Table of Content

25 March 2020, Volume 41 Issue 6
Food Chemistry
Effect of Malondialdehyde-Induced Protein Oxidation on Structural Properties of Myofibrillar Protein from Silver Carp (Hypophthalmichthys molitrix)
JIANG Yiren, LI Tao, LIU Youming, XIONG Shanbai
2020, 41(6):  1-7.  doi:10.7506/spkx1002-6630-20190411-143
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The impact of secondary products from lipid oxidation on structure and functional characteristics of silver carp myofibrillar protein were studied by using malondialdehyde (MDA) oxidizing systems (0–1.00 mmol/L). The results showed that the contents of carbonyl and free amino groups content changed slightly with increasing MDA concentration from 0.05 to 0.50 mmol/L. The active thiol contents and surface hydrophobicity were enhanced as the malondiadehyde concentration was increased to 0.25 mmol/L, but dityrosine content decreased somewhat; Ca2+-ATPase activity initially decreased and then increased, whereas the opposite trend was observed for its solubility. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) indicated that oxidation promoted the crosslinking and aggregation of myofibrillar protein molecules mainly through disulfide bonds. The increasing MDA concentration resulted in a reduction in α-helix content and an increase in β-sheet content. The results implicate that in the proper concentration range, MDA as a representative of the secondary products of lipid oxidation led to mild oxidation of myofibrillar protein, and the mild oxidation of myofibrillar protein at MDA concentration of 0.25 mmol/L promoted partial unfolding of myofibrillar protein, resulting in exposure of more active sites and consequently protein cross-linking, which might contribute to the formation of surimi gel.
Effect of Different Blend Ratios between Gliadin and Glutenin on Biscuit Quality
YANG Tao, WANG Pei, ZHOU Qin, WANG Xiao, CAI Jian, HUANG Mei, DAI Tingbo, CAO Weixing, JIANG Dong
2020, 41(6):  8-15.  doi:10.7506/spkx1002-6630-20181203-028
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The purpose of this paper was to clarify the effects of different ratios between gliadin and glutenin on the quality of dough and biscuit. Gliadin, glutenin and starch were separated from wheat flour (cv. Yangmai 22) and recombined into low-gluten (8%) flours with predetermined ratios between gliadin and glutenin. The gluten secondary structure and dough rheology of the recombined flours and the quality of biscuits produced from each of them were analyzed. The results showed that with the increase in gliadin/glutenin ratio, the contents of β-sheet and α-helix in gluten proteins decreased gradually, the content of β-turn increased gradually, and the content of free sulfhydryl group decreased linearly; the thermal denaturation temperature (Tp) did not significantly change, but the enthalpy change (ΔH) showed an upward trend. In addition, the storage modulus (G’) and loss modulus (G’’) of the doughs made from recombined flours decreased gradually, while the rheological loss angle tanΔ(G’’/G’) increased gradually, and so did the cohesiveness, adhesiveness and elasticity. The hardness, chewiness, diameter and thickness of biscuits increased gradually, the spread ratio decreased and the color improved with increasing gliadin/glutenin ratio. The sensory score of biscuits increased first and then decreased. In summary, increased gliadin/glutenin ratio led to increased diameter and improved color of biscuits. But excessively higher gliadin/glutenin ratio led to a decrease in gluten viscoelasticity, and imparted an increase hardness, decreased spread ratio and whiter color to biscuits. The optimal ratio of gliadin to glutenin for biscuit making was 6:4.
Effects of Interaction on the Structure and Potential Allergenicity of Ovalbumin and Lysozyme
WANG Wujing, TONG Ping, CHEN Hongbing, GAO Jinyan
2020, 41(6):  16-24.  doi:10.7506/spkx1002-6630-20190124-307
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To understand the effect of protein-protein interactions during heat treatment on the structure and allergenicity of ovalbumin (OVA) and lysozyme (Lys), the interaction between OVA and Lys in egg white at different temperatures was studied. The physical properties including turbidity, solubility and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) profile were analyzed. The spatial structure was characterized by circular dichroism spectroscopy, ultraviolet spectroscopy and fluorescence spectroscopy. Finally, the potential allergenicity of proteins was studied by competitive enzyme linked immunosorbent assay (ELISA). The results showed that OVA-Lys interaction during heating for 10 minutes at 60 and 65 ℃ did not significantly affect the structure and potential allergenicity of each other. However, when treated at 70 ℃, the tertiary structure of OVA was unfolded, and the hydrophobic groups of Lys were exposed outside. Thus, the interaction between OVA and Lys was formed through disulfide bonds and could significantly reduce the potential allergenicity of each other.
Variations in the Contents of Glycerides, 3-Chloropropanol Esters and Glycidyl Esters in Rice Bran Oil with Different Acid Values during Alkali Refining
LIU Yulan, LI Zeze, CHEN Wenyan, ZHANG Jiafeng, MA Yuxiang
2020, 41(6):  25-30.  doi:10.7506/spkx1002-6630-20190218-094
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In the present study, we detected the contents of glycoester, glycidyl ester, 3-chloropropanol ester, glycidyl ester, oryzanol, vitamin E, phytosterol and plasticizer in four crude rice bran oils with different acid values, and two oils with distinct acid values were selected from these oils for alkali de-acidification. Changes in the above indicators were analyzed during alkali refining. The results showed that the contents of triglyceride in the four rice bran oils with acid values in the range of 10.34–23.86 mg/g were 70.31%–84.62%, and the total amounts of glycoester and glycidyl ester were 15.38%–29.69%, which increased significantly with the increase of acid value; the content of 3-MCPDE was 1.44–1.98 mg/kg, and the content of GEs was 0.34–0.55 mg/kg, which showed no clear correlation with acid value. After alkaline refining of the selected rice bran oils, the contents of glyceride and diglyceride decreased but only to a limited extent (on average by 3.27%) with the decrease in acid value, while the contents of 3-MCPD ester and GEs decreased significantly by 26.35% and 33.55% on average, respectively, indicating that alkaline deacidification resulted in partial removal of 3-MCPD and GEs. In addition, 64%–76% of oryzanol, 19.5%–29.8% of VE, and 23.6%–39.3% of sterol were lost during the alkali refining process.
Regulatory Effect of Acidification Rate on Soy Protein Isolate Gels Induced by Glucono-δ-Lactone
LI Qianru, XIONG Yao, LIN Jianuo, YE Qian, MIAO Song, ZHANG Longtao, ZHENG Baodong
2020, 41(6):  31-35.  doi:10.7506/spkx1002-6630-20190420-271
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This study aimed to investigate the effect of acidification rate on the physicochemical properties of soy protein isolate (SPI) gel induced by glucono-δ-lactone. Soy protein gel samples were prepared at different incubation temperatures. pH, turbidity, gel strength, water holding capacity, frequency-sweeping curves and microstructure were measured to evaluate the changes in the acidification rate of glucono-δ-lactone (GS) and the microstructural properties of soy protein gels. The results showed that with the increase in temperature, the release rate of GDL coagulant became faster, and the rate of decline in the pH of the soy protein isolate gel increased. The protein turbidity increased continuously, indicating that the protein aggregation rate increased. The gel system reached a steady state in a shorter period of time, and incubation temperature was proportional to the acidification rate of the protein gel. As acidification rate increased, the gel strength and rigidity of the soy protein isolate gel increased continuously; the water-holding capacity reached a maximum at 60 ℃. The microstructure results showed that the structure of the soy protein isolate gel maintained at 60 ℃ was more uniform and denser. In summary, acidification rate significantly affected the gel structure of soy protein isolate, and the acidification rate at 60 ℃ resulted in the most dense and uniform gel structure.
Preparation, Structural Characteristics and Antioxidant Activity of Polysaccharide-Iron Complex from Fritillaria ussuriensis
ZHANG Man, ZHANG Yu, XU Shaobo, ZHAO Hong, WANG Yuliang, ZHAO Zhimeng, MENG Fanling
2020, 41(6):  36-42.  doi:10.7506/spkx1002-6630-20190410-123
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Objective: To prepare polysaccharide-iron complex from the bulbs of Fritillaria ussuriensis, and to evaluate its physicochemical properties, structural characteristics and antioxidant activity. Methods: The structure of the polysaccharide extracted by water extraction and then alcohol precipitation was chemically modified to obtain its iron complex. Ultraviolet-visible spectroscopy, infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy (SEM), and thermogravimetric-differential thermal analysis were used to determine the physicochemical properties, and structural characteristics of the polysaccharide and its iron complex. Moreover, their antioxidant activities were evaluated by 1,1-dipheny1-2-picryl-hydrazyl (DPPH), superoxide anion and hydroxyl radical scavenging assays. Results: The extraction yield of F. ussuriensis polysaccharide was 4.66%. The characterization confirmed the successful synthesis of polysaccharide-iron complex. The basic structure framework of the polysaccharide was not changed after complexation with Fe3+. In addition, the structural stability of polysaccharide-iron complex was stronger. The complex had stronger radical scavenging effects than the polysaccharide and the maximum scavenging rates were 68.96%, 57.28% and 46.88% for DPPH, superoxide anion and hydroxyl radicals, respectively. Conclusion: The structural stability of F. ussuriensis polysaccharide increased after being modified with Fe3+, leading to a significant increase in the antioxidant activity in vitro.
