Table of Content

25 August 2019, Volume 40 Issue 16
Food Chemistry
Effect of Temperature and pH on Dephosphorylation of Myofibrillar Protein in Vitro
REN Chi, HOU Chengli, LI Xin, BAI Yuqiang, ZHANG Dequan
2019, 40(16):  1-7.  doi:10.7506/spkx1002-6630-20180926-279
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This study determined the effect of temperature (25, 15, and 4 ℃) and pH (5.2, 5.8, and 6.4) on dephosphorylation of myofibrillar protein, aiming to provide a theoretical basis for improving meat quality. Myofibrillar protein from postmortem muscle was extracted and alkaline phosphatase (AP) was added to catalyze its dephosphorylation. The phosphorylation level was detected by sodium dodecyl sulfate-polyacrymyl gel electrophoresis (SDS-PAGE) followed by sequential fluorescence staining of the gels using Pro-Q Diamond and SYPRO Ruby. Moreover, AP activity was measured by a commercial kit. The results demonstrated that at pH 5.8 and 6.4, the phosphorylation level of myofibrillar protein in the AP group significantly decreased with the prolongation of incubation (P < 0.05), while no significant change occurred at pH 5.2 (P > 0.05). Likewise, the control group showed no significant change in the phosphorylation level of myofibrillar protein throughout the incubation period (P > 0.05). At 4 ℃ and pH 5.2, AP activity was inhibited, delaying the catalytic time (P < 0.05). Interestingly, AP catalyzed not only the dephosphorylation of myofibrillar protein but also its own dephosphorylation, which caused no loss of activity. Increasing temperature and pH in a certain range could promote the dephosphorylation ability of AP, thereby decreasing the phosphorylation level of myofibrillar protein and making the reaction start earlier. These findings can be important for improving meat quality and provide a new idea for meat preservation.
Binding between Quercetin and β-Lactoglobulin B: Mechanism and Improved Solubility of Quercetin
LI Xiaolei, ZHENG Lili, AI Binling, ZHENG Xiaoyan, YANG Yang, YANG Jingsong, SHENG Zhanwu
2019, 40(16):  8-16.  doi:10.7506/spkx1002-6630-20180614-279
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In order to improve the poor water solubility of quercetin, the mechanism of quercetin binding to β-lactoglobulin B was studied by various spectroscopies, isothermal titration calorimetry and molecular simulation, and changes in the secondary structure of β-lactoglobulin B and quercetin solubility were determined after the binding reaction. The results showed that quercetin was able to bind to β-lactoglobulin B through hydrogen bonding and van der Waals forces. Threedimensional fluorescence spectra, synchronous fluorescence spectra and UV-visible absorption spectra demonstrated that quercetin quenched β-lactoglobulin B fluorescence strongly in the static mode. Furthermore, circular dichroism and Fourier transform infrared spectra indicated that quercetin induced partial transition of α-helix to β-structures in β-lactoglobulin B. Moreover, molecular simulation results showed that the binding site of quercetin on β-lactoglobulin B was located in a cavity formed by α-helix and β-turn, and 8 amino acid residues were involved in the binding site. In combination with quercetin, the threonine residue at position 125 provided strong hydrogen bonds, while the remaining residues provided van der Waals forces. Besides, the solubility of quercetin was increased by about 1 844 times after its conjugation to β-lactoglobulin B. In summary, the water solubility of quercetin can be significantly improved by conjugating it to β-lactoglobulin B.
Influences of Calcium Salt and Emulsifier Composition on in Vitro Digestion Properties of 1,3-Dioleoyl-2-Palmitoylglycerol Emulsions
WU Wenbin, XU Yuxi, XIONG Hua, HU Jiangning, ZHU Xuemei
2019, 40(16):  17-24.  doi:10.7506/spkx1002-6630-20180622-421
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An in vitro simulated gastrointestinal (GI) digestion system was used to investigate the effects of ratio between casein and whey protein and calcium chloride concentration as well as interaction between the two factors on the digestion of a structured lipid made with 1,3-dioleoyl-2-palmitoylglycerol (OPO). The changes in the release rate of fatty acids, particle size distribution and fatty acid composition were determined during the digestion process. The results showed that at the same emulsifier ratio, lipid bioavailability of OPO emulsions increased with the increase of CaCl2 concentration. At a CaCl2 concentration of 20 mmol/L, the release rate of free fatty acids (FFA) from emulsions stabilized with different ratios between whey protein and casein decreased as follows: 10:0 > 6:4 > 0:10 during simulated gastric digestion. For each CaCl2 concentration, the average particle size of the emulsions became smaller after simulated GI digestion. The d(0.1), d(0.5), and d(0.9) values of the fresh emulsions increased with increasing CaCl2 concentration. Both the release rate and amount of FFA during the simulated intestinal digestion of the three emulsions became greater with increasing CaCl2 concentration. FAA and monoglyceride composition analysis showed that the digested products consisted mainly of palmitic acid and oleic acid. The effect of different calcium salts on the lipid digestion of OPO emulsions was also investigated. It turned out that calcium salts with higher solubility promoted lipid hydrolysis and that the release rate and amount of FFA with different calcium salts during simulated intestinal digestion were ranked in the following order: calcium citrate > calcium chloride > calcium lactate > calcium carbonate.
Effects of γ-Polyglutamic Acid on the Self-Assembly of Pepsin-Solubilized Collagen from Tilapia (Oreochromis niloticus) Skin
YAN Mingyan, ZHAO Xiaochen, YANG Xiao, XU Hao, AN Xiangsheng, LI Yinping
2019, 40(16):  25-29.  doi:10.7506/spkx1002-6630-20180617-341
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The effects of γ-polyglutamic acid (γ-PGA) on the kinetic self-assembly of pepsin-solubilized collagen (PSC) from tilapia (Oreochromis niloticus) skin and the microstructure and properties of the resulting hydrogel were investigated. It was found that the self-assembly process of PSC consistently involved the nucleation and growth phases in the presence of various concentrations of γ-PGA, but it prolonged the nucleation time, and decreased the rate constant of the nucleation phase, whereas it firstly rose and then reduced that of the growth phase. After the self-assembly, PSC was formed into a white hydrogel, which showed a three-dimensional fibril network as observed by scanning electron microscopy, but γ-PGA could affect the density of collagen fibrils. The network density displayed an increasing trend with increasing γ-PGA/PSC ratio up to 80%, but significantly decreased as the ratio further increased to 100%. Correspondingly, the gel strength was firstly enhanced and then weakened. Nevertheless, neither the enzymatic resistance nor thermal stability of the collagen hydrogel was improved evidently by γ-PGA, suggesting that further studies are necessary to enhance the gel properties by cross-linking.
Effects of Trehalose and Mannitol on Freeze-Thaw-Induced Structural and Functional Changes of Myofibrillar Proteins from Mantis Shrimps (Oratosquilla oratoria)
CHEN Jinyu, LI Bin, HE Lili, LIANG Huanhuan, WEI Yingxia, HAN Yeqin, ZHANG Kunsheng
2019, 40(16):  30-37.  doi:10.7506/spkx1002-6630-20180606-087
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The effects of a combination of trehalose and mannitol (both 4 g/100 mL) on freeze-thaw-induced structural and functional changes of myofibrillar proteins from Oratosquilla oratoria were studied, aiming to provide a theoretical basis for the preservation of seafood products. In this study, 0, 1, 3 and 5 freeze-thaw cycles were performed on the experimental group with cryoprotectants and the control group without cryoprotectants. Protein carbonyl content, total sulfhydryl content, surface hydrophobicity, tryptophan fluorescence, storage modulus (G’), gel strength and water-holding property, gel microstructure, and emulsifying properties were determined to explore the cryoprotective effects of trehalose and mannitol. As the number of freeze-thaw cycles increased, protein carbonyl content and surface hydrophobicity increased significantly (P < 0.05), while total sulfhydryl content and tryptophan fluorescence intensity decreased significantly (P < 0.05). Protein aggregation was found to different extents and the gelation and emulsifying properties were reduced markedly. The addition of trehalose and mannitol effectively inhibited protein denaturation, reduced the changes in protein structure, increased the storage modulus (G’) of myofibrillar protein during thermal gelation, and improved the gel properties (gel strength and water-holding capacity and three-dimensional network structure), emulsifying activity and emulsion stability. Trehalose and mannitol could combine with functional groups of myofibrillar protein, thereby avoiding protein aggregation. In addition, by binding with water molecules, trehalose and mannitol could reduce the eutectic temperature, decrease the formation of ice crystals, retard protein aggregation, and prevent protein condensation and denaturation, thus improving the quality of mantis shrimp meat during freezing storage.
