Table of Content

25 May 2019, Volume 40 Issue 10
Food Chemistry
Comparison of in Vitro Digestion of Lycopene Nanoemulsions Stabilized with Different Macromolecular Emulsifiers
HONG Zehan, WU Wanyi, LI Lu, LI Yan, XIE Xin’an
2019, 40(10):  1-7.  doi:10.7506/spkx1002-6630-20180619-369
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The in vitro digestion characteristics of lycopene nanoemulsions stabilized with three different emulsifiers: octenyl succinic anhydride (OSA)-modified starch, whey protein isolate (WPI) and sodium caseinate (SC) were studied. The results showed that the droplet size, zeta potential and microstructure of the nanoemulsions during digestion mainly depended on emulsifier type. Each nanoemulsion was digested in both simulated gastric and intestinal fluid, leading to droplet aggregation, increased emulsion droplet size and minimal zeta potential. The release rate of free fatty acid from these lycopene nanoemulsions followed the decreasing order: OSA-modified starch (92.25%) > SC (86.53%) > WPI (79.88%), which was higher than that (48.7%) of the control group. This indicates that the incorporation of lycopene into nanoemulsions could improve its digestion characteristics effectively. The nanoemulsions stabilized with OSA modified starch showed higher lycopene bioavailability (25.60 ± 3.08)% than those stabilized with protein emulsifiers.
Functional and Structural Properties of Micronized Dietary Fiber Powder Extracted from Peel and Pomace of Jincheng Sweet Oranges (Citrus sinensis (L.) Osbeck cv. Jincheng)
YI Tian, CUI Wenwen, WANG Mingrui, YAO Jingjing
2019, 40(10):  8-14.  doi:10.7506/spkx1002-6630-20180615-330
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The peel and pomace of Jincheng sweet oranges were used to prepare dietary fiber (DF). Ordinary and micronized DF powders were obtained using a multi-purpose grinder and a planetary ball mill, respectively. The physicochemical properties and heavy metal adsorption abilities of the DF powders were measured. A Laser particle analyzer, an infrared spectrometer, an X-diffractometer, a thermal analyzer, and a scanning electron microscope were used for particle size measurement and microstructural observation. Our aim was to evaluate the effect of micronization of sweet orange DF on its physicochemical properties, microstructure and heavy metal adsorption ability. Compared with the ordinary powder, the micronized powder had a smaller particle size as well as a lighter color and showed a significant increase in water retention capacity, oil retention capacity, swelling capacity, and adsorption ability toward heavy metal ions (P < 0.05). This experiment provides a theoretical basis for the comprehensive utilization of Jincheng organ peel and pomace as a potential source of food additive.
Effect of Regenerated Cellulose-Whey Protein Isolate Emulsion on the Quality of Emulsified Sausages
ZHAO Yinyu, TIAN Xiaona, ZHOU Guanghong, ZHANG Wangang
2019, 40(10):  15-20.  doi:10.7506/spkx1002-6630-20180314-182
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The purpose of this study was to investigate the effects of regenerated cellulose (RC)-whey protein isolate (WPI) emulsion used as pork back fat replacer (0%, 33%, 66% and 100%) on the proximate composition, color, cooking loss, texture, fatty acid profile, lipid oxidation and dynamic storage modulus (G’) of low-fat emulsified sausages. The results indicated that the emulsified sausages showed a significant reduction in fat content and lipid oxidation (P < 0.05) and a significant increase in lightness (P < 0.05) with increasing percentage of RC-WPI emulsion. The 66% emulsion (T2) group showed a significant reduction in cooking loss (P < 0.05). Dynamic storage modulus (G’) was higher for samples with RCWPI emulsion compared to the control (C). The hardness, springiness and chewiness of the emulsified sausages with 33% (T1) and 66% (T2) emulsion were significantly higher than those of the control (C) (P < 0.05). Emulsified sausages showed a significant increase in polyunsaturated fatty acid content and a significant decrease in saturated fatty acid content with increasing proportion of pork fat replacement by the emulsion (P < 0.05). In conclusion, olive oil emulsion stabilized by RC and WPI as a substitute for pork back fat could effectively improve the quality and fatty acid profile of emulsified sausages.
Preparation and Properties of Corn Starch/Eggshell Powder Composite Film
JIANG Bingxue, LI Shuai, WU Yuanyuan, SONG Jingxin, CHEN Shanshan, LI Xinxin, SUN Huimin
2019, 40(10):  21-28.  doi:10.7506/spkx1002-6630-20180507-099
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A composite film was prepared using corn starch (CS) and eggshell powder (ESP) as the main film-forming substrates. The effects of CS, ESP and glycerol (Gly) concentration on the tensile strength (TS), elongation at break (EB), water vapor permeability (WVP), and oxygen permeability (OP) of CS/ESP film were studied. Principal component analysis method was used to comprehensively evaluate the film properties. The optimum process parameters determined through response surface methodology were as follows: CS 4.9 g/100 mL, glycerol 49%, and ESP 1.9%. The TS, EB, WVP, and OP of the film prepared under the optimized conditions were 4.97 MPa, 109.12%, 1.31 × 10-12 g/(cm·s·Pa) and 1.19 × 10-5 cm3/(m2·d·Pa), respectively. Fourier transform infrared spectroscopic (FTIR) analysis showed that ESP and CS had good compatibility with each other. X-ray diffraction (XRD) and thermogravimetric analysis (TGA) results showed that the addition of ESP improved the crystallinity and thermal stability of CS/ESP film. Scanning electron microscopy (SEM) analysis revealed that the CS/ESP film had a smooth surface and cross-sectional morphology without obvious protrusions and cavities.
Preparation and Properties of Peppermint Oil Nanoemulsions
QI Yuman, XUN Chongrong, CHE Jialing, JIANG Lianzhou, MA Wenjun, ZHANG Xiaoyuan, LI Yang, WANG Zhongjiang
2019, 40(10):  29-35.  doi:10.7506/spkx1002-6630-20180325-327
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In order to overcome limitations of peppermint oil such as high volatility and poor water solubility, peppermint oil nanoemulsions were prepared by high pressure homogenization method using soybean protein-phosphatidylcholine complex as the emulsifier. Based on average particle size, polydispersity index, zeta potential, turbidity, emulsification yield and emulsion stability index, the optimum process parameters were determined as follows: soy protein isolate (SPI) concentration 2.5% (m/m), peppermint oil 5% (m/m), and homogenization pressure 80 MPa. Peppermint oil nanoemulsions with a small average diameter and uniform size distribution were obtained under the optimized conditions as examined by dynamic light scattering and transmission electron microscopy. Analysis by gas chromatography-mass spectrometry (GC-MS) showed that the nanoemulsions could effectively preserve the functional components of peppermint oil; the rheological results showed that the peppermint oil nano-emulsion had good kinetic stability.
Metabonomic Study on the Effect of Transcriptional Factor SlNAC4 on Tomato Fruit Metabolites
ZHENG Haiying, ZHANG Dongqing, ZHAO Xiaodan
2019, 40(10):  36-42.  doi:10.7506/spkx1002-6630-20180925-265
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In this study, SlNAC4 gene-silencing and wild-type tomato fruit were used for metabonomic investigation of tomato fruit metabolites at the breaking stage by using high performance liquid chromatography coupled to high-resolution tandem mass spectrometer (HPLC-HRMS/MS) in order to evaluate the effect of transcriptional factor SlNAC4 on tomato fruit metabolites during its ripening. The compounds were qualitatively analyzed by comparison of their mass spectral data with those in HMDB and KEGG databases as well as those of in-house reference standards using the XCMS software. The quantitative analysis and differential metabolite screening were carried out using metaX software. The results showed that a total of 67 differential metabolites that could match both the mass spectral and tandem mass spectral data (m/z) were found, including 19 amino acid derivatives and dipeptides, 7 vitamins, 4 carbohydrates and their derivatives, 11 nucleic acids and their derivatives, 4 alkaloids, 4 flavors and 9 organic acids, 29 of which were up-regulated whereas the rest were significantly down-regulated, indicating that SlNAC4 transcriptional factors affects tomato fruit metabolism during the ripening process.
Purification, Identification and Characterization of a Novel Antioxidant Pentapeptide
YAN Ana, CHEN Shengyang, CHEN Xu, TIAN Yongqi, FU Caili, WANG Shaoyun
2019, 40(10):  43-49.  doi:10.7506/spkx1002-6630-20180620-385
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Black shark skin was enzymatically hydrolyzed by protease to produce antioxidant peptides. The mechanism of action of the peptides was explored. The hydrolysis process was optimized based on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity and also by taking into account degree of hydrolysis. The antioxidant peptides were separated and purified by reversed-phase high performance liquid chromatography (RP-HPLC). The amino acid sequences were identified by electrospray ionization quadrupole-time of flight mass (ESI Q-TOF MS), and the in vitro antioxidant activity of the purified peptides was analyzed. The optimal hydrolysis parameters were determined as follows: use of alkaline protease as the best enzyme, enzyme dosage 311 U/mL, substrate concentration 3%, temperature 45 ℃, pH 8.0 and time 4.9 h. The hydrolysate obtained with a degree of hydrolysis of 14.21% under the optimized conditions scavenged 77.61% of DPPH radical. The hydrolysate was separated into 26 fractions. F19 was found to possess the strongest DPPH radical scavenging activity. The total ion current peak with higher antioxidant activity (at 10.02 min retention time) was selected for mass spectrometric (MS) and tandem mass spectrometric (MS/MS) analysis. The amino acid sequence of F19 was determined as Pro-Gly-Gly-Thr-Met. F19 at 1.0 mg/mL scavenged 75.01% of DPPH radical, and its oxygen radical absorption capacity (ORAC, calculated as Trolox equivalent) was 2 490.01 μmol/g. Pro and Met residues played a leading role in the antioxidant activity of F19. This study provides a theoretical basis for understanding the antioxidant mechanism and the structureactivity relationship of the pentapeptide derived from black shark skin.
