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15 October 2016, Volume 37 Issue 19
Basic Research
Effects of Fast Freezing on the Quality and Microstructure of Beef
FENG Xianchao, ZHOU Guanghong
2016, 37(19):  1-7.  doi:10.7506/spkx1002-6630-201619001
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This study investigated and compared meat color, thawing loss, cooking loss, and shear force of beef subjected
to normal freezing and quick freezing. The microstructure of frozen beef was also studied by HE staining, scanning electron
microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the H value of bovine tendon
muscle subjected to quick freezing-thawing process rose by only 0.9%, compared to as high as 9.4% for the normally
frozen and thawed sample, suggesting a significant difference between both freezing methods (P < 0.05). Thawing loss of
beef tendon muscle subjected to normal freezing was significantly higher than that of the sample subjected to fast freezing
(P < 0.01). At the same time, cooking loss of beef tendon muscle subjected to normal freezing was also significantly higher
than that of the samples subjected to fast freezing (P < 0.05). In addition, shear force of beef tendon muscle subjected to normal
freezing was lower but not significantly than that of the quick-frozen and control groups. Electron microscopy results showed
that normal freezing could result in noticeably bigger intermuscular gap and larger intermyofibrillar space in thawed beef when
compared with fast freezing, and it also destroyed the cross-sectional area of muscle fibers. On the other hand, fast freezing could
protect the bright color of beef and improve its eating quality. In addition, fast freezing could greatly reduce the size of ice crystals
in meat, protect the microstructure of meat, and optimize the taste of meat.

Effects of Heat Treatment on Properties of Soybean Oil Body Emulsion
DING Jian, ZHANG Qiaozhi, HAN Tianxiang, SUI Xiaonan, DONG Jixuan, LI Yang
2016, 37(19):  8-15.  doi:10.7506/spkx1002-6630-201619002
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In this study, soybean oil body emulsion was subjected to heat treatment at different temperatures. The changes in
physical stability, oxidative stability, the secondary structures of oleosins, interfacial tension, and interfacial characteristics in
the oil body emulsion were examined using dynamic surface tension measurement, dynamic laser light scattering, confocal
laser technology and circular dichroism to evaluate the effectiveness of heat treatment. The results showed that heat treatment
reduced surface charges and interfacial tension, and changed the interfacial strength of oil bodies. In addition, heat treatment
caused a decrease in α-helix structure from (17.71 ± 0.01)% to (15.3 ± 0.03)%, unordered structure from (29.96 ± 0.01)% to
(27.3 ± 0.06)% and β-turn from (22.34 ± 0.05)% to (21.2 ± 0.03)%, and it could increase β-sheet structure from (29.89 ± 0.06)%
to (36.1 ± 0.02)%. Heat treatment changed the forces maintaining the secondary structure of oleosins, which in turn could affect
the secondary structure contents and resulted in different interfacial properties. Furthermore, heat treatment could not significantly
promote the flocculation of oil bodies; heat treatment at 30 ℃ and 50 ℃ had relatively small amount of hydrogen peroxide. This
result suggested that heat treatment changed the interfacial properties of soybean oil body emulsion and consequently had an
important impact on its physical properties and oxidative stability.

Effect of Wheat Dietary Fibers on Functional Properties of Pork Myofibrillar Protein Gels
LIU Yingli, XIE Liangxu, DING Li, ZHANG Huijuan, GONG Lingxiao, WANG Jing, JIANG Guoqing
2016, 37(19):  15-23.  doi:10.7506/spkx1002-6630-201619003
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In order to develop healthy meat products with low fat and high fiber and to clearly define the effect of dietary
fiber on the quality of meat products, we investigate properties of heat-induced gels of pork myofibrillar protein (MP) as
well as examined the influence of adding wheat bran dietary fibers to heat-induced MP gels on their properties using the
one-factor-at-a-time method. The results showed that the denaturation temperature of MP ranged from 40 to 70 ℃. With
the increase in protein concentration, the water-holding capacity (WHC) and gel hardness increased to reach a plateau at
70 mg/mL. At pH 5.5, the heat-induced gel showed the maximum hardness, and WHC tended to be stable at pH 7.0. Both gel
hardness and WHC showed a stable trend at the ionic strength of 0.6 mol/L. Meanwhile, the emulsifying capacity of MP was
increased but not significantly with increasing addition of wheat bran dietary fibers, showing an increase of 7.4% at an added
concentration of 5%, whereas emulsion stability decreased. Moreover, the elastic modulus, hardness and WHC of heatinduced
MP gels were enhanced. The gel hardness and WHC reached a plateau with the addition of 4% of wheat bran dietary
fibers. Gel microstructure became more loose with enlarged pore size as observed under scanning electron microscope (SEM).
By adding dietary fibers with smaller particle size, the WHC and hardness of gels became stronger, microscopic structure
became more compact, a the value of elastic modulus became smaller. In conclusion, dietary fiber can obviously change
the functional properties of myofibrillar proteins. The addition of the right amount of dietary fiber in meat products can
significantly improve meat flavor as a substitute for fat to reduce energy intake.

Effect of Different Cooking Methods on the Quality of Lamb Meat
REN Guoyan, CAO Li, WANG Yuqin, GUO Jinying, SONG Ya, KANG Huaibin, CUI Guoting, WU Ying, HAN Shuyu
2016, 37(19):  24-30.  doi:10.7506/spkx1002-6630-201619004
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This work studied the effect of different cooking methods (boiling, grilling and roasting) on lamb meat quality.
The compositions and contents of amino acids, fatty acids, and nucleotides, texture indices and muscle microstructure of
fresh and cooked meat samples were detected. Results showed that boiling resulted in the minimum cooking loss and had
the lowest effect on the compositions and contents of amino acids, fatty acids and nucleotides in lamb meat. The amino acid
pattern and fatty acid pattern of lamb meat were changed to different degree during cooking. The flavor amino acid content
in grilled lamb meat was 55.33%, which was significantly higher than that of the boiled (50.67%) and roasted samples
(49.33%). The flavor nucleotide content in roasted lamb meat was the lowest. Fatty acid composition and contents in boiled,
grilled and roasted lamb meat were different but not significantly. The chewiness of grilled lamb meat was better than that
of the boiled and grilled samples. Muscle fiber bundles, the perimysium and intermuscular fat in roasted lamb meat were
damaged most seriously.

Preparation of Magnetic Fe3O4 Nanoparticles Loading Peptides Derived from Enzymatic Hydrolysis of Hairtail Waste Proteins and Its Effect on Membrane Fluidity in CW-2 Cells
SHI Yunjie, LIN Huimin, JIN Tunan, DENG Shanggui
2016, 37(19):  31-35.  doi:10.7506/spkx1002-6630-201619005
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Objective: To prepare magnetic Fe3O4 nanoparticles loading peptides derived from enzymatic hydrolysis of
hairtail processing waste proteins and explore its effect on membrane fluidity in CW-2 cells. Methods: The target product
was synthesized by co-precipitation method, and its structure characteristics and particle size distribution were observed with
X-ray diffraction (XRD), transmission electron microscope (TEM) and atomic force microscope (AFM). Meanwhile, its effect
on membrane fluidity in human colon cancer CW-2 cells was explored by fluorescence polarization in a non-magnetic field
and an alternating magnetic field. Results: Magnetic Fe3O4 nanoparticles loading hairtail peptides were uniformly distributed
with a size of approximately 10 nm and they were found to adhere to each other to form intertwined curves. Compared
with the single magnetic Fe3O4 particles, loading of hairtail peptides enhanced dispersion stability of magnetic nano-Fe3O4
particles. The optimum pH for magnetic Fe3O4 nanoparticles loading hairtail peptides was 6.5–9.0. Cell membrane fluidity
tests showed that P and η values in the experimental group were significantly reduced after 24 h of alternating magnetic field
exposure, indicating that the magnetic Fe3O4 nanoparticles loading hairtail peptides could increase cell membrane fluidity.
Conclusion: Magnetic Fe3O4 nanoparticles loading hairtail peptides can enhance the anti-tumor activity of hairtail peptides in
an alternating magnetic field.

