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Table of Content

25 May 2018, Volume 39 Issue 10
Food Chemistry
Distribution of β-Glucan and Phenolic Acids in Oat Bran (Avena nuda) from the Processing of Oat Rice and Oat Flour
CHEN Zhongwei, WANG Ling, NIU Rui, ZHAO Fangfang, SUN Jun, XU Bin
2018, 39(10):  1-6.  doi:10.7506/spkx1002-6630-201810001
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The proportion and microstructure of oat bran and endosperm were analyzed on several selected typical cultivars of naked oat (Avena nuda). At the same time, the distribution profiles of β-glucan and phenolic acids in oat bran (pericarp, and seed coat with aleurone layer), and endosperm was tested to establish a method for determining the processing suitability of oats rice and oat flour. Finally, the method was used to verify the suitability of the existing mainstream processing technologies for oat rice and oat flour. The results showed that for all the selected varieties, β-glucan was mainly enriched in the bran containing a value of 85.7 mg/g, which was about 4.5 times higher than that in endosperm. Moreover, the contents of p-coumaric acid and ferulic acid in oat bran were 0.099 and 1.00 mg/g, which were 24 and 48 times higher than those in endosperm, respectively. In addition, the contents of p-coumaric acid and ferulic acid in pericarp were 13 and 2.7 times higher than those in testa + aleurone layer, respectively. The average content of β-glucan in the second bran obtained from oat rice processing was 1.7%, which was far lower than that in oat bran, suggesting that grinding was suitable for oat processing. While the contents of β-glucan in the fourth and fifth brans obtained from oat flour processing were 6.73% and 7.80%, which were close to that in oat bran, suggesting the processing was excessive. In conclusion, by analyzing the contents of β-glucan and phenolic acids in the oat bran obtained by grinding, we can determine the processing degree of oat products, which will provide technical support for oat processing.
Quality Protection and Action Mechanism of Antifreeze Peptide on Frozen Potato Dough Subjected to Freeze-Thaw Cycles
LI Ling, CHEN Xu, WANG Shaoyun
2018, 39(10):  7-13.  doi:10.7506/spkx1002-6630-201810002
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The objective of the present study was to determine the effect of antifreeze peptides from tilapia scale (TSAPP) on the specific volume, fermentation properties, water loss rate, starch gelatinization degree, texture properties, water distribution and mobility of frozen potato dough during freeze-thaw cycles and to elucidate the underlying mechanism of action. The addition of 1% TSAPP could increase the specific volume, shorten the fermentation time, augmented the starch gelatinization degree and reduce the water loss rate. Texture analysis showed that the hardness, chewiness and gumminess of potato steamed bread containing 1% TSAPP were decreased respectively by 29.96%, 26.99%, and 28.30% as compared with those of the control group. Analysis by nuclear magnetic resonance (NMR) showed that TSAPP affected the water status in potato dough by increasing tightly bound water and decreasing semi-bound water. TSAPP could also inhibit water loss and increase the water holding capacity of potato dough. In conclusion, antifreeze peptides could be used as a cryoprotective agent in frozen potato dough products.
Preparation and Physicochemical Properties of Hesperidin-Chitooligosaccharide Complex
CAO Ruge, ZHAO Yali, ZHOU Zhongkai
2018, 39(10):  14-19.  doi:10.7506/spkx1002-6630-201810003
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In this study, a new complex of hesperidin and chitooligosaccharide (Hesp-COS) was prepared by spray drying method in order to improve the water solubility and utilization of hesperidin. The physical and chemical properties of the Hesp-COS complex were studied by scanning electron microscopy, Fourier transformation infrared spectroscopy, nuclear magnetic resonance and thermogravimetric analysis. The results showed that hesperidin and chitooligosaccharides were interacted to form a stable complex through non-covalent interactions such as hydrogen bonds or van der Waals force. The water solubility of this complex was improved significantly by as high as 3.8 folds, and its antioxidant capacity was also greatly enhanced as indicated by an increase in 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (94.38%) and 2,2’-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt scavenging activity (17.37%) compared with that (83.72% and 9.15%, respectively) of hesperidin.
Effects of Complexation with Anthocyanin on the Structural and Functional Properties of Denatured Soybean Protein
JIANG Lianzhou, CHEN Si, LI Yang, WU Changling, WANG Zhongjiang, ZHANG Qiaozhi, QI Baokun, SUI Xiaonan, CHEN Fusheng, XU Zhenguo
2018, 39(10):  20-27.  doi:10.7506/spkx1002-6630-201810004
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This paper is focused on the effect of interaction with anthocyanin on the structure and function of denatured soybean protein. Fluorescence spectroscopy was used to study the conformational changes of the complexes. The relationship between structural change and functional properties was analyzed through determination of solubility, emulsifying ability, emulsifying stability, particle size analysis and Zeta potential analysis. The results showed that the absolute value of Zeta potential as well as emulsifying activity and emulsion stability of denatured soybean protein increased significantly after complexation with anthocyanin at pH 7.4, whereas its solubility decreased. The fluorescence spectra showed that the fluorescence quenching of heat-treated soybean protein by anthocyanin was a static quenching process with the formation of binding sites close to 1. The three dimensional fluorescence spectra indicated that complexation with anthocyanin extended the protein polypeptide backbone and changed the protein structures.
Dissociation Effect of Different Treatments on N-Glycolylneuraminic Acid in Beef
LIANG Meilian, ZHU Qiujin, LIU Chunli, WANG Kun
2018, 39(10):  28-34.  doi:10.7506/spkx1002-6630-201810005
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In this study, the N-glycolylneuraminic acid (Neu5Gc) contents of red meat and processed meat products were determined. The effects of different deep-fat frying temperatures and different cooking times on Neu5Gc contents in beef and beef soup were studied respectively. In addition, different enzyme preparations were screened for their ability to dissociate Neu5Gc. The results showed that the highest content of Neu5Gc was (58.45 ± 0.98) μg/g in beef. Neu5Gc loss in deep-fat fried beef was increased with increasing frying temperature above 150 ℃. However, the Neu5Gc content of beef soup was increased with increasing cooking time. Additionally, this study found that inulinase could dissociate Neu5Gc and the optimum dissociation conditions for Neu5Gc standard were 30 min water bath incubation at 50 ℃ and an enzyme dosage of 0.8%. Under these conditions, the dissociation rate of Neu5Gc standard was (50.52 ± 0.88)%, while the dissociation rate of Neu5Gc in beef was only (7.29 ± 2.67)% due to the complex composition of beef. This study may provide scientific guidance for people’s daily diet and also provide a basis for further exploring effective methods to reduce Neu5Gc in red meat.
Preparation of Stable Conjugated Linoleic Acid Microspheres Using Whey Protein Isolate-Gum Arabic Complex
YAO Xiaolin, CHEN Yu, SHU Meng, ZHANG Kun, JIANG Fatang
2018, 39(10):  35-39.  doi:10.7506/spkx1002-6630-201810006
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In this paper, conjugated linoleic acid (CLA) microspheres stabilized with whey protein isolate (WPI)-gum arabic (GA) complex (WPI-GA ISCs) were prepared by the emulsification solvent evaporation method. The results showed that the solvent evaporation resulted in aggregation of WPI-GA complex and consequently shrinkage and collapse of the WPI-GA interface, contributing to the thicker layer. The emulsifying stability of WPI-GA ISCs was improved, thereby preventing particle aggregation and CLA leakage. When the concentration of WPI-GA ISCs was higher than 1%, the CLA microspheres had good physical stability and resolubility after freeze-drying with high efficiency of encapsulation and delivery in the gastrointestinal tract.
Physicochemical Properties and Structural Analysis of Bigeye Tuna Skin Gelatin
HAN Shuang, MA Liang, YANG Hui, HUANG Dandan, ZHANG Yuhao
2018, 39(10):  40-45.  doi:10.7506/spkx1002-6630-201810007
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In this experiment, physicochemical properties and structural characteristics, including gel strength, gelling and melting points, amino acid composition, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and spectral characteristics of gelatin from bigeye tuna skin were investigated. The gelatin exhibited lower gel strength (403 g) and gelling and melting points (21.5 ℃ and 28.8 ℃) when compared with those of porcine gelatin. The contents of proline and hydroxyproline in the gelatin were 19.09%, which were slightly lower than those in porcine skin gelatin. This can explain why gel strength and gelling and melting points of tuna skin gelatin were lower than those of porcine skin gelatin. The results of SDS-PAGE showed that the content of low molecular weight components in tuna skin gelatin was only 6.67%, which indicated that pretreatment and extraction did not destroy the integrity of subunits in gelatin. The ultraviolet and infrared spectra of tuna skin gelatin were similar to those of porcine skin gelatin, which further indicated that the product obtained in this experiment was high-quality gelatin.
Effects of Polyphenols from Kunlun Chrysanthemum (Coreopsis tinctoria) on the Oxidative Stability of Peanut Oil
BAI Yunhui, WANG Guoyi, WEN Haichao, ZHANG Lei, NI Yuanying, LI Jingming
2018, 39(10):  46-52.  doi:10.7506/spkx1002-6630-201810008
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The effect of polyphenols from Kunlun chrysanthemum (KCP) on the oxidative stability of peanut oil was evaluated by accelerated oxidation test. The results showed that there was no significant difference in antioxidant activity between 200 mg/kg butylated hydroxy toluene (BHT) and 700 mg/kg KCP (P > 0.05). KCP concentration dependently improved the oxidative stability of peanut oil. Furthermore, KCP showed significantly increased 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity and ferric ion reducing antioxidant power in peanut oil (P < 0.05) and significantly prevent linolenate from oxidative degradation (P > 0.05). These results indicated that Kunlun chrysanthemum polyphenols could be used as a natural antioxidant to prevent lipid oxidation in peanut oil.
Flavonoid Content and Antibacterial Activity of Xanthoceras sorbifolia Bunge Fruit Drop
YANG Xiaohui, SHI Guangbo, BAI Xiaobin, ZHAO Chenxuan, LI Bosheng
2018, 39(10):  53-58.  doi:10.7506/spkx1002-6630-201810009
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Objective: This study aimed to determine the total flavonoid content of Xanthoceras sorbifolia Bunge fruit drop, identify flavonoid monomers and evaluate the antibacterial activity of these flavonoids. Methods: The content of total flavonoids was determined spectrometrically, and color reaction and Fourier transform infrared spectroscopy and high performance liquid chromatography (HPLC) were used to analyze the flavonoid monomers. The antibacterial activity was evaluated against Bacillus subtilis and Escherichia coli and Staphylococcus aureus. Results: The content of total flavonoids was 18.4 mg/g. Rutin and 14 other unknown monomers were detected in the purified flavonoids. The content of rutin was 27 mg/g, which accounted for about 6% of the total flavonoids. The flavonoids from X. sorbifolia Bunge fruit drop had an inhibitory effect on B. subtilis and E. coli and S. aureus and the strongest inhibition was observed on E. coli. Conclusion: Flavonoids with strong antibacterial activity are abundant in X. sorbifolia Bunge fruit drop and rutin is an important monomer.
Acidic Catalysis and Antioxidant Activity of Sesamolin
LI Xiaodong, WANG Xuede, WANG Nannan, MA Yuxiang
2018, 39(10):  59-64.  doi:10.7506/spkx1002-6630-201810010
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Petroleum ether, methanol and ethanol were used to explore the effect of different solvents on the acid-catalyzed degradation of sesamolin. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay was used to evaluate the antioxidant ability of sesamolin as well as its degradation products. Phosphotungstic heteropoly acid (HPW) was used to catalyze the sesamolin in sesame oil with the aim of investigating the effect of this catalysis on the oxidative stability of cold pressed sesame oil. The results indicated that different products were generated from the catalytic reaction in three different solvents. Sesamol was produced in all three solvents, while semin and sesaminol were detected only in petroleum ether and two unknown substances were found in both methanol and ethanol. The DPPH radical scavenging capacity of sesamolin and sesamin was much weaker than that of sesamol, tertiary butylhydroquinone (TBHQ), butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT); however, the DPPH radical scavenging capacity of sesamolin was markedly increased after being catalyzed by HPW in petroleum ether, which would provide a theoretical basis for enhancing the oxidative stability of cold pressed sesame oil by catalysis of sesamolin with HPW. The content of sesamolin in cold pressed sesame oil was gradually decreased with increasing addition of HPW, whereas the contents of sesamol and sesaminol were increased. Meanwhile, the oxidation induction time (OIT) of sesame oil was increased, which suggested enhanced oxidative stability.
Effect of Arabinoxylan Extracted by Two Methods on Properties of Wheat Dough and Quality of Chinese Steamed Bread
CHEN Jie, TIAN Beibei
2018, 39(10):  65-70.  doi:10.7506/spkx1002-6630-201810011
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In the current study, water extraction and enzymatic degradation were used to prepare araboxylan (AX) from wheat starch waste water with the aim of evaluating the effects of these two AXs on farinograph property, rheological fermentation characteristics, gelatinization characteristics and water status of wheat dough. The effect of AX addition on the quality of Chinese steamed bread (CSB) was analyzed by scanning electron microscopy and texture profile analysis. The results obtained showed that the purity of the enzymatically produced AX was 86.81%, which was higher than that of the water extractable AX. Both AXs when added at an appropriate concentration could improve farinograph characteristics of wheat dough and the effect of the enzymatically produced AX was more pronounced. A marginal decrease in the degree of gelatinization was observed with the addition of AX. The addition of AX led to a significant decrease in the hardness and chewiness of CSB. Adding the enzymatically produced AX could maintain the integrity of the protein network structure of CSB after compression. But the water extractable AX had a negative impact on the protein network structure of CSB and a large amount of starch granules were exposed when the CSB added with this AX was compressed. The addition of the enzymatically produced AX increased the gas capacity of dough and resulted in more uniform size of gas bubbles in the crumb of CSB, while the water extractable AX destroyed the uniformity of gas bubbles. Xylan endonuclease could improve this negative effect. In summary, multifarious optimization purposes can be achieved by addition of high purity AX to wheat flour-based products.
Extraction of β-Glucan from Lentinus edodes and Its Effect on Starch Digestibility
CHEN Zhongqiu, FENG Tao, ZHUANG Haining, YANG Yan, ZHANG Jingsong
2018, 39(10):  71-77.  doi:10.7506/spkx1002-6630-201810012
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Lentinus edodes β-glucan (LEBG) was extracted from the fruiting bodies of Lentinus edodes. The average molecular weight of LEBG was measured to be 1.868 × 106 Da. Monosaccharide composition analysis showed that LEBG was composed of arabinose, xylose, mannose, glucose and galactose with a molar ratio of 0.72:1.61:2.61:92.75:2.34. Infrared (IR) spectroscopy showed that LEBG was a polysaccharide containing pyranose ring. Addition of LEBG to wheat starch and corn starch increased both their loss modulus and storage modulus. Dynamic rheological measurements revealed the interaction between LEBG and starch. During in vitro digestion, the rates of enzymatic hydrolysis of wheat starch and corn starch supplemented with LEBG were significantly lower than those without LEBG. This difference may be due to the fact that LEBG and starch are intertwined, enhancing the structure of the gel network. At the same time, both starches with LEBG showed lower levels of rapidly digestible starch and predicted glycemic index and higher levels of slowly digestible starch and resistant starch, indicating that LEBG has an inhibitory effect on the in vitro digestion of starch. In the visualization experiment, we further confirmed that starch was wrapped by LEBG. Ultrafine Lentinus edodes powder could also inhibit in vitro starch digestion due to its β-glucan. This study has indicated that LEBG shows promise for developing low-glycemic-index starchy foods.
Comparison of Antioxidant Activity and Enzyme Inhibitory Activity of Different Plant Parts of Torreya grandis cv. Merrillii
ZHANG Lu, LIU Pengfei, TU Zongcai, XIE Xing, ZHANG Shuya, SHA Xiaomei, WANG Hui, DAI Huajian
2018, 39(10):  78-83.  doi:10.7506/spkx1002-6630-201810013
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This study aimed to compare the phytochemical constituents, antioxidant activity, anti-diabetes activity and anti-gout potential of the leaf, stem, aril, seed shell and seed kernel of Torreya grandis cv. Merrillii by analyzing the contents of phenolics, flavonoids and condensed tannins, as well as radical scavenging ability and inhibitory activities against α-glucosidase and xanthine oxidase. The results indicated that the main bioactive constituents, antioxidant activity and α-glucosidase inhibitory activity of different plant parts varied significantly (P < 0.05). The kernel and leaf extracts had the highest total phenolic content (25.28 mg GAE/g) and condensed tannins content (1.10 mg CE/g), respectively. The highest content of flavonoids was found in the stem and aril extracts (P > 0.05). Bioactivity analysis revealed that the kernel extract showed the strongest 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging ability, 2,2’-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS+·) scavenging ability, inhibitory activities against α-glucosidase and xanthine oxidase, and its α-glucosidase inhibitory activity (IC50 = 0.14 mg/mL) was much higher than that of the positive control acarbose (IC50 = 1.29 mg/mL). Thus, it can be concluded that the seed kernel of Torreya grandis cv. Merrillii is a better resource of natural antioxidants and inhibitors of both α-glucosidase and xanthine oxidase than its leaf, stem, aril and seed shell.