Role of phoP Regulon in Environmental Stress Tolerance in Cronobacter sakazakii
ZHOU Yaqin, LI Mengyun, XIA Xiaodong
2019, 40(10):  50-56.  doi:10.7506/spkx1002-6630-20180619-359
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The aim of this study was to investigate the effect of the phoP regulon on environmental stress tolerance in Cronobacter sakazakii. A phoP-deleted strain of C. sakazakii was constructed by using the Red homologous recombination method, and then the growth curve and stress tolerance of the phoP-deleted strain were examined. The results showed that the phoP-defective strain showed delayed growth and weaker tolerance to external acid-base and heat stress. Meanwhile, it exhibited shortened time of death from heat treatment. phoP rendered C. sakazakii tolerant to bile salt environment, and its deletion resulted in a reduction in survival rate of 19.93% (P < 0.05), 40.73% (P < 0.01) and 45.84% (P < 0.01) in 4%, 8% and 12% bile salt solutions, respectively. The tolerance to osmotic pressure of the phoP gene-deficient strain was also significantly lower than that of the wild-type strain (P < 0.05). In conclusion, phoP enables C. sakazakii to respond to environmental stimuli.
Optimization of Fermentation Conditions for Higher Viable Count of Lactobacillus paraplantarum in Enzymatic Hydrolysate of Sturgeon Cartilage and Changes in Nutrient Components before and after Fermentation
WU Ruiyun, DU Yili, ZHANG Jinlan, YIN Jian, HU Jinrong, LI Pinglan
2019, 40(10):  57-63.  doi:10.7506/spkx1002-6630-20181210-123
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In order to improve the effective utilization rate of sturgeon bones and realize its high value-added utilization, enzymatic hydrolysate of sturgeon cartilage was fermented by Lactobacillus paraplantarum L-ZS9 and the fermentation parameters were optimized using one-factor-at-a-time method and response surface methodology. The optimal fermentation conditions were determined as follows: glucose concentration 17.11 g/L, inoculum amount 4.27%, initial pH 5.95, and fermentation time 20.07 h. Under these conditions, the viable number of strain L-ZS9 was (3.55 ± 0.10) × 108 CFU/mL. Furthermore, the changes in the contents of macronutrients in the hydrolysate before and after fermentation were investigated. The results showed that the soluble calcium concentration in the fermented hydrolysate was up to 20.88 mg/mL, which was significantly increased compared with that before fermentation. Meanwhile, the concentrations of phosphorus, magnesium and protein were increased by 14.4%, 6.5% and 26.7%, respectively. The results of this study provide new ideas and a theoretical basis for further processing and development of sturgeon bones.
Change in Antigenicity during Enzymatic Hydrolysis of Soybean Protein Isolate and Analysis of Linear Epitopes in the Hydrolysate
WANG Zhangcun, YUAN Luyang, ZHANG Lu, HU Jinqiang, AN Guangjie, ZHAO Xuewei
2019, 40(10):  64-69.  doi:10.7506/spkx1002-6630-20180612-187
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The aim of this study was to investigate the changes in the molecular composition and antigenicity of soybean protein during its enzymatic hydrolysis and whether there could be antigenic epitope sequences in the hydrolysate. The enzyme used was alcalase. The changes in molecular composition and antigenicity were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and competitive enzyme-linked immunosorbent assay (ELISA), respectively. Some new peptides (i.e., 23 and 21 ku) were found in the hydrolysate and did not disappear even after 120 min of hydrolysis. Meanwhile the hydrolysate still retained 28% of the original antigenicity. In order to determine whether the new peptide chains were related to the antigenicity, the proteomic bands in the SDS-PAGE gel were hydrolyzed by trypsin and then analyzed by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). The amino acid sequences of the peptide fragments obtained were matched with the amino acid sequences in the antigen database and the soybean protein isolate database, respectively. The results showed that there were two complete sequence epitopes (LQRFNQRSPQLQNLR and SEDKPFNLRSRDPIYSNKLGKFFEITPEKN) in the 21 ku component, both of which came from the α subunit in β-conglycinin. The residual antigenicity of this peptide fragment was 15.7%. The amino acid sequences of the 23 ku peptide chain were matched partially with those of epitopes but no complete epitopes were found. However, its residual antigenicity was 2.1%. These findings may partially account for the antigenicity of soybean protein hydrolysates.
Rheological Properties of Fermented Milk as Affected by Addition of Enterococcus faecium AS8 and Its Exopolysaccharides
BAI Ying, LIU Naiqi
2019, 40(10):  70-76.  doi:10.7506/spkx1002-6630-20180530-419
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This study aimed to investigate the structural composition of exopolysaccharides (EPS) from Enterococcus faecium AS8 and the rheological properties of traditional fermented dairy products in Inner Mongolia containing respectively Streptococcus thermophiles + Lactobacillus bulgaricus, EPS + S. thermophiles + L. bulgaricus and E. faecium AS8. Two fractions of EPS, named as AS8-1-EPS and AS8-2-EPS, were obtained by Sephadex G-100 column chromatography and purified by Sephadex G-50 column chromatography. AS8-1 was mainly composed of mannose (59.1%), glucose (26.8%) and galactose (7.9%). AS8-2-EPS was mainly composed of mannose (65.4%), glucose (21.3%), galactose (8.9%) and rhamnose (4.4%). The results of Fourier transform infrared (FT-IR) spectroscopy revealed that both EPS fractions were heteropolysaccharides.
Cloning and Prokaryotic Expression of the Xylose Isomerase Gene (LbxylA) from Chinese Wolfberry (Lycium barbarum Linn.) Fruit and Preparation of Polycloal Antibody against the Fused Protein
ZHAO Jianhua, LI Haoxia, YIN Yue, WANG Yajun, LI Yanlong, FAN Yunfang, AN Wei, CAO Youlong
2019, 40(10):  77-83.  doi:10.7506/spkx1002-6630-20180528-382
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In this study, the full-length sequence of the xylose isomerase gene (LbxylA) was obtained from Chinese wolfberry fruit from the cultivar ‘Ningqi 1’ (Lycium barbarum Linn.) by using reverse transcription-polymerase chain reaction (RTPCR). The open reading frame (ORF) of LbxylA was 1 446 bp in length encoding a polypeptide of 481 amino acids. The relative molecular mass was 53.54 kDa and the theoretical isoelectric point (pI) was 5.37. The deduced amino acid sequence of LbxylA shared a high similarity (95%) to those of the tobacco and potato xylose isomerase genes as revealed by bioinformatics analysis. The recombinant plasmid pGEX4T-1-LbxylA was constructed and transformed into E. coli Rosetta (DE3) for prokaryotic expression induced by isopropyl-β-D-thiogalactoside (IPTG), and the optimum expression conditions were determined as induction at 18 ℃ for 10 h with 100 μmol/L IPTG. The fused protein, partially soluble, was purified and used as an antigen to immunize Japanese big-ear white rabbits for the preparation of polyclonal antibody against the LbxylA protein. As a result, the serum antibody titer was higher than 1:81 000 as determined by indirect ELISA. The relative expression level of LbxylA in the fruit reached its maximum at 9 d after full bloom, and then decreased gradually with fruit development. The changes of LbxylA protein level as detected by Western Blot were basically consistent with the changes of LbxylA relative expression. The protein expression level of LbxylA was lower at 9 d after full bloom than at 15 d, and then decreased gradually from the 15th day onwards. Both the gene and protein expression levels reached the lowest values at the end of fruit ripening. This study indicated that the protein expression of LbxylA lags behind the gene transcription possibly owning to the post-translation processing at the early stage of fruit development. The results of this study are helpful to gain further insights into LbxylA function and its effect on sugar accumulation during fruit development.
Immobilization of Phospholipase A1 on Amino-Modified Fe3O4-SiO2
LI Jinhong, CAO Lili, PANG Min, PAN Lijun, HOU Zhigang, SHUI Longlong, BAO Sai, JIANG Shaotong
2019, 40(10):  84-91.  doi:10.7506/spkx1002-6630-20180614-264
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In this investigation, Fe3O4-SiO2 magnetic nanoparticles were used as a carrier to study the effects of different operating conditions on the immobilization of phospholipase A1. The optimal conditions determined using response surface methodology were as follows: pH 6.7, temperature 30 ℃, immobilization time 7.9 h, glutaraldehyde concentration 8.3%, and amount of enzyme 8.2 mL/50 mg. Under these conditions, the recovery of enzymatic activity was as high as 63.6% and the percentage of protein immobilization was 68%. The chemical composition, morphological structure and particle size of the immobilized phospholipase were characterized. The results showed that the efficiency of phospholipase immobilization was good; uniform particle size distribution was observed with a mean particle size of about 200 nm. The thermal, pH and storage stability of the immobilized enzyme were enhanced relative to the free one. The optimum reaction temperature for the immobilized enzyme was 50 ℃ and optimum pH 6.0. Over 60% of the enzymatic activity remained after tenth repeated use.
