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25 November 2018, Volume 39 Issue 22
Food Chemistry
Enzymatic Oxidation Products of EGCG and EC and Their Formation Routes
SHI Liting, JIANG Heyuan, ZHANG Jianyong, WANG Weiwei, SU Wei
2018, 39(22):  1-7.  doi:10.7506/spkx1002-6630-201822001
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The aim of this study was to explore several major oxidation pathways of epigallocatechin gallate (EGCG) and the competition mechanism between the disproportionation pathway and the benzene pathway. Dehydrotheasinensin A (DTSA) and theaflavin-3-gallate (TF) were obtained by enzymatic oxidation of mixtures of different proportions of EGCG and epicatechin (EC). The results showed that several products including DTSA and GA were formed from the hydrolysis of EGCG by polyphenol oxidase (POD), while theaflavin-3-gallate (TF-3-G) was formed and the consumption rate of EGCG was increased by 3.86%–4.95% when epicatechin (EC) was added to the reaction solution. The formation rate of DTSA was not significantly changed during the early reaction stage but it was lower in EGCG + EC systems than in the single system during the later stage with a maximum difference of up to 10.84%. The formation of TF-3-G was significantly higher (up to 11.16%) at 5 mmol/L EC than at 2.5 mmol/L EC concentration. The enzymatic oxidation process of EGCG + EC could be divided into four stages: initial stage, dimer formation, change of the main pathways and dimer consumption. At the initial stage, the disproportionation and the benzene pathways were both dominant and their proportions were higher than 85%. At the second stage, the proportion of the benzene pathway was increased with the addition of EC while the proportion of EGCG transformed into DTSA was significantly reduced and the disproportionation pathway was weakened. As the reaction processed, a number of oxidation polymerization pathways gradually appeared in the system and the proportions of other substances were increased. At the third stage, DTSA began to be consumed and TF-3-G was slowly increased. The disproportionation pathway was dominant during the whole process of EGCG enzymatic oxidation.
Foaming Properties and Foam Micromorphology of Rice Bran Protein
ZHANG Manjun, LI Xiaomin, ZHANG Yanpeng, QI Yutang, ZHANG Weinong, XU Wei
2018, 39(22):  8-14.  doi:10.7506/spkx1002-6630-201822002
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The effects of pH value and NaCl concentration on foaming properties and foam micromorphology of rice bran protein (RBP) were investigated. The relationships between bubble characteristics and foaming properties were established. The results indicated that although the foaming capacity of RBP solution without NaCl at pH 4 was poor, the form stability was up to (88.3 ± 7.3)%. At pH 10 and 12, the foaming capacity was significantly increased to (73.3 ± 0)% and (168.9 ± 10.2)%, respectively, and the foam stability was (74.7 ± 2.5)% and (68.5 ± 2.1)%. Moreover, the foaming capacity was increased to (77.8 ± 3.8)% and (90.0 ± 5.8)% at pH 4 and 7 respectively upon the addition of 1% NaCl. The micromorphology of RBM foams indicated that initial bubble size distribution was related to foam stability at all pH levels. Changes in the foaming capacity and foam stability caused by added NaCl were related to both bubble number and average bubble area.
Interaction between Disodium Succinate and Monosodium Glutamate and Their Hedonic Liking
WANG Jing, LI Bei, WANG Wenli, ZHANG Danni, LIU Yuan
2018, 39(22):  15-19.  doi:10.7506/spkx1002-6630-201822003
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Monosodium glutamate (MSG), a representative umami substance, is widely used to enhance overall food flavor and palatability in the food industry. Disodium succinate (or WSA for short) is also a widely used flavor enhancer due to its unique umami taste. Although WSA has been applied in many commercial products, its interaction with MSG and their hedonic liking have not been reported yet. A total of 12 panelists were trained for sensory evaluation in this study. Paired comparison test and the nine-point hedonic scale were used to determine the relative umami concentration and to assess the hedonic liking of 5 mixed solutions containing 0.300 g/100 mL MSG and 0.010, 0.020, 0.030, 0.050 and 0.100 g/100 mL WSA, respectively. The results showed that umami taste significantly increased with increasing WSA concentration up to a MSG/WSA ratio of 6:1 and then decreased. Hedonic liking slightly rose with increasing WSA concentration up to a MSG/WSA ratio of 15:1 and then dropped dramatically. Hence, the optimum MSG/WSA ratio does not exceed 10:1 based on the results above. The interaction between MSG and WSA found in this study can provide a theoretical basis for the application of WSA.
Analysis of Bioactive Substance Contents and Antioxidant Activities in Rosa roxburghii Fruits during Development
ZHOU Guangzhi, LU Min, AN Huaming
2018, 39(22):  20-25.  doi:10.7506/spkx1002-6630-201822004
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This study aimed to understand the changes in the contents of bioactive substances and their contributions to the antioxidant properties in the fruits of Rosa roxburghii (Guinong 5 cultivar). The contents of total phenolics, total flavonoids, total triterpenes and vitamin C and superoxide dismutase (SOD) at different developmental stages were determined. The antioxidant activity in vitro was evaluated by measuring scavenging capacities against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2’-amino-di(2-ethyl-benzothiazoline sulphonic acid-6)ammonium salt (ABTS) radicals and ferric reducing antioxidant power (FRAP). We also investigated the correlation between the bioactive substance contents and antioxidant activity. The results showed that different bioactive substances in the fruits of Rosa roxburghii changed differently with developmental stage. The VC content increased to reach the maximum at 100 d after anthesis. The contents of total phenolics, total flavonoids and total triterpenes consistently decreased firstly and then increased; higher levels were observed in the young (20–40 d after anthesis) and ripe fruits. However, higher SOD activity was recorded at 40–60 d after anthesis. Overall, three antioxidant properties changed consistently with total phenolic content, showing a significantly positive correlation (P < 0.01). Principal component analysis (PCA) showed the contribution of five bioactive substances to antioxidant capacity was in the decreasing order of total phenolics, total flavonoids > VC > total triterpenes > SOD, and the cumulative contribution rate of the first three substances to the total variance was over 80%. All of the above results showed that the antioxidant capacity of the fruit was ascribed to the synergistic effects of several bioactive substances, and the total phenolics, total flavonoids and ascorbate played a decisive role.
Effect of Flaxseed Gum on the Gelling Forces and Emulsifying Properties of Myofibrillar Protein at Different NaCl Concentrations
FENG Meiqin, LIU Wenyan, SUN Jian, XU Xinglian, ZHOU Guanghong
2018, 39(22):  26-31.  doi:10.7506/spkx1002-6630-201822005
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To improve the gelling and emulsifying properties of low-salt meat products, this study determined the effect of flaxseed gum (FG) on the stability of emulsions containing myofibrillar protein (MP) and the chemical forces involved in MP gelation. The emulsion stability was evaluated by measuring creaming index, zeta potential value, particle size and microscopic observation. Results showed that the formation of MP gel and FG-MP gel system was attributed to disulfide bonds and non-disulfide covalent bonds. The effects of different NaCl concentrations on creaming index, potential value, and particle size of FG-MP emulsion were not statistically significant (P > 0.05). Creaming index, zeta potential value, and particle size varied significantly with increasing NaCl concentration (P < 0.05). In particular, the addition of flaxseed gum could significantly improve the stability of MP stabilized emulsions at low salinity levels (P < 0.05). Microscopic observation revealed that the addition of FG could reduce the aggregation of MP emulsion droplets. Thus, under low salt conditions, flaxseed gum could significantly improve the stability and salt tolerance of MP stabilized emulsions, which could promote the application of flaxseed gum in meat products.
Effect of Starter Culture Mixture of Staphylococcus xylosus and S. carnosus on the Quality of Dry-Cured Meat
ZHOU Huimin, ZHANG Shunliang, ZHAO Bing, LI Su, PAN Xiaoqian, REN Shuang, QU Chao, CHENG Xiaoyu
2018, 39(22):  32-38.  doi:10.7506/spkx1002-6630-201822006
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The effect of a starter culture mixture of Staphylococcus xylosus and S. carnosus on the quality of dry-cured meat was studied by physicochemical and microbial analysis, sensory evaluation, aroma composition analysis and electronic nose evaluation. Dry-cured meat produced without starter culture served as a blank control. The results showed that the effect of the starter culture on the quality of products was significant. Compared with the blank group, the starter culture significantly increased acid value (from 2.12 to 3.28 mg/g), protein degradation index (from 16.32% to 19.24%), a* value (from 9.25 to 11.08), sensory scores for aroma and acceptance, and the types and amounts of aroma active compounds derived from amino acid metabolism (3-methylbutyraldehyde and 3-methylbutanoic acid). Furthermore, it reduced peroxide value (POV) (from 0.15 to 0.07 g/100 g lipid), thiobarbituric acidreactive substance (TBARS) value (from 0.25 to 0.17 mg/kg) and the contents of aroma active compounds derived from lipid oxidation (hexanal and nonylaldehyde). However, some physicochemical indexes (water content, aw, and pH) were not significantly affected. The electronic nose could distinguish between the two groups, which illustrated that the flavor was changed after adding the starter culture. Therefore, the starter culture mixture of S. xylosus and S. carnosus could significantly promote proteolysis and lipolysis, improve color, promote fermented flavor development, and delay lipid oxidation in dry-cured meat.
