Table of Content

25 February 2019, Volume 40 Issue 4
Food Chemistry
Effects of TOCNs and Cationic Polyacrylamide on Properties of Sodium Carboxymethyl Cellulose Film
GONG Xiao, TANG Yali, LU Lixin, QIU Xiaolin, WANG Jun
2019, 40(4):  1-6.  doi:10.7506/spkx1002-6630-20171026-297
Asbtract ( 217 )   HTML ( 17)   PDF (2671KB) ( 184 )  
Related Articles | Metrics
To improve the mechanical properties of sodium carboxymethyl cellulose (CMC) films, 2,2,6,6-tetramethyl-1-piperidinyloxy-oxidized cellulose nanofibrils (TOCNs) were incorporated into CMC films to enhance the tensile strength, and cationic polyacrylamide (CPAM) was also added to increase the elongation at break by taking advantage of the electrostatic interaction between the cations produced electrolytically from it and the carboxylate ions formed by TOCNs and CMC in aqueous solutions. Biodegradable blend films with good tensile strength and toughness were obtained. The blend film with an m (CMC):m (TOCNs):m (CPAM) ratio of 50:10:1 exhibited an increase in tensile strength of 177% and an increase in elongation at break of 36% as compared with pure CMC film, accompanied by an increase in light transmittance and thermal stability but a slight decrease in oxygen resistance. Our results showed that the tensile strength and thermal stability of CMC film could be improved obviously by adding TOCNs and the elongation at break and light transmittance could be improved obviously by adding CPAM. There were interactions and good compatibility among the three agents, contributing to improved physical and chemical properties of CMC film.
Interaction between Unfolded Bovine β-Lactoglobulin and Epigallocatechin Gallate
FU Shanlin, ZHONG Junzhen, YAO Wenjun, QIN Fangfang, LIU Chengmei, LIU Wei
2019, 40(4):  7-13.  doi:10.7506/spkx1002-6630-20171212-141
Asbtract ( 222 )   HTML ( 9)   PDF (3028KB) ( 115 )  
Related Articles | Metrics
The interaction mechanism of unfolded bovine β-lactoglobulin (U-β-LG) with epigallocatechin gallate (EGCG) was investigated by using fluorescence, ultraviolet and circular dichroism (CD) spectroscopy. U-β-LG was obtained after β-lactoglobulin (β-LG) was treated by microwave. It was shown that EGCG could interact with β-LG or U-β-LG to form β-LG-EGCG complex or U-β-LG-EGCG complex. The main binding force between EGCG and β-LG or U-β-LG was hydrophobic interaction. The binding distance between donor and acceptor at 298 K were 3.188 and 2.875 nm for β-LG-EGCG complex and U-β-LG-EGCG complex, respectively based on the F?rster’s theory of non-radiative energy transfer. The two- and three-dimensional structures of β-LG and U-β-LG were changed and their surface hydrophobicity was decreased slightly after being combined with EGCG. The binding affinity between U-β-LG and EGCG was stronger than that between β-LG and EGCG, which contributed to greater conformational change of U-β-LG.
Interaction between Two Natural Antioxidants and Silver Carp Myosin
HUANG Yuan, YUE Shiyang, XIONG Shanbai, DU Hongying
2019, 40(4):  14-20.  doi:10.7506/spkx1002-6630-20171221-263
Asbtract ( 341 )   HTML ( 10)   PDF (3315KB) ( 162 )  
Related Articles | Metrics
In this investigation, the interaction between two natural antioxidants epigallocatechin gallate (EGCG), resveratrol (RE) and silver carp myosin was studied. The changes in the intermolecular interaction and microstructure of myosin were evaluated by fluorescence and circular dichroism spectroscopy. The results showed that the interaction of silver carp myosin with EGCG or RE led to fluorescence quenching of silver carp myosin in a static quenching mode. Thermodynamic analysis showed that the main driving forces for EGCG and RE binding to myosin molecules were hydrogen bonding and van der Waals force. The Stern-Volmer equation was used to obtain the binding constants and the number of binding sites at different temperatures. Circular dichroism (CD) spectroscopy and surface hydrophobicity analysis showed that EGCG and RE induced changes in myosin structure; EGCG increased the content of α-helix and decreased the surface hydrophobicity, while RE had no effect on the secondary structures of myosin and increased the surface hydrophobicity.