Preparation and Characterization of Wheat Gluten Nanoparticles-Xanthan Gum Pickering Emulsions
XIE Anqi, DENG Sumeng, ZUO Bailu, ZHOU Wei, ZHU Yuqing, ZOU Liqiang, LIU Wei
2019, 40(16):  38-44.  doi:10.7506/spkx1002-6630-20180709-111
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In this study, wheat gluten nanoparticles and xanthan gum were used to synergistically stabilize Pickering emulsions and their physicochemical properties and microstructure were characterized. The results showed that stable Pickering emulsions could be prepared through the synergism between xanthan gum and wheat gluten nanoparticles. While low concentration of xanthan gum (0.2%) promoted creaming, the emulsion could be stored for one month at 4 ℃ without any aggregation or creaming when the concentration of xanthan gum was equal to or greater than 0.3%. When the concentration of xanthan gum was 1%, the emulsion became unstable after 30 days. The emulsion stability varied with different orders of emulsification. The M-WG-XG emulsion (prepared by sequential dispersion of a mixture of wheat gluten nanoparticles and corn oil, followed by addition of xanthan gum) had the highest stability and smallest particle size (21.4 ± 0.314) μm. The addition of xanthan gum increased the net charge and consequently stability of emulsions. The droplets were evenly distributed and the interface layer exhibited a multilayer structure under confocal laser scanning microscopy. Compared to the other emulsions, the M-WG-XG emulsion possessed a better viscoelasticity and higher salt stability (0–1 000 mmol/L NaCl) against aggregation.
Effect of Partial Substitution of Sodium Nitrite with Glycosylated Nitrosohaemoglobin on Quality of Harbin Air-Dried Sausage
LIU Pengxue, LIU Haotian, ZHANG Huan, KONG Baohua
2019, 40(16):  45-51.  doi:10.7506/spkx1002-6630-20180714-181
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In this study, we investigated the effects of partial substitution of sodium nitrite with different concentrations of glycosylated nitrosohaemoglobin (GN-Hb) on microbiological growth, lipid oxidation and sensory quality of Harbin air-dried sausage. The results showed that GN-Hb had no significant influence on the pH, water activity (aw), total bacterial count or lactic acid bacteria (P > 0.05) during the fermentation of sausages. The addition of GN-Hb significantly inhibited Escherichia coli growth and lipid oxidation (P < 0.05). The color analysis showed that partial substitute of sodium nitrite with GN-Hb improved the redness (a*) value of sausages, and no significant difference in lightness (L*) values was found when comparing sausages with 0.5 and 1.0 g/kg GN-Hb with that with 0.10 g/kg sodium nitrite (P > 0.05). The results of sensory evaluation showed that addition of GN-Hb improved the sensory quality of air-dried sausages, especially the flavor. Overall, this result revealed that GN-Hb can be partially substituted for sodium nitrite in Harbin air-dried sausage.
Effects of Phosphorylation on Titin Degradation at Different Ca2+ Concentrations in Vitro
WANG Ying, LI Xin, LI Zheng, ZHU Jie, ZHANG Sheqi, ZHANG Dequan
2019, 40(16):  52-57.  doi:10.7506/spkx1002-6630-20180920-211
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The objective of this study was to investigate the effects of phosphorylation on titin degradation at different Ca2+ concentrations in vitro. Titin was extracted from ovine longissimus lumborum muscles. Protein kinase A (PKA) and alkaline phosphatase (AP) were individually added to titin in vitro to change its phosphorylation level. The samples were then incubated with μ-calpain at 4 ℃ for 2 days at Ca2+ concentrations of either 0.05 or 2 mmol/L. The pH of the systems was measured and the degrees of phosphorylation and degradation of titin were determined. The results showed that there were no significant differences in pH values among the PKA, AP and control groups (P > 0.05). The relative phosphorylation levels of titin in the groups followed the decreasing order of PKA > control > AP (P < 0.05). The degradation product of about 1 200 kDa was detected in the AP group after 12 h incubation at a Ca2+ concentration of 0.05 mmol/L, but not in the other groups. The 1 200 kDa band was detected in both the PKA and control groups after 12 h, but after 0.5 h in the AP group at a Ca2+ concentration of 2 mmol/L. These observations demonstrated that the phosphorylation of titin in vitro was significantly enhanced by PKA but attenuated by AP. With the increase of calcium concentration, the degradation rate of titin became faster. The degradation of titin in the AP group was faterer than in the other groups at the same Ca2+ concentration. It was suggested that the dephosphorylation promoted titin degradation.
Characterization of the Enzyme-Induced Aggregation Behavior of Soybean Protein Isolate
2019, 40(16):  58-63.  doi:10.7506/spkx1002-6630-20190117-198
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The changes in the degree of hydrolysis (DH), turbidity, components and molecular mass, surface hydrophobicity and structure of soybean protein isolate (SPI) were studied after being treated with an aspartic protease (AP) from Quambalaria cyanescens. The enzyme-induced aggregation behavior of SPI was determined by laser scanning confocal microscopy (LSCM) and atomic force microscopy (AFM). The results indicated that the DH and turbidity of SPI increased first and then tended to be stable with the increase of AP treatment time. The enzymatic treatment caused subunit dissociation of SPI, leading to its hydrolysis into smaller molecules. This treatment also increased the surface hydrophobicity of SPI. The circular dichroism (CD) spectrum and intrinsic fluorescence emission spectrum of SPI showed that the enzymatic treatment significantly changed its structure, causing the exposure of internal hydrophobic groups and hydrophobic amino acid residues. LSCM and AFM observation showed that the increases of enzymatic treatment time caused more extensive aggregation of SPI, resulting in the formation of bigger, irregular and discontinuous aggregates.
Effect of Inulin on Physicochemical Properties of Wheat Gluten
MU Wanju, FENG Jia, LI Xiuxiu, LI Shuhong, CHEN Ye
2019, 40(16):  64-68.  doi:10.7506/spkx1002-6630-20180919-209
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The effects of adding different amounts of inulin on emulsification and thermal properties of wheat gluten protein were studied by differential scanning calorimetry and Fourier transform infrared spectroscopy. The protein structure was characterized by scanning electron microscopy. The results showed that inulin even at low concentration had a great effect on the emulsifying properties of wheat gluten. Inulin at a concentration of 10% increased the emulsifying activity index by 14.4%, and at 7.5% by 18.7%. Thermodynamic experiments showed that inulin increased the denaturation temperature and decreased the denaturation enthalpy of the protein. Inulin at a concentration of 12.5% increased the denaturation temperature. The structural analysis showed that the content of disulfide bond in the protein increased by 222% with the addition of 20% inulin. Moreover, the β-turn structure of the wheat protein was transformed into β-sheet and random coil structure in the presence of inulin. The gluten network structure became denser with inulin addition.
Stability and Chemical Changes of Catechins during Oolong Tea Processing
LIU Honglin, ZENG Yitao, ZHAO Xin
2019, 40(16):  69-74.  doi:10.7506/spkx1002-6630-20180727-326
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This study was conducted to investigate the impact of lightly fermented Oolong tea processing on catechins as bioactive compounds. Freshly harvested tea shoots were immediately processed under strict control. Tea infusions from each processing stage were analyzed for total catechin profiles and various individual compounds including (-)-gallocatechin (GC), (-)-epigallocatechin (EGC), (+)-catechin (C), (-)-epicatechin (EC), (-)-epigallocatechin gallate (EGCG), (-)-gallocatechin gallate (GCG), (-)-epicatechin gallate (ECG) and (-)-catechin gallate (CG). During processing, the content of total catechins was slightly decreased by approximately 10% while the contents of individual catechins varied differently. Among the processing operations, indoor withering, pan-firing and drying steps had potent impacts on catechin concentrations. This result should be considered for tea manufacturing in order to maximize the potential health benefits of catechins in Oolong tea. We expect that this study will pave a chemical foundation for Oolong tea processing.
A Spectroscopic Study of Bovine Casein Structure as Affected by Interaction with Xylitol
KONG Fanhua, CAO Xueyan, KANG Shimo, LI Weixuan, GUAN Boyuan, LI Mohan, YANG Mei, YUE Xiqing
2019, 40(16):  75-82.  doi:10.7506/spkx1002-6630-20180727-323
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In this paper, fluorescence, Fourier transform infrared and circular dichroism spectroscopies were used in conjunction to study the interaction between bovine casein (Cs) and xylitol (XY) and its effect on the structural and functional properties of casein. The results of fluorescence spectroscopy indicated that xylitol strongly quenched the fluorescent intensity of bovine casein. The quenching mechanism was static quenching that generates a new complex. The binding constants for the interaction at 300, 310 and 320 K were 5.326 × 106, 2.600 × 106 and 2.160 × 106 L/mol, respectively, and the binding sites were 1.513, 1.452 and 1.422, respectively. The main binding forces were electrostatic attraction and hydrophobic force with a binding distance of 3.564 nm. The results of synchronous fluorescence and threedimensional fluorescence spectroscopies revealed that the interaction site was closer to the tryptophan residues; this interaction enhanced the hydrophobicity of the surrounding microenvironment and changed the molecular conformation of bovine casein. Fourier transform infrared and circular dichroism spectroscopies showed that xylitol changed the secondary structure of bovine casein by increasing the relative content of α-helix and reducing the relative content of random coil structure and as a result, the structure of bovine casein became more compact. Furthermore, this structural change led to a decrease in the emulsifying activity, an increase in the emulsion stability, and a decrease in the surface hydrophobicity of casein. These results provide a theoretical basis for the development of functional dairy-based ingredients.
