone content in the after-ripening soybeans (24 h) were increased by 65.12% and decreased by 63.28%, respectively, compared with those of dry soybeans. The in vitro digestion experiments were conducted on the natto samples at different fermentation stages, and the release rate of total phenolics was 70.64% while the residual rate of isoflavones was 21.79%. Hydroxyl radical (?OH), 2,2-diphenyl-1-picrylhydrazyl (DPPH?), and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) scavenging abilities and oxygen radical absorbance capacity (ORAC) were used to determine antioxidant activity. After in vitro digestion, the scavenging ability of DPPH radicals was decreased in natto at different fermentation stages, and both ABTS scavenging ability and ORAC values were elevated. During the gastric digestion simulation stage, the scavenging ability of ABST radicals and the ORAC value in the after-ripening soybeans (24 h) were 1.80 and 2.22 times those of dry beans. During the intestinal digestion simulation stage, the scavenging ability of ABST radicals and the ORAC value of the after-ripening soybeans were 1.70 and 1.41 times those of dry beans. In summary, the antioxidant activity of the natto was increased after fermentation, and the natto from the gastric digestion stage showed higher antioxidant activity during the in vitro digestion process.

13 Antigenic Epitope Prediction and Structural Analysis of Glycoside Hydrolase Family 18 Chitinase Allergen from Domestic Silkworm (Bombyx mori) Pupa

ZHAO Xiang-Jie , LI Lin , YANG Rong-Ling , BI Yan-Hong , WANG Zhao-Yu , ZHAO Li , KUANG Zhe-Shi , MU Li-Xia , LI Bing

2016, 32(11):85-90. DOI: 10.13982/j.mfst.1673-9078.2016.11.013

[Abstract](1143) [HTML](0) [PDF 1.26 M](1127)

Abstract:
Domestic silkworm (Bombyx mori) pupa is an important byproduct of the sericulture industry and is commonly consumed as a snack owing to its nutritional properties and high content of proteins and unsaturated fatty acids. Recent progress in the study and development of diversified products prepared from silkworm pupa has boosted the revenue obtained from the sericulture industry. However, the severe allergy symptoms resulting from consuming silkworm pupa have limited its applications in the food and feed industries. It has been reported that the glycoside hydrolase family 18 chitinase (BmChi) from domestic silkworm (Bombyx mori) pupa is an important food allergen; however, no 3-dimentional structure studies have been conducted on the allergen BmChi. In this study, several bioinformatics software tools were used to comprehensively analyze the homology, secondary structure, hydrophilicity and hydrophobicity, molecular flexibility, antigenicity, and surface accessibility of BmChi, and subsequently, the B-cell epitope region was predicted. The results of this study can provide the foundation for an in-depth study on the immunological characteristics of BmChi and help developing methods for desensitization to silkworm pupa.

14 Heterologous Expression and Enzymatic Properties of Lipase LipTX from Thermophilic Bacterium Thermoanaerobacter sp. Strain X514

WEI Tao , YANG Kun-peng , JIA Wei-wei , MAO Duo-bin

2016, 32(11):91-97. DOI: 10.13982/j.mfst.1673-9078.2016.11.014

[Abstract](1064) [HTML](0) [PDF 1.10 M](1352)

Abstract:
The gene coding for a thermostable lipase LipTX (Teth514_0029) from thermophilic bacterium Thermoanaerobacter sp. strain X514 was cloned and the lipase LipTX was purified using affinity chromatography. The gene coding for lipase LipTX was amplified using polymerase chain reaction (PCR) method, and cloned into a pET15b vector, which was used to construct the recombinant plasmid pET15b-LipTX. The constructed pET15b-LipTX was transformed into host Escherichia coli BL21 (DE3) to express the recombinant enzyme via isopropyl β-D-1-thiogalactopyranoside (IPTG) induction. The purified recombinant enzyme was obtained after heat treatment and nickel-nitrilotriacetic acid (Ni-NTA) affinity chromatography. The sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) result showed that the relative molecular mass of lipase LipTX was approximately 28 ku. Study of the enzymatic properties indicated that LipTX displayed optimal activity at 70 ℃ and pH 7.5. Substrate specificity and kinetics experiments showed that LipTX could hydrolyze p-nitrophenyl ester (pNP-ester) substrates with different acyl chain lengths (from C8 to C12), and the most suitable substrate was pNP-decanoate. Additionally, this enzyme could hydrolyze triacylglycerols with long acyl chains (from C4 to C16) and showed the strongest enzymatic activity with tributyrin as the substrate. Furthermore, the recombinant lipase LipTX was found to have strong resistance to non-polar organic solvents (methanol, ethanol, acetone, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), hexane, and chloroform) and denaturants (sodium dodecyl sulfate (SDS), Tween-20, and Triton X-100). These results demonstrate that the lipase LipTX has a broad application prospect for biocatalysis and organic synthesis.

15 Laccase-mediated Cross-linking of Rice Protein with Ferulic Acid: Changes in Structural Properties and Antioxidant Activity

JIA Xiao , ZHAO Mou-ming , JIA Chun-xiao , TENG Jian-wen , WEI Bao-yao , HUANG Li , XIA Ning

2016, 32(11):98-105. DOI: 10.13982/j.mfst.1673-9078.2016.11.015

[Abstract](913) [HTML](0) [PDF 3.94 M](1131)

Abstract:
The enzymatic cross-linking of rice protein (RP) and ferulic acid (FA) and the antioxidant activity of the resultant product in the aqueous phase and emulsion were studied, and the FA content was investigated by high performance liquid chromatography (HPLC). Changes in the structural properties of RP were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), ultraviolet (UV) spectroscopy, Fourier transformed infrared (FT-IR) spectroscopy, and scanning electron microscopy. HPLC results showed that the FA easily underwent laccase-catalyzed oxidation, and the oxidation product could react with the subunits of RP, resulting in an increase of RP protein molecular weight. With increasing FA concentration, the absorbance band between 300 and 350 nm in the UV/visible spectra of RP gradually increased, and the cross-linked products had an orange-yellow color, indicating that the oxidation products bound covalently to the free amino groups of RP. After the enzymatic cross-linking of RP and FA, the secondary structure of RP changed, the contents of β-turn and α-helix were reduced by 13% and 2%, respectively, the contents of random coil and β-sheet were increased by 11% and 4%, respectively, and the microstructure of RP became loosened from the aggregated state. 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radical scavenging abilities of the RP-FA cross-linked product were increased from 32.31% to 71.43% and from 3.34 % to 77.61%, respectively, compared to those of RP. RP-FA cross-linked product could significantly reduce the level of hydroperoxide, 2-thiobarbituric acid reactive substances (TBARS), and hexanal in the emulsion, suggesting that cross-linking of RP can effectively enhance the antioxidant activity of RP.

16 Freeze-thaw Stability of the Emulsions Stabilized by Different Proteins

ZHU Xue-feng , TANG Chuan-he

2016, 32(11):106-110. DOI: 10.13982/j.mfst.1673-9078.2016.11.016

[Abstract](987) [HTML](0) [PDF 1.60 M](1614)

Abstract:
Soy protein isolate (SPI) (1% m/V) and whey protein concentrate (WPC) (1% m/V) were used as the test materials in this study. Protein particles formed from heat treatment were used to prepare an oil-in-water Pickering emulsion with an oil volume fraction of 0.4, and native SPI, WPC, or sodium caseinate (SC)-stabilized emulsions were employed as controls. The emulsions stabilized by native proteins and protein particles were stored at -20 ℃ for 24 h and then thawed at 30 ℃ for 3 h in an incubator; this freeze-thaw cycle was repeated three times. The freeze-thaw stability of the emulsions stabilized by the native proteins and protein particles was investigated, including the droplet size distribution, degree of coalescence and flocculation, creaming index, situation of oil floating, microstructure of the fresh emulsion, and emulsions after each freeze-thaw cycle. The results showed that part of the emulsions was inevitably damaged during the thawing process, while the Pickering emulsion stabilized by the SPI particles that were produced from heat-induced aggregation had excellent freeze-thaw stability. This result may provide an effective technical approach for the study and development of some oil-in-water emulsions frozen foods, heat-sensitive bioactive substances, and medicines requiring storage at low temperature.

17 Effect of Oxidative Modification by Peroxyl Radical on the Structure of Rice Protein

WU Wei , LI Tong , CAI Yong-jian , WU Xiao-juan , LIN Qin-lu

2016, 32(11):111-116. DOI: 10.13982/j.mfst.1673-9078.2016.11.017

[Abstract](916) [HTML](0) [PDF 909.36 K](1202)

Abstract:
The peroxyl radicals derived from the thermal decomposition of different concentrations of 2,2’-azobis (2-amidinopropane) dihydrochloride (AAPH) under aerobic conditions were selected to be representative of lipid peroxidation-derived lipid radicals, and the effect of oxidative modification by peroxyl radicals on the structure of rice protein was studied. The results showed that when the concentration of AAPH increased from 0 to 25 mmol/L, the protein carbonyl and disulfide contents of rice protein increased from 3.77 and 13.88 nmol/mg to 7.23 and 15.73 nmol/mg, respectively, while the free sulfhydryl content of rice protein decreased from 7.32 to 1.97 nmol/mg, indicating that the peroxyl radical induced the oxidation of rice protein. Fourier transform infrared spectroscopy indicated that the oxidation of the protein led to a decrease in α-helix and β-sheet motifs, and an increase in β-turn and random-coil motifs. As the extent of rice protein oxidation increased, the particle size of rice protein increased from 126 nm to 216 nm and the surface hydrophobicity decreased from 1053 to 568. Meanwhile, the wavelength of the maximum emission peak of intrinsic fluorescence was blue-shifted, and the intrinsic fluorescence intensity was decreased. Besides, the content of high-molecular aggregates in the molecular weight distribution of rice protein gradually increased. The results indicated that the oxidation of rice protein induced by peroxyl radicals changed the structure of rice protein, and formed oxidative aggregates.

18 Effect of Garlic Essential Oil on the Production of Phenylethylamine and Tyramine by Enterococcus faecium and Enterococcus faecalis

ZHANG Ya-qing , LU Shi-ling , HUANG Fa-tian , ZHENG Ting-ting , DAI Na-na , LI Bin-bin

2016, 32(11):117-122. DOI: 10.13982/j.mfst.1673-9078.2016.11.018

[Abstract](875) [HTML](0) [PDF 867.45 K](1330)

Abstract:
The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of garlic essential oil against two phenylethylamine-and tyramine-producing bacteria-Enterococcus faecalis and Enterococcus faecium-were measured in vitro using the double tube dilution method. The effects of a variety of concentrations of garlic essential oil on the two strains with high phenylethylamine-and tyramine-production were measured by high performance liquid chromatography (HPLC), to determine the inhibitory effect of garlic essential oil on biogenic amine production by the two strains. The results showed that garlic essential oil displayed sstrong antimicrobial activity against E. faecalis and E. faecium, and the corresponding maximum inhibitory rates (IRs) reached 52.41% and 48.20%, respectively. The antimicrobial effect increased as the concentration increased. When the amount of added garlic essential oil was ? MIC, it showed an inhibitory effect on the growth of E. faecalis and E. faecium. At a concentration of 0.025%, the garlic essential oil could significantly reduce the production of phenethylamine and tyramine by the test strains; the production of phenylethylamine and tyramine was reduced by 26.61% and 15.54%, respectively, from of the control. The result indicated that garlic essential oil exhibited a significant inhibitory effect on E. faecalis and E. faecium, thereby reducing the production of phenethylamine and tyramine.

19 Effect of Cassava Starch on the Gel Properties of Pork Salt-soluble Muscle Proteins

LI Jun-guang , JIANG Ai-min , BAI Yan-hong , ZHANG Hua , WU Yue

2016, 32(11):123-127. DOI: 10.13982/j.mfst.1673-9078.2016.11.019

[Abstract](739) [HTML](0) [PDF 1.91 M](1439)

Abstract:
The effect of cassava starch (CS) on the gel functional properties of porcine salt-soluble muscle proteins (SSMP) was investigated. Changes in texture, dynamic rheological properties, and water-holding capacity (WHC) of the gel were determined using a texture analyzer, rheometer, and centrifugation, respectively. Changes in water distribution and microstructure were analyzed by low-field nuclear magnetic resonance (LF-NMR) and scanning electron microscopy (SEM), respectively. The results showed that addition of cassava starch improved the textural properties and WHC of porcine SSMP gel. Gel-forming temperature changed, with maximum storage modulus (G′max) values of SSMP and CS-SSMP at 72 ℃ and 80 ℃, respectively. Additionally, maximum gel hardness, springiness, and WHC were determined as 379.02 g, 0.85, and 85.16%, respectively, with the addition of 1.5% cassava starch. LF-NMR results indicated that the ratio of bound and immobile water in the gel increased with the addition of 1.5% cassava starch, thus enhancing the WHC of the gels. SEM results showed that cassava starch was present in the interstitial spaces of the protein network via a filling effect, which made the network microstructure of the gel more compact and orderly.

20 Study on the Ability of Lactobacillus delbrueckii subsp. bulgaricus to Hydrolyze Casein and Analysis of the Hydrolysate

MAO Xue , GONG Ya-li , ZHANG Guo-fang , ZHAO Yu-cai , LIU Li-bo , LIU Yang , WANG Ting-ting , WANG Jing-ying , DUAN Chun-ying , LI Chun

2016, 32(11):128-133. DOI: 10.13982/j.mfst.1673-9078.2016.11.020

[Abstract](920) [HTML](0) [PDF 1.57 M](1470)

Abstract:
In order to carry out an in-depth study on casein hydrolysis by Lactobacillus bulgaricus, Lactobacillus delbrueckii subsp. bulgaricus strain ATCC 11842 was used, with Lactobacillus delbrueckii subsp. bulgaricus strains KLDS 08007, KLDS 08009, KLDS 08010，KLDS 08014, and KLDS 08018 as controls. The degree of casein hydrolysis and peptide content of the fermentation broths from different strains were measured, and the casein hydrolysate of ATCC 11842 was further analyzed by sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and liquid chromatography-mass spectrometry (LC-MS). The results showed that ATCC 11842 had the strongest hydrolytic ability with the degree of hydrolysis as 13.89%, and the peptide content 0.63 mg/mL. The activities of cell envelope proteinases (CEPs) of the six strains were measured and compared with their hydrolytic abilities, and the results showed that their proteinase activity was positively related to their hydrolytic ability. ATCC 11842 exhibited the highest enzyme activity (up to 15.52 U/mL), and its specific enzyme activity was 6.73 U/mg. It can be seen from the electrophoretogram that the casein was hydrolyzed gradually with a prolonged fermentation time and 3.4~21.0 ku polypeptides were produced. As shown from the LC-MS analysis of the casein hydrolysate, 77 types of peptide fragments containing 6~25 residues were produced after casein hydrolysis, and the peptides containing 6~7 residues and 8~14 residues accounted for 9% and 77% of the total types of polypeptides, respectively.

21 Effect of Deacidification by Fermentation with Lactobacillus fermentum on the Qualities of Plum (Prunus salicina Lindl. cv. Sanhua) Juice

YUAN Xing-xing , YU Yuan-shan , WU Ji-jun , XIAO Geng-sheng , XU Yu-juan , ZHOU Bo

2016, 32(11):134-138. DOI: 10.13982/j.mfst.1673-9078.2016.11.021

[Abstract](773) [HTML](0) [PDF 569.61 K](1069)

Abstract:
The changes in the viable count of Lactobacillus fermentum, sugar component, organic acids content, pH value, titratable acid content, total phenolic content, antioxidant capacity, anthocyanin content, and color of the Sanhua plum juice during the deacidification by fermentation with L. fermentum were investigated in this paper. The results showed that the L. fermentum grew slowly in the plum juice at 30 ℃, and its population appeared to be stable after six days of fermentation. During the fermentation, L. fermentum consumed the sugar in the plum juice slowly, using only a small amount of glucose to maintain its metabolism and growth, while consuming malic acid rapidly. With the depletion of malic acid and production of a small amount of lactic acid, the pH of the plum juice increased quickly with a rapid reduction in the total titratable acid content. After eight days of fermentation, the population of L. fermentum in the plum juice increased from 7.01 log CFU/mL to 7.91 log CFU/mL, the malic acid was completely consumed, while 73.82% of the glucose and 97.7% of the fructose remained. The pH value increased by 0.38, titratable acid content reduced by 43.7%, while 82.23% of the total phenolics remained. The antioxidant activity (oxygen radical absorbance capacity (ORAC) value) increased by 14.90%, 50% of anthocyanin remained, and no significant changes (p>0.05) were observed in the color of the juice sample. Hence, the use of L. fermentum for the fermentation of Sanhua plum juice can not only reduce the acidity of the plum juice, but also retain the nutrient content of plum juice well.

22 Microflora Analysis and Preliminary Identification of Dominant Spoilage Bacteria in Refrigerated Cololabis saira

DONG Wen-xia , WANG Xin

2016, 32(11):139-145. DOI: 10.13982/j.mfst.1673-9078.2016.11.022

[Abstract](952) [HTML](0) [PDF 839.74 K](1377)

Abstract:
A deeper understanding of the dominant spoilage bacteria during storage will help develop methods to inhibit target bacteria, thus extending the shelf life of Cololabis saira. Changes in the bacterial phase of the bacteria causing spoilage of Cololabis saira stored at 4°C were investigated, the dominant spoilage bacteria were isolated and identified, and their spoilage potential was verified. The results showed that the shelf life of refrigerated Cololabis saira was six days. A total of 13 strains that belonged to seven genera, were isolated during refrigerated storage, including seven gram-positive and six gram-negative bacteria. Furthermore, according to the change in the proportion of each strain in the bacterial phase and their effects on the total volatile basic nitrogen (TVB-N) value of sterilized fish juice, Strains 13 (Enterobacter sp.), 12 (Shewanella sp.), 7, and 9 (Acinetobacter sp.) were identified. These bacteria had different influences on the TVB-N, trimethylamine (TMA) and 2-2-thiobarbituric acid (TBA) content of Cololabis saira. Strain 12 (Shewanella sp.) accelerated TMA generation, Strain 13 (Enterobacter sp.) showed significant influence on TVB-N value, Strain 7 (Acinetobacter sp.) significantly increased TBA content, while Strain 9 (Acinetobacter sp.) affected all three indicators. The results demonstrated that the four identified strains showed strong spoilage potential for Cololabis saira during refrigerated storage.

23 Risk Reduction Assessment of Combined Acidic Electrolyzed Water and High Hydrostatic Pressure Effects on Vibrio parahaemolyticus in Shelled Shrimp

DU Su-ping , ZHANG Zhao-huan , LOU Yang , XIAO Li-li , PAN Ying-jie , ZHAO Yong

2016, 32(11):146-154. DOI: 10.13982/j.mfst.1673-9078.2016.11.023

[Abstract](790) [HTML](0) [PDF 1.54 M](1050)

Abstract:
Acidic electrolyzed water (AEW) was combined with high hydrostatic pressure (HHP) in this study to inactivate Vibrio parahaemolyticus in shelled shrimp, and the risk reduction of this technique was evaluated using a quantitative microbial risk assessment (QMRA) model. The results showed that the risk of V. parahaemolyticus infection could be significantly reduced using this novel sterilization technology. Compared with untreated shelled shrimp, the final contamination level of V. parahaemolyticus was decreased from 1.98 to -2.53 log CFU/g, and the mean infection risk was reduced from 1.28×10-1 to 2.01×10-3 after combined treatment with AEW and HHP. The average cases of V. parahaemolyticus infection were reduced from 1280 to 20 per 10,000 people, with a risk reduction rate of 98%. The sensitivity analysis showed that the treatment pressure, treatment time, and sodium chloride concentration required for electrolysis, all had a negative correlation with risk of V. parahaemolyticus infection. In addition, this study also indicated that the novel sterilization technique could be combined with cold chain logistics to be applied in the production chain of the food industry, thus minimizing the risk of V. parahaemolyticus infection and providing strong technical support to safeguard public health.

24 Effects of HIU-aided Pretreatment of Crude Protein in Fish Skin: Separation and Structure

LIANG Jian-hua , ZHU Zhi-wei , CHEN Zhu-bing

2016, 32(11):155-161. DOI: 10.13982/j.mfst.1673-9078.2016.11.024

[Abstract](782) [HTML](0) [PDF 1.07 M](1155)

Abstract:
Due to the larger consumption of energy, solvent, and pretreatment period during the conventional separation of crude protein in fish skin, a method of HIU-aided pretreatment of fish skin was provided. In order to reveal the effects of different ultrasonic pulses ways on fish skin and the structure of fish collagen fiber, five following parameters were investigated: total content of proteins removed, loss of collagen during the HIU pretreatment, structure of collagen fiber after the HIU pretreatment, subsequent extraction yield of collagen and SDS-PAGE patterns of collagen. After pretreatment by the way of HIU3 s on 2 s off for 60 min, the content of protein in fish skin removed was 37.37 mg/g without significant loss of collagen (0.63 mg/g). SEM figures showed that, the loose of fish skin and the sufficient extension of collagen fiber were convenient for the subsequent collagen extraction after pretreatment by the way of HIU3 s on 2 s off. FT-IR spectra obtained for fish collagen fiber confirmed the integrated conformation of fish skin collagen. Furthermore, collagen with structural integrity well maintained yielded the highest.

25 Laccase-induced Construction of Edible Double-network Gels Based on Soy Protein and Sugar Beet Pectin

CHEN HAO , ZHUO Ting-ye , QIU Shuang , LIU Yan , ZHU Qiao-mei , YIN Li-jun

2016, 32(11):162-169. DOI: 10.13982/j.mfst.1673-9078.2016.11.025

[Abstract](851) [HTML](0) [PDF 2.21 M](1088)

Abstract:
Soy protein isolate is commonly used as a gel material in the food industry. However, it is sensitive to the environment, with low mechanical property and poor formability. The gelation properties of the proteins could be improved by protein modification using polysaccharides. In the present study, an appropriate amount of sugar beet pectin was added to soy protein isolate, and the concentrations adjusted to construct double-network gels, in order to achieve the goal of improving the mechanical and textual properties of the protein single-network gel. A two-step process (thermal treatment and laccase catalysis) was applied to the construction of double-network gel. With increasing concentrations of soy protein isolate, the springiness of the double-network gel was improved; with increasing concentrations of sugar beet pectin, the hardness and chewiness of the double network gel was enhanced. When the concentration of soy protein isolate was 11%, the concentration of sugar beet pectin was 1.5%, and the enzyme dosage was 100 nkat/g substrate, the highest water holding capacity (95.28%) of the double network gel was achieved. When the concentration of soy protein isolate was 8%, the concentration of sugar beet pectin was 2.5%, and the enzyme dosage was 100 nkat/g substrate, the hardness and the chewiness of the double network gel were 4.25/g and 4.06/J, respectively. The construction of soy protein isolate-sugar beet pectin double-network gels improved the mechanical property and water holding capacity of gels, resulting in the formation of a more ordered gel network structure.

26 Improved Shelf Life of Germinated Brown Rice Cakes

GE Yun , WU Feng-feng , LI Jing , YANG Na , JIN Zheng-yu , XU Xue-ming

2016, 32(11):170-176. DOI: 10.13982/j.mfst.1673-9078.2016.11.026

[Abstract](907) [HTML](0) [PDF 845.96 K](1067)

Abstract:
The improved shelf life of germinated rice cakes was studied in this paper. The shelf-life properties of rice cakes prepared by pure brown rice flours with different germination times, or mixed brown rice flours in different ratios were analyzed and compared using texture profile analysis, differential scanning calorimetry (DSC), and sensory analysis, and the pattern changes in the main ingredients of brown rice during germination were analyzed. The results showed that the shelf life of rice cakes was increased with prolonged germination time, and the brown rice flours with different germination times, mixed in a specific blending ratio, could also further enhance this effect. The optimum shelf life of rice cakes was observed when the 2 d and 3 d germinated brown rice flours were mixed in a ratio of 1:2. The main reasons accounting for the improved shelf life of the rice cakes were the starch degradation. This resulted in the decrease of total starch, amylose and amylopectin content (from day zero to four of germination, the content of total starch, amylose, and amylopectin decreased from 77.26%, 4.08%, and 73.18% to 46.77%, 2.56%, and 44.21%, respectively), and the increase in content of dextrin and small-molecule sugar (from day zero to four of germination, the reducing sugar content increased from 0.98% to 8.22%). Furthermore, the improved shelf life of the final products was also influenced by changes in protein, fat and other components in the germination period and the interaction of these compounds.