Cloning and Expression of Laccase Gene from Bacillus pumilus and Degradation of Aflatoxin M1 by Recombinant Laccase
HUO Chao, LU Haiqiang, LIU Xiaoyu, LI Qi, GAO Jie, SANG Yaxin
2019, 40(10):  92-98.  doi:10.7506/spkx1002-6630-20180516-249
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This study aimed at determining the enzymatic properties of recombinant CotA laccase and evaluating its potential for the degradation of aflatoxin M1 (AFM1). Our analysis demonstrated that the cotA gene of Bacillus pumilus E-1- 1-1 was 1 486 bp long, encoding 495 amino acids and having no signal peptide, and its putative protein molecular mass was 58 kDa. The optimum temperature for the recombinant laccase was 40 ℃, and the optimum pH was 4.0. The Km value was 3.01 mmol/L, and the Vmax value was 0.795 mmol/(L·min). Metal ions and chemical reagents had different effects on its enzymatic activity. K+, Na+, ethanol and SDS inhibited the enzymatic activity obviously with percentage inhibition of 31.0%, 13.6%, 64.5% and 100%, respectively. In contrast, Mn2+ and Zn2+ promoted the enzymatic activity by 33.0% and 23.9%, respectively. After 72 hours of reaction with this enzyme, the content of AFM1 in milk decreased by 54.3%, accompanied by a decrease in the toxicity of 9.1%. From this study, we concluded that CotA laccase from B. pumilus can have a great potential as an AFM1-degrading enzyme.
Isolation, Identification and Screening of Acid Tolerant Lactic Acid Bacteria from Chinese Sauerkraut
WANG Wan, LU Jiayin, JIAO Yuehua, WANG Yichao, JIANG Zhanmei, TIAN Bo, WANG Yutang, HOU Juncai
2019, 40(10):  99-105.  doi:10.7506/spkx1002-6630-20180524-348
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This work was undertaken in order to obtain lactic acid bacterial (LAB) strains with high acid tolerance. LAB strains isolated and purified from naturally fermented Chinese sauerkraut were tentatively identified by morphological observation and randomly amplified polymorphic DNA (RAPD) analysis. Subsequently, 16S rDNA sequence homology analysis was used for species identification and these strains were screened for their survival rate at pH 3.0. The results showed that a total of 72 LAB isolates were identified as Lactobacillus (62 strains) or Enterococcus (10 strains), the fingerprints of 21 of which were different. The 21 isolates were identified as E. lactis, L. curvatus, L. oryzae, L. brevis, L. paracasei or L. coryniformis. The survival rates of 8 of these strains were over 75% at pH 3.0. Homology analysis of the house-keeping gene rpoA showed that the two selected strains with high acid tolerance were L. plantarum. This study lays the foundation for developing functional foods containing lactic acid bacteria.
Analysis of Bacterial Diversity during Fermentation of Naturally Fermented Vegetables in Shanxi
KANG Jianyi, HONG Jie, GAO Yi, YANG Yue, CHEN Meng, YI Xinxin, GAO Xiuzhi
2019, 40(10):  106-111.  doi:10.7506/spkx1002-6630-20180615-306
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Changes in the bacterial community structure during the fermentation of naturally fermented vegetables in Shanxi were studied by Illumina HiSeq sequencing. Bacterial DNAs were extracted from samples collected at different fermentation stages and were sequenced. These samples were analyzed for their aerobic plate counts, lactic acid bacterial counts, and physicochemical indicators. The results showed that the bacterial diversity of the fermented vegetables was rich in the early stage of fermentation. The bacterial community structure became stable with the prolongation of fermentation time. The main genus in both the middle and late fermentation stages was Lactobacillus. During the fermentation period, pH increased and total acid content decreased. The aerobic plate count and lactic acid bacterial count in the finished fermented vegetables were 1.2 × 107 and 2.5 × 106 CFU/g, respectively. The nitrite content was 0.15 mg/kg, the pH was 3.22, and the total acid content was 1.98 g/kg. The number of Lactobacillus and nitrite showed an opposite trend. This study will hopefully provide a theoretical basis for the commercial production of fermented vegetables.
Improved Tolerance of Vacuum-Dried Pichia membranifaciens to Thermal Environment
ZHANG Hongyan, WANG Wenjun, DENG Lili, YAO Shixiang, ZENG Kaifang
2019, 40(10):  112-120.  doi:10.7506/spkx1002-6630-20180511-170
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We subjected Pichia membranifaciens to thermal and hydrogen peroxide pretreatments and added sodium chloride and calcium chloride to its culture medium in order to enhance its stress tolerance and hence improve the viability of vacuum-dried P. membranifaciens. The trehalose content of heat-adapted P. membranifaciens (40 ℃ for 40 min) was higher than that of the control; the survival of heat-adapted P. membranifaciens after vacuum-drying was higher than that of the control. The trehalose content of oxidative stress-adapted P. membranifaciens (40 min treatment with 5 mmol/L hydrogen peroxide) was higher than that of the control. Similarly, the survival of oxidative stress-adapted P. membranifaciens after vacuum-drying was higher than that of the control. The addition of 0.1–0.9 mol/L sodium chloride or 1–10 mmol/L calcium chloride to the culture medium induced a marked increase of the trehalose content, and P. membranifaciens cells showed the highest amount of trehalose upon adding 0.7 mol/L sodium chloride, followed by 0.9 mol/L sodium chloride; 5 mmol/L calcium chloride treated P. membranifaciens induced the highest amount of trehalose in yeast cells. The viability of vacuumdried P. membranifaciens without any protectant and with 0.7 or 0.9 mol/L sodium chloride added was higher than that of all other treatments and the control. The viability of vacuum-dried P. membranifaciens with a protectant and sodium chloride or calcium chloride at each concentration was not significantly different from that of the control, indicating that the effect of adding protectant on the viability of vacuum-dried P. membranifaciens is greater than that of pretreating the yeast with sodium chloride or calcium chloride.
Enzymatic Properties and Application in Biomass Conversion of Acidophilic Feruloyl Esterase from Trichoderma atroatroviride
GAO Zhaojian, XU Xiang, WANG Xianfeng, LU Ning, WANG Xudong, ZHANG Tiezhu, ZHANG Kangzhen, JIAO Wei
2019, 40(10):  121-128.  doi:10.7506/spkx1002-6630-20180522-311
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In order to realize efficient biomass degradation in the preparation of ferulic acid, exerting important physiological functions in the body, feruloyl esterase (TaFAE) was isolated and purified from the fermentation broth of Trichoderma atroatroviride XS6 and its enzymatic characteristics were described in this experiment. The electrophoretically pure enzyme was obtained by consecutive ammonium sulfate precipitation, DEAE-cellulose DE52 anion exchange chromatography and Sephadex G-200 gel filtration chromatography. SDS-polyacrylamide gel electrophoresis (SDS-PAGE) of the enzyme revealed a single band of about 66.4 kDa. Its specific activity was 134.3 U/mg, with a recovery of 28.9%, and 31.52-fold purification. TaFAE had the highest affinity for methyl ferulate. When methyl ferulate was used as substrate, the Km and Vmax values of the enzyme were 0.53 mmol/L and 16.74 μmol/(min·mg), respectively. When methyl sultacide was used as substrate, the highest enzymatic reaction rate of 32.21 μmol/(min·mg) was obtained, which was twice as high as that of methyl ferulate. In addition, no activity was shown toward methyl caffeate, indicating that the enzyme has a stringent substrate specificity. The optimum pH and temperature of TaFAE were pH 4.0 and 40 ℃, respectively. In the pH range of 2.0–9.0 and at 30–40 ℃, TaFAE showed good stability. The metal ions Ca2+ and Mg2+ promoted TaFAE activity, whereas Hg2+ and Pb2+ almost completely inhibited the activity of the enzyme; β-mercaptoethanol, dithiothreitol (DTT), SDS, and Trition X-100 promoted the enzymatic activity, whereas PMSF had a strong inhibitory effect. Biomass conversion by xylanase produced significantly more ferulic acid and reducing sugar when TaFAE was added to the system, indicating that TaFAE and xylanase have a good synergistic effect. In summary, TaFAE has good acid tolerance and enzymatic properties, which make it promising for applications in the feed and food industry.