Comparative Physicochemical and Flavor Characteristics of Maillard Reaction Products Derived from Enzymatic Hydrolysate of Sipunculus nudus and Different Saccharides
YOU Gang, NIU Gaigai
2019, 40(16):  83-90.  doi:10.7506/spkx1002-6630-20180613-205
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Maillard reaction products (MRPs; 120 ℃, 120 min) derived from an enzymatic hydrolysate (SEH) of Sipunculus nudus and different saccharides (glucose, maltose, xylose and gum arabic) were characterized by measuring their absorbance at 420 nm and 294 nm, pH, color difference, total amino acid (TAA) composition, and free amino acid (FAA) composition and fluorescence intensity. Moreover, an electronic nose (E-nose) was used to analyze changes in their volatile flavor compounds. The results obtained suggested that SEH conjugated with saccharides showed a higher browning degree, a yellower color with darker lightness, and a lower pH value. Additionally, the contents of 17 FAAs and TAAs in MRPs were reduced, especially for 8 bitter amino acids, relative to SEH, which improved the bitterness of SEH. The fluorescence spectra revealed that the fluorescence intensity of MRPs was significantly reduced and a slight red-shift was observed as compared to SEH, leading to changes in the tertiary structure of SEH. On the basis of the above results, the reaction degree of SEH conjugated with different saccharides followed the declining order: xylose > gum arabic > glucose > maltose. E-nose could distinguish the flavor characteristics of SEH from those of MRPs better with linear discriminant analysis (LDA) than with principal composition analysis (PCA). Loadings analysis showed that sensors 2 and 7 contributed greatly to the first principal component, while sensors 6 and 9 to the second principal component, indicating that ammonia oxides, methane and sulfides were the main volatile flavor components that could discriminate between SEH and MRPs. In this study, we have found that the flavor and reaction characteristics of MRPs derived from SHE and different saccharides are different, suggesting that an appropriate saccharide can be chosen to meet technological demands.
Synthesis of γ-Glutamyl Dipeptides in Lactic Acid Bacteria and Its Influence on the Taste of Steamed Bread
YAN Bowen, YANG Huayu, CAI Yijie, FAN Daming, LIAN Huizhang, CHEN Wei, ZHANG Hao, ZHAO Jianxin
2019, 40(16):  91-96.  doi:10.7506/spkx1002-6630-20190125-327
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This study is aimed at investigating the synthesis of γ-glutamyl dipeptides in sourdough fermented by various Lactobacillus strains and the effect of γ-glutamyl dipeptides on the taste of steamed bread. The results indicated that Lactobacillus preferentially utilized glutamate and isoleucine to synthesize γ-glutamyl glutamate and isoleucine, respectively. The synthesis of γ-glutamyl dipeptides was species-specific among lactobacilli. Further, based on the electronic tongue analysis, the addition of sourdough fermented by Lactobacillus had a great influence on the taste of steamed bread, indicating that γ-glutamyl dipeptides are directly responsible for enhancing the saltiness of steamed bread. This study provides an important theoretical basis and new research direction for the development of low-sodium fermented foods.
A Mechanistic Study of Citrus Infection by Penicillium expansum
ZHAO Lina, LI Huifang, YU Jiang, LIU Kun, ZHANG Xiaoyun, YANG Qiya, ZHANG Hongyin
2019, 40(16):  97-106.  doi:10.7506/spkx1002-6630-20181213-162
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Strain H1, isolated from rotten citrus wounds in our laboratory, was identified as Penicillium expansum and was found to be able to produce citrinin (CIT). In this study, the possible mechanisms underlying citrus infection by P. expansum were investigated by measurement of cell wall degrading-enzymes and transcriptome analysis. The results showed that P. expansum H1 could produce polygalacturonase, pectin methylgalacturonase, endo-1,4-β-D-glucanase and β-glucosidase in both modified Marcus medium and infected citrus tissues. Meanwhile, the expression levels of all genes related to the infection were up-regulated, such as those related to cell wall degrading-enzymes, CIT production, the pH changes of the host, antioxidative stress response and effector factors. The results indicated that cell wall-degrading enzymes, CIT, pH, and antioxidant enzymes all play vital roles in citrus infection by P. expansum H1.
Analysis of Microbial Community Diversity in Chinese Korean Traditional Rice Wine and Its Starter Culture Using High-Throughput Sequencing
NING Yali, WU Yue, HE Qiang, XU Shuaizhe, CHEN Yan
2019, 40(16):  107-114.  doi:10.7506/spkx1002-6630-20180917-173
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The microbial community structure and diversity in crude and refined Korean traditional rice wine from Yanbian, Jilin province and its starter culture were analyzed by high-throughput sequencing of the bacterial 16S rDNA V3 region and the fungal ITST1 region on the Illunina MiSeq and HiSeq platforms, respectively. The results of sequencing showed effective in-depth coverage of the microbial species, and the starter culture and rice wines were all populated by a highly diverse array of bacteria and fungi. The rice wines were similar to each other in microbial community structure, but significantly different from the starter culture. At the genus level, a total of 147 bacterial species were identified in all the samples. The dominant bacteria in the starter culture were Pseudomonas (5.00%) and Enterobacter (4.28%), while Lactobacillus (3.72% and 7.73%) and Enterobacter (6.31% and 4.41%) were dominant in both the crude and refined wines. Meanwhile, at the specie level, 12 fungi were identified in all these samples. The dominant fungus in the starter culture was Guehomyces pullulans (10.22%), while Saccharomyces cerevisiae (49.48% and 81.52%) and Hyphopichia burtonii (29.47% and 6.43%) were dominant in both the crude and refined wines.
Effect of Different Winemaking Conditions on Fermentation Aroma Production by Saccharomyces cerevisiae
ZHU Xia, LIU Qi, ZHAO Dandan, WANG Lulu, HAN Shunyu, YANG Xueshan
2019, 40(16):  115-123.  doi:10.7506/spkx1002-6630-20180929-321
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In this paper, headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) was used to compare the aroma-producing performance of different strains of Saccharomyces cerevisiae (CY3079, LA-FR, LA-RA, MST, and OFC) in model grape juice and to analyze the variation of aroma compounds produced under different fermentation conditions. The results showed that strain LA-FR had the strongest ability to produce esters and terpenes and displayed the best aroma-producing performance of the strains tested. Therefore, LA-FR was used to study the effects of nitrogen source, fermentation temperature, pH value and SO2 addition on the production of various aroma compounds. When the concentration of nitrogen source increased from 1.0 g/L to 2.0 g/L, the contents of alcohols and terpenes decreased by 36.41% and 42.56%, whereas the contents of esters and acids increased by 72.92% and 26.86%, respectively. In the range of 18–28 ℃, lower temperature fermentation was beneficial to the accumulation of esters and terpenes, but not to the synthesis of alcohols and acids. When the pH increased from 3.2 to 3.8, the contents of esters and terpenes increased by 19.50% and 67.43%, while the contents of alcohols and acids decreased by 30.24% and 34.16%, respectively. The addition of SO2 was positively correlated with the synthesis of alcohols and esters, but negatively correlated with the synthesis of acids and terpenes. The results of multiple regression analysis showed that nitrogen sources had the greatest influence on the contents of alcohol and ester, and that fermentation temperature and SO2 addition had the greatest influence on the content of acid and terpenes, respectively. The results of this study can provide theoretical support for further study of the effects of multiple factors on the production of aroma compounds during wine fermentation and the control of wine aroma quality.
Isolation, Purification and Structural Identification of Peptides with Hypolipidemic Activity Derived from Hazelnut Protein
ZHOU Meihan, GUO Yong, WEI Zhen, ZHAO Lan, QIN Hanxiong, WANG Ji, MIN Weihong
2019, 40(16):  124-129.  doi:10.7506/spkx1002-6630-20180606-077
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A peptide with higher hypolipidemic activity was separated and purified from the alcalase hydrolysate of hazelnut protein isolate by ultrafiltration, Sephadex G-25 chromatography, Sephadex G-15 chromatography and reversed-phase highperformance liquid chromatography (RP-HPLC). The amino acid sequence of the peptide was identified by Q Exactive hybrid quadrupole-Orbitrap mass spectrometry. The levels of lipid accumulation, total cholesterol, and triglyceride in 3T3-L1 preadipocytes incubated with the peptide were also determined. The results showed that fraction C3 isolated by Sephadex G-15 chromatography had significantly higher inhibitory activity against pancreatic lipase, cholesterol micelle adsorption capacity, and cellular hypolipidemic activity than any other fractions. The peptide was identified as Phe-Leu-Leu-Pro-His (FLLPH), and it could inhibit 26.31% of total lipid accumulation in 3T3-L1 preadipocytes, and reduce cholesterol and triglyceride levels by 32.67% and 23.87%, respectively, compared to the model control. The present study provides a theoretical basis for the development of hypolipidemic peptides from hazelnut protein.
Analysis of Specific Spoilage Organisms in Chilled Red Swamp Crayfish Using Culture-Dependent Method and High-Throughput Sequencing
JIANG Yangyang, YANG Shuibing, YU Haixia, YAO Jieyu, HU Yaqin
2019, 40(16):  130-136.  doi:10.7506/spkx1002-6630-20180718-229
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In order to reveal the microbial diversity and specific spoilage organisms (SSOs) of red swamp crayfish under refrigerated condition (4 ℃), we individually isolated the SSOs using the culture-dependent method in this study and evaluated their spoilage abilities. Meanwhile, high-throughput sequencing technology was used to identify the spoilage bacterial species in fresh crayfish and those at the middle and late stages of spoilage and to explore the changes in the microbial community during refrigerated storage. The results showed that a higher bacterial diversity was detected by highthroughput sequencing compared to the culture-dependent method and the former method identified more genera than the latter. A total of 11 strains of SSOs were detected by the culture-dependent method, among which Aeromonas jandaei had the strongest spoilage ability while Citrobacter freundii had the weakest spoilage ability. In addition, high-throughput sequencing revealed that the total relative abundance of Shewanella sp., Carnobacterium sp., Brochothrix sp., Psychrobacter sp., Vagococcus sp. and Acinetobacter sp. was 90.57% at the end of shelf life. By comparing the results of the two methods, it was found that the SSOs in chilled crayfish mainly included Shewanella sp., Carnobacterium sp., Brochothrix sp., Psychrobacter sp., Vagococcus sp., Acinetobacter sp., Aeromonas jandaei, and Trichococcus sp..