Ion Chromatography Studies of Dynamic Hydrolysis of Added Polyphosphates in Muscle
XU Meng, LIU Wei, ZHOU Li, MA Zhifang, PENG Zengqi
2016, 37(19):  36-41.  doi:10.7506/spkx1002-6630-201619006
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Polyphosphates are commonly used in meat processing as food additives. Once added into meat, they are
hydrolyzed continuously by endogenous polyphosphatases present in meat. In this study, ion chromatography was used to
detect the hydrolysis process of added tetrasodium pyrophosphate (TSPP), sodium tripolyphosphate (STPP) and composite
polyphosphate (m (TSPP) : m (STPP): m (sodium hexametaphosphate) = 3:4:3) in pork longissimus dorsi, fish dorsal muscle
and chicken breast muscle. Inconsistent results were obtained for the hydrolysis of added polyphosphates in muscle from
different animal species. The hydrolysis rate of TSPP in chicken breast muscle was the highest, and TSPP was hydrolyzed
completely within 0.8 h. More TSPP in pork longissimus dorsi was hydrolyzed than in fish dorsal muscle. In addition, STPP
and composite polyphosphate were hydrolyzed fastest upon addition of either of them to pork longissimus dorsi, followed
by addition to chicken breast muscle, and the slowest hydrolysis rate was observed upon addition to fish dorsal muscle. This
study can provide the theoretical basis for regulating the hydrolysis process of polyphosphates and accordingly provide a
guide to the reasonable addition of polyphosphates into muscle from different species.

Effect of Microwave Treatment on Functional Properties of Soybean Isolate Protein-Phospholipid System
LI Qiuhui, LI Yang, SUI Xiaonan, WANG Zhongjiang, QI Baokun, JIANG Lianzhou
2016, 37(19):  42-47.  doi:10.7506/spkx1002-6630-201619007
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This research studied the effect of different microwave power levels on foaming, emulsifying and gel properties
of soybean protein isolate-phospholipid system by measuring foaming activity, foam stability, emulsifying activity, emulsion
stability, flocculation index, creaming index, water retention and gel texture, as well as by examining gel microstructure
under scanning electron microscope. The results showed that foaming activity, emulsifying capacity and gel properties
were increased at first and then decreased with microwave power. In addition, when the microwave power was 900 W, the
composite system exhibited the best foaming properties and emulsifying properties; at 1 100 W microwave power, the gel
properties were improved significantly when compared with the control sample, indicating that microwave could promote the
formation of soybean protein isolate-phospholipid system at the water/oil interface and that structural changes of the protein
could improve gel properties of the composite system.

Preparation, Characterization and Activity Analysis of Selenium-Containing Pumpkin Polysaccharide
SHANG Longchen, WU Shaowei, ZHANG Chi, LIAO Honghua, LIU Xinping
2016, 37(19):  48-53.  doi:10.7506/spkx1002-6630-201619008
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Objective: To investigate selenium modification of pumpkin polysaccharide and to evaluate the in vitro
antioxidant activity and antitumor effect against human breast cancer MDA-MB-231 cells of the modified polysaccharide.
Methods: Pumpkin polysaccharide was prepared and purified and it was modified by reaction with Na2SeO3 to obtain
selenium-containing polysaccharide. Furthermore, the structure of the modified polysaccharide was characterized through
UV, IR, atomic fluorescence spectroscopies and thermogravimetric analysis. Finally, its scavenging effect on O2-· and
·OH as well as growth inhibitory effect on breast cancer cells were tested by using pyrogallol autoxidation, salicylic
acid method and methyl thiazolyl tetrazolium colorimetric assay. Results: Se=O and Se–C bonds were observed in the
structure of the target product, thus successfully achieving the selenium modification of pumpkin polysaccharide. The
selenium-containing pumpkin polysaccharide had significantly stronger scavenging effects on O2-· and ·OH than ordinary
pumpkin polysaccharide, which were concentration-dependent. Meanwhile, the modified polysaccharide also inhibited the
growth of human breast cancer cells in a dose-dependent manner more significantly than did the unmodified one.

Interactions between Konjac Glucomannan and Curdlan
JIANG Mingfeng, XIAO Man, NI Xuewen, YAN Wenli, KUANG Ying, SHEN Yue, JIANG Fatang
2016, 37(19):  54-58.  doi:10.7506/spkx1002-6630-201619009
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The interaction between konjac glucomannan (KGM) and curdlan was evaluated by molecular dynamic simulation.
The viscosity and shear stress of KGM/curdlan sol were measured as a function of shear rate by a rotational rheometer at
25 ℃. The molecular morphology of KGM and curdlan in water solution were observed by transmission electron microscopy
(TEM) and atomic force microscopy (AFM). The results of molecular dynamic simulation and rheological behavior showed
that hydrogen bond interactions existed between KGM and curdlan. The collaborative stress index increased from 1.43 to 1.97,
suggesting KGM/curdlan sol has synergistic viscosification due to the interactions between KGM and curdlan. TEM and
AFM results showed the formation of interpenetrating network structure between KGM and curdlan, which may be driven
by hydrogen bonding interactions, and this interaction was further confirmed by the microscopic level.

Preparation and Properties of Edible Amino Acid-Modified Biofilm Carrier
SUN Ye, WANG Yanping, LI Shuya, LIU Zhaoxian, LIU Yuan
2016, 37(19):  59-63.  doi:10.7506/spkx1002-6630-201619010
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In order to expand the application of lactic acid bacterial biofilm in the food industry and construct edible
functional carrier, amino acids which could be used as ligands for bacterial adhesion were modified onto alginate in this
study. The structures, compositions, electrical properties and hydrophilicity of the modified carriers (Alg-Arg and Alg-Lys)
were characterized by nuclear magnetic resonance, amino acid content analysis, and ζ potential and water contact angle
measurement. Lactobacillus kefiranofaciens ZW3 was cultured on the carriers to investigate its growth and extracellular
exopolysaccharide secretion. The results showed that after cultivation for 4 d, the amount of ZW3 on Alg-Arg reached up to
3.8 × 107 CFU/cm2, which was 3.5 times as high as that on Alg-Lys. The secretion amount of extracellular exopolysaccharide
was 28.2 μg/cm2, which was increased by 2.4 times in comparison with that on Alg-Lys. Compared with lysine-modified
carrier, arginine-modified carrier was better for ZW3 growth and the secretion of extracellular exopolysaccharide. These
results demonstrated that biofilm formation could be enhanced by the appropriate ligand.

Mass Spectrometry-Based Analysis of Digestive Stability of Target Protein in Genetically Modified Organism
MAO Jie, SUN Xing, CHENG Juanxian, WANG Xinzheng, ZHAO Yongqiang, WANG Hongxia, HE Kun, XIA Qing
2016, 37(19):  64-69.  doi:10.7506/spkx1002-6630-201619011
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Digestive stability analysis of exogenous protein is one of the important indexes of genetically modified organisms
(GMO) safety assessment. In the present study, we established a novel assessment assay for protein digestive stability based
on label-free quantification of mass spectrometry using bovine β-lacto globulin (BLG), bovine serum albumin (BSA) and
soybean trypsin inhibitor (STI) as standard proteins. Protein samples were treated with simulated gastric/intestinal fluids
(SGF/SIF), and then separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The target bands were then
cut out and trypsinized. The extracted peptides were analyzed by nano liquid chromatography-electronic spray ion-mass
spectrum/mass spectrum and identified by Mascot software. By calculating the ratio between the matched peptide numbers
of the target protein before and after SGF/SIF treatment, the digestibility of the target protein was estimated. When the ratio
was lower than 0.50, the target protein was considered digestible. This newly developed assay was applied to Cry1Ab/1Ac,
the exogenous protein of the genetically modified rice ‘Huahui No. 1’. The results showed that the ratio was lower than 0.50
after digestion in SGF for 2 minutes, while it decreased to less than 0.50 after digestion in SIF for 15 seconds, indicating that it
is very liable to be digested. Our study provides a novel MS-based method for digestive stability analysis of target proteins from
genetically modified organisms, which is easy to operate with no need for specific antibody.

Correlation among Cell Wall Components, Related Enzyme Activities and Texture of Developing Fruits of Different Apple (Malus × domestica) Cultivars
GAO Ziyi, FAN Xianguang, YANG Huijuan, JIANG Xiaobing, YANG Yazhou, ZHAO Zhengyang, DANG Zhihong
2016, 37(19):  70-75.  doi:10.7506/spkx1002-6630-201619012
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Apple texture is one of the most important quality properties that influences consumers’ acceptability of this
fruit. To evaluate the determinant factor for texture difference in apple fruits, the changes in firmness, crispness, cell wall
components and related enzyme activities in fruits of 4 apple cultivars with different textures were monitored during
fruit growth and ripening in this study. The results suggested that fruit crispness slightly increased whil firmness and the
contents of cell wall components in the 4 apple cultivars showed a decreasing tendency during fruit development. During
fruit ripening, the content of water-soluble pectin (WSP) in the crisp fruit cultivars was higher, while cellulose content
was obviously lower. The activities of polygalacronase (PG) and β-galactosidase were higher in the apple cultivars with
higher crispness ‘Honeycrisp’ and ‘Gala’, but the activities of carboxymethycellulase and pectinmethylesterase disclosed no
significant difference among all cultivars. Therefore, it was proposed that apple texture differed greatly due to variations in
WSP, ionic soluble pectin and cellulose contents as well as PG and β-galactosidase activities.