Effect of Heat Treatment on Solubility and Secondary Structure of Soybean 11S Glycinin
QI Baokun, ZHAO Chengbin, LI Yang, XU Liang, DING Jian, WANG Huan, JIANG Lianzhou
2018, 39(22):  39-44.  doi:10.7506/spkx1002-6630-201822007
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The thermal properties, solubility and secondary structure of soybean 11S glycinin were measured by using differential scanning calorimetry, the Lowry method and Fourier transform infrared (FTIR) spectroscopy, respectively. The effects of heat treatment on the solubility and secondary structure of 11S glycinin were evaluated. The results obtained showed that Td and ΔH were reduced by heat treatment, leading to partial or complete denaturation of protein. Heat treatment at 80 ℃ could reduce the solubility of soybean 11S globulin, which may be due to the changes in the spatial structure and surface charge of protein caused by heat treatment. At the same time, the α-helix structure of protein was gradually transformed into β-sheet and random coil structure. However, the solubility of protein was slightly increased after heating for a certain time at 90 or 100 ℃, which was ascribed to the formation of soluble aggregates. Furthermore, the α-helix and β-sheet structures of protein were transformed into β-turn and random coil structure, indicating that the β-turn and random coil structures play an important role in the formation of heat-induced aggregates. In addition, protein denaturation and rupture of hydrogen bond were important causes for mutual transformation of the secondary structures.
Anthocyanin Composition and Antioxidant Activity of Cranberry
WAN Meizhi, MENG Xianjun
2018, 39(22):  45-50.  doi:10.7506/spkx1002-6630-201822008
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In this paper, the anthocyanin composition and antioxidant activity of cranberry were evaluated. By pH differential method, the amounts of anthocyanins extracted by ultra high pressure-assisted extraction and conventional solvent extraction were determined to be (75.49 ± 0.43) and (67.31 ± 1.08) mg/100 g, respectively. The anthocyanin content of cranberry was (79.52 ± 0.50) mg/100 g. AB-8 macroporous resin was used to purify anthocyanins from the crude extract of cranberry. After purification, the content of anthocyanins in the freeze-dried powder increased from (46.10 ± 0.92) to (309.26 ± 2.37) mg/g. The scavenging capacity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2’-azinobis(3-ethylbenzothiazoline-6-sulphonate) (ABTS+·) free radical and total antioxidant capacity of the purified anthocyanins were determined. The results indicated that the antioxidant capacity of cranberry anthocyanins was stronger than that of vitamin C at the same concentrations. Seven anthocyanins were identified by HPLC-MS, namely peonidin-3,5-dihexoside, cyanidin-3-galactoside, cyanidin-3-glucoside, cyanidin-3-arabinoside, peonidin-3-galactoside, peonidin-3-glucoside and peonidin-3-arabinoside. Peonidin-3,5-dihexoside was identified in cranberry for the first time to our knowledge.
Characterization of Salt-Soluble Protein from Mytilus edulis and Enzymatic Preparation of ACE Inhibitory Peptides
QIAO Meiling, LIU Hanxiong, FAN Fengjiao, TU Maolin, YU Cuiping, DU Ming
2018, 39(22):  51-56.  doi:10.7506/spkx1002-6630-201822009
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The molecular mass distribution, particle size distribution and degeneration temperature of the salt-soluble protein from Mytilus edulis muscle were studied. The tryptic hydrolysate of M. edulis muscle was found to have higher angiotensin converting enzyme (ACE) inhibitory activity than the hydrolysates produced with neutral protease and pancreatin, with a half maximal inhibitory concentration (IC50) of 215.96 μg/mL. The amino acid sequences of peptides from the tryptic hydrolysate were identified by mass spectrometry. Eleven peptides bound to ACE with scores greater than 180 were selected. The interaction and hydrogen bonds between amino acid binding sites were analyzed to screen active peptides and the mechanism of antihypertensive activity was elucidated. Finally, LYDIDVAK and WIAEEADK were predicted as peptides with high ACE inhibitory activity.
Chemical Quality Analysis and Evaluation of Donkey Hide Gelatin and Deer Skin Gelatin
ZHANG Lei, WANG Yanhua, LIU Chang, GONG Ruize, LI Shanshan, SUN Yinshi
2018, 39(22):  57-63.  doi:10.7506/spkx1002-6630-201822010
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The contents of heavy metals, amino acids, nucleosides and fatty acids in donkey hide gelatin and deer skin gelatin were measured by inductively coupled plasma mass spectrometry (ICP-MS), automatic amino acid analyzer, ultra performance liquid chromatography (UPLC) and gas chromatography (GC), separately. Results showed that the contents of Pb (1.00 mg/kg) and Cu (0.80 mg/kg) were much higher than those of other heavy metals (< 0.1 mg/kg). The contents of total amino acids in the two gelatins were 85.66% and 90.02%, where the proportions of essential amino acids were 16.14% and 15.89%, respectively. Glutamic acid, glycine, alamine and proline were the dominant amino acids. Twelve nucleosides were detected in donkey hide gelatin with the dominance of xanthine (35.46 μg/g), while 9 nucleosides in deer skin gelatin, xanthine being the major one (70.44 μg/g). The major fatty acids found in both gelatins were palmitic acid, palmitoleic acid, oleic acid, and linoleic acid; saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) were more abundant in deer skin gelatin than in donkey hide gelatin. On the other hand, the contents of polyunsaturated fatty acids (PUFA), essential fatty acids (EFA) and n-6 unsaturated fatty acids were higher in donkey hide gelatin. The ratios of SFA/MUFA/PUFA in both gelatins were close to the healthy ratio.
Effect of Different Waxy Corn Starch on Gel Properties of Myofibrillar Protein
LIU Jingxue, LI Fenglin, ZHANG Chuanjun
2018, 39(22):  64-70.  doi:10.7506/spkx1002-6630-201822011
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Waxy corn starch, esterified waxy corn starch and cross-linked esterified waxy corn starch were added separately to myofibrillar proteins at levels of 0%, 2%, 4%, 6%, 8% and 10% to form protein-starch composites for the purpose of investigating the effects of three starches on the water retention, texture properties, whiteness, surface hydrophobicity, rheology and microstructure of myofibrillar protein (MP) gels. The experimental results showed that addition of starch could significantly improve the water holding capacity, hardness and elasticity of MP gels in a concentration-dependent manner (P < 0.05). These indexes were increased but not significantly at an addition level of 10% (P > 0.05). Cross-linked esterified corn starch was the most effective among the starches. All three starches could increase the whiteness of composite gels, but cross-linked esterified corn starch resulted in an excessively high whiteness value (P < 0.05), which is unfavorable to the color. Meanwhile, all the starches could significantly increase protein surface hydrophobicity and gel elastic modulus (P < 0.05). Compared with MP gels, the composite gel structure tended to be more compact and uniform. The effect of cross-linking esterified waxy corn starch on improving MP gel properties except for color was better than that of the other two starches.
Bioengineering
Optimized Preparation, Characterization and Identification of Antioxidative Peptide Derived from Chicken Blood Corpuscle Proteins by Enzymatic Hydrolysis
ZHENG Zhaojun, ZHANG Rijun
2018, 39(22):  71-79.  doi:10.7506/spkx1002-6630-201822012
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In order to explore the potential antioxidative properties of poultry blood, several proteases were screened for use in the production of antioxidative peptide from chicken red blood cells and the enzymatic hydrolysis process was optimized using response surface methodology. The hydrolysate was purified sequentially by ultrafiltration, cation exchange chromatography, gel filtration chromatography, and high-performance liquid chromatography. The antioxidative peptide obtained was identified by mass spectrometry. The results showed that the hydrolysate obtained using acidic protease had the highest scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical (> 80%) among 6 proteases used. The optimal hydrolysis conditions were obtained as follows: enzyme/substrate (E/S) ratio 2%, temperature 45 ℃ and time 3.0 h. The DPPH radical scavenging activity, superoxide ion-scavenging activity and reducing power of the hydrolysate obtained using the optimized conditions were (98.31 ± 0.66)%, (28.89 ± 0.31)% and (1.94 ± 0.03), respectively. After purification, the fraction with the highest antioxidative activity was obtained, whose DPPH radical-scavenging activity and reducing power were (87.16 ± 1.59)% and (0.21 ± 0.01) at 0.1 mg/mL, respectively. Finally, the peptide was identified by liquid chromatography-mass spectrometry (LC-MS/MS) as MGQKDSYVGDEAQSKRGILT with a molecular mass of 2 182.1 Da.