Genetic Diversity and Phylogeny of Oenococcus oeni Strains Isolated from Winemaking Regions of Changli, Hebei Province
YU Dongliang, SHI Kan, MENG Qiang, LIU Shuwen, HE Ling
2019, 40(16):  137-143.  doi:10.7506/spkx1002-6630-20181115-172
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222 Oenococcus oeni strains isolated from 5 different wineries in Changli, Hebei province were identified by species-specific PCR, and amplified fragment length polymorphism (AFLP) technique was used for genetics research. The AFLP results showed that a total of 221 AFLP genotypes were detected in the 222 strains, with different phenotypes, and their similarity coefficients were 74%–98%, revealing a high level of genetic diversity. By the un-weighted pair-group method with Arithmetic means (UPGMA), two major phylogroups were deciphered at 81.7% similarity level. Additionally and more importantly, the strains from the same winery formed unique clusters, indicating distinct genetic relationships with their origins and validating that O. oeni is an important part of the wine terroir. This study confirmed that there are rich O. oeni resources with genetic specificity in the wine-making region of Changli. This study offers technical and theoretical support for the development of indigenous starter cultures with regional characteristics.
Screening and Aroma Characteristics of Ester-Producing Yeasts as Starter Cultures for Shanxi Aged Vinegar
CHEN Jia, XING Xiaoying, FENG Zhihong, WANG Rufu
2019, 40(16):  144-151.  doi:10.7506/spkx1002-6630-20180822-242
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The purpose of this study was to select starter cultures for the production of Shanxi aged vinegar. We isolated 3 ester-producing yeast strains from fermented grains used in the traditional fermentation process of Shanxi aged vinegar. Two of them were identified as Candida ethanolica, while the remaining one as Pichia manshurica (named as Y14) by morphological characterization and sequence analysis of the 26S rDNA D1/D2 domain. These yeast strains were used in the production of Shanxi aged vinegar, and the resultant vinegar products was subjected to ester composition analysis using headspace-solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) and sensory evaluation. The results showed that the concentrations of total ester and ethyl acetate in the vinegar fermented by a mixture of P. manshurica Y14 and Daqu (a Chinese traditional fermentation starter used in vinegar production) were increased by 40.5% and 1.3 times compared with the control group. The vinegar was richer esters and flavor components. P. manshurica Y14 shows promise for use as a new starter culture for Shanxi aged vinegar.
Composition Analysis
Optimization of Sample Pretreatment and Chromatographic Separation Conditions for Identification of Goat Milk Oligosaccharides by Ultra Performance Liquid Chromatography-Q-Exactive Focus Tandem Mass Spectrometry
ZHANG Yan, LU Jing, ZHANG Shuwen, PANG Xiaoyang, WANG Junhui, Lü Jiaping
2019, 40(16):  152-159.  doi:10.7506/spkx1002-6630-20181008-039
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Four different sample pretreatment procedures, sequential chromatography on Sep-Pak C18 and graphitized carbon columns, ultrafiltration, dialysis and Sephadex-G10 gel column chromatography, were used to purify oligosaccharides to remove lactose from crude extracts. Ion exchange chromatography was used to determine the removal of lactose and the loss of oligosaccharides. The Sephadex-G10 method was shown to be the best of the four methods. Oligosaccharides in goat milk were identified and structurally analyzed by ultra performance liquid chromatography-Q-Exactive Focus tandem mass spectrometry. The total ion current (TIC) chromatogram was recorded, and based on it, the gradient elution program was determined as follows: 0–20 min, 95%–78% A (acetonitrile); 20–35 min, 78%–73% A; 35–38 min, 73%–62% A; 38–45 min, 62%–50% A. A significantly larger number of oligosaccharides were identified in the samples purified by gel filtration chromatography than the crude extract samples. The oligosaccharide isomers in goat milk were separated effectively under the optimal chromatographic conditions. This method could be considered as an important tool for structural analysis of goat milk oligosaccharides.
Effect of Different Processing Stages on Flavor Components of Shanghai Smoked Fish Made from Grass Carp
XUE Yongxia, ZHANG Zuoqian, ZHANG Hongcai, ZHANG Ju, WEI Saichao, CHEN Shunsheng
2019, 40(16):  160-168.  doi:10.7506/spkx1002-6630-20180914-151
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To investigate the effect of different processing stages on flavor components of Shanghai smoked fish, we employed high performance liquid chromatography (HPLC), an amino acid auto-analyzer and gas chromatography-mass spectrometry (GC-MS) to analyze and identify the flavor components of samples obtained at five processing stages (fresh grass carp, marination, frying, marination followed by frying, and marination followed by frying and then marination again). The results showed that the content of inosine monphosphate (IMP), a main umami nucleotide, kept increasing during processing and the same was true of the contents of free amino acids and taste amino acids, with significant differences being observed among stages. Aspartic acid and glutamic acid had the greatest influence on the flavor of Shanghai smoked fish. In addition, a total of 36, 75, 34, 73 and 78 volatile components were detected in five processing stages mentioned above, respectively, which were mainly composed of aldehydes, ketones, alcohols and hydrocarbons. Therefore, marination and frying mainly contributed to the flavor formation of Shanghai smoked fish.
Identification of Chemical Constituents of Methanol Extract of Cimicifuga dahurica by Ultra Performance Liquid Chromatography Coupled with Quadrupole-Time of Flight-Tandem Mass Spectrometry
Lü Hong, WANG Xiaoming, LIU Xiaomei, ZHANG Fan, WANG Xianrui, GUO Yaqing, PAN Guixiang
2019, 40(16):  169-176.  doi:10.7506/spkx1002-6630-20180928-320
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Objective: To identify the chemical components of the methanol extract from Cimicifuga dahurica. Methods: High-resolution mass spectrometric data of the extract were collected by ultra performance liquid chromatography coupled with quadrupole-time of flight-tandem mass spectrometry (UPLC-Q-TOF-MS). Through molecular feature extraction (MFE), Masshunter software was then used to process the original MS data. Several candidate compounds that may be derived from C. dahurica were obtained. Furthermore, the structures of these compounds were speculated according to their MS fragmentation patterns and confirmed by comparison with reference standards. Results: A total of 38 compounds were identified, including phenylpropanoids, saponins, chromones, and nitrogenous compounds. Conclusion: UPLC-Q-TOF-MS can be applied to identify the chemical components of C. dahurica.
Evaluation of Red Sausage Flavor Based on Electronic Nose
2019, 40(16):  177-184.  doi:10.7506/spkx1002-6630-20180923-244
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This study was devised to rapidly and objectively evaluate the flavor of red sausages using an electronic nose. A total of 9 samples of three kinds of sausages were collected from three batches for each and their volatile components were identified using head space solid phase micro extraction (HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS). Both sensory evaluation and an electronic nose were used to evaluate the flavor attributes of sausages. The ability of the electronic nose to differentiate sausages was evaluated by support vector machine (SVM). Relative odor activity value (ROAV) was used to evaluate the critical flavor compounds in different sausages. The volatile components were recognized by principal components analysis (PCA). The correlation between critical flavor components and the electronic nose was established by orthogonal partial least squares discrimination analysis (OPLS-DA). Regression models between the electronic nose and critical flavor compounds and sensory evaluation were established by stepwise regression. According to the SVM results, the electronic nose had good distinguishing ability for different kinds of sausages and different batches of the same kind of sausage. A total of 117 volatile flavor compounds were identified in all the sausages. According to the ROAV, the critical flavor substances in different sausages varied widely. Allyl mercaptan was the only critical flavor substance found in each sausage. PCA showed that different kinds of sausages were significantly different in overall flavor components. Sensory analysis showed that there were differences in the taste and flavor of different sausages, and the smoky and salty tastes were the most i mportant flavors. The OPLS-DA showed that the electronic nose sensor data showed a good correlation with the critical flavor substances; the regression models between the electronic nose and critical flavor substances and sensory attributes (R2 > 0.8, P < 0.01) indicated that the electronic nose could evaluate and predict the flavor of sausage s.