Physicochemical Properties and Digestibility of Proso Millet Starch
ZHANG Lizhen, JI Peishuang, LUO Xuxiao, MU Hongzhang, QIN Yanpeng, NIU Yu, QIAO Zhijun
2016, 37(19):  76-81.  doi:10.7506/spkx1002-6630-201619013
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In this experiment, glutinous and nonglutinous proso millet starch were prepared from glutinous and nonglutinous
proso millet flour by an alkaline method and their granule morphology, infrared spectral characteristics, transmittance,
solubility, water-holding capacity, retrogradation stability and digestibility were explored. The results showed that the
amylopectin content was 91.78% and amylose content was 8.21% in glutinous proso millet starch. The amylopectin content
was 65.28% and amylose content was 34.72% in nonglutinous proso millet starch. The contents of resistant starch in
nonglutinous proso millet flour and starch were higher than those in nonglutinous proso millet flour and starch, and all four
values were over 50%. Glutinous proso millet starch showed better transparency and weaker retrogradation stability than
did nonglutinous proso millet starch. Water-holding capacity and solubility of both glutinous and nonglutinous proso millet
starch showed an upward trend with increasing temperature.

Identification and Comparative Analysis of Antioxidant Ability of Anthocyanins in Lonicera caerulea Berry Extracts
AN Xiaoqi, WANG Yuehua, MENG Xianjun
2016, 37(19):  82-87.  doi:10.7506/spkx1002-6630-201619014
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The identification of anthocyanins composition and antioxidant activity of Lonicera caerulea berry extracts
was investigated in this study. ‘Beilei’ L. caerulea berries were ultrasonically extracted with 60% ethanol containing 0.1%
HCl for 90 min. D101 macroporous resin was used to purify the obtained extracts. After that, freeze drying was conducted
to obtain powder. The contents of total anthocyanins and polyphenols were determined using pH differential and Folinreagent
method as (353.35 ± 0.79) mg/g and (474.01 ± 2.12) mg/g, respectively. High performance liquid chromatographytandem
mass spectrometry (HPLC-MS/MS) was used for the identification of anthocyanin composition. A total of 11
individual anthocyanins were found with cyanidin-3-glucoside (90.679%) being the major anthocyanin. Additionally, total
antioxidant capacity (T-AOC) and 2,2’-azinobis(3-ethylbenzothiazoline-6-sulphonate) radical (ABTS+·), 1,1- diphenyl-
2-picrylhydrazyl (DPPH) radical scavenging activities of L. caerulea berry extracts, cyanidin-3-glucoside and VC were
comparatively analyzed, and the results revealed a decreasing order of cyanidin-3-glucoside > L. caerulea berry extract > VC.

Antioxidant Activities in Vitro of Different Fruit Parts of Eight Kiwifruit Varieties
ZHANG Ting, LI Chen, LUO Anwei, TANG Miaoling, CHEN Han, LI Xulei, DUAN Lihua
2016, 37(19):  88-93.  doi:10.7506/spkx1002-6630-201619015
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In order to extend the utilization of kiwifruits, we determined and correlated physicochemical parameters and
antioxidant activities (DPPH, ·OH, and ABTS+·scavenging capacity and Cu2+ and Fe3+-reducing power) of different fruit
parts of 8 commercial varieties of kiwifruit. In addition, the contents of antioxidant components in fruit peel, pulp and core
were evaluated and the contribution rates of different parts to the antioxidant activities of the whole fruit were also explored.
Among 8 varieties of kiwifruits, the “Huayou” cultivar had the strongest antioxidant activity, whereas “Hayward” had the
weakest antioxidant activity. The correlation analysis indicated that ascorbic acid and total phenolic contents significantly
contributed to the antioxidant activities. The decreasing order of antioxidant activities of different fruit parts was as follows:
peel, pulp and core. The antioxidant activity of the peel was mainly derived from the rich contents of phenolic compounds,
while the antioxidant activity of the pulp was mainly derived from the plenty of ascorbic acid.

Degradation Kinetics of Pigments from Lycium ruthenicum in Aqueous Solution and Screening of Their Color Fixatives
ZHANG Jianqi, YANG Wenyu, SHI Dongjun, TANG Sheng, LUO Chunxu
2016, 37(19):  94-99.  doi:10.7506/spkx1002-6630-201619016
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Lycium ruthenicum is widely distributed in the Qinghai-Tibet Plateau, and its fruits are rich in anthocyanins, 80%
of which is petunidin-3-O-rutinoside (trans-p-coumaroyl)-5-O-glucoside, an ortho-diphenolic compound. Considering the
rapid degradation of the purple pigment from Lycium ruthenicu (PLR) in aqueous solution, this work aimed to explore the
degradation mechanism of PLR and to improve its stability. Optimal degradation kinetics and appropriate color fixatives
for PLR were investigated by determining the changes of its UV-Vis absorption spectrum and absorbance at the maximum
wavelength (Aλmax) and fitting the changes in Aλmax to several models. The results indicated that: (1) the degradation of PLR
in aqueous solution followed the Weibull model basically; (2) 0.4–80.0 mg/mL citric acid was beneficial to the stabilization
of PLR while it could change its color from purple to peach; (3) 4.0–80.0 mg/mL ascorbic acid could not prevent the
degradation of PLR, and it changed the degradation kinetics to Baker-Lonsdale model; (4) sodium chloride at higher
concentrations (250.0 mg/mL or above) could have a stabilizing effect on PLR; (5) additives such as calcium or polyols
were not helpful for improving the stability of PLR. It could be supposed that ortho-diphenolic group rather than plant
enzyme could be the main factor responsible for the degradation of PLR, due to slower fading when adding boric acid when
compared with 50% ethanol.

Effect of in Vitro Simulated Digestion on Anthocyanin Composition and Antioxidant Activity of Lonicera caerulea Berry Extracts
WANG Yuehua, LI Bin, MENG Xianjun, AN Xiaoqi, MA Yan, ZHANG Qi, LI Li, LI Dongnan
2016, 37(19):  100-105.  doi:10.7506/spkx1002-6630-201619017
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Changes in total polyphenols and anthocyanins contents, anthocyanin composition and antioxidant capacity of
Lonicera caerulea berry extracts before and after in vitro digestion were investigated. Folin-Ciocalteu and pH differential
methods were used for determining the contents of total polyphenols and anthocyanins, respectively. Anthocyanin
composition was analyzed using HPLC-EIS-MS/MS based on molecular mass and fragment ions, peak sequence and related
literature data. Antioxidant activities of the extracts before and after in vitro digestion were measured using total antioxidant
capacity (T-AOC) and oxygen radical absorbance capacity (ORAC) methods. The results indicated that the content of total
polyphenols increased by 48.2% while anthocyanins decreased by 67.6%. The number of anthocyanins decreased from
11 to 8; additionally, the ORAC and T-AOC values of the extracts decreased by 80.0% and 55.6% after in vitro digestion,
respectively. Taken together, after in vitro digestion, Lonicera caerulea berry extracts had increased total polyphenols,
reduced anthocyanin contents and composition, and lowered antioxidant activity.

Comparison of Thermal Properties of Muscles from Five Kinds of Freshwater Fish
SHAO Ying, WANG Xiaohong, WU Wenjin, LI Xin, XIONG Guangquan, WANG Haibin, QIAO Yu, WANG Jun, LIAO Li, WANG Lan
2016, 37(19):  106-111.  doi:10.7506/spkx1002-6630-201619018
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The study was intended to investigate comparatively the thermal properties of muscles from 5 different freshwater
fish (Megalobrama amblycephala, Ctenopharyngodon idellus, Pelteobagrus fulvidraco, Lateolabras janopicus and Siniperca
chuatsi) by differential scanning calorimetry (DSC), including moisture content, freezing point, denaturation temperature,
denaturation enthalpy and specific heat capacity. Results showed that the freezing points of the five fish ranged from −0.57 to
−0.10 ℃; the onset temperature of decalescence peak around 50 ℃ ranged from 37.00 to 41.57 ℃, the conclusion temperature
ranged from 60.47 to 62.33 ℃, and the denaturation enthalpy ranged from 1.680 0 to 2.499 7 J/g. The onset temperature of
decalescence peak around 70 ℃ ranged from 66.33 to 71.13 ℃, the conclusion temperature ranged from 73.60 to 82.20 ℃, and
the denaturation enthalpy ranged from 0.418 0 to 0.512 2 J/g; the specific heat capacity ranged from 1.658 0 to 3.862 3 J/(g·K).
As demonstrated by this study, among the five species examined, freezing point and moisture content of Megalobrama
amblycephala were relatively lower; denaturation temperature and denaturation enthalpy of Ctenopharyngodon idellus
myosin and Siniperca chuatsi actin were relatively higher, which means that they had higher protein stability. Moreover, the
specific heat capacity of fresh fish was higher than that of frozen fish; the specific heat capacity of processed fish was higher
than that of the unprocessed one.