Construction and Characterization of Medium-Chain Triglyceride (MCT)/Zein Microcapsules with Core-Shell Structure
HUANG Xue, WANG Ying, ZHANG Hui, ZHAO Meng, FANG Yapeng
2019, 40(4):  21-27.  doi:10.7506/spkx1002-6630-20170831-368
Asbtract ( 298 )   HTML ( 10)   PDF (7467KB) ( 209 )  
Related Articles | Metrics
In this research, medium-chain triglyceride (MCT) and zein were used respectively as internal oil phase (core) and external shell to prepare MCT/zein microcapsules with core-shell structure by the anti-solvent method. Based on the macro-morphology, micro-morphology and size distribution of microcapsules, the optimum preparation conditions were determined as follows: 0.5% gum arabic (GA) as emulsifier, emulsification speed 800 r/min, zein precipitation with a mixture of 30 mL of water and 100 mL of GA solution added at a rate of 6 mL/min. Scanning electron microscopy, confocal laser scanning microscopy and laser particle size analyzer were used to characterize the structure and size properties of freeze-dried MCT/zein microcapsules. It turned out that the MCT/zein microcapsules had a typical core-shell structure with homogenous size distribution and good storage stability. In conclusion, the anti-solvent method was simple, practical and suitable for the preparation of MCT/zein microcapsules with core-shell structure for application in the encapsulation and protection of various lipophilic bioactive components.
Development of a System Combining Sodium Alginate Gelation and Rice Starch Gelatinization
ZHOU Yanqing, XIANG Zhongqi, HE Lu, ZHAO Wenjing, YANG Ying
2019, 40(4):  28-33.  doi:10.7506/spkx1002-6630-20170823-281
Asbtract ( 273 )   HTML ( 10)   PDF (2538KB) ( 201 )  
Related Articles | Metrics
In order to investigate the effect of concentration-induced sodium alginate gel on the gelatinization and retrogradation of rice starch, a system combining sodium alginate gelation and starch gelatinization was established by determining the preparation conditions of concentration-induced sodium alginate-Ca2+ gel and the addition of starch using rheological methods. water evaporation during heating triggered the transformation of sodium alginate (1 g/100 mL)-Ca2+ (3 mmol/L) system (storage modulus G’ < loss modulus G”) from a solution to a gel (G’ > G”) and the critical concentration of Ca2+ for gelling was 5.1 mmol/L. Sodium alginate-Ca2+ system containing 4–6 g/100 mL starch was converted from a liquid state (δ > 45°) to a solid-like state (δ < 45°) after water evaporation for 30 minutes with good preparation operability, which showed a closely linked network structure as seen under scanning electron microscope, accompanied by an increased G’ and a decreased flow index. These results confirmed that the alginate-Ca2+-starch system prepared under the above conditions could allow simultaneous sodium alginate gelation and starch gelatinization.