27 Effect of Ultraviolet-C Irradiation on Phenolic Compounds and Antioxidant Activity of Postharvest Actinidia arguta Fruit

JIAO Zhong-gao , HU Li-na , ZHANG Chun-ling , LIU Hui , YANG Wen-bo , LV Zhen-zhen , WANG Si-xin , LIU Jie-chao

2016, 32(11):177-183. DOI: 10.13982/j.mfst.1673-9078.2016.11.027

[Abstract](893) [HTML](0) [PDF 887.28 K](1117)

Abstract:
The effect of ultraviolet (UV)-C irradiation at different dosages on fruit quality, phenolic contents, and antioxidant activity of Actinidia arguta during storage were investigated. Fresh fruits were exposed to different doses (1.05, 2.1, and 4.2 kJ/m2）of shortwave UV-C immediately after harvest, while fruit firmness, total soluble solid content, total phenolic content, flavonoid content, anthocyanin content, and antioxidant capacity of Actinidia arguta were determined during room-temperature storage and cold storage. The results showed that UV-C treatment increased the total soluble solid content, delayed the decrease in fruit ?rmness, signi?cantly enhanced the synthesis and accumulation of total phenolics, total ?avonoids, and anthocyanins, and effectively improved the antioxidant activity of fruit during storage. When stored at 25 ℃, the fruits treated with 4.2 kJ/m2 UV-C irradiation showed the highest content of phenolic compounds after five days of storage. During storage at 0 ℃, the highest phenolic content was reached in fruits treated with 1.05 kJ/m2 UV-C irradiation and stored for three days. These results suggest that UV-C irradiation can serve as a safe and non-toxic postharvest treatment method to improve and enhance fruit quality, phenolic content, and antioxidant activity of Actinidia arguta fruits.

28 Effect of Postharvest Gibberellic Acid Treatment on the Chilling Injury of Tomato Fruits during Cold Storage

ZHU Zhen , DING Yang , ZHAO Jin-hong , NIE Ying , ZHANG Yu , TANG Xuan-ming

2016, 32(11):184-189. DOI: 10.13982/j.mfst.1673-9078.2016.11.028

[Abstract](809) [HTML](0) [PDF 2.06 M](882)

Abstract:
The effect of exogenous gibberellic acid (GA3) treatment on chilling stress tolerance of harvested tomato fruits was investigated in this study. Solanum lycopersicum L. ‘Zhefen’ No. 702 at the mature green stage was used as the test material, treated with 0, 0.2, 0.5, or 1 mM GA3 aqueous solution at room temperature, and stored at 4 ℃. Tomato samples were collected on days 0, 3, 7, 14, 21, and 28, and stored at room temperature for three days before the chilling injury index was measured to determine the most suitable GA3 concentration. In addition, microstructure changes, malondialdehyde (MDA) content, electrolyte leakage, and changes in the activities of phospholipase C (PLC), phospholipase D (PLD), lipoxidase (LOX), and polygalacturonase (PG) were measured. These results showed that compared with the control, 0.5 mM exogenous GA3 treatment effectively alleviated the chilling injury symptoms, protected cellular microstructure, and significantly inhibited increases in the MDA content, electrolyte leakage, and activities of PLC, PLD, LOX, and PG, thus enhancing the chilling stress tolerance of postharvest tomato fruits.

29 Effect of Detoxified, Partially Defatted Flaxseed Meals on the Quality of Steamed Bread

CAO Wei-wei , HUANG Qing-de , TIAN Guang-jing , DENG Qian-chun

2016, 32(11):190-196. DOI: 10.13982/j.mfst.1673-9078.2016.11.029

[Abstract](752) [HTML](0) [PDF 611.60 K](1029)

Abstract:
The effect of different levels of detoxified, partially defatted flaxseed meals on the specific volume, color, texture, sensory characteristics, nutritional quality, and other characteristics of steamed bread was studied. The results showed that adding excessive amount of detoxified, partially defatted flaxseed meals could decrease the specific volume and expansion ratio of steamed bread, and the bread turns dark in color. The textural test showed that the hardness, gumminess, and chewiness of steamed breads increased continuously with increasing amounts of detoxified, partially defatted flaxseed meals, while springiness, cohesiveness, and resilience decreased continuously. The fat, protein, and ash contents increased, but the content of amino acids (except for proline) showed an increasing trend. Moreover, the lignan content also significantly increased (p<0.05), and lignan content in a steamed bread containing 15% detoxified, partially defatted flaxseed meals could be up to 3.34 mg/g. The sensory evaluation score of steamed bread gradually decreased with increasing amount of detoxified, partially defatted flaxseed meals. However, the sensory evaluation scores of the steamed breads with additions of 3% and 6% of detoxified, partially defatted flaxseed meals (above 90) were significantly higher than the other tested steamed breads, and showed no significant differences between each other. Since the steamed breads with addition of 6% detoxified, partially defatted flaxseed meals had more fat, protein, lignans, and other nutrients, the optimum amount of detoxified partially defatted flaxseed meals that should be added to steamed bread was determined as 6%.

30 Effect of Ultrasound and Ultrasound-assisted Osmotic Dehydration on Infrared Radiation Drying Characteristics of Peach Slices

ZHANG Peng-fei , LV Jian , BI Jin-feng , LIU Xuan , ZHOU Lin-yan , GUAN Yun-jing , XIAO Min

2016, 32(11):197-202. DOI: 10.13982/j.mfst.1673-9078.2016.11.030

[Abstract](972) [HTML](0) [PDF 1016.29 K](1186)

Abstract:
To explore the effect of ultrasound (UL) and ultrasound-assisted osmotic dehydration (ULOD) pretreatments on water transfer in peach slices and the drying characteristics of infrared radiation drying, samples were pretreated with UL and ULOD for different time followed by infrared radiation drying at 80 ℃. Low-field nuclear magnetic resonance (LF-NMR) was used to measure the transverse relaxation times (T2) of the pretreated peach slices. Changes in water status and distribution were analyzed, the drying characteristics curve was obtained, and the effects of water status and distribution on the drying characteristics were explored. The results showed that UL decreased the soluble solid content, and ULOD significantly improved the soluble solid content and decreased the water content. Both pretreatments affected the water status and distribution. UL increased the transverse relaxation times of immobilized water (T22) and free water (T23), indicating that the degree of freedom of water increased. As a result, UL enhanced the drying rate and increased the water effective diffusion coefficient (Deff). ULOD decreased the transverse relaxation time of bound water (T21), immobilized water (T22), and free water (T23). The free water content was significantly reduced, and the immobilized water and bound water content increased relatively, thus reducing the drying rate and decreasing the Deff of infrared radiation drying. This study provides the theoretical basis for the study of the effects of UL and ULOD pretreatments on water transfer and diffusion characteristics of fruite slice treated by infrared radiation drying.

31 Effect of the Pretreatment Combining Glycation and Pulsed Electric Fields on the Antigenicity and Structure of β-Lactoglobulin

TU Zong-cai , TIAN Ming , WANG Hui , YANG Wen-hua , LI Xue , HUANG Tao

2016, 32(11):203-208. DOI: 10.13982/j.mfst.1673-9078.2016.11.031

[Abstract](983) [HTML](0) [PDF 661.90 K](1251)

Abstract:
β-Lactoglobulin (β-Lg) is a nutrient-rich bovine whey protein, but it is a major allergen in milk. In this study, we investigated β-Lg, and the changes in the antigenicity of the β-Lg in β-Lg-galactose conjugates and the structural properties of reaction products as determined using indirect competitive enzyme-linked immunosorbent assay, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), circular dichroism spectroscopy, and fluorescence spectroscopy. The reaction conditions were as follows: mass ratio of β-Lg and galactose, 1:2, modification temperature, 60 ℃, reaction time, 3 h and reaction pH 7.4. The pulsed electric field (PEF) intensity was varied. The results showed that after the pretreatment with glycation and PEF, the antigenicity of β-Lg significantly reduced, and PEF pretreatment promoted the decrease in antigenicity. When the sample was treated with PEF at 25 kV/cm for 90 μs, followed by glycation, the largest drop in the antigenicity of β-Lg was achieved (about 72.9%). After pretreatment with glycation coupled with PEF, the molecular weight of β-Lg increased. The contents of α-helix and β-turns decreased while the content of β-sheet and random coil increased. The intrinsic fluorescence intensity and surface hydrophobicity decreased, and the free sulfhydryl content first increased and then decreased. In this study, we describe a novel method for producing low-allergic β-Lg.