Relationships between Solvent Retention Capacity of Wheat Flour and Mechanical Properties of Dried Noodles
JIANG Song, JIA Danfeng, WU Juan
2016, 37(19):  112-116.  doi:10.7506/spkx1002-6630-201619019
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Six wheat varieties and lines were used to analyze the relationships between solvent retention capacity (SRC) of
wheat flour and mechanical properties of dried noodles. Meanwhile, the texture quality and cooking characteristics of dried
noodles were tested using a texture analyzer. Results indicated that lactic acid SRC was correlated positively with elasticity
modulus, fracture displacement, fracture stress, hardness and chewiness (r = 0.84–0.92), respectively, while it was correlated
negatively with cooking loss (r = −0.99). Sucrose SRC was significantly correlated with fracture stress (r = 0.84), chewiness
(r = 0.82) and cooking loss (r = −0.83), respectively. Sodium bicarbonate SRC was correlated significantly with cohesiveness
(r = −0.87), springiness (r = −0.85) and water absorption rate of cooked noodles (r = 0.98), respectively. Water SRC was not
correlated significantly with the qualities of noodles. The SRC test could be used as an alternative to the traditional tests of
protein content, wet gluten content, sodium dodecyl sulfate, sodium salt sedimentation value and damaged starch content for
the prediction of mechanical properties of dried noodles.

Bioengineering
Screening of Lactic Acid Bacteria for Inhibiting Oral Streptococcus mutans and Preliminary Study of Antibacterial Mechanism
GUO Xialei, ZHANG Jian, YANG Zhennai
2016, 37(19):  117-122.  doi:10.7506/spkx1002-6630-201619020
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Considering that lactic acid bacteria (LAB) that can inhibit harmful bacteria, LAB strains stored in our laboratory
were screened for inhibiting oral Streptococcus mutans. The screened strains were measured for minimum inhibitory
concentration (MIC) and inhibitory effect on biofilm formation adhesion properties of S. mutans, and the underlying
mechanism was preliminarily studied as well. The results showed that 5 Lactobacillus plantarum strains including K25,
SKT109, YW3-2, YW5-1 and YW1-1 exhibited clear inhibition against S. mutans. Among 4 indicator S. mutans strains,
1.2499 and 1.2500 were more sensitive to L. plantarum. L. plantarum K25 showed stronger inhibition than 4 other strains
against S. mutans. The MIC value (1.25 × 107–2.50 × 107 CFU/mL) of strain K25 was the lowest, the inhibition rate on
biofilm formation of S. mutans was significantly higher, and the inhibitory effect on the adhesion ability of S. mutans was
clear. Preliminary studies on the antibacterial mechanism of L. plantarum K25 indicated that lactic acid and hydrogen
peroxide produced by the strain played major roles in this activity.

Effect of p-Hydroxybenzyl Alcohol on the Biosynthesis of Exopolysaccharide by Submerged Culture of Grifola frondosa and Fermentation Kinetics
ZHU Junjie, WU Tianxiang, WU Caiyun, LIU Xin, ZHAO Qunli
2016, 37(19):  123-127.  doi:10.7506/spkx1002-6630-201619021
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The effect of adding different concentration gradients of p-hydroxybenzyl alcohol to the culture medium of Grifola
frondosa on mycelial growth and the production of extracellular polysaccharide in submerged fermentation. Meanwhile, we
determined changes in mycelial growth, reducing sugar (residual sugar) content, extracellular polysaccharide content, pH,
p-hydroxybenzyl alcohol and gastrodin contents in the fermentation broth of Grifola frondosa, and we also made a dynamic
analysis. Results showed that addition of 200 mg/L p-hydroxybenzyl alcohol was found to be optimal, resulting in an
increase in mycelial biomass of 22.73% and an increase in extracellular polysaccharide production of 10.24% as compared
with the control group without added p-hydroxybenzyl alcohol; both increases were significant (P < 0.05). Dynamic analysis
results showed that the growth of Grifola frondosa remained stable from day 8 onwards; glucose was consumed as the carbon
source, and residual glucose and the production of extracellular polysaccharide both remained stable from day 10 onwards.
In addition, the gastrodin content increased as a result of partial conversion of p-hydroxybenzyl alcohol into gastrodin.

Isolation and Alcohol Fermentation Characteristics of Thermotolerant Yeasts
LIU Chaodi, MIAO Lihong, CHEN Jin, LIU Pulin
2016, 37(19):  128-134.  doi:10.7506/spkx1002-6630-201619022
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In this study, 69 thermotolerant yeast strains were isolated from 29 different soil samples, and the fermentation
performance of these strains at high temperature was also detected. Based on 26S rDNA D1/D2 domain sequence analysis
and physiological characterization, these strains were phylogenetically related to 7 species in 6 genera, including Candida
tropicalis (39.1% of the total yeast strains), K. marxianus (23.4%), I. orientalis (29.7%), M. guilliermondii (1.6%), K. bovina
(1.6%), C. palmioleophila (1.6%) and S. cerevisiae (3.1%). C. tropicalis were the most widely distributed species. The best
thermotolerant and ethanol fermentation ability were detected in K. marxianus. The ethanol production reached up to 6.56%
(V/V) in 72 h at 40 ℃. These results demonstrated that K. marxianus has obvious advantages in ethanol fermentation at high
temperature, which makes it a good potential candidate for commercial biomass ethanol production.

Enhanced Production of Thermomyces lanuginosus Lipase in Pichia pastoris by Codon Optimization and Co-expression of Vitreoscilla Hemoglobin
WANG Jianrong, LIU Danni, XIA Yu, YANG Ling, LIU Jinshan, TANG Ye, CHEN Lizhi, HUANG Jiale, LI Yangyuan
2016, 37(19):  135-140.  doi:10.7506/spkx1002-6630-201619023
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The codon usage of Thermomyces lanuginosus lipase (tll) and Vitreoscilla hemoglobin (vhb) gene were optimized
by online software according to P. pastoris preferred codon usage. The G + C contents of the codon-optimized genes tll-opt
and vhb-opt were increased from 46% to 49% and 42% to 51%, respectively. The nucleotides A, T, C and G dispersed evenly
in the optimized genes, thereby eliminating AT- or GC-rich motifs. The tll and tll-opt genes were ligated into pPICZαA and
transformed into P. pastoris X33, respectively. The recombinant strains containing tll and tll-opt were cultivated in shaking
flask and 50 L bioreactor, respectively. In shake-flask level, the maximum lipase activities of X33/tll and X33/tll-opt were
7 and 16 U/mL, respectively. In 50 L bioreactor, the maximum lipase activities produced by X33/tll and X33/tll-opt were
201 U/mL and 430 U/mL. To further increase the expression of tll-opt, the vhb-opt gene was transformed into the
recombinant strain containing tll-opt to form recombinant strain VHb+. In shake-flask level, the maximum lipase activity
of VHb+ was 23 U/mL, which was 139% and 328% higher than that from the tll-opt gene and the wild-type gene (tll),
respectively. The maximum lipase activity of VHb+ in 50 L bioreactor was 610 U/mL, which was 141% and 303% higher
than that from the tll-opt gene and the wild-type gene (tll).

