Volume 30,Issue 8,2014 Table of Contents

1 Immunological Effects of Schizophyllum commune Polysaccharides in Mice

YANG Na , WANG Hong-fei , DONG Shuan-quan , XU Feng , SHAO Xing-feng , LI He-sheng

2014, 30(8):1-5.

[Abstract](1712) [HTML](0) [PDF 429.51 K](711)

Abstract:
In this study, polysaccharide from Schizophyllum commune was obtained by ultrasound-assisted water extraction and an immunocompromised mouse model was established by intraperitoneal injection of cyclophosphamide. Immunological effects of different doses of S. commune polysaccharides administered to mice intragastrically were investigated in terms of non-specific immunity, cell-mediated immunity, and humoral immunity. The inhibitory effects of S. commune polysaccharides on the in vitro proliferation of mouse macrophages and colon carcinoma were evaluated by MTT assay. The results showed that S. commune polysaccharides had a certain recovery effect on the thymus and spleen as well as caused sensitization in mice injected with sheep red blood cells in their footpads, leading to swelling. In mice injected with different doses of S. commune polysaccharides, serum levels of hemolysin, IgG, IgA, and IL-2 increased to varying degrees as compared to the immunocompromised mice group. In addition, S. commune polysaccharides could increase phagocytosis by murine macrophages and at 2000 μg/mL concentration, showed up to 45.32% inhibition of colon carcinoma cells.

2 Inhibitory Effect of Prunella vulgaris L. Flavonoids on Osteoporosis in Ovariectomized Rats

LIU Hua , ZHONG Ye-jun , WU Dan

2014, 30(8):6-11.

[Abstract](1443) [HTML](0) [PDF 487.24 K](735)

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In this study, the effect of flavonoids from Prunella vulgaris L. on bone mass, biomechanical properties, and bone metabolism of ovariectomized, osteoporotic rat model was investigated. After treatment with flavonoids extracted from P. vulgaris L., rat serum samples were collected to examine changes in the levels of blood minerals, osteoprotegerin (OPG), and alkaline phosphatase (ALP). The femur bone was also collected from rats in each group to measure bone mineral density (BMD) and bone tissue morphology. A fluorescent quantitative polymerase chain reaction approach was used to determine the expression levels of collagen type I, integrin β1, and focal adhesion kinase mRNA. The results showed that the level of ALP (3.03 ± 0.22 IU/L), number of osteoclasts (0.23 ± 0.05 1/mm2), and bone resorption perimeter percentage (14.94% ± 5.12%) were lower in the flavonoids group than in the control group (p < 0.05). In contrast, the levels of OPG (186.34 ± 44.21 pg/mL), BMD, and the relative volume (26.11% ± 5.32%) and thickness (587.16 ± 165.01 μm) of trabecular bone were higher (p < 0.05) in the flavonoids group than in the control group. The results indicated that Prunella vulgaris L. flavonoids enhanced osteoblast function, decreased bone resorption and bone metabolism, increased bone formation, reduced trabecular bone loss, and inhibited the reduction in bone mass and bone strength, thus enhancing BMD and ultimately suppressing osteoporosis in ovariectomized rats.

3 Mechanism of Weight Loss with Resistant Starch from Banana in Diet-induced Obese Rats

TANG Jian , XIA Yu , DU Bing , ZHANG Jia-yi , YANG Gong-ming

2014, 30(8):12-18.

[Abstract](1724) [HTML](0) [PDF 530.55 K](789)

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In this study, the anti-obesity effect of green bananas, rich in resistant starch, on diet-induced obese rats was evaluated and the mechanism of weight loss was studied. The results showed that, compared with rats in the obese control group, the body weight of rats in the medium- and high-dose (of banana resistant starch) groups reduced significantly (P < 0.05) by 7.26% and 7.99%, respectively. Rats in all three groups showed improved biochemical profiles, including blood glucose, serum leptin, total cholesterol, triglycerides, low-density lipoprotein, and high-density lipoprotein levels, and a dose-dependent increase in fecal fat excretion, indicating that resistant starch from banana displayed good anti-obesity effect. Compared with the obese control group, low, medium, and high doses of resistant starch from banana reduced food intake of rats by 16.63%, 19.61%, and 23.86%, respectively. Three kinds of gastrointestinal hormones related to appetite control were investigated to explore the mechanism of weight loss. Medium and high doses of resistant starch from banana significantly increased serum cholecystokinin (CCK) levels (P < 0.05) by 24.36% and 24.97%, respectively. The serum CCK level also increased in the low-dose group, with no statistically significant differences. Serum peptide YY (PYY) level in the low-, medium-, and high-dose groups increased significantly (P < 0.01), by 22.35%, 28.34%, and 34.84%, respectively. However, no effects were observed on ghrelin. Therefore, the mechanism of weight loss by resistant starch from banana involved in stimulating the secretion of gastrointestinal hormones that affected appetite, controlling food intake of rats, and prolonging gastric emptying.

4 Effect of Pretreatment of Defatted Soybean Meal on Functional Properties of β-conglycinin

WU Wei , CAI Yong-jian , LIANG Ying , LIN Qin-lu , DENG Ke-quan , HUA Yu-fei

2014, 30(8):25-30.

[Abstract](1523) [HTML](0) [PDF 581.63 K](876)

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Soybean β-conglycinin was prepared from fresh defatted soybean meal, dry-heat treated defatted soybean meal and solvent extraction of defatted soybean meal. The effects of pretreatment on residual lipid content, lipoxygenase activity of defatted soybean meal and the functional properties of prepared soybean β-conglycinin were investigated. Dry-heat treatment did not result in significant changes in residual lipid content; however, lipoxygenase activity decreased by 7.69%. Solvent extraction treatment led to a significant decrease in the residual lipid content and lipoxygenase activity by 98.08% and 96.12%, respectively, indicating that solvent extraction could significantly inhibit lipid peroxidation of defatted soybean meal. Dry-heat treatment also caused a decrease in solubility, water-holding capacity, oil-holding capacity, emulsifying properties, foaming properties, and gelling properties of the prepared soybean β-conglycinin. These functional properties of soybean β-conglycinin showed an improvement when defatted soybean meal was treated with solvent extraction. These results provide a preliminary basis to improve the functional properties of soybean protein.

5 Stimulation of Glucose Consumption in 3T3-L1 Adipocytes by Triterpenoids from Cyclocarya paliurus Leaves

FU Xiao , YIN Zhong-ping , SHANGGUAN Xin-chen , PENG Da-yong , CHEN Ji-guang , JIANG Yan

2014, 30(8):31-37.

[Abstract](1278) [HTML](0) [PDF 363.36 K](733)

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Cyclocarya paliurus is a unique plant native to China, tea made from the leaves of this plant known for its hypoglycaemic effects. To further explore its hypoglycaemic property, total triterpenoids from Cyclocarya paliurus leaves (CPTT) were extracted by an ultrasound-assisted method and successively purified by extraction, macroporous resin adsorption, and decolorization. The total triterpenoid content of CPTT was as high as 86.3%. The content of ursolic acid, oleanolic acid, maslinic acid, corosolic acid, and betulinic acid in CPTT were 19.35%, 17.38%, 7.53%, 4.59%, and 1.42%, respectively. No obvious change in glucose consumption was observed when 3T3-L1 pre-adipocytes were treated with CPTT in the basal condition, but the consumption significantly increased after simultaneous stimulation with 10 nM insulin. For mature adipocytes, CPTT increased glucose consumption significantly in both basal and insulin-stimulated conditions. For dexamethasone-induced insulin-resistant 3T3-L1 adipocytes, CPTT effectively improved insulin sensitivity and enhanced glucose consumption in a dose-dependent manner, with the optimal effect observed at 25 μg/mL. These results suggest that triterpenoids from Cyclocarya paliurus leaves can effectively increase glucose consumption in adipocytes and therefore have a potential application in both the food and pharmaceutical industries.

6 Isolation and Identiﬁcation of Flavor Peptides in Cultured Puffer Fish (Takifugu obscurus)

LIU Yuan , QIU Chun-yang , WANG Xi-chang , MIAO Xiao-dan , ZHANG Jing-jing , XIONG Zheng-hai

2014, 30(8):38-42.