Comparison of Acid Hydrolysis and Enzymatic Hydrolysis of Dextran
HUANG Ruijie, LI Mei, LIAO Anping, LAN Ping, ZHONG Lei, QIN Qin, LAN Lihong, WANG Xuejiao, WEI Liming, GAN Lanfang
2020, 41(6):  43-50.  doi:10.7506/spkx1002-6630-20190121-241
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In order to obtain dextran with specific molecular mass, dextranase was used to hydrolyze dextran and compared with the traditional acid hydrolysis method. The experimental results showed that both enzymatic hydrolysis and acid hydrolysis could control the molecular mass of dextran, the distribution coefficients of the products were within a reasonable range, with good homogeneity. The enzymatic hydrolysis occurred fast under mild reaction conditions at about 50 ℃, and the products had no chloride ion residue. At about 90 ℃, the acid hydrolysis was carried out at a high reaction rate, but it needed a large amount of acid and alkali, with high energy consumption and serious pollution, and the level of chloride ion residue in the products was 5.89%. Therefore, compared with the acid hydrolysis, the enzymatic hydrolysis had the advantages of lower energy consumption, less pollution and no chloride ion residue, which provides a strong basis for the potential of the enzymatic method as an alternative to the acid method to produce dextran with specific molecular mass.
Effect of Heat-Modified Starch from Laiyang Taro on the Formation and Stability of Emulsions
ZHANG Linlin, ZHU Yuzhu, JIANG Yang, DONG Bin, LI Dapeng, LI Feng
2020, 41(6):  51-57.  doi:10.7506/spkx1002-6630-20190425-325
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In this study, starch was prepared from Laiyang taro tubers and thermally modified. The modified starch was characterized by scanning electron microscopy (SEM), particle size analyzer and X-ray diffraction (XRD). Furthermore, the stabilizing effect of the modified starch on Pickering emulsion was investigated based on particle diameter and stability. Results showed that the average size and zeta potential of the modified starch were 1.560 μm and –20.3 mV, respectively, suggesting that it was more suitable for the preparation of Pickering emulsions than the original starch. Based on emulsion particle size and emulsification index, the optimal conditions for preparing emulsions were determined as follows: pH 7.1, starch concentration 6.25 × 10-2 g/mL, percentage of oil phase 60%, dispersion strength 14 000 r/min and dispersion time 4 min. Moreover, the emulsion formed exhibited high centrifugal stability and thermal stability. These results may provide a basis for broadening the utilization of starch from Laiyang taro and the development of novel emulsion stabilizers.
Effect of Different Oils on Trans Fatty Acid Contents in Deep-Fried Foods
ZHENG Yi, HE Yahong, HE Jiguo
2020, 41(6):  58-63.  doi:10.7506/spkx1002-6630-20190410-133
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Purpose: In this study, we examined the effects of peanut oil, soybean oil, rapeseed oil, 24° palm oil and 42° palm oil on the content of trans fatty acids (TFAs) in deep-fried foods after repeated cycles of continuous frying of French fries, Youtiao (deep-fried twisted dough sticks) and chicken nugget, aiming to provide an experimental basis for the selection of the optimal deep-frying process for foods. Methods: Each oil was used to sequentially process French fries (at 176 ℃ for 2 min and 45 s), Youtiao (at 176 ℃ for 2 min and 30 s) and chicken nugget (at 176 ℃ for 3 min) daily for 5 consecutive days. The fatty acid composition of the three fried foods was investigated using gas chromatography with flame ionization detection (GC-FID). Results: Trans fatty acids were produced during the deep frying of all types of foods with each oil. Fried fries and Youtiao deep-fried in rapeseed oil had the highest contents of TFAs of 38.74 mg/100 g and 37.51 mg/100 g, respectively. All foods deep-fried in palm oil had the lowest content of TFAs, which was 4.98, 6.01 and 4.36 mg/100 g in French fries, Youtiao and chicken nuggets, respectively. Conclusion: In order to reach the lowest content of TFAs in deep-fried foods, 42° palm oil, with better stability, should be used.
Biochemical Characteristics of Rice Flour Sourdough Fermented by Lactic Acid Bacteria and Its Effects on Steaming Characteristics of Steamed Bread
WU Yuxin, CHEN Jiafang, MA Zilin, WU Meng, TANG Xiaojuan, ZHANG Binle, ZHENG Jianxian, HUANG Weining, LI Ning
2020, 41(6):  64-71.  doi:10.7506/spkx1002-6630-20190217-085
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Weissella confuse J28, which has been found to produce exopolysaccharide (EPS), was inoculated to pure rice flour or 10% sucrose incorporated rice flour and cultured at 30 ℃ for 24 h to prepare low-EPS and high-EPS rice flour sourdoughs, respectively. In order to compare the effects of the two sourdoughs on the dough rheology, microstructure and steaming characteristics of steamed bread, biochemical analysis, dynamic rheological test, texture analysis and sensory evaluation were carried out. The results showed that upon the addition of sugar, strain J28 produced 11.12 g/kg EPS in the rice sourdough. This strain produced acids to activate the endogenous enzymes. The amylase activity in the rice sourdough increased first and then decreased, and the soluble sugar content increased. A large amount of fructose and glucose were produced. Increased proteolytic activity was observed, causing degradation of macromolecular soluble gluten. Compared with steamed bread dough incorporated with rice flour at 25%, the elasticity and viscosity moduli of the steamed bread doughs with rice flour sourdough were reduced, and the protein structure was weakened. The dough with high-EPS sourdough was softer. Compared with the control, the sourdough steamed breads had significantly increased specific volume (P < 0.05) and significantly decreased hardness (P < 0.05), with more uniform and smaller pores. The texture of the steamed bread with high-EPS sourdough was better than of the steamed bread with low-EPS sourdough, as manifested by 7.9% increase in specific volume and 28.7% reduction in hardness. Moreover, the sensory score of the steamed bread with high-EPS sourdough was higher and it was more popular with consumers than the other two groups.
Odor Activity Modulation of Aroma Compounds in Spine Grape Wine by Mixed Fermentation of Hanseniaspora uvarum and Saccharomyces cerevisiae
LI Aihua, WANG Lingyun, SU Jun, WANG Qianqian, ZHANG Linyu, TAO Yongsheng
2020, 41(6):  72-78.  doi:10.7506/spkx1002-6630-20190127-349
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The effect of mixed fermentation of Hanseniaspora uvarum (Hu) and Saccharomyces cerevisiae (Sc) on the aroma profile of Spine grape wine were examined to provide technological support for aroma enhancement in wine. Spine grapes (cv. Xiangzhenzhu) were obtained from Hongjiang county, Hunan province. Hu was selected in our laboratory with China Center for Type Culture Collection (CCTCC) accession number M2013658. A commercial Sc yeast powder was used. Winemaking experiments were designed using the dry red winemaking process. Mixed fermentation was divided into three different inoculation strategies, i.e. CF: co-inoculation of Hu and Sc; SF1: Hu inoculation 24 h before Sc; SF2: Hu inoculation 48 h before Sc. Pure Sc fermentation was taken as the control (CK). After the completion of fermentation, the clarification and stabilization of wines were carried out using routine methods. The following April, wine aroma components were analyzed by solid-phase microextraction followed by gas chromatography-mass spectrometry (SPME-GC-MS). Results showed that mixed fermentation decreased the levels of terpenes and C13-norisoprenioids in spine grape wine, but increased the content of thiols. Mixed fermentation enhanced the formation of fermentative aroma compounds. Simultaneous fermentation increased ethyl esters, while sequential fermentation resulted in prominent improvements in acetates and phenyl ethyls. The cumulative odor activity values of volatiles showed that simultaneous fermentation produced more fruity odorants while sequential fermentation gave enhanced floral odor. The aroma quality of Spine grape wine could be improved by mixed fermentation of Hu and Sc by elevating the concentrations of fermentative odorants, and different aroma responses were achieved by different inoculation strategies.
Recombinant Expression and Enzymatic Characterization of Glucose Oxidase in Aconidial Aspergillus niger Strain
LIN Xiaotong, PAN Li, LUO Shiyu, WANG Bin
2020, 41(6):  79-85.  doi:10.7506/spkx1002-6630-20181229-362
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Considering that currently glucose oxidase (GOD), a food-grade enzyme, is industrially produced in low yield, in this study, we chose the glucose oxidase gene goxC from Aspergillus niger CBS513.88 for modification by codon optimization and signal peptide replacement to construct a recombinant strain with high GOD activity. Aconidial A. niger strain SH2, low-background ofsecreted proteins, was used as the host, carrying the high efficient promoter PglaA. Positive transformants were selected using the auxotroph marker pyrG. Catalytic assay of o-dianisidine and SDS-PAGE results showed that the recombinant glucose oxidase with a molecular mass of 80 kDa was successfully expressed in A. niger SH2. The enzymatic activity reached 563.8 U/mL on the 7th day of fermentation in a 500-mL shake flask. In the 50-L tank fermentation, the enzymatic activity attained 1 128 U/mL at 179 h, which was over twice as much as that achieved in the shaking flask fermentation. In the current study, the expression of glucose oxidase was higher than previous literature values in A. niger expression system. This study showed that the optimum temperature and pH of the recombinant glucose oxidase were 45 ℃ and 5.5, respectively. Overall, a recombinant A. niger strain highly effective expression of goxC has been constructed.