Relationship between Flowability and Particle Structure of Dietary Fiber Powders
WANG Yang, YAN Caizhi, YE Fayin, LEI Lin, ZHAO Guohua
2018, 39(10):  84-88.  doi:10.7506/spkx1002-6630-201810014
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The particle structure, flowability and their relationship between dietary fiber powders from various sources (mushroom, cereal, fruit and vegetable) were comparatively investigated in the present work. The results indicated that there were large differences among the particle sizes (D10, 130.3–9.0 μm), specific surface areas (2.06–0.18 m2/g), pore volumes (13.15–0.37 cm3/g), pore diameters (61.46–4.45 nm) and angles of repose (32.01°–56.85°) and slide (21.90°–54.94°) of forty dietary fiber powders, which were not significantly dependent on the source. In terms of pore diameter, all the dietary fiber powders except that from sugarcane were classified as mesoporous materials. Correlation analysis revealed that particle size was negatively correlated to specific surface and span while pore volume was positively correlated to specific surface and pore diameter. More importantly, the flowability of dietary fiber powder was significantly correlated to its particle size, specificity and pore volume, but it was not tightly correlated to its pore span and volume.
Formation of γ-Oryzanol/β-Sitosterol and Monoglyceride Organogels: Process and Molecular Mechanism Studies
LI Sheng, MA Chuanguo, LIU Jun, SI Tianlei
2018, 39(10):  89-96.  doi:10.7506/spkx1002-6630-201810015
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In this study, composite organogels containing sunflower seed oil were prepared with oryzanol/sitosterol and monoglycerides as gelators. The formation process of organogels and the influence of monoglycerides on the gelation process were examined. It was found that this process could be divided into three stages. Monoglycerides had little influence on the supercooling and supersaturatation stages. In the logarithmic stage of aggregation nucleation of gelators, monoglycerides could increase the enthalpy per unit volume and reduce the total Gibbs free energy, consequently promoting nucleation. In the linear stage of crystal growth and assembly, the primary, secondary and tertiary structures of organogels were gradually formed; the tertiary structure was most closely related to macroscopic properties and its ratio of permanent crosslinking to instantaneous crosslinking determined the main properties of organogels. Nuclear magnetic resonance analysis showed that the gelation process was mainly ascribed to physical entrapment. Furthermore, X-ray diffraction and small angle X-ray scattering were used to analyze the assembly structure and the results showed that a symmetrical hexagonal structure was found in oryzanol/sitosterol organogels, a symmetric layered structure in monoglycerides organogels, and composite organogels containing oryzanol/sitosterol and monoglycerides had a symmetric cubic structure.
Preparation, Stability and Antioxidant Activity of Lotus Seedpod Oligomeric Procyanidin Nanoliposome
YIN Hao, CHEN Ya, TAO Tao, XIE Bijun, SUN Zhida
2018, 39(10):  97-105.  doi:10.7506/spkx1002-6630-201810016
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Lotus seedpod oligomeric procyanidin (LSOPC)-loaded nanoliposome was prepared by reverse-phase evaporation method in combination with ultrasonic treatment. The preparation process was optimized and the stability and antioxidant activity of the nanoliposome were determined in this research. The results indicated that the optimal parameters of the preparation process were as follows: ratio of phosphatidylcholine and cholesterol, 3:1; LSOPC concentration, 0.33 mg/mL; and Tween 80 concentration, 16.7 mg/mL. The average particle size of the nanoliposome prepared under these conditions was (35.57 ± 0.08) nm, and the polydispersity index was 0.153 ± 0.01. The highest encapsulation efficiency of (71.97 ± 0.42)% was achieved at an LSOPC concentration of 1%. The spherical vesicle structure was observed by transmission electron microscopy, and the nanoliposome was found to be stable at low temperature. Low concentrations of glucose and sucrose had little impact on the size of LSOPC nanoliposome. Fe3+, Cu2+, Zn2+, and Pb2+ affected its size. Compared with the nanoliposome, the 2,2’-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt scavenging activity and ferric reducing power of LSOPC solution dropped significantly after being stored at 4 ℃ for a week. LSOPC nanoliposome had higher total antioxidant capacity, as measured by oxygen radical absorbance capacity (ORAC), than LSOPC solution.
Effect of Highland Barley β-Glucan on Starch Digestibility in Vitro
DENG Jing, MA Xiaohan, ZHAO Tiantian, YI Jiwu, LIU Xiong
2018, 39(10):  106-111.  doi:10.7506/spkx1002-6630-201810017
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In this paper we compared the digestibility in vitro of highland barley and wheat flour and investigated the effects of β-glucan concentration and molecular mass from highland barley on its starch digestibility in vitro. Furthermore, a possible mechanism for the low glycemic index of highland barley β-glucan was proposed based on its rheological properties and interaction with α-amylase. The results showed that the in vitro starch digestibility of highland barley was significantly lower than that of wheat flour. The viscoelasticity of β-glucan solution increased with the increase in its concentration and molecular mass, its inhibitory effect on α-amylase activity became stronger, and it became more effective in delaying starch digestion. These results indicated that the high viscosity of highland barley β-glucan solution could be regarded as a potential mechanism for the low starch digestibility of highland barley.
Bioengineering
Isolation, Identification and Biological Characteristics of Excellent Lactic Acid Bacteria from Fermented Hot Pepper
YE Ling, LI Yong, WANG Rongrong, LIU Chengguo, JIANG Liwen, DENG Fangming, ZHOU Hui
2018, 39(10):  112-117.  doi:10.7506/spkx1002-6630-201810018
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Lactic acid bacteria were isolated from fermented pepper and five strains of Lactobacillus sp. were screened out based on their acid production and nitrite depletion ability. By biochemical tests and genetic analysis based on 16S rDNA sequence, strains W-4, Y-5 and Y-12 were identified as L. plantarum, and the other two strains Y-25 and Y-31 were identified as L. brevis. The stress response indicated that the L. plantarum survived better under acidic and osmotic stresses as compared with L. brevis, and L. plantarum W-4 had the strongest tolerance ability. All five strains were sensitive to erythromycin, ampicillin, gentamicin, tetracycline and penicillin G.
Purification and Some Enzymatic Properties of Acid Protease from Monascus anka
YUAN Jianglan, HE Shouchun, KANG Xu, HUANG Yaming, CHEN Xiaomin
2018, 39(10):  118-124.  doi:10.7506/spkx1002-6630-201810019
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Extracellular acid protease was obtained from Monascus anka CICC 40806 by ammonium sulfate precipitation, followed by anion exchange column chromatography with CM Sepharose, and then enzymatic and kinetic properties were determined. The results showed that the optimal pH value for the enzyme activity was 3.0 and the enzyme was stable in the pH range of 3.0–7.0. Its optimal reaction temperature was 50 ℃ and the enzyme was stable at temperature below 50 ℃; the attenuation constant at 50 ℃ was 0.569. The activation energy (Ea) was 28.85?kJ/mol when the substrate was casein. The protease had good salt resistance, and its residual enzymatic activity was 12% at a salt concentration of 7%. When the substrates were casein, rice dreg protein (RDP) and bovine serum albumin, the Km values were 12.48, 14.77 and 20.05?mg/mL, respectively, and it had higher catalytic efficiency for RDP and casein. The extracellular acid protease could play a positive role in fermentation and degradation of RDP.
Preparation and Antihypertensive Activity of Angiotensin I-Converting Enzyme (ACE) Inhibitory Peptides Derived from Sea Cucumber (Stichopus japonicas)
HUA Xin, SUN Lechang, WAN Chujun, TANG Yi, WENG Ling, LIU Guangming, CAO Minjie
2018, 39(10):  125-130.  doi:10.7506/spkx1002-6630-201810020
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The body wall of sea cucumber (Stichopus japonicus) was hydrolyzed by protamex proteinase to produce angiotensin I-converting enzyme (ACE) inhibitory peptides. Using one-factor-at-a-time method, the optimum hydrolysis conditions to obtain the highest ACE inhibitory activity were determined as follows: solid to liquid ratio, 1:6 (g/mL); proteinase dosage, 0.8% (m/m); hydrolysis time, 6 h; and hydrolysis pH, 7.0. Ultrafiltration of the resulting hydrolysate yielded a less than 3 kDa fraction with ACE inhibitory activity, whose IC50 was 0.8 mg/mL. Kinetic analysis showed that the inhibitory action of the fraction on ACE was non-competitive. The ACE inhibitory peptides were stable under high temperature, acidic or alkaline conditions and were resistant to gastrointestinal digestion in vitro. Furthermore, these peptides could significantly decrease systolic blood pressure in spontaneously hypertensive rats (SHRs). The present work could provide a theoretical basis for the development of sea cucumber peptides with ACE inhibitory activity as potential antihypertensive food ingredients.
Changes in Volatile Constituents and Gene Expression Involved in Terpenoid Biosynthesis in Ponkan Fruit Peel during Peel Puffing
YAO Shixiang, CAO Qi, XIE Jiao, DENG Lili, ZENG Kaifang
2018, 39(10):  131-137.  doi:10.7506/spkx1002-6630-201810021
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The present study employed gas chromatography-mass spectrometry (GC-MS) and RNA-Seq to probe the changes in volatile constituents and the expression of genes involved in terpenoid biosynthesis in ponkan fruit peel during peel puffing. The results obtained were as follows. A total of 53 volatile components were identified in normal and puffing fruits, with terpenoids accounting for up to 96% of the total amount. Normal and puffing fruits did not differ with respect to volatile composition except for the contents of 32 volatile components. The contents of total volatile compounds and terpenoids in puffing fruits decreased to 82% and 81.4% as compared with the normal fruits, respectively. A total of 12 key genes involved in terpenoid biosynthesis were identified, most of which were down-regulated significantly during peel puffing. This study revealed for the first time the pattern of change in volatile constituents in ponkan fruit peel during peel puffing, and that this dynamic pattern was closely related with the down-regulation of gene expression involved in terpenoid biosynthesis.
Comparison of Intestinal Microbial Diversity in Cold-Water Fishes in Xinjiang by 16S rRNA High-Throughput Sequencing
HUANG Lili, ZHANG Yan, ZHOU Hong, NI Yongqing
2018, 39(10):  138-144.  doi:10.7506/spkx1002-6630-201810022
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This study aimed to understand the intestinal microbial diversity and community structure of wild cold-water fishes in Eerqisi River in Altay region, Xinjiang, China. The V4 region of the 16S rRNA gene was sequenced by high-throughput sequencing and the microbial community compositions in the intestinal contents and mucosa of three kinds of cold-water fish were compared. A total of 58 328 effective sequences and 242 operational taxonomic units (OTUs) were obtained. Diversity analysis indicated that the Shannon index in Hucho taimen was lower than those in Qinling lenok and Esox reicherti. The microbial community structure of Qinling lenok was closer to that of Esox reicherti. At the phylum level, Firmicutes and Gammaproteobacteria dominated the microbiota of six fish samples. Firmicutes was the most dominant phylum in Hucho taimen samples. However, Gammaproteobacteria was increased significantly in Qinling lenok and Esox reicherti, whereas Firmicutes was decreased sharply. At the genus level, Carnobacterium was the most abundant in Hucho taimen. Psychrobacter, Acinetobacter and Clostridium sensu stricto were the main microbial populations in both Qinling lenok and Esox reicherti. Marked differences were detected in the microbial community composition and diversity of different cold-water fishes, while for the same fish the microbial community composition in the intestinal contents and mucosa was similar, without significant differences.
Effects of Cu2+ on Paenibacillus polymyxa Proliferation and Conversion of Ginsenosides
XIAO Ruxue, ZANG Pu, GAO Yugang, ZHAO Yan, ZHU Hongyan, HE Zhongmei, YANG He, LIU Shuangli, ZHANG Lianxue
2018, 39(10):  145-150.  doi:10.7506/spkx1002-6630-201810023
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Objective: This study aimed to examine the effect of Cu2+ on the proliferation of Paenibacillus polymyxa and the conversion of ginsenosides. Methods: A microplate reader and HPLC were used for this study. Results: Cu2+ at 10–50 mg/L improved P. polymyxa proliferation and the best effect was observed at 30 mg/L, where it entered the logarithmic growth phase earlier 1 d and the biomass was significantly increased as compared with the control group. The presence of Cu2+ at 10–50 mg/L in the culture medium improved?the conversion of ginsenosides by P. polymyxa and its effect was strongest at 30 mg/L. However, when the concentration of Cu2+ exceeded 100 mg/L, the conversion of ginsenosides was inhibited, and this inhibition was increased with increasing Cu2+ concentration. Conclusion: A Cu2+ concentration of 30 mg/L improved P. polymyxa proliferation and the conversion of ginsenosides.
Optimization of Fermentation Process of Lonicera caerulea Berry Wine and Effect of Fermentation on Anthocyanin Composition
LIANG Min, BAO Yihong
2018, 39(10):  151-157.  doi:10.7506/spkx1002-6630-201810024
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In the present study, the fermentation process of Lonicera caerulea berry wine was optimized and its effect on anthocyanin composition was examined. By comparing the effects of different yeast strains and different carbohydrates on total acid, residual sugar, anthocyanin content, alcohol content and sensory score, special wine yeast (Angel Yeast Co. Ltd.) and sucrose were determined as the best strain and carbon source, respectively. The effects of yeast inoculum amount, initial pH and fermentation temperature on the physicochemical and sensory properties of blue indigo fruit wine were studied. Optimization of the three independent variables was carried out by one-factor-at-a-time and orthogonal array design methods. Each independent variable was set at three levels. The results showed that the optimum fermentation conditions were determined as follows: inoculum amount, 0.15%; initial pH, 3.2; and fermentation temperature, 26 ℃. After fermentation under these conditions for 12 days, the alcohol concentration was 9.33% (V/V), the sensory score was 75.15 and the anthocyanin concentration was 80.49 mg/L, which accounted for 38.13% of the initial value (211.0 mg/L). Analysis by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) showed that the same 8 anthocyanins were detected in both juice and wine. The peak area of cyanidin-3-hexoside-catechin, peonidin-3,5-dihexoside, cyanidin-3,5-dihexoside, peonidin-3-rutinoside, cyanidi-n-3-acetylhexoside and peonidin-3-glucoside increased in the wine compared with the juice, whereas those of cyanidin-3-glucoside and pelargonidin-3-glucoside decreased.
Response Surface Methodology for Optimization of Hydrolysis Conditions for Preparing Antioxidant Peptides from Quinoa Bran Protein
TIAN Xujing, DUAN Penghui, FAN Sanhong, ZHANG Jingting
2018, 39(10):  158-164.  doi:10.7506/spkx1002-6630-201810025
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Quinoa bran protein was enzymatically hydrolyzed to prepare antioxidant peptides. Various proteases were screened and a mixture of flavourzyme and alcalase (1:1) was selected as the optimal enzyme. The enzymatic hydrolysis process was optimized by investigating the effects of various factors and their interactions on reducing power using one-factor-at-a-time method and response surface methodology. An enzyme dosage of 3 600 U/g, pH 7.66, a hydrolysis time of 2.13 h and a temperature of 50.53 ℃ were found to the optimal conditions to obtain a higher yield of antioxidant peptides of 76.25%. The predicted reducing power of the antioxidant peptides prepared under the optimized conditions was 0.636 5, in good agreement with the actual average value of 0.644. The antioxidant peptides had potent superoxide anion and hydroxyl radical scavenging capacity in a concentration-dependent manner, thereby holding promise in the field of natural antioxidant and health food applications.
Melatonin Treatment Enhances Content of Resveratrol via Up-regulating Stilbene Synthase (sts) Gene Expression in Grape
XU Lili, YUE Qianyu, BIAN Feng’e, ZHAI Heng, YAO Yuxin
2018, 39(10):  165-172.  doi:10.7506/spkx1002-6630-201810026
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Objective: This study aimed to investigate whether melatonin treatment could induce the expression of stilbene synthase (sts) genes and thereby enhance content of resveratrol in grapevine. Methods: The whole grape clusters were treated with 100 μmol/L melatonin at early veraison, and the roots of in vitro shoot cultures were treated with 30 μmol/L melatonin for approximately 30 days after subculture. RNA-Seq with the grape genome data as a reference was employed to identify melatonin-induced sts genes. Sequence and clustering analysis were performed using Clustalx and MEGA5 software, and the cis-acting elements in the promoter region were identified using online plantCARE software. The expression levels of sts genes were detected using quantitative real-time PCRs. The content of resveratrol was determined by high performance liquid chromatography (HPLC). Results: RNA-Seq analysis showed that 30 sts genes were up-regulated by melatonin treatment, accounting for 62.5% of the total amount of grape sts genes and 8.5% of all the up-regulated genes. The melatonin-induced sts genes were primarily located in chromosome 16 and their deduced proteins shared more than 88.3% similarity; only one different amino acid existed between the two sts with the highest similarity. The promoter regions of different sts genes were also highly conserved and their similarity surpassed 55.6%. The detected 30 sts genes were clustered into three groups, i.e., A, B and C, in the light of their sequence similarity of protein or promoter. A highly conserved sequence was found in the promoters of sts genes from groups A and B. Additionally, there were a number of cis-acting elements present in the promoters of sts gens related to ABA-, ethylene-, salicylic acid- and auxin-responsive elements. The 30 melatonin-induced sts genes exhibited varying expression patterns in different tissues and generally they were predominantly expressed in grape roots; additionally, they had varying transcriptional abundance in grape berries. qRT-PCR analysis showed that the 5 selected sts gens were induced by melatonin, consistent with the results of RNA-Seq, and exhibited different expression patterns in response to melatonin. Conclusions: A total of 30 sts genes were induced by melatonin in grape berries and they shared highly conserved protein and promoter sequences. The promoter regions of 30 sts gens contained different cis-acting elements and they exhibited different expression patterns in response to melatonin treatment. Melatonin treatment enhanced the content of resveratrol in grape berries and roots. The results of this study laya basis for the application of melatonin in improving the nutritional value of grape berries and shed light on the molecular mechanism underlying the regulation of melatonin on resveratrol metabolism
Classification of Natural Plasmids in Lactobacillus brevis
SUN Daqing, LI Hongfei, YANG Jian, SONG Dawei
2018, 39(10):  173-178.  doi:10.7506/spkx1002-6630-201810027
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This study aimed to establish a method for the classification of natural plasmids from Lactobacillus brevis. A total of 51 natural plasmids of L. brevis were accurately and efficiently divided into 6 family types and 11 subfamily types through the replication initiation protein (Rep) phylogenetic tree and genome colinearity analysis. A new type of replicon was found in the plasmids of family 4. The results showed that both the Rep phylogenetic tree and genome colinearity analysis were effective methods for the classification of natural plasmids in L. brevis. The classification results will provide a theoretical foundation for the scientific classification and reasonable application of L. brevis natural plasmids in the future.
Application of Droplet Digital PCR in Screening of Genetically Modified Saccharomyces cerevisiae for Multicopy Expression of Xylanase
LAN Xue, ZHANG Sitong, LI Zhe, CHANG Hao, SUN Yang, WANG Gang, CHEN Huan, WANG Chunfeng, CHEN Guang
2018, 39(10):  179-184.  doi:10.7506/spkx1002-6630-201810028
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In order to obtain a high yield of xylanase from genetically engineered Saccharomyces cerevisiae, the S. cerevisiae expression vector for the multicopy expression of the xylanase gene was constructed by rDNA integration method. Then, the copy number of transformants was detected by droplet digital PCR, and the relationship between the copy number of the xylanase gene and the enzyme activity was analyzed. The results indicated that 10 strains of S. cerevisiae were obtained by rDNA integration method. Their enzymatic activity was measured. The xylanase production capacity was increased to the maximum of 308 U/mL with copy number up to 9, but decreased when the copy number was more than 9.
Inhibitory Effects of Peptides Derived from Tryptic Hydrolysate of Skin Collagen from Melanogrammus aeglefinus on UVB-Induced Photodamage in HaCaT Cells
DONG Lisha, LI Yanyan, ZHANG Hongyan, CUI Chenxi, HAN Jiaojiao, WANG Zhaoyang, SI Kaixue, ZHOU Jun, LU Chenyang, SU Xiurong
2018, 39(10):  185-192.  doi:10.7506/spkx1002-6630-201810029
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Objective: This study aimed to examine the antioxidant activity of peptides produced by tryptic hydrolysis of skin collagen from Melanogrammus aeglefinus and its inhibitory effect against photodamage in an effort to improve the reuse potential of M. aeglefinus skin. Methods: One-factor-at-a-time method and response surface methodology were used in conjunction to determine the optimum hydrolysis process for skin collagen from M. aeglefinus. The obtained peptides were sequenced by matrix-assisted laser desorption/ionization time of flight tandem mass spectrometry (MALDI-TOF MS/MS). The dominant peptides were docked with Kelch-like ECH-associated protein 1 (Keap1) by using the CDOCKER module in Discovery Studio. At the same time, HaCaT cells were pretreated with different concentrations of the collagen hydrolysate and then induced by ultraviolet B (UVB) to establish a cellular model of photodamage. The activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), malondialdehyde (MDA) and the cell apoptosis and cycle were examined to test the ability of the peptides to inhibit photodamage. Results: Optimal hydrolysis conditions were determined as follows: hydrolysis time 1.75 h, enzyme concentration 1.23%, and temperature 52.95 ℃. The corresponding degree of hydrolysis was 78.33%. The dominant peptide sequences in the hydrolysate were identified as V-IFFVTMGTP-R, L-SIVPV-R and L-MHT-T. Molecular docking showed that the binding of V-IFFVTMGTPR to Keap1 was the most stable, thereby predicting that the peptide has antioxidant effect. The SOD and GSH-Px activities of HaCaT cells treated with the hydrolysate at 250 mg/mL were significantly higher than those of the model group (P < 0.01), accompanied by a significant decrease in MDA content (P < 0.01). Conclusion: The tryptic hydrolysis of collagen from M. aeglefinus skin has antioxidant activity, and an inhibitory effect on photodamage.
Antibacterial Mechanism of Bacteriocin from Lactobacillus casei
MA Jiage, YU Wei, LI Jiajun, ZHOU Shihao
2018, 39(10):  193-198.  doi:10.7506/spkx1002-6630-201810030
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Objective: This study aimed to analyze and predict the molecular structure and physicochemical properties of the bacteriocin gene and its encoded protein from Lactobacillus casei and to clarify the antibacterial mechanism of the bacteriocin. Methods: A variety of bioinformatics software were used to predict and analyze protein structure and function. Site-directed mutagenesis was applied to the predicted amino acid sites, and the antibacterial activities of the mutants were detected. Results: Bacteriocin from L. casei (LacA and LacB) was thermally stable, contained a secretory signal peptide and had a transmembrane region. LacA contained a typical antimicrobial domain GxxxG. The mutant vectors for V40 and I57 in LacA were constructed, and the antimicrobial activity was significantly reduced when any of these two amino acids was mutated. Conclusion: V40 and I57 could be the key amino acid residues responsible for the antibacterial activity of L. casei. This study has provided a theoretical basis for exploring the antibacterial mechanism of bacteriocin from L. casei (class IIb).
Effects of an Ester Aroma-Producing Bacterial Strain on Maotai-Flavor Fermented Grains
CHEN Mengyuan, LIU Xuebin, WANG Ping, CHEN Jian, CAI Xuemei, LUO Aimin
2018, 39(10):  199-205.  doi:10.7506/spkx1002-6630-201810031
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The purpose of this study was to investigate the effects of an ester aroma-producing bacterial strain on Maotai-flavor fermented grains. High-throughput sequencing technique and gas chromatography were used to analyze the differences in aroma composition and bacterial community structure as well as physicochemical properties between the experimental and blank groups after stacking and fermentation. The results showed that during stacking and fermentation, the bacterium had little effect on moisture, acidity, reducing sugar and starch, but it could enhance proteinase activity, amino nitrogen content and esterification degree. At the same time, the bacterial strain mainly affected the bacterial community structure during the stacking process, as indicated by an increase in Bacillus counts and the number of bacterial species, consequently reducing the contents of alcohols, acid compounds, aldehydes and ketones and increasing ester content.