[Abstract](1506) [HTML](0) [PDF 554.21 K](770)

Abstract:
The aim of this study was to isolate and study the structural properties of flavor peptides from raw, cultured puffer fish muscle. Three fractions (0-F1, 0-F2, and 0-F3) were obtained from an aqueous extraction of cultured puffer fish (Takifugu obscurus) muscle by Sephadex G-15 gel filtration chromatography. Using sensory evaluation analysis and an electronic tongue, it was found that fraction 0-F1 could elicit umami and kokumi tastes. Further isolation of fraction 0-F1 components was performed using reverse-phase high-performance liquid chromatography (RP-HPLC) to yield two subfractions 0-F1-1 and 0-F1-2. The electronic tongue showed that subfraction 0-F1-1 could elicit a relatively strong umami taste. The amino acid sequence of subfraction 0-F1-1 isolated by RP-HPLC was identified using matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and the structure of this new flavor peptide was Pro-A-Ala-B Met*-Cys-Arg (810.9046 Da, where A and B are amino acid codes; Met* is oxidative methionine). Although this peptide contained a large number of hydrophobic amino acids, it did not have a bitter taste, and rather a thick and strong taste. Hydrophilic amino acid residue Cys might be the key factor contributing to the kokumi taste of this peptide.

7 1H Nuclear Magnetic Resonance (NMR) Fingerprints and Low-Field- NMR Relaxation Properties of Sunflower Oil during Thermal Oxidation

LU Hai-yan , WANG Xin , ZHAO Ting-ting , LIU Bao-lin

2014, 30(8):43-50.

[Abstract](1223) [HTML](0) [PDF 664.81 K](731)

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1H nuclear magnetic resonance (1H-NMR) was used to study change patterns associated with relative content of oxidation products (conjugated olefins, aldehydes, oxides, aromatic hydrocarbons, and free fatty acids) produced by the process of thermal oxidation during storage of sunflower oil at 65 ℃. Correlation analysis with S21 changes in low-field (LF)-NMR relaxation was conducted. The 1H-NMR results indicated that the amount of primary oxidation products increased initially and then decreased with time, where hydroperoxide- conjugated dienes were preferentially degraded as compared to hydrogen peroxides. The amount of secondary oxidation products and hydrolysates such as aldehydes, epoxides, and free fatty acids increased exponentially with time (R2 > 0.96), whereas the amount of aromatic hydrocarbons also increased and then decreased with time. The LF-NMR peak area S21 for the oil sample increased exponentially (R2 = 0.99) with time. Correlation analysis showed that oxides and free fatty acids had the highest correlation with S21, which was proved reasonable and reliable by model validation. The results could provide a foundation to further explore the characteristic peak S21 such that the quality of edible oil could be improved using the LF-NMR results as reference.

8 Identification and Antiproliferative Activity of Polysaccharides from Tricholoma matsutake (mushroom)

YOU Li-jun , FENG Meng-ying , GAO Qing , ZHAO Rong-zhong , FU Xiong , LIU Dong , ZHAO Mou-ming

2014, 30(8):51-58.

[Abstract](1506) [HTML](0) [PDF 451.15 K](749)

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Tricholoma matsutake,also known as “the king of mushrooms,” contains polysaccharides that had been reported to have anti-cancer, anti-radiation, and immune-enhancing effects. In this study, polysaccharides from Tricholoma matsutake (TM-P) were isolated and purified using a diethylaminoethyl (DEAE) Sepharose fast-flow column and a Sephadex G-75 column, which resulted in four purified fractions: TM-P1A, TM-P1B, TM-P2A, and TM-P2B. Structural characterization of these polysaccharide fractions was performed using gas chromatography-mass spectrometry (GC-MS), high-performance gel permeation chromatography (HP-GPC), and nuclear magnetic resonance (NMR) spectra. The results showed that the main components of TM-P1A and TM-P2B were glucose and galactose with a small amount of mannose in molar ratios of 8.7:1.8:1.0 and 8.9:1.3:1.0, respectively. TM-P2A was composed of glucose, galactose, mannose, and fucose, with a molar ratio of 17.7:7.9:3.9:1.0. The main component of TM-P2B was β-1,6-glucopyranose (unbranched) with a small amount of β-1,6-galactopyranose and β-1,6-mannopyranose. Among all fractions, TM-P2B showed the strongest antioxidant and antiproliferative activities. The oxygen radical absorbance capacity of TM-P2B was 2475.33±15.32μmolTrolox/g. At a concentration of 1.0mg/mL, TM-P2B showed 90.23% ± 2.17% inhibition of HepG2 human hepatoma cells, which was 1.2 and 3.1 times that observed with TM-P2A and TM-P1A, respectively. This study provides important information for further application and development of Tricholoma matsutakeand related products.

9 Impact of Region of Interest Selection for Hyperspectral Imaging and Modeling of Sugar Content in Apple

GUO Zhi-ming , HUANG Wen-qian , PENG Yan-kun , WANG Xiu , LI Jiang-bo

2014, 30(8):59-63.

[Abstract](1871) [HTML](0) [PDF 540.54 K](787)

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Hyperspectral imaging is an effective imaging technique that has been applied to quality and safety inspection of food and agricultural products. However, the selected shape and size of the region of interest (ROI) in hyperspectral imaging directly affects the accuracy and stability of the measurement. In this study, a hyperspectral imaging system was developed for wavelengths spanning from 330 to 1100 nm to acquire hyperspectral images of apple samples. Mean reflectance spectra of round and square ROIs with different sizes were extracted. After the spectral pretreatment to eliminate the impacts of noise and irrelevant information, models for quantitative analysis of the sugar content in apple were developed using partial least squares method. The models were externally verified with the prediction set consisting of independent samples, in order to analyze the impact of the shape and size of ROIs on the accuracy of hyperspectral imaging system modeling. The results showed that the model of sugar content in apple, constructed using a round ROI with 150 pixels diameter, yielded the highest accuracy and predictive capability. The correlation coefficient of calibration set (Rc) was 0.9305, the root mean square error of calibration (RMSEC) was 0.4331, the correlation coefficient of prediction set (Rp) was 0.9232, and the root mean square error of prediction (RMSEP) was 0.4568. These results demonstrate that selecting an ROI with an appropriate shape and size is important to improve the accuracy of modeling and harness the full potential of the hyperspectral imaging technique.

10 Analysis of CRISPR Regions in Food-borne Listeria monocytogenes

DI Hui-ling , YAN He , SHI Lei

2014, 30(8):64-69.

[Abstract](1165) [HTML](0) [PDF 781.42 K](722)

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In order to find out CRISPRs in 18 lineage I (serotype1/2b, 4b) strains of food-borne Listeria monocytogens isolated from 2177 retail food samples in Hebei province, the CRISPR sequences were obtained by PCR amplification, and homology analysis was predicted using bioinformatic methods, then cluster typed by using a CRISPR-based approach. We detected three CRISPR loci in all studied strains. Loucus1 was most popular (13/18); locus2 and locus3, as two activity loci , were only detected at least one in 5 serotype 1/2b strains. Locus1, a putative remnant of a functional CRISPR ancestor, was beared unconserved repeats (DR1) and a few of spacers; locus2 and locus3, relative new functional structures, were beared conserved repeats (DR2, DR3) and fast growing number of spacers. In all, 2 strains containerd all three loci, 3 strains contained the first 2 of the three loci, as well as 8 strains only contained the first one locus, and 5 strains did not find any CRISPR structure. As the diversity of CRISPR arrays, 18 strains typed to 5 clusters (A~F), and 4 subset clusters (A1and A2, B1 and B2). CRISPR typing can be good used in differentiating serotype 1/2b strains. In other hands, the CRISPR structures, especially that beared more spacers, enhance the host's environmental adaptability, enlarged the clear difficulty in food processing, alarm the food safety. The government should reinforce the control of these kinds of L. monocytogenes.

11 In Vitro Antioxidant Activity and Resistance to Ultraviolet Radiation of Polyphenol from Watermelon Rind

LIU Zhong-yi , TAN Cao , LIU Wen-ping , PENG Li , BAO Hao , LUO Cai-lian

2014, 30(8):70-75.

[Abstract](1322) [HTML](0) [PDF 659.57 K](899)

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Polyphenols were extracted from watermelon rind using an ultrasound-assisted process. Antioxidant activity of the crude extract was assessed by determining its hydroxyl radical-scavenging activity, 2,2-diphenyl-2-picrylhydrazyl (DPPH)-scavenging activity, ferric-reducing ability of plasma (FRAP) assay, whereas resistance to ultraviolet (UV) radiation was studied using solid Escherichia coli medium. Composition of the polyphenol extract was determined by high-performance liquid chromatography. The results showed that the crude polyphenol extract from watermelon rind exhibited in vitro antioxidant activity and resistance to UV radiation. Additionally, its hydroxyl radical-scavenging activity was weaker than that of Vc, and its DPPH-scavenging activity was equivalent to that of butylated hydroxytoluene (BHT); however, its ferric-reducing activity was significantly stronger than the activity of BHT. When exposed to the same intensity of UV radiation that caused 90% mortality in E. coli, a visibly higher number of surviving E. coli colonies treated with the crude polyphenol extract from watermelon rind was observed than that observed in the control (saline-treated) group. The antioxidant activity and resistance to ultraviolet radiation correlated linearly with the concentration of polyphenol extracted from watermelon rind. The main component of the extract was gallic acid.