Production and Structural Analysis of Propionin by High Cell Density Fed-Batch Fermentation
ZHENG Lixue, WANG Jiahao, CHEN Zhipeng, QI Bin, WANG Limei
2019, 40(10):  129-133.  doi:10.7506/spkx1002-6630-20180612-178
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In this work, high cell density fed-batch fermentation was carried out to produce propionin with higher antibacterial activity. Starting from 96 h of fermentation, a mixed carbon source (sodium lactate:glucose = 3:1, m/m) and a mixed nitrogen source (yeast extract:corn distiller’s grains liquid = 1:30, V/V) (100 mL each, 2.5 g/L) were added at 24 h intervals for a total of 120 h. As a result, the antibacterial activity of propionin was increased from 17.6 to 31.2 AU/mL. In this study, we innovatively used corn distiller’s grains liquid as an alternative nitrogen source to partially replace yeast extract in order to greatly reduce the production cost of propionin. In addition, propionin was found to be a proteinaceous material with antibacterial activity as revealed by infrared spectroscopy and protease sensitivity experiments. The results of this study lay the foundation for industrial production and application of propionin.
Influence of Different Amplified Regions on Results of Bacterial Diversity in Zhaguangjiao, a Chinese Traditional Fermented Chili Product, by MiSeq Sequencing
WANG Yurong, YANG Chengcong, GE Dongying, SHANG Xuejiao, ZHANG Zhendong, GUO Zhuang
2019, 40(10):  134-140.  doi:10.7506/spkx1002-6630-20180529-402
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This study aimed to evaluate whether different amplified regions of 16S rRNA gene influence the results of bacterial diversity in Zhaguagnjiao by MiSeq sequencing. The V1–V2, V3–V4 and V4–V5 regions were amplified using bacterial genomic DNA extracted from Zhaguangjiao samples as template with three different primer pairs, 27F/338R, 338F/806R and 515F/907R. The results indicated that the percentage of non-specific amplification sequences were significantly lower in the amplified products of V4–V5 region (P < 0.05), and the Chao 1 index was significantly higher in the amplified products of V1–V2 regions (P < 0.05). Although the relative abundance of Cyanobacteria and Pediococcus were significantly higher in the amplified products of V3–V4 region (P < 0.05), there was no significant difference in the microbial community structure of the same samples with different amplified variable regions (P > 0.05). Thus, amplification of the V4–V5 region using primer pair 515F/907R is recommended for analysis of the bacterial diversity of Zhaguangjiao.
Screening for Broad-Spectrum Lytic Phage against Vibrio parahaemolyticus and Its Application to Marine Products
ZHENG Xiaoshuang, GAO Lu, ZHANG Hui, RAO Shengqi, YANG Zhenquan
2019, 40(10):  141-148.  doi:10.7506/spkx1002-6630-20180621-405
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Five lytic bacteriophages were isolated from sewage samples using pathogenic Vibrio parahaemolyticus (Vp) strains as hosts. The biological and antibacterial properties of the isolated bacteriophages were studied using artificially contaminated yellow croaker as a model. Transmission electron microscopy (TEM) revealed that the 5 phages belonged to the Myoviridae, Siphoviridae or Corticoviridae families. The lytic spectrum showed that the single phages could lyse 5–24 Vp strains, while their mixture (VppMIX) could lyse all 42 tested Vp strains. The activity of the phages remained stable at 60 ℃ and pH 4–10. The bacteriophage insensitive mutant frequency (BIMF) of the single phages was 10-3–10-5, while that of VppMIX was reduced to 10-6. The bacteriostatic test showed that number of Vp in artificially contaminated yellow croaker was significantly reduced by 1.41–4.98 (lg(CFU/g)) as compared with the control (P < 0.01) when treated by VppMIX at 25 ℃ for 12 h . This study provides a new biological bacteriostatic agent to control pathogenic Vp in marine products.
Production and in Vitro Antioxidant Activity of Mycelial Polysaccharide from Ganoderma lucidum Utilizing Burdock (Arctium lappa L.) Root under Optimized Solid-State Fermentation Conditions
DONG Yuwei, ZHOU Jie, MIAO Jingzhi, LI Wen, HU Chuanyin
2019, 40(10):  149-156.  doi:10.7506/spkx1002-6630-20180617-347
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In order to achieve value-added utilization of burdock root waste, the solid-state fermentation of low-quality burdock root by a high-yield polysaccharide-producing strain of Ganoderma lucidum (Leyss. ex. Fr.) Karst was optimized for improved production of mycelial polysaccharide and the in vitro antioxidant activity of the polysaccharide was assessed. The fermentation conditions including amount of medium contained in culture flasks, degree of pulverization and liquid-tosolid ratio were optimized by combined use of one-factor-at-a-time method and response surface methodology. The mycelial polysaccharide from G. lucidum was extracted by water extraction and ethanol precipitation and was quantified by the phenol-sulfuric acid method. After being deproteinized and decolorized by dialysis, the polysaccharide was characterized by infrared spectroscopy and was determined for its monosaccharide composition by high performance liquid chromatography (HPLC). Besides, the in vitro antioxidant activity was evaluated by 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH), superoxide anion and hydroxyl radical scavenging assays. The results showed that the optimal fermentation conditions were as follows: liquid-to-solid ratio 0.4 mL/g, medium-to-culture flask ratio 0.2 g/mL, and use of particles passing through a 6-mesh sieve. The polysaccharide content of the mycelia harvested under the optimized conditions was 24.85 mg/g. Fourier-transform infrared spectroscopy (FTIR) analysis showed that the product had the characteristic absorption peaks of polysaccharide. The monosaccharide composition analysis showed that the polysaccharide was composed of mannose, ribose, rhamnose, glucose and galactose, with mannose being the most abundant monosaccharide, which was 7.6 times as high as glucose. Each of the free radical was over 70% scavenged by the polysaccharide, and the effect increased with increasing its concentration. Hence, the polysaccharide had good antioxidant activity in vitro.
Induced Biosynthesis and Antioxidant Properties of Triterpenoids in Inonotus hispidus
KANG Ning, WANG Zhanbin, LI Dehai, WANG Luan
2019, 40(10):  157-165.  doi:10.7506/spkx1002-6630-20180530-430
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This study aimed to explore the effect of exogenous inducers on the biosynthesis and antioxidant properties of triterpenoids in Inonotus hispidus. We used seven inducers at different concentrations including methyl jasmonate (MeJA), salicylic acid (SA), oleic acid, willow branch decoction, Mn2+, Fe2+ and Cu2+. The results showed that all the seven inducers significantly promoted the mycelial growth of I. hispidus and the biosynthesis of triterpenoids, oleic acid being the most effective among these. A mycelial biomass yield of (7.146 ± 0.131) g/L was obtained by the addition of 3% oleic acid at the beginning of fermentation. The content of triterpenoids in the mycelia was (56.377 ± 3.178) mg/g, and the total production of triterpenoids was 402.870 mg/L, which was increased by 143.74% compared with the control group without any inducer added. The antioxidant tests showed that the antioxidant capacity of triterpenoids varied with inducer type. Among these inducers, oleic acid induced triterpenoids with the strongest antioxidant effect; the total reducing power was 1.342, and the IC50 values for scavenging of 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl and superoxide anion radicals were 0.099, 1.294 and 0.001 mg/mL, respectively. The total reducing power and the free radical scavenging rates were increased by 79.48%, 66.71%, 28.10% and 29.22% compared with those of the control group, respectively. The results can provide scientific data for the application of inducers in the biosynthesis of triterpenoids and hence the development of new antioxidants.
Screening for and Identification of Freeze-Tolerant Yeasts with Antioxidant Activity in Fish
GUO Weidan, LIU Weicong, HU Zuomin, LI Zhengwen, FU Xiangjin
2019, 40(10):  166-170.  doi:10.7506/spkx1002-6630-20180610-145
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In this paper, freeze-tolerant yeasts from common fermented foods were enriched by five freeze-thawing cycles and were isolated and purified by spread plate and streak plate methods. The growth characteristics, gas production characteristics and antioxidant activity against lipid oxidation in fish of the isolates were analyzed. A total of 25 yeast strains with freezing tolerance were obtained, of which, strains J3, J7, J8, J9, J12, J15, J18 and J25 exhibited good fermentation ability at low temperatures while J8, J12 and J18 inhibited lipid oxidation effectively. These 8 strains were identified as Wickerhamomyces anomalus by 5.8S rDNA sequencing and phylogenetic analysis. This study provides valuable information for developing new preservatives for aquatic products.
Optimization of Fermentation Process for Whole Navel Orange Wine and Comparative Analysis of Flavor Components with Navel Orange Juice Wine
ZHENG Shudan, CHEN Gang, QUE Faxiu, WAN Ling, DENG Shanhong, JIAN Suping
2019, 40(10):  171-177.  doi:10.7506/spkx1002-6630-20181011-090
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Whole navel oranges were utilized as raw material for fruit wine brewing. The effects of yeast inoculum amount, temperature and fermentation time on ethanol production and residual sugar concentration were analyzed by one-factor-ata- time method and Box-Behnken experimental design. The optimal fermentation conditions were determined as follows: inoculum amount 6.4%, temperature 28 ℃ and fermentation time 14 days. The volatile flavor components of whole navel orange wine and navel orange juice wine were extracted by headspace solid-phase microextraction (HS-SPME) and identified by gas chromatography-mass spectrometry (GC-MS). The results showed that 25 and 11 volatile aroma compounds were detected in whole navel orange wine and navel orange juice wine, respectively. The main aroma active components of whole navel orange wine were terpenes, which accounted for 66.00% of the total amount of aroma components, while the main aroma components of navel orange juice wine were alcohols, accounting for 91.95%.