Volatile Compounds in Subcutaneous Fat of Three Brands of Dry-Cured Hams
TAN Yezi, ZHOU Guanghong, XU Xinglian, LIU Yuan, LI Chunbao, ZHANG Danni
2019, 40(16):  185-192.  doi:10.7506/spkx1002-6630-20180725-304
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This study was done to identify the flavor-active volatile compounds and analyze their contributions to the overall flavor of subcutaneous fat of dry-cured hams. The subcutaneous fat samples were collected from Jinhua Jinzi, Xuanwei Puji and Changshou Rugao dry-cured hams of different ages and were analyzed for volatile compounds using an electronic nose and solid phase microextraction (SPME) gas chromatography-mass spectrometry (GC-MS). Results showed that the electronic nose could rapidly distinguish among different aroma profiles of dry-cured hams. Sixty-two volatile compounds were identified by GC-MS. Fifteen volatile compounds, including 3-methylbutanal, hexanal, heptanal, octyl aldehyde, (E)-2-heptenal, nonanal, (Z)-2-octenal, 2-nonenal, 6-nonenal, (Z,Z)-2,4-decadienal, 1-octen-3-one, 1-octen-3-ol, ethyl 2-methylbutyrate, 2-n-pentylfuran and 2-ethylfuran, were determined as the key aroma contributors by relative odor activity value (ROAV). Principal component analysis indicated that good discrimination among different flavors of subcutaneous fat was achieved on the basis of these aroma compounds.
Differences in Taste Components in By-products of Chilled Large Yellow Croaker (Pseudosciaena crocea)
ZHOU Fen, ZHANG Yanxia, ZHANG Long, ZHANG Caixia, JIANG Jiwei, TAO Ningping, WANG Xichang
2019, 40(16):  193-199.  doi:10.7506/spkx1002-6630-20181008-034
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In order to make efficient use of fish processing by-products and to improve their added value, in this study, we investigated 7 by-products of chilled large yellow croaker (Pseudosciaena crocea). Firstly, the differences in the basic nutrients of the 7 by-products were evaluated. Secondly, the differences in overall taste profile were determined by electronic tongue, and the contents of free amino acids and flavor nucleotides were also measured. The results showed that minced muscle, head meat, roes and fish scales all had the characteristics of high protein and low fat. Principal component analysis (PCA) combined with discriminant factor analysis (DFA) could effectively distinguish among the seven by-products. Seventeen free amino acids were detected in all by-products except fish scales. The value of IMP in these by-products showed a taste activity value (TAV) greater than 1, and the TAV values of minced meat and head meat reached 18.27 and 16.51, respectively. The above results showed that there were some differences in the types and amounts of taste components in different by-products of P. crocea, which contributed to the overall flavor of P. crocea. These results could provide a useful theoretical foundation for further exploitation and development of P. crocea by-products.
Dynamic Changes of Main Quality Components during Yellow Tea Processing
ZHANG Jiao, LIANG Zhuangxian, ZHANG Tuo, LI Zongqiong, ZHU Jingjing, ZHANG Pengcheng, XIAO Wenjun
2019, 40(16):  200-205.  doi:10.7506/spkx1002-6630-20181004-015
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One fresh leaf with one bud from the Bixiangzao tea cultivar harvested in summer were made into yellow tea by the conventional process, sequentially involving spreading, fixation, rolling, piling and drying. This study aimed to explore the dynamic changes of the main quality components during yellow tea processing for the purpose of providing useful information for improvement of the current yellow tea processing technology and its quality. The contents of tea polyphenols, catechins, amino acid, water extract, soluble sugar, caffeine and flavonoids were detected in samples from 11 representative processing points. At the same time, sensory evaluation and aroma quality components were analyzed. The results showed that during the processing of yellow tea, the contents of tea polyphenols, total catechins, water extract, soluble sugar, caffeine and flavonoids decreased gradually, which were 30.12%, 24.08%, 10.97%, 61.34%, 33.20% and 25.55%, respectively lower in dried tea than in fresh tea leaves. By contrast, the content of free amino acid increased by 19.46% compared with fresh tea leaves and the contents of tea polyphenols, caffeine, flavonoids and amino acid similarly increased during the spreading process. The relative contents of alcohols, ketones, olefins and esters in dried tea were reduced by 17.18%, 5.51%, 5.77% and 2.10%, respectively, compared with fresh tea leaves, while the relative contents of aldehydes and phenolic compounds were increased by 35.35% and 4.06%, respectively. Among the processing steps, the taste quality of yellow tea was mainly influenced by spreading and piling. The contents of amino acids were increased with the extension of spreading time, and the piling process could convert ester catechins into simple catechins and produced theaflavin at the same time, the main contributors to the formation of yellow tea’s alcohols, refreshing taste and “yellow soup and yellow leaves” quality. The taste quality was better when the piling time was 8 h; the aroma quality was mainly impacted by the spreading, piling and drying process.
A Comparative Analysis of Functional Components and Nutritional Values of Female and Male Hippocampus erectus and H. trimaculatus
YAN Zhenzhen, ZHANG dong, LIN Tingting, LIU Xin, XIAO Dongxue, GUO Quanyou
2019, 40(16):  206-212.  doi:10.7506/spkx1002-6630-20180920-234
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We determined and compared the contents of nutritional and functional ingredients in males and females from two major seahorse species, Hippocampus erectus and H. trimaculatus, and we also evaluated their nutritional values. The results showed that: 1) the major component of the seahorses was crude protein (on a dry mass basis), which averaged at (60.61 ± 2.83)%, and the crude fat (on a dry mass basis) was relatively lower with an average of (3.04 ± 0.26)%, no significant differences being seen between the genders within a species; 2) the male and female seahorses were similar in amino acid composition, of which the seven essential amino acids were slightly lower as compared with the FAO/WHO recommended pattern. Within a species, the amino acids score, chemical score and essential amino acid index of the females were higher than those of the males. We also found the limited amino acids, including valine, isoleucine, methionine and cysteine, in the seahorses; 3) the fatty acid compositions in the seahorses were consistent regardless of gender, and the total contents of saturated fatty acids, monounsaturated fatty acids and polyunsaturated fatty acids (PUFA) of the females were significantly higher than those of the males within a species. The ratios of n-6/n-3 PUFA of the two species were 0.14–0.18, and they were n-3 PUFA-rich food. The indexes of atherosclerosis and thrombosis were significantly higher than those in the Eskimo diets, which are considered as healthy food for preventing coronary heart disease; 4) the contents of cholesterol and hypoxanthine in the female seahorses were significantly higher than those in the males, while the uridine content in the females was lower than in the males. These results indicate that H. erectus and H. trimaculatus can be used as superior sources of protein and n-3 PUFA. In addition, the gender difference in the contents of nutrients and main functional components (e.g. cholesterol and hypoxanthine), suggests that monosex culture may be a good practice in seahorse aquaculture.
Geographical Origin Traceability and Varietal Classification of Zanthoxylum Based on Mineral Profile
WU Zhen, LI Hong, YANG Yong, TAN Hongjun, ZHAN Yong, JIA Fengxia, LI Xiaobin, WANG Fuqiang
2019, 40(16):  213-219.  doi:10.7506/spkx1002-6630-20181008-029
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The concentrations of 21 mineral elements (Al, B, Ba, Ca, Cd, Co, Cu, Na, K, Fe, Mg, Mn, Zn, Ni, Pb, As, Se, Hg, Cr, V and Sr) of 80 Zanthoxylum samples collected from 9 main producing regions in China (Z. bungeanum Maxim: Hancheng in Shaanxi, Hanyuan in Sichuan, Maowen in Sichuan and Wudu in Gansu; Z. schinifolium Sieb. et Zucc: Zhaotong in Yunnan, Guanling in Guizhou, Jinyang in Sichuan, Hanyuan in Sichuan, and Jiangjin in Chongqing) were determined by principal component analysis (PCA) and partial least squares-discrimination analysis (PLS-DA) were used to analyze the data obtained. The 80 samples were classified into nine groups by PCA and PLS-DA, agreeing with the actual grouping. The classification ability of PLS-DA was better than that of PCA and could effectively distinguish between Z. bungeanum Maxim. and Z. schinifolium Sieb. et Zucc. This study demonstrated that the combination of multi-element analysis and PLSDA can be an effective tool for identifying the geographical origin and variety of Zanthoxylum.
Changes in Volatile Components of Coix Seed Oil during Accelerated Oxidation Analyzed by Solid Phase Microextraction-Gas Chromatography-Mass Spectrometry and Electronic Nose
ZHAO Zewei, DING Zhuhong, GU Yuanting, DING Xiaojuan
2019, 40(16):  220-226.  doi:10.7506/spkx1002-6630-20180917-176
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The dynamic changes of flavor compounds during the oxidation of coix seed oil were analyzed by solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) and an electronic nose. The results showed that the characteristic volatile flavor compounds detected during the accelerated oxidation of coix seed oil were mainly aldehydes, ketones and alcohols. (E)-2-Nonenal, (E,E)-2,4-decadienal, (E)-2-decenal, (E,Z)-2,6-nonadienal, 1-octen-3-one, and decanal were the key flavor compounds of fresh coix seed oil, responsible for the grassy, oily, and watermelon-like smell of the oil. The deterioration of oil quality became more serious with the increase in oxidation time. The relative content of aldehydes was 73.815% after accelerated oxidation at 60 ℃ for 30 days, and the relative contents of small aldehydes, acids and alcohols were increased as compared with fresh oil. The key flavor compounds that were newly found in the accelerated oil included the newly added nonanal, octanal, hexanal, and (E)-2-octenal, which had a rancid odor due to the present of these compounds. Linear discriminant analysis (LDA) of the electronic nose data clearly distinguished the fresh oil from the oxidized oil, as well as between flavors in the early and late stages of oxidation. The characteristic compounds of fresh coix seed oil included (E)-2-nonenal, and (E,E)-2,4-decadienal. Small molecules, including nonanal, octanal, and hexanal, were the characteristic volatile compounds after accelerated oxidation of coix seed oil.