Antimicrobial Activities of Lactic Acid Bacteria and Staphylococcus xylosus against Clostridium perfringens
ZHANG Huan, LI Peijun, TIAN Xinglei, CHEN Qian, KONG Baohua
2020, 41(6):  86-92.  doi:10.7506/spkx1002-6630-20190123-302
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The effect of five strains of lactic acid bacteria (LAB) and Staphylococcus xylosus on the growth of Clostridium perfringens was investigated in this study. Mixed culture and conditioned culture were employed to evaluate the effects of these six strains on the growth, sporulation and spore germination of C. perfringens, and the antibacterial mechanism was also investigated. The results showed that Lactobacillus plantarum had the strongest inhibitory effect on C. perfringens growth and its spore germination and growth in both mixed culture and conditioned culture, and S. xylosus possessed the weakest inhibitory effect. None of the six strains could inhibit the sporulation of C. perfringens in the mixed culture, while in the conditioned culture, the sporulation of C. perfringens was inhibited by Lactobacillus fermentum, L. plantarum and Pentosaceus pentosaceus when pre-cultivated for 48 h. Besides, the low pH of the fermented broths of LAB and the heat-resistant bacteriocin produced by L. plantarum were crucial for inhibiting the proliferation of C. perfringens. This result showed that L. plantarum has the highest antibacterial capacity due to its ability to produce both acid and bacteriocin.
Genetic Diversity and Probiotic Characteristics of Intestinal Bifidobacterium Strains Isolated from Uygur Infants in Kashi, Xinjiang
WEI Xiaojing, ZHOU Huancheng, JIN Yamei, CAI Jingjing, NI Yongqing, ZHANG Yan
2020, 41(6):  93-100.  doi:10.7506/spkx1002-6630-20190217-083
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The purpose of this study was to analyze the genetic and species heterogeneity of bifidobacterial strains isolated from the intestinal tract of Uygur infants in Kashi, Xinjiang, and, more broadly, to lay the foundation for exploiting intestinal probiotic bifidobacteria resources from ethnic minority infants. The inter-strain difference in genetic structure was analyzed according to the 16S rRNA gene sequence using rep-PCR fingerprint typing technology. According to the genetic fingerprints, some representative bifidobacteria were selected and tested for their antibacterial activities against 6 common pathogenic bacteria, and the strains with good antibacterial activity were further tested for acid and bile resistance, carbon source metabolism and antibiotic susceptibility. This study found that the 75 strains of Bifidobacterium were assigned to four species and two subspecies, B. bifidum, B. pseudocatenulatum, B. adolescentis, B. longum subsp. infantis and B. longum subsp. suis, respectively. The bacteriostatic tests showed that 16 of the 75 strains had broad-spectrum antibacterial properties. Drug sensitivity test showed that these strains were sensitive or moderately sensitive to all antibiotics except amikacin and vancomycin. The acid and bile salt tolerance tests showed that B. longum subsp. infantis f65-26 and B. pseudocatenulatum f115-8 were the most tolerant strains, which could have great potential for development and utilization.
Screening for a Strain of Lactic Acid Bacteria with Broad-Spectrum Antimicrobial Activity and Analysis of Its Bacteriocin-Related Genes
LIU Shuxin, WU Aijuan, ZHEN Ni, SUN Jie, HUANG Ling, ZENG Zhidan, ZENG Xiaoqun, PAN Daodong
2020, 41(6):  101-107.  doi:10.7506/spkx1002-6630-20190209-035
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Using agar diffusion method, one strain, named B6, with potent and broad-spectrum antimicrobial activity was selected from the 8 strains of lactic acid bacteria (LAB) isolated from traditional yogurt in Xinjiang, China. It was identified as Lactobacillus plantarum by morphological, physiological and biochemical characteristics and 16S rDNA sequence alignment. The cell-free fermented broth of B6 retained its antibacterial activity after sequential removal of acids and hydrogen peroxide, which indicated that L. plantarum B6 could produce bacteriocin. Polymerase chain reaction (PCR) analysis was carried out to identify the bacteriocin genes of B6 by using 10 pairs of primers designed to be specific for the genes related to the biosynthesis of bacteriocin with the total DNA of strain B6 as the template. The results showed that strain B6 had the structural genes plnE/F/J/K for class IIb bacteriocin. The plnJ gene shared 99% similarity with that of L. plantarum C11 with only one amino acid mutation in the leader peptide region, and the plnE/F/K genes shared 100% similarity with those of L. plantarum C11, which indicated that L. plantarum B6 produced class IIb bacteriocin.
Function Evaluation of C-Terminal Domain of Thermoacidiphilic Raw Starch Degrading α-Amylase Gt-amy and Identification of Raw Starch Binding Sites
ZENG Jing, GUO Jianjun, TU Yikun, YUAN Lin
2020, 41(6):  108-115.  doi:10.7506/spkx1002-6630-20190115-159
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To identify the raw starch binding region of the thermoacidiphilic raw starch degrading α-amylase Gt-amy, C-terminal domain (CTD) truncated mutant Gt-amy-T was constructed and its enzymatic properties were characterized and compared with those of Gt-amy. The abilities of Gt-amy and Gt-amy-T to bind to and hydrolyze raw corn starch to evaluate the role of CTD as a raw starch binding domain. Both Gt-amy and CTD displayed comparable affinities for raw corn starch whereas Gt-amy-T was unable to bind to raw corn starch. Gt-amy hydrolyzed raw corn starch efficiently, while Gt-amy-T did not. The kcat of Gt-amy-T was 77.9% of that of Gt-amy with soluble starch as the substrate. Phylogenetic analysis of CTD revealed that CTD was not a typical starch binding domain, but Gt-amy’s CTD was experimentally verified to be raw starch binding domain, which played an important role in raw starch binding and hydrolysis by Gt-amy. CTD contributed to the hydrolysis of soluble starch by Gt-amy. In addition, mutational analysis of Tyr residues in CTD was performed to identify the raw starch binding sites in CTD. The binding capacities of CTD and the mutants to raw corn starch were assayed. The raw corn starch binding and hydrolysis capacities of Gt-amy and Gt-amy W501A/W514A were investigated. The results revealed that the residues W501 and W514 were probably raw starch binding sites in CTD.
Transcriptome Analysis of Lactobacillus paracasei SMN-LBK under Ethanol Stress
GUO Jinfeng, YANG Jie, LI Baokun, JIN Dan, LI Xu, LU Shiling, WANG Qingling, JI Hua, DONG Juan, LI Yingbiao, JIANG Caihong
2020, 41(6):  116-122.  doi:10.7506/spkx1002-6630-20190303-015
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Lactobacillus paracasei SMN-LBK, which was isolated from traditional Koumiss in Tacheng, Xinjiang was subjected to ethanol stress at concentrations of 4%, 6%, 8% and 10%. The corresponding survival rates were 25.84%, 18.39%, 10.86% and 1.67%, respectively. A transcriptomic analysis was carried out on strain SMN-LBK under 10% ethanol stress to study the expression levels of differentially expressed genes at the transcriptional level. The results showed that a total of 50 genes were significantly down-regulated under 10% ethanol stress, including 1 gene involved in alanine, aspartate and glutamate metabolism, 2 genes involved in fatty acid biosynthesis, 8 ATP-binding cassette transporter genes, 3 genes involved in the phosphotransferase system (PTS), and 36 hypothetical protein genes. A total of 28 genes were significantly up-regulated, including 4 genes involved in alanine, aspartate and glutamate metabolism and 24 hypothetical protein genes. Six differentially expressed genes were selected for real-time quantitative polymerase chain reaction (real-time PCR) to verify the transcriptome results, and it turned out that the two methods gave consistent expression levels. These genes are related to the biosynthesis of the main cell wall components peptidoglycans and teichoic acid, which are capable of protecting themselves from damage caused by ethanol stress by increasing the expression of these genes. These genes may be closely related to the ethanol stress mechanism of L. paracasei SMN-LBK. This study lays the foundation for further elucidation of the stress-tolerance mechanism of Lactobacillus.
Optimization of Medium Composition and Fermentation Conditions for Folate Production by Lactococcus lactis KLDS4.0325 by Response Surface Methodology
JIAO Wenshu, GUAN Jiaqi, SHI Jialu, LI Bailiang, LU Jingjing, YAN Fenfen, LI Na, ZHAN Meng, HUO Guicheng
2020, 41(6):  123-130.  doi:10.7506/spkx1002-6630-20190318-210
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This study aimed to select and optimize the critical medium components and fermentation conditions for the production of folate by Lactococcus lactis KLDS4.0325, isolated from koumiss in Northwest China’s Xinjiang. Folate content in the fermentation broth of this strain was determined by high performance liquid chromatography (HPLC). Using one-factor-at-a-time (OFAT) method, yeast extract and glucose were identified as the optimal nitrogen and carbon sources, respectively, and initial pH, the concentration of p-aminobenzoic acid (pABA) and glutamic acid and culture temperature were identified as main factors that influence folate production. The levels of the four factors were further optimized using response surface methodology with Box-Behnken design. The optimal values for initial pH, pABA concentration, glutamic acid concentration and fermentation temperature were determined as 5.40, 42.0 mg/L, 6.30 g/L and 35.40 ℃, respectively. Under these conditions, the yield of folic acid was 0.814 μg/mL, which was 3.13 times higher than that (0.260 μg/mL) before the optimization. This study provides technical support for the industrial production and application of natural folate.
Inhibitory Effect of Mixed Cultures of Lactic Acid Bacteria on N-nitrosamine Production during Sausage Fermentation
LI Xiuming, YANG Hua, WANG Yang, QIU Hongbo, WU Chenyan, XIONG Fengjiao, LIU Jingjing, MA Lizhen
2020, 41(6):  131-138.  doi:10.7506/spkx1002-6630-20190308-105
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In order to evaluate the potential of applying lactic acid bacteria to inhibit the formation of N-nitrosamines during sausage fermentation for improved food safety, four commercial mixed cultures: SHI-59 (Staphylococcus xylosus + S. pentosus + Lactobacillus plantarum), WBX-43 (S. bovis + S. xylose), PRO-MIX5 (S. xylosus + L. sake + L. plantarum), and VBM-60 (S. xylosus + S. pentosus + Lactobacillus) , as well as three pure strains: L. curvatus (Lc), L. pentosus, and L. sake were inoculated into salted sausage fillings at 107 CFU/g, separately. Fermentation was conducted at 35 ℃ after stuffing and filling. At 12, 16, 20, and 24 h, samples were collected to determine the number of lactic acid bacteria. Fermented sausages were by cooking (drying, cooking, smoking, and roasting) each sample, and their sensory quality indicators, pH, and the contents of nitrite, nitrate, 8 biogenic amines and 9 N-nitrosamines were determined. The results showed that the performance of PRO-MIX5 was particularly outstanding. After 12 h of fermentation, the content of nitrite residue was significantly reduced (7.58 mg/kg), the total amount of nine N-nitrosamines was as low as 8.68 μg/kg, and N-nitrosodimethylamine content (2.91 μg/kg) was below the national standard limit. There was no significant increase in the levels of the eight biogenic amines as compared to the control group (P > 0.05). The product had a slightly sour and fermented taste. Besides, Lc could also significantly reduce the total amount of N-nitrosamines to 9.46 μg/kg, but was not effective in reducing nitrite residues (47.73 mg/kg), and increased significantly the total content of biogenic amines. In summary, the commercial starter PRO-MIX5 has the potential to effectively improve the safe of fermented meat products.
Improved Stability of Rice Bran with Composite Membrane Immobilized Enzyme
YU Dianyu, CHEN Shuman, WANG Tong, LI Dan, ZHANG Xue, WU Nan, TANG Honglin, QIN Lanxia, YAO Kai
2020, 41(6):  139-145.  doi:10.7506/spkx1002-6630-20190130-386
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Cellulose acetate (CA) was used to modify a microporous polytetrafluoroethylene (PTFE) membrane, and papain was immobilized on the CA-PTFE composite membrane. The final aim of this study was to investigate the deactivation of lipase in fresh rice bran using the immobilized enzyme membrane. The conditions for deactivating lipase in fresh rice bran were optimized using a combination of one-factor-at-a-time method and response surface methodology. The relative lipase activity was taken as the response. The results showed that the optimal conditions for deactivation of rice bran lipase were determined as follows: ambient air relative humidity 72%, deactivation temperature 71 ℃, and time 113 min. Under these conditions, the relative lipase activity of rice bran decreased to 35.2% indicating good deactivation efficiency. After storage for two months, the relative lipase activity of rice bran remained below 36.0%, and the immobilized enzyme membrane still retained 73.0% of its initial activity after sixth repeated use. Thus, this study concluded that the immobilized enzyme membrane could be repeatedly applied to stabilize rice bran by effectively inactivating lipase.
Dynamic Analysis of Volatile Components of Salted Radish during Different Fermentation Processes
WANG Dongdong, TANG Yao, CHEN Gong, LI Heng, MING Jianying, CAI Difeng, WANG Yong, WU Yalong, ZHANG Qisheng
2020, 41(6):  146-154.  doi:10.7506/spkx1002-6630-20190414-186
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The changes of volatile flavor components during the fermentation of salt radishes with water activities of 0.95, 0.90 and 0.85, respectively simulating the wet, semi-dry and dry state were analyzed by headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). To identify the main components and characteristic volatile components, the data acquired were processed by multivariate statistical analysis (MSA). The results showed that the microflora of wet salted radish was dominated by lactic acid bacteria, while fermentation was very weak or did not occur in the semi-dry and dry state. A total of 61 volatile flavor substances were detected from the three samples fermented for 30 days. Based on principal component analysis (PCA), it was found that 4-methylpentyl isothiocyanate, 1-hexanol, decanal, nonanal, tetrasulfide, dimethyl, acetoin, 1-octen-3-ol, 1-isothiocyanatohexane, 3,5-octadien-2-one, 4-(1-methylpropyl)phenol, 1-heptanol and cis-2-pentenol were identified as typical representatives of the volatile substances. Twelve volatile components were selected with variable importance in the projection (VIP > 1.2) and t-test (P < 0.05) by partial least squares discriminant analysis and hierarchical clustering. Among them, acetic acid was the characteristic component of wet salted radish. 1-penten-3-ol, cis-2-pentenol, 1,1-bis(methylthio)ethane, oxime-, methoxy-phenyl-were the characteristic components of semi-dry salted radish, and hexanoic acid, dimethyl trisulfide, acetoin, 2-pentylfuran, dimethyl tetrasulfide, heptanal, and phenylethyl alcohol were the characteristic components of dry salted radish. These characteristic volatile flavor components could clearly distinguish the three salted radishes. These research results provide a theoretical basis for improving the flavor quality of salted radish.
Effect of α-Lactalbumin on Intestinal Flora in Rats Analyzed by 16S rRNA High-Throughput Sequencing
LI Menghan, WANG Zhiyong, SHENG Xue, CUI Dongying, XI Enze, TANG Mengqi, ZHANG Huikai, XU Xiaoxi, MA Chunli
2020, 41(6):  155-162.  doi:10.7506/spkx1002-6630-20181227-317
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Alpha-lactalbumin (α-LA) is an important immune protein in breast milk. In addition to providing various nutrients such as essential amino acids for infants, α-LA may also regulate intestinal flora. Infant formula contains a lower concentration of α-LA relative to breast milk. Therefore, it is important to explore the effects of different concentrations of α-LA on the diversity and structure of intestinal flora and to determine the appropriate amount of α-LA science added in infant formula. In this experiment, 4 groups of SD rats were orally administered respectively with an equal volume of normal saline (control group), α-LA at high, medium and low concentrations (200, 100 and 20 mg/kg), and colonic feces were aseptically taken after 14 and 28 days of administration. The V3-V4 region of the 16S rRNA gene of the intestinal flora was amplified. Alpha diversity, Beta diversity, and intestinal flora composition at the phylum and genus levels were analyzed by high-throughput sequencing. The results showed that α-LA at high and medium doses improved the species richness, diversity and structure of intestinal microbiota, and the effect was similar to that of breast milk. At the genus level, the high concentration of α-LA reduced the relative abundance of Lactobacillus, Blautia and Akkermansia, while the opposite effect was observed at medium and low concentrations. α-LA at all concentrations decreased the relative abundance of Prevotella and Bacteroides, and the effect was more pronounced with the decrease in its concentration. Moreover, α-LA at all concentrations increased the relative abundance of Eubacterium xylanophilum and maintained the relative abundance of Ruminococcaceae, Clostridium sensu stricto_1 and unknown Lachnospiraceae genera at a constant level. The medium concentration of α-LA enhanced intestinal microbial diversity, and increased or maintained the relative abundance of intestinal probiotics while reducing the abundance of intestinal harmful bacteria, suggesting α-LA at this concentration was optimal to regulate intestinal microbiota. The results of this study provide experimental data for improving infant feeding, and ultimately provide theoretical support for the supplementation of α-LA in infant formula.