Composition Analysis
Qualitative and Quantitative Analysis of Soluble and Bound Anthocyanins in Black Soybean Seed Coat by High Performance Liquid Chromatography-Mass Spectrometry
DUN Qian, PENG Han, MAI Qiying, DENG Zeyuan, ZHANG Bing
2019, 40(10):  178-186.  doi:10.7506/spkx1002-6630-20180507-095
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Ultrasonic-assisted organic solvent extraction was used to obtain soluble anthocyanins from black soybean seed coat, and bound anthocyanins from the extraction residue were obtained by treatment with acid, alkaline, sequential acid/ alkali hydrolysis or the reverse sequence. By ultra-high performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry (UPLC-ESI-QTOF-MS), a total of 17 anthocyanin components, including 11 anthocyanin glycosides: delphinidin-3-O-glucoside, delphinidin-3-O-galactoside, petunidin-3-O-glucoside, petunidin-3-O-galactoside, pelargonidin-3-O-rutinoside, cyanidin-3-O-glucoside, cyanidin-3-O-galactoside, pelargonidin-3- O-hexoside, peonidin-3-O-hexoside, pelargonidin-3-O-(6”-malonyl glucoside) and apigeninidin-3-O-(6”-malonyl glucoside); and 6 anthocyanin aglycones: delphinidin, cyanidin, petunidin, pelargonidin, apigeninidin, and peonidin, were identified from these extracts. High performance liquid chromatography coupled with electrospray ionization triple quadrupole mass spectrometry (HPLC-ESI-QQQ-MS) was used to accurately quantify the content of anthocyanins. The total content of bound anthocyanins in the acid extract was the highest. In addition, in the soluble anthocyanin extract, anthocyanins were present mainly in the form of anthocyanin glycoside with lesser amounts of aglycons, whereas in the bound anthocyanin extract, anthocyanin aglycons were the main components but glycosides were rare.
Effect of Cooking, Autoclaving and Reheating on the Volatile Components of Steamed Pork with Rice Flour
ZHANG Zheqi, ZANG Mingwu, ZHANG Kaihua, LI Dan, WANG Shouwei, LI Xiaoman
2019, 40(10):  187-192.  doi:10.7506/spkx1002-6630-20181009-063
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The volatile flavor components in steamed pork with rice flour sampled at different processing stages (cooking and autoclaving) and after reheating were extracted and identified by solid phase micro-extraction (SPME) combined with gas chromatography-mass spectrometry-olfactometry (GC-MS-O) in order to understand the formation of its flavor. A total of 40 volatile compounds were identified, eighteen of which were common to the uncooked (A), cooked (B), autoclaved (C), hot water-reheated (D) and microwave-reheated (E) samples. The content of volatile substances in all autoclaved samples (2 026.40 and 1 978.77 μg/kg for samples C and D) except for sample E (989.12 μg/kg) was significantly higher than that of the unautoclaved samples A (705.00 μg/kg) and B (1 038.53 μg/kg). Odor activity values (OAVs) showed that ethyl caproate and aldehydes may be mainly responsible for the unpleasant overcooked and can-like flavors. Principal component analysis (PCA) showed obvious separation between the five groups. All groups except the microwave-reheated one exhibited a remarkable difference in the contribution of the second principal component (PC2) but not the first principal component (PC1). The contribution of PC1 in the microwave-reheated group was lower than that of the other groups, whereas there was little difference in the contribution of PC2 between the microwave-reheated and autoclaved groups. Overall, controlling the formation of aldehydes and ethyl hexanoate helps to inhibit the formation of off-flavors caused by autoclaving and reheating in steamed pork with rice flour and microwave reheating has little effect on the flavor.
Comparison of Full-Spectrum Free and Hydrolyzed Amino Acids in Human and Bovine Milks
GUAN Boyuan, ZHANG Zhenghan, SHI Jiaxin, SHI Xu, YUE Xiqing, YANG Mei
2019, 40(10):  193-198.  doi:10.7506/spkx1002-6630-20180515-213
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For this experiment, we collected human and bovine milks at 30–40 days postpartum. Isobaric tags for relative and absolute quantification combined with high performance liquid chromatography-tandem mass spectrometry (iTRAQ-HPLCMS/ MS) was used to compare the composition of full-spectrum free and hydrolyzed amino acids in milk samples. The results indicated that total free amino acid content was 0.37 and 0.16 g/L in human and bovine milks, and total hydrolyzed amino acid content was 2.5 and 3.3 g/L, respectively. Among the full-spectrum free amino acids, 9 essential amino acids and 15 non-protein amino acids were detected in both milks, and 11 and 7 non-essential amino acids were detected in human and bovine milks, respectively. Moreover, 9 essential amino acids, 10 non-essential amino acids and 7 non-protein amino acids in human milk were significantly more abundant than in bovine milk (P < 0.05). Among the full-spectrum hydrolyzed amino acids, 8 essential amino acids, 10 non-essential amino acids and 12 non-protein amino acids were detected simultaneously in human and bovine milks. Moreover, the levels of γ-aminobutyric acid, taurine, α-amino-n-butyric acid and β-alanine in human milk were significantly higher than in bovine milk (P < 0.05). This study provides a theoretical basis for the development of milk formulaeand functional foods.
Changes of Volatile Flavor Compounds in Spiced Beef Marinated with Different Water Contents
LI Su, ZHOU Huimin, ZHANG Shunliang, LIU Jiawen, ZHAO Bing, PAN Xiaoqian, XU Dian, GUO Ya, LIU Bowen
2019, 40(10):  199-205.  doi:10.7506/spkx1002-6630-20181105-049
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The volatile flavor compounds of spiced beef samples prepared by consecutive tumbling marination with different water contents (0%, 5%, 10%, 15%, 20%, and 25%) and autoclaving were analyzed by purge-trapping and thermal desorption coupled with gas chromatography-mass spectrometry (GC-MS) and were identified by malondialdehyde content, odor activity value (OAV) analysis and sensory evaluation. The results showed that the relative concentrations of aldehydes, ethers, ketones, alcohols and hydrocarbons were higher in all six samples than the other compounds identified and declined with increasing water content. The total volatile concentration of spiced beef marinated with 20% water added was the highest, up to 2 325.65 μg/kg. OAV analysis of these samples showed that aldehydes, ketones and sulfur-containing compounds contributed greatly to the flavor of the product, and furfuryl mercaptan, linalool and 3-hydroxy-2-butanone had the highest flavor activity values in the sample marinated with 10% water content. Based on these results combined with sensory evaluation, the spiced beef sample marinated with addition of 10% water had the best flavor.
Change in Volatile Components of Sinonovacula constricta during Temporary Culture in Seawater
RAN Yun, ZHANG Sijia, CHEN Rong, RAN Zhaoshou, XU Jilin, LIAO Kai
2019, 40(10):  206-213.  doi:10.7506/spkx1002-6630-20180513-188
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This study investigated changes in flavor components of Sinonovacula constricta during temporary culture (0, 8, and 24 h) in seawater by headspace solid phase micro-extraction coupled with gas chromatography-mass spectrometry (HSSPME- GC-MS). A total of 128 volatile components were detected, including aldehydes (33), ketones (12), alcohols (10), aromatics (17), hydrocarbons (16), esters (22), furan (5) and other compounds (13). The principal component analysis (PCA) results showed that the flavor of S. constricta meat was changed little after purification by temporary culture. The overall flavor change was mainly caused by the changes in volatile components in the digestive gland of S. constricta. The results of partial least squares discriminant analysis (PLS-DA) showed that the overall flavor of S. constricta remained unchanged while the off-flavor was reduced, leading to improved palatability, after temporarily culture for 8 h. The contents of volatile components in the digestive gland of S. constricta decreased obviously after temporary culture for a short period of time, but then increased again when the culture time was too long. Thus, the best temporary cultivation time was 8 h, which could maintain the unique flavor of S. constricta, reduce the unpleasant earthy and fishy odors and consequently improved the sensory quality.
Qingzhuan Brick Tea Infusion: Analysis of Taste Components and Establishment of Quality Evaluation Model
WANG Shengpeng, GONG Ziming, ZHENG Pengcheng, LIU Panpan, GAO Shiwei, TENG Jing, WANG Xueping, YE Fei, ZHENG Lin, GUI Anhui
2019, 40(10):  214-219.  doi:10.7506/spkx1002-6630-20180604-028
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In the present experiment, Qingzhuan tea samples from different manufacturers were used. Taste sensory evaluation of the tea infusions was carried out, followed by chemical measurement. Then, representative chemical components were selected by principal component analysis (PCA) and the correlation coefficient method. Finally, a regression equation for taste quality evaluation of tea infusion was established by principal component regression (PCR) or stepwise regression (SR), and the predictive performance of the regression equation was tested by applying it to unknown samples. The results showed that five components were found to be closely related to the taste quality of tea infusion (P < 0.05), whose contributions to the taste of tea infusion were in the descending order of EGCG, total catechins, tea polyphenols, ECG and EGC. The SR model was better than the PCR model, and the correlation coefficient of calibration (Rc 2 ), root mean square error of cross-validation (RMSECV), correlation coefficient of prediction (Rp 2) and root mean square error of prediction (RMSEP) of the SR model were 0.973 5, 0.380 7, 0.968 1 and 0.400 0, respectively. The SR model showed better predictive performance for the unknown samples (Rp 2 = 0.974 6, and RMSEP = 0.391 5). The results showed that the chemometric model was able to predict the taste quality of Qingzhuan brick tea accurately and reliably and could provide a new method for evaluating the taste quality of Qingzhuan tea infusion.