12 Screening of High-yield Fibrinolytic Enzyme-producing Strains from Traditional Fermented Douchi (Honghe, Yunnan) and Analysis of the Gene Encoding the Fibrinolytic Enzyme

GONG Fu-ming , LI Xiao-ran , SONG Yuan-liang , LUO Yi-yong , ZHANG Zhong-hua , LIU Chen-jian

2014, 30(8):76-81.

[Abstract](1324) [HTML](0) [PDF 615.80 K](830)

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High-yield fibrinolytic enzyme-producing bacterial strains were isolated and screened from traditionally fermented douchi from Honghe, by a two-step screening method, in which skim milk agar and fibrin agar were used. The bacterial gene encoding the fibrinolytic enzyme was cloned and analyzed to provide bacterial reference strains and a theoretical basis to develop a new version of functional douchi. Using these methods, a high-yield fibrinolytic enzyme-producing strain Bacillus subtilis LC-2-1 was successfully isolated, which secreted a kind of douchi fibrinolytic enzyme. The molecular mass of the enzyme was 27.4 kDa that contained 275 amino acids encoded by 825-bp. Compared to other douchi fibrinolytic enzymes and nattokinase, the enzyme produced by B. subtilis LC-2-1 showed significant differences, and the amino acid sequence homology was 85.1%. Additionally, the enzyme had high fibrinolytic activity, which was up to 79.84 U/mL. Thus, these results could provide a bacterial reference strain and theoretical basis to develop a new version of fermented douchi with thrombolytic activity.

13 The Research of Apoptotic in Yak Muscles during Postmortem Aging

SUN Zhi-chang , YU Qun-li , HAN Ling , ZHANG Wen-hua , YANG Qin

2014, 30(8):82-88.

[Abstract](1446) [HTML](0) [PDF 545.03 K](772)

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Twenty-four Gannan yak were slaughtered according to Islamic way of slaughtering, then aged at 0~4 ℃ with wind speed of 0.5 m/s . The shear force, MFI, color, apoptotic rate and caspase-3 activity during postmortem aging were determined. The shear force value in triceps brachi (TB), musculus longissimus (ML) and semimembranosus (SM) after slaughtered of 1~5 d was significantly lower (p <0.05), and MFI significantly increased (p <0.01); L *, a *, b * values were significantly higher at the 3rd d of postmortem aging, a *, b * values decreased significantly at 5~7th d of postmortem aging (p <0.01); the cooking loss first increased and then decreased at 1~7th d of postmortem aging; the apoptosis rate in TB and SM had very significant increase in process (p <0.01), the positive nuclei number in TB and ML had difference during postmortem aging (p <0.01); it was detected caspase-3 activity in TB, ML and SM at 0.5 h postmortem, while it was reached the highest in ML at 12 h postmortem. Across correlation analysis, the yak skeletal muscle cell apoptosis and its degree of deepening were related to the changes of tenderness, meat color (L *, a *, b *) and water holding capacity, as well as the yak meat quality change.

14 Study of Structural Changes in Whey Protein Isolate-Dextran Conjugate Using Fourier Transform Infrared Spectroscopy

LU Jing-jing , SUN Wei-wei

2014, 30(8):89-93.

[Abstract](1459) [HTML](0) [PDF 510.91 K](1068)

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Measurement of A294, the degree of browning, and the content of free amino groups showed that a grafting reaction based on the Maillard-type reaction had occurred between the whey protein isolate (WPI) and dextran under dry-heating treatment. The effect of this grafting reaction on the structure of WPI was investigated by using Fourier transform infrared spectroscopy (FT-IR). Compared to the original WPI, the conjugate showed a broad peak in the range of 3700~3200 cm-1 and an increase in absorption between 1260 and 1000 cm-1. The peak shapes of amide I and amide II bands showed remarkable changes, the peak intensity increased, and the red shift phenomenon occurred in the corresponding absorption peaks. Using deconvolution and second derivative methods, the curve of amide I band was fitted for quantitative analysis of the secondary structural changes in WPI before and after the grafting reaction. The results showed that the secondary structure of WPI had been destroyed owing to the introduction of macromolecule dextran. The number of β-turns and random coils increased, whereas the number of α-helix and β-sheet decreased after the graft reaction, indicating that the structure of WPI had become relatively unordered.

15 Effect of Conjugated Linoleic Acid on Physical Properties of Corn Starch

WANG Hui-yun , WANG Wen-jing , CHEN Hai-hua , WANG Yu-sheng

2014, 30(8):94-99.

[Abstract](1163) [HTML](0) [PDF 504.64 K](764)

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Effect of conjugated linoleic acid on the pasting properties, thermal properties and rheological properties of corn starches with different amylose content were studied by Rapid Viscosity Analyser, Differential Scanning Calorimetry and Dynamic Rheometer. The results showed that with the equal addition of conjugated linoleic acid, the peak viscosity and some other viscosity value of common corn starch was increased. Gelatinization enthalpy of common starch was enhanced and reached the highest with addition of 1% conjugated linoleic acid. With 2% conjugated linoleic acid, gelatinization enthalpy of high-amylose corn starch and waxy corn starch was decreased. Further more, the gelatinization enthalpy of waxy corn starch was decreased significantly. In addition, short-term and long-term retrogradation of high-amylose corn starch was significantly inhibited and the aging rate was decreased from 0.45, 0.63 to 0.31, 0.55 respectively. With the addition of conjugated linoleic acid, apparent viscosity and consistency coefficient of three corn starches were increased. Storage modulus and loss modulus of common corn and high-amylose corn starch were increased, while tanδ was decresed for the addition of conjugated linoleic acid. Therefore, common corn and high-amylose corn starch could form elastic gels.

16 Isolation, Identification, and Fermentation Properties of Lactic acid bacteria from Air Dried and Fermented Megalobrama amblycephala

ZHAO Jun-ren , CHENG Shui-ming , HONG Wei-di , WANG Ru-lan , LI Chun-hai

2014, 30(8):100-105.

[Abstract](1504) [HTML](0) [PDF 542.39 K](798)

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The aim of this study is to obtain lactic acid starters with excellent fermentation properties from air-dried and fermented Megalobrama amblycephala, a fermented fish product unique to China. The fermentation capacity of lactic acid bacteria was isolated, identified, and evaluated from the fermented fish. Strains were isolated by dilution plate method and identified by colony characteristics, bacterial morphology, carbohydrate fermentation, and a series of physiological and biochemical tests. The results showed that the isolated strains belonged to the following seven species: Tetragenococcus halophilus, Lactobacillus curvatus, Lactococcus lactis subsp. lactis, Leuconostoc gelidum, Lactobacillus gasseri, Lactobacillus jensenii, and Lactobacillus amylophilus. Fermentation capacity was evaluated in terms of acidification rate, salt tolerance, nitrite tolerance, growth temperatures, and proteolytic and lipolytic capacities. The final optimization results showed that Lactococcus lactis subsp. lactis qualified as an excellent lactic acid starter.

17 Effect of Different Storage Temperatures on the Quality and Ultrastructure of Pampus argenteus

SU Hui , XIE Jing , LI Liu , WU Sheng-bin , XU Cheng-hua

2014, 30(8):106-111.

[Abstract](1304) [HTML](0) [PDF 551.62 K](916)

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To explore the shelf life of Pampus argenteus under different storage temperatures, the aerobic plate count (APC), pH, total volatile basic nitrogen (TVB-N) content, K values, actomyosin content, total sulfhydryl content, and ultrastucture of Pampus argenteus were measured under conditions of cold storage, partial freezing storage, and frozen storage. The results showed an increase in APCs, pH, TVB-N, and K values with time, under all three storage conditions. The TVB-N content of Pampus argenteus reached values of 0.35 mgN/g, 0.40 mgN/g, 0.16 mgN/g, respectively, after storage for 6 d, 20 d, and 60 d in the frozen state. This observation suggested that frozen storage conditions could effectively retard spoilage of Pampus argenteus. The amount of dissolved actomyosin and total sulfhydryl content decreased with storage time for all three storage conditions. The formation of ice crystals within muscle fibers showed different trends with different storage temperatures. After 20 d of storage under frozen conditions, the muscle fibers of Pampus argenteus were severely damaged, likely because of the formation of ice crystals with large muscle fiber displacement and deformation. In contrast, only partial muscle fiber displacement occurred with partial freezing storage, suggesting that partial freezing conditions could better maintain Pampus argenteus muscle fiber morphology.

18 Antioxidant Activity of Recombinant Allophycocyanin β-Subunit (Holo-apcB)

ZHOU Sun-lin , CHEN Hua-xin , JIANG Peng , LI Fu-chao , TANG Dong-shan

2014, 30(8):112-116.

[Abstract](1475) [HTML](0) [PDF 529.32 K](1065)

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In this study, a recombinant allophycocyanin β-subunit (holo-apcB) [Thermosynechococcus elongatus BP-1] was biosynthesized in recombinant Escherichia coli by using metabolic engineering technology. Holo-apcB was then isolated and purified using affinity chromatography. SDS-PAGE analysis showed that there was a band with a molecular weight close to 18.4 ku, which matched the theoretical molecular weight of holo-apcB. Spectrum analysis showed the maximum absorbance and maximum fluorescence emission of holo-apcB were at 615 nm and 640 nm, respectively. Thus, this subunit had the same molecular weight and spectroscopic properties as those of holo-apcB. At 55 ℃, the half-life of holo-apcB reached up to 31.9 h. Comparison of the antioxidant activity of holo-apcB with native allophycocyanin (APC) and apo-apcB showed that holo-apcB had the highest antioxidant activity. Moreover, the holo-apcB IC50 values for hydroxyl and peroxyl radical-scavenging activities were 224.9 μg/mL and 20.6 μg/mL, respectively, which were significantly lower than those for apo-apcB and native APC. Therefore, it was suggested that phycocyanobilin also has antioxidant functions.

19 Analysis of Quality on Modified Atmosphere Packaged Cobia Fillet during Freezing-point Storage

WU Yan-yan , SUN Ji-ying , YANG Xian-qing , MA Hai-xia , HUANG Hui , CEN Jian-wei

2014, 30(8):117-124.

[Abstract](1417) [HTML](0) [PDF 539.25 K](837)

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Changes in quality of cobia fillet in freezing-point storage with modified atmosphere packaging (MAP), air packaging (AP) and vacuum packaging (VP) were studied. During the experimental process, some quality indexes such as K value, total bacterial number, TVB-N value, pH value, water holding capacity, drip loss, sensory quality, texture indexes and color were measured. The results showed that, under the MAP condition, it cost 18 d for K value arrive 60% of early corruption by 106 CFU/g of the total number of bacteria , comparing to AP or VP 6d and 2 d were extended respectively. It is 23 d for TVB - N content arrive 0.30 mg/g storing under MAP condition, comparing to AP or VP, 9d and 6 d were extended respectively. Drip loss and pH value of the cobia fillet with MAP increased slowly than with AP or VP. Change rate of water holding capacity, sensory quality, texture and color with MAP was slower than control samples. After the comprehensive comparison of the conclusion: MAP cobia fillet could has a 8~10 days and 2~6 days longer storage time than AP or VP, which showed that MAP cobia fillet during freezing-point storage has the obvious delay the deterioration. It is more suitable for application in high quality cobia fillet storage.

20 Preparation and Structural Characterization of Octenyl Succinic Anhydride Modified Inulin

ZHANG Xiao-yun , YAN Xiao-jing , SHI Jin , ZHU Yi , ZHENG Yan , DING Wen-hui

2014, 30(8):125-130.

[Abstract](1078) [HTML](0) [PDF 685.96 K](759)

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The preparation of octenyl succinic anhydrid (OSA) modified inulin in aqueous medium was studied. The effects of the inulin concentration, reaction temperature, pH value, the additive amount of OSA were investigated by single factor experiments with the degree of substitution (DS) as measurement index. The synthetic conditions of OSA modified inulin which were optimized by orthogonal analysis were as follows: OSA/AFU molar ratio of 0.35, temperature 30℃, pH 8.5~9.0, 25% (m/m) concentration of inulin. The structures of the product were determined by means of scanning electron microscopy(SEM),fourier transform infrared spectroscopy(FT-IR), carbon-13 and proton nuclear magnetic resonance spectroscopy (13C NMR and 1H NMR). The results showed that the surface structure of OSA modified inulin particles were damaged and lost their original smooth surface structure. Infrared datas showed that carbonyl absorption peak of ester bond appeared at 1733.72 cm-1 and alkenyl absorption peak of octenyl succinic anhydride appeared at 1569.80 cm-1. Characteristic absorption peaks of the carbonyl carbon and carboxyl carbon were appeared at 175.6 ppm and 176.5 ppm in the 13C NMR diagram. The absorption peaks of methylene protons and methyl protons in the chain of OSA molecule were discovered about 1.2ppm, 0.8ppm chemical shift in the 1H NMR diagram. These results demonstrated that the OSA group had been linked with inulin molecules by the ester bond.

21 Effect of High Shear Dispersing Emulsification Technology on the Water Status in Soy Protein Isolate Gel

LIU Jun-mei , WANG Dan , LI Zhuo-wei , YU Li-mei , WANG Qing , ZHANG Lan , YANG Pan-pan , WANG Hui , WANG Lu , YU Han-song , HU Yao-hui

2014, 30(8):131-137.

[Abstract](1021) [HTML](0) [PDF 701.22 K](859)

Abstract:
In this study, the effects of high shear dispersing emulsification (HSDE) technology on the water status of transglutaminase-induced soy protein isolate (SPI) gel were investigated. Low-field nuclear magnetic resonance (LF-NMR) technology was used to study the effect of HSDE technology on the water status in SPI gels, in terms of water distribution, water mobility, and water holding capability (WHC). The results indicated that the mobility of bound water increased whereas that of free water decreased in the HSDE-treated gel. Additionally, bound and free water in HSDE-treated samples could be immobilized. Magnetic resonance imaging (MRI) revealed that water was distributed evenly in the gel treated with HSDE. According to the correlation analysis, HSDE showed a significant negative correlation with T21, T22, and T23, but it positively correlated with the WHC of the gel. Analysis of WHC showed that HSDE technology could improve the WHC of transglutaminase-induced SPI gel, which improved significantly during storage.

22 Preparation and Properties of PVDF/PTFE Composite Membrane by Spin-coating

XIAO Kai-jun , CAI Sheng , DONG Rui , ZHU Liang

2014, 30(8):138-143.

[Abstract](2602) [HTML](0) [PDF 785.36 K](2166)

Abstract:
Spin-coating technique applied to film preparation stands out among other techniques owing to its advantages in terms of affording precise control of film thickness and producing minimal pollution in addition to being cost effective and energy saving. In this study, a PVDF/PTFE composite membrane was prepared by spin-coating; the preparation process was optimized, and the mechanism of film formation in spin-coating was investigated. Through single-factor experiments, the effects of the concretion of PVDF solution, spin speed of the spin coater, and the film-forming temperature on the tensile strength and water flux of the composite membrane were examined. The variations in pore size of the composite film adhesive layer were analyzed using scanning electron microscopy. The results showed that the optimum preparation conditions for PVDF/PTFE composite membrane were as follows: PVDF solution concentration of 6 g/L; coater spin speed of 2500 r/min, and film-forming temperature of 90 ℃. Under these conditions, the film thickness of the prepared composite film was 200 μm, the average pore size was 20 μm, the tensile strength reached up to 26.34 MPa, and its water flux reached up to 605.2 L/(m2·h). Furthermore, the mechanism of PVDF/PTFE composite film formation using spin-coating involved Van der Waals forces and other intermolecular forces acting between PVDF sol molecules and the PTFE micro-porous membrane, while the adhesive effects resulted from hook bonding and nail bonding formed by penetration of PVDF sol-gel molecules into the pores of the PTFE membrane.

23 Characteristics and Mathematical Models for Hot-air-dried Rapeseed (Brassica napus)

YANG Ling , CHEN Jian , YANG Yi-li , YANG Ming-jin , GUO Meng-bao , LAN Yu-bin

2014, 30(8):144-150.

[Abstract](1309) [HTML](0) [PDF 580.90 K](705)

Abstract:
Drying and storage of rapeseed directly affects its physiological characteristics, potential for breeding, as well as processing characteristics and quality of rapeseed oil produced. In order to provide a technical basis for designing equipment and optimization of process control for hot-air drying of rapeseed, the characteristics of hot-air-dried rapeseed (Brassica napus) under different conditions of moisture content, hot air temperature, and air velocities were investigated, and the applicability of 10 mathematical models for the process of hot air-drying rapeseed was compared. The results showed that there was no apparent constant-rate drying period in the hot-air-drying process, and moisture removal mainly occurred in the falling-rate drying period. Of the various models tested, the page model was found to be the best mathematical model for describing the drying characteristics of rapeseed and the predicted drying characteristic curves fitted well with results obtained. Hot air temperature was the main factor that affected the drying process of rapeseed. With the increase of temperature, the effective moisture diffusion coefficient of rapeseed increased. When the hot air temperature increased from 45 ℃ to 65 ℃, the coefficient increased from 3.835 × 10-10 m2/s to 7.666×10-10 m2/s and the activation energy for rapeseed drying was 29.26 kJ/mol.

24 Preparation and Physicochemical Properties of an Amylose-conjugated Linoleic Acid Complex

CHANG Qing-qing , ZHOU Xing , XU Yan , WU Chun-sen , XU Xue-ming , JIN Zheng-yu

2014, 30(8):151-156.

[Abstract](1237) [HTML](0) [PDF 586.33 K](821)

Abstract:
In this study, the amylose prepared from debranched, waxy, maize starch as wall material and conjugated linoleic acid (CLA) as the guest molecule were used to prepare an amylose-CLA complex, using the water-ethanol complexation method. Scanning electron microscope, X-ray diffractometer, and differential scanning calorimeter were used to verify complex formation, and particle size distribution, storage stability, solubility, and oxidative-stability of the complex were examined. The results showed that the amylose-CLA complex had a massive, typically V-shaped structure, with a smooth surface and an endothermic peak at 83 ℃. The particle size of the complex in aqueous solution was in the nanoscale range, albeit, with poor storage stability. After ultrasonic treatment, the particle size of the complex was further decreased, and solution stability of the solution was improved. At ambient temperature, the solubility of amylose-CLA complex in water was 62.64%, which increased with an increase in temperature, to a maximum of 91.05% at 90 ℃. Oxidative stability of CLA improved after it formed the complex with amylose. This finding indicated that the treatment using amylose to wrap CLA was an effective method to improve the solubility and chemical stability of CLA.

25 Foreign Body Detection in Yoghurt Using Electrical Impedance Tomography

YANG Jian-xiong , CUI Meng , LI Xing-shu

2014, 30(8):157-162.

[Abstract](1040) [HTML](0) [PDF 796.04 K](1008)

Abstract:
In this study, electrical impedance tomography was used to detect a foreign body in yoghurt. It was found that variations in the size of the foreign body, applied current, and current frequency showed corresponding changes in the reconstructed image. A 16-electrode data acquisition system was established to obtain image data using an adjacent excitation/measurement scheme. The Modified Newton-Raphson algorithm was applied to reconstruct the image data, binarization was performed for post-processing of the reconstructed images, and a quantitative analysis was performed by comparing the deviations of both the coordinates and area of the images with those of the actual foreign body. The results showed that this method could detect plastic foreign objects within yoghurt, but could not determine the location and shape of the foreign body accurately. In addition, this method was sensitive to the size of the foreign body, but only within a certain range. Optimum detection was possible within a detecting region diameter of 100 mm, under the following conditions: 25 mm size of the foreign body, 15 mA current, and 30 kHz current frequency. Although some details of the original reconstructed image might be lost with this processing method, the image obtained allowed for easier observation and convenience in comparison of imaging results under different conditions.

26 Construction of Kinetics Model for Production of Microbial Oils by Saccharomyces Cerevisiae As2.516 Fermentation Process Using Hydrolysis Liquid of Kitchen Garbage

SUN Shi-quan , JIANG Chang-bo , ZHOU Qian , LIU Qing-zhi , TAN Wan-chun , NIE Xiao-bao , WAN Jun-li , YU Guan-long

2014, 30(8):163-168.

[Abstract](1286) [HTML](0) [PDF 462.41 K](693)

Abstract:
In order to increase the production of microbial oils and indicate its regular pattern during fermentation process, Saccharomyces cerevisiae As2.516, was used to set up the kinetics models based on the optimal fermentation conditions: the initial addition of hydrolysis liquid of kitchen garbage was 90% (V/V) and the initial pH value of medium was 6, the inoculum was 10% (V/V) at 30 ℃ for 10 d with agitation speed at 180 r/min and aeration rate at 2.5 L/min in a 1L fermentator. Results showed that the S. cerevisiae As 2.516 biomass accumulation presented an S-shaped curve during fermentation, the production of microbial oil displayed a closed correlation with the bacteria biomass. The batch fermentation kinetic models were established (cell growth kinetic model, substrate depletion kinetic model, production formation kinetic model) based on Logistic equations, Luedeking-Piret equations and mass balance calculation. Cell growth kinetic model was , substrate depletion kinetic model was, and production formation kinetic model was, The experimental results fit the predictive values from these proposed models.The correlation coefficients R2 of the three equations were 0.9979, 0.9957, 0.9565, respectively, which indicated a good correlation between experimental values and models. Therefore, those models could be used to describe the process of cell growth, substrate consumption for production of microbial oils by S cerevisiae As2.516 during batch fermentation. The establishment of batch fermentation kinetic models could lay a foundation for theory and provide practical instruction for the application of production microbial oils.

27 Bioethanol Production by Stepwise Saccharification and Fermentation of Sugarcane Bagasse by Using Mild Alkali Pretreatment

XIE Wen-hua , ZHU Zhi-sheng , ZHU Ming-jun

2014, 30(8):169-174.

[Abstract](1209) [HTML](0) [PDF 507.08 K](939)

Abstract:
Sugarcane bagasse, the main waste product of the sugar industry, is an important renewable biological resource owing to its wide variety of sources and high cellulose content. Based on the cellulose content analysis, sugarcane bagasse was prepared with mild alkali, followed by stepwise saccharification and fermentation, to produce bioethanol. The results of orthogonal experiments showed that enzyme dosage significantly affected enzymatic hydrolysis, where optimal conditions for hydrolysis were as follows: enzyme dosage of 25 FPU/g sugarcane bagasse, temperature of 50 ℃, and an initial pH of 4.9. Under these optimal conditions, the enzymatic efficiency could reach up to 74.26%. Supplementation of the bagasse hydrolysate with certain nutrients facilitated yeast growth and fermentation to produce ethanol. After 96 h fermentation, the final ethanol concentration was 39.79 g/L, with a fermentation efficiency of 82.70% and an ethanol yield of 0.48 g/g. This study confirmed the feasibility of using mild alkali to pretreat bagasse hydrolysate for ethanol production by fermentation and demonstrated the benefit of pretreating sugarcane bagasse before use as raw material for ethanol production.

28 Mathematical Model for Prediction of Compression Heating of Foods Processed with Ultra-high Hydrostatic Pressure

WANG Biao-shi , LI Bian-sheng , ZENG Qing-xiao , DU Jian-zhong , PENG Yuan-huai , JIANG Min

2014, 30(8):175-181.

[Abstract](996) [HTML](0) [PDF 582.14 K](710)

Abstract:
In this study, we aimed to predict the behavior of foods during compression heating using ultra-high hydrostatic pressure and to accurately control processing conditions for sterilization. The compression heating values of food and their components under low heat loss (simulated with a Teflon sleeve) were measured and a method to predict the compression heating value for a particular food item was proposed. A comparison of the estimated and measured values showed that this method could accurately predict compression heating values of food. Within a certain range of pressure and temperature, the compression heating value of food could be determined using the initial temperature and pressure, as derived from the first law of thermodynamics. The fitted compression heating value was obtained from an empirical equation, and the relationship between compression heating values of food and initial pressure/temperature was established. The compression heating values of water, soybean oil, and olive oil were determined under the lower heat loss of 100~400 MPa and 22~55 ℃. The results showed that the three regression coefficients (R2) obtained by applying the regression equation were 0.976, 0.990, and 0.981, respectively. In addition, the measured value was compared with the value predicted using the equation and the relative errors were found to be less than 5%. This finding indicates that this equation provides a valid prediction.

29 Changes in Composition and Physicochemical Properties of Okara Dietary Fiber Treated with Different Ionic Liquid

YE Fa-yin , ZHANG Yin , QIAN Gui-ming , FAN Hong-Xia , LIU Jia , ZHAO Guo-hua

2014, 30(8):182-186.

[Abstract](1329) [HTML](0) [PDF 478.90 K](762)

Abstract:
The aim of this study is to determine the effect of ionic liquids (ILs) on the composition and physicochemical properties of okara dietary fiber and to broaden the application of okara in the food industry. Fresh okara containing rich, insoluble, dietary fiber (IDF) was used as raw material to study the changes in composition and physicochemical properties of dietary fiber treated with different ILs. The results showed that soluble dietary fiber (SDF) content of okara increased significantly with ionic liquid treatment. However, this effect waned with the extension of the cationic groups in the IL. The enhancement effect of ILs with acetate groups was better than that of ILs with chloride ion. In all, the largest increase was observed with 1-ethyl-3-methylimidazolium acetate (EAC), where the okara SDF content increased from 5.97×10-2 g/g to 0.17 g/g and the SDF/IDF ratio increased from 0.17 to 0.69. IL treatment also changed the monosaccharide composition of the SDF and IDF, the okara microstructure was damaged due to swelling, and its crystal structure was destroyed. After IL treatment, the water-holding and oil-holding capacities of okara dietary fiber increased by 10% and 16%, respectively. Therefore, IL treatment is an effective approach to increase the SDF content and improve the hydration properties of okara dietary fiber.

30 Effect of Different Thawing Methods on the Quality of Quick-frozen Buckwheat Wantuo

PENG Deng-feng , CHAI Chun-xiang , ZHANG Kun-sheng , WANG Wei

2014, 30(8):187-193.

[Abstract](1164) [HTML](0) [PDF 491.64 K](874)

Abstract:
Compared with buckwheat wantuo that were not quick-frozen, the quality of quick-frozen buckwheat wantuo, thawed using different methods was investigated. Four thawing methods were compared, namely natural air, microwave, atmospheric pressure cooker, and ultrasonic thawing. The results showed that the microwave method required 53 s, which was the shortest thawing time among the four methods. In terms of texture, the estimates for hardness, gumminess, and chewiness of quick-frozen buckwheat wantuo using microwave thawing were 1923 g, 1636 g, and 1548 g, respectively, which were the closest to those of the control. Natural air-thawing and ultrasonic thawing showed relatively high levels of hardness, with low levels of chewiness. The sensory scores of the sample using microwave thawing and the control were 81.20 and 81.00, respectively, with no significant difference (p > 0.05). In terms of color, the ΔE* values with microwave thawing and atmospheric pressure-cooker thawing methods were less than 2, while their individual effects on the color of quick-frozen buckwheat wantuo could not be distinguished by the naked eye. The rate of water loss with microwave method was 2.23%, which was the closest to that observed with the control method. Microwave thawing showed the lowest bacterial countsof 278 CFU/g, among all four thawing methods. As compared to the control, all four methods showed an impact on volatile flavor. This study demonstrated that microwave thawing was the most suitable method to thaw quick-frozen buckwheat wantuo.

31 Effect of Barrier Property of Packaging Material on the Quality of Dezhou Braised Chicken

LU Li-li , HU Hong-hai , ZHANG Chun-jiang , HUANG Feng , ZHANG Xue , ZHANG Hong

2014, 30(8):194-200.

[Abstract](1213) [HTML](0) [PDF 589.73 K](781)

Abstract:
Dezhou Braised Chicken was vacuum packed using three different barrier packaging materials. In order to study the effect of barrier property of packaging material during storage, physical and chemical indicators of braised chicken, such as surface color changes, thiobarbituric acid (TBA) content, and volatile compounds were measured, and sensory evaluations were conducted. The results indicated that the L* and a* values of the braised chicken packed with common packaging material decreased rapidly, and significant browning occurred on Day 5 (L* value decreased from 50.02 to 46.34 and a* value decreased from 16.33 to 13.17)). In contrast, the L* and a* values of the braised chicken packed using two high-barrier packaging materials did not change significantly (p > 0.05) from the initial values, upon storage (L* value: 50.02; a* value: 16.33). For the two high-barrier packaging materials, the TBA values after 20 days were 0.60 mg/kg and 0.65 mg/kg, which were significantly lower than that for the common packaging material (0.76 mg/kg; p < 0.05). The results from the electronic nose method and GC-MS analysis indicated that more volatile, sulfur-containing compounds and volatile compounds from spices were preserved with high-barrier packaging materials. With increasing storage time, rancid taste appeared with common packaging material, but not with high-barrier packaging materials. In summary, high-barrier packaging could effectively maintain the original color of braised chicken, delay lipid oxidation, and retain original flavor.

32 Effect of Different Curing Strategies on Curing Rate and Quality Index of Duck Meat

XU Wei-min , YIN Yan-tao , ZHU Yong-zhi , BIAN Huan , WU Hai-hong , WANG Dao-ying , GENG Zhi-ming , LIU Fang , ZHANG Mu-han

2014, 30(8):201-205.

[Abstract](1368) [HTML](0) [PDF 489.39 K](834)

Abstract:
To investigate the effect of vacuum and pressure on curing rate and duck meat quality, this study evaluated the pulsed vacuum brining (PVB), pulsed pressure brining (PPB), vacuum and pressure combined brining (VPB) on the curing rate and the quality indexes of duck meat samples including pH, cooking loss, protein content and shear force, with atmospheric pressure brining (APB) as the control. Results showed that the salt content of the muscles after APB, PVB, PPB, and VPB treatment was 2.61%, 3.01%, 2.91%, 3.21% respectively. The pH-value showed a declining trend without significant difference between the four treatments (p>0.05). Compared with that of APB, PVB and VPB could reduce the cooking loss, while PPB increased the cooking loss. After curing for 4h, the shear force of the muscles treated by APB, PVB, PPB, and VPB was 1076g, 938g, 1093g, 908g respectively, and the shear force PVB and VPB treated muscles were significantly different from that of APB, (p<0.05), whereas there was no significant difference between PPB and APB brined muscles (p>0.05). Protein content of PVB, PPB and VPB treated muscles all greatly increased compared with that of APB (p<0.05). On the whole, with regard to the curing rate and duck meat quality, the VPB treatment had more advantages than PVB and PPB.

33 Effect of Temperature on the Freshness and Taste of Muraenesox cinereus during Vacuum Drying

ZOU Lei , WAN Jin-qing , ZHONG Yao-guang , YAO Zhi-yong , LI Jia , ZHAO Yan-feng , LI Jian-guo , GAO Xian-chu

2014, 30(8):206-211.

[Abstract](1275) [HTML](0) [PDF 578.68 K](762)

Abstract:
The effect of temperature on the freshness and taste of Muraenesox cinereus during vacuum drying were studied. Five different drying temperatures were tested: 14 ℃ (mode I), 8 ℃ (mode II), 3 ℃ (mode III), ice-temperature (mode IV), and -3 ℃ (mode V). The results showed that the drying rate declined gradually as the vacuum drying temperature decreased, while the moisture content gradually increased. The minimum K value (freshness quality index) in the fillet dried at -3 ℃ during vacuum drying was 1.05%, which was very close to that of the fresh sample. The highest content of inosine monophosphate (IMP) (130 mg/100 g) was detected in the fillet vacuum-dried at ice-temperature, which was higher than that detected at other temperatures. For the filets vacuum-dried at -3℃, the IMP content was low, at 46 mg/100 g. In terms of free amino acid and main flavor-free amino acid, the increments for the K values of the filets dried at ice-temperature during vacuum drying were 22.61%, 22.59%, respectively, which were better than other conditions. In summary, for the five tested vacuum-drying temperatures, the freshness of the filets vacuum-dried at -3 ℃ was the best, with a lower content of flavor compounds. In contrast, vacuum drying at ice-temperature produced samples of excellent-grade freshness and a relatively high content of flavor compounds, IMP, and free amino acids.

34 Effect of Irradiation on Quality of Freshly Cut Color Pepper

SHEN Yue , LIU Chao-chao , GAO Mei-xu , MOU Hui , LI Shu-jin , ZHAO Xin

2014, 30(8):212-218.

[Abstract](1372) [HTML](0) [PDF 620.62 K](841)

Abstract:
In order to extend the shelf life of color pepper and enhance its product value, 60Co-γ irradiation was used to the processing of freshly cut color pepper. The effect of different doses on the decontamination, nutritional value, and physicochemical properties of color pepper was studied. The results showed that γ-irradiation could effectively reduce bacterial load in freshly cut color pepper. An irradiation dose of 0.52 kGy or higher significantly reduced the total bacterial count and coliform load, thus meeting the requirements of national and local standards. Irradiation resulted in eradication of Salmonella enteritidis (D10 = 0.22 kGy) and Listeria innocua (D10 = 0.21 kGy), with no bacteria detected in the color pepper samples, and a contamination level of 102 cfu/g was achieved. Irradiation at doses 1.81 kGy had no significant impact (above 5% level) on the weight loss, soluble solid content, and nitrite content of the color pepper samples. Moreover, irradiation delayed the loss of firmness and Vc content and did not significantly affect sensory aspects such as color, smell, texture, flavor, and tissue. Irradiation of 0.52~1.81 kGy was thus shown to effectively control microbial population in freshly cut color pepper samples without affecting its edibility or sensory qualities, which extended its shelf life up to six weeks.

35 Effect of Ice-temperature Storage and Modified Atmosphere Packaging on the Texture and Physiological Characteristics of Winter Jujube

LU Gui-long , YANG Shao-lan , ZHANG Xin-fu , ZHENG Bo-wen , HE Wen-jie

2014, 30(8):219-224.