Component Analysis
Principal Component Analysis of Volatile Compounds in Different Grades of Lu Mountain Clouds-Mist Tea from Three Regions
LIU Ye, GE Liqin, WANG Yuanxing
2018, 39(10):  206-214.  doi:10.7506/spkx1002-6630-201810032
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The volatile compounds of different grades of Lu Mountain Clouds-Mist Tea from three regions (Tongyuan township, Saiyang township, and Xingzi county) were investigated by solid phase micro extraction (SPME) followed by gas chromatography-mass spectrometry (GC-MS). A total of 76 of volatile components were identified. Principal component analysis was applied to find out the main factors affecting the volatile components in different grades of Lu Mountain Clouds-Mist Tea. The results showed that the first 4, 3 and 3 principal components contributed cumulatively to 80.4%, 87.9% and 89.8% of the total variation for the teas from Tongyuan, Saiyang and Xingzi, respectively. Different grades of tea could be discriminated by their respective chemical properties. The volatile compounds with variable importance in the projection (VIP) value greater than 1 in the loading plots were screened for the characteristic aroma compounds in different grades of tea. The results showed that the higher grade and more expensive Lu Mountain Clouds-Mist tea had higher contents of aroma compounds, such as hexanal, (Z)-3-hexen-1-ol, hexanol, heptanal, benzaldehyde, 2-pentyl-furan, limonene, isophorone, linalool, and jasmone. This study provides a new idea for grade discrimination of Lu Mountain Clouds-Mist Tea.
Relationship between Contents of Mineral Elements and Quality of Hot Pepper Grown in Zunyi, Guizhou Province
ZHANG Jian, YANG Ruidong, CHEN Rong, PENG Yishu, WEN Xuefeng, REN Haili
2018, 39(10):  215-221.  doi:10.7506/spkx1002-6630-201810033
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The contents of twelve mineral elements (K, Ca, Mg, P, S, Fe, Mn, Zn, Cu, Mo, Ni, and Co) and four quality attributes (capsaicin, vitamin C, protein, and dry matter) of hot pepper samples collected from Zunyi, Guizhou were determined. The relationship between the quality and the mineral elements was studied. Moreover, principal component analysis (PCA) and hierarchical cluster analysis (HCA) were used to analyze the quality of hot pepper. The results showed that the contents of twelve mineral elements were in the following order: K > P > S > Mg > Ca > Fe > Zn > Mn > Cu > Ni > Mo > Co. Compared with data from previous studies, the contents of protein, vitamin C, and dry matter in Zunyi grown hot pepper were higher, being rich in nutrients. Nonetheless, the capsaicin content of Zunyi grown red pepper varied in a wide range. Vitamin C content was significantly positively correlated with copper content (r = 0.584, P < 0.05, n = 16), as well as the contents of K, Ca, Mg, P, S, and Zn. In addition, PCA showed that the cumulative contribution rate of the first two principal components was 49.368%, which indicated that capsaicin was an important indicator in assessing the quality of hot pepper, and the characteristic elements were K, Mg, P, S, Zn, Cu, Ni, and Co. Besides, the results of HCA revealed that there were some differences in the quality and mineral elements of hot pepper from different regions, and the quality and mineral elements contents of hot peppers from the same area were similar. A regional distribution pattern was observed for hot pepper quality.
GC-MS/GC-O Combined with Chemometrics for the Screening and Identification of Aroma Characteristics of Korla Pear Wine
ZHOU Wenjie, ZHANG Fang, WANG Peng, ZHAN Ping, TIAN Honglei
2018, 39(10):  222-227.  doi:10.7506/spkx1002-6630-201810034
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Headspace solid phase microextraction combined with gas chromatography-mass spectrometry (SPME-GC-MS) was applied to identify and analyze the volatile aroma compounds of Xinjiang Korla pear wine, and gas chromatography-olfactometry (GC-O) with odor specific magnitude estimation (OSME) and odor activity values (OAV) was applied to determine the characteristic aroma components of Korla pear wine. Chemometrics was used to establish the correlation between aroma compounds and sensory attributes of Korla fragrant pear wine. A total of 51 aroma components were identified, including 15 alcohol compounds, 19 esters, 5 aldehydes, 4 ketones, 2 phenols, 3 acids and 3 other compounds. The aroma compounds identified by both OSME and OAV methods were 1-nonanol, phenyl alcohol, ethyl hexanoate, ethyl caprylate. Partial least squares regression (PLSR) analysis indicated a good correlation between these characteristic aroma compounds and the sensory attributes of Korla pear wine.
Application of Electronic Nose in Aroma Prediction of Pork Balls
JIANG Qiang, ZHENG Limin, TIAN Lijun, CHENG Guodong, MENG Wanlong
2018, 39(10):  228-233.  doi:10.7506/spkx1002-6630-201810035
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The feasibility of rapidly and objectively evaluating the flavor of pork balls using an electronic nose was investigated. The odor of four pork meatballs with different proportions of lean (100%, 90%, 80% and 70%) was analyzed by the electronic nose, and their volatile compounds were determined by head space-solid phase microextraction (HS-SPME) coupled to gas chromatography-mass spectrometry (GC-MS). Besides, the aroma intensity was scored by a trained sensory panel. Both linear discriminant analysis (LDA) and neural network algorithm (NNA) were used to identify and classify the electronic nose data. Partial least squares regression (PLSR) was applied to correlate the aroma compounds identified by electronic nose sensors and GC-MS data. The results showed that there were significant differences in the aroma scores of four meatball samples (P < 0.01). The meatballs with higher proportion of fat had higher sensory scores. Analysis by LDA and NNA demonstrated that the aroma profiles of all four samples could be discriminated by the electronic nose. A total of 67 volatile aroma compounds were detected by GC-MS, mainly including aldehydes, alcohols and ketones. Differences in volatile flavor compounds were mainly responsible for the differences in sensory scores. The PLSR model established exhibited good correlation between the electronic nose data and the relative contents of major volatile compounds. The prediction model established by stepwise regression (R2 > 0.9, P < 0.01) indicated that the electronic nose can be used to predict the aroma of meatballs with reliable results.
Comparison of Different Extraction Fibers for Analysis of Characteristic Aroma Compounds in Xinjiang Roasted Lamb by SPME-GC-MS and PCA
XI Jiapei, ZHAN Ping, TIAN Honglei, WANG Peng, GENG Qiuyue, WANG Yongxiao, ZHANG Fang, JI Yunyun
2018, 39(10):  234-241.  doi:10.7506/spkx1002-6630-201810036
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The volatile flavor compounds of roasted lamb in Shihezi, Xinjiang were determined by solid phase microextraction (SPME) coupled with gas chromatography-mass spectrometry analysis (GC-MS). Various SPME fibers were screened for their ability to extract the key volatile compounds. The optimal SPME fiber was selected as 75 μm CAR/PDMS based on sensitivity and key common compounds with projections greater than 0.80 in the loading matrix of principle component analysis (PCA). The correlation of different fibers (75 μm CAR/PDMS, 65 μm DVB/PDMS, 85 μm PA, 100 μm PDMS and 50/30 μm DVB/CAR/PDMS) with the extracted volatile compounds was examined. The key aroma components extracted with the selected SPME fiber were 1-octen-3-ol, n-heptaldehyde, pentanal, dodecanal, (E)-2-decenal dehyde, hexanal, benzaldehyde, 1-tetradecyne, naphthalene, 4-methylnonanoic acid, 6-methylheptanal, cuminaldehyde, decyl aldehyde, nonylaldehyde, 2-methyl-3-methylthio furanl, octanal, and phenylbenzene.
Analysis of Aroma Components in Four Chinese Congou Black Teas by Odor Active Values and Aroma Extract Dilution Analysis Coupled with Partial Least Squares Regression
XIAO Zuobing, WANG Hongling, NIU Yunwei, ZHU Jiancai, MA Ning
2018, 39(10):  242-249.  doi:10.7506/spkx1002-6630-201810037
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The volatile components of four Chinese congou black teas were qualitatively and quantitatively investigated by headspace steam distillation extraction (HSDE) followed by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O). Thirty, thirty six and twenty two volatile components were identified as aroma-active compounds by odor active values (OAV), aroma extract dilution analysis (AEDA) and their combination, respectively. The correlations between sensory attributes and key aroma-active compounds were modeled by partial least squares regression (PLSR). Twenty two key aroma-active compounds were found to make an important contribution to the aroma of Chinese congou black tea, including 1-pentanol, cis-3-hexen-1-ol, 1-octen-3-ol, trans-linalool oxide, linalool, cis-6-nonenol, geraniol, benzyl alcohol, phenylethyl alcohol, nerolidol, valeraldehyde, hexanal, trans-2-hexenal, furfural, (E,E) -2,4-heptadienal, phenylacetaldehyde, (E,E)-2,4-decedienal, methyl salicylate, γ-nonalactone, 2,3-butanedione, 2-heptanone, and coumarin.