32 Influence of an Electric Field on the Interaction between Konjac-derived Glucomannan and Carrageenan

WANG Shu-na , TAN Xiao-dan , CHEN Han , HUANG Rong-xun , WANG Min , XIE Bing-qing , LIN Hai-bin , PANG Jie

2016, 32(11):209-214. DOI: 10.13982/j.mfst.1673-9078.2016.11.032

[Abstract](780) [HTML](0) [PDF 849.94 K](1274)

Abstract:
In order to study the influence of an electric field on the mechanism underlying the interaction of konjac glucomannan and carrageenan, 5 kV high-voltage direct current (oxygen anion) was used to treat konjac-derived glucomannan (KGM) and carrageenan powders, and samples were prepared from the two powders for testing. The results showed that the elastic modulus G′ of the composite gel of KGM and carrageenan treated by the electric field for 9 min was significantly greater than the viscous modulus G′′ all the time. The gel network was flexible, and the entanglement and penetration of the molecular chains were significant. In the frequency scan range, the elastic modulus G′ of KGM and carrageenan composite gel was significantly greater than the viscous modulus G′′, suggesting that the gel network structure already had a certain strength. When the concentration of polysaccharide was 1% and the blending ratio of konjac-derived glucomannan and carrageenan was 1:4, the maximum gel strength was reached. The maximum gel strength was also achieved when the sample was treated by the electric field for 6 min or heated at 75℃ for 30 min. Fourier infrared spectroscopy analysis was performed. The infrared absorption spectra showed only changes in the intensity of absorption peaks and no new absorption peaks, suggesting that the electric field did not significantly change the chemical structure or properties.

33 Effect of Salting Temperature on the Protein Phosphorylation of Mutton

ZHANG Cai-xia , WANG Zhen-yu , LI Zheng , DU Man-ting , ZHANG De-quan

2016, 32(11):215-221. DOI: 10.13982/j.mfst.1673-9078.2016.11.033

[Abstract](780) [HTML](0) [PDF 2.28 M](871)

Abstract:
The effect of different salting temperatures on the phosphorylation level of myofibrillar and sarcoplasmic proteins in mutton was investigated. The topside muscles from both hind legs were removed immediately after slaughter and aged at 4 ℃ for 24 h, and then three salting treatment groups were set up at -1 ℃, 4 ℃, and 25 ℃. Samples from each group were collected at 0 h, 8 h, 16 h, and 24 h, and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) combined with fluorescence staining was employed to analyze phosphorylation levels. The results showed that the global phosphorylation level (P/T) of myofibrillar proteins increased with decreasing salting temperature. After 8 h of salting, the global phosphorylation level of the myofibrillar proteins with freezing temperature treatment was significantly higher than that of the myofibrillar proteins with room temperature treatment (p<0.05), and no significant difference was found between the samples salt-treated for 16 h and those treated for 24 h. The results of the sarcoplasmic protein phosphorylation showed the opposite trend, and the global phosphorylation level of sarcoplasmic proteins decreased with decreasing salting temperature. After 8 h of salting, the global phosphorylation level of the sarcoplasmic proteins with freezing temperature treatment was significantly lower than that of the sarcoplasmic proteins with room temperature treatment (p<0.05), and no significant difference was found between the samples salt-treated for 16 h and those treated for 24 h. The effect of salting temperature on the phosphorylation level of individual protein bands was different. The phosphorylation levels of actin and aldolase increased with increasing salting temperature, while those of myosin and enolase decreased. Therefore, salting temperature can regulate the meat quality by influencing the phosphorylation of muscle proteins.

34 Changes in Aromatic Composition of Apple Vinegar with Application of Partial Block Freeze-concentration: A Pilot Study

MEN Ge-yang , ZHONG Rui-min , LIAO Cai-hu , DENG Ze-yuan , XIAO Zi-jun , LAO Yong-da

2016, 32(11):222-227. DOI: 10.13982/j.mfst.1673-9078.2016.11.034

[Abstract](717) [HTML](0) [PDF 1.14 M](1148)

Abstract:
A partial block freeze-concentration apparatus (50 L) was applied to concentrate apple vinegar in a pilot study, and the aromatic composition changes in the vinegar and ice samples before and after the concentration process were compared using gas chromatography-mass spectrometry (GC/MS). During this process, the refrigerant interlayer temperature and stirring rate of the freeze concentrator at the beginning stage were controlled at -12.0 ℃ and 300 r/min, respectively. When the ice on the inside wall of the crystallizing tank reached a thickness of 0.50 cm, the refrigerant interlayer temperature and stirring rate were changed to -16.0 ℃ and 500 r/min, respectively, which were maintained until the end of the concentration process. After 11 h, 21.70 kg of concentrated apple vinegar with 9.50% content and 27.84 kg block ice with 0.66% entrainment could be obtained from the initial 50.00 kg apple vinegar. The concentration index and solute yield were 2.13 and 92.24%, respectively. The total loss of aromatic compounds from the block ice was just 3.12%, and the loss rates of characteristic components, such as benzaldehyde, octanoic acid, 4-ethylbenzoic acid butan-2-yl ester, phenylethyl alcohol, and acetic acid 2-phenylethyl ester, were in the range of 3.33~7.47%. However, when the recovery liquid from thawed ice was re-concentrated using similar two-step controlling parameters, the main components recovered were the solutes (e.g. organic acids), but no significant concentration effect was observed in the trace amounts of residual aromatic components.

35 Effects of Ultrafine Grinding on the Extraction Rate and Antioxidant Properties of the Active Ingredients of Lotus Plumule

CHEN Ming , XUE Qi , SHEN Ting , WANG Xin-feng , QIANG Qian , LUO Hai-qing , ZHU Cui-ling , WU Hai-feng , WU Lei , LI Peng-xia , HU Wei-cheng

2016, 32(11):228-234. DOI: 10.13982/j.mfst.1673-9078.2016.11.035

[Abstract](1224) [HTML](0) [PDF 1.60 M](1383)

Abstract:
To evaluate the effect of ultrafine grinding on the particle size, microstructure, extraction rates of total phenolics and flavonoids, and antioxidant capacity of lotus plumule, the total phenolic and flavonoid contents were measured using NaNO2-Al (NO3)3 and Folin-phenol reagent methods, respectively. Antioxidant activity was evaluated by 2,2′-diphenyl-1-picrylhydrazyl (DPPH) free radical-scavenging activity, reducing power assay, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) scavenging activity, oxygen radical absorbance capacity (ORAC), and cellular antioxidant activity (CAA) assay. The results showed that for the samples treated by ultrafine grinding, the median particle size reduced, the cell wall-breaking rate increased, and the extraction rates of total flavonoids and phenolics increased by 21.82% and 24.09%, respectively. In terms of antioxidant capacity, ultrafine grinding treatment significantly enhanced DPPH free radical-scavenging activity, reducing power, ABTS scavenging activity, ORAC, and CAA. In conclusion, ultrafine grinding could improve the physicochemical properties of lotus plumule powder and increase the dissolution rates of the active ingredients (total phenolics and total flavonoids) in lotus plumule. Meanwhile, ultrafine grinding significantly increased antioxidant capacity and could serve as a pretreatment method in the development of functional food products with lotus plumule as the raw material.

36 Effect of Enzymatic Modification on Structural Changes of Corn Flour Protein

SUN Bu-yun , LIN Zi-mu , YANG qiang , ZHENG shuang , LI Xin-hua , QI Bing

2016, 32(11):235-240. DOI: 10.13982/j.mfst.1673-9078.2016.11.036

[Abstract](860) [HTML](0) [PDF 854.42 K](1369)

Abstract:
The differences in the subunit compositions of gliadin and glutenin extracted from three kinds of enzyme-modified corn flours and untreated corn flour were compared by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and the molecular weights of the subunits were analyzed. Changes in the secondary structure of glutenin during enzymatic modification were determined by Fourier transform infrared (FT-IR) spectroscopy. The results showed that enzymatic modification had a relatively large influence on glutenin structure and a relatively small influence on gliadin. Treatment combining α-amylase and alkaline protease had a synergistic effect, promoting the hydrolysis of corn gluten, and a large number of low molecular weight subunits were produced. The structure of the corn glutenin modified by individual enzymes was more disordered than that of the untreated sample, but the combined enzyme treatment produced the highest percentage of α-helices and the structure tended to be stable. The above results showed that the change in the glutenin structure might be an important factor for the improvement of corn dough-forming properties. This study revealed some of the mechanisms underlying the enzymatic modification of corn flour, and provided a scientific basis for the modification of corn dough and product development.

37 Effect of Different Pretreatments on the Vacuum-freezing Characteristics of Apple Slices

WANG Hai-ou , CHEN Shou-jiang , FU Qing-quan , WANG Rong-rong , ZHANG Wei , CHEN Lu-lu , WU Jin-ying

2016, 32(11):241-247. DOI: 10.13982/j.mfst.1673-9078.2016.11.037

[Abstract](876) [HTML](0) [PDF 792.47 K](991)

Abstract:
The vacuum-freezing characteristics of apple slices were investigated after freeze-thaw, blanching, and ultrasound pretreatments versus no pretreatment (four groups). The characteristics studied included: rate of water loss, temperature, moisture state in tissues, and cell structure. The water loss rate among the four groups after 40 min of vacuum-freezing was 46.48%, 27.49%, 24.80%, and 22.92%, respectively. The results showed that water loss rate of the freeze-thaw group was significantly higher than that of the other three groups (p<0.05). The difference in water loss rate between the untreated and blanching groups was significant (p<0.05), whereas no significant difference was noted between untreated and ultrasound groups (p>0.05). The process of vacuum freezing apple slices is divided into three phases: depressurization flashing, ice forming, and deep freezing. The final freezing temperature of the freeze-thaw, blanching, and ultrasound and no pretreatment groups was -30.40 ℃, -27.42 ℃, -26.84 ℃, and -26.50 ℃, respectively. The transverse relaxation time peak T23 value of free water in low-field nuclear magnetic resonance (LF-NMR) of apple slices pretreated with freeze-thawing and blanching shifted significantly to the left, whereas the binding force on free water in tissues was enhanced. Freeze-thaw and blanching pretreatments caused greater damage to the structure and morphology of cells and tissues of apple slices compared with ultrasound and no pretreatment. The differences in the vacuum-freezing characteristics of the four groups were mainly due to the different extent of damage to the structures and tissues in apple slices caused by each pretreatment.

38 Thermal Properties of Four Kinds of Starch-fatty Acid Inclusion Complexes Prepared by Alkaline Method

QIN Fu-min , CHEN Hai-hua , WANG Yu-sheng , HU Zun-ying

2016, 32(11):248-254. DOI: 10.13982/j.mfst.1673-9078.2016.11.038

[Abstract](716) [HTML](0) [PDF 672.82 K](1153)

Abstract:
The effect of mung bean starch, cassava starch, sweet potato starch, and potato starch on the gelatinization properties, thermal decomposition properties, glass transition temperature (Tg), and crystal structure of starch-fatty acid inclusion complexes prepared by HCl/KOH method were studied by differential scanning calorimeter, thermogravimetric analyzer, and X-ray diffractometer. The results showed that the crystal form of the starches was transformed to V-type after complexation with fatty acids. The highest gelatinization temperature, Tg, and thermal decomposition stability were present in potato starch-stearic acid inclusion complexes, while those of cassava starch-stearic acid inclusion complexes were the lowest. Among the three kinds of root and tube starch-oleic acid inclusion complexes, the cassava starch-oleic acid inclusion complex had the highest gelatinization enthalpy (?H) and the lowest thermal decomposition stability, but the sweet potato starch-oleic acid inclusion complex had the lowest ?H and the highest thermal decomposition stability. The gelatinization temperature and thermal decomposition stability of potato starch-stearic acid inclusion complexes were higher than those of mung bean starch-stearic acid inclusion complexes, while the ?H and Tg of potato starch-oleic acid inclusion complexes were higher than those of mung bean starch-oleic acid inclusion complexes.

39 Changes of Non-volatile and Volatile Flavor Compounds in Braised Chicken Legs during the Reuse of Marinating Liquid

PENG Ting-ting , ZHANG Chun-jiang , HUANG Feng , ZHANG Liang , ZHANG Hong

2016, 32(11):255-266. DOI: 10.13982/j.mfst.1673-9078.2016.11.039

[Abstract](837) [HTML](0) [PDF 711.67 K](1084)

Abstract:
In order to explore the pattern of changes in flavor compounds from braised chicken legs during the reuse of marinating liquid, fresh chicken legs were braised in fresh marinating liquid and marinating liquids that had been reused between one and five times in this experiment, respectively, and a control group was cooked in distilled water. The changes in the levels of free amino acids (FAAs), nucleotides, and volatile flavor compounds were measured. With increasing number reuses of the marinating liquid, the content of FAAs showed an upward trend (p<0.05), and large fluctuations were observed in each stage. The nucleotide content also showed an upward trend (p<0.05), and inosine monophosphate (IMP) was the main tasty nucleotide in the braised chicken legs. Among the samples braised using the marinating liquids that were fresh or reused from one to five times and the control sample, 27, 29, 30, 32, 27, 25, and 15 types of volatile compounds were identified, respectively. The identified compounds were mainly produced from the thermal reaction of chicken flavor precursors and from volatile components of spices. With increasing number of marinating liquid reuses, the peak area of total ion current exhibited a downward trend after an initial increase. After the marinating liquid was reused four times, the mainly detected flavor compounds not only were of numerous types, but also had the largest peak area of total ion current. The highest sensory evaluation score was found after the marinating liquids were reused four and five times. These results provide a theoretical basis for the development and control of typical flavor compounds in the processing of braised chicken.

40 Isolation and Identification of Aroma-active Compounds and the Aroma Characteristic Analysis of Anhui Rice Wine

GAO Xian-li , ZHOU Cun-shan

2016, 32(11):267-273. DOI: 10.13982/j.mfst.1673-9078.2016.11.040

[Abstract](825) [HTML](0) [PDF 592.65 K](1038)

Abstract:
The aroma-active compounds in Anhui rice wine were isolated and identified using gas chromatography-mass spectrometry/gas chromatography-olfactometry (GC-MS/GC-O) coupled with quantitative descriptive analysis (QDA) in this paper, and the aroma characteristics of Anhui rice wine were also analyzed. Sixty-five volatiles, including eight acids, 12 alcohols, 16 esters, eight aldehydes/ketones, five furans, five phenols, three nitrogen-containing compounds, three sulfur-containing compounds, and five other compounds, were isolated and identified from Anhui rice wine. Using Guyue Longshan rice wine as a control, the types of volatiles isolated and identified in both Chinese rice wines showed high similarity (87%), but there were differences in the relative contents of most volatiles between Anhui rice wine and the control. Nineteen aroma-active compounds were identified in both Anhui rice wine and the control using GC-O, and contributed to the sour, alcohol, fruit, floral, pit, caramel-like, smoky, and herbal flavors. The results of QDA showed that Anhui rice wine was characterized by a harmonious aroma with prominent alcohol, wheat qu, and caramel-like flavors, while the control sample was characterized by a harmonious aroma with prominent alcohol, wheat qu, and fruit flavors. The aroma-active compounds in Anhui rice wine were identified using the above methods, and Anhui rice wine was found to possess unique aroma characteristics when compared with those of the control.