Comparative Nutrient Composition of Seed Oils of Wild Camellia oleifera with Different Single Kernel Masses Grown in Ten Regions
CHEN Xiaolu, CHEN Baiying, WANG Mei, LI Jing, ZOU Yujing, RONG Jun, DENG Zeyuan
2019, 40(16):  227-234.  doi:10.7506/spkx1002-6630-20180925-264
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This study aimed to investigate the differences in the nutrient composition of the seed oils of wild Camellia oleifera with different single grain masses grown in different regions in order to find suitable geographical origins of camellia seeds for oil production and to provide a basis for the introduction and domestication of camellia seeds. Wild camellia seed samples from 10 regions, including Huangshan in Tangkou, Daling village in Huoshan county, Yuanbao Mountain in Rongshui county and Hengkou village in Xianfeng county, were classified into three categories of single grain mass: below 0.35 g, 0.35–0.8 g, and above 0.8 g. The seed oils from these samples were compared for their nutrient composition. The oil contents of all samples were determined by the solvent method to be between 29.9% and 46.11%. A total of 26 fatty acids were detected by gas chromatography (GC). All samples were determined to contain 0.031-0.149 mg/g of α-tocopherol by high performance liquid chromatography (HPLC), 0.056–0.256 mg/g of olefin, 0.166–0.351 g/g of tea saponin by the phenol-sulfuric acid method. From a regional perspective, the oil content of camellia seeds from Mountain Emei was the highest, reaching 43.74%, while the lowest oil content of 32.86% was found in camellia seeds from Daling village. Among the three categories of single grain mass, the average oil content of camellia seeds between 0.35 and 0.8 g was the highest, and those below 0.35 g and above 0.8 g were similar, 36.28% and 36.74%, respectively. Among the 26 fatty acids, oleic acid (71.156%–78.515%) was dominant, followed by palmitic acid (8.091%–12.096%) and linoleic acid (2.621%–10.618%). The content of α-tocopherol was the highest in camellia seeds from Emei Mountain and the lowest in Yuanbao Mountain among the 10 regions. The content of α-tocopherol in camellia seeds below 0.35 g was the highest, followed by those between 0.35 and 0.8 g, and the lowest value was noted in camellia seeds above 0.8 g. The content of squalene in camellia seeds from Daling village was the highest, and the lowest in Banruo village among the 10 regions. The content of squalene in camellia seeds below 0.35 g was the highest, followed by those between 0.35 g and 0.8 g, and the lowest value was detected in camellia seeds above 0.8 g. The content of tea saponin was the highest in camellia seeds from Emei Mountain and the lowest in Huangliantai. The content of tea saponin in camellia seeds above 0.8 g was the highest, followed by those below 0.35 g, and the lowest value was measured in camellia seeds between 0.35 g and 0.8 g. The results showed that the quality of camellia seeds varied among regions and among single grain masses. The oil contents of camellia seeds from Emei Mountain, Banruo Temple and Maoer Mountain were higher. α-Tocopherol and tea saponin were richer in camellia seed oils from Emei Mountain, Banruo Temple and Tangkou, while the contents of squalene in camellia seed oils from Daling village, Huangliantai and Emei Mountain were higher. Camellia seeds with a lower single grain mass contained higher levels of alpha-tocopherol and squalene.
Process and Technology
Optimization of Water Temperature and Salinity for Live Transportation of Grouper
WU Bo, XIE Jing
2019, 40(16):  235-241.  doi:10.7506/spkx1002-6630-20181101-012
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In this work, the effects of water temperature and salinity on transportation stress in live grouper were studied. The response surface methodology (RSM) was used to optimize the two parameters. The results showed that different severities of stress reaction in grouper could be induced by different transportation temperatures with the highest survival rate occurring at 15 ℃. The concentration of serum cortisol and blood glucose and the expression level of HSP70 at 15 ℃ were significantly lower than those at 21, 27, and 30 ℃. Excessively lower (5‰) or higher salinity (40‰) could induce acute stress reaction in grouper, leading to injury or even death. The survival rate at 20‰ salinity was significantly higher than at the other salinity levels, whereas the concentration of blood glucose was significantly lower at 20‰ salinity. Besides, the concentration of serum cortisol and the expression level of HSP70 in at 30‰ were significantly lower than at the other salinity levels, while the suitable salinity range reduced the stress response of fish. The optimum water temperature and salinity were 16 ℃ and 26‰, respectively, as determined by a combination of single factor method and response surface methodology. In experiments conducted under these conditions, the serum cortisol level was (15.83 ± 1.07) ng/L, and the blood glucose concentration was (1.93 ± 0.17) mmol/L.
Preparation, Characterization and in Vitro Release Characteristics of Sustained-Release Chitosan Microcapsules Containing Tea Tree Oil
LONG Men, FENG Chao, LI Yongjia, WANG Xuhai, CAI Huazhen, ZHAN Ge
2019, 40(16):  242-248.  doi:10.7506/spkx1002-6630-20181010-077
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In this experiment, chitosan (CS) microcapsules containing tea tree oil (TTO) were prepared using sodium tripolyphosphate (TPP) as the crosslinking agent by the ionic gelation method. The structure, functional properties and release profiles in different food model systems of the microcapsules were analyzed. The results showed that the encapsulation efficiency was strikingly affected by TTO concentration and mass ratio between CS and TPP. The optimized values of the two parameters were 11.30 mg/mL and 5.3:1, respectively, which resulted in a minimum particle size of (0.74 ± 0.03) μm and a maximum encapsulation efficiency of (53.15 ± 0.32)%. The particle size of the microcapsules obtained under these conditions was normally distributed in the range of 0.2–2.3 μm, and the stability of TTO was significantly improved by the encapsulation. The antimicrobial and antioxidant effects of the microcapsules were more stable for 15 d than TTO. In different food model systems, the microcapsule powder was rapidly released, and reached a stable sate after 30 minutes. Therefore, this process can be used for microencapsulation of tea tree oil to improve its stability.
Safety Detection
Prediction of Acrylamide Content in Fried Battered and Breaded Fish Nuggets Using Artificial Neural Network
SHAN Jinhui, CHEN Jiwang, LIU Yan, WANG Haibin, XIA Wenshui, Youling L. XIONG
2019, 40(16):  249-255.  doi:10.7506/spkx1002-6630-20180607-093
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In this paper, the prediction of acrylamide contents in fried battered and breaded fish nuggets (BBFNs) was performed through the combination of response surface methodology (RSM) and back propagation artificial neural network (BP-ANN). RSM was utilized to collect the experimental data and a BP-ANN model was established to predict the changes in acrylamide content in BBFNs during deep-fat frying, where the ratio of xanthan gum to soybean fiber, drying time of BBFNs, soybean oil quality, frying temperature and time were considered as the input while acrylamide content was regarded as the output. Furthermore, the training set was used for model fitting and the test set was used to evaluate the prediction ability of the model. The results showed that the acrylamide content in fried BBFNs was obviously affected by the ratio of xanthan gum to soybean fiber, drying time of BBFNs, frying temperature and time. However, the quality of soybean oil had no significant influence on the acrylamide content in fried BBFNs. A correlation coefficient (R) of 0.997 for the ANN model after training was presented, indicating that the model is notably fitted and has a good approximation ability. Moreover, the model had slight prediction errors for new data with a maximum relative error of 5.34% and a minimum relative error of 0.12%, suggesting accurate prediction of the acrylamide content in fried BBFNs using BP-ANN.
Rapid Electrochemical Determination of Furan in Food
CHAI Xiaoling, HAO Yaru, LI Shuguo
2019, 40(16):  256-260.  doi:10.7506/spkx1002-6630-20180913-128
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The electrochemical properties of furan were investigated. On this basis, we developed a rapid electrochemical method for the determination of furan in food. The cyclic voltammetry showed that a well-defined oxidation peak was observed at 1.80 V but no reduction peak appeared, indicating that the electrochemical reaction of furan is irreversible. The experimental conditions were optimized with differential pulse voltammetry as follows: acetonitrile as solvent, potential increment 0.005 V, pulse interval 0.3 s, and electrolyte concentration 0.15 mol/L. The oxidation peak current (Ip) had a good linear relationship with furan concentration (Cfuran) in the range of 2 × 10-6–6 × 10-5 mol/L, which was fitted as follows: Ip = 0.046 6Cfuran + 0.565 (R2 = 0.996 8), and the limit of detection (LODs) of the proposed method was 0.55 μmol/L (RSN = 3). The presence of furan in different foods was quantified by this method, and the average recoveries for spiked samples were in the range of 94.60%–98.41%. The detection results well agreed with those obtained with gas chromatography-mass spectrometry (GC-MS). With the characteristics of simple sample preparation, simple operation and rapid detection, this method is useful for rapid determination of furan in food samples .