Effect of Exopolysaccharides of Lactobacillus helveticus MB2-1 on Growth Characteristics of Ten Probiotics
HUANG Rong, ZHANG Xueliang, HAN Shuo, ZHOU Ziwen, MO Qiaoya, DONG Mingsheng, RUI Xin, ZHANG Qiuqin, CHEN Xiaohong, LI Wei
2020, 41(6):  163-169.  doi:10.7506/spkx1002-6630-20190811-124
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This study evaluated the effects of the exopolysaccharides (EPS) produced by Lactobacillus helveticus MB2-1 and its purified components on the growth characteristics of probiotics in order to gain further insights into the probiotic function of the EPS of L. helveticus MB2-1. The optical density (OD600 nm) values of ten probiotics and two pernicious strains continuously cultured in a medium with EPS or EPS-2, the most abundant component separated and purified from EPS, as the sole carbon source were determined. The residual amounts of total EPS and the amounts of short-chain fatty acids (SCFA) produced in 10 probiotics during 48 h of culture were measured by high performance liquid chromatography (HPLC). The results showed that the 10 probiotics could grow and reproduce at different rates in the medium with EPS or EPS-2 as the sole carbon source. Among them, Enterococcus faecium MN-1grown in EPS showed a maximum growth rate of 0.225 h-1 at 11.56 h. The growth of the two pernicious strains was inhibited to a certain extent compared with normal glucose medium. Lactic acid was produced in larger amounts than other SCFA. L. paracasei was the most efficient producer of lactic acid, and at 48 h of fermentation, the lactic acid concentration reached 57.6 mmol/L, which increased by 121.7% as compared with 26.1 mmol/L at the beginning of fermentation. This study demonstrated that the EPS derived from L. helveticus MB2-1 is a good carbon source for the ten probiotics and can be used as potential prebiotics to regulate intestinal health in humans and animals.
Synthesis of Resveratrol from Peanut Wastes by Biotransformation of Phomopsis liquidambari B3
LIU Lianhong, CHEN Fei, GUAN Yongxiang, QIU Meihua, ZHANG Li, DAI Chuanchao
2020, 41(6):  170-178.  doi:10.7506/spkx1002-6630-20190203-014
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This study examined the effect of fermentation with Phomopsis liquidambari B3 on increasing the resveratrol content in the peanut wastes. The resveratrol biosynthesis pathway was elucidated by identifying metabolites and analyzing the key enzyme genes in this pathway using real-time quantitative PCR. The results showed that B3 could secrete β-glucosidase to transform piceid in peanut wastes to resveratrol. It could also transform p-coumaric acid in peanut wastes to resveratrol via de novo synthesis. On this basis, the optimization of fermentation conditions for improved resveratrol conversion efficiency was carried out using one-factor-at-a-time method and response surface methodology. A ratio of solid to liquid of 1:30 (g/mL), an initial medium pH value of 5.2, an inoculum amount of 9%, a fermentation temperature of 28.6 ℃ and a rotating speed of 204 r/min were found to be the optimal conditions to obtain a higher yield of reveratrol. After 36 h fermentation in a 5 L fermentor, the content of resveratrol was increased by 1.9 times as compared with that before fermentation. The results confirmed that fermentation with P. liquidambari B3 could significantly increase the content of resveratrol in peanut wastes. This study is of great guiding significance for the development of high value-added products from peanuts and for wider comprehensive utilization of peanuts.
Salt Stress Enhanced Selenium Enrichment in Lactobacillus rhamnosus
XU Ying, WU Shufang, YANG Fulian, YU Haixia, HE Jiaxuan
2020, 41(6):  179-183.  doi:10.7506/spkx1002-6630-20190221-129
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Lactobacillus rhamnosus (ATCC 53103) was cultured 37 ℃ in an MRS medium containing 1 mL of 6% NaCl per 15 mL and 10 μg/mL sodium selenite at pH 6.4. The selenium content of the dried biomass was determined to be up to 452.43 μg/g by inductively coupled plasma-atomic emission spectrometry and the selenium enrichment efficiency was calculated as 43.33%. Compared with the unstressed control group, the selenium content and selenium enrichment efficiency were improved by 122.72 μg/g and 13.17%, respectively. Black microparticles were observed both inside and outside the selenium-enriched L. rhamnosus cells by transmission electron microscopy, which was proved to be elemental selenium by energy dispersive X-ray spectroscopy (EDAX). The selenium content increased after salt stress, which further proved that salt stress promoted the selenium enrichment of L. rhamnosus.
Effects of Fermenter Type on the Quality of Zhejiang Rosy Vinegar
FANG Guanyu, MU Xiaojing, JIANG Yujian
2020, 41(6):  184-192.  doi:10.7506/spkx1002-6630-20190129-377
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In this study, a reflux stirring fermenter, a pneumatic stirring fermenter and a mechanical stirring fermenter were separately used for mechanized brewing of Zhejiang rosy vinegar after adding water. The yield, organic acid composition, and volatile components of Zhejiang rosy vinegar were determined after the completion of fermentation. The results showed that the yield of Zhejiang rosy vinegar made from 1 kg of rice was increased from 7.84 kg to 8.25 and 8.13 kg by using the pneumatic stirring fermenter and the mechanical stirring fermenter with a stirring frequency of once every five days compared with the traditional fermenter, respectively. The content of lactic acid in rosy vinegar produced using the reflux stirring fermenter was relatively high, and the content of non-volatile organic acid in rosy vinegar was increased by using the pneumatic stirring fermenter. Principal component analysis and cluster analysis showed that different fermenters had a great effect on organic acid composition of Zhejiang rosy vinegar whereas stirring frequency had little effect. The amino acid content increased with the increase in stirring frequency. The amount of volatile components produced by using the reflux stirring fermenter was significantly lower than that obtained using the other fermenters. Principal component analysis and cluster analysis showed that different fermenters had a significant influence on volatile components while stirring frequency had little influence. The quality of the rosy vinegar produced by using the pneumatic stirring fermenter with a stirring frequency of once every five days was the closest to that of traditional rosy vinegar.
Effect of mtnN Gene on Biosynthesis of S-Adenosylmethionine in Bacillus amyloliquefaciens
RUAN Liying, WEN Zhiyou, WEI Xuetuan
2020, 41(6):  193-200.  doi:10.7506/spkx1002-6630-20190124-316
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In order to explore the effect of mtnN on S-adenosylmethionine (SAM) synthesis in Bacillus amyloliquefaciens, a series of genetically engineered strains with modifications in the mtnN gene were constructed by gene knockout and antisense RNA suppression technology in this study. Compared with the original strain HZ-12, the SAM yield and biomass of the mtnN-deleted strain decreased by 51% and 26%, respectively, indicating that complete blocking of the mtnN gene is not conducive to cell growth and SAM synthesis. Furthermore, the expression of mtnN was inhibited by antisense RNA fine-tuning. Compared with the control strain HZ-12/pHY300, the biomass of the engineered strains HZ-12/pHY-mtnNasRNA-1, HZ-12/pHY-mtnNasRNA-2 and HZ-12/pHY-mtnNasRNA-3 showed no significant difference from each other, and their SAM yields reached 14.58, 12.27 and 12.49 mg/L, respectively, increasing by 44%, 22% and 24% compared with the control, respectively. This study not only explains the influence of mtnN gene on SAM synthesis, but also provides a new strategy for construction of high-yield SAM producing engineered strains.
Changes in Abundance of Inoculated Akkermansia muciniphila in an In Vitro Model Gut System
WANG Lei, YAO Hong, TANG Xin, WU Xiyang
2020, 41(6):  201-206.  doi:10.7506/spkx1002-6630-20190218-102
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We collected 131 human fecal samples from Guangzhou, Guangdong to analyze the colonization rate of Akkermansia muciniphila. Then, we chose the feces without A. muciniphila for use as the inoculum in an in vitro model gut system and 1 × 108 CFU/mL of A. muciniphila was spiked into the system to evaluate the colonization ability of A. muciniphila by real-time quantitative polymerase chain reaction (real-time PCR) and high-throughput sequencing. The results of real-time PCR showed that the colonization rate was 89.31% and the average abundance was 5.825 (lg(CFU/mL)). The abundance of A. muciniphila changed slightly in the first 24 h. The growth of Lactobacillus was stimulated whereas the growth of Bifidobacterium and Bacteroides were inhibited. The results of next-generation sequencing (NGS) showed that the microbial profiles before and after intervention with A. muciniphila were not significantly different. In conclusion, A. muciniphila had the ability to colonize and it did not perturb the intestinal microbiota.
Differences in Physicochemical Properties and Prokaryotic Microbial Communities between Young and Old Pit Mud from Chinese Strong-Flavor Baijiu Brewing
ZHANG Huimin, WANG Yanli, MENG Yajing, WANG Yinhui, LI Anjun, WANG Zhiqiang, ZHANG Zhizhou, XING Xinhui
2020, 41(6):  207-214.  doi:10.7506/spkx1002-6630-20190226-190
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In this study, the differences in physicochemical properties and bacterial community structure between young and old pit muds (PMs) used to produce Chinese strong-flavor Baijiu were analyzed. pH and ammonium nitrogen, acetic acid and K+ contents were relatively higher in old PMs than in young PMs, while the contents of ethanol, propionic acid, lactic acid, ethyl hexanoate, soluble Ca2+ and total ester were relatively higher in young PMs than in old PMS. Young PMs were richer in Lactobacillus while old PMs were richer in Clostridium, Syntrophomonas, Methanoculleus, Aminobacterium and Sedimentibacter. The Pearson correlation analysis suggested that the bacterial interaction in old PMs was more complex compared with young PMs. The canonical correlation analysis (CCA) between physicochemical properties and prokaryotic microbial communities suggested that pH value and the contents of ammonium nitrogen, acetic acid and K+ were positively correlated with the old PM bacterial communities while the contents of lactic acid, total ester, ethanol, propionic acid and Ca2+ were strongly positively correlated with the young PM bacterial communities. This study provides a theoretical basis for the improvement of artificial/degraded PM.