Cloning, Expression and Identification of Trichoderma viride Cellobiohydrolase Gene in Lactic Acid Bacteria
WANG Cuiyan, WANG Yuhua, PIAO Chunhong, LIU Junmei, HU Yaohui, REN Dayong, YU Hansong
2016, 37(19):  141-146.  doi:10.7506/spkx1002-6630-201619024
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The expression of the cbhⅡ (cellobiohydrolase) gene from Trichoderma viride was studied by using Lactobacillus
expression system. Primers were designed according to T. viride cbhⅡ gene (GenBank accession number: M55080) and
the cbhⅡ gene cDNA was obtained by PCR method with a sequence length of approximately 1 441 bp. An 80 bp signal
peptide sequence was inserted into the upstream gene for the secretory expression of the target protein. Then, the gene was
optimized according to the codon usage of lactic acid bacteria for the synthesis of the whole cbhⅡ gene. The prokaryotic
expression vector pMG36e-S-cbhⅡ was constructed through connection between the target gene and the shuttle vector
pMG36e. Electrotransformation was used to obtain recombinant lactic acid bacteria in competent cells of Lactococcus lactis
NZ3900. The recombinant protein displayed a molecular weight of approximately 53 kD as determined by sodium dodecyl sulfatepolyacrylamide
gel electrophoresis, which is consistent with the expected size. The cellulase activity was 16.7 U/mL in culture
supernatants by 3,5-dinitrosalicylic acid assay, and there was almost no activity in cell lysate precipitates or supernatants.
These results showed that the signal peptide sequence was correctly identified by Lactococcus lactis and extracellular
expression was achieved successfully.

Isolation, Purification and Characterization of Laccase from Pleurotus ostreatus Heterosis-2
LIAO Haijun, LI Ruijia, TAO Min, BAI Yajuan, TANG Jing, TANG Yunming
2016, 37(19):  147-153.  doi:10.7506/spkx1002-6630-201619025
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An electrophoretically pure laccase from the fermentation broth of Pleurotus ostreatus heterosis-2 was obtained
through ammonium sulfate fractionation, DEAE-Sepharose fast flow chromatography and Superdex-200 prep grade
chromatography. The results indicated that the specific activity of the purified enzyme reached 115 U/mg. The relative
molecular weight of the laccase was approximately 244.0 kD, with a subunit molecular mass of roughly 85.6 kD. The
enzymatic properties showed that the optimum pH and temperature for the laccase were 5.0 and 55 ℃, respectively. The
enzyme was stabled at pH 6.0–8.0 and 40–55 ℃, and its apparent Km and vmax were 2.1 mmol/L and 0.117 μmol/(min·L),
respectively. Fe2+ and ascorbic acid could completely inactivate the laccase, whereas the enzyme activity was slightly
affected by EDTA, Ag+, Mg2+ and Li+. Cu2+ had little activating effect on laccase activity. The enzyme activity of laccase
could be activated by urea, ethanol, and isopropanol, and inhibited by oxalic acid, methanol, n-butanol, K+, Ca2+, Ba2+,
Zn2+, Cd2+, Pb2+, Mn2+, and Co2+.

Effect of Fermentation Methods on Sensory and Nutritional Quality of Persimmon Vinegar
LUO Xiuli, YANG Ying, LU Shengmin, ZHANG Chenlei
2016, 37(19):  154-159.  doi:10.7506/spkx1002-6630-201619026
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Two fermentation methods, i.e., static liquid-state fermentation and static solid-state fermentation, were applied
to make persimmon vinegar from ‘Lanxi Red’ persimmon for the purpose of investigating the effects of fermentation
methods on sensory quality, nutrient components, volatile compounds and antioxidant capability in vitro of persimmon
vinegar. Results indicated that persimmon vinegar had rich fragrance, and soft and mellow sourness, and the sensory quality
of vinegar made by static solid-state fermentation was better. Furthermore, the total acidity was up to 6.551 g/100 mL, and
flavones, polyphenol and protein contents were significantly higher than those in static liquid state fermented vinegar and
even persimmon pulp (P < 0.05). The total amino acid content in solid-state fermented persimmon vinegar was 0.778%,
with essential amino acids accounting for 44.47% of the total amino acids, the contents of all amino acids except arginine
were significantly higher than those in liquid-state fermentation. The same tendency was found for volatile components.
The content of ester compounds in solid state fermented samples was higher, especially for ethyl acetate (which showed
an increase of about 10%). The new occurrence of γ-nonanolactone, phenethyl benzoate, β-damascenone and eugenol,
which contributed to special aroma characteristics, was only found in solid-state fermented persimmon vinegar, and these
compounds were together responsible for its unique aroma and flavor. A higher antioxidant capability in vitro was also
found in persimmon vinegar prepared by solid state fermentation, and it was slightly but not significantly lower when
compared with that in the pulp (P > 0.05). From the perspective of both sensory and nutritional quality, the solid static state
fermentation method is more suitable for traditional vinegar manufacturers to produce fruit vinegar.

Screening and Identification of Nitrite-Degrading Lactic Acid Bacteria
WU Huihao, NIU Feng, CHEN Shanshan, ZHONG Qi, XIAO Junchuan
2016, 37(19):  160-165.  doi:10.7506/spkx1002-6630-201619027
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Objective: To screen nitrite-degrading lactic acid bacteria (LAB), and thus to lay a theoretical foundation for
the future development of probiotic lactic acid bacteria. Methods: Totally 13 LAB strains were isolated and purified from
unique local foods and animal intestines, and their nitrite-degrading abilities were evaluated by the naphthyl ethylenediamine
dihydrochloride spectrophotometric method. Biochemical assays and 16S rDNA sequencing were used to identify the lactic
acid bacteria with the highest nitrite-degrading capacity. Results: A nitrite-degrading strain, JS3, was obtained, which was
found to be able to degrade 83.39% nitrite. The optimized culture conditions for enhanced nitrite degradation by the selected
strain were determined as peptone concentration in medium of 15 g/L, inoculum quantity of 5%, and culture at 30 ℃ for
48 h, resulting in a degradation rate as high as 93.47%. The strain had obvious antibacterial activity against Staphylococcus
aureus and Bacillus subtilis. It was identified as Lactobacillus zeae and named L. zeae. JS3. Conclusion: The strain JS3 has
efficient nitrite-degrading capacity, and it is potentially an excellent species for the degradation of nitrite in the future.

Evaluation of Drug-Resistant Phenotypes and Genes in Foodborne Salmonella Isolates
HOU Xuejiao, WU Kemin, MO Guodong, LIU Shuhong, YAN Tianjiu, JIAO Pengtao, WEI Ping
2016, 37(19):  166-170.  doi:10.7506/spkx1002-6630-201619028
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In order to investigate the relationship between drug-resistant phenotypes and genes and explore the mechanism
of drug resistance at the gene level, a total of 215 Salmonella strains isolated from 1 093 retail meat samples were assayed
for antimicrobial susceptibility. Totally 16 pairs of primers were designed to amplify the drug-resistant genes and sequence
homology was detected after T-A cloning. Results indicated that the Salmonella isolates showed the highest resistance
to sulfisoxazole (SIZ) (71.7%), followed by tetracycline (TET) (69.8%), trimethoprim (TMP) (67.9%) and compound
sulfamethoxazole (TSU) (52.8%), and all these isolates were sensitive to ciprofloxacin (CIP), nitrofurantoin (NIT) and
cephalosporin. Approximately 60.5% of these isolates showed resistance to at least 3 kinds of antibiotics, and 4 of them were
even resistant to 13 drugs. Ten drug-resistant genes were detected and they were found to share a homology higher than 99%
with reference sequences. The consistency rates between drug-resistant phenotype and drug-resistant gene for β-lactams and
tetracycline were both higher than 90%, followed by sulfonamides (81.6%). This study demonstrated that the drug resistance
rate of foodborne Salmonella was high and their multi-drug resistance was serious. And the results of detection of drugresistant
phenotypes and drug-resistant genes were consistent.

Isolation, Identification of Bacillus mojavensis amyP216 and Optimization of Its Fermentation Conditions for Enhanced Chitosanase Production
FENG Zhibin, XUE Yu, CHEN Guozhong, ZHANG Juan, LUO Le, CHENG Shiwei
2016, 37(19):  171-176.  doi:10.7506/spkx1002-6630-201619029
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Bacterial strains were isolated from coastal sandy soil collected in Yantai, Shandong province, and were initially
screened to obtain 5 chitosanase-producing strains by transparent circle method. Further secondary screening provided a
strain producing the highest chitosanase activity named amyP216. The strain amyP216 was identified as Bacillus mojavensis
based on morphological, physiological and biochemical characteristics and 16S rDNA sequence analysis. The fermentation
conditions of amyP216 for chitosanase production were optimized by one-factor-at-a-time and orthogonal array designs.
The results showed that the maximum chitosanase activity of 80.60 U/mL, which was increased by 2.2 folds as compared
to that before optimization (36.20 U/mL), was obtained when the fermentation was carried out at 30 ℃ for 45 h in a 5-L
auto-controlled fermentor using optimized culture medium containing 20 g/L colloid chitosan, 12.5 g/L yeast extract
powder and 1.0 g/L Tween-80 at initial pH 6.0. Therefore, the strain amyP216 has potential application in the industrial
production of chitosanase.