Effects of Oxidative Modification by Peroxyl Radicals on the Structural and Functional Properties of Rice Bran Protein
YOU Xiangyu, HUANG Huimin, WU Xiaojuan, WU Wei
2019, 40(4):  34-41.  doi:10.7506/spkx1002-6630-20171227-346
Asbtract ( 367 )   HTML ( 11)   PDF (3271KB) ( 107 )  
Related Articles | Metrics
Effects of oxidative modification by peroxyl radicals derived from oxidative thermal decomposition of 2,2’-azobis(2-amidinopropane) (AAPH) at different concentrations on the structural and functional properties of rice bran protein were investigated. The results indicated that as AAPH concentration increased, protein carbonyl, disulfide, and dityrosine contents of rice bran protein increased from 2.0 nmol/mg, 12.04 nmol/mg, and 84.54 to 7.09 nmol/mg, 14.69 nmol/mg, and 127.1, respectively, while free sulfhydryl content decreased from 23.97 to 15.29 nmol/mg. Oxidative modification by peroxyl radicals resulted in a decrease in α-helix and random coil content and an increase in β-sheet content. Besides, the content of amino acid side chains firstly increased, and then slightly decreased after this treatment, which also led to a decreased in surface hydrophobicity and intrinsic fluorescence intensity accompanied by a blue shift of the maximum emission wavelength. Nevertheless, oxidative modification by peroxyl radicals had no significant impact on the subunit structure of rice bran protein, but caused polypeptide chain aggregation of rice bran protein accompanied by partial rupture of the major polypeptide chain to form peptides. As AAPH concentration increased, rice bran protein solubility gradually decreased; however, water-holding capacity, oil-holding capacity, foaming activity, foaming stability, emulsifying activity, and emulsiong stability firstly increased and then decreased.
Araboxylan Solubilization and Phenolic Acid Release from Fermented Wheat Bran and Bread Dough Incorporated with It
LUO Kun, YANG Wendan, MA Zilin, ZHANG Binle, TANG Xiaojuan, LIANG Li, ZOU Qibo, ZHENG Jianxian, HUANG Weining, Omedi Jacob Ojobi
2019, 40(4):  42-48.  doi:10.7506/spkx1002-6630-20180516-243
Asbtract ( 257 )   HTML ( 10)   PDF (2291KB) ( 265 )  
Related Articles | Metrics
Fermented wheat bran was used as a functional ingredient to make high dietary fiber bread. Chemical analysis, high performance liquid chromatography and ion chromatography were used to analyze araboxylan solubilization and phenolic acid release during wheat bran fermentation and dough making and from the corresponding bread. The results indicated that the contents of water extractable araboxylan (WEAX), free phenols and ferulic acid in wheat bran increased gradually as fermentation proceeded. After fermentation, the contents of free arabinose, glucose and fructose increased; the content of WEAX improved significantly (P < 0.05) whereas the branch degree of WEAX decreased significantly (P < 0.05). Araboxylan solubilization and phenol release increased continuously during dough mixing, fermentation and baking; the content and branch degree of WEAX in fermented wheat bran enriched bread were higher. After in vitro gastrointestinal digestion, the contents and absorption rates of free phenols and ferulic acid in fermented wheat bran enriched bread were higher. Moreover, fermented wheat bran significantly promoted the antioxidant activity of bread.
Effect of Sodium Sulfite Soaking Pretreatment on Main Quality Attributes of Dehydrated Garlic Slices
ZHANG Jinglin, TAO Yang, HAN Yongbin, YE Xiaosong, YE Mingru, WU Chao, YE Shuxian
2019, 40(4):  49-55.  doi:10.7506/spkx1002-6630-20170928-412
Asbtract ( 254 )   HTML ( 11)   PDF (4027KB) ( 112 )  
Related Articles | Metrics
The browning reaction during the drying process may decrease the quality of dehydrated garlic. Therefore, in this study, the effects of sodium sulfite concentration, soaking time and temperature were investigated on the color, rehydration ratio, sulfur dioxide residue, thiosulfinate content and in vitro antioxidant activity of dehydrated garlic. It was found that sodium sulfite solution could effectively maintain the quality of dehydrated garlic. Overall, soaking time and temperature had little impact on the quality of dehydrated garlic. After being treated with sodium sulfite solution (500 mg/L) for 30 min, the garlic color was better than that of control group. The sulfur dioxide residue increased with increasing either its concentration in the soaking solution or soaking time. After soaking, the thiosulfinate content was up to 0.115 mmol/g, significantly higher than that (0.077 1 mmol/g) of the control group.
Effect of Bamboo Shoot Dietary Fