Volume 31,Issue 2,2015 Table of Contents

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  • 1  Patterns of T-2 Toxin Residue in Prawns and Its Subsequent Effect on Genes in Male Mice
    WU Chao-jin MO Bing WANG Ya-ling HUANG Zhan-rui HE Wan-ying SU Jing-yi XU De-feng SUN Li-jun
    2015, 31(2):1-6. DOI: 10.13982/j.mfst.1673-9078.2015.2.001
    [Abstract](1048) [HTML](0) [PDF 919.23 K](1072)
    Abstract:
    This study examined the pattern of T-2 toxin residue in prawns following acute exposure, and the genetic alterations in mice following administration of the poisoned prawns. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to detect the content of residual T-2 toxin in prawns after intramuscular injection. The mice were administered the poisoned prawns by gavage. The results showed that the content of free T-2 toxin in prawns positively correlated with its increasing dose. T-2 toxin appeared to have accumulated in the prawns, and the amounts were significantly different among the various organs. The lowest content of free T-2 toxin was found in muscle; T-2 toxin content was close to zero. The sperm deformity and micronucleus rate of mice gradually increased with an increase in the exposure dose, compared to the control group (P < 0.05). The four organs of the prawns in the high dose group were toxic to the mice, and the toxicity levels were the highest in the muscles and hepatopancreas, followed by the intestinal tract. The results indicated that T-2 toxin in prawns could be easily concealed, especially in the muscle, where free T-2 toxin is converted to masked T-2 toxin. As a result, T-2 toxin could remain undetected, resulting in secondary harm to other organisms.
    2  Effects of Co-overexpression of Squalene Synthase and Dammarenediol-ⅡSynthase in Panax notoginseng Cells on Saponin Synthesis
    YANG Yan LIU Di-qiu GE Feng YU Gang
    2015, 31(2):7-13. DOI: 10.13982/j.mfst.1673-9078.2015.2.002
    [Abstract](902) [HTML](0) [PDF 714.74 K](1179)
    Abstract:
    To study the effects of the co-overexpression of the squalene synthase (SS) and dammarenediol-II synthase (DS) genes in Panax notoginseng cells on saponin synthesis, an overexpression vector of SS derived from P. notoginseng was constructed and integrated into the P. notoginseng genome by culturing with Agrobacterium tumefaciens LBA4404. Expression levels of SS and DS in transgenic cell lines were detected using quantitative reverse transcription-polymerase chain reaction (QRT-PCR), and the saponin contents were determined by the vanillin-glacial acetic acid-perchloric acid colorimetric method. The results showed that for the three strains (T-4, T-5, T-9) in which SS and DS were overexpressed simultaneously, the relative SS expression levels were 5.66, 7.37, and 7.46 times greater than that of the strain with only DS overexpression, and the relative DS expression levels were 1.39, 2.00, and 1.41 times greater than that of the strain overexpressing only DS. The total saponin content of P. notoginseng (PNS) in the three strains was 1.7 times that in the strain overexpressing only DS, and 2.4 times of that observed in normal cells. The total monomer saponin content, including R1, Rg1, Re, Rb1, and Rd, in the three strains was 1.33, 1.61, and 1.71 times greater than that in the strain overexpressing only DS, and 5.62, 6.81, and 7.26 times greater than that in normal cells. In addition, the Re content was significantly higher and reached 5–6 times that observed in P. notoginseng medicinal materials. The results indicated that both SS and DS genes played positive regulatory roles in the saponin biosynthetic pathway, and overexpression of these two genes could further enhance the saponin content, demonstrating that synergistic regulatory effects might exist for two or more genes in the biosynthetic pathway.
    3  Stability of ERIC-PCR and Sau-PCR Techniques on Listeria monocytogenes Typing
    SHI Lei ZHAO Yi-ming ZHANG Zhi-gang YAN He
    2015, 31(2):14-18. DOI: 10.13982/j.mfst.1673-9078.2015.2.003
    [Abstract](1334) [HTML](0) [PDF 697.55 K](1218)
    Abstract:
    To evaluate the stability of enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) and Sau-PCR for typing of Listeria monocytogenes (LM), five isolates of LM from a local vegetable market in Guangzhou and a food processing plant in Xiamen were cultured. DNA was extracted from the cultures incubated at room temperature after 24, 48, and 72 h. In addition, DNA was extracted from the 5th, 10th, 15th, and 20th subcultures. ERIC-PCR and Sau-PCR were then used for typing and changes in fingerprint diagrams with time and increase in the number of generations in subculture were determined. The results indicated that apart from some missing bands, there were no additional bands after room-temperature culture and subculture. However, there were minor changes in the overall band appearance. The homology of ERIC-PCR and Sau-PCR results was higher than 92% and 94%, respectively, indicating that the two typing methods were stable and had epidemiological significance for typing of LM cultures incubated for less than 72 h and 20 generations.
    4  Effect of Dimethyl Dicarbonate Combined with Nisin on Cell Membrane Functions of Leuconostoc mesenteroides in Model Juice
    GUO Huan-li YU Yuan-shan WU Ji-jun XU Yu-juan XIAO Geng-sheng WEN-Jing
    2015, 31(2):19-25. DOI: 10.13982/j.mfst.1673-9078.2015.2.004
    [Abstract](1352) [HTML](0) [PDF 671.13 K](1273)
    Abstract:
    The effects of dimethyl dicarbonate (DMDC) and nisin treatment on the inactivation of Leuconostoc mesenteroides present in model juice and cell membrane functions were investigated. Combined treatment with DMDC and nisin had a fractional bactericidal concentration index of 0.38 (<0.5) against L. mesenteroides, indicating a strong synergistic bactericidal effect of DMDC and nisin. Scanning electron microscopy analysis showed no obvious changes in the cell morphology of L. mesenteroides treated with these antibacterial agents. Treatment with nisin alone increased the membrane permeability of approximately 7% of the cell population; this effect was stronger than that of treatment with DMDC alone. Despite this effect on membrane permeability and the resultant increase in the cellular uptake of extracellular polar substances, nisin treatment could not significantly reduce the loss of intracellular substances. The ultraviolet absorption value of L. mesenteroides cell suspension increased by approximately 60% after treatment with high concentrations of DMDC. To summarize, DMDC and nisin exhibited a synergistic effect on the inactivation of dehydrogenase activity in L. mesenteroides, but not on membrane permeability, loss of intracellular substances, and alteration of intracellular pH.
    5  Properties of Protein Peptides Modified by Dextran in Macromolecular Crowding Condition
    QI Jun-ru WENG Jing-yi ZHUO Xiu-ying KANG Yan-hui FENG Ji-lu YANG Xiao-quan
    2015, 31(2):26-31. DOI: 10.13982/j.mfst.1673-9078.2015.2.005
    [Abstract](1155) [HTML](0) [PDF 658.56 K](1035)
    Abstract:
    In this work, properties of protein peptides modified by dextran in macromolecular crowding condition in liquid system were investigated. The result indicated that the conjugate prepared by protein peptides and dextran reacting at 60℃ for 4h had superior function on the grafted degree, thermal stability, oxidation resistance and emulsification. First, pepsin was introduced for enzymolysis of soybean protein isolated, preparing the glycopeptide. Glycopeptide-dextran covalent conjugate was prepared via Maillard reaction in macromolecular condition. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was used to confirm the formation of covalent conjugate of 7S-dextran. In macromolecular crowding conditions, the Maillard reaction and enzymatic were combined for the protein glycosylated reaction, the enzymatic can greatly shorten the chemical modification reaction time. The pepsin give a driving force to unfold the tertiary structure of protein, promoting the exposure ofε-amino groups and covalent attachment to the dextran.
    6  Properties of Extracellular Protease Produced by Halogranum rubrum RO2-11
    GAO Rui-chang LIU Xiang-dong LU Wen-ting CUI Heng-lin YUAN Li
    2015, 31(2):32-36. DOI: 10.13982/j.mfst.1673-9078.2015.2.006
    [Abstract](1189) [HTML](0) [PDF 567.83 K](1056)
    Abstract:
    In this study, the characteristics of an extracellular protease produced by Halogranum rubrum RO2-11 were studied. Skimmed milk powder medium was used to confirm extracellular protease production, while enzyme activity was determined by Folin-Phenol method. The results showed that Halogranum rubrum RO2-11 produced an extracellular protease with a certain tolerance to high concentration of NaCl. The optimum temperature for enzymatic reaction was 50 ℃. The temperature tolerance of the enzyme decreased at temperatures exceeding 60 ℃. The optimum pH for enzymatic reaction was 8.0. The enzyme showed high activity and stability between pH values of 8.0 and 11.0, demonstrating that the enzyme was an alkaline protease. The enzyme was activated by Ca2+ but was inhibited by Mn2+ and Cu2+. EDTA had a strong inhibitive effect on the protease. However, isopropanol, DTNB (a mercapto reactant) and PMSF (a serine inhibitor) had little influence on the activity of the enzyme, which showed that the enzyme might be a metalloprotease without a mercapto group and tolerant towards organic solvent to a certain extent.
    7  Enhancing Thermostability of Nattokinase by Site-directed Mutagenesis
    LIU Zhong-mei HE Xiao-tian CUI Wen-jing ZHOU Zhe-min
    2015, 31(2):37-41. DOI: 10.13982/j.mfst.1673-9078.2015.2.007
    [Abstract](1444) [HTML](0) [PDF 686.85 K](1188)
    Abstract:
    Cardiovascular and cerebrovascular diseases caused by thrombi are often life-threatening, contributing to the highest mortality rate. This has fuelled rapid development of thrombolytic drugs and functional foods with thrombolytic activity in the past few years. Due to its strong thrombolytic effect, nattokinase (NK) has become the focus of international interest. The aim of this study was to enhance the thermostability of NK. Based on its sequence alignments and crystal structure, NK mutants were prepared by site-directed mutagenesis and the amino acids that might affect NK thermostability were studied. Among the five mutants generated in this study, P14L and N76D showed significantly increased thermostability and their half-life at 65 ℃ improved from 20 min (wild type) to 30 and 50 min, respectively. Homology modeling and molecular dynamics analysis showed that two amino acid sites influenced thermostability and catalytic activity of NK through different mechanisms. This study provides a theoretical and technical basis for the genetic reconstruction, production, and application of NK.
    8  Study on the Antioxidant Activity of Different Forms of Phenolic Compounds in Rice Bran
    CHEN Cai-wei WU Hui LAI Fu-rao MIN Tian DU Xiao-yan TANG Yu-qian LI Xiao-feng
    2015, 31(2):42-46. DOI: 10.13982/j.mfst.1673-9078.2015.2.008
    [Abstract](1418) [HTML](0) [PDF 919.16 K](1281)
    Abstract:
    In this study, the contents of different forms of polyphenol, viz. free, soluble ester, soluble glycoside, insoluble ester, and insoluble glycoside forms, in rice bran were investigated. The in vitro antioxidant activities, including the Fe3+ reducing capacity and 2,2-diphenyl-1-picrylhydrazyl (DPPH), O2-, and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging activities, were evaluated. The results showed that the polyphenol content in free, soluble ester, soluble glycoside, insoluble ester, and insoluble glycoside form in rice bran were 44.70, 80.81, 63.84, 128.63, and 95.46 mg GAE/100 g, respectively. Polyphenols existing in the different forms in rice bran had different antioxidant effects on different systems. Compared to other polyphenols, the polyphenols in the soluble ester form had the strongest Fe3+ reducing capacity (IC50: 37.62 μg/mL). The polyphenols in the insoluble ester form exhibited the best DPPH radical scavenging ability; the DPPH scavenging rate was 93.56% at an insoluble ester concentration of 16.33 μg/mL. The polyphenols in the soluble ester form showed the strongest O2- scavenging capability; the O2- scavenging rate was 91.12% at a soluble ester concentration of 9.66 μg/mL. The polyphenols in the insoluble ester form showed good ABTS scavenging capability, and the ABTS scavenging rate was 91.19% at an insoluble ester concentration of 64.05 μg/mL. These results indicated that rice bran was rich in polyphenols, which had relatively good antioxidant abilities.
    9  Inhibitory Mechanism of Rhein on α-Amylase and Its Molecular Simulation
    LIU Hua LI Shi-xiang ZHONG Ye-jun WU Dan
    2015, 31(2):47-51. DOI: 10.13982/j.mfst.1673-9078.2015.2.009
    [Abstract](985) [HTML](0) [PDF 730.81 K](1294)
    Abstract:
    The inhibitory effect (including inhibitory mechanism, type and kinetic parameters) of rhein on α-amylase and the effect on α-amylase secondary structure were investigated by UV, fluorescence, and circular dichroism spectrometry, while molecular docking of rhein and α-amylase was conducted by molecular simulation. The results showed that rhein was a reversible and competitive inhibitor to α-amylase. The half-maximal inhibitory concentration (IC50) and inhibition constant (Ki) were 0.43 ± 0.02 mM and 0.35 ± 0.03 mM, respectively. Circular dichroism spectra analysis revealed that rhein could alter the content of secondary structure in α-amylase (gradual increase of α-helix content from 12.22% to 22.72% and gradual decrease of β-sheet from 43.24% to 36.43%), indicating that rhein could induce partial conformational changes in α-amylase. Chelating calcium ions experiment indicated that rhein combined with calcium ions at the α-amylase active site. Moreover, the results of molecular simulation indicated that rhein had a binding preference for the α-amylase active site, interacting with the catalytic groups TRP59 and TYR62 by forming hydrogen bonds and π-π interaction. Furthermore, rhein competed with starch, consequently reducing the catalytic activity of α-amylase.
    10  Morphologies and Structures of Waxy Corn Starch Dispersed in a 1-Allyl-3-Methylimidazolium Chloride/Water Binary Blend System
    ZHAO Dan-dong WANG Zhuo-xin FU Xiong LIU Hong-sheng CHEN Hao-xin LIU Jia-ji
    2015, 31(2):52-56. DOI: 10.13982/j.mfst.1673-9078.2015.2.010
    [Abstract](1400) [HTML](0) [PDF 659.99 K](1175)
    Abstract:
    In this study, the effect of the ionic liquid 1-allyl-3-methylimidazolium chloride (AMIMCl) and a AMIMCI/water binary blend system on the morphologies, thermal properties, crystalline structures, and related properties of waxy corn starch granules were systematically studied. A hot-stage microscope was used to monitor the morphological changes of starch granules in the ionic liquid/water binary blend system at room temperature and during the heating process. The thermal behavior and crystallinity of the ionic liquid-treated starch sample were characterized by differential scanning calorimetry (DSC) and X-ray diffraction. The results showed that the AMIMCl/water blend system had a significant impact on the morphology and crystalline structure of starch granules; these properties were closely related to the AMIMCI content. When the AMIMCl content in the solution was less than 50%, the temperature range for the disappearance of the cross-polarization of starch increased with increasing AMIMCI content, consistent with the observation that the endothermic peak in DSC was shifted to the high-temperature side. When the gelatinization temperature was increased to 84 ℃, the strengths of the intramolecular and intermolecular forces of starch increased. When the AMIMCl content in solution was more than 50%, the gelatinization temperature and enthalpy decreased to 62 ℃ and 12.45 J/g, respectively. At the same time, the interchain structures of starch were destroyed, the stability of starch molecules decreased, and starch dissolution and gelatinization occurred simultaneously. In pure AMIMCl, because of the absence of water, only starch dissolution occurred and became more apparent with increasing storage time.
    11  Effect of Ginger Essential Oil on the Physicochemical and Antibacterial Properties of a Gelatin-Calcium Carbonate Edible Film
    WANG Yue-meng LIU An-jun LI Xin HAN Yue TENG An-guo WANG Li-xia
    2015, 31(2):57-62. DOI: 10.13982/j.mfst.1673-9078.2015.2.011
    [Abstract](1284) [HTML](0) [PDF 865.10 K](1093)
    Abstract:
    In order to develop gelatin-calcium carbonate edible films with antibacterial activity, gelatin-calcium carbonate edible films were incorporated with 0%, 1%, and 3% ginger essential oils. The thickness, mechanical properties, water solubility (WS), water vapor permeability (WVP), color, light transmission and transparency, antibacterial activity, surface morphology, and microstructure of the prepared edible films were measured. Additionally, the freshness-preserving effect of edible films on chilled pork stored at 4 ℃ was also investigated. The results showed that after the addition of ginger essential oil, the appearance of the films became darker due to interactions between gelatin and ginger essential oil; also, the tensile strength, WS, and WVP were all decreased to some extent, while the thickness, elongation at break, and antibacterial activity of the edible films were all increased to some extent. Atomic force microscopy (AFM) was used to characterize the microstructure and roughness of the edible films and the results showed that the surface roughness of the ginger essential oil-treated films increased with increasing ginger essential oil concentration. In addition, the preservation experiment on chilled fresh pork showed that the preservative effect of the modified films was improved upon increasing the amount of added ginger essential oil. In summary, the ginger essential oil-edible film, which was developed by the addition of ginger essential oil to gelatin-calcium carbonate edible films, has potential applications in food packaging.
    12  Separation and Identification of the Active Ingredients in Piper nigrum L. Leaves and Analysis of Their Antioxidant Activity
    ZHANG Shui-ping GU Feng-lin HE Shu-zhen WANG Qing-huang
    2015, 31(2):63-69. DOI: 10.13982/j.mfst.1673-9078.2015.2.012
    [Abstract](1102) [HTML](0) [PDF 810.46 K](1173)
    Abstract:
    The leaves and fruit of Piper nigrum Linnaeus (black pepper)exhibit antioxidant activities; the leaves also possess anti-atherosclerotic properties, and the removal of black pepper leaves can increase the yield of pepper fruits. However, the active components in the leaves of Piper nigrum L. were not clear. In order to provide a theoretical basis for the exploitation of Piper nigrum leaves, the antioxidant activity was analyzed by oxygen radical absorbance capacity (ORAC). The results indicated that the ORAC value of the Piper nigrum leaves was 3639.05 μmol TE/g, which was greater than that of the Piper nigrum fruits (fresh, black, and white). Through serial solvent extractions, the ethanol extract of Piper nigrum leaves was determined to have the highest ORAC value. Using the ORAC detection method as the tracing method for the separation and identification of antioxidative components, the active target compounds were isolated after successive extractions of the ethanol extracts of Piper nigrum leaves, followed by silica gel chromatography (Sephadex LH-20 resin), gel-filtration chromatography, reversed-phase chromatography, thin-layer chromatography, and high-performance liquid chromatography. The identification and characterization experiments carried out using nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS) confirmed that hinokinin and rhoifolin-two active ingredients with high antioxidant activities-were separated from Piper nigrum leaves, and their ORAC values were 16070 μmol TE/g and 10823 μmol TE/g, respectively.
    13  Alginate-konjac Glucomannan Microcapsule Preparation and Protective Effect on Lactobacillus acidophilus CGMCC1.2686
    ZHAO Meng CAI Sha QU Fang-ning FANG Ya-peng
    2015, 31(2):70-75. DOI: 10.13982/j.mfst.1673-9078.2015.2.013
    [Abstract](1192) [HTML](0) [PDF 838.50 K](1045)
    Abstract:
    In this study, the physical properties of alginate (ALG)-konjac glucomannan (KGM) microcapsules and their protective effect on Lactobacillus acidophilus CGMCC1.2686 (LAB), particularly the impact of KGM molecular weight were investigated. KGM fractions with different molecular weights were prepared by enzymatic degradation. Mixtures of KGM with different molecular weights and ALG were used as composite wall material to encapsulate LAB via the emulsification/internal gelation method. The capsule mean size increased from 309 μm to between 412 and 452 μm after the addition of KGM to ALG and the mean diameter increased with increasing molecular weight of KGM. Compared to ALG microcapsules, all ALG-KGM microcapsules showed greater mechanical strength, viscoelasticity, encapsulation yield, and LAB survival rate in simulated gastric juice (SGJ) and bile salts (BS). Additionally, microcapsules prepared from intermediate-molecular weight KGM exhibited the highest values for these five indices. Regression analysis showed that survival rates in SGJ and BS positively correlated with mechanical strength of the ALG-KGM composite microcapsules. In conclusion, mixing ALG and KGM enhanced the protective effect of microcapsules on LAB, which in turn, was correlated with KGM molecular weight.
    14  Inhibition Mechanism of 4-Hydroxycinnamic Acid on Reactions Catalyzed by Tyrosinase
    SUN Xiao-mei MU Yan LI Lin HU Song-qing
    2015, 31(2):76-80. DOI: 10.13982/j.mfst.1673-9078.2015.2.014
    [Abstract](958) [HTML](0) [PDF 544.37 K](1594)
    Abstract:
    The purpose of this study was to investigate the inhibition effect of 4-hydroxycinnamic acid (HCA) on the catalytic activity of tyrosinase on the monophenol substrate L-tyrosine and diphenol substrate L-dopa. The mechanism of inhibition was studied using UV-vis spectroscopy, fluorescence spectroscopy, and molecular docking. The results showed that HCA was more effective at inhibiting the catalytic activity of tyrosinase on the diphenol substrate L-tyrosine than on the monophenol substrate L-dopa; their IC50 values were 0.096 and 0.500 mmol/L, respectively. The UV-visible spectrum showed a red shift in the characteristic absorption peak of HCA because of the formation of a Cu2+ chelate complex. Furthermore, fluorescence quenching of HCA in tyrosinase solution did not occur and instead, the fluorescence intensity increased with increasing HCA concentration, indicating that HCA was catalytically oxidized to the corresponding quinone by tyrosinase. Molecular docking demonstrated that HCA could competitively occupy the positions of both monophenol and diphenol substrates in the active site of tyrosinase by hydrogen bonds and hydrophobic interaction, and could coordinate to Cu2+ in tyrosinase, thus inhibiting the catalytic activity of tyrosinase on L-tyrosine and L-dopa oxidation.
    15  Study on Physicochemical Properties and Trypsin Hydrolysis of Acetylated Rice Protein
    LI Yan-yan WANG Li QIAN Hai-feng ZHANG Hui QI Xi-guang
    2015, 31(2):81-86. DOI: 10.13982/j.mfst.1673-9078.2015.2.015
    [Abstract](1360) [HTML](0) [PDF 809.64 K](1391)
    Abstract:
    The physicochemical properties of acetylated rice protein, including solubility, surface charge, and secondary structure, were explored; the enzymatic hydrolysis of acetylated rice protein by trypsin was also investigated. The results showed that the isoelectric point (pI) of acetylated rice protein was decreased with increasing degrees of acetylation. Acetylation improved the solubility of rice protein, as it was increased to 0.7 mg/mL from 0.4 mg/mL (neutral pH) upon acetylation. Acetylation significantly increased the net negative surface charge of the protein, and a higher degree of acetylation led to an increased net negative charge. Meanwhile, acetylation also had certain effects on the secondary structure of rice protein. The α-helix and random coil contents remained the same, while the β-sheet content decreased and β-corner content increased upon acetylation. Acetylation enhanced the enzymatic hydrolysis rate and digestibility of rice protein by trypsin. When the substrate concentration was the same, the kinetic parameter increased with increasing degree of acylation. The electrophoresis results of the enzymatic hydrolysates showed that after enzymatic hydrolysis by trypsin for 120 min, bands at 20 kDa, 16.9 kDa, and 14 kDa were still clearly visible for the unmodified rice protein, while the bands corresponding to the acetylated rice protein almost completely disappeared.
    16  Study on the Thermostability of Starch Whiteness
    ZHANG Ben-shan LI Wei-min HOU Cheng-bo WANG Jian-ping QU Zhe-hui
    2015, 31(2):87-92. DOI: 10.13982/j.mfst.1673-9078.2015.2.016
    [Abstract](1207) [HTML](0) [PDF 650.62 K](1301)
    Abstract:
    Using corn, cassava, potato, and sago starches as raw materials, high temperature treatment from 100 to 200 ℃ was adopted to investigate changes in the whiteness of original starches and starches treated with physical methods. Scanning electron microscopy (SEM) was used to observe the granular morphology of potato starch, which had the most obvious change in whiteness. Results showed that, after heating at 200 ℃, the whiteness of potato starch decreased from 85.88 to 45.51, which was the largest change; corn starch whiteness reduced from 88.21 to 79.10, which was the smallest change. After purification by ethanol, the resultant and original starches showed similar changes in whiteness under vacuum heating. At 200 ℃, the largest change in whiteness occurred in potato starch and the whiteness of all starches was lowered by 2 to 6 compared to their respective original starches. After heating under acidic or alkaline conditions, changes in whiteness were more obvious in the native starches, especially under alkaline condition. After heating at 200 ℃, whiteness was reduced to a range of 13.67 to 24.76. When starches were pre-gelatinized and heated, the changes in whiteness were roughly the same for the different starches; whiteness was very close to 39 at 200 ℃. These results demonstrate that the proteins and lipids in starch have little influence on the changes in its whiteness; however, variation in the thermostability of the whiteness of different starches might be related to their granular sizes.
    17  Isolation, Identification and Preliminary Enzymology of an Acidic α-Amylase-producing Fungus
    ZHANG Da-wei ZHANG Jie WANG Neng-qiang LIANG Fang
    2015, 31(2):93-99. DOI: 10.13982/j.mfst.1673-9078.2015.2.017
    [Abstract](943) [HTML](0) [PDF 812.35 K](1020)
    Abstract:
    An acidic α-amylase-producing fungal strain was isolated from the soil near a vinegar factory and was identified by morphology and ITS sequence analysis. Growth characteristics such as growth temperature and pH of the initial fermentation solution as well as the characteristics of the enzyme produced by this strain were examined. The strain was identified as Aspergillus niger and was named Aspergillus niger ZTL. The optimal growth and enzyme-producing temperatures were determined as 35 ℃ and 40 ℃, respectively, while optimum growth and enzyme-producing pH values were 6.0 and 5.0, respectively. The activity of α-amylase produced was above 80% within the pH range of 4.5 to 7.0. The optimum functional temperature range was between 40 ℃ and 50℃, and the enzyme was stable within this range, as determined by thermal stability analysis. Additionally, the enzyme stability decreased significantly when kept at 60 ℃ for some time. The enzyme was activated by Ca2+ to some extent and inhibited by Mg2+, Fe2+, and Cu2+, while Na+ showed no obvious effect. The Km value was 4.5×10-3 g/L. These results indicate that α-amylase produced by the strain isolated in this study has potential development value.
    18  Effects of Konjac Glucomannan on the Crystal Structure of High Acyl Gellan Gum
    WEN Cheng-rong YIN Na PANG Jie LI Chong-gao SUN Zhong-qi Yu Cheng-cheng
    2015, 31(2):100-105. DOI: 10.13982/j.mfst.1673-9078.2015.2.018
    [Abstract](1206) [HTML](0) [PDF 762.71 K](1046)
    Abstract:
    In order to explore the interaction between natural polymers, the effects of konjac glucomannan on the crystal structure and physicochemical properties of high acyl gellan gum, under heating and microwave treatments, were studied in this work. Changes in crystal structure were analyzed by synchrotron radiation X-ray fiber diffraction, the frequency dependences at 45 and 25 ℃ as well as the temperature sweep in the range of 5~80 ℃ were measured using a rheometer, and the change in thermal stability was measured using the modulated differential scanning calorimetric technique. The results showed that konjac glucomannan led to a diminished crystal lattice but its orthorhombic structure was unchanged. The lattice parameters a, b, and c were changed from 14.6 × 10-10 m, 16.8 × 10-10 m, and 21.2 × 10-10 m to 13.2 × 10-10 m, 13.7 × 10-10 m, and 17.5 × 10-10 m, respectively. Konjac glucomannan caused a decrease in the storage modulus G' and an increase in the loss angle tan (δ) of high acyl gellan gum; the sensitivities of G’ and δ to frequency and temperature were enhanced. No significant differences were found in the impacts of heating and microwave treatments on the physiochemical properties. The results suggested that the helical molecular interaction in high acyl gellan gum was hindered by konjac glucomannan, and konjac glucomannan did not facilitate the formation of high acyl gellan gum gel network and crystalline structure.
    19  Effect of Ethanol on the Structural and Functional Properties of Silk Fibroin
    DONG Wen-xiu LI Jun-sheng YAN Liu-juan HUANG Guo-xia LI Qiu-jie
    2015, 31(2):106-112. DOI: 10.13982/j.mfst.1673-9078.2015.2.019
    [Abstract](1351) [HTML](0) [PDF 812.66 K](1570)
    Abstract:
    In order to study the structural characteristics and functional properties of silk fibroin in the presence of ethanol, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) were used to measure surface tension, emulsifying properties, emulsion stability, foaming properties, foam stability, and protein solubility. The FT-IR spectra indicated a significant increase in the β-sheet structures of the silk fibroin sample after the addition of ethanol to the solvent system. The SEM analysis showed that the silk fibroin was dissolved more completely in the calcium chloride-ethano-water (CCEW) system than in the calcium chloride-water (CCW) system. With increasing dialysis time, the lowest surface tension and critical micelle concentration of the silk fibroin in the CCEW system were much lower than those in the CCW system. In addition, for the CCEW system-treated silk fibroin solution, the best emulsifying property (about 97.51%), emulsion stability (about 355.49%), and foam stability were achieved after dialysis times of 20, 15, and 10 h, respectively. For the silk fibroin solution treated with CCW system, the best emulsifying property (96.23%), emulsion stability (about 200.86%), and foam stability were achieved after dialysis times of 25, 20, and 15 h, respectively. Therefore, the addition of ethanol can effectively improve the structural and functional properties of silk fibroin, and this research could provide a theoretical basis for the development of silk protein-based surfactants.
    20  Effects of Cinnamaldehyde Concentrations on the Performance of Whey Protein Concentrate-Chitosan Composite Film
    MA Zhong-su SUI Si-yao ZHANG Ning WANG Ya-jing CHEN Shan-shan
    2015, 31(2):113-118. DOI: 10.13982/j.mfst.1673-9078.2015.2.020
    [Abstract](1132) [HTML](0) [PDF 736.06 K](1099)
    Abstract:
    Cinnamaldehyde was added into a whey protein concentrate-chitosan composite film to prepare an antibacterial composite film. The microstructures of the composite films were characterized by Fourier transform infrared spectroscopy (FT-IR), and the effects of cinnamaldehyde concentrations on the thickness, transmittance, mechanical properties, water vapor permeability, oxygen permeability, and antibacterial properties of the composite film were studied. Cinnamaldehyde was found to have a good compatibility with the whey protein concentrate-chitosan composite film. The results indicated that the transmittance and tensile strength of the film decreased with increasing cinnamaldehyde concentration. When the cinnamaldehyde concentration was 0.3%, the lowest water vapor permeability (1.15 × 10-13 g?cm/cm2?s?Pa) was obtained. The lowest film thickness and oxygen permeability (1.1 × 10-5 cm3/m2?d?Pa) were observed at a cinnamaldehyde concentration of 0.4%. When the cinnamaldehyde concentration was 0.5%, the elongation at break was the highest (57.5%). The antibacterial efficiency of the film increased with the increasing cinnamaldehyde concentration. The results obtained in this study can provide a new reference for optimizing the processing parameters in the production of cinnamaldehyde-whey protein concentrate-chitosan antimicrobial composite films.
    21  Effect of Polyphenol Oxidase (PPO) Enzymatic Inducing Factors on Non-enzymatic Browning of Apple Polyphenols
    YI Jian-hua DONG Xin-ling ZHU Zhen-bao
    2015, 31(2):119-127. DOI: 10.13982/j.mfst.1673-9078.2015.2.021
    [Abstract](1141) [HTML](0) [PDF 916.12 K](1084)
    Abstract:
    In order to study the effects of apple polyphenol oxidase (PPO) enzymatic inducing factors on the non-enzymatic browning of apple polyphenols, chlorogenic acid and phlorizin were used as reaction substrates, and phosphate buffer was used as the model apple juice system to carry out enzymatic induction under controlled enzymatic induction conditions. Subsequently, the enzyme was deactivated, and the non-enzymatic polymerization in the model apple juice system was carried out at 60 ℃; L*, a*, b*, and △E* values were measured using a colorimeter every 24 h. The results showed that significant differences were found in the impacts of enzymatic inducing factors on the non-enzymatic browning involving chlorogenic acid and phlorizin. In the 3.5~6.0 pH range, the degree of browning in the model juice system containing chlorogenic acid and phlorizin increased with increasing pH values. When the temperature of enzymatic induction was between 20 and 60 ℃, the temperature of the inducing system had no significant effect on the non-enzymatic browning involving chlorogenic acid, while the degree of non-enzymatic browning in the model juice using phlorizin was higher at 40 ℃. A higher degree of non-enzymatic browning was achieved for the model juice using chlorogenic acid and phlorizin when the durations of enzymatic induction were 40 and 30 min, respectively. When the PPO activity was in the range of 14.25~171 U, the increasing enzymatic activity could accelerate the non-enzymatic browning involving chlorogenic acid and phlorizin. Meanwhile, the results indicated that non-enzymatic browning involving phlorizin was related to the haze occurring in apple juice, and the development of the haze in apple juice could be accelerated by increasing the pH, temperature, PPO activities, and duration of enzymatic induction.
    22  Isolation and Identification of the Chemical Constituents in Ethyl Acetate Extracts of Wild Aquilaria sinensis Leaves
    YANG Mao-xun LIANG Yao-guang CHEN He-ru HUANG Yong-fang GONG Hai-guang
    2015, 31(2):128-132. DOI: 10.13982/j.mfst.1673-9078.2015.2.022
    [Abstract](1735) [HTML](0) [PDF 652.60 K](1411)
    Abstract:
    The aim of this study was to explore the material basis for the pharmacological activities of Aquilaria sinensis leaves, which are the main components of the ‘Aquilaria Tea’ health food product series. Dried leaf powder was percolated with an aqueous solution containing 70% acetone and extracted several times using petroleum ether and ethyl acetate. Subsequently, seven compounds were isolated from the ethyl acetate extracts of wild Aquilaria sinensis leaves by multiple techniques including silica gel column chromatography, gel filtration chromatography (Sephadex LH-20), and preparative high performance liquid chromatography (PHPLC). Data from mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy revealed the presence of six compounds: ergosterol (1), quercetin-3-O-?-D- galactopyranoside (2), stigmasterol (3), 5,4-dihydroxy-7-methoxyflavanone (4), ?-sitosterol (5), and quercetin-3-O-?-D-glucopyranoside (6). Based on their structures, the compounds could be classified as three sterols and their derivatives, two flavonoid glycosides, and one flavanone. Among them, compounds 1-2 were first isolated from the family Thymelaeaceae, and compound 4 was the first flavanone isolated from the genus Aquilaria (family Thymelaeaceae). The 2D NMR data and chemical shift assignments of compound 5 were reported here for the first time.
    23  Effect of Added Exogenous Wheat Gluten on Thermomechanical and Dynamic Rheological Properties of Wheat Flour Dough
    LIU Jun-fei TANG Xiao-zhi HU Zhan-qiang GONG Jing-yi LI Ming-ming
    2015, 31(2):133-137. DOI: 10.13982/j.mfst.1673-9078.2015.2.023
    [Abstract](1198) [HTML](0) [PDF 846.78 K](1343)
    Abstract:
    The effects of different percentages of wheat gluten on the thermomechanical and dynamic rheological properties of wheat flour dough were studied by adding wheat gluten protein powder at substitution rates of 0%、5%、10%、15%、20%、25%、30%, by using Mixolab, a rapid visco analyser (RVA), and a dynamic rheometer. The results showed that with the addition of wheat gluten, the water absorption and the dough development time significantly increased from 53.3% to 67% and from 1.41 min to 9.31 min, respectively. On the other hand, the stabilization time first increased and then significantly decreased with increasing substitution rate, with the maximum stabilization time being 10.02 min at a substitution rate of 5%. The addition of wheat gluten significantly lowered the peak torque and setback value of wheat flour dough from 2.06 Nm to 1.37 Nm and from 1.68 Nm to 1.06 Nm, respectively. The dynamic rheological test revealed that the addition of wheat gluten greatly affected the viscoelastic properties of wheat flour dough. Both storage modulus (G′) and loss modulus (G〞) first increased and then decreased, while tanδ increased with the increase of wheat gluten percentage. The only exception was the dough with 5% wheat gluten protein powder, for which tanδ was lower than that of the control when scanned in the low-frequency range. The results indicated that the extent of molecular interactions increased, thus improving the strength of the gluten network of the flour dough.
    24  Preparation of Soybean Peptides and Characteristic Study of Their Maillard Reaction Products
    ZHAO Mou-ming ZHANG Jia-nan WU Chang-ping LIU Yang SU Guo-wan
    2015, 31(2):138-144. DOI: 10.13982/j.mfst.1673-9078.2015.2.024
    [Abstract](1052) [HTML](0) [PDF 650.13 K](1132)
    Abstract:
    In this paper, the technique of using koji to produce soy sauces was simulated, soybean peptides were prepared by fermentation and enzymatic hydrolysis using high-temperature soybean meals as raw materials, and the properties of soybean peptides and their Maillard reaction products were studied. An in-depth analysis of the effects of fermentation, enzymolysis, and enzymolysis time on the antioxidant activities of soybean peptides and their Maillard reaction products was conducted through comparison of their protein recoveries, antioxidant indicators as DPPH scavenging capacities, degrees of browning and molecular weight distributions. The results showed that both fermentation and enzymolysis could significantly increase the protein recoveries and antioxidant activities of the soybean peptides prepared from soybean meals. The highest protein recovery was 77.21% after an enzymolysis time of 24 h, and the half-inhibitory concentration (IC50) of the 2,2-diphenyl-1-picryhydrazyl (DPPH)-scavenging capacity and reducing power (A700) of the enzymatic hydrolysate of soybean were 0.77 mg/mL and 0.16, respectively. However, the antioxidant activity of the Maillard reaction products could be further enhanced. Additionally, the thermal degradation of higher-molecular-weight components during the Maillard reaction was more intense, while the small molecules (oligopeptides) had higher Maillard reactivity than the large molecules.
    25  Effects of High Pressure Microfluidization on the Structure and Rheological Properties of Akebia trifoliata var. australis Seed Protein Isolate
    LEI Li ZHAO Qiang FAN Ting XIONG Hua
    2015, 31(2):145-150. DOI: 10.13982/j.mfst.1673-9078.2015.2.025
    [Abstract](1177) [HTML](0) [PDF 772.31 K](1110)
    Abstract:
    In this study, Fourier transform infrared spectroscopy (FT-IR) and steady shear rheology were carried out to investigate the effects of high pressure microfluidization (HPM, 0.1, 50, 90, 130, 170 MPa) on the conformational and rheological properties of Akebia trifoliata var. australis seed protein isolate (API). The results showed that after HPM treatment, the particle size of API became smaller, subunits of API were unchanged, and solubility increased significantly, as demonstrated by SDS-PAGE. The contents of the total and exposed sulfydryl decreased with increasing pressure. The FT-IR results suggest that the secondary structure of API changed, and the maximum change occurred when the pressure was 130 MPa; the contents of unstable structures such as β-sheets and random coils decreased, while the stable β-turn protein structure content increased, resulting in improved conformational stability of the sample. Rheology measurement indicated that the API solution was a pseudoplastic liquid both before and after HPM treatment, the apparent viscosity of all API solution samples showed a decreasing trend when the shear rate ranged from 0 s-1 to 10 s-1. With the increase of treatment pressure, the apparent viscosity of the API solution showed obvious shear-thinning phenomenon.
    26  Experimental Study of a Method for Mechanical Shrimp Heading
    WANG Ze-he ZHANG Ze-ming ZHANG Xiu-hua WANG Wei
    2015, 31(2):151-156. DOI: 10.13982/j.mfst.1673-9078.2015.2.026
    [Abstract](1009) [HTML](0) [PDF 1.04 M](976)
    Abstract:
    Manual shrimp heading is labor intensive, has low efficiency, and results in a susceptibility of shrimp meat to bacterial contamination. On the other hand, mechanical heading of a shrimp using a guillotine results in a significant waste of shrimp meat. Therefore, this study developed an approach for shrimp heading by double elastic cylinder extrusion. A theoretical analysis and an extrusion experiment were carried out simultaneously. The extrusion process for removing shrimp head can be divided into two phases. In the first phase, a movable elastic cylinder is automatically guided to the weak parts connecting the head and body of the shrimp and is extruded preliminarily. In the second phase, the movable elastic cylinder moves along the side surfaces of a fixed cylinder, further separating the head and body. In this way, the shrimp head is completely separated from the body with negligible loss of the shrimp meat. In the experiment, optimal shrimp heading was achieved at a downward speed (v) of 10 mm/s, an offset distance (e) of 1.29 mm, and a reserve distance (H) of 0 mm for the movable elastic cylinder. Compared with using a guillotine, the double elastic cylinder extrusion for shrimp heading improved the yield of shrimp meat by 11.13%. Therefore, double elastic cylinder extrusion can serve as a basis for the development of shrimp heading devices.
    27  Kinetics and Effect of Storage Temperature on the Browning and Antioxidant Activity of Agaricus bisporus
    WANG Li-fang WANG Xiao-tuo WANG Zhi-dong
    2015, 31(2):157-163. DOI: 10.13982/j.mfst.1673-9078.2015.2.027
    [Abstract](1295) [HTML](0) [PDF 719.55 K](1129)
    Abstract:
    The effects of three storage temperatures, viz. 1 ℃, 4 ℃, and 7 ℃, on the superoxide dismutase (SOD) and catalase (CAT) activities, as well as antioxidant activity of Agaricus bisporus were investigated. The correlations between antioxidant capacity, total phenolic content, and ascorbic acid content, as well as the degree of browning of Agaricus bisporus were explored, and a kinetic model for the change in antioxidant activity of Agaricus bisporus during storage was evaluated. The results showed that low temperature storage (1 ℃) could effectively inhibit the decline of total phenolic and ascorbic acid content in Agaricus bisporus during storage; moreover, it could delay the rise and occurrence of the peak values of SOD and CAT activities, maintain a relatively high antioxidant activity, and effectively inhibit browning. The correlation analysis showed that phenols and ascorbic acid played an important role in the antioxidative properties of Agaricus bisporus, and the color change in mushroom was closely related to the antioxidant capacity during storage. L* value, ascorbic acid level, and rate of change in antioxidant capacity (Trolox equivalent antioxidant capacity (TEAC) and ferric reducing antioxidant power (FRAP) assays) were obtained based on the Arrhenius equation, and increased with elevated storage temperatures. Using the final model equations, the browning and antioxidant activity of Agaricus bisporus could be predicted rapidly and reliably at storage temperatures ranging from 274.15 K to 280.15 K.
    28  Effects of Various Fresh-keeping Techniques on the Quality of Litchi chinensis Sonn. during Storage
    GUO Jia-ming LV En-li LU Hua-zhong LI Ya-hui ZENG Zhi-xiong
    2015, 31(2):164-172. DOI: 10.13982/j.mfst.1673-9078.2015.2.028
    [Abstract](1095) [HTML](0) [PDF 810.46 K](1065)
    Abstract:
    To investigate the effects of various methods for maintaining freshness of Litchi chinensis Sonn. (lychee) fruit during storage, experiments were conducted on the ‘Gui Wei’ (lychee)fruit under various storage conditions, including controlled atmosphere, controlled temperature and humidity, and controlled temperature storage environment, and the effects were comparatively analyzed. The results indicated that the marketable fruit yields after a 20-day storage period using controlled atmosphere, controlled temperature and humidity, and controlled temperature were 1.00, 0.81, and 0.59, respectively. During the first 5 d of the storage period, there was no significant difference in the quality of lychee fruits among the different fresh-keeping methods employed. In the controlled temperature mode, the moisture content of the lychee pericarp rapidly decreased to 57%, and the fruit weight-loss rate quickly increased to 11.52% during storage. In controlled atmosphere and controlled temperature and humidity modes, the moisture content of the lychee pericarp decreased from 73% to 69% and 71%, respectively, while the weight loss rate increased to 2.91% and 2.05%, respectively. There was no significant difference in changes in the total soluble solids (TSS) and titratable acidity (TA) contents in lychee fruit with regard to the fresh-keeping method used. The shelf-life test conducted after 20 d demonstrated that the controlled atmosphere could decrease the lychee weight loss rate during the shelf life. These results provide a reference for the selection of storage and transportation methods for lychee fruit.
    29  Wastewater Treatment Using Microorganisms Entrapped in Sodium Alginate and Pullulan Immobilization Matrix
    QIAO Chang-sheng PENG Qiao LIU Jian-bo WANG Yi-chao LI Xue LI Kun-rong
    2015, 31(2):173-178. DOI: 10.13982/j.mfst.1673-9078.2015.2.029
    [Abstract](1046) [HTML](0) [PDF 542.14 K](1104)
    Abstract:
    The aim of this study was to develop immobilized systems for wastewater treatment by immobilizing microorganisms in mixed matrices. Two bioactive polysaccharides, sodium alginate (SA) and pullulan (Pu), were used to immobilize microorganisms for wastewater treatment. The optimum mechanical strength, elasticity, and diffusion rate of the immobilized beads were obtained upon addition of 1% Pu polysaccharides and 7% SA. Three base strains of bacteria (which produce amylase, protease, and cellulose) were immobilized in SA or Pu matrices for wastewater treatment. The seeding quantity for microbial immobilization was optimized. A seeding quantity of 200 mL during the preparation of immobilized beads helped achieve efficient wastewater treatment. The total nitrogen (TN) and chemical oxygen demand (COD) removal rates observed during the end of a seven-day treatment period were 65.94% and 77.88%, respectively. Three types of immobilized beads were compounded for wastewater treatment. The immobilized beads 11008, 11009, and 10004 were added at concentrations of 0.75%, 0.50%, and 0.50% of the total volume of wastewater, respectively, and wastewater was treated for seven days continuously; the TN and COD removal rates under these conditions were observed to be up to 90.55% and 91.45%, respectively.
    30  Evaluation of the Quality of Xinjiang Grapes with Fuzzy Comprehensive Evaluation Model
    MA Qian-li TIAN Ying-zi YING Li YANG Ren-dang LUO Yu-nian WANG Qing-qing ZHAO Cui
    2015, 31(2):179-183. DOI: 10.13982/j.mfst.1673-9078.2015.2.030
    [Abstract](1064) [HTML](0) [PDF 480.63 K](1104)
    Abstract:
    This article chooses 4 kinds of different Grapes, detects their physical index and nutrition composition, and uses fuzzy comprehensive evaluation method to evaluate the typical types of Xinjiang grapes. Evaluate the grapes by 5 different kinds of factor model, and analyze their quality comprehensively. The results are as follows: Obviously, different kinds of Xinjiang grapes vary from one index to another, such as the difference of soluble solids content between Seedless white grapes and Horse-milk wine can reach at least 10%. Take spike weight, kernel weight, soluble sugar, total acid, Vc, protein, amino acids, dietary fiber, sugar acid ratio and the like as grape quality evaluation elements to establish Xinjiang grapes fuzzy comprehensive evaluation model; Five models are built by different main points. By calculating the detecting results of Xinjiang grapes, and analyzing them, there is a conclusion that the predominant grapes in Xinjiang, the Seedless white grapes (two groups of rank optimal 0.8662, 0.7364) and Munage grapes (three groups of rank optimal 0.7508, 0.7908, 0.6345), have more obvious advantages in the comprehensive evaluation, and the research will be a valuable reference for further Xinjiang grape development.
    31  Effect of Different Processing Techniques on Quality of Black Garlic Products
    WU Qing-mei PAN Si-yi XU Xiao-yun
    2015, 31(2):184-189. DOI: 10.13982/j.mfst.1673-9078.2015.2.031
    [Abstract](1349) [HTML](0) [PDF 753.39 K](1076)
    Abstract:
    Black garlic is a new kind of garlic product. Two different black garlic products, namely No. 1 and No. 2, were obtained using different processing techniques; the production cycle of black garlic No. 1 was three times as long as that of No. 2. In this study, the effects of two different processing techniques on the nutrient composition, allin content, and free radical scavenging capacity of black garlic products were compared. The results revealed that the moisture (around 40%) and alliin contents of the black garlic products were less than those of fresh garlic, and black garlic contained more soluble sugar, protein, and polyphenols than fresh garlic on a wet basis. With the exception of polyphenols, the other contents decreased on a dry basis; the proline and arginine contents decreased significantly, with coefficients of variation of 1.03 and 1.12, respectively. On a wet basis, the OH? radical scavenging capacity of black garlic was similar to that of fresh garlic, and the DPPH? scavenging capacity of black garlic was twice as much as that of fresh garlic. The crude protein content of black garlic No. 1 was lower than that of black garlic No. 2, while the soluble sugar, polyphenol, and alliin contents were greater. The coefficients of variation of crude protein and polyphenol contents were about 0.20, and there were significant differences (P < 0.05) among all components. The extracts from the two black garlic products showed equivalent OH? and DPPH? scavenging capacities at various concentrations. When the extract concentration was 0.05 g/mL, more than 90% of the OH? and DPPH? radicals were scavenged. The two black garlic products could be distinguished using an electronic tongue.
    32  Drying Characteristics and Quality of Carica Papaya Linn under Med- and Short-wave Infrared Radiation and Hot Air Drying
    GAO He YI Jian-yong BI Jin-feng LIU Xuan DENG Fang-ming WU Xing-ye
    2015, 31(2):190-195. DOI: 10.13982/j.mfst.1673-9078.2015.2.032
    [Abstract](1593) [HTML](0) [PDF 640.26 K](1162)
    Abstract:
    The effects of infrared and hot air drying at different temperatures (60, 70, 80, and 90 ℃) on the quality of Carica Papaya Linn (papaya) slices were discussed. Four indicators viz. drying properties, color, rehydration, and vitamin C retention were employed. The results showed that, at the same drying temperature, the speed of infrared drying was faster than that of hot air drying . The effective moisture diffusion coefficients (Deff) increased with increase in drying temperature for both drying methods. The Deff of infrared drying and hot air drying ranged from 0.58546×10-10~9.87313×10-10 m2/s and 0.01179×10-10~ 4.88646×10-10 m2/s, respectively. The activation energy was 32.13 kJ/mol and 33.28 kJ/mol for the infrared and hot air drying, respectively. The papaya slices dried by infrared showed better color and rehydration properties than those dried by hot air. However, the papaya slices dried by hot air had higher vitamin C retention. In summary, the best product was obtained with infrared drying at 70 ℃.
    33  Effect of Metal Salts on the Immersion Method for the Preparation of Preserved Eggs
    LIU Yan LIU Lun-lun ZHOU Zan LUO Can
    2015, 31(2):196-204. DOI: 10.13982/j.mfst.1673-9078.2015.2.033
    [Abstract](1207) [HTML](0) [PDF 709.94 K](1829)
    Abstract:
    Using duck eggs as raw material, the effects of the type and amount of added metal salts on the quality of preserved eggs were studied by comparing the safety performance and sensory quality of preserved eggs prepared by the immersion method, using different metal salt solutions. The experimental results showed that good sensory quality was obtained in preserved eggs prepared by the addition of CuSO4, ,CuSO4:ZnSO4 = 1:1, or ZnSO4:FeSO4 = 1:1, with evaluation scores of 90.6 ± 2.4, 89.8 ± 3.2, or 88.2 ± 2.7, respectively. The sensory quality of the preserved egg prepared by the addition of ZnSO4 was slightly lower, with an evaluation score of 85.80 ± 3.80. Low sensory quality was obtained in preserved eggs prepared by the addition of FeSO4 or MgSO4. For the preserved eggs prepared by the addition of CuSO4: ZnSO4 = 1:1, the concentrations of residual zinc and copper ions (Cu2+: 4.12±0.11 mg/kg, Zn2+: 8.32±0.19 mg/kg) were significantly lower than those of preserved eggs prepared by the addition of zinc salt (Zn2+: 12.96 ± 0.22 mg/kg) or copper salt (Cu2+: 8.55 ± 0.28 mg/kg). The impacts of different zinc salts on the sensory quality of the preserved eggs were different. The concentration of residual zinc ions (Zn2+: 9.27 ± 0.09 mg/kg) and sensory evaluation score of preserved eggs prepared by adding zinc oxide were significantly lower than those of preserved eggs prepared by adding other zinc salts. Based on this comprehensive evaluation, ZnSO4 was found to be a suitable zinc salt for the preparation of preserved eggs. For preserved eggs prepared by the addition of CuSO4 or CuSO4:ZnSO4=1:1, the runny-yolk index was high (0.66 or 0.57, respectively), with good elasticity, hardness, and chewiness. Therefore, considering the sensory quality and the level of metal residues, the qualities of preserved eggs prepared by the immersion method, using CuSO4 and ZnSO4 solutions, were relatively good, while the addition of FeSO4 alone was not suitable for the preparation of preserved eggs.
    34  Sodium Hydrosulfide-induced Chilling Resistance in Postharvest Bananas
    LUO Zi-sheng DU Rui-xue WANG Yan-sheng
    2015, 31(2):205-210. DOI: 10.13982/j.mfst.1673-9078.2015.2.034
    [Abstract](1149) [HTML](0) [PDF 745.40 K](1100)
    Abstract:
    The e?ects of exogenous sodium hydrosul?de (NaHS) treatment on chilling injures in postharvest bananas were investigated. Harvested banana fruits were treated with 0.5 mM/L NaHS at 20 ℃ for 24 h in a sealed container, and subsequently stored at 7 ℃ for 14 days. NaHS treatment delayed the increase in membrane permeability and malondialdehyde (MDA) content, increased antioxidase enzyme (catalase [CAT], peroxidase [POD], ascorbate peroxidase [APX], and glutathione reductase [GR]) activity, and reduced the rate of generation of superoxide anion (O2-) and hydrogen peroxide (H2O2) content in treated banana peels, as opposed to the untreated, control fruits. NaHS treatment also enhanced the accumulation of total phenolics, led to an increase in reduced glutathione (GSH) content, and enhanced total antioxidant capacity. After the 14-day cold storage period, the chilling injury index, relative conductivity, MDA content, O2- generation rate, and H2O2 content in banana fruits treated with NaHS were 5.00%, 5.36%, 10.26%, 11.39%, and 18.78% lower, respectively, than those in the control fruits; CAT, POD, APX, and GR activities were 36.77%, 35.59%, 6.81%, and 21.93% higher, respectively, than those in the control fruits. Moreover, the total phenolics and GSH content in the fruit treated with NaHS were 11.39% and 18.78% higher, respectively, than those in the control fruits. These results suggest that hydrogen sulfide could be used as a signaling molecule to induce chilling resistance in postharvest banana fruits.
    35  Effect of Cold Ozonized Seawater on the Quality of Trachurus japonicas During Refrigerated Storage
    LIU Lin HU Zhuo-jin LV Fei DING Yu-ting
    2015, 31(2):211-217. DOI: 10.13982/j.mfst.1673-9078.2015.2.035
    [Abstract](1037) [HTML](0) [PDF 830.91 K](1031)
    Abstract:
    In this study, the effect of cold, ozonized seawater on the quality of Trachurus japonicus (horse mackerel) meat during refrigerated storage was investigated with respect to the pattern of change in the aerobic plate count (APC), pH value, total volatile basic nitrogen (TVB-N), 2-thiobarbituric acid reactive substances (TBARS), color, texture, and sensory quality. Fish samples were divided into three treatment groups: tap water pretreatment (group A), cold seawater pretreatment (group B), and cold ozonized seawater pretreatment (group C), and stored at 4 ± 1 ℃. The results indicated that APC, TVB-N, and b* values of horse mackerels in the three groups increased with time during refrigerated storage. During the late stage of storage, the inhibitory effect of cold, ozonized seawater on APC and TVB-N by B and C pretreatments was significantly higher than that by pretreatment A, while the overall effect of pretreatment C was found to be better than that of pretreatment B (p < 0.05). On the tenth day, the APC and TVB-N values for the group A were 7.13 log CFU/g and 31.43 mg/100 g, respectively, which exceeded the acceptable limit for fish in China. Meanwhile, the sensory scores decreased with increasing storage time, where scores for group A decreased much faster than those for groups B and C. However, the degree of lipid oxidation for groups B and C was higher than that for A, indicating that cold seawater and ozone pretreatments may promote lipid oxidation. There were no significant effects of cold ozonized seawater treatment on pH, L*, a* values, and texture. In conclusion, the cold ozonized seawater treatment helped delay the decline in freshness indices for horse mackerel meat and maintained quality during refrigerated storage, thus prolonging shelf life.
    36  Effect of Exogenous Antioxidants on the Antioxidant Activity and Sensory Quality of Steamed Bread
    FENG Wei-hua HUANG Shi-qi LI Bing BAI Wei-dong DENG Wan-jun
    2015, 31(2):218-224. DOI: 10.13982/j.mfst.1673-9078.2015.2.036
    [Abstract](1445) [HTML](0) [PDF 718.63 K](1376)
    Abstract:
    In this study, the specific volumes, aging processes, and sensory qualities of steamed breads in two exogenous antioxidant-treatment groups: Vitamin C (Vc) + soybean lecithin group, and Vitamin E (VE) + soybean lecithin group during processing and storage were investigated. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and ferric reducing antioxidant power (FRAP) assays were used to explore the effect of exogenous antioxidants on the content and antioxidant activity of polyphenols- the endogenous antioxidant-during processing and storage. The results demonstrated that the addition of Vc, VE, and soybean lecithin during the steamed bread-making process produced softer steamed bread and slowed down the aging process during a 12~48 h storage time; the specific volumes were 0.67~0.81 mL/g higher than that of the control group, showing a significant increase in specific volumes (p < 0.01); the overall sensory qualities were apparently higher than that of the control group. The DPPH radical scavenging capacity and FRAP (i.e., antioxidant activity) were enhanced during processing and storage. However, the change in total phenolic content (TPC) was not significant (p < 0.05) during the processing and storage of steamed bread. Thus, the addition of Vc, VE, and soybean lecithin could comprehensively improve the quality of steamed bread during processing and storage.
    37  Effect of Different Pre-freeze Conditions on the Quality of Larimichthys polyactis
    DONG Kai-cheng YANG Shui-bing YU Hai-xia CHEN Shi-guo YANG Zhi-jian LU Jun HU Ya-qin
    2015, 31(2):225-231. DOI: 10.13982/j.mfst.1673-9078.2015.2.037
    [Abstract](1226) [HTML](0) [PDF 852.17 K](1128)
    Abstract:
    In this study, the effect of different pretreatments on the quality of Larimichthys polyactis (small yellow croaker) over a storage period of one month was investigated. The fish was stored at -4.3 ℃ (sample W) or -18 ℃ after three types of low-temperature freezing treatments: pre-frozen to -18 ℃ using a -80 ℃ cryogenic refrigerator (sample L), pre-frozen to -60 ℃ using a -80 ℃ cryogenic refrigerator (sample D), and pre-frozen to -60 ℃ with liquid nitrogen (sample Y). Physicochemical properties such as pH, TVBN, activity of Ca2+-ATPase, TBA value, sensory attributes, and total sulfhydryl and salt-soluble protein content of the fish were then determined. The results showed that with the increase in storage time, pH values of the four samples showed downward trends, while that of the sample W showed an initial drop and then an increase. TVBN and TBA values of the samples increased gradually. After storage for 30 days, the TVBN values of the four samples (W, L, D and Y) reached 14.26 mg/100 g, 7.11 mg/100 g, 6.13 mg/100 g, and 5.53 mg/100 g, respectively; while the salt-soluble protein contents declined to 17.68 mg/g, 28.36 mg/g, 30.01 mg/g, and 32.33 mg/g, respectively. The activity of Ca2+-ATPase, total sulfhydryl content, and sensory assessment values also decreased gradually with the increase in storage time. These results suggest that different pre-freeze conditions had different effects on the quality and flavor of the small yellow croaker during storage.
    38  Quality Analysis of Commercial Roasted Chicken Wing Products
    LI Bian-sheng GU Miao-qing RUAN Zheng GUO Wei-bo LIN Guang-ming YANG Huan-bin
    2015, 31(2):232-239. DOI: 10.13982/j.mfst.1673-9078.2015.2.038
    [Abstract](1275) [HTML](0) [PDF 778.47 K](1506)
    Abstract:
    In order to analyze and quantitatively evaluate the quality of roasted chicken wing products, eight brands of commercial roasted chicken wing products were evaluated for their quality, sensory, and safety indexes. Principal component analysis (PCA) was used to establish a comprehensive evaluation model with 12 indexes including water content, hardness, and chromatic aberration. The final comprehensive score of each brand was obtained by PCA and safety indexes. The results showed that there were different degrees of variation in quality indexes between the brands. No. 7 obtained the highest sensory score, but its total bacterial count exceeded the national standard. There were various degrees of correlations between the different indexes. Water activity had positive correlations with water content, hardness, chewiness, shearing force, and total sugar content, and had negative correlations with the L* and b* value. The first two principal components, with an accumulative variance contribution of 88.00%, were extracted based on PCA. From the results of PCA and safety evaluation, among eight brands of commercial roasted chicken wings, No. 1 had the highest comprehensive score, followed by No. 5, No. 2, No. 3, No. 8, No. 6, No. 4, and No. 7. The comprehensive evaluation method set up in this paper can be used to quantify and rank the quality of roasted chicken wing products and offer a more scientific and intuitive foundation for quality evaluation.
    39  Comparison of Volatile Components in Tea Blossom Obtained by Supercritical CO2, Subcritical CO2, and Petroleum Ether Extractions
    WANG Juan YU Rui ZHANG Jun-yan MA Yu-rong HUANG Hui-hua
    2015, 31(2):240-248. DOI: 10.13982/j.mfst.1673-9078.2015.2.039
    [Abstract](1183) [HTML](0) [PDF 662.89 K](1242)
    Abstract:
    The volatile components of tea blossom were extracted by supercritical CO2, subcritical CO2, and petroleum ether medium extractions. Gas chromatography-mass spectrometry was applied to isolate and identify the volatile components in the three extracts. Principal component analysis, using the SPSS software, was adopted to analyze and compare the main flavors of the three extracts. Results showed that there were, in total, 58 volatile components in tea blossom. Of these, 55, 50, and 54 components were identified in the supercritical CO2, subcritical CO2, and petroleum ether extracts, respectively. They included 17 fatty hydrocarbons and aromatic hydrocarbons, 4 terpenes, 6 terpenols and terpenones, 4 aromatic alcohols and aromatic ketones, 2 aliphatic alcohols, 6 aliphatic ketones, 2 aldehydes, 5 esters, and 7 acids. The major volatile compounds of tea blossom included 2-hydroxy-2-phenylacetophenone (11.04, 10.23, and 8.41 μg/g, respectively, in the supercritical CO2, subcritical CO2, and petroleum ether extracts; same below), phenethylol (11.49, 9.98, and 8.52 μg/g), α-phenethylol (13.91, 12.30, 9.72 μg/g), linalool oxide (5.34, 6.35, and 4.38 μg/g), benzyl alcohol (6.60, 5.34, and 4.43 μg/g), 1,8-dimethyl-4-isopropyl-8,9- epoxy theaspirone (3.68, 2.37, and 1.61 μg/g), and β-ionone (2.67, 1.76, and 1.16 μg/g). The two principal components were deduced based on an analysis by SPSS. The fragrances of the supercritical CO2 extract were found to be richer than those of the subcritical CO2 and petroleum ether extracts
    40  Analysis of Changes in Volatile Components of Salmon Fillets during Refrigerated Storage by the HS-SPME-GC-MS Technique Combined with Electronic Nose
    LI Ting-ting DING Ting ZOU Zhao-yang ZHOU Kai ZHAO Guo-hua LI Jian-rong
    2015, 31(2):249-260. DOI: 10.13982/j.mfst.1673-9078.2015.2.040
    [Abstract](1290) [HTML](0) [PDF 1.15 M](1622)
    Abstract:
    The volatile components of salmon fillets were determined using headspace solid-phase microextraction gas chromatography- mass spectrometry (HS-SPME/GC-MS) combined with the electronic nose technique, and the changes of volatile components during storage at 4 ℃ were also explored. The results showed that the 288 types of volatile components determined by HS-SPME/GC-MS mainly consisted of aldehydes, alcohols, and hydrocarbons (alkanes, alkenes, and aromatics). Additionally, during cold storage, the volatile aldehyde content of salmon fillets decreased continuously, acids showed an increasing trend, and alcohols and aromatics showed a decreasing trend after initial increase. The maximum peak area value of the hydrocarbons appeared on day 12; esters appeared after day 6 with an increasing trend; the contents of amines and other components fluctuated greatly during cold storage. The volatile components of cold-stored salmon fillets, detected by electronic nose, were analyzed by principal component analysis (PCA), loading analysis (LA), and linear discriminant analysis (LDA). The obtained results were consistent with the results of the HS-SPME-GC-MS method, indicating that significant changes in volatile components took place on days 6, 12, and 15, which were the inflection points of the freshness of salmon fillets during refrigerated storage.
    41  Identification of Wine of Origins Using Rare Earth Element Fingerprinting
    ZHAO Fang LIN Li SUN Xiang-yu MAO Wen-hua SUN Yu-qiang ZHAN Ji-cheng
    2015, 31(2):261-267. DOI: 10.13982/j.mfst.1673-9078.2015.2.041
    [Abstract](1373) [HTML](0) [PDF 698.21 K](1326)
    Abstract:
    In this study, in order to explore the feasibility of using rare earth element fingerprinting to identify wine of origins, inductively coupled plasma-mass spectrometry (ICP-MS) was employed to measure the contents of 15 rare earth elements in 228 wine samples from three origins. The data were analyzed by correlation analysis, analysis of variance (ANOVA), and discriminant analysis. The wine of origin was significantly correlated with the rare earth element contents (p < 0.01), while the rare earth element contents were significantly different for the three origins (p < 0.001). The highest rare earth element content was found in the wines from Tonghua, followed by wines from the eastern foot of the Helan Mountains, and the lowest was found in the wines from Shacheng. The cross-validated accuracy rates of the wines from Shacheng, the eastern foot of the Helan Mountains, and Tonghua, using Fisher linear discriminant analysis (FLD), were 92.98%, 98.25%, and 100.00%, respectively, while the accuracy rates by external validation were 84.21%, 89.47%, and 100.00%, respectively. The discrimination capacity of partial least squares discriminant analysis (PLS-DA) was slightly lower; the cross-validated accuracy rates of the three wine origins were 82.46%, 98.25%, and 91.23%, respectively, while the accuracy rates by external validation were 73.68%, 84.21%, and 100.00%, respectively. Therefore, it is possible to identify wine of origins by rare earth element fingerprinting and multivariate statistical analysis.
    42  Rapid Detection of Acrylamide in Fried Food by Nanotechnology-based Hemoglobin Biosensor
    FEI Yong-le WANG Li-ran LI Shu-guo
    2015, 31(2):268-273. DOI: 10.13982/j.mfst.1673-9078.2015.2.042
    [Abstract](1062) [HTML](0) [PDF 787.88 K](1021)
    Abstract:
    Acrylamide is a neurotoxin and a potential carcinogen. Hemoglobin (Hb) biosensor passivation can be achieved by the formation of a covalent compound by acrylamide with the -NH2 group of the N-terminal valine of hemoglobin. Different concentrations of acrylamide produce different degrees of passivation. Based on this principle, hemoglobin biosensors were prepared by immobilizing multi-wall carbon nanotubes (MWCNTs) and Hb in a chitosan film on the surface of glassy carbon electrodes and these were used for the detection of acrylamide in fried food. The optimum analysis conditions for the detection of acrylamide in fried food by differential pulse voltammetry (DPV) was determined as follows: pulse increment 0.008 V, pulse amplitude 0.05 V, pulse width 0.1 V, pulse interval 0.1 s. The oxidative-reductive detector consisted of 10 μg/cm2 MWCNTs and the supporting electrolytes were 0.1 mol/L PBS (pH 7.4), 0.1 mol/L NaCl and 5×10-3 mol/L potassium ferrocyanide. The linear range of response was from 3.0×10-8 mol/L to 3.0×10-7 mol/L and the detection limit was estimated as 1.2×10-8 mol/L, taking into account a signal-to-noise ratio of 3. The developed method is practical in the determination of acrylamide in fried foods, with the advantages of simplicity, rapidity, sensitivity, and accuracy over the standard high-pressure liquid chromatography method.
    43  Determination of Potato Chymotrypsin Inhibitor Activity
    ZENG Fan-kui ZHOU Tian-hong KANG Ke-gui LIU Gang
    2015, 31(2):274-279. DOI: 10.13982/j.mfst.1673-9078.2015.2.043
    [Abstract](1025) [HTML](0) [PDF 619.27 K](1104)
    Abstract:
    Determination of chymotrypsin inhibitor activity is very important for the study of proteins in potato tubers, particularly for protein separation and purification. In this study, a method to evaluate the activity of a potato-derived chymotrypsin inhibitor was explored. This method was based on the spectrophotometric determination (275 nm) of the hydrolysis products of casein that were produced by a specific concentration of chymotrypsin, in the presence or absence of the inhibitor. The results showed that the chymotrypsin inhibitor activity of a crude protein solution extracted from potato tubers was 98.31 CUI/mg (82.11 μg/mg). In other words, each milligram of chymotrypsin inhibitor inhibited 82.11 μg chymotrypsin. Theoretically, the chymotrypsin inhibitor content in 100 g potato tubers can inhibit the activity of 147.43 mg chymotrypsin. Thus, this method is suitable to determine the activity of chymotrypsin inhibitors from potatoes and other sources.
    44  Determination of Selenium Species in Genetically Modified Soybean by High-Performance Liquid Chromatography with Inductively Coupled Plasma Mass Spectrometry
    YANG Xiu-bin WANG Bing-tao YU Kun YAN Zhi LIN Qi-hui ZHAO Qiong-hui LIN Yan-kui WANG Chao
    2015, 31(2):280-284. DOI: 10.13982/j.mfst.1673-9078.2015.2.044
    [Abstract](1672) [HTML](0) [PDF 646.46 K](1318)
    Abstract:
    An analytical method to detect selenium species such as selenate [Se(IV)], selenite [Se(VI)], selenomethionine (SeMet), selenocystine (SeCys2), and selenoethionine (SeEt) in genetically modified soybean was established using high-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS). The effects of the chromatographic column, mobile phase, and acidity on separation were evaluated. Hamilton PRP X-100 reversed phase anion exchange column with 10 mmol/L citric acid solution as the mobile phase was used for separation. Collision cell technology was adopted to eliminate the interference of polyatomic ions such as 40Ar40Ar+ and 40Ar2H2+. Isotope 82Se was detected by ICP-MS. The five species were completely separated within 21 min. The extraction procedure was discussed and optimized. A spiked recovery experiment was carried out with proteinase extration, using genetically modified soybean imported from the USA. The result showed that the recoveries were around 100% for Se(IV) and Se(VI), was in the range 92.6%–109.3% for SeMet, and they were in the range 81.2%–95.9% for SeCys2 and SeEt. This method can be used for the quantitative determination of selenium species in genetically modified soybeans.
    45  Analysis of Umami Components in Sweet Bean Sauce
    HUANG Ming-quan WANG Lu ZHANG Jing-lin SUN Bao-guo
    2015, 31(2):285-293. DOI: 10.13982/j.mfst.1673-9078.2015.2.045
    [Abstract](1190) [HTML](0) [PDF 960.75 K](1227)
    Abstract:
    The methods described in GB/T were used to measure the moisture, crude fat, total nitrogen, and crude protein contents in seven commercially available samples of sweet bean sauce. An automatic amino acid analyzer and high performance liquid chromatography were employed to analyze the free amino acids and nucleotides in the sweet bean sauces, respectively. The molecular weight distribution of small peptides in the sweet bean sauces was determined by size exclusion chromatography (SEC), and the degree of hydrolysis, average peptide chain length, and taste activity value (TAV) of amino acids in sweet bean sauce, as well as their contributions to the taste were calculated and analyzed. The experimental results showed that the moisture, crude fat, total nitrogen, and crude protein contents in seven commercially available samples of sweet bean sauce were 51.42%, 1.84%, 1.284%, and 7.32%, respectively. The total free amino acid contents in the seven pastes ranged from 1.55~2.78 g/100 g, and the most abundant amino acids were proline, glutamic acid, leucine, and aspartic acid. Among them, glutamic acid had the highest TAV (7.00-25.67) and had an important contribution to the taste of umami. Hypoxanthine (Hx) was the dominant nucleotide in sweet bean sauce (3.19~4.87 mg/100 g), but did not have a direct impact on the taste (TAV < 0.5). The small peptide content in sweet bean sauce was in the range of 0.55~3.31 g/100 g; the average peptide chain length (PCL) was between 2 and 4, and the molecular weight distribution was in the range of 221~445 u. Additionally, these small peptides contributed to the taste of umami to some extent.

    Editor in chief:李琳

    Inauguration:现代食品科技

    International standard number:ISSN 1673-9078

    Unified domestic issue:CN 44-1620/TS

    Domestic postal code:46-349

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