Simultaneous Determination of Free Gossypol and Its Degradation Product Tetramethoxy Gossypol in Commercially Available Cottonseed Oil by High Performance Liquid Chromatography
ZHOU Mengyu, Gulisitan·ABULAITI, YAO Jun, CHEN Ling
2019, 40(16):  261-266.  doi:10.7506/spkx1002-6630-20180926-282
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This study aimed to establish a high performance liquid chromatography (HPLC) method for the determination of free gossypol and its degradation product tetramethoxy gossypol in commercially available cottonseed oil in order to provide a scientific basis for quality control of cottonseed oil. The chromatographic separation was accomplished on an Inertsil? ODS-3 column (250 mm × 4.6 mm, 5 mm) using a mobile phase comprised of methanol and 2% phosphoric acid (85:15, V/V) at a flow rate of 1.0 mL/min, and the column temperature was set at 32 ℃. The detection wavelength was 235 nm, and the injection volume was 10 mL. Good linear relationship was achieved for gossypol in the concentration range of 0.245–1.226 mg/mL (r = 0.999 5). The relative standard deviation (RSD) of precision and repeatability was 0.88% and 1.73% (n = 6), respectively. The average recovery was 101.2%, with RSD of 1.75% (n = 3). The method also showed a good linear relationship for tetramethoxy gossypol in the concentration range of 0.211–1.056 mg/mL (r = 0.999 6). The RSD of precision and repeatability was 1.56% and 1.11% (n = 6), respectively. The average recovery was 100.3%, with RSD of 1.12% (n = 3). Free gossypol was detected in 25 out of 90 batches of commercially available cottonseed oils in the range of 0.159– 1.661 mg/mL, and tetramethoxy gossypol in 56 in the range of 0.093–1.661 mg/mL. This method displayed good accuracy, high precision and easy operation and could be widely used to monitor the detoxification of cottonseed oil.
Identification of Heterologous Species in Donkey-Hide Gelatin Based on Specific Peptides
FANG Fang, ZHANG Jiukai, MA Xueting, SU Min, CHEN Ying
2019, 40(16):  267-273.  doi:10.7506/spkx1002-6630-20180927-293
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This study aimed to identify animal glue in adulterated donkey-hide gelatin. We applied bottom-up proteomics to find and identify characteristic thermostable peptides from different species. Firstly, we found the characteristic peptides from three animal glues (donkey-hide gelatin, pig-hide gelatin and bovine-hide gelatin). At the same time, we also found that the thermostable specific peptides containing no hydroxyproline from the three species were located at similar positions in the α1 sequence of type I collagen. By investigating the sequence characteristics of collagen-derived species-specific peptides, we speculated the cleavage pattern of collagen during the industrial processing of donkey-hide gelatin. Secondly, two characteristic peptides of horse skin, derived from equine keratin and unnamed equine protein, respectively, were used to discriminate horse hide glue from donkey-hide gelatin. In addition to discrimination between donkey-hide gelatin and heterogeneous animal skin glue, this study also provides technical support for the authenticity identification of donkey-hide gelatin and the discovery of more specific peptides from collagen.
On-Line Detection of Mildew Degree of Maize Based on Spectral and Image Information Fusion
SHEN Fei, HUANG Yi, ZHOU Yuechun, LIU Qin, PEI Fei, LI Peng, FANG Yong, LIU Xingquan
2019, 40(16):  274-280.  doi:10.7506/spkx1002-6630-20180619-355
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This work aimed to establish an on-line method for the detection of the mildew degree of maize based on data fusion of visible/near infrared (Vis/NIR) spectroscopy and machine vision technique. Irradiation-sterilized maize kernel samples were inoculated with spore suspensions of 5 different fungal strains, separately. Then the samples were stored in an artificial climate box (28 ℃ and 85% relative humidity) for 15 d until serious mildew occurred. After 0, 6, 9, 12 and 15 d, the characteristic spectral and image information of maize samples were collected online. Both spectral features and image color features were extracted and fused for the development pf qualitative and quantitative analysis models. The results showed that principal component analysis (PCA) could distinguish maize samples according to different mildew degrees. The overall recognition rate obtained by linear discriminant analysis (LDA) for the classification of samples with different mildew degrees was 91.1% based on spectral and image data infusion, which were 4.4% and 8.9% higher than single spectral and image information, respectively. The prediction of colony counts in maize samples using the partial least squares regression (PLSR) based on information fusion was also better and the coefficient of determination for the prediction set (Rp 2), root mean square error of prediction (RMSEP) and residual predictive deviation (RPD) value obtained were 0.894 1, 0.665 (lg(CFU/g)) and 3.06, respectively. These results indicated that spectral and image data fusion could improve the model precision and was feasible in on-line detection of fungal contamination levels in maize. In further studies, naturally infected maize samples and samples contaminated with more representative fungal strains should be considered to enhance the robustness and applicability of the calibration model.
Application of DNA Barcoding in Detection of Starch Adulteration
CHEN Jia, WANG Shuang, ZHOU Wei, ZHANG Yan, SANG Yaxin
2019, 40(16):  281-285.  doi:10.7506/spkx1002-6630-20180611-159
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This study reported on the application of plant DNA barcoding technique to detect adulteration of starch and starch products. Genomic DNA samples were extracted from alfalfa, potato, cassava, sweet potato and maize and were used as templates for PCR amplification with the universal primers ITS2, matK, rbcL and trnH-psbA. The sequences were aligned using the basic local alignment search tool (BLAST) with those deposited in the GenBank database. The identification abilities of 4 DNA fragments were compared by success rate. Five starch samples and 4 vermicelli samples we collected were detected using the group of ITS2 + trnH-psbA with higher efficiency.
Effect of Change in Chloride Ion Content on the Contents of 3-Chloropropanol Ester and Glycidyl Ester during Corn Oil Refining
LIU Yulan, WANG Luyang, HUANG Huina, WANG Manyi, AN Jun
2019, 40(16):  286-292.  doi:10.7506/spkx1002-6630-20180731-373
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In this study, the contents of chloride, 3-monochloro-1,2-propanediol ester (3-MCPD ester) and glycidyl esters (GEs) in crude, decolorized but undeodorized corn oil and refined oil from corn oil processing plants in Anhui, Hebei and Shandong provinces were detected. The crude corn oil was refined under laboratory conditions that can be definitely controlled, and the contents of chloride, 3-MCPD ester and GEs in the refining process were detected and compared with those obtained from oil processing plants. By doing so, we aimed to examine the change of chloride ion content during corn oil refining and its effect on the contents of 3-MCPD ester and GEs. The results showed that all the corn oil samples tested contained chloride ion, 3-MCPD ester and GEs, among which the highest content of chloride ion of 0.628–2.029 mg/kg was found in the crude oil. The contents of 3-MCPD ester and GEs in the crude oil were 0.547–1.083 mg/kg and 0.246–0.721 mg/kg, respectively; the content of chloride ion in the decolorized but undeodorized corn oil was 0.110– 0.374 mg/kg, which was significantly lower than that in the crude oil, and the contents of 3-MCPD ester and GEs were 0.933–1.422 mg/kg and 0.246–0.432 mg/kg, respectively, which were higher than and similar to those in the crude oil, respectively. After deodorization, the contents of 3-MCPD ester and GEs increased markedly to 3.523–4.541 and 1.501– 13.584 mg/kg, respectively, and a maximum increase of 4.5- and 33.1-fold in them was observed in one sample, as well as a maximum decrease in chloride ion content (0.287 mg/kg). The analysis of corn oil samples refined in our laboratory and in the plants consistently showed that the chloride ion content decreased during the refining process, and maximum decrease of 76.1%–81.3% occurred at the stages of hydration degumming and alkali deacidification. By contrast, the contents of 3-MCPD ester and GEs did not change much after hydration degumming, alkali deacidification and adsorption decolorization processes, while they increased greatly after deodorization, accompanied by a decrease in chloride ion content, and a larger reduction in chloride ion content led to a greater increase in 3-MCPD ester content. This study provides a useful guideline to prevent and control the risks of 3-MCPD esters and GEs during corn oil refining and even the production of other vegetable oils.
Development of Certified Reference Materials for Xinyang Maojian Tea Grading Based on HPLC Fingerprints of Flavor Components
WANG Shuhui, CAO Xueli, SONG Shasha, LONG Limei
2019, 40(16):  293-301.  doi:10.7506/spkx1002-6630-20181102-025
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A method of developing tea reference materials (RMs) to be used in tea grading based on fingerprint classification was established in this paper, and three grades (120 samples, 50 g each) of Xinyang Maojian tea certified reference materials (CRMs) were developed. Tea infusion samples were prepared according to the national standard, and then analyzed by HPLC for flavor ingredients. A newly improved extent similarity method was used for calculation of fingerprint similarity. On the basis of the fingerprint similarity, the homogeneity and stability of the tea RMs were tested and similarity values were certified by eight laboratories according to the guidelines for CRMs. The results indicated that each grade of samples had good homogeneity and stability. The fingerprint similarity value and uncertainty at 95% confidence level were certified as 0.918 ± 0.027, 0.662 ± 0.033, and 0.400 ± 0.074 for grades I, II and III, respectively, and the grading was consistent with sensory evaluation. This set of tea CRMs has been certified and issued by the National Technical Committee on Reference Materials as China’s first tea CRM based on the fingerprint classification with quantitative characteristics. This method can be used for grading of Xinyang Maojian tea.