Nutritional and Medicinal Quality of Mulberry Fruit from 13 Main Varieties Grown in Guangxi
HE Xuemei, SUN Jian, LIANG Guiqiu, QIU Changyu, LI Jiemin, LI Li, LI Changbao, SHENG Jinfeng, LIU Guoming, LING Dongning, TANG Yayuan
2018, 39(10):  250-256.  doi:10.7506/spkx1002-6630-201810038
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The major nutritional and functional components of mulberry fruit from 13 main varieties grown in Guangxi region of China were investigated by factor analysis in an effort to evaluate their nutritional and medicinal quality and to screen out special varieties for the development of food and pharmaceutical products. The factor analysis of nutritional quality indicated that 5 principal components extracted from 15 quality indicators could reflect the comprehensive information on nutritional quality with a cumulative contribution rate of 86.32%. The contents of vitamin, microelements, amino acids and dietary fiber were the main factors influencing nutritional quality. Te 2, Da 10 and Guiyou M161 ranked first to third by comprehensive score among 13 varieties. These three varieties were suitable for food development. The factor analysis of medicinal quality indicated that 3 principal components extracted from 9 quality indicators could reflect the comprehensive information on medicinal quality with a cumulative contribution rate of 88.02%. The main factors influencing medicinal quality were the contents of polyphenols, chlorogenic acid, rutin and anthocyanins. The comprehensive scores of Guiyou M257, Guisangyou 62 and Da 10 were ranked the top three among 13 varieties. These three varieties were suitable for the development of healthcare products and medicines.
Effects of Yeast Species and Nitrogen Sources on Volatile Aroma Composition of Bog Bilberry Wine
WEI Ming, ZHAO Laiyu, YANG Hangyu, WU Yuwen, LI Teng, WANG Shaoyang, ZHU Baoqing, ZHANG Bolin
2018, 39(10):  257-262.  doi:10.7506/spkx1002-6630-201810039
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The aroma components of bog bilberry wines fermented by different yeast species utilizing different nitrogen sources were analyzed by headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography-mass spectrometry (GC-MS). The results showed that 86 aroma components were identified in all 4 wine samples, including 32 esters, 18 alcohols, 13 terpenes, 10 acids, 7 aldehydes, ketones and 6 other compounds, and 78 components were common to these samples. The types and amounts of aroma compounds varied with changing the yeast species and the nitrogen source. The yeast “red fruit” in combination with diammonium hydrogen phosphate favored the fermentation of bog bilberry wine and produced higher amounts of isoamylol, isobutanol, ethyl acetate and acetoin, which mainly contributed to the aroma of bog bilberry wine. To sum up, choosing the appropriate yeast species and nitrogen source allowed for improved aroma of bog bilberry wine.
Amino Acid Composition and Nutritional Evaluation of Proteins in Six Samples of Cultivated Flammulina velutipes
WU Yingying, BAO Dapeng, WANG Ruijuan, CHEN Hongyu, WANG Hongmei
2018, 39(10):  263-268.  doi:10.7506/spkx1002-6630-201810040
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To evaluate the nutritional value of proteins in commercially cultivated Flammulina velutipes, the amino acid composition and crude protein contents of 6 samples from different factories were analyzed. The contents of taste-active amino acids were determined and the nutritional value of proteins was assessed by calculating amino acid score (AAS), chemical score (CS), score of ratio coefficient of amino acid (SRC), essential amino acid index (EAAI) and protein digestibility corrected amino acids score (PDCAAS). The results showed that 18 amino acids were detected in the hydrolysate of each of the tested samples, with taste-active amino acids accounting for 56.28%–57.37% of the total amino acids. The content of essential amino acids was close to the WHO/FAO reference protein pattern value; the most abundant essential amino acids were Met and Lys, and the limiting amino acids were Val and Ile. The SRC values were between 72.61 and 82.07, and EAAI values were over 90, both being close to those of ovalbumin. It is concluded that commercially cultivated F. velutipes are rich in taste-active amino acids and high quality proteins that are easily absorbed and has a great potential for the development of flavored foods. F. velutipes is recommended to be combined with cereals and meats in diet for the balanced consumption of amino acids.
HPLC-MS Analysis of Anthocyanin Composition of Wine from ‘Guipu 6’ Grapes
CHENG Guo, HUANG Yu, YANG Ying, XIE Linjun, HUANG Xiaoyun, YU Huan, XIE Taili, ZHOU Yongmei, ZHANG Jin
2018, 39(10):  269-275.  doi:10.7506/spkx1002-6630-201810041
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The composition and content of anthocyanins in wine produced from the wild grape germplasm ‘Guipu 6’ were determined by high performance liquid chromatography-mass spectrometry (HPLC-MS) at the end of alcohol fermentation and after bottle storage for 3 months and compared with those of Cabernet Sauvignon (Vitis vinifera L.) wine. The results indicated that the total anthocyanin contents of fresh and 3-month stored ‘Guipu 6’ wine were 548.94 and 427.89 g/L, which were about 1.2 and 2.7 times as high as those of their Cabernet Sauvignon counterparts, respectively. A total of 25 and 19 anthocyanins were detected in fresh and stored ‘Guipu 6’ wine, respectively. The most abundant form of anthocyanin found in ‘Guipu 6’ wine was diglucoside anthocyanins with peonidin-3,5-O-diglucoside being the most abundant. Compared with Cabernet Sauvignon wine, the 3-month stored ‘Guipu 6’ wine had higher contents of 3’,5’-substituted anthocyanins but lower contents of acylated, methylated and pyranoanthocyanins. There were significant differences in the composition and content of anthocyanins between ‘Guipu 6’ and Cabernet Sauvignon wines, which were dependent on varietal characteristics.
Processing Technology
Application of Combination of ε-Ploy-L-lysine with Other Preservatives in Pickles
SONG Meng, FU Qiang, SHI Yifei, CHENG Yawen, ZHENG Zuoxing, TAN Zhilei, JIA Shiru
2018, 39(10):  276-282.  doi:10.7506/spkx1002-6630-201810042
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To extend the shelf-life pickled vegetables, in this study, we examined the preservative effect of ε-ploy-L-lysine (ε-PL) when combined with other preservatives and antioxidant (nisin, natamycin and tea polyphenols) on pickles. The results showed that the biopreservatives nisin and natamycin as well as the antioxidant tea polyphenols potently inhibited the growth of spoilage bacteria, and their effects were synergistic in combination. The optimal combination determined using response surface methodology was ε-PL 0.06 μg/mL, nisin 0.06 μg/mL, natamycin 0.035 μg/mL and tea polyphenols 0.40 μg/mL. In addition, this combination was more effective when added during seasoning that during rehydration of dried radish and increased the shelf-life to 21 days. The pickle maintained good quality during its shelf-life, and the total number of colonies, the number of coliforms, total acid and amino nitrogen content were in line with the national standard. This study can provide an experimental basis for the application of ε-PL in pickled vegetables.
Optimization of Purification of Flavonoids from Mung Bean Coat by AB-8 Macroporous Resin and Comparison of Antioxidant Capacity of crude and purified Flavonoids
LI Xia, ZANG Xueli, XU Yibo, WANG Dawei
2018, 39(10):  283-290.  doi:10.7506/spkx1002-6630-201810043
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In this study, AB-8 macroporous resin was used to separate and purify flavonoids from mung bean coat. To establish optimized sample loading and the elution conditions, the influence of sample concentration, pH and flow rate as well as eluent concentration, volume and flow rate on the adsorption and desorption efficiencies was investigated. The optimal conditions determined were as follows: sample concentration, 1.5 mg/mL; pH, 5.0; flow rate, 1.0 mL/min; and 225 mL of 70% ethanol as eluent at a flow rate of 2.0 mL/min. Under these conditions, the purity of mung bean coat flavonoids increased from 27.95% to 62.38%. The existence of flavonoids were confirmed by their characteristic peaks in UV-visible spectra and characteristic functional groups identified by infrared spectroscopy. Scanning electron microscopy (SEM) showed that most flaky and powdery particles were released, which might contribute to the increased purity of flavonoids after initial purification. Compared with crude extract, the purified flavonoids had higher antioxidant ability.