Isolation and Identification of Spoilage Yeasts in Foods and Their Spoilage Ability
LU Wenjun, WANG Fang, LU Zhaoxin, Lü Fengxia, ZHAO Haizhen, ZHANG Chong, BIE Xiaomei
2016, 37(19):  177-182.  doi:10.7506/spkx1002-6630-201619030
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According to the method to detect yeasts described in the National Food Safety Standard GB 4789.15?2010, yeasts
from fruit and honey were isolated and identified by sequence analysis of the D1/D2 domain of 26S rDNA. From honey,
strawberries, bananas, oranges, nectarines and mangoes, a total of 3 Citeromyces matritensis strains, 3 Wickerhamomyces
anomalus strains, 12 Meyerozyma guilliermondii strains, 1 Lodderomyces elongisporus strain, 2 Hanseniaspora uvarum
strains and 1 Metschnikowia reukaufii strain were isolated. Each of these yeasts was inoculated on apples, nectarines and
bananas to evaluate their spoilage ability in comparison with blank control based on how fast the inoculated samples spoiled.
We determined W. anomalusand and C. matritensisare to be the major spoilage yeasts of fruits and honey. Moreover,
M. reukaufiicauses could result in strong putrefaction on nectarines and M. guilliermondiidoes was obviously active in
causing spoilage of bananas. By strengthening the detection and control of these yeasts, we can prevent them from causing
hazards to the food industry better.

Identification of Specific Spoilage Organisms in Whitefish at Room Temperature
XIA Xiudong, LIU Xiaoli, WANG Ying, LI Ying, HUANG Zisu, JIA Yangyang, DONG Mingsheng, ZHOU Jianzhong
2016, 37(19):  183-189.  doi:10.7506/spkx1002-6630-201619031
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Sensory quality, total volatile base nitrogen (TVBN) value, the growth of spoilage bacteria and pH in sterile
whitefish blocks (as control, CK) and those inoculated with different spoilage bacteria were analyzed, and growth kinetic
parameters of spoilage bacteria and the yield factor for TVBN production (YTVBN/CFU) were used for quantitative measurements
of microbial spoilage to identify the specific spoilage organism (SSO) of whitefish at room temperature. The results showed
that the whitefish blocks inoculated with Morganella sp.wf-1 reached the limit (15.16 h) of sensory acceptability earlier
than CK and whitefish inoculated with Staphylococcus sp.wf-1, Morganella sp.wf-1, Morganella sp.wf-2, Proteus sp.wf-1,
Proteus sp.wf-2 and Proteus sp.wf-3, and TVBN value and total bacterial count were 29.98 mg/100 g and 7.53 (lg(CFU/g))
at this time point, respectively. The analysis of growth kinetic parameters and YTVBN/CFU for these spoilage organisms showed
that Morganella sp.wf-1 had the shortest lag phase of growth, maximum specific growth rate and YTVBN/CFU, which were 2.60 h,
0.304 6 h-1 and 6.27 × 10-9 mg TVBN/CFU, respectively. The pH value tended to first decline and then rise for CK and all
whitefish blocks inoculated with different spoilage bacteria. Notably, pH of whitefish blocks inoculated with Morganella sp.
wf-1 and Morganella sp.wf-2 was much higher than that of CK and whitefish meat inoculated with other spoilage organisms
at 8–48 h time points. In conclusion, Morganella sp.wf-1 was the SSO in whitefish at room temperature also taking into
account the concept of SSO.

Polypeptide Production from Cold-Pressed Walnut Meal by Liquid-State Fermentation
GAO Ruixiong, YAN Qiaozhen, YUE Zhenzhen, LEI Hongjie, XU Huaide
2016, 37(19):  190-196.  doi:10.7506/spkx1002-6630-201619032
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Walnut meal, a by-product left after pressing walnuts for oil, contains rich protein and its nutritional value is high.
Polypeptide production from cold-pressed walnut meal by liquid-state fermentation of Bacillus subtils natto was investigated
in this study. The effects of fermentation time, feed concentration, initial pH, inoculum amount, and fermentation temperature
on the content of polypeptide and the degree of hydrolysis (DH) were studied, and these fermentation parameters were
optimized by single-factor experiments and Box-Behnken response surface methodology. Results showed that the optimum
fermentation parameters were determined as follows: fermentation time, 84 h; feed concentration, 8 g/100 mL; initial pH
value, 8.0; inoculum amount, 11% and fermentation temperature, 33 ℃. The maximum content of polypeptide and DH of
2.58 mg/mL and 37.5%, respectively were simultaneously obtained under these optimized conditions.

Mixed Culture Fermentation and Quality Analysis of Persimmon Peel Vinegar
TIAN Lu, WANG Liping
2016, 37(19):  197-203.  doi:10.7506/spkx1002-6630-201619033
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The fermentation of fruit vinegar from persimmon peel, a byproduct of persimmon processing using
Gluconobacter oxydans, Lactobacillus plantarum and Leuconostoc sp. was studied in this work. Fermentation experiments
were carried out using single and mixed cultures. The optimal combination for mixed culture fermentation was determined
based on fermentation period and product quality. The aroma components were identified by head-space solid phase
micro-extraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS) and the main organic acids
were quantified by reverse-phase high performance liquid chromatography (HPLC) in the best vinegar products. The results
showed that a 1:1 (V/V) mixture of Gluconobacter oxydans and Lactobacillus plantarum gave the best product quality. The
optimal vinegar fermentation time was 6 days. Under these optimized conditions, the sensory evaluation score was 94.9
points, and 51 aroma components, mainly alcohols, esters, with lactic acid and acetic acid being the predominant organic
acids, were identified in the product. Moreover, the product had a strong persimmon flavor and a strong vinegar fragrance
with a good balance between them and it tasted good.

Effect of Different Drying Methods on Angiotensin Converting Enzyme Inhibitory Activity of Peptides from Bovine Casein Hydrolysate
HU Zhihe, ZHAO Yong, XIA Lei, LI Yanjun, XUE Lu, SUN Zhengang, WU Wenqi, FENG Yongqiang
2016, 37(19):  204-210.  doi:10.7506/spkx1002-6630-201619034
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The objective of this paper was to explore the effect of different drying methods i.e., spray drying, fluid bed
drying and vacuum freeze drying on the angiotensin converting enzyme (ACE) inhibitory activity of peptides from bovine
casein hydrolysate. The operating parameters were optimized to obtain both a moisture content lower than 5% and reduced
half inhibitory concentration (IC50) for ACE inhibition of dried product. The antihypertensive efficiency of the dried products
obtained by different drying methods was evaluated by animal tests. The results showed that the spray drying conditions
were optimized as 190 ℃, 75 ℃ and 44 mL/min for air inlet and air outlet temperatures and feeding rate, respectively. The
IC50 for ACE inhibition of the dried product obtained under these conditions was 0.442 mg/mL. The optimal fluid bed drying
conditions were established as 65 ℃, 180 mL and 30 g for air inlet temperature, loading amount and suspending medium
amount, respectively, which gave a dried product with an IC50 of 0.294 mg/mL for ACE inhibition. The IC50 for ACE
inhibition of the dried product obtained by vacuum freeze drying was 0.275 mg/mL. The results of animal tests showed that
upon oral administration of the three different dried products at the same dose, the anti-hypertension activity of dried product
was best maintained by by vacuum freeze drying, followed by fluid bed drying, and spray drying caused the maximum loss
of anti-hypertension activity. Therefore, vacuum freeze drying is a better drying method for casein hydrolysate rich in ACE
inhibitory peptides.

Kinetic Study of β-Glucanase Production by Batch Fermentation at Different Temperatures
ZHAO Xiyue, SONG Houyu, CAI Zhiqiang, CHEN Xiaohua
2016, 37(19):  211-215.  doi:10.7506/spkx1002-6630-201619035
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The effect of different temperatures on the growth of Bacillus subtilis ZJF-15, substrate consumption and
β-glucanase production was studied by conducting batch fermentation experiments in a 5-L fermentation tank. The
fermentation conditions were determined as 400 r/min, 1.0 L/(L·min), 7.0, 5%, 0.6 and 35–37 ℃ for rotating speed,
ventilation rate, initial fermentation pH, inoculum quantity, medium loading coefficient and culture temperature, respectively.
The results showed that increased culture temperature led to a higher reaction rate, accelerated bacterial growth and
metabolism, earlier production of β-glucanase, faster enzyme inactivation, shortened fermentation period and finally reduced
production of β-glucanase. The kinetic equations for bacterial growth, substrate consumption and β-glucanase production of
Bacillus subtilis ZJF-15 were established by batch fermentation.