41 Safety Evaluation and Anti-anemia Effect of Hairtail Protein Ferrous-chelating Peptide in Mice

YUAN Ning , LIN Hui-min , DENG Shang-gui , JIN Tu-nan

2016, 32(11):274-279. DOI: 10.13982/j.mfst.1673-9078.2016.11.041

[Abstract](881) [HTML](0) [PDF 817.27 K](1019)

Abstract:
A rat model of iron deficiency anemia was established by feeding rats an iron-deficient diet, and the anti-anemia effect and safety of hairtail protein ferrous-chelating peptide were studied by feeding the animals with hairtail protein ferrous-chelating peptide through gavage, and these effects were evaluated using the acute toxicity test, Ames test, mouse bone marrow micronucleus test, sperm abnormality test and chromosome aberration test in mammalian cells in vitro. The results showed that hairtail protein ferrous-chelating peptide increased the hemoglobin (Hb) content and the number of red blood cells (RBC) and other peripheral parameters, and significantly improved the symptoms of anemia in rats. The median lethal dose (LD50) was 7454.80 mg/kg, indicating actual non-toxicity. TA97, TA98, TA100, and TA102, four standard strains in Ames test, were all negative in the Ames test of the mice. Meanwhile, compared with the negative control group, the results of the mouse bone marrow micronucleus test, sperm abnormality test, and chromosome aberration test in mammalian cells in vitro showed no significant difference, suggesting that the three results were also all negative. Therefore, we concluded that hairtail protein ferrous-chelating peptide has an anti-anemia effect and good food safety, and can be further developed and utilized as a food additive.

42 Prevalence of Staphylococcus aureus Contamination in Infant Foods and the Detection of Antibiotic Resistance Genes and New Enterotoxin Genes

ZHANG Yang , QIAO Ming-yu , WANG Xin

2016, 32(11):280-285. DOI: 10.13982/j.mfst.1673-9078.2016.11.042

[Abstract](790) [HTML](0) [PDF 471.61 K](1281)

Abstract:
The prevalence of S. aureus contamination in infant formula milk powder (PIF) and infant rice cereal (IRC) was investigated in this study, and the corresponding antibiotic resistance genes and novel enterotoxin genes were detected. A total of 692 PIF and IRC samples of different brands were collected in the Shaanxi province of China in 2010 and 2012 and screened for S. aureus. Polymerase chain reaction (PCR) was employed to detect 31 antibiotic resistance genes and nine novel enterotoxin genes among the isolates. The overall positive rate for S. aureus in 692 samples was 7.80%, including 8.17% among the samples collected in 2010 and 7.38% among the samples collected in 2012. Among the 75 isolated strains of S. aureus, 12 types of antibiotic resistance genes and two novel enterotoxin gene profiles were detected. The resistance gene with the highest detection rate was tetK (72.00%), followed by blaZ (36.00%), ermC (29.33%), tet(K)F (21.33%), linA/linA (12.00%), dfrG (8.00%), tetL (6.67%), and acc(6') (5.33%), and the genes with the lowest detection rate were ermB, msrA, msrB, and drfK (all at 1.33%). Among the novel enterotoxin genes, only sen (44.00%) and ser (4.00%) were detected. No significant difference was found in the contamination rate of S. aureus among the samples from different sampling years and production months and with different shelf lives. Additionally, the primary antibiotic resistance genes that these strains carried conferred resistance to penicillin, tetracycline, and macrolide, and the main virulence gene was sen.

43 Hazard Identification of Listeria monocytogenes Cross-contamination from Raw to Cooked Food Based on Food Safety Objective Values

DONG Qing-li , LU Ran-ran , WANG Wen , LIU Qing , JIANG Rong-hua

2016, 32(11):286-292. DOI: 10.13982/j.mfst.1673-9078.2016.11.043

[Abstract](740) [HTML](0) [PDF 617.83 K](1347)

Abstract:
To qualitatively analyze the cross-contamination of Listeria monocytogenes from raw to cooked food on cutting boards of different materials, wooden, plastic, and stainless steel cutting boards were selected for this study. Four common scenarios were set up, and the contamination levels (lgCFU/g) of L. monocytogenes in marinated pig tongue, cucumber, and on cutting boards under different scenarios were measured. At the same time, the modified first-order Baranyi model and second order main parameter model were used to simulate the growth of L. monocytogenes in cucumber. Additionally, the contamination level of the whole cross-contamination process was calculated according to food safety objective (FSO) theory; 2 lgCFU/g was set as the standard value for the FSO of L. monocytogenes in ready-to-eat (RTE) foods and was compared with 12 cross-contamination scenarios, i.e., four scenarios using three materials, and the corresponding risks were ranked. The results showed that the wooden cutting board scenario 1 (S1w), plastic cutting board scenario 1 (S1p) and stainless steel cutting board scenario 1 (S1s) showed the highest risk. Under scenarios 2, 3, and 4, the risk levels of wooden cutting boards were 2, 3, and 3, respectively, which were one risk level higher than those of the cutting boards of the other two materials. In conclusion, this study showed that cross-contamination was most likely caused by the use of the cutting boards without any cleaning treatment, and the risk from the wooden cutting board was higher than that of the cutting boards of the other two materials.

44 Identification of the Main Nitrogen-containing Compounds in Ctenopharyngodon Idellus by HPLC-Q-TOF-MS

ZHANG You-sheng , HUANG Jia-si , LIU Xue-ming , CHENG Jing-rong , CHEN Zhi-yi , ZHANG Ye-hui

2016, 32(11):293-302. DOI: 10.13982/j.mfst.1673-9078.2016.11.044

[Abstract](947) [HTML](0) [PDF 979.74 K](1733)

Abstract:
The main nitrogenous compounds in methanol extracts of Ctenopharyngodon idellus were analyzed and identified using high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (HPLC-Q-TOF-MS). Both positive and negative ionization modes were used to confirm the related chemical compounds and their characteristic fragment ions according to the accurate molecular mass information of the excimer ion peaks and the fragment ions. Using the ChemSpider database, 33 nitrogenous compounds in Ctenopharyngodon idellus were ultimately determined, and the data for the main fragments of each component were analyzed. These 33 nitrogenous compounds included 11 amino acids (eight types of α-amino acids), 12 amines, eight amide compounds, and two heterocyclic nitrogenous compounds. The results showed that the structures of monomer compounds in fresh aquatic products and raw materials could be elucidated directly using the HPLC-Q-TOF-MS technique and fragmentation analysis by mass spectrometry, which can improve the efficiency of analysis and identification of chemical components in fresh raw material. This study shows that these techniques are conducive for the identification and analysis of active components and newly generated compounds during the storage of fresh raw materials.

45 Application of Band Optimization of Near-infrared Spectra for Quantitative Detection of Proteins in Northeastern Pine Nuts

QIU Xun-chao , CAO Jun

2016, 32(11):303-309. DOI: 10.13982/j.mfst.1673-9078.2016.11.045

[Abstract](848) [HTML](0) [PDF 2.26 M](1139)

Abstract:
Near-infrared (NIR) spectroscopy was performed to develop a fast, nondestructive, and simple method to test the quality of Northeastern pine nuts. Using shelled and deshelled pine nuts, quantitative analysis models of proteins in the nuts were established using partial least squares (PLS) and the models were optimized by derivation, multiplicative scatter correction (MSC), standard normal variate (SNV), and vector normalization pretreatment. Backward interval partial least squares (BiPLS) and elimination of uninformative variables (UVE) were used to select characteristic bands to establish PLS protein prediction models with full wavelength and characteristic bands. The results showed that the models established after preprocessing with vector normalization and SNV exhibited optimal performance for deshelled and shelled pine nuts, respectively. The models were optimized by band selection and the optimum screening result was presented using BiPLS. The correlation coefficients (RC) of calibration subset of the protein models for deshelled and shelled pine nuts were 0.9056 and 0.9383, respectively. The root-mean-square error (RMSE) values of the validation subset were 0.6670 and 0.5761, respectively. Therefore, after optimization, the model prediction performance was improved, thus providing a reference point for online testing of proteins in deshelled and shelled pine nuts.