Effect of Extraction Techniques on the Extraction and Hypolipidemic Activity in Vitro of Triterpenoids from Inonotus hispidus
LI Dehai, DU Lingjuan, KANG Ning, GU Jialin, WANG Zhanbin
2018, 39(10):  291-297.  doi:10.7506/spkx1002-6630-201810044
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This study aimed to examine the effect of different extraction techniques on the extraction and hypolipidemic activity in vitro of triterpenoids from Inonotus hispidus (IHT). Five extraction techniques i.e., high shear emulsifier-assisted extraction, ultrasound-assisted extraction, aqueous two-phase extraction, semi-bionic extraction and solvent reflux extraction were evaluated for their influences on the extraction efficiency and cholate binding capacity of IHT. The structure of IHT was analyzed by infrared spectroscopy. The results showed that the extraction efficiency and hypolipidemic activity of IHT were significantly different (P < 0.05) among five extracts; high shear emulsifier-assisted extraction gave the highest extraction efficiency of (3.33 ± 0.02)%, which was 2.64 times as high as that ((1.26 ± 0.05)%) of solvent reflux extraction. The cholate binding capacity of IHT extracted by high shear emulsifier-assisted extraction was the most significant (P < 0.05), and its lipid-lowering activity was dose dependent. At a concentration of 40 mg/mL, the binding capacities for sodium glycocholate, sodium cholate and sodium taurocholate were (1.01 ± 0.03), (0.47 ± 0.04), and (1.31 ± 0.09) μmol/100 mg, respectively, which were 36.53%, 27.92% and 46.33% as compared to those of simvastatin, respectively. Infrared spectroscopy analysis showed that the IHT exhibited the characteristic structure of triterpenoids and the strongest characteristic absorption peak. These findings will provide a theoretical basis for the selection of optimal extraction technique for IHT and the development and utilization of hypolipidemic drugs.
Taste Modification of Bitter Melon (Momordica charantia) Powder by Different Bitterness Inhibitors
ZHANG Huimin, DENG Yuanyuan, ZHANG Ruifen, ZHANG Yan, WEI Zhencheng, MA Yongxuan, LIU Lei, ZHANG Mingwei
2018, 39(10):  298-303.  doi:10.7506/spkx1002-6630-201810045
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The effects of ten bitterness inhibitors, namely zinc lactate, neohesperidin dihydrochalcone (NHDC), γ-aminobutyric acid (GABA), sodium caseinate, fat milk, ferulic acid, polydextrose, sucrose, neodiosmin and AMP on the bitterness, delayed bitterness, sweetness, delayed sweetness, astringency and flavor of bitter melon powder suspended in water were studied systematically by the general labeled magnitude scale (gLMS). The synergistic effects of three selected inhibitors on the bitterness and delayed bitterness were also explored. The results indicated that all ten inhibitors had an inhibitory effect on the bitterness, delayed bitterness and astringency of bitter melon. NHDC was more effective than were other inhibitors in inhibiting the bitterness and delayed bitterness, followed by zinc lactate for delayed bitterness and GABA for bitterness. Sodium caseinate was the best inhibitor for the astringency. Sucrose, polydextrose, sodium caseinate and milk could increase the sweetness and delayed sweetness of the whole system. The results of orthogonal array design showed that zinc lactate could affect the bitterness significantly. By adding NHDC, GABA and zinc lactate at 0.60, 3.98 and 4.46 mg/g of bitter melon powder, respectively, the bitterness and delayed bitterness were effectively decreased to almost no perception while maintaining the characteristic flavor of bitter melon without off-flavor.
Extraction and Antioxidant Capacity of Bound Phenolics from Fresh Lotus Seeds
WANG Zhenyu, GE Shenghan, ZHOU Arong, KONG Zihao, ZENG Shaoxiao, ZHENG Baodong, LIN Shaoling, HU Jiamiao
2018, 39(10):  304-311.  doi:10.7506/spkx1002-6630-201810046
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The extraction of bound phenolics from fresh lotus seeds from Jianning was optimized using a central composite design. Optimization experiments were carried out by investigating the effect of solvent pH, alkali concentration, solid-to-solvent ratio and extraction time on extraction efficiency. The extract was fractionated with solvents of different polarities and the resulting fractions were comparatively evaluated for their antioxidant activity by total antioxidant capacity, 1,1-diphenyl-2-picrylhydrazyl (DPPH), and hydroxyl radical scavenging assays. The results showed that the optimum extraction conditions were determined as follows: NaOH concentration, 2.8 mol/L; solid-to-solvent ratio, 1:25 (g/mL); and extraction time, 3.7 h. Under these conditions the yield of bound phenolics was (8.483 ± 0.063) mg/g of dry matter. In addition, all the fractions possessed high total antioxidant capacity, DPPH and hydroxyl radical scavenging capacity in a dose-dependent manner. Among these, ethyl acetate and n-butanol fractions showed higher antioxidant activity. In conclusion, fresh lotus seeds contained abundant bound phenolics and the ethyl acetate and n-butanol fractions exhibited higher antioxidant capacity.
Safety Detection
Screening and Identification of Mycotoxin-Producing Strains from Grains at Harvest Time
PEI Shichun, LI Yan, GAO Jianwei, WANG Yan, WANG Lin, HAN Gidong
2018, 39(10):  312-317.  doi:10.7506/spkx1002-6630-201810047
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This study aimed to screen out mycotoxin-producing fungal strains from wheat, corn and rice at harvest time in northeast China. ELISA, UPLC-MS/MS and PCR were adapted as analytic tools. Fungal isolation, liquid medium culture, primary screening of toxigenic strains, qualitative analysis of toxin production and gene sequence alignment of isolates were carried out. Six toxigenic strains producing zearalenone, deoxynivalenol and fumonisin were obtained and identified by DNA analysis. They were found to belong to four species, Fusarium asiaticum, F. poae, F. graminearum and F. fujikuroi. The results from this study can provide basic experimental data for the targeted prevention and control of toxic fungal contamination in foodstuffs.
Optimization of Solid-Phase Microextraction-Gas Chromatography-Mass Spectrometry Method for Microbial Volatile Organic Compounds from Aspergillus carbonarius
LI Menghua, WANG Guoyi, ZHANG Xiaoxu, ZHANG Lei, CHENG Zhan, MA Liyan, LI Jingming
2018, 39(10):  318-325.  doi:10.7506/spkx1002-6630-201810048
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The aim of this work was to determine the optimal conditions for the analysis of microbial volatile organic compounds (MVOCs) from the common food spoilage fungus Aspergillus carbonarius. The volatile compounds were extracted by solid phase microextraction (SPME) and detected by gas chromatography-mass spectrometry (GC-MS).The influences of extraction fiber, time and temperature were examined. The optimized conditions for SPME were determined as follows: 60 min of extraction at 60 ℃ with 50/30 μm DVB/CAR/PDMS extraction fiber. Under these conditions, 32 MVOCs including 1 aldehyde, 1 ketone, 2 alcohols, 6 esters, 10 sesquiterpenes, 11 hydrocarbons and 1 cyclic dicarboxylic anhydride were detected. Based on the sensory characteristics of these MVOCs, A. carbonarius showed outstanding mushroom-like and hydrocarbon odor.
Mini-DNA Barcode for Identification of Multiple Animal-Derived Ingredients
PAN Yanyi, QIU Deyi, CHEN Jian, YANG Weidong, YUE Qiaoyun
2018, 39(10):  326-332.  doi:10.7506/spkx1002-6630-201810049
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Based on the standard DNA barcodes of 51 animal species, a new pair of universal primers for mini-DNA barcode was designed and combined with clone sequencing to develop an accurate and efficient method for identifying multiple animal derived ingredients. Eleven common edible meat species were identified by the mini-DNA barcode to verify its accuracy in comparison with the results of standard DNA barcode. A mixture in equal proportion of the 11 species was used to evaluate the colon sequencing method. The results showed that the designed primers had favorable universality among 11 species with different levels of sequence homology with primers. Thus, 11 meat species could be accurately identified with the mini-barcode, which showed high consistency to the standard DNA barcode. By clone sequencing, nine species from mixed samples were detected. Furthermore, the reasons why not all the species were detected were discussed. The results of this study can lay a foundation for combining mini-DNA barcode and next generation sequencing technique for efficient species identification in mixed meat.