Comparative Enzymatic Kinetics of Polyphenol Oxidase from Different Grape Varieties
YAN Xiaoyu, DONG Zhe, WANG Shasha, ZHOU Yali, SU Pengfei, YUAN Chunlong
2016, 37(19):  216-221.  doi:10.7506/spkx1002-6630-201619036
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The kinetic parameters Km and vmax/Km of polyphenol oxidase (PPO) from three Franco-American hybrid grape
varieties namely “Guankou”, “Goldfinger”, “Huangmi” and two Vitis vinifera varieties i.e., Zexiang and seedless white
were compared towards different substrates: catechol, 4-methylcatechol, catechin and caffeic acid as well as optimal pH
and temperature, thermal stability, and the effect of inhibitors on PPO activity. Results showed that the affinity of PPO
from five varieties grapes for catechol was significantly different, whereas no significant difference was observed when
4-methylcatechol, catechin and caffeic acid were used as substrates. The catalytic efficiency of PPO from Franco-American
hybrid grapes and Vitis vinifera for catechol was significantly different while no significant difference was observed when
4-methylcatechol, catechin and caffeic acid were used as substrates. The catalytic efficiency of PPO from “Guankou”
grapes for catechin and caffeic acid was obviously higher than that of four other varieties of grapes. Among inhibitors
tested, ascorbic acid and sodium metabisulfite had stronger inhibition on PPO from all five varieties. The inhibitory effect of
sodium metabisulfite on PPO from “Guankou” grapes was weaker than on PPO from four other varieties. Optimal pH and
temperature of PPO from five varieties of grapes had no significant difference.

Nutrition & Hygiene
Effect of Resveratrol on Metabolic Network Flux in Rats
XU Lianjie, WANG Huisong, PANG Guangchang
2016, 37(19):  222-226.  doi:10.7506/spkx1002-6630-201619037
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A large number of studies have shown that lactic acid metabolism flux can be used to quantitatively describe
the state of the body in the condition of normal life. When it is reduced, the body is in good shape; in contrast, when it is
increased, the body is in the state of inflammation or detoxification. In recent years, a number of reports have demonstrated
the prevention of diseases of modern civilization by resveratrol and it is evident that this effect is closely related to lactate
metabolism flux. However, studies on its metabolism in the body have rarely been reported. In the present study, one control
group and three resveratrol treatment groups at low, medium and high doses (2, 20 and 200 mg/kg), each consisting of 6 male
rats were designed. After the rats were administered by gavage, a metabolic network model for metabolic flux analysis was
established. The results showed that the body catabolism was reduced by administration of 2 mg/kg of resveratrol, but it was
increased dose-dependently when the dose was over 20 mg/kg. Based on these results, resveratrol at 2 mg/kg could result
in the lowest body catabolism, suggesting that it can help prevent and treat diseases of modern civilization. As it resulted in
a significant increase in the body catabolism, resveratrol at 200 mg/kg could cause toxic side effects to the body. Therefore,
resveratrol can play a role in protecting the body against diseases only in a certain dose range.

Effects of Two Feeding Conditions on Nutritional Quality of Sunit Sheep Meat
LUO Yulong, WANG Bohui, JIN Zhimin, LIU Xiawei, JIN Ye
2016, 37(19):  227-231.  doi:10.7506/spkx1002-6630-201619038
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The objective of this study was to investigate the difference in nutritional components of Longissimus dorsi,
Biceps femoris and Triceps brachii muscles from Sunit sheep subjected to two feeding methods (grazing and house-feeding).
Sunite sheep were slaughtered at 12 months of age for the collection of muscle samples. The results showed that pH of the
house-feeding group measured at 45 min postmortem was significantly higher than that of the grazing group (P < 0.05), and
it was not significantly different from the grazing group at 24 h postmortem. Additionally, intramuscular fat content of the
house-feeding group was higher than that of the grazing group. However, crude protein, ash, thiamine and reducing sugar
contents of the grazing group were higher than those of the house-feeding group, and the absorption of mineral element
contents in Sunit sheep was highly correlated with different feeding methods. The accumulation of nutritional components in
grazing Sunit sheep was better than in house-fed sheep, and the meat of grazing Sunit sheep was rich in a variety of nutrients
with good quality and high nutritional value.

Disrupting Effect of Peptides Derived from in Vitro Digestion of Tofu Protein on the Transportation of Micellar Cholesterol
DONG Yupin, CHEN Ze, XUAN Jia, JIA Hui, ZHAO Dayun
2016, 37(19):  232-236.  doi:10.7506/spkx1002-6630-201619039
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Soy protein peptides have significant hypocholesterolemic activity. But at present most studies are focused on
small molecular peptides, and few explorations have been made on their hypolipidemic mechanism. In the present study, an
in vitro gastrointestinal digestion model was applied to simulate the gastrointestinal digestion of tofu protein. The digested
products were classified into three levels: > 10 000, 3 000-10 000, and < 1 000, according to their molecular weights (MR).
The effect of these digested products on disrupting the transportation of micellar cholesterol was explored based on dietary
mixed micelles (DMM) experiments with two experimental matrixes and two test methods. The results indicated that the
products with MR > 10 000 had the strongest suppressing effect on transportation of micellar cholesterol. The absorption rate
of micellar cholesterol in their presence was 62.40%, which was superior to the positive control, VAWWMY (Val-Ala-Trp-
Met-Tyr) with an absorption rate of micellar cholesterol of 68.41%. The effect of the products with MR > 10 000 was enhanced
first and then reduced with the increase in its concentration. In addition, the results of two cholesterol detection methods and the
transportation efficiencies of two cholesterol micelles were consistent. Peptides derived from in vitro digestion of tofu protein
exerted a significant inhibitory effect on the micellar solubility of cholesterol. The current work has provided the first approach to
exploring the potential effect of tofu protein hydrolysates (TPH) on reducing cholesterol absorption in the intestine.

Preparation and Bioactivity of Peptides from Strongylocentrotus nudus
WANG Ting, WANG Xiaohui, MA Ying, JI Xiaotong, WANG Ling, NIAN Yiying, XUE Peng,MENG Shuang, QIN Lei, LI Dongmei, ZHANG Gongliang, HOU Hongman, SUN Liming
2016, 37(19):  237-242.  doi:10.7506/spkx1002-6630-201619040
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Strongylocentrotus nudus is one of the major species of economic sea urchin in China. It has high food and
medicinal value due to its delicious taste and nutritional richness. In this work, bioactive peptides were prepared by
enzymatic hydrolysis of Strongylocentrotus nudus gonads with papain and their bioactivities were investigated. Five
fractions with molecular weight distribution of < 1, 1–3, 3–5, 5–10 and <10 kD were obtained by ultrafiltration of the
hydrolysate. Results showed that all the peptide fractions at a final concentration of 200 μg/mL could promote lymphocyte
growth. Moreover, at this concentration, all the peptides except the fraction of < 1 kD could inhibit the growth of HeLa
cells, and promote the phagocytic function of peritoneal macrophages. At 50 μg/mL, all the peptide fractions could protect Chang
liver cells against oxidation induced by tert-butyl hydroperoxide; butylhydroperoxid through direct and indirect pathways. All
the peptides could inhibit the classical complement pathway activity in a dose-dependent manner. All the above results suggested
potential regulatory activity on cellular and humoral immune function and anti-oxidant capacity. The multiple bioactivities of these
peptides deserve further investigation.