Component Analysis
Analysis of Flavor Characteristics and Volatile Compounds of Kangzhuan Tea
ZHANG Ting, NI Hui, WU Ling, HU Yang, WU Yinglong, HUANG Gaoling, LI Lijun
2020, 41(6):  215-221.  doi:10.7506/spkx1002-6630-20190115-179
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In this paper, the aroma characteristics of Kangzhuan tea were analyzed by sensory evaluation, gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O). The results of sensory evaluation showed that floral and woody notes were the main aroma profiles of Kangzhuan tea. By GC-MS analysis, a total of 35 volatile compounds were identified. Among them, 1,2,3-trimethoxybenzene (151.7 μg/mL), dihydroactinidiolide (96.9 μg/mL), 2-ethylhexanol (37.7 μg/mL), cedrol (34.8 μg/mL) and phenylacetaldehyde (25.5 μg/mL) were more abundant than the other volatiles. GC-O results showed that trans-2-nonenal (green), trans-β-ionone (floral), linalool (floral), hexanal (green), phenylacetaldehyde (green), trans-α-ionone (woody and stale) and linalool oxide I (floral) were the main flavor-active compounds. The results of this study lay an experimental foundation for further study on the aroma characteristics of Kangzhuan tea.
Dynamic Changes in Aroma, Functional Components and Hypoglycemic Effect in Vitro of Red Raspberry Wine during Fermentation
RAO Yanyan, SANG Ying, TANG Linlin, CHEN Sirui, FENG Jianwen, FU Maorun, LIU Yamin, WANG Jinling
2020, 41(6):  222-230.  doi:10.7506/spkx1002-6630-20190408-062
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The dynamic changes of functional components (active components and organic acid contents) and aroma components of red raspberry wine made from frozen red raspberries were studied at different fermentation stages. Based on the inhibitory rates of α-glucosidase and α-amylase, we investigated the changes of hypoglycemic effect in vitro during the brewing of red raspberry wine. The results showed that the alcohol content (V/V) increased first and then tended to be stable during the fermentation of raspberry wine, and at the end of aging it was up to (18.00 ± 0.07)%. Active components contents and the inhibition rates of α-glucosidase and α-amylase increased first and then decreased during the brewing process, and both total phenol and anthocyanin contents reached the maximum of (153.32 ± 2.26) and (173.64 ± 5.72) mg/L on the first day of fermentation, respectively. The contents of flavonoid and proanthocyanidin reached the maximum value of (67.03 ± 0.30) and (6.38 ± 0.04) mg/L on the 9th and 5th day, respectively. The inhibition rates of α-glucosidase and α-amylase reached the maximum of (90.18 ± 0.77)% and (87.93 ± 2.10)% on the 5th and 1st day, respectively. During the fermentation process, L-malic acid content increased, citric acid content decreased, and the content of other organic acids increased first and then decreased, with the greatest changes being observed in the contents of succinic acid and lactic acid. During aging, L-malic acid content increased slowly, succinic acid content increased first and then decreased slowly, while the contents of citric acid, lactic acid, oxalic acid, tartaric acid and shikimic acid decreased continuously. A total of 18 aroma components were detected in fresh red raspberry juice, and 46 and 23 aroma components were detected during the fermentation and aging of red raspberry wine, respectively. The main aroma components of raspberry juice were ketones (63.40%), and the content of ketones decreased and the contents of alcohols and esters increased after fermentation. The main aroma components in raspberry wine were ester, ethyl decanoate, ethyloctanoate and isoamylformate, which were responsible for the characteristic aroma.
Quality Characteristics and Aroma Components of Three Fresh Edible Cultivars of Canarium album Grown in Fuzhou
LAI Ruilian, FENG Xin, CHEN Jin, CHEN Yiting, WU Rujian
2020, 41(6):  231-238.  doi:10.7506/spkx1002-6630-20190419-255
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In this research, the fruit quality characteristics and aroma components of the main fresh edible cultivars (FECs) of Canarium album grown in Fuzhou, Fujian: ‘Lingfeng’, ‘Minqing 2’ and ‘Qinglan 1’ were studied to provide a theoretical basis for breeding of new cultivars with improved quality traits. Principal component analysis (PCA) and cluster analysis were used for comprehensive evaluations. Results showed that 12 quality parameters including total acid (TA), total sugar (TS), total polyphenol, crude polysaccharide and total soluble solid (TSS) contents significantly differed among the three FECs. The quality of the cultivars could be ranked in terms of both TSS/TA and TS/TA ratio as follows: ‘Lingfeng’ > ‘Minqing 2’ > ‘Qinglan 1’. By using the two principal components extracted by PCA, a comprehensive quality evaluation model was established as f = 0.686f1 + 0.314f2, and the FECs were ranked in the decreasing order of synthetic quality score: ‘Lingfeng’ > ‘Qinglan 1’ > ‘Minqing 2’. A total of 35 aroma components were detected in all FECs, mainly including olefins, as well as lesser amounts of alcohols, phenols, esters and other chemical compounds. Notably, caryophyllene was the most abundant aroma component of all cultivars. The aroma compounds of the FECs could be divided into two main categories, and a comprehensive aroma evaluation model was developed as F = 0.597F1 + 0.403F2. The FECs were ranked in the decreasing order of aroma characteristics: ‘Qinglan 1’ > ‘Minqing 2’ > ‘Lingfeng’. Cluster analysis revealed that ‘Lingfeng’ and ‘Qinglan 1’ shared similar quality characteristics, while ‘Minqing 2’ and ‘Qinglan 1’ were similar in aroma components. The results obtained in this research indicated that the quality characteristics and aroma components of C. album varied greatly among cultivars. Thus, the combined use of mathematical models and sensory evaluation is essential for accurate quality evaluation of C. album. In addition, olefins were the major aroma components of C. album, and caryophyllene might be one of the important factors contributing to its characteristic flavor. Our present study provides a scientific basis for the development of the fresh edible C. album industry.
Effects of Potato Flour on Volatile Flavor Compounds in Noodles
ZHENG Kaidi, LIANG Shan, ZHANG Min, ZHU Yong, LI Xinping
2020, 41(6):  239-245.  doi:10.7506/spkx1002-6630-20190412-162
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The volatile flavor substances of noodles incorporated with potato flour to replace wheat flour at different levels were determined by electronic nose analysis combined with headspace solid phase microextraction followed by gas chromatography-mass spectrometry (HS-SPME-GC-MS). The effects of potato flour and noodle types (fresh and dried) on the flavor and volatile odor of cooked noodles were studied by using two-way analysis of variance, principal component analysis, cluster analysis and loading analysis. The electronic nose was found to be effective in accurately distinguishing noodles with different amounts of added potato flour. The volatile odor of 6 kinds of noodles differed mainly in inorganic sulfur compounds and short-chain alkanes. Aldehydes were found to be the main flavor compounds of noodles. With increasing amount of potato flour addition, the volatile odor of noodles was enhanced significantly, and the flavor compounds in fresh noodles become more abundant. The fresh and dried noodles incorporated with 20% potato flour showed similarities in odor, but there were still differences in the content of flavor substances. The top three most abundant volatile flavor compounds were hexanal, n-hexanol and 2-pentylfuran in the fresh potato flour incorporated noodles; and 2-pentylfuran, hexanal and (E)-2-nonenal in the dried potato flour incorporated noodles. Both the types of noodles and the addition of potato flour significantly affected the flavor of noodles, with the latter being more effective than the former. Geranyl acetone was found only in the potato flour incorporated noodles, which was directly related to the addition of potato flour to the recipe. The results showed that the addition of potato flour had a great effect on the volatile flavor of noodles.
Analysis of Nutritional and Functional Components and Taste Amino Acids of Different Commercial Brands of Sufu Paste
ZHANG Jianping, XIE Chunzhi
2020, 41(6):  246-251.  doi:10.7506/spkx1002-6630-20191015-138
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The main nutritional and functional components of different commercial brands of sufu paste including two brands from Beijing: BJ-1 and BJ-2, one brand from Hebei (HB), one brand from Shanghai (SH), and one brand from Guangdong (GD) were quantitated and compared, and the taste amino acids were analyzed by principal component analysis (PCA). The results showed that the nutritional and functional components were abundant in sufu paste, and significantly different among brands (P < 0.05). Compared with other brands, the contents of puerarin (12.18 mg/100 g), γ-aminobutyric acid (13.67 mg/100 g), stigmasterol (0.07 mg/100 g) and β-sitosterol (0.13 mg/100 g) in BJ-1 were the highest; the content of puerarin was about 2.5 times as high as that of HB and the content of β-sitosterol was 4 times as high as that of BJ-2. A total of 15 free amino acids were detected, among which, glutamate was the most abundant, followed by leucine. According to the taste characteristics, MSG-like amino acids were dominant in HB, BJ-2 and SH, while bitter amino acids were slightly prevailing in BJ-1 and GD. Sweet and tasteless amino acids were the least abundant. Principal component analysis (PCA) showed that the cumulative contribution of the first four principal components accounted for 92.70% of the total variance, which could well represent the taste amino acid composition. The comprehensive evaluation scores of taste amino acids decreased in the following order: GD > HB > BJ-1 > BJ-2 > SH.