Effects of PDEs Gene Deletion in Saccharomyces cerevisiae on Antioxidant and Volatile Substances in Mopan Persimmon Wine
MA Lin, YAO Ting, REN Xiangfeng, TAN Taicong, ZHANG Liangran, WANG Yousheng
2018, 39(22):  80-86.  doi:10.7506/spkx1002-6630-201822013
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In this study, persimmon wine was produced with the wild type Saccharomyces cerevisiae and four mutant strains (PDE1/Dpde1, Dpde1/Dpde1, PDE2/Dpde2 and Dpde2/Dpde2). Changes in the physicochemical properties including soluble solids content (SSC), total sugar, alcohol content and pH, the contents of total phenols and flavonoids, and antioxidant properties including scavenging capacities against 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radical (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and total reducing power were detected during the fermentation process. The volatile components of five persimmon wines were analyzed and compared by headspace solid phase microextraction (SPME) coupled to gas chromatography-mass spectrometry (GC-MS). The results showed that the fermentation end point was reached at day 12, and the fermentation rates of the four mutants were faster than that of the wild-type strain, of which the Dpde2/Dpde2 strain had the fastest fermentation rate. The total flavonoids content and antioxidant ability of persimmon wines fermented with the four mutants were higher than those of the wine fermented with the wild-type strain. The wine produced with Dpde2/Dpde2 had the strongest antioxidant ability. No significant difference in volatile substances profiles was observed between the mutants and the wild-type strain, except that the relative content of esters in the persimmon wine fermented by PDE2/Dpde2 was higher than that of other persimmon wines.
Optimization of Culture Conditions for Poly γ-Glutamic Acid Production by Bacillus subtilis ZJS18
YU Ping, HUANG Xingxing, ZHANG Yishu
2018, 39(22):  87-92.  doi:10.7506/spkx1002-6630-201822014
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The culture conditions for poly γ-glutamic acid production by Bacillus subtilis ZJS18 were optimized by response surface methodology (RSM). Three factors that had a significant influence on the yield of poly γ-glutamic acid, namely sucrose, yeast powder and sodium glutamate, were screened out by the Plackett-Burman design. The levels of the three medium components were further optimized to be 64.40, 7.10 and 57.96 g/L, respectively using Box-Behnken design with RSM. The optimal culture conditions for the production of poly γ-glutamic acid were as follows: sucrose 64.40 g/L, yeast powder 7.10 g/L, sodium glutamate 57.96 g/L, NaCl 30 g/L, KH2PO4 2 g/L, MgSO4 0.3 g/L, initial pH 7.5, inoculum size 5%, medium volume 40 mL/250 mL, temperature 37 ℃, shaking speed 200 r/min, and fermentation time 36 h. Under the above conditions, the yield of poly γ-glutamic acid was up to 13.20 g/L, which was increased by 2.88 folds as compared to that under the original conditions.
Separation and Reutilization of Surfactant in Extractive Fermentation of Monascus Pigment
CHEN Gong, WU Zhenqiang
2018, 39(22):  93-100.  doi:10.7506/spkx1002-6630-201822015
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In this paper, pigment separation by trihalomethanes extraction combined with resin absorption (THMS-Resin) was investigated. The performance of the recovered Triton X-100 in the extractive fermentation was also studied. Results showed that the Monascus pigments and Triton X-100 could be well separated through the combined method. The recovery of Triton X-100 and yellow pigments with high antioxidant activity was 78% and 52%, respectively. The recycled Triton X-100 exhibited excellent performance for cell growth and pigment metabolism while maintaining the extraction performance. Meanwhile, the extractive fermentation with a proper mixture of the new and recycled Triton X-100 could significantly promote the synthesis of both intracellular and extracellular Monascus pigment, resulting in a 35% increase of the total pigment yield. Five cycles of extractive fermentation were conducted. In each cycle, the average recovery of Triton X-100 was about 80% with a good biocompatibility; cell growth was stable and the extraction efficiency and metabolism were high. The relative content of extracellular and intracellular yellow pigment was 1.0 and 0.6, respectively. This method showed potential applications in obtaining high yield of Monascus yellow pigments while promoting the reuse of Triton X-100.
Optimization of Fermentation Conditions for Plantaricin Production by Lactobacillus plantarum LPL-1 by Response Surface Methodology and Its Physicochemical Properties
WANG Yao, LI Qi, LI Pinglan
2018, 39(22):  101-109.  doi:10.7506/spkx1002-6630-201822016
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The present study aimed at improving plantaricin production by Lactobacillus plantarum LPL-1. Fermentation conditions were optimized by response surface methodology (RSM). The inhibitory activity (AU/mL) against Listeria monocytogenes 54002 was used as response variable. Using one-factor-at-a-time method and Plackett-Burman design, temperature, fermentation time and initial medium pH were identified as main factors that influence plantaricin production. The optimal fermentation conditions were determined as 31 ℃, 6.40, 32 h, 0.5% and 60% for temperature, initial medium pH, time, inoculum size and medium volume in flasks, respectively using path of steepest ascent and RSM with Box-Behnken design. The antibacterial activity of plantaricin produced under the optimized conditions was 674.29 AU/mL, which increased by 2.31 times compared with that before optimization. It was also found that the crude plantaricin extracted from the fermentation broth had obvious inhibitory effect on Gram-positive bacteria, and it was stable to heat (100 ℃, 30 min), acid-base conditions (pH 2–10) and sensitive to protease. Meanwhile, the disulfide bonds of bacteriocin were broken by disulfide bond denaturants, which proved the importance of disulfide bonds for bacteriocins. Conclusively, the present study provides insights into the potential use of bacteriocin as a food preservative in the food industry.
Isolation and Identification of Leuconostoc from Traditional Fermented Soybean Paste
ZHANG Ping, ZHANG Pengfei, LIU Siqi, YUE Yuanyuan, WU Rina
2018, 39(22):  110-115.  doi:10.7506/spkx1002-6630-201822017
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The objective of this study was to separate Leuconostoc from traditional fermented soybean paste and to analyze their prebiotic properties. A total of 56 samples of naturally fermented soybean paste were collected from six regions in northeast China. We separated the suspected strains from these samples using the spread plate method, identified their morphological characteristics, physiological and biochemical characteristics, and analyzed their 16S rRNA gene sequences. The acid and bile salt tolerance of Leuconostoc strains were compared. As a result, we obtained 118 strains of lactic acid bacteria suspected of being Leuconostoc. Six of these were confirmed as Leuconostoc, three of which were identified as Leuconostoc lactis while the remaining three were identified as Leuconostoc mesenteroides subsp. mesenteroides. Among these Leuconostoc strains, strain FX6 had the best prebiotic potential and its survival rate was 85.16% after 3 h incubation at pH 3.0 and was up to 96.07% after 6 h incubation with 0.3 g/100 mL bile salt. Therefore, strain FX6 can be used for further research and industrial applications. The mechanism of action of FX6 in the soybean paste fermentation process still needs to be elucidated further.
Construction of in situ UDPG Regeneration Strain for Biosynthesis of Rebaudioside D
FEI Liwen, WANG Yong
2018, 39(22):  116-122.  doi:10.7506/spkx1002-6630-201822018
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Sucrose synthase 3 from Arabidopsis thaliana (AtSUS3) was used to regenerate uridine diphosphate glucose, an activated glucose donor required in biotransformation of rebaudioside D (RD) from rebaudioside A (RA). The AtSUS3 gene was cloned from the cDNA of A. thaliana and assembled into plasmid pET28a to construct a expression plasmid pLW105. Co-transformation of pLW105 and plasmid pYF09 harboring UDP-glucosyltransferase EUGT11 gene into Escherichia coli (E. coli) BL21(DE3) generated the engineered strain pLW105+pYF09-BL21(DE3) co-expressing both enzymes. Using the whole cells of this strain as a biocatalyst, more than 80% of RA was conversed to RD without exogenous addition of UDPG, yielding about 930 mg/L RD. Then a plasmid harboring the genes encoding both enzymes was constructed and the resulting engineered strain E. coli BL21(DE3) showed the same biotransformation efficiency as the strains containing two plasmids. In order to decrease the amount of sucrose used in the bioconversion reaction, the cell lysate instead of the whole cells was used to catalyze the biotransformation of RD. Using the cell lysate of the engineered strain pLW108-BL21(DE3), about 93% RA was conversed to RD with a yield of about 1 051 mg/L at 5 g/100 mL sucrose concentration, which used only 1/8 of the amount of sucrose used in whole cell catalysis with a comparable RD yield.
Purification of an Antimicrobial Peptide from Bacillus pumilus HN-10 and Its Inhibitory Activity against Trichothecium roseum
YAN Haijiao, YUN Jianmin, BAI Jie, GUO Juan, DENG Zhanrui, LI Duojia
2018, 39(22):  123-128.  doi:10.7506/spkx1002-6630-201822019
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Chronic heavy use of bactericides could not only induce antibiotic resistance, but also could cause serious environmental and health risks. Thus, it is very important to develop new bactericides that kill pathogens without detectable resistance. In this study, a novel antimicrobial peptide produced by Bacillus pumilus HN-10 was purified consecutively by ammonium sulfate precipitation, macroporous resin AB-8 chromatography, Sephadex G-100 chromatography, and reversed-phase high performance liquid chromatography (RP-HPLC). The antimicrobial activity of the peptide was tested against Trichothecium roseum. The amino acid sequence was analyzed by matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS/MS). The results showed that this peptide was designated as P-1 and its amino acid sequence was G-G-S-G-G-G-S-S-G-G-S-I-G-G-R with a molecular mass of 1 149.14 Da. P-1 exhibited strong antimicrobial activity against T. roseum with a minimum inhibitory concentration of 1 μg/mL. Analysis with the ProtParam software indicated that the theoretical isoelectric point of P-1 was 9.75, with one positive charge. P-1 was proved to be a novel peptide by NCBI database and APD database search with the highest similarity of only 45%.
Effects of Selenium on Antioxidant Activity of Saccharomyces cerevisiae under Cadmium Stress
YANG Yukun, YANG Wenfei, CHANG Yuanyuan, GUO Yuanyuan, ZHAI Doudou, WANG Jin, WANG Xinghua
2018, 39(22):  129-134.  doi:10.7506/spkx1002-6630-201822020
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The aim of this paper was to examine the effects of selenium on the antioxidant activity of Saccharomyces cerevisiae under cadmium stress. The levels of reactive oxygen species (ROS) and malondialdehyde (MDA), and the activities of important antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and peroxidase (POD) in S. cerevisiae cells were determined. The results obtained showed that cadmium treatment could significantly increase the contents of ROS and MDA in S. cerevisiae (P < 0.01), consequently generating oxidative stress. When a certain amount of exogenous selenium was added to the culture system, the activities of SOD, POD, CAT and GSH-Px were significantly increased (P < 0.01). The content of antioxidant GSH was also increased, enhancing the ability to scavenge ROS and MDA. These results indicated that the addition of exogenous selenium could also antagonize cadmium effects in S. cerevisiae, and this effect was also observed in plants and animals. S. cerevisiae could be used as a model organism for further study to investigate the mechanisms of selenium antagonism towards cadmium toxicity.
Screening and Identification of Aroma-Producing Fungi from Tongcheng Dry-Cured Duck
YAO Xiuxiang, WANG Wu, LI Peijun, ZHOU Ying, TONG Honggan, ZHANG Huafeng, YE Jian
2018, 39(22):  135-140.  doi:10.7506/spkx1002-6630-201822021
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In this study, aroma-producing fungi were screened and isolated from Tongcheng dry-cured duck using Bengal Red and PDA media. As a result, an aroma-producing strain of yeast (Y1) and an aroma-producing strain of mold (M3) were selected by sensory evaluation. The volatile flavor compounds produced by the two fungi in a potato-glucose culture system and a model meat system were extracted by headspace solid-phase microextraction (SPME) and identified by gas chromatography-mass spectrometry (GC-MS). In comparison with the control group, 1-pentanol and phenylethyl alcohol from strain Y1 were generated as well as benzaldehyde and γ-decalactone from strain M3. Y1 was identified as Candida zeylanoides and M3 as Bjerkandera based on 26S rDNA gene sequence and internal transcribed spacer (ITS) region sequence, respectively.
Changes in Carbon Metabolism Characteristics and Community Composition of Endophytic Bacteria in Postharvest Kuqa-Grown Apricot
LIU Xiaojing, ZHU Jing, CHU Min, TANG Qiyong, GU Meiying, WANG Bo, ZHU Xuan, ZHANG Zhidong
2018, 39(22):  141-146.  doi:10.7506/spkx1002-6630-201822022
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This study aimed to analyze the succession of endophytic bacterial communities in postharvest Kuqa-grown apricot. The characteristics of carbon metabolism and the bacterial community composition were investigated by Biolog Eco method and high-throughput sequencing. The results showed that the metabolic activity of endophytic bacteria in Kuqa-grown apricot was obviously higher at the fully ripe stage than at the green ripe stage, and the major carbon sources utilized by the endophytic bacteria were significantly different between the two stages. The percentages of endophytic bacterial communities utilizing amino acids, carboxylic acids and polymeric substances were increased markedly. High-throughput sequencing results showed that 47 operational taxonomic units (OTUs) including 33 genera in 15 orders were obtained. The community structure of endophytic bacteria was different significantly in fully ripe and green ripe apricots. Flavobacteriales, Bacteroidales Clostridiales together accounted for up to 83% of the endophytic bacterial community. Meanwhile, Rhodospirillales, Enterobacteriales and Clostridiales were predominant in fully ripe apricot, accounting for up to 86% the total bacterial community. The percentages of Flavobacterium and Bacteroides were decreased whereas the percentages of Rhodospirillales and Enterobacteriales were increased; however, the percentage of Clostridiales did not significantly change with ripening of apricots. Furthermore, some pathogens that caused fruit soft rot and gastrointestinal disorders in humans were observed. This study can provide a scientific basis to further understand the spoilage mechanism of postharvest Kuche-grown apricot and develop storage and preservation technologies and for proper consumption.
Transcriptomic and Bioinformatic Analyses of Human Umbilical Vein Endothelial Cells Induced by Elaidic Acid
QIU Bin, SUN Wenjia, LIU Wei, XU Tongcheng, LIU Lina, ZONG Aizhen, JIA Min, DU Fangling
2018, 39(22):  147-152.  doi:10.7506/spkx1002-6630-201822023
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After being induced by elaidic acid, the differentially expressed genes in human umbilical vein endothelial cells were studied by transcriptional analysis and bioinformatics analysis at the transcriptional level. The results showed that a total of 95 genes were found to significantly changed, 31 of which were up-regulated while 64 were down-regulated. The bioinformatics analysis showed that a total of 772 genes were significantly differentially expressed during the biological evolution. There were 46 and 122 differentially expressed genes related to cell composition and molecular functions, respectively. A total of 93 signaling pathways were detected, of which 11 including terpenoid skeleton biosynthetic pathway, steroid biosynthetic pathway and fatty acid metabolic pathway were significantly changed. Based on the protein-protein interaction (PPI) and gene-gene interaction pathways, the target genes involved in different pathways including fatty acid synthase, STAT4 transcription factor and IL-23 cytokine were further analyzed.
Formulation Optimization of a Cryoprotectant for Freeze-Dried Candida oleophila and Its Application to Control Blue Mold in Apple
CAI Mengxuan, DENG Lili, YAO Shixiang, ZENG Kaifang
2018, 39(22):  153-158.  doi:10.7506/spkx1002-6630-201822024
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Candida oleophila is an efficient antagonist. Many studies have shown that it can control postharvest diseases in various fruits. However, because of difficulties in its transportation and storage, C. oleophila is difficult to apply commercially. Freeze-drying is widely used to preserve microorganisms. Thus, in the present research, the selection and optimization of cryoprotectant components (sugars and sugar alcohols including trehalose, sucrose, lactose and sorbitol; the antioxidant sodium glutamate; excipients including skim milk and β-cyclodextrin) as well as their levels for vacuum freeze-drying of C. oleophila were optimized using one-factor-at-a-time and orthogonal array design methods. The optimal formulation was composed of 15% trehalose, 2% sodium glutamate, and 10% skim milk powder. A survival rate of 69.7% was obtained using this formulation. The effects of fresh and freeze-dried C. oleophila on the incidence of blue mold and lesion diameter in apple were compared, and the growth dynamics of the yeast inoculated in apple wounds. Through this study, we hope to obtain a good biocontrol agent against blue mold in apple.
Preparation and Adsorption Performance of Immunoaffinity Column Based on Muscle Antibody from Bullfrog (Rana catesbeiana) for Detection of Citrinin
WANG Xiangyang, GU Shuang, YANG Ling
2018, 39(22):  159-165.  doi:10.7506/spkx1002-6630-201822025
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The citrinin binding capacity of muscle protein from bullfrog (Rana catesbeiana) immunized with citrinin-bovine serum albumin (BAS) conjugate emulsified with Freund’s complete adjuvant was investigated. The protein with high citrinin binding capacity was embedded into sodium alginate microspheres. The optimum conditions were determined as follows: immunogen dosage 6.4 mg, sodium alginate concentration 4 g/100 mL, CaCl2 concentration 5 g/100 mL, glutaraldehyde concentration 0.2%, and crosslinking time 2 h. Two milliliter of the crude citrinin extract from red rice was passed through a column packed with 2 g of sodium alginate microspheres followed by washing with 20 mL of ultra-pure water to remove the impurities, and good chromatogram was obtained without interfering peaks compared with commercial immunoaffinity column. The recovery of citrinin standard solution eluted with 5 mL of 70% acetonitrile and trifluoroacetic acid mixture was 86.7%. The column capacity was 0.101 μg/g. The content of citrinin in red rice was determined to be 0.037 and 0.043 μg/g using the column developed in this study and commercial immunoaffinity column, respectively. However, further study should be done to improve the preparation process for better product performance.
Comparison of Fungal Communities in Daqu with Different Treatments
XIA Yu, LUO Huibo, ZHOU Ping, HUANG Dan, DENG Bo, SHEN Caiping, WU Jiefeng
2018, 39(22):  166-172.  doi:10.7506/spkx1002-6630-201822026
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In order to explore the effect of hot air drying on the fungal communities in Daqu during storage, qPCR and high-throughput sequencing were used to analyze and compare the fungal community structures in Daqu with different treatments. The results showed that the number of 18S rRNA gene copies of fungi in all Daqu samples was between 1 × 1011 and 4.5 × 1011 copies/g, and the maximum number of copies of ZR3 was 4.5 × 1011 copies/g. Thermoascu spp., Rhizomucor spp., Aspergillus spp. and Candida spp. were the dominant fungi in all tested samples. Among these, Thermoascus spp. was the most predominant and it remained predominant during storage in Daqu storehouse. Compared with the storehouse environment, the laboratory storage environment was more conducive to the growth of Aspergillus spp.. Candida spp. grew better in dried Daqu. Besides, higher diversity indexes were observed in Daqu RG3 with hot air drying and subsequent laboratory storage for 2 months, as well as significant differences in the fungal communities, especially Wallemia spp., Byssochlamys spp., Penicillium spp. and Aspergillus spp.. Furthermore, principal component analysis (PCA) showed that the drop point of Daqu RG3 was relatively far away from other samples. Hence, it is worth further study to provide guidance for the industrial application of hot air drying on Daqu.
Bacterial Community Structure and Diversity in Unsterilized Shrimp Sauce
DAI Lingying, QI Manting, WANG Limei, QI Bin
2018, 39(22):  173-178.  doi:10.7506/spkx1002-6630-201822027
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This study aimed to fully understand the microbial diversity in shrimp sauce. The V3-V4 region of the bacterial 16S rDNA gene from shrimp sauce was sequenced by high-throughput sequencing, and the composition and diversity of the bacterial communities were analyzed. A total of 61 107 effective sequences and 4 358 operational taxonomic units (OTUs) were obtained. The result of diversity analysis showed that the semi-finished product had a high microbial community diversity. The analysis of bacterial composition indicated that Proteobacteria, Gammaproteobacteria, Vibrionales, Vibrionaceae and Photobacterium accounted for 92.02%, 90.58%, 85.91%, 85.91% and 71.94%, respectively. This research gives a better understanding of the microbial communities in shrimp sauce, which can provide a theoretical basis for ensuring the quality and safety, improving the quality and optimizing the production of shrimp sauce.
Effect of Probiotics on Antioxidant Activities of Cheddar Cheese during Ripening Period
CHEN Ping, LIU Lu, LI Xiaodong, QU Xiuwei, WANG Haixia, ZHANG Xiuxiu
2018, 39(22):  179-185.  doi:10.7506/spkx1002-6630-201822028
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Our study evaluated the acid and salt tolerance of 9 strains of probiotics to screen them for cheese production. We selected one strain with higher hydrolysis activity and another strain with higher antioxidant activity, and added them to cheddar cheese, respectively. Cheddar cheese without probiotics was used as the control. We studied the viability and antioxidant activity of all samples to determine the effect of various probiotics on antioxidant properties of cheese. The results showed that Lactobacillus helveticus 1.0612 possessed better hydrolysis activity while Lactobacillus rhamnosus 1.0911 possessed better antioxidant activity. During the ripening period, viable counts in the probiotic cheeses were significantly higher than those in the control (P < 0.05), but there was no significant difference between the probiotic cheeses (P > 0.05). For all three cheeses, antioxidant properties were increased first, then decreased, and finally leveled off. The scavenging capacities against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radicals reached the maximum at the 4th month while reducing power reached the maximum at the 5th month. The DPPH and hydroxyl radical scavenging capacity and reducing power (51.05%, 49.97% and 0.66) of the cheese with L. helveticus 1.0612 were significantly higher than those (47.30%, 46.19% and 0.56) of the cheese with L. rhamnosus 1.0911, respectively (P < 0.05). Therefore, we concluded that compared with the strain with good antioxidant activity, adding the strain with high hydrolysis activity to cheese can promote protein breakdown into antioxidant short-chain peptides and amino acids, consequently enhancing antioxidant activity in cheese.
Analysis of Fungal Diversity in Homemade Sourdough Starters Using High-Throughput Sequencing
LIU Jianli, SUN Min, CAO Xiaohong, ZHANG Xiu, LI Jingyu
2018, 39(22):  186-194.  doi:10.7506/spkx1002-6630-201822029
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Sourdough starter is a fermentation starter used in the processing of traditional flour food. Most of the previous studies concerning the microbiology of sourdough starter have focused on the isolation and culture of microorganisms. This paper aimed to reveal the characteristics of fungal community structure in traditional sourdough starters by high-throughput sequencing. To analyze the fungal communities in 18 samples collected from different provinces in China, internal transcribed spacer 1 (ITS1) regions were amplified with by PCR based on metagenomics and high-throughput sequenced with Illumina Miseq. Bioinformatics analysis was carried out on Cloud Service Platform. The results showed that a total of 101 operational taxonomic units (OTUs) were found in the 18 samples, which were assigned to 56 species in 38 genera in 25 families in 15 orders in 9 classes in 4 phyla. Saccharomyces cerevisiae was predominant in most samples. S. cerevisiae, Fungi sp. and unclassified_k__Fungi were found abundant in all samples. Kazachstania bulder, Torulaspora delbrueckii, Candida humili, Candida glabrata and Candida sake were also abundant, but they only existed in single samples. Wickerhamomyces anomalus, Alternaria sp. and Aspergillus penicillioides were not only abundant but also highly frequent in most samples. The fungal community structures in these samples were not significantly dissimilar, and no significant difference was observed between the different types and geographical origins.
Component Analysis
Effects of Ohmic Heating on the Volatile Compounds of Soymilk
SHAN Changsong, SONG Hualu, LIU Jin, JIA Chaoshuang, WU Peng, LI Fade
2018, 39(22):  195-201.  doi:10.7506/spkx1002-6630-201822030
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This study aimed to investigate the effect of Ohmic heating on the volatile compounds of soymilk. Headspace solid-phase micro-extraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) was employed to analyze the volatile compounds of samples. The extraction efficiencies of three types of SPME fibers (100 μm PDMS, 65 μm PDMS/DVB and 50/30 μm DVB/CAR/PDMS) were compared. The optimal conditions were determined for the analysis of volatiles in soymilk samples. To eliminate the influence of thermal effects, the Ohmic heating and the traditional heating process were kept as consistent as possible. The results showed that 65 μm PDMS/DVB fiber had a greater sensitivity to a more diverse range of volatile compounds in soymilk, followed by 50/30 μm DVB/CAR/PDMS and 100 μm PDMS fiber. A total of 35 volatile compounds were identified in soymilk, including 16 aldehydes, 5 alcohols, 10 heterocycles (hexanal, (E)-2-heptenal and 1-octene-3-alcohol), 3 ketones and 1 ester. These volatiles contributed to the characteristic flavor of soymilk. Different heating methods had no considerable effect on the types of volatile compounds but significantly affects the contents of the characteristic aroma compounds (P < 0.05). In comparison with the conventional heating group, the contents of hexanal, 1-octen-3-ol and (E)-2-octenal were decreased by 45.55%, 58.60%, and 25.56%, respectively, in the Ohmic heating group. (E)-2-heptenal and 1-hexanol, the major odor compounds of soymilk, were not detected in the Ohmic heating group. Thus, it was concluded that the contents of beany flavor compounds in soymilk could be reduced significantly by Ohmic heating. This research can provide a theoretical basis for the application of Ohmic heating in soymilk processing.
Effect of Ultra-High Pressure Treatment on Enzymatic Activities and Aroma Compounds in Hami Melon Juice
HOU Sihan, PEI Longying, CHEN Jiluan
2018, 39(22):  202-206.  doi:10.7506/spkx1002-6630-201822031
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In this study, we used principal component analysis (PCA) to analyze the correlation between the activities of six key enzymes involved in the pathway of fatty acid metabolism, lipoxidase (LOX), alcohol dehydrogenase (ADH), acyltransferase (AAT), hydroperoxide lyase (HPL), phospholipase A1 (PLA-1) and phospholipase A2 (PLA-2) and aroma compounds in Hami melon juice subjected to ultra-high pressure treatment. The results showed that there existed different correlations between the different enzymes and aroma compounds. The first and second principal components contributed to 75.56% and 21.83% (97.39% together) of the total variance, respectively. LOX and PLA-1 activities were found to be highly correlated with esters, aldehydes, ketones and alcohols based on the first principal component. A strong correlation between ADH, HPL, AAT and PLA-2 activities was found based on the second principal component.
Phenolic Compositions and Discrimination of Seven Vegetable Oils
BAI Yunhui, WEN Haichao, ZHANG Lei, NI Yuanying, LI Jingming
2018, 39(22):  207-212.  doi:10.7506/spkx1002-6630-201822032
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The phenolic compositions of sunflower oil, rapeseed oil, peanut oil, flaxseed oil, olive oil, corn oil and sesame oil were determined by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Principal component analysis, linear discriminant analysis and cluster analysis were applied to discriminate these vegetable oils. Results showed that phenolic composition and contents greatly varied among these vegetable oils. In PCA analysis, four principal components were extracted, which accounted for 89.42% of the total variance explained. The PCA score plots showed a noticeable difference among the seven oils. The vegetable oils were apparently distinguished by linear discriminant analysis with an accuracy rate of 84.4%. Good discrimination of rapeseed oil, olive oil and rapeseed oil from other oils was achieved by hierarchical cluster analysis.
Nutritional and Functional Compositions and Nutritional Quality of Edible Petals of Various Lines of Hibiscus syriacus L.
YANG Shaozong, CHEN Jialong, LIU Xinhong, LIN Changli, CHENG Yaping, FANG Ru
2018, 39(22):  213-219.  doi:10.7506/spkx1002-6630-201822033
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In order to study the food value of the flowers of Hibiscus syriacus L. to humans, the nutritional and functional components of the flesh petals of five lines of H. syriacus, H. syriacus?f. elegantissimus, H. syriacus?f. violaceu and H. syriacus f. albus-plenus, cultivated in Longquan, Zhejiang; and H. syriacus f. albus-plenus and H. syriacus?f. violaceu cultivated in Cangnan, Zhejiang, were analyzed. The results showed that the nutritional quality of H. syriacus. was lower than that of edible rose. The contents of general nutrients and mineral elements were consistent with or slightly higher in H. syriacus than in green vegetables, while the vitamin content was lower. There were 16 amino acids detected in H. isyriacus L., including 7 essential amino acids (EAA), with flavor amino acids accounting for 27.1%-41.84% of the total amino acids, which was higher than that of edible rose. The petals of H. isyriacus L. contained such health-protective components as polysaccharides, flavanoids and proanthocyanidins. The flowers of H. syriacus tasted good and had high nutritional value. Principal component analysis (PCA) showed that there existed significant difference in nutritional value among five lines of H. syriacus L. and the nutritional value of H. syriacus?f. violaceu from both areas was the highest. Consequently, H. syriacus f. violaceus has the potential to be developed into a functional food.
Processing Technology
Preparation of Soybean Milk Powder with Higher Isoflavone Aglycone Content by Germination-Low Temperature Pulping
JIANG Lianzhou, XUN Chongrong, WU Changling, Просеков Александр ЮРЬЕВИЧ, FAN Zhijun, LI Yang, XU Zhenguo, WANG Zhongjiang
2018, 39(22):  220-226.  doi:10.7506/spkx1002-6630-201822034
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In this study, the traditional wet process for preparing soybean milk powder was improved by blanching and subsequent low-temperature pulping of germinated soybean in order to increase the isoflavone aglycone content in soybean milk powder. The new process was optimized by one-factor-at-a-time method and response surface methodology. Germination at 25 ℃ for 75 h and pulping at 57 ℃ for 3.5 h after pH adjustment to 6.0 were found to be the optimal conditions to obtain a higher content of isoflavone aglycone of 6.43 mg/g. The types and amounts of isoflavones in soybean milk powder was determined by high performance liquid chromatography (HPLC). Our data showed that the total isoflavone content and the isoflavone aglycone content were significantly increased (by 2.09 and 10.37 times) using the improved process compared with the traditional one.
Optimization of UV Sterilization Process of Strawberry Fresh Juice by Response Surface Methodology
HU Shunshuang, GAO Haiyan, WU Weijie, CHEN Hangjun
2018, 39(22):  227-234.  doi:10.7506/spkx1002-6630-201822035
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In this study, fresh strawberry juice was sterilized by UV radiation. The effects of fruit juice thickness, irradiation distance and time on sterilization efficiency were investigated. The optimal process parameters were obtained by response surface methodology as follows: juice thickness 0.7 mm, irradiation distance 8.0 cm and irradiation time 62 min. Under these conditions, the sterilization efficiency was 99.24%. In comparison with pasteurization, the contents of total phenolics and total anthocyanins were increased by UV irradiation while maintaining titratable acidity. However, UV irradiation had no significant influence on soluble solid content. Additionally, VC content was decreased by UV irradiation, while compared with pasteurization, the loss rate of VC was reduced by 28.7%. These results indicate that UV irradiation can meet the requirements for commercial sterilization of strawberry juice while maintaining its quality.
Extraction and Antifatigue Effect of Polyphenols from the Fruits of Acanthopanax sessiliflorus (Rupr. et Maxim.) Seem
XIAO Fengyan, GAO Lei, ZHAO Zijian, LUAN Chang, DUAN Cuicui, ZHAO Yujuan, LI Shengyu
2018, 39(22):  235-240.  doi:10.7506/spkx1002-6630-201822036
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Objective: To study the extraction and antifatigue effect of polyphenols from the fruits of Acanthopanax sessiliflorus (Rupr. et Maxim.) Seem. Methods: The effects of number of extraction cycles, extraction time and liquid to solid ratio on the extraction yield of polyphenols were investigated by orthogonal array design. The antifatigue effect was tested using a mouse weight-loaded swimming model. Results: Extraction time was found to be the factor with the greatest influence on the extraction yield of polyphenols followed by liquid to solid ratio and number of extraction cycles. The optimum extraction conditions were found as follows: liquid to solid ratio 20:1 (mL/g), extraction time 60 min, and two extraction cycles. The extraction yield of polyphenols under these conditions was 1.426%. The in vivo results showed that the extracted polyphenols could significantly prolong the exhausting swimming time, increase the levels of liver glycogen and muscle glycogen, enhance glutathione peroxidase activity, and reduced the levels of lactic acid and creatine kinase activity. Conclusion: Polyphenols from the fruits of A. sessiliflorus showed an antifatigue effect in mice.
Safety Detection
1H NMR Spectroscopy Combined with Chemometrics for the Rapid Detection of Adulterated Camellia Oil (Camellia oleifera Abel.)
SHI Ting, CHEN Qian, YAN Xiaoli, ZHU Mengting, CHEN Yi, XIE Mingyong
2018, 39(22):  241-248.  doi:10.7506/spkx1002-6630-201822037
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In an effort to develop a new method for the rapid detection of camellia oil adulteration, pure camellia oil and adulterated camellia oil with soybean oil or corn oil were tested by proton nuclear magnetic resonance (1H NMR) spectroscopy, and then the obtained spectral data were analyzed by chemometric methods. The experimental results showed that pure and adulterated camellia oil could be clearly distinguished by principal component analysis (PCA). Moreover, the adulterated samples display regular distribution depending on the adulteration ratio. However, only a few samples at lower adulteration ratios were overlapped with pure camellia oil. The difference could be revealed by partial least squares discriminant analysis (PLS-DA) with 100% identification accuracy for pure camellia oil. Partial least squares (PLS) was further applied for the prediction of the adulteration level in camellia oil. The proposed method allowed accurate and fast detection of camellia oil adulteration, and showed a great application potential in quality control and evaluation of camellia oil.
Establishment of Multiplex Real-Time PCR Assay to Detect Five Strains of Diarrheagenic Escherichia coli
HU Antuo, WANG Ping, ZHANG Caixia, CAI Yang, CHEN Ying
2018, 39(22):  249-255.  doi:10.7506/spkx1002-6630-201822038
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Objective: To develop a multiplex real-time PCR method for rapid detection and identification of five strains of diarrheagenic Escherichia coli. Methods: The multiplex real-time PCR method was established based on 11 virulence genes, including eae, stx1, stx2, ipaH, uidA, estla, estlb, aggR, pic, elt and astA. This method consisted of two reaction systems, A and B, which could be used to detect diarrheagenic enteropathogenic E. coli (EPEC), enterohemorrhagic E. coli (EHEC), enterotoxigenic E. coli (EIEC), enterotoxigenic E. coli (ETEC), and enteroaggregative E. coli (EAEC), respectively. The concentrations of probe and primers and PCR reaction conditions were optimized, and the sensitivity and specificity of the method were finally tested. Results: The primers and probes specifically amplified 11 gene fragments, and the sensitivities of systems A and B were 2.6 × 104 and 2.2 × 104 copies/reaction, respectively. Conclusion: The multiplex real-time PCR method established in this study can be used to determine whether one sample is diarrheagenic E. coli and which type of pathogen it belongs to by the simultaneous use of reactions A and B. This method can provide a basis for clinical detection, disease prevention and outbreak traceability of diarrheagenic E. coli.
Detection of the Binding Capacity between Peanut Protein and Serum IgE from Peanut Allergy Sufferers Using Biolayer Interferometry
ZHANG Ying, LI Kun, YAN Qi, CHEN Hongbing, WU Zhihua,
2018, 39(22):  256-262.  doi:10.7506/spkx1002-6630-201822039
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In the present study, an approach to detect the binding capacity between peanut protein and serum IgE from patients with peanut allergy was explored using biolayer interferometry (BLI). For this purpose, the experiment was designed using a streptavidin (SA) dip and read biosensor, biotin labeled goat anti-human IgE antibody, the serum pool of patients with peanut allergy and peanut proteins. The optimized conditions for sensor modification were as follows: immobilization of the 100-fold diluted IgE for 20 min before being bound to the 10-fold diluted serum overnight. After being washed to baseline online, peanut protein (1 mg/mL) was bound to the sensor for 3 600 s and then dissociated for 120 s. This method was applied to detect the IgE binding capacity of peanut protein subjected to different thermal treatments and compare with enzyme linked immunosorbent assay (ELISA). The results showed that this method could directly evaluate the IgE binding capacity of allergenic protein and had good consistency with the ELISA results with correlation coefficient of 0.91. After frying treatment, the IgE binding capacity of peanut protein increased but decreased after boiling and roasting treatments. Protein extracted from thermally processed peanuts without shells had a stronger IgE binding capacity than that from thermally processed peanuts with shells.
Migration of Polycyclic Aromatic Hydrocarbons during the Refining of Soybean Oil
LIU Yulan, WEN Yunqi, MA Yuxiang, SI Shengli, XU Lili, LIU Chunmei
2018, 39(22):  263-268.  doi:10.7506/spkx1002-6630-201822040
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The migration of polycyclic aromatic hydrocarbons (PAHs) during the refining of crude soybean oil was investigated so as to prevent and control the risk of the presence of PAHs in foods containing soybean oil. For this purpose, we determined the contents of PAHs in phosphoric acid, caustic soda, activated clay used for degumming, deacidification, decolorization and deodorization of crude soybean oil and the corresponding processed samples as well as those in byproducts such as oil residue, soap stock, waste clay and deodorizer distillate. The results showed that PAHs were found in all refining agents and the benzo[a]pyrene (BaP) contents in phosphoric acid, caustic soda and activated clay were 0.95, 1.84 and 0.71 μg/kg, respectively. The total contents of 4 EU priority PAHs (benzo[a]anthracene, chrysene, benzo[b]fluoranthene and BaP) were 2.81, 16.81 and 8.85 μg/kg, and the total contents of 16 USEPA priority PAHs were 26.18, 112.61 and 111.85 μg/kg in the three agents, respectively. The removal rates of BaP during degumming, deacidification and deodorization were 7.57%, 23.57% and 91.65%, respectively. The removal rates of 4 EU priority PAHs during degumming, deacidification, decolorization and deodorization were 15.93%, 10.41%, 19.31% and 50.91%, respectively, and the removal rates of 16 USEPA priority PAHs were 15.45%, 11.59%, 6.66% and 52.99%, respectively. The contents of BaP in oil residue, soap stock, waste clay and deodorizer distillate were 0.45, 0.90, 0.52 and 12.49 μg/kg, respectively. The contents of 4 EU priority PAHs in these by-products were 10.14, 7.39, 9.69 and 300.50 μg/kg, respectively. The contents of 16 USEPA priority PAHs were 261.60, 434.49, 156.29 and 2 775.15 μg/kg, respectively.
Degradation Dynamics and Residue Analysis of Prothioconazole and Its Metabolite Prothioconazole-Desthio in Wheat and Soil by QuEChERS-High Performance Liquid Chromatography-Tandem Mass Spectrometry
SUN Xing, YAN Xiaolong, YANG Bangbao, DING Yue, YU Xiangyang
2018, 39(22):  269-275.  doi:10.7506/spkx1002-6630-201822041
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The degradation dynamics and residues of prothioconazole and its metabolite prothioconazole-desthio from 40% prothioconazole + tebuconazole suspension concentrate (SC) in wheat and soil were investigated by QuEChERS-high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The limit of detection (LOD) for both prothioconazole and prothioconazole-desthio was 2 × 10-3 ng, and the limit of quantitation (LOQ) was 0.02 mg/kg. The recoveries of prothioconazole from spiked wheat grains and straw and soil were 87.3%–103.0%, 93.6%–100.3% and 85.0%–100.5%, respectively, and the recoveries of prothioconazole-desthio were 93.2%–109.9%, 92.7%–101.9% and 81.7%–95.6%, respectively. The degradation of prothioconazole and its metabolite in wheat straws was fitted to a first-order reaction kinetic model. The half-lives of degradation of prothioconazole in wheat straw from Jiangsu, Henan and Beijing were 4.4, 1.8 and 3.3 d, respectively. The half-lives of degradation of prothioconazole-desthio in wheat straw from Jiangsu, Henan and Beijing were 6.2, 2.9 and 6.0 d, respectively. The final residues of prothioconazole in wheat grains and straw and soil were < 0.02, < 0.02–0.225 and < 0.02–0.033 mg/kg, respectively. The final residues of prothioconazole-desthio were < 0.02, < 0.02–0.282 and < 0.02–0.049 mg/kg, respectively. The spray application of 40% prothioconazole + tebuconazole SC twice at a dose of 300 g a.i./hm2 gave a final residual prothioconazole concentration in wheat grains consistent with the national standard (GB 2763-2016); thus, it can be safely used.
Suggestions concerning Limit Standard for Listeria monocytogenes during Low-Temperature Emulsified Sausage Processing
JIANG Ronghua, SU Liang, REN Pengcheng, SUN Linjun, WANG Xiang, LIU Qing, DONG Qingli
2018, 39(22):  276-282.  doi:10.7506/spkx1002-6630-201822042
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The aim of this study was to optimize the risk management of Listeria monocytogenes during low-temperature emulsified sausage processing. The food safety objective (FSO) for low-temperature emulsified sausage was set by the prevalence-dose (PD) equivalence curve method based on the results of quantitative risk assessment completed by our group with or without cross-contamination of L. monocytogenes. Moreover, other food safety standards, including performance objective (PO), performance criterion (PC) and microbiological criteria (MC), were obtained based on their relationship with FSO. The operating characteristic (OC) curve was used to evaluate the performance of sampling plans and MC. The results showed that the FSO for low-temperature emulsified sausage with and without cross-contamination of L. monocytogenes was 0.36 (lg(CFU/g)) and ?4.58 (lg(CFU/g)), respectively. The food safety standard with cross-contamination of L. monocytogenes was stricter, labor saving and economical. However, the consumer risk was overestimated and the producer risk was underestimated in the food safety standard without integrating the cross-contamination of L. monocytogenes.
Determination of 15 Toxic Alkaloids in Food Samples by High Performance Liquid Chromatography-Tandem Mass Spectrometry
FAN Sufang, MA Junmei, LIU Zhuo, YU Jing, ZHAI Hongwen, LI Qiang, ZHANG Yan
2018, 39(22):  283-288.  doi:10.7506/spkx1002-6630-201822043
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In this paper, a high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was established for the determination of 15 toxic alkaloids in food samples. Extraction conditions, purification methods and instrumental parameters were optimized. Samples were extracted with 20% ethanol solution, and the supernatant was separated and analyzed after centrifugation. The external standard method was used for quantification. The limits of detection (LODs) of 15 alkaloids were in range of 4–20 μg/kg and the limits of quantification (LOQ) were in range of 10–80 μg/kg. The recoveries of the method were in range of 80.9%–119.8% at spiked levels of LOQ, 3 LOQ and 5 LOQ, with relative standard deviations (RSDs) lower than 10%, which met the analytical requirements. This method was found to be useful for rapid screening and quantitative analysis of 15 toxic alkaloids in plant-derived drinks, cereal products, fruits and vegetables.
Separation and Determination of Acrylamide in Potato Chips by Pressurized Capillary Electrochromatography
FENG Jun, XIAO Xiaoru, LI Lijun,, CHENG Hao, HUANG Wenyi, LI Yanqing, KONG Hongxing
2018, 39(22):  289-294.  doi:10.7506/spkx1002-6630-201822044
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An efficient pressurized capillary electrochromatography (pCEC) method was developed for the determination of acrylamide in potato chips. The separation was performed on a reversed-phase EP-100-20/45-3-C18 capillary column (total length 45 cm, effective length 20 cm, diameter 100 μm, ODS packing 3 μm). Moreover, the mobile phase composition, the concentration of phosphate buffer, separation voltage and other experimental conditions were investigated and optimized, respectively. The mobile phase was composed of a mixture of acetonitrile and 15 mmol/L NaH2PO4 (pH 4.7) (15:85, V/V) at a flow rate of 0.04 mL/min. Under the optimal conditions (separation voltage ?2 kV, and UV detection wavelength 202 nm), the analyte was well separated. The linear range was 2.0–32 μg/mL with a correlation coefficient of 0.999 4. The detection limit (LOD) of acrylamide was 0.30 μg/mL (RSN = 3). The average recoveries were 95.3%–108.1%, with a relative standard deviation (RSD) less than 1.48%. The method has been used for the determination of acrylamide in potato chips with good results.
High-Throughput Screening of Veterinary Drug Residues in Raw Milk by HPLC-TOF-MS/MS
TIAN Huaixiang, HE Yujie, ZHOU Xingxin, ZHENG Xiaoping, HE Yabin, YU Haiyan, CHEN Chen
2018, 39(22):  295-304.  doi:10.7506/spkx1002-6630-201822045
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In this study, a high performance liquid chromatography tandem time-of-flight mass spectrometry (HPLC-TOF-MS/MS) method was established for the high-throughput determination of 174 veterinary drug residues in raw milk. The target compounds were extracted with acetonitrile and purified by freezing. A Poroshell 120 EC-C18 column (3.0 mm × 150 mm, 2.7 μm) was used for the separation of the target compounds with a mobile phase consisting of 0.1% formic acid in water and methanol via gradient elution. The analytes were detected with an electrospray ionization source (EIS) in the positive ion mode. The results showed that the method had a good linearity (R2 > 0.990 0) and low limits of detection (LOD) (1–10 ng/g) for 114 pesticide compounds. The average recoveries for 99 of these ranged from 70% to 130% with relative standard deviation (RSD) from 1.03% to 9.65% at quality control concentration levels. The method was successfully applied in the screening of veterinary drug residues in raw milk with high efficiency and sensitivity.
Molecular Identification and Safety Evaluation of Penicillium citrinum YL-1 from Fish Sauce Based on Fungal Genomic Sequencing
SONG Jiajia, GU Wenyu, LIN Changhao, ZHANG Xiaoyong, GAN Zhonghong, XIE Li, GAO Xiangyang
2018, 39(22):  305-311.  doi:10.7506/spkx1002-6630-201822046
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Objective: In order to overcome the deficiency of the traditional method to toxin-producing fungi, the toxin biosynthetic pathways and related key genes in Penicillium citrinum YL-1 were investigated by genomics to evaluate the safety of P. citrinum YL-1 during fish sauce fermentation. Methods: The strain was identified by internal transcribed spacer (ITS) sequencing. Genome survey of strain YL-1 was performed using the Illumina Hiseq platform. The key synthetic pathways and genes involved in the synthesis of Penicillium toxin and aflatoxin, as well as mycotoxin metabolism in which strain YL-1 may be involved were analyzed. The metabolic pathways of non-ribosomal peptide synthetase (NRPS), polyketide synthase (PKS), PKS-NRPS, terpenoid and amino acids and related genes were analyzed by bioinformatics tools. The mycotoxin-producing ability of YL-1 was determined to evaluate whether there was a potential hazard of mycotoxin. Results: Strain YL-1 was identified as P. citrinum with a 99% similarity. The genome of P. citrinum YL-1 was 31.92 Mb in length with GC content of 46.27%. A total of 11 980 genes were predicted using Maker2 sequencing by homology analysis, including 5 417 eukaryotic genes and 4 946 prokaryotic genes annotated in eukaryote clusters of orthologous groups (KOG) and cluster of orthologous groups of proteins (COG) databases, respectively. Kyoto Encyclopaedia of Genes and Genomes (KEGG) analysis was used to assign 3 525 genes to 323 pathways. Five metabolic pathways related to the biosynthesis of mycotoxins were annotated in P. citrinum YL-1, including only one homologous gene (Afld) involved in the metabolic pathway of aflatoxin and five other related genes. However, no complete metabolic pathway was annotated. Conclusion: Despite the above findings, further studies should be done to evaluate the safety of P. citrinum YL-1 in fish sauce and other related products.
Determination of Amatoxins and Phallotoxins in Plasma and Urine by Ultra Performance Liquid Chromatography-tandem Mass Spectrometry
XIAO Shaozhen, LIN Feng, FU Wusheng, WEI Daozhi
2018, 39(22):  312-318.  doi:10.7506/spkx1002-6630-201822047
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An ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was successfully developed for the simultaneous determination of amatoxins (AMA) and phallotoxins in plasma and urine. Guinea pigs were orally administered with α-AMA, β-AMA, phallacidin (PCD) and phalloidin (PHD) at single doses of 1.0, 0.486, 0.079 and 0.120 mg/kg·bw respectively. Plasma and urine samples at different time points were collected and analyzed by the developed method to study the metabolism patterns of these toxins in laboratory animals. The results showed that the limits of detection (LODs) were 0.3 and 1.0 μg/L for urine and plasma, respectively. The average recoveries at three spiked levels of 2–100 μg/L varied from 76.8% to 109.0% with relative standard deviations (RSDs) of 1.30%–12.00% (n = 6). α-Amanitin and β-amanitin rapidly reached the maximum levels of 14.6 and 7.24 μg/L in plasma, respectively at 2 h after administration. At 24 h, the amanitins were near the LODs or were undetectable. However, the phallotoxins were below the LODs in plasma at all time points investigated. All four toxins were detected at concentrations of 45.9–1 905 μg/L in urine at 2 h after administration.
Preparation and Application of Molecularly Imprinted Electrochemical Sensor for Rapid Detection of Sulfadiazine Residues in Foods
ZHAO Lingyu, QIN Sinan, GAO Lin, GAO Wenhui
2018, 39(22):  319-327.  doi:10.7506/spkx1002-6630-201822048
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A molecularly imprinted electrochemical sensor for the detection of sulfadiazine was prepared using sulfadiazine as a template molecule and o-aminophenol as a functional monomer at an optimized ratio as determined by UV spectroscopy. The glassy carbon electrode was modified by drop casting method with carbonylated multi-walled carbon nanotubes and nano-gold sol. Poly (o-aminophenol) membrane was formed by electropolymerization in perchloric acid-sodium perchlorate solution (pH 5.5). In the experiment, an aqueous solution containing 0.5 mol/L KCl and 5 mmol/L K3[Fe(CN)6] was used for the characterization of the sensor. The response characteristics of the electrochemical sensor were evaluated by cyclic voltammetry and differential pulse voltammetry. The preparation conditions were optimized. The selective response of the sensor to the template molecule and its analogues was investigated. It was applied to the rapid detection of sulfadiazine residues in foods. The results showed that under the optimum conditions, good linearity was observed in the concentration range of 1.0 × 10-8–2.0 × 10-6 mol/L. The limit of detection (LOD) was 3.3 × 10-9 mol/L, and the average recoveries from spiked samples were between 83.50% and 97.80%, with relative standard deviations (RSDs) less than or equal to 4.0%. The sensor is very promising due to its low cost, easy and rapid operation, high sensitivity, strong interference resistance and good stability.
Spectral Characterization of Fluorescent Sensor Immobilized with Eggshell Membrane and Method Development for Melamine Detection
ZHANG Pei, LI Ying, WANG Zengli, WANG Shiping
2018, 39(22):  328-333.  doi:10.7506/spkx1002-6630-201822049
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This study aimed to develop a method for rapid and precise detection of melamine in milk products. Based on the phenomenon that the melamine can linearly increase the fluorescence intensity of fluorescein within a certain concentration range, we constructed an eggshell membrane biosensor with fluorescein immobilized on its surface to detect melamine. Fluorescein and glutaraldehyde concentration were optimized. The eggshell membrane sensor had a linear working range of 1–500 μg/L, and the limit of detection (LOD) for melamine was 0.47 μg/L. Compared to the methods used for the detection of melamine in aqueous solution, the eggshell membrane sensor was more specific and stable with higher selectivity and lower LOD. This sensor can be successfully applied to the detection of melamine in commercial milk products.