Effect of Oral Administration of Casein Hydrolysate Containing ACE Inhibitory Peptides and Purple Sweet Potato Extract on the Systolic Blood Pressure (SBP) of Spontaneously Hypertensive Rats (SHR)
XIA Lei, HU Zhihe, LI Yanjun
2016, 37(19):  243-248.  doi:10.7506/spkx1002-6630-201619041
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In order to investigate the effect of casein hydrolysates containing ACE inhibitory peptides and purple sweet
potato extract containing anthocyanins on the systolic blood pressure (SBP) of spontaneously hypertensive rats (SHR) and
Wistar rats, 12-week-old male SHR and Wistar rats were orally administered with different doses of casein hydrolysates (10,
20, 30, and 40 mg/kg mb) and purple sweet potato extract (5.4, 10.8, 21.6 and 32.4 mg/kg mb) as well as combinations of
casein hydrolysates at two hypotensive doses identified and purple sweet potato extract at three hypotensive doses selected,
respectively. The blood pressure of SHR was tested by non-invasive automated sphygmomanometer. The results showed
that both casein hydrolysates and purple sweet potato extracts had a significant hypotensive effect on SHR rats. Moreover,
their effect was significantly enhanced when they were applied in combination at a single dose (P < 0.05). The SBP of SHR
rats was reduced by (24.67 ± 4.46), (28.47 ± 3.96), and (41.51 ± 4.89) mmHg, respectively, at 4 or 5 h after administration
of 10 mg/kg mb casein hydrolysates in combination with purple sweet potato extract at three doses of 5.4, 10.8 and
21.6 mg/kg mb, while it was reduced by (38.03 ± 3.46), (43.92 ± 2.92), and (47.20 ± 4.31) mmHg, respectively, at 5 or 6 h
post-administration of casein hydrolysates at 20 mg/kg mb in combination with purple sweet potato extract at 5.4, 10.8
and 21.6 mg/kg mb. Nevertheless, no effect on the SBP of Wistar rats was observed when they were used in combination.
Combined administration of casein hydrolysates at 10 and 20 mg/kg mb with purple sweet potato extract at 10.8 mg/kg mb
twice daily at 4 h intervals resulted in a decrease in the SBP of SHR rats of (28.20 ± 3.02) and (43.54 ± 2.55) mmHg as
compared with that before administration, respectively. Furthermore, the lower levels of SBP could be maintained for a
long period. Therefore, casein hydrolysate containing ACE inhibitory peptides and purple sweet potato extract containing
anthocyanins, when orally administered in combination, can significantly reduce the SBP of SHR.

Effects of Different Feeding Patterns on Meat Quality and Nutrition of Tibetan Sheep
ZHOU Yuqing, LI Na, XIE Peng, WANG Huan, LEI Yuanhua, LIU Xuan, LI Haipeng, BAO Shanke, SUN Baozhong
2016, 37(19):  249-253.  doi:10.7506/spkx1002-6630-201619042
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In order to improve the breeding efficiency of Qinghai Tibetan sheep, the meat color, pH value, tenderness and
other edible quality indexes of lamb in 3 different feeding patterns (grazing, grazing plus forage supplementation, and
house feeding) were measured by colorimeter, acidity meter and tenderness meter. The contents of fat, protein, moisture
and other harmful substances in the mutton were determined by the national standard methods, and the residues of heavy
metals, antibiotics, agricultural and veterinary drugs were also explored. It was demonstrated that cooking loss rates of lamb
meat from the three feeding patterns were significantly different (P < 0.05), and a significant decrease was observed in the
house feeding group compared with the two other groups. Nonetheless, there was no significant difference in water loss rate
or shearing force among the three groups. The fat content in the house feeding group was significantly increased compared
with that in the two other groups, whereas the difference in moisture content was not significant. Likewise, there was no
significant difference in protein content among these three groups. Moreover, significant difference was observed in saturated
fatty acid contents rather than in unsaturated fatty acid contents. Lead was detected only in the grazing group at a level of
0.022 mg/kg. No other harmful substances were detected in all of these groups. Processing properties of Tibetan sheep in the
house feeding group were better, but higher protein content was found in grazing group. Different uses should be considered
when choosing different feeding patterns in production.

Reviews
Progress in Research on Biofilm Formation Regulated by LuxS/AI-2 Quorum Sensing
LIU Lei, GUI Meng, WU Ruiyun, LI Pinglan
2016, 37(19):  254-262.  doi:10.7506/spkx1002-6630-201619043
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The majority of bacteria form biofilms for growth and development and bacteria within biofilms may better adapt
to environment than their planktonic counterparts. LuxS-dependent quorum sensing is a widespread system used by bacteria
for cell-to-cell communication, which can regulate biofilm formation in a cell density-dependent manner. Autoinducer 2 (AI-2)
produced by LuxS, is a species-nonspecific signal used by both gram-negative and gram-positive bacteria for biofilm
formation. Currently, several inhibitors of LuxS/AI-2 quorum sensing have been determined to influence biofilm formation
based on their anti-AI-2 communication mechanisms. Recently, there has been a surging interest in the mechanism of biofilm
regulation by LuxS/AI-2 quorum sensing system, which is important to better understand the relationship between LuxSdependent
QS system and biofilm formation.

Legal System of Co-Regulation in Food Safety Governance in China from the Perspective of the Characteristics of Food Safety Risk
DU Bo
2016, 37(19):  263-268.  doi:10.7506/spkx1002-6630-201619044
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From the perspective of the characteristics of food safety risk, the measure for managing and controlling risk
is one of the ways to solve the problem of food safety. Food safety in the whole society which is under the control of
food safety risk is not only the starting point but also the ultimate goal of the legal system of co-regulation in food safety
governance. Therefore, it is proposed that the system should consist of three parts: public participation, main responsibility
and shared rights. Following the principles of the co-regulation in food safety governance will be helpful to the realization of
the legal system of co-regulation in food safety governance in China.

Bioactive Components of Potato and Their Functions
MU Taihua, LI Penggao
2016, 37(19):  269-276.  doi:10.7506/spkx1002-6630-201619045
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Potato is not only a nutritious food, but also contains a great number of bioactive components that may exert
special bioactivity in human body and play an important role in the prevention and adjuvant treatment of many diseases. In
this paper, the major bioactive components of potato and their biological effects are reviewed. Factors that may influence
the bioactive components of potato such as species, storage, cooking and processing methods are also discussed as well
as factors that may exert harmful or poisonous effects on human health upon consumption of potato and potato products.
Finally, perspectives and suggestions on future studies are proposed. This paper may provide helpful information for further
studies and utilization of potato.

A Review of the Formation and Control of Ice Crystals in Aquatic Products during Freezing Storage
LI Yuan, WANG Liping, LI Yujin, HU Yaqin
2016, 37(19):  277-282.  doi:10.7506/spkx1002-6630-201619046
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Freezing storage is an important preservation method for aquatic products as it could maintain their freshness to
the maximum extent. However, the quality of aquatic products may inevitably be damaged in terms of flavor and texture
due to the formation of ice crystals during freezing storage. Drip loss may also be unavoidable during thawing. This review
elucidates the mechanism of the formation of ice crystals, and discusses the factors which affect the formation of ice crystals
including freezing rate, freezing temperature, and temperature fluctuation. The existing methods for controlling the formation
of ice crystals in the aquatic products are also described such as superchilling and pressure shift freezing.

Advances in Research on Protective Effect of Polyphenols in Cardiovascular Disease
LI Lu, Lü Jiaqian, JIANG Chengjia, CHEN Jiajun, LI Wenjuan, ZHANG Yansong, YAO Yufei
2016, 37(19):  283-288.  doi:10.7506/spkx1002-6630-201619047
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The World Health Organization reported in 2015 that cardiovascular disease was a leading cause of death
worldwide. The number of death from cardiovascular diseases is increasing year by year. A large number of literature
reported that tea polyphenols have a good preventive effect on cardiovascular diseases, such as atherosclerosis, arrhythmia
and myocardial ischemia reperfusion. The aim of this article is to review the health benefits of tea polyphenols against
cardiovascular diseases and to outline the molecular mechanisms involved in cardioprotection of tea polyphenols.
Additionally, it also describes the current status of research on tea polyphenols in China for the purpose of providing an
outlook to the application prospects of polyphenols.

Advances in Research on β-1,3-1,4-Glucanase
XIA Xuhan, ZHU Chenglin, LI Cheng
2016, 37(19):  289-295.  doi:10.7506/spkx1002-6630-201619048
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β-1,3-1,4-Glucanases (EC 3.2.1.73) are a class of endo-type glucoside hydrolases widely distributed in bacteria,
fungi and plants. They can randomly hydrolyze β-1,4-linkages in β-1,3-1,4-glucans from cereals and have great potential
in the food and feed industries. To date, there are three glycoside hydrolase families (GH16, GH17 and GH26) which
β-1,3-1,4-glucanases belong to whose crystal structures have been resolved. This paper reviews the current knowledge about
the sources, properties, structures and functionalities of β-1,3-1,4-glucanases as well as their recent applications in the food
and feed industry.

A Review of the Application of Quantum Dots as Probes in Fluorescent Immunoassays of Low Molecular Weight Food Contaminants
DAI Jinbo
2016, 37(19):  296-301.  doi:10.7506/spkx1002-6630-201619049
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Quantum dots (QDs) are semiconductor nanoparticles with very interesting optical properties like high quantum
yield, and narrow and size-tunable fluorescence spectra. QDs are applied widely, especially as fluorescence labels in food
safety detection that has received increased attention recently. In this review, three methods for coupling antibody/antigen
to QDs are discussed. The development of QD-based fluorescent immunoassays for the detection of low molecular weight
hazardous compounds in the food safety area is also demonstrated.