Processing Technology
Decolorization and Antioxidant Activities of Peptides from Neptunea cumingi Muscle Protein Hydrolysate
ZHANG Shanshan, LI Xiaobin, ZHANG Xuanming, HAN Liwen, LIU Kechun
2020, 41(6):  252-258.  doi:10.7506/spkx1002-6630-20190527-334
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Crude peptides were prepared from Neptunea cumingi muscle by using acid-alcohol extraction. By using the response surface methodology, the conditions for decolorizing the crude peptides were optimized as follows: activated carbon amount 0.42%, reaction temperature 52 ℃, reaction time 50 min and pH 7.4. Under these conditions, the retention rate of peptide was (67.63 ± 0.80)% and the decolorization rate was (68.70 ± 0.54)%. Furthermore, antioxidant activities of the purified peptides were evaluated both in vitro and in vivo. The half maximal effective concentration (EC50) for 1,1-diphenyl-2-trinitrobenzene hydrazine (DPPH) radical scavenging was 170.041 μg/mL. The in vivo antioxidant tests showed that the peptides showed similar activity to the positive control VC at a concentration of 50 μg/mL in a zebrafish model. In addition, at 200 μg/mL, the peptides could inhibit oxidative damage induced by metronidazole. The total amino acid content of the peptides was 853.46 mg/g. The amino acid composition was determined by precolumn derivatization. It was found that alkaline and acidic amino acids together accounted for about 80% of the total amino acids, and arginine, alanine and proline were the most abundant amino acids.
Preparation of Blueberry Anthocyanin Extract by Ultrasound-Assisted Flash Extraction and Evaluation of Its Anti-Tumor Activity in Vivo and in Vitro
XUE Hongkun, TAN Jiaqi, LIU Chenghai, LIU Chai
2020, 41(6):  259-269.  doi:10.7506/spkx1002-6630-20190411-159
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Ultrasonic-assisted flash extraction (UFE) was employed to extract anthocyanins from blueberry fruit. The effects of ultrasonic power, flash extraction speed, extraction time, solid-to-liquid ratio and ethanol concentration on the yield of anthocyanins were investigated. A combination of one-factor-at-a-time method and genetic algorithm was used to optimize the extraction parameters. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and Annexin V-FITC/PI double label staining were employed to investigate the effects of the anthocyanin extract at different concentrations on proliferation and apoptosis of S180 cells. Its in vivo antitumor activity was tested using an S180 tumor-bearing mice model and enzyme-linked immunosorbent assay (ELISA). The results showed that the optimum extraction conditions that provided the highest yield of anthocyanins of (2.71 ± 0.08) mg/g were obtained as follows: extraction time 10 min, ultrasonic power 450 W, flash extraction speed 8 400 r/min, solid-to-liquid ratio 1:30 (g/mL) and ethanol concentration 68%. The content of anthocyanins in the resulting extract was (31.79 ± 0.53)%. In vitro tests showed that the anthocyanin extract could remarkably inhibit proliferation, induce apoptosis of S180 cells, and block the cells in S phase. In vivo anti-tumor tests showed that the masses of tumors treated with the anthocyanin extract at low, medium and high doses were significantly lower than that of the model control group (P < 0.05) and the anti-tumor rates were 26.36%, 33.33% and 46.51%, respectively. The levels of IL-12 and TNF-α in the serum of tumor-bearing mice treated with the anthocyanins at the three doses were significantly higher than those of the model control group (P < 0.05), while the serum level of IL-10 was significantly lower than that of the model control group (P < 0.05). In conclusion, UFE is an efficient method for anthocyanins extraction, and the anthocyanin extract can inhibit the growth of tumors by inducing apoptosis and enhancing immunity.
Optimization of Extraction of Rose Essential Oil by High Intensity Pulsed Electric Field Combined with Enzymatic Treatment-Assisted Steam Distillation
ZHOU Yajun, LI Shengrao, WANG Shujie, XUE Changmei, YAO Guangming
2020, 41(6):  270-277.  doi:10.7506/spkx1002-6630-20191104-042
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In order to explore a high-efficiency method for extracting rose essential oil, the extraction of rose essential oil by combined use of high intensity pulsed electric field (PEF), celluase hydrolysis and steam distillation was optimized by one-factor-at-a-time method and response surface methodology coupled with Box-Behnken. The composition of the essential oil was analyzed by gas chromatography-mass spectrometry (GC-MS). The results showed that compared with single and enzyme-assisted steam distillation extraction, PEF followed by enzyme-assisted steam distillation increased the oil yield by about 43.83% and 20.48%, and shortened the extraction time by 25% and 40%, respectively. The optimal parameters of PEF followed by enzyme-assisted steam distillation were obtained as follows: distillation time 1.7 h, pulse number 10, and electric field strength 21 kV/cm. Under these conditions, the oil yield was 0.116 5%. A total of 63 components were identified from the essential oil, accounting for 95.04% of the total essential oil. PEF combined with enzymatic treatment could promote the release of essential oil components and as a result, provide an efficient method for the extraction of rose essential oil.
Safety Detection
Identification of Watercore in Xinjiang-Grown Fuji Apples Based on Reflection-Transmission Hyperspectral Imaging
GUO Junxian, MA Yongjie, TIAN Haiqing, HUANG Hua, SHI Yong, ZHOU Jun
2020, 41(6):  278-284.  doi:10.7506/spkx1002-6630-20181204-044
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In this research, hyperspectral technique combined with chemometrics was used to discriminate between Xinjiang-grown Fuji apples with and without watercore. Visible and near infrared hyperspectral images were acquired within the wavelength range of 380 to 1 004 nm. The region of interest was selected from the images to calculated average spectra. The original spectra were preprocessed by 9 different methods such as direct difference first-order derivative, and then principal component analysis (PCA), independent component analysis and correlation coefficient method were used to reduce the dimensionality of the spectral data. Finally, Bayes discriminant, K nearest neighbor method, Mahalanobis distance discriminant, least squares support vector machine, quadratic linear discriminant method were combined to perform pattern recognition. Results indicated that 15 principal components were extracted by PCA. The model developed using standard normal variate (SNV) or multiple scatter calibration (MSC) combined with PCA and least squares support vector machine (LSSVM) exhibited the best recognition performance with identification rates for the calibration and prediction sets of 100% and 91.2%, respectively.
Influence of Aging in Different Oak Barrels on Volatile Sulfur Compounds in Wines
YE Dongqing, ZHENG Xiaotian, LI Ying, DUAN Changqing, LIU Yanlin
2020, 41(6):  285-291.  doi:10.7506/spkx1002-6630-20190117-204
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The influence of different geographic origins (the United States, Hungary and France) and toasting levels (light and medium) of oak barrels on the evolution of volatile sulfur compounds (VSCs) in wine during maturation was investigated in this study. Wines aged in stainless steel tanks were used as the control. Gas chromatography with flame photometric detection (GC-PFD) was used to monitor the changes of 16 VSCs in wines during the year of aging, and 7 VSCs were quanti?ed in all samples. Most VSCs tended to decline or changed slightly during the aging process, while the contents of dimethyl sulfide and ethyl thioacetate were found to increase. After one-year aging, the levels of most VSCs were lower in the wines aged in oak barrels than in stainless steel tanks. Multi-way analysis of variance (ANOVA) showed that the geographic origin of oak barrels signi?cantly in?uenced the concentrations of S-methyl thioacetate and 2-methyltetrahy-drothiophen-3-one (P < 0.001), while the toasting level of oak barrels signi?cantly in?uenced the concentration of 2-(methylthio) ethanol (P < 0.001). This study reported the evolution of VSCs in wines during oak barrel aging and evaluated the influence of oak barrel types on it, which would provide wine-makers with useful information for wine oak barrel aging.