Analysis of Characteristic Aroma Constituents of Hawk Tea
ZHANG Lei, WANG Jie, LUO Liyong, ZENG Liang
2019, 40(10):  220-228.  doi:10.7506/spkx1002-6630-20180128-384
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Hawk tea, a kind of herbal tea with a unique pungent aroma, is popular in the southwest of China for a long time. In order to identify the aroma characteristics of hawk tea, 17 samples of commercial hawk tea were analyzed using headspace solid phase micro-extraction coupled to gas chromatography-mass spectrometry (HS-SPME-GC-MS) in this study. Then the characteristic aroma components of hawk tea were identified based on odor activity values (OAVs) and a comparative quantitative analysis of the aroma components identified. For this purpose, principal component analysis (PCA) was also carried out. The results obtained were as follows: 1) 6 classes of volatiles were detected from hawk tea samples, namely 61 terpene olefins, 22 alcohols, 15 aldehydes, 10 ketones, 4 esters, and 5 other substances; with terpene olefins being predominant; 2) based on the results of PCA, 20 volatile compounds including alpha-copaene, alpha-santalol were selected as the main aroma constituents of hawk tea; and 3) according to OVAs and the comparative quantitative analysis, 38 volatile compounds such as lauraldehyde, beta-ionone and epiglobulol contributed greatly to the aroma characteristics of hawk tea. Overall, 12 volatile compounds including spathulenol, alpha- bourbonene, and calamenene were responsible for the pungent camphor-like aroma of hawk tea, 17 compounds including lauraldehyde, alpha-pinene, 3-carene and beta-ionone for the flowery, fruity and rosin-like aroma, and 9 compounds including alpha-tantalol, alpha-gurjunene and alpha-guaiene for the wood, sandalwood-like and herbal aroma.
Comparative Analysis of Volatile Components of Tricholoma matsutake and Agaricus blazei
ZHANG Xianchen, ZHANG Pengjie, RONG Yutang, QIU Deyi, LU Junwen, HUA Hongbo
2019, 40(10):  229-235.  doi:10.7506/spkx1002-6630-20180503-027
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In order to investigate the differences in the volatile components of dried fruit bodies of Tricholoma matsutake and A. blazei, headspace solid phase micro-extraction combined with gas chromatography-tandem mass spectrometry (HSSPME- GC-MS/MS) was used to analyze the volatile components of T. matsutake from four different producing areas and A. blazei from three different producing areas. Totally seventy-six volatile compounds including asters, aldehydes, alcohols, phenols, olefins, ketones, acids, furans, and nitrogen-containing heterocyclic compounds were identified from the dried samples of T. matsutake, twenty-five of which were common to these samples. Totally, sixty-nine volatile compounds including asters, aldehydes, alcohols, phenols, olefins, ketones, acids, furans, and nitrogen-containing heterocyclic compounds were identified from the dried samples of A. blazei, twenty-eight of which were common to these samples. Comparative analysis indicated that methyl cinnamate, 1-octen-3-one, 1-octen-3-ol, pentanal and decanal as the characteristic volatile components of T. matsutake, and benzaldehyde, 2-isopropyl-5-methylhex-2-enal as the characteristic volatile components of A. blazei could be used as effective chemical indicators for the discrimination of T. matsutake from A. blazei, and could also provide useful information to evaluate the quality of T. matsutake and A. blazei.
Analysis of Volatile Compounds in Fermented Sturgeon
ZHAO Feng, XU Ping, ZENG Shiyu, YANG Xing
2019, 40(10):  236-242.  doi:10.7506/spkx1002-6630-20180514-199
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The changes of volatile flavor compounds in fermented sturgeon sampled at different stages of the fermentation process were analyzed by solid phase micro-extraction (SPME) coupled to gas chromatography-mass spectrometry (GCMS). The key volatile flavor compounds were identified based on relative odor activity value (ROAV) as a function of odor threshold. A total of 38, 48, 66, 72, 75, 76 and 84 compounds were identified in fresh, salted, 5, 10, 20, 25 and 35 d fermented sturgeon respectively. 2,4-Decadienal, 1-octen-3-ol, nonanal, decanal, and hexanal were the key flavor compounds in the fresh sample. Nonanal, 1-octen-3-ol, hexanal, decanal, and D-limonene were the key flavor compounds in the salted sample. 1-Octen-3-ol, D-limonene, nonanal, hexanoic acid, ethyl ester, and 1-heptanol were the key flavor compounds in the 5 d fermented sample. Nonanal, 1-octen-3-ol, hexanoic acid, ethyl ester, D-limonene, and decanal were the key flavor compounds in the 10 d fermented sample. Nonanal, D-limonene, 1-octen-3-ol, decanal, hexanoic acid, and ethyl ester were the key flavor compounds in the 20 d fermented sample. Nonanal, D-limonene, 1-octen-3-ol, hexanoic acid, ethyl ester, and decanal were the key flavor compounds in the 25 d fermented sample. Hexanoic acid, ethyl ester, D-limonene, nonanal, 1-octen-3-ol, and 1-heptanol were the key flavor compounds in the 35 d fermented sample.
Principal Component Analysis and Cluster Analysis for Evaluating Free Amino Acids of Different Cultivars of Daylily Buds
LIU Wei, ZHANG Qun, LI Zhijian, BIAN Jianming, HUANG Lühong, ZHU Xiangrong, SHAN Yang
2019, 40(10):  243-250.  doi:10.7506/spkx1002-6630-20180523-336
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This study aimed to analyze the differences in the composition, content and taste of free amino acids in daylily buds from 10 main cultivars in Hunan province. We determined the free amino acid profiles with an automatic amino acid analyzer and a systematic evaluation was performed by measurement of taste activity value (TAV), correlation analysis, principal component analysis (PCA) and cluster analysis. The results showed that daylily buds contained abundant free amino acids. A total of 14–17 free amino acids were detected at a total content of 13.935 mg/g. There were significant differences in the contents of free amino acids (FAA), total essential amino acids (EAA), taste-active amino acids (DAA) and limiting amino acids (LAA) in the 10 cultivars of daylily buds, among which the highest TFAA, EAA, DAA and LAA were observed in the cultivar CT. Glu had the greatest influence on the flavor of daylily buds, and its TAV value was between 3.53–7.51 with an average of 5.66. Three principal components were extracted by PCA, which contributed cumulatively to 89.242% of the total variance. The comprehensive scores of CT, TT and BY were ranked as the top three. Cluster analysis was used to divide these daylily cultivars into 4 groups, and the results were consistent with the PCA, which reflected the distinction among different germplasms of daylily in Hunan.
Analysis of Aroma Components of Green Teas Made from Leaves of High-Quality Tea Strains in Hubei Province
MA Linlong, LIU Yanli, CAO Dan, GONG Ziming, LIU Panpan, JIN Xiaofang
2019, 40(10):  251-256.  doi:10.7506/spkx1002-6630-20180206-088
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The volatile aroma compounds of green teas made from the leaves of 6 high-quality tea strains in Hubei province were analyzed by sensory evaluation and headspace solid phase micro-extraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS) in this study. Our results showed that all tea samples had fresh, clean and high aromas, which were typical of green tea. Three of them, 01-4-7, 20-2-1 and 03-7-1, presented floral aroma. Meanwhile, a total of 55 aroma components were detected in the green teas with the major ones being alcohols, aldehydes and esters. Among the identified compounds, linalool, nonanal, (Z)-3-hexenyl hexanoate, geraniol and (E)-hex-3-enyl butyrate were predominant followed by dimethyl sulfide, methyl salicylate, heptanal and decanal. A significant difference was observed in the content of aroma compounds in the six green teas, and some of them had unique aroma components at high levels. Totally, nine aroma components with high odor activity value (OAV), including sequential linalool, decanal, dimethyl sulfide, β-ionone, geraniol, nonanal, heptanal, (E)-2-nonenal and (Z)-3-hexenyl hexanoate, were found in the present study, which may contribute to the aroma characteristics of the green teas. Multivariate analysis indicated that a marked difference was found in aroma components between six green teas and Fuding white tea, and four green teas including 03-7-4, 01-4-7, 07-7-68 and 03-7-1 showed a similarity in their aroma components. Among all these green teas, 20-2-1 had higher contents of esters and the highest total amount of aroma compounds while 07-7-64 was richer in aldehyde compounds. In addition, we also verified that there were significant differences in the contents of 19 aroma components in the measured samples.
Analysis and Preparation of Cyanidin Glycosides from Purple Cabbage
JIANG Xiaolan, SHI Yufeng, FU Zhouping, CHENG Lin, LIU Yajun, GAO Liping, XIA Tao
2019, 40(10):  257-264.  doi:10.7506/spkx1002-6630-20180515-223
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In this experiment we identified 16 cyanidin glycosides from purple cabbage. Cyanidins were extracted from purple cabbage under the optimized conditions as follows: 50% ethanol containing 1% hydrochloric acid as extraction solvent, and a solid-to-solvent ratio of 1:10 (g/mL). The extract was purified with macroporous resin AB-8 and then hydrolyzed with acid at high temperature to free cyanidin glycosides. Furthermore, the hydrolysate was purified by C18 column chromatography, yielding cyanidin monomers with 99% purity.