[Abstract](1277) [HTML](0) [PDF 538.22 K](817)

Abstract:
The fruit texture properties such as firmness, adhesiveness, springiness, cohesiveness, and chewiness, as well as storage-related physiological indicators were measured in this study. The results showed that ice-temperature storage delayed the reduction in firmness, adhesiveness, and springiness, postponed fruit senescence, and lowered the soluble pectin content, thereby preventing softening of the winter jujube. Fruit packaged in modified atmosphere showed better texture than the control, and the rate of weight loss during storage was significantly lower than that with control as well as that with ice-temperature storage. After 20 days storage, the rate of weight loss in the control, fruits treated with ice-temperature storage, and fruits packaged in modified atmosphere were 12.02%, 10.25%, and 1.17%, respectively. Modified atmosphere packaging delayed the decrease in Vc content and maintained higher nutritional quality of the winter jujube fruit. Ice-temperature storage delayed anthocyanin synthesis in the fruit peel, which showed less than one-third red coloration after 20-day storage, whereas anthocyanin synthesis occurred normally in the fruits packaged in modified atmosphere. In summary, modified atmosphere packaging was more effective for fruit storage than ice-temperature storage.

36 Volatile Flavor Compounds in Regular and Purple Sweet Potato Yogurt

HE Hong-jun , ZOU Hui , SUN Ning , YANG Ying-ying , ZHANG Xue-ting , ZHAO Yu-ping

2014, 30(8):225-230.

[Abstract](1512) [HTML](0) [PDF 465.01 K](792)

Abstract:
In this study, volatile flavor components of purple sweet potato yogurt and regular yogurt were extracted by headspace solid-phase micro-extraction, detected by gas chromatography-mass spectrometry, and identified using the NIST Library automated retrieval system. There were 75 and 46 volatile compounds detected and identified from purple sweet potato yogurt and regular yogurt, respectively. Characteristic flavor compounds such as acetic acid, acetaldehyde, diacetyl, and delta-nonalactone were detected in both products. Three aromatic heterocycles and one terpene were detected in regular yogurt, accounting for 1.42% and 0.77%, respectively, whereas six aromatic heterocycles and five terpenes were detected in purple sweet potato yogurt, accounting for 2.33% and 5.96%, respectively. Neroli, guaiacol, vanillin, etc. were identified from purple sweet potato yogurt only, whereas neroli was accounted for 4.77%. These characteristic flavor compounds might be present due the purple sweet potato component, which may be responsible for the formation of several volatile and flavor-producing compounds during fermentation, thus giving a lemon-like fruit flavor to the purple sweet potato yogurt.

37 Rapid Detection of Microbial Contamination and Growth in Wheat and Corn

ZHAI Huan-chen , ZHANG Shuai-bing , HUANG Shu-xia , CAI Jing-ping

2014, 30(8):231-237.

[Abstract](1184) [HTML](0) [PDF 538.64 K](727)

Abstract:
To detect contamination and growth of fungi, bacteria, and other microorganisms in grain and its processed products rapidly, a comparative experimental study was conducted by using catalase activity detection and plate culture count methods. For this purpose, gradient dilutions were used in Aspergillus glaucus, Aspergillus flavus, Bacillus subtilis, and other microbial suspensions, which are closely related to the quality and safety of grain and its processed products during storage and circulation. The results showed that for the method involving detection of catalase activity, deviations were relatively small, all linear correlation coefficients were equal to or more than 0.99, and the correlation coefficients between the measured values using this method and those obtained using the plate count method were greater than 0.95. For grain and its processed products with different degrees of microbial contamination, the change in the trend of the measured values using the two methods was consistent. For samples with the same type of microorganisms in grain and its processed products, the catalase activity detection method showed relatively high sensitivity. Additionally, when these microorganisms were in the growth state, the values for enzyme activity were two times higher than that when they were not in the growth state. Therefore, the method based on catalase activity detection is an efficient method to detect contamination and growth of microorganisms in grain and its processed products.

38 Determination of Naproxen in Health Liquor Using HPLC-PAD

GUO Jie-biao , LAN Xian-quan , XIAO ZI-jun , LIU Wang-pei , YAN Xiao-ming , HE Ying-juan

2014, 30(8):238-241.

[Abstract](1247) [HTML](0) [PDF 484.00 K](751)

Abstract:
Recently, undeclared anti-inflammatory drug were frequently exposed being adulterated into antirheumatic health liquors to promote therapeutic effect. This phenomenon poses a serious threat to public health. Naproxen is a common nonsteroidal anti-inflammatory drug. The aim of this study is to develop a liquid chromatographic method coupled with photodiode array detector for identification of illegal adulterated naproxen in healthy food. Two-step liquid-liquid extractions were employed to purify naproxen from samples using chloroform in acidic condition following aqueous solution in alkaline condition, respectively. Chromatographic separation was achieved on a Kromasil 100-5C18 column (250×4.6 mm E74572) with the mobile phase of methanol-10mM phosphate buffer (pH 4.0) (75/25, V/V), at a ?ow rate of 1.0 mL/min. The eluant was detected at 231nm. Retention time combined with standard addition result and PAD-scanning graph were applied to verify naproxen. Quantitation of naproxen was attempted by external standard method. The results showed as follows: the limit of quantitation was 0.5 μg /mL, the linear range was 5~80 μg/mL (R2= 0.9993), RSD was 1.87% (n=6) and the recovery of naproxen from health liquor was ranging from 83.3~92.6%. The method is suitable in determination of naproxen as adulterants in health liquor due to its accuracy and reliability.

39 Polyphenol Composition and Antioxidant Activity of Domestic Wines from Shaanxi Province

SUN Xiang-yu , DU Guo-rong , MA Ting-ting , LIU Xing-yan , WANG Xiao-yu , ZHAN Ji-cheng

2014, 30(8):242-250.

[Abstract](1123) [HTML](0) [PDF 644.48 K](767)

Abstract:
The quality and health benefits of domestic wines sold in the cities of Shaanxi province was evaluated, in terms of polyphenol composition and antioxidant activity. We determined the content of total phenol by Folin-Ciocalteu method, total flavonoids by aluminum chloride method, total flavan-3-ols by p-dimethylaminocynnamaldehyde method, total anthocyanins by pH differential method, monomeric phenols by high-performance liquid chromatography, and antioxidant activity by 1-diphenyl-2-picrylhydrazyl method. The results showed that the sampled domestic wines from Shaanxi Province have a high content of polyphenolic compounds and rich monomeric phenols, which correlated with the designated type, origin, and varietal characteristics of the individual samples. However, few samples also contained exogenously added polyphenolic compounds. No adulterated wines or half-juice variants were found among the sampled domestic wines sold in these cities. In addition, high antioxidant activity was detected in the samples, implying health benefits on their consumption. Evaluation of wine quality by wine tasters is limited by the individual competence and personal preference, whereas the current method uses polyphenol composition and antioxidant activity to evaluate wine quality and therefore, is feasible and effective in comparison. The findings of this study could provide a new quality reference for consumers besides that indicated by the price.

40 Synthesis and Application of MUGal which is the Specific Fluorescent Substrate for Detection of Coliform

MA Yan-xia , WU Qing-ping , ZHANG Ju-mei , GUO Wei-peng , WEI Xian-hu

2014, 30(8):251-257.

[Abstract](1083) [HTML](0) [PDF 604.81 K](797)

Abstract:
4-Methylumbelliferyl-β-D-galactopyranoside (MUGal) is specific fluorescent substrate for rapid detection of coliform bacteria which are the important indicator bacteria for food safety. Protected glycoside was produced from condensation of 4-methylumbelliferone (4-MU) and tetraacetyl-α-D-galactopyranosyl bromide under the conditions of phase transfer catalysis, and then deprotection in H2O/CH3OH solution of sodium carbonate gave 4-methylumbelliferyl-β-D-galactopyranoside. Through the study of temperature, time and amount of catalyst on the yield of glycosylation，we found that when the temperature was 30 ℃ and the reaction time was 16 h, the yield could be up to 73.12%. Yield of alcoholysis reaction with sodium carbonate as base was 91.01%. Structural characterization of target compound was conducted by IR and 1H NMR. The product was further applied to coliform chromogenic medium. Compared with imported products, they were no significant differences in the number of fluorescent tubes by X2 test (P>0.05). In sample test, both positive rate of GB4789.3-2010 (48 h) and MUGal(24 h) were 80%. The detection time was significantly shorter than GB 4789.3-2010. Therefore, the product could be comparable with imported products and could be used as a substitute for imported products.

41 Analysis of Volatile Compounds in Enteromorpha prolifera Harvested during Different Seasons by Electronic Nose and HS-SPME-GC-MS

MIAO Fang-fang , DING Yuan , LIN Jia-liang , HE Hong-ping , ZHU Wen-rong , SU Xiu-rong

2014, 30(8):258-263.

[Abstract](1108) [HTML](0) [PDF 486.93 K](773)

Abstract:
In this study, the composition and spectrum of volatile compounds in Enteromorpha prolifera harvested from winter and spring, were analyzed using electronic nose (E-nose) and head space solid-phase micro extraction combined with gas chromatography mass spectrometry (HS-SPME-GC-MS). The data from E-nose sensors and t-test results showed significant differences in the composition and types of volatile compounds in E. prolifera between samples collected during the two seasons. HS-SPME-GC-MS analysis identified 68 and 82 different volatile compounds in E. prolifera harvested in spring and in winter, respectively. In addition, the main volatile compounds in the former were hydrocarbons and aldehydes, whereas those in the latter were aldehydes and ketones. The relative content of volatile compounds between samples contained in the two seasons differed mainly with respect to alcohols, ketones, acids, hydrocarbons, and heterocyclic compounds. At the same time, among the heterocyclic compounds, a bitter compound, methylpyrazine, was detected in E. prolifera harvested in winter, with a relative content of 0.13%, but it was not detected in samples harvested in spring. Therefore, significant differences were observed in the composition and the types of volatile compounds in E. prolifera harvested in different seasons.

42 Detection of Adulteration of Goat Milk with Cow Milk Based on β-Carotene Analysis

LI Bao-bao , GE Wu-peng , GENG Wei , ZHANG Jing , YANG Jing , LI Yan-li

2014, 30(8):264-269.

[Abstract](1155) [HTML](0) [PDF 518.21 K](738)

Abstract:
The fraudulent practice of substituting goat milk with cow milk is prevalent in the dairy industry. The level of β-carotene in cow milk is much higher than that in goat milk; hence, a quantitative analysis was established using high-performance liquid chromatography for the detection of adulteration of goat milk with cow milk, using the β-carotene level in the milk as a characteristic variable. Milk samples were saponified and extracted with petroleum ether, washed, and concentrated. Subsequently, the sample was eluted on a Shimadzu shim-pack VP-ODS C18 column (4.6 × 150 mm, 5 μm) by using methanol-acetonitrile-chloroform as the mobile phase and a detection wavelength of 450 nm. The variation range of β-carotene in pure cow and goat milk was used to construct the mixing ratio linear curve to perform quantitative analysis. The results showed that the recovery rates of this method were between 89.46% and 98.19%, while the relative standard deviations were between 1.50% and 2.79%. During the main production season, from April to September, the range of β-carotene levels in pure cow milk and goat milk was 0.08~0.13 μg/g and 1.9×10-3~2.2×10-3 μg/g, respectively. Linear correlation coefficients were between 0.9958 and 0.9988, whereas the relative errors of blind samples were between 2.20% and 4.75%. The results suggest that the method using β-carotene as a characteristic variable to evaluate the mixing ratio of cow milk in goat milk is feasible.

43 Preparation of a Biosensor for DNA Damage Detection and its Application in Rapid Detection of Aflatoxin B1 in Feed

FANG Jun-jie , SUN Yu-xue , YE Yong-kang , SUN Han-ju

2014, 30(8):270-275.

[Abstract](1203) [HTML](0) [PDF 585.73 K](747)

Abstract:
In this study, a single-stranded DNA/Au (ssDNA/Au) electrode was prepared by aligning a self-assembled monolayer of thiolated ssDNA onto an Au electrode surface. Under optimal conditions, ssDNA/Au hybridized with the complementary DNA (cDNA) fragment to produce a double-stranded DNA/Au (dsDNA/Au) electrode, which was a useful and cost-effective electrochemical DNA biosensor for the rapid detection of aflatoxin B1 (AFB1). Electrochemical methods such as cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were applied to characterize the electrochemical behavior of ferricyanide and methylene blue (MB) (as electron mediators) on the surface of ssDNA/Au and dsDNA/Au electrodes. A certain concentration of AFB1 reacted with dsDNA/Au to induce DNA damage, thereby reducing the electrochemical signals from MB and allowing for rapid detection of AFB1. Under optimized conditions (ssDNA was self-assembled on gold electrodes for 14 h at 4 ℃ and hybridized with cDNA at 37 ℃ for 2 h to produce the dsDNA/Au electrode; AFB1 solution induced DNA damage for 22 min at 37 ℃), the linear detection range for AFB1 was 10~500 ng/mL, with a satisfactory recovery ranging from 95.99% to 104.57%. This method of AFB1-induced DNA damage detection could be explored as a useful, quantitative method for accurate and rapid detection of AFB1.

44 Home Cooking Stability Study on a Kind of Nutrition-balanced Formula Oil

LI Ke-liang , GE Ya-zhong , YANG Zhan-dong , YANG Ji-guo , NING Zheng-xiang

2014, 30(8):276-279.

[Abstract](1032) [HTML](0) [PDF 432.16 K](702)

Abstract:
The stability of a Nutrition-balanced formula oils with appropriate ω-6/ω-3 fatty acid ratio and rich in linoleic acid and linolenic acid, was investigated by simulation of home cooking. With the commercially available and commonly used edible oil as control, the results showed that when used for cooking green vegetables, pork and green peppers, and cooking in water, the acid value, peroxide value and malondialdehyde (MDA) content of the formula oil were changed, but all conformed to the regulation of GB2716-2005 and GB/T 8937-2006, the formula oil met the requirements of general cooking oil. The fatty acid composition of the oil after cooking was analyzed. Results indicated that there was no obvious deterioration reactions such as oxidation, isomerization took place in formula oil during cooking process. The formula oil, whose polyunsaturated fatty acid(PUFA) content above 60% and ω-6/ω-3 fatty acid ratio under 4:1, was feasible to be used for home cooking , also was an effective way to supplement ω-3 fatty acids to people.

45 Upconversion Fluorescent Nanoparticles Technology in Food Inspection

LI Xiang-li , TAN Gui-liang , ZHANG Na , LIU Yao , WU Shi-jia , WANG Zhou-ping , DONG Jun

2014, 30(8):280-287.

[Abstract](1605) [HTML](0) [PDF 547.38 K](999)

Abstract:
Upconversion fluorescent nanoparticles technology) is a new emerging technique that has attracted increasing attention in recent years. Compared with other labeling techniques such as radioisotopic labeling, enzymatic labeling, chemiluminescent labeling, organic fluorescent dyes, and quantum dots (QDs), upconversion fluorescence nanoparticles have unique advantages such as high photostability, high detection sensitivity, good selectivity, easyobservation and operation, no damage to the sample, and no background fluorescence. In addition, this technique has overcome several shortcomings of other prevalent methods, such as radioactive contamination, enzyme-instability, poor sensitivity, and poor reproducibility of chemiluminescence. It has been widely applied to imaging studies of cells and tissues, quantitative detection of biomolecules, etc., and has achieved remarkable outcomes. In this study, three upconversion mechanisms of UCNPs (e.g., excited-state absorption), their composition, four preparation methods (e.g., hydrothermal method), and six surface modification methods (e.g., Stober method) were reviewed. Subsequently, it provides a perspective to the application of UPNT in food inspection.

46 Detection and Characterization of Gizzerosine in Fish Meal

TAO Zhi-hua , HAN Ling-shuang , XU Xiao-jing , TAN Zhao-ping , LIN Min , CEN Zhi-peng

2014, 30(8):288-291.

[Abstract](1438) [HTML](0) [PDF 385.84 K](761)

Abstract:
Gizzerosine (GZ) in fish meal feed is the causative agent of gizzard erosion and ulceration, inappetence, decreased spawning rate, Black Vomit, and death in chickens, ducks, fish, and other poultry. Gizzerosine is a biogenic amine formed during the flame-drying treatment of brown fish meal. The level of gizzerosine that can cause pathological changes is about 1 mg/kg and its physiological toxicity is 1000 times that of histamine in fish meal. The main pathogenic mechanism is that gizzerosine promotes secretion of large amounts of gastric acid, resulting in gastric mucosal lesions. Poultry farming is the main source of income in agriculture field, and is an important contributor to food-related human health. From the safety point of view in animal husbandry, it is essential to establish an inspection system that is suitable to monitor feed safety affording timely and effective control of factors affecting poultry safety. In this study, the physicochemical properties, toxicity levels, and gizzerosine detection methods were reviewed in the paper, thereby providing a reference for future research on gizzerosine and methods to control the diseases it causes. Thus, it offers a new perspective for gizzerosine-related research.

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Volume 30,Issue 8,2014 Table of Contents