Simultaneous Determination of Pinoxaden and Clodinafop-Propargyl and Cloquintocet-Mexyl Residues in Barley by High Performance Liquid Chromatography-Tandem Mass Spectrometry
HAN Hedan, SHE Yongxin, HE Yongjuan, HE Yahui, WANG Mengqiang, WANG Miao, WANG Shanshan, ZHENG Lufei, CAO Zhen, SHAO Hua, JIN Maojun, JIN Fen, WANG Jing, GAO Liping
2020, 41(6):  292-297.  doi:10.7506/spkx1002-6630-20181106-066
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An analytical method for simultaneous determination of the results of two herbicides, pinoxaden, clodinafop-propargyl, and the herbicide safety agent cloquintocet-mexyl in barely was developed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) combined with quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction. The samples were extracted with acetonitrile, and cleaned up with C18 and N-propyl ethylenediamine (PSA). The analytes were then separated with a reversed phase C18 column (XBridge) by gradient elution with a mixture of 0.1% formic acid solution and acetonitrile as the mobile phase. The instrument was operated under the multiple reaction monitoring (MRM) mode with positive electrospray ionization and the analytes were quantified?by matrix matched external standard method. Good linearity was obtained in the concentration range of 0.1–100 μg/L with correlation coefficients no less than 0.999 6. The limits of detection (LODs) of the method were 0.05, 0.02 and 0.01 μg/L for pinoxaden, clodinafop-propargyl and cloquintocet-mexyl, respectively. The average recoveries of the analytes at three spiked concentration levels (determined according to the residue limits of the national standard for wheat) were 76.87%–103.55%. The repeatability, expressed as relative standard deviations (RSD), ranged from 2.4% to 9.2% (n = 5). The method confirmed its applicability to marketed barley grains and seedling flour. This method provides technical support for the determination of pinoxaden residues in barley products.
Identification of Lotus Seed Flour Adulteration Based on Near-Infrared Spectroscopy Combined with Deep Belief Network
HU Renwei, YU Yue, NI Minglong, YU Jiao, ZHOU Junwei, ZHU Cheng, LI Zhanming
2020, 41(6):  298-303.  doi:10.7506/spkx1002-6630-20190125-325
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We developed a near-infrared (NIR) spectroscopic method for rapidly identifying the adulteration of lotus seed flour. The spectral data of lotus seed flours mixed with different other crop flours at different levels were classified using support vector machine (SVM). On this basis, deep belief network (DBN) was employed for discrimination of lotus seed flours with unknown adulterants. The results showed that the average recognition rate of the SVM model for adulteration of the other crop flours was 98% (training numbers ≥ 600). Based on the DBN model, lotus seed flour adultered with the other crops could be effectively identified and the average recognition rate for very few adulteration levels was about 96% (training numbers ≥ 600). The DBN model avoided the disadvantages of the current deep neural networks such as local optimization and not using massive labelled samples. NIRs combined with DBN provides a new alternative for the rapid detection of adulteration of agricultural products.
Migration of Capsaicinoids from Spicy Hot Pot Soup into Foodstuffs during Cooking
YANG Li, JIA Hongfeng, SONG Lushan, HUANG Ying, ZHANG Miao
2020, 41(6):  304-309.  doi:10.7506/spkx1002-6630-20181228-335
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In this study, 16 types of foodstuff were separately cooked thoroughly in boiling beef tallow hot pot or vegetable oil hot pot soup. High performance liquid chromatography was applied to detect the content of capsaicinoids in the cooked foodstuffs and the oil and water phases of hot pot soups. The pungency of the cooked foodstuffs was evaluated using a sensory panel. Based on all the results obtained, the pattern of migration of capsaicinoids was analyzed and the absorption coefficient of capsaicinoids was determined. It was found that the pungency of cooked foodstuffs was related to foodstuff type and the amount of capsaicin and dihydrocapsaicin absorbed. The amount of capsaicinoids absorbed by foodstuffs was related to the content of capsaicinoids in hot pot soup, capsaicinoid type, and oil or fat used in hot pot soup. The absorption coefficient of capsaicinoids was higher after being cooked in the water phase than in the oil phase of hot pot soup, and the value for some foodstuffs was greater than 1. Beef tallow hot pot soup imparted pungency to meat more slowly than to leaf vegetables, whereas the reverse was true for vegetable oil hot pot soup. The pungency of cooked foodstuffs in hot pot soup was affected by a combination of various factors. Understanding those factors may provide a scientific guidance for developing a healthy diet.
Determination Six Cations in Chinese Liquor, Red Wine, Beer and Several Kinds of Yellow Wine by Ion Chromatography with Conductivity Detection
MAO Jiatian, ZHOU Wanqing, Pavel N. NESTERENKO, YE Mingli, XIE Guangfa, CHEN Meilan
2020, 41(6):  310-315.  doi:10.7506/spkx1002-6630-20190414-187
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A new ion chromatographic (IC) method was developed for the determination of alkali metal (Li+, Na+, and K+), alkali-earth metal (Mg2+ and Ca2+) cations and ammonium (NH4+) in four types of alcoholic beverages including yellow rice, Chinese liquor and red wine and beer. The separation of cations was performed on IonPac CG16 (5 mm × 50 mm) and IonPac CS16 (5 mm × 250 mm) columns connected in series with 30 mmol/L methanesulfonic acid as an eluent. The calibration plots obtained for conductivity detection of the separated cations showed a good linearity with regression coefficients (r2) > 0.999 0 and the method presented good reproducibility with low values of relative standard deviation (RSD) ≤ 5.52 (n = 6). The results of IC analysis indicated the presence of ammonium in 18 brands of yellow rice wines at concentrations ranged from 137.00 to 284.01 mg/L and in beer and red wine at concentrations ranged from 28.29 to 42.88 mg/L, but the absence of ammonium in Chinese liquor. A further investigation revealed that the elevated concentration of ammonium in yellow rice wine was due to the presence of proteins in the raw materials, indicating the ammonium concentration depends on the fermentation degree. At the same time, no correlation between ammonium content and age was found for yellow rice wine. The concentrations of alkali metal and alkaline-earth metal cations were the lowest in Chinese liquor as compared with the other types of beverages studied, which could be due to distillation during its production. It was also found that the concentration of K+ in red wine was significantly higher than in the other types, which was attributed to the higher content of potassium in red grapes.
Discrimination of Different Geographical Origins of Tan Sheep Meat Based on Mineral Element Fingerprints
MA Mengbin, LUO Ruiming, LI Yalei
2020, 41(6):  316-321.  doi:10.7506/spkx1002-6630-20190218-097
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The geographical traceability indicators were selected by analysis of the differences in mineral element contents of Tan sheep meat of different geographical origins and multivariate statistical analysis to construct a discriminant model for the identification of the geographic origin of mutton. Inductively coupled plasma-mass spectrometry was used to determine the contents of 25 mineral elements in the Longissimus dorsi muscle of Tan sheep from Yanchi county of Ningxia, Etuokeqian banner of Inner Mongolia autonomous region, Dingbian county of Shanxi province and Huanxian county of Gansu province. Analysis of variance, principal component analysis and linear discriminant analysis were carried out to develop and validate the discriminant model. The results showed that the contents of 17 of the 25 mineral elements in mutton were significantly different among growing regions. The principal component 1 was mainly composed of six elements: Cr, Mn, Ni, Cu, Se and Rb, with the highest discriminant contribution rate of 26.403%; the principal component 2 was mainly composed of four elements of K, P, Fe and Sn, with contribution rate of 22.285%. Through the stepwise discriminant analysis, Ca, P, Cr, Mn, Ni, Cu, Se, Rb, Mo and Sn were selected for modeling. The overall correct discrimination rate for the geographical origins of mutton was 100%, suggesting the model could accurately distinguish Tan sheep meat from different producing areas. Therefore, discrimination based on mineral element fingerprints can effectively identify Tan sheep meat from different producing areas.
Discriminations of the Geographical Origin of Peach Based on Stable Isotope and Rare Earth Element Fingerprint Characteristics
LI An, CHEN Qiusheng, ZHAO Jie, PAN Ligang, ZHANG Qiang, JIN Xinxin, ZHANG Shaojun, QIAN Xun
2020, 41(6):  322-328.  doi:10.7506/spkx1002-6630-20190414-183
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A method for geographical origin discrimination of peach was established to provide technical support for the protection of geographical indication products and for tracing the geographical origin of agricultural products. Ninety-two samples of common peach cultivars were collected from four producing areas: the counties of Shunping, Laoting and Yongqing in Hebei Province and Pinggu district, Beijing in this study. The stable carbon, nitrogen, hydrogen and oxygen isotope ratios in peach were determined by elemental analysis-isotope ratio mass spectrometry. Inductively coupled plasma mass spectrometry was used to determine the contents of 16 rare earth elements. Multiple comparative analysis and general discriminant analysis were performed to establish a discriminant model for identifying the geographical origin of peach. Multiple comparative analysis showed that there were significant differences in nitrogen isotopes between Pinggu grown peach and those from other producing areas (P < 0.05); significant differences were found in carbon and oxygen isotope ratios between peaches grown in hilly regions (Pinggu and Shunping) and those grown in plain regions (Laoting and Yongqing) (P < 0.05), and the contents of the rare earth elements Ce, Eu, Gd and Er showed the most significant difference among different producing places (P < 0.05). According to the results of multiple comparative analysis, four stable isotopes (δ13C, δ15N, δ2H and δ18O) and eight rare earth elements (Y, Ce, Eu, Sm, Pr, Nd, Gd and Er) were selected for general discriminant analysis. Three discriminant functions with significant correlations were determined (P < 0.05). The overall correct discrimination rates for original peach samples from different geographical origins in back substitution and cross-validation test were 97.8% and 95.7%, respectively. Conclusively, stable isotope and rare earth element fingerprint analysis combined with chemometrics is feasible to identify the geographical origin of peach in small spatial scale.