Process and Technology
Preparation and Identification of Calcium Citrate Malate from Tilapia Scale
ZHANG Ling, TAN Nanfeng, LI Chunhai, ZHOU Huimin, ZHANG Zhong, LI Wen
2019, 40(10):  265-271.  doi:10.7506/spkx1002-6630-20180202-026
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In this paper, calcium citrate malate (CCM) was prepared by ultrasonic-assisted organic acid treatment of tilapia scale. The pretreatment and preparation conditions were optimized and the structure of the product were characterized. The results showed that good extraction efficiency was obtained by ultrasonic-assisted preparation of fish scale without boiling. At a solvent-to-solid ratio of 20:1 (mL/g), the optimum conditions for preparing CCM were obtained by orthogonal array design as follows: 12% (m/m) of an citric acid-malic acid mixture at a mass ratio of 2:1, temperature 70 ℃ and time 1.0 h. Under these conditions, the maximum extraction rate of calcium of 18.97% was obtained. Infrared spectroscopy analysis and X-ray diffraction (XRD) showed that the product was not a physical mixture of calcium citrate and calcium malate, but coincided with the structure of CCM. Scanning electron microscope showed that the crystal structure was a hexahedron. The specific surface area from mesoporous pore volume determination of the product was 385.703 m2/g, average pore size 4.049 nm and single point adsorption total pore volume 0.320 cm3/g. CCM was successfully prepared by this method with higher yield of calcium. These research results provide some theoretical support for the processing of organic calcium products from tilapia scale.
Optimization of Removal of Cadmium from Rice Flour by Water Soaking and Its Effect on Quality
CHEN Yuwei, WANG Lei, WU Yongning, GONG Zhiyong
2019, 40(10):  272-278.  doi:10.7506/spkx1002-6630-20180312-157
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The conditions for removing cadmium from rice flour by water soaking were optimized using response surface methodology. The effects of the optimized treatment on nutrient retention were determined. We also investigated the effects on the morphology, thermodynamic characteristics, starch crystal structure and functional groups of rice flour by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and Fourier transform infrared spectrometry (FTIR), respectively. The results showed that the optimal conditions that provided the maximum remove rate of cadmium of (0.459 ± 0.006) mg/kg (cadmium content (0.176 ± 0.003) mg/kg) were determined as follows: temperature 42 ℃, solid to water ratio 1:3, and soaking time 47 h. Under these conditions, protein content of rice flour decreased significantly (P < 0.05), and the contents of fat, starch and ash decreased slightly. The onset temperature of gelatinization of rice flour starch decreased after water soaking, while the peak temperature changed little, indicating damaged crystal layer, reduced stability and possibly increased amylose content of rice starch. On the other hand, the soaking treatment did not destroy the crystal components of starch granules in rice flour. The d-spacing of the soaked rice flour decreased slightly, indicating that soaking may lead to deterioration in hardness, chewiness and resilience and cohesiveness. No new chemical bonds or groups were formed during the process of water soaking.
Safety Detection
Quality Detection of Xinyang Maojian Tea Using Electronic Nose and Electronic Tongue
ZOU Guangyu, WANG Wanzhang, WANG Miaosen, XIAO Yanzhong, ZHANG Hongmei
2019, 40(10):  279-284.  doi:10.7506/spkx1002-6630-20180504-039
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In order to rapidly identify and predict tea quality, the volatile odor components of Xinyang Maojian tea and the taste components of its infusion were analyzed with an electronic nose and an electronic tongue. Principal component analysis (PCA) indicated that the fusion of the electronic nose and tongue data allowed a better discrimination among tea samples. The fused data were used to develop mathematical models to predict the contents of tea polyphenol and caffeine. Results showed that the regression coefficients of the multiple linear regression (MLR), multivariate linear stepwise regression (MLSR) and quadratic polynomial stepwise regression (QPSR) models were all statistically significant (P < 0.01). The QPSR model presented the best prediction performance among these models. The determination coefficients of calibration and validation of this model were 0.999 and 0.975 for tea polyphenol, and 0.985 and 0.978 for caffeine, respectively; the root mean square error of calibration (RMSEC) were 0.083 and 0.174 for tea polyphenol, and 0.015 and 0.048 for caffeine, respectively. The combination of electronic nose and tongue is feasible to predict the quality and chemical composition of tea.
Nondestructive Detection of Sucrose Content of Lingwu Changzao Jujubes by Hyperspectral Imaging
CHENG Lijuan, LIU Guishan, HE Jianguo, YANG Xiaoyu, WAN Guoling, ZHANG Chong, MA Chao
2019, 40(10):  285-291.  doi:10.7506/spkx1002-6630-20180508-119
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In the present study, we focused on developing a rapid non-destructive method for rapid detection of the sugar content in Lingwu Changzao jujubes in order to predict the distribution of sugar content. High performance liquid chromatography (HPLC) was used to detect the sucrose content. Simultaneously, hyperspectral imaging combined with chemometrics method was used to establish a predictive model for sucrose content. The predictive models were built based on the full spectra and the feature wavelengths using partial least squares regression (PLSR), principle component regression (PCR) and multi-variable linear regression (MLR) through dimensionality reduction using competitive adaptive reweighed sampling (CARS), successive projections algorithm (SPA) and uninformative variable elimination (UVE). It was found that the correlation coefficient was increased from 0.611 to 0.846 by removing the abnormal samples using the Monte Carlo method; orthogonal signal correction (OSC) was the optimal preprocessing approach, and the correlation coefficients of calibration and prediction sets (RC and RP) of the PLS model were 0.853 and 0.794, respectively; SPA, UVE, CARS, CARS + SPA and CARS + UVE methods were used to select 5, 21, 17, 10, and 18 characteristic wavelengths, respectively. The CARS-PCR model was the best among the models developed, and its RC, RP, root mean square error of calibration (RMSEC) and root mean square error of prediction (RMSEP) values were 0.861, 0.843, 0.013 mg/g and 0.014 mg/g, respectively.According to the results of this study, hyperspectral imaging can be used to predict the sucrose content of jujube, laying the foundation for insights into the internal quality of jujubes.
Evaluation of Uncertainty in Determination of Plant Growth Regulator Residues in Bean Sprouts by Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry
LI Jing, ZHANG Juzhou, YU Xiaojuan, LIU Yi
2019, 40(10):  292-297.  doi:10.7506/spkx1002-6630-20180323-304
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The study was aimed at evaluation of the measurement uncertainty in the determination of three plant growth regulator residues in bean sprouts by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/ MS). According to Evaluation and Expression of Uncertainty of Measurement (JJF 1059.1-2012), a mathematical model of uncertainty evaluation was constructed, and the sources of uncertainty were analyzed in depth, and each component was quantified and synthesized. The results showed that the main sources of uncertainty arose from the preparation of standard solution and curve fitting. Furthermore, the expanded uncertainty was 0.6, 2.3 and 2.3 μg/kg for paclobutrazol, indole-3-acetic acid and 3-indolebutyric acid contents of 5.9, 15.5 and 16.0 μg/kg in bean sprouts (k = 2), respectively.
Determination of Carrageenan in Livestock Meat by High Performance Liquid Chromatography-Mass Spectrometry
ZHANG Huiliang, HUANG Chuanfeng, LI Peixuan, JIANG Feng, SUN Shanshan, DING Hong, CAO Jin
2019, 40(10):  298-303.  doi:10.7506/spkx1002-6630-20180404-044
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This study aimed to establish a method for the determination of added carrageenan in livestock meat by high performance liquid chromatography-mass spectrometry (HPLC-MS). Carrageenan in fresh meat was digested with 1 mol/L hydrochloric acid, yielding characteristic oligosaccharide fragments such as [A-G4S]-, which were detected by HPLC-triple quadrupole mass spectrometry. A high resolution mass spectrometer was employed for validation of the method. The results showed that no false positive results were found for natural meat samples, while positive samples such as steak labelled to contain carrageenan were identified effectively by the proposed method. The limit of detection (LOD) of carrageenan was 20 mg/kg (at m/z 403 > 241). A good linear relationship was observed in the concentration range of 0.1–0.4 g/kg with correlation coefficients of more than 0.99. The relative recoveries were in the range of 90%–120%. In summary, this method, thanks to its simplicity, clear target and high sensitivity, could be used as an effective means to detect carrageenan-injected livestock meat.