46 Identification of Phenolic Components in the Root and Leaf of Purple Yam (Dioscorea alata) by UHPLC-DAD-ESI-MS/MS

ZHOU Li , SHI Xin-min , REN Xiang-mei , ZHANG Jin-peng , QIN Zhi-hong

2016, 32(11):310-315. DOI: 10.13982/j.mfst.1673-9078.2016.11.046

[Abstract](1289) [HTML](0) [PDF 824.64 K](1505)

Abstract:
Total polyphenols were obtained from the freeze-dried root and leaf of Dioscorea alata by microwave-assisted extraction using 80% methanol as the extraction solvent. The extract was analyzed by ultra-high-performance liquid chromatography with diode array detector coupled with electrospray ionization-tandem mass spectrometry (UHPLC-DAD-ESI-MS/MS) in the positive/negative ion mode. Based on the retention time, ultraviolet absorption, relative molecular weight, and MS2 fragmentation pattern in LC-MS chromatography, the main phenols in the root and leaf of Dioscorea alata were phenolic acids, anthocyanins, and flavonoids. Twenty-nine phenolic compounds were identified in the purple yam, and 5-O-caffeoylquinic acid, feruloylquinic acid (tR: 12.289), rosmarinic acid, rutin, and quercetin were the common components in both root and leaf. Eleven further phenolic compounds were identified from the root of purple yam, including sinapic acid, sinapic acid-glucosides, syringic acid derivatives, coumaric acid derivatives, ferulic acid derivatives, sinapic acid-diglucoside, and anthocyanins. Furthermore,13 phenolic compounds were found in the leaf of purple yam, including caffeic acid, caffeoylquinic acid methyl ester, caffeoyl shikimic acid, p-coumaroylquinic acid, coumaroylquinic acid methyl ester, kaempferol -3-O-rutinoside, and rosmarinic acid methyl ester.

47 Determination of the Addition Amount of Oat Flour to Wheat Flour Based on Gas Chromatography

WANG Chao-qun , ZHANG Hui , QIAN Hai-feng , WANG Li , QI Xi-guang

2016, 32(11):316-322. DOI: 10.13982/j.mfst.1673-9078.2016.11.047

[Abstract](838) [HTML](0) [PDF 610.29 K](1065)

Abstract:
The fatty acid composition of 48 varieties of oat flour, 40 varieties of wheat flour, and 105 oat-wheat composite flours obtained using a balanced incomplete randomized block design were acquired using the gas chromatography technique. The contents of palm acid, oleic acid, and linoleic acid, and the ratios and correlations of oleic acid/linoleic acid, palm acid/oleic acid, and palm acid/linoleic acid of the samples were analyzed. The similarity of fatty acid composition in oat and wheat flours was used to determine the indexes for quantitative analysis of the amount of oat flour added to wheat flour, and the difference in the fatty acid content was used to reflect the variation trend of fatty acid content in composite flour with different ratios of added oat flour. Based on these results, a three-dimensional map for discriminant analysis and Fisher linear discriminant functions were established to clearly present the distribution features of fatty acids in the composite flour, and then the amount of oat flour added to wheat flour was quantitatively determined. Based on the analysis of the similarities and differences in the fatty acid composition and content of oat and wheat flour, this study provides an important reference method with a wide application, high sensitivity, and strong feasibility for the safety surveillance and quality control of oat products.

48 Determination of Stable Carbon and Hydrogen Isotope Ratios of Commercial Vegetable Oils

WU Yu-luan , DONG Hao , WANG Chao , WANG Li , WANG Bin , GUO Xin-dong , XIAN Yan-ping

2016, 32(11):323-327. DOI: 10.13982/j.mfst.1673-9078.2016.11.048

[Abstract](875) [HTML](0) [PDF 521.26 K](1155)

Abstract:
A method using element analyzer-isotope ratio mass spectrometry (EA-IRMS) was established to analyze the stable hydrogen and carbon isotope ratios (δ2H and δ13C, respectively) of 13 corn oil, 20 soybean oil, 20 peanut oil, and 15 blend oil samples. The results showed that δ13C values of corn oil, soybean oil, and peanut oil samples were -30.475‰ to -14.15‰, -30.11‰ to -25.103‰, and -29.775‰ to -24.44‰, respectively. The δ13C values were significantly different among samples of the three kinds of vegetable oils (p<0.01). After eliminating possible adulterated samples, the δ2H values of the corn oil, soybean oil, and peanut oil samples were -277.431‰ to -261.493‰, -262.658‰ to -232.687‰, and -290.164‰ to -231.233‰, respectively. The δ13C values of the corn oil, soybean oil, and peanut oil samples were -16.606‰ to -14.15‰, -25.98‰ to -25.103‰, and -29.775‰ to -26.032‰, respectively. Significant differences were observed in the δ2H and δ13C values among samples of the three kinds of vegetable oils (p<0.01). In addition, blend oil displayed a wide distribution of δ2H values ranging between -260.033‰ and -220.234‰. Comparison of the two-dimensional distribution of carbon and hydrogen isotope ratios of blend oil with those of the other three kinds of vegetable oils can contribute towards comprehensively evaluating and identifying adulterated commercial vegetable oil samples and can provide a foundation for research and technical support for determining adulteration in commercial vegetable oils.

49 An Electronic Nose-based Method for Determination of the Storage Time of Huangshan Maofeng Tea

XUE Da-wei , YANG Chun-lan , KONG Hui-fang , BAO Jun-hong

2016, 32(11):328-333. DOI: 10.13982/j.mfst.1673-9078.2016.11.049

[Abstract](851) [HTML](0) [PDF 652.60 K](1194)

Abstract:
Five grades of Huangshan Maofeng tea samples with six different storage times were analyzed by using an electronic nose. First, the original feature vectors representing the tea odor were acquired, and the first five principal components were extracted as the principal feature vectors. The principal feature vectors were used as the input of back propagation neural network (BPNN) to establish the prediction model for the storage time of Huangshan Maofeng tea (called PCA-BPNN). The test was carried out on 75 tea samples (15 samples of every grade). The results showed that for the tea at zero day of storage, the maximum prediction error was seven days and the prediction error of five samples exceeded ten days (6.67%). For the tea of 60 d of storage, the maximum prediction error was ten days, and the prediction error of four samples exceeded ten days (5.33%). For the tea of 120 d of storage, the maximum prediction error was 16 d and the prediction error of seven samples exceeded ten days (9.33%). For the tea of 180 d of storage, the maximum prediction error was 19 d and the prediction error of eight samples exceeded ten days (10.67%). For the tea of 240 d of storage, the maximum prediction error was 21 d and the prediction error of eight samples exceeded ten days (10.67%). For the tea of 300 d of storage, the maximum prediction error was 14 d and the prediction error of six samples exceeded ten days (8.00%). The feasibility of PCA-BPNN prediction model to determine the storage time of Huangshan Maofeng tea was verified. Moreover, the performance of PCA-BPNN prediction model was better than that of BPNN prediction model using the original feature vectors as the input.

50 Separation and Identification of Potential Microbial Contaminants in Traditional Vinegar

ZHENG Yu , NIU Ji-wei , ZHANG Xiang-long , SONG Jia , XIA Ting , WANG Min

2016, 32(11):334-339. DOI: 10.13982/j.mfst.1673-9078.2016.11.050

[Abstract](1241) [HTML](0) [PDF 1.05 M](2011)

Abstract:
Chinese traditional vinegars are produced in open fermentation conditions involving various types of microorganisms, and improper control in the production process can lead to microbial contamination of the products. In this study, the differences in physicochemical properties and viable bacterial count between normal vinegar (NV) samples and abnormal vinegar (ANV) samples were compared. Additionally, the gas composition in ANV samples was analyzed, and the potential microbial contaminants were separated and identified. The results showed that in ANV samples the viable bacterial count exceeded the limit, the reducing sugar and total sugar contents decreased, and the lactic acid content increased. The main gas that resulted in the expansion of plastic bottles was CO2, whose concentration was more than 0.005 in the headspace of the ANV samples. Thirty strains were separated from the ANV samples, and 16 of them were identified as heat-resistant, gas-producing, or preservative-resistant strains that belonged to the genera Bacillus, Pseudomonas, Stenotrophomonas, Serratia, Clostridium, Aneurinibacillus, Brevibacillus, Sphingobacterium, and Delftia. Among them, strains PMB-9 and PMB-16 could produce white flocs that allowed the fermented liquid to become ropy, and these were the main potential microbial contaminants causing the ropy vinegar. Strains PMB-3, PMB-4, PMB-7, PMB-8, and PMB-14 could grow and produce gases in the vinegar, and were the main potential microbial contaminants causing the gas expansion.

Home

About the journal

Notes for submission

Acceptable topics

Author garden

Open access

中文

Volume 32,Issue 11,2016 Table of Contents