Determination of Mineral Oil-Saturated Hydrocarbons in Paddy and Rice by On-Line High Performance Liquid Chromatography-Gas Chromatography
LIU Lingling, LI Bingning, OUYANG Jie, WU Yanwen
2019, 40(16):  302-307.  doi:10.7506/spkx1002-6630-20180627-498
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A method based on on-line high performance liquid chromatography-gas chromatography (HPLC-GC) was proposed for the determination of mineral oil-saturated hydrocarbons (MOSH) in paddy and rice. Firstly, the MOSH in samples were extracted with n-hexane. The extract was then purified using activated aluminum oxide to remove alkanes from it, concentrated and injected into the HPLC system. The MOSH fraction separated was transferred into the GC system by “heart-cut” technique and detected by a hydrogen flame ionization detector (FID). Under optimized analysis conditions, the calibration curve established using paraffin oil as reference standard displayed a good linearity within the range of 0.5–100 mg/L with a correlation coefficient of 0.999. The quantification limit (LOQ) of the method was 0.05 mg/kg. The recoveries for spiked samples ranged between 89.1% and 91.4% with relative standard deviation (RSD) of 4.6%–5.5%. The MOSH contents of 24 real samples ranged from 0.30 to 2.30 mg/kg as determined by this method.
Establishment and Application of a Closed Culture Method for Enumeration of Molds
HAN Tao, YANG Xueni, ZHANG Fang
2019, 40(16):  308-313.  doi:10.7506/spkx1002-6630-20180611-168
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In the present study, we focused on the growth dynamics of Aspergillus niger under-micro oxygen stress to develop a closed culture method for the detection of this mold in foods. A comparative analysis was made to explore the feasibility and practicality of the culture method. The results showed that there was no significant difference between the closed culture and the traditional open culture. Therefore, the closed culture method featuring the parameter of volume ratio between air and medium equal to or more than 3 could be used to determine mold counts in foods in place of the traditional open culture method, so as to overcome the problems of mold spore diffusion and pollution.
Recognition of Dumplings with Foreign Body Based on X-Ray and Convolutional Neural Network
WANG Qiang, WU Kai, WANG Xinyu, SUN Yu, YANG Xiaoyan, LOU Xiaohua
2019, 40(16):  314-320.  doi:10.7506/spkx1002-6630-20180612-180
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Foreign bodies in quick-frozen dumplings can seriously endanger consumers’ physical and mental health. However, the traditional metal detector can only detect metals and the results cannot be visualized intuitively. Motivated by this problem, in this study, we developed a method of recognizing foreign bodies dumplings with based on LeNet convolutional neural network (CNN) model, which can detect X-ray images of dumplings containing five foreign bodies, including metal balls, wires, screws, stones, and glasses. Firstly, X-ray images of dumplings without foreign bodies and those with foreign bodies were obtained and processed by denoising and contrast stretching transformation. Secondly, the CNN model was optimized, trained and validated using batch normalization (BN) method and Softmax linear regression classifier with ReLu as the activation function and Max-Pooling as the down-sampling method. The trained network model was applied to test 100 dumpling images without foreign bodies and 100 ones with foreign bodies. The experimental results showed that the recognition method could accurately identify the foreign body-containing dumplings with a recognition rate of up to 99.78%. Finally, the traditional texture features of local binary pattern (LBP), histogram of oriented gradient (HOG) and Gabor were extracted and used as the feature vectors for identifying dumpling images with and without foreign objects by using back propagation (BP) neural network, support vector machine (SVM), K-nearest neighbor (KNN) classifier, AdaBoost classifier, Naive Bayes classifier and decision tree classifier. The results were compared with those obtained with the network model, which verified the superiority of the algorithm and the effectiveness of the extracted features. This research provides a new approach for the detection of foreign bodies in food so as to ensure food safety.
Determination of VB12 in Formula Foods by High Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry
LIU Jie, GONG Lei, ZHU Xiaoling, PENG Qingzhi, ZHANG Li, ZHOU Taohong, JIANG Feng, HUANG Qian, ZHANG Xiaoling
2019, 40(16):  321-326.  doi:10.7506/spkx1002-6630-20180920-223
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A method based on high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS) was developed for determination of VB12 in formula foods. The sample pretreatment was performed followed by purification using an HLB solid phase extraction column, and then the analyte was separated on a C18 reversed phase column by isocratic elution using a mobile phase consisting of methanol and 8 mmol/L ammonium acetate aqueous solution (19:81, V/V). VB12 was determined indirectly by measuring cobalt ions in samples by ICP-MS. The results showed that the analysis could be completed within 7 min, and the target compound exhibited a good peak shape. A good linearity was obtained in the range of 0.1–500 μg/L for VB12 with a correlation coefficient of 0.999. The limit of detection (LOD) was 0.02 μg/kg. The average recoveries of the method ranged from 81.3% to 103.6% with relative standard deviations of 0.4% to 4.6% for different food matrixes at three spiked levels (n = 6). The method is simple, fast and sensitive with strong resistance to matrix interference and wide dynamic range. It is applicable to various formula foods.
Fingerprinting of Organic Acids by High Performance Liquid Chromatography for Authentication of Sweet Cherry Juice
LI Jiaxiu, ZHANG Chunling, LIU Hui, CHEN Dalei, LIU Jiechao, JIAO Zhonggao
2019, 40(16):  327-334.  doi:10.7506/spkx1002-6630-20180913-122
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A high performance liquid chromatographic (HPLC) fingerprint of organic acids in sweet cherry juice was developed by using the software of Similarity Evaluation System for Chromatographic Fingerprints of Traditional Chinese Medicine (Version 2.0). Moreover, based on the fingerprint, similarity analysis, principal component analysis (PCA), and cluster analysis (CA) were used to discriminate whether sweet cherry juice was adulterated with apple juice, pear juice, apricot juice, peach juice, or exogenous citric acid. Results showed that the similarities between the reference fingerprint and those of 42 sweet cherry juice samples were all above 0.948. The fingerprint of sweet cherry juice was well consistent among varieties and harvest times. Adulteration reduced the similarities. All the adulterated juice samples especially at higher adulteration levels could be discriminated from pure sweet cherry juices by using the HPLC fingerprint combined with PCA and CA, while only sufficiently high levels of adulteration could be discriminated by similarity analysis. It is suggested that sweet cherry juice adulteration could be discriminated by HPLC fingerprints combined with chemometrics, which may be useful for the authentication and quality control of sweet cherry juice.
Determination of Eight Illegal Drugs in Internet-Famous Health Foods by Thin-Layer Chromatography Coupled to Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry
CAO Xiaoqin, FANG Zhenfeng, ZHANG Tao, ZHOU Guoyong, CHEN Zhongqiang, SHI Lu
2019, 40(16):  335-342.  doi:10.7506/spkx1002-6630-20190107-097
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A method for the simultaneous determination of 8 illegal drugs in internet-famous health foods was established by thin-layer chromatography (TLC) coupled to ultra performance liquid chromatography-tandem mass spectrometry (TLC-UPLC-MS/MS). The sample pretreatment was accomplished by TLC, and subsequently the chromatographic separation was done on a Kinetex 100 RP-18 (100 mm × 2.1 mm, 1.6 μm) column with gradient elution using a mobile phase consisting of 1 mmol/L ammonium acetate solution (with 0.1% acetic acid) and acetonitrile. The multiple reaction monitoring (MRM) mode was used to quantify 8 illegal drugs, sibutramine, lovastatin, simvastatin, ephedrine, caffeine, phenolphthalein, phenformin and sildenafil. The results showed that good linear relationships in the range of 0.5–100 μg/L were observed for all of the analytes with correlation coefficients no less than 0.995 8. The limits of detection (LODs) and limits of quantification (LOQs) ranged from 0.09 to 0.29 μg/kg and from 0.31 to 0.79 μg/kg, respectively. The average recoveries for various samples were in the range of 67.3%–101.1%, and the relative standard deviations for six replicate determinations were no more than 16.5%. Totally, 23 out of 45 samples were identified to contain the illegal drugs. The established method can be suitable for rapid screening and quantification of these 8 illegal drugs in internet-famous health foods.
Determination of Five Biogenic Amines in Northeast Farmhouse Soybean Paste by High Performance Liquid Chromatography
HAO Yu, SUN Bo, ZHANG Yu, MA Yiying, XIE Shuangyu, LI Tianyi
2019, 40(16):  343-349.  doi:10.7506/spkx1002-6630-20180626-486
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In this study, we established a precolumn derivatization-high performance liquid chromatography (HPLC) method and applied it to determine biogenic amines in farmhouse soybean paste from northeastern China. Biogenic amines from samples were extracted with 5% trichloroacetic acid and were precolumn derivatized with dansyl chloride after defatting with n-hexane. A C18 (250 mm×4.6 mm, 5 μm) column was used for the chromatographic separation. Gradient elution was carried out with a mixture of methanol and water at a flow rate of 0.8 mL/min. The biogenic amine content was measured at a wavelength of 254 nm. The results showed that five biogenic amines (histamine, tyramine, β -phenylethylamine, putrescine, and spermidine) from the soybean paste were well separated within 40 min. The linear range for the analytes was 1–50 mg/kg, with correlation coefficients (R2) ≥ 0.99. The detection limits (LODs, RSN = 3) were 0.02–0.06 mg/kg, and the relative standard deviation (RSD) was less than 5%. The average recoveries of the biogenic amines from spiked samples at three concentration levels of 5.0, 10.0 and 15.0 mg/L were between 82% and 105%. The method had a wide linear range, good repeatability and high accuracy, and could allow for quick and simple detection of biogenic amines in northeast farmhouse soybean paste.