Determination of Six Zeranols in Milk by QuEChERS-High Performance Liquid Chromatography-Tandem Mass Spectrometry
XIE Yujie, CHEN Hui, PENG Tao, DAI Hanhui, HU Xueyan, FAN Chunlin, HU Xiuzhi, XUE Zhanyong
2019, 40(10):  304-310.  doi:10.7506/spkx1002-6630-20180509-141
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A method for simultaneous determination of six zeranols residues in milk was developed by quick, easy cheap, effective, rugged and safe (QuEChERS) extraction coupled to high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The sample was extracted with 1% acetate acetonitrile. The extract was degreased with acetonitrile-saturated n-hexane, cleaned up with a mixture of C18, primary secondary amine (PSA) and magnesium sulfate anhydrous. The analytes were separated on a reversed phase C18 column and gradiently eluted with 5 mmol/L ammonium acetate and acetonitrile. These analytes were analyzed under the multiple reaction monitoring (MRM) mode with negative electrospray ionization (ESI-) and quantified by matrix-matched external standard method. Good linearity was obtained for the six zeranols in the concentration range of 0.1–50 μg/L with correlation coefficients of more than 0.995. The limits of detection (LODs) and the limits of quantification (LOQs) for the zeranols were 0.05–0.1 and 0.25–0.5 μg/kg, respectively. The recoveries at three spiked concentration levels were in the range of 91.8%–114.5%. The repeatability expressed as relative standard deviation (RSD) ranged from 3.2% to 14.4% (n = 6).
Optimized Detection and Pollution Exposure of Chloropropanol Fatty Acid Esters in Infant Formula
ZHANG Ni, ZHOU Jing, HU Shoujiang, YE Qing, PENG Yafeng, LU Yi
2019, 40(10):  311-317.  doi:10.7506/spkx1002-6630-20180305-048
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Objective: A method for the simultaneous determination of the contents of 3-monochloropropane-1,2-diol ester (3-MCPDE), 2-monochloropropane-1,3-diol ester (2-MCPDE), 1,3-dichloropropane-2-ol ester (1,3-DCPE) and 2,3-dichloropropane-1-ol ester (2,3-DCPE) in infant formula was established by gas chromatography-mass spectrometry (GC-MS). A total of 50 infant formula samples sold in Shanghai were researched for the pollution levels of four chloropropanol fatty acid esters (CPFAEs). Also we assessed the dietary exposure of infants to CPFAEs in infant formula. Methods: Fat was extracted from samples, followed by alkali hydrolysis, solid-phase extraction purification through a diatomite column and derivatization with heptafluoro butyrylimidazole before being injected into the GC-MS system. The analytes were quantified by the internal standard method. Results: The method showed a good linear relationship in the concentration range of 20–600 ng/mL (r2 ≥ 0.998 9). The limit of detection (LOD) and limit of quantification (LOQ) were 0.005 and 0.015 mg/kg, respectively (calculated as chlorpropanol). The recoveries of the four chloropropanols esters spiked at 0.03, 0.075 and 0.15 mg/kg were between 82.2%–113.9%, with relative standard deviations (RSDs) of less than 8.3%. 3-MCPDE and 2-MCPDE were detected in 100.0% and 42.0% of the 50 infant formula samples with contamination levels in the range of 0.037–0.208 mg/kg and ND–0.060 mg/kg, respectively. However, 1,3-DCPE and 2,3-DCPE were not detected in any sample. The average exposure to CPFAEs in infant formula were 3.86, 2.00 and 1.07 μg/kg for infants aged 0–6, 6–12 and 12–36 months, respectively. Conclusion: The method was easy to operate with good accuracy and reliability, and suitable for the determination of CPFAEs in infant formula. The health risk of CPFAEs through the intake of infant formula for infants should be a major concern.
Surface-Enhanced Raman Scattering Spectroscopy for Qualitative Detection of Carbofuran Residues in Chinese Liquor
TAN Wenyuan, CHEN Yuqin, FU Dayou, WANG Shoufeng, MING Hongmei
2019, 40(10):  318-324.  doi:10.7506/spkx1002-6630-20180329-399
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In this paper, a surface-enhanced Raman scattering (SERS) method was established for the detection of carbofuran residues in Chinese liquor. Au nanoparticles (Au NPS) and Au-core/Ag-shell nanoparticles (Au@Ag NPS) with different thicknesses of Ag shell were prepared, and then their SERS performance were comparatively evaluated by the dye molecule rhodamine 6G (R6G). In alkaline solution, 2,6-dichloroquinone-4-chloroimide as a marker was introduced to carbofuran, and then mixed with the nanoparticles that had better SERS performance in a certain proportion. We optimized the conditions for SERS signal acquisition, compared and attributed the Raman peaks, and estimated the enhancement factor of carbofuran on NPS enhanced substrate. The results showed that Au@Ag NPS with a 7 nm thick Ag shell possessed the best SERS effect, and therefore could be used as the SERS substrate. The limit of detection of carbofuran was 1 × 10-16 mol/L and the enhancement factor of Au@Ag NPS was 2 × 108. Trace carbofuran in all three kinds of commercial Chinese liquor was detected rapidly, simply and reliably by this method.
Determination of Monepantel and Its Metabolite Residues in Dairy Products by High Performance Liquid Chromatography-Tandem Mass Spectrometry
WU Yingxuan, LIN Feng, CHEN Simin
2019, 40(10):  325-330.  doi:10.7506/spkx1002-6630-20180305-045
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A method was developed for the determination of monepantel and its metabolite residues in dairy products by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The sample was ultrasonically extracted with a mixture of saturated sodium chloride solution and acetonitrile, and then the extract was purified by hexane. The target compounds were separated on an inertsil C8 column (2.1 mm × 100 mm, 3 μm) using a gradient elution program with a mobile phase composed of methanol and 0.5 mmol/L ammonium acetate, and detected by tandem mass spectrometry using negative electrospray ionization in multiple reaction monitoring (MRM) mode. The quantification of monepantel and its metabolite residues was performed by the external standard method. The calibration curves showed a good linearity within the concentration range of 0.1–5.0 μg/L and the limit of quantitation (LOQ) was 2.0 μg/kg. The recoveries for dairy products at three spiked levels were in the range of 79.5%–102.9% with relative standard deviations (RSDs) between 2.0% and 5.3%. With the advantages of simplicity, rapidity, accuracy, high sensitivity, strong anti-interference capacity and good recovery and repeatability, the method could be suitable for the analysis of monepantel and its metabolite residues in dairy products.
Adulteration and Purity Detection of Chinese Giant Salamander Meat Powder Based on Near Infrared Spectroscopy
YANG Hui, CHEN Dejing, XIA Donghui, XIN Xi, CHEN Haitao, JIN Wengang
2019, 40(10):  331-336.  doi:10.7506/spkx1002-6630-20180413-180
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In this paper, the adulteration and purity detection of Chinese giant salamander (Andrias davidianus) meat powder were investigated based on near infrared spectroscopy. Infrared spectra of authentic Chinese giant salamander meat powder and adulterated samples with longsnout catfish meat powder, grass carp meat powder or potato starch (40 samples each, 160 samples in total) were collected. After spectral preprocessing, qualitative discrimination models between pure and adulterated samples and among pure sample and adulterated samples with longsnout catfish, grass carp and potato starch) were established by partial least square discriminant analysis (PLS-DA). Partial least squares regression (PLSR) was used to establish a quantitative calibration model for the purity of the three adulterated samples. The results showed that the PLSDA qualitative models with first derivative + multiplicative scatter correction (MSC) spectral preprocessing had the best performance in discriminating the authentic and adulterated samples with 100% predictive accuracy for the calibration and prediction sets. For the PLSR quantitative models of adulteration of longsnout catfish, grass carp and potato starch, the correlation coefficients of the calibration set (Rc 2) were 0.990 6, 0.986 4, and 0.993 3, respectively, and the root mean square errors of calibration (RMSEC) were 1.14%, 1.39%, and 0.88%, respectively. The correlation coefficients of the prediction set (Rp 2) were 0.994 4, 0.992 4, and 0.990 8, respectively, and the root mean squared error of prediction (RMSEP) was 0.83%, 0.89%, and 1.22%, respectively. These results suggest that near infrared spectroscopy combined with chemometrics could be used for adulteration and purity detection of Chinese giant salamander meat powder.
Determination of Glyphosate and Glufosinate-Ammonium Residues in Tea by UPLC-MS/MS
YANG Mei, SUN Si, LIU Wenfeng,WANG Anbo, PAN Chengdan, WANG Jian
2019, 40(10):  337-343.  doi:10.7506/spkx1002-6630-20180404-045
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A rapid method was developed for the determination of glyphosate (GLY) and glufosinate-ammonium (GLUF) in tea using ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The sample was extracted with NaOH solution and after pH adjustment with HCl, the extract was cleaned up with N-(n-propyl) ethyenediamine (PSA), and then was derivatized with 9-fluorenylmethyl chlorformate (FMOC-Cl) in borate buffer solution. The derivatives of GLY and GLUF were detected with positive electrospray ionization-mass spectrometry (ESI-MS/ MS) in the multiple reaction monitoring (MRM) mode. The quantification was performed by external standard method. The method showed a good linearity (r > 0.995) in the range of 0.005–0.50 μg/mL. The limit of detection (LOD) and the limit of quantization (LOQ) were 0.05 and 0.08 mg/kg for both GLY and GLUF, respectively. At spiked levels of 0.08, 0.10, 1.0, 2.0 and 4.0 mg/kg, the recoveries of GLY and GLUF were 75.6%–95.5% and 76.0%–96.6%, with relative standard deviations (RSDs) (n = 10) of 3.24%–8.38% and 3.05%–7.85%, respectively. This method proved to be simple and rapid, and its sensitivity and accuracy could meet the requirements for the simultaneous analysis of GLY and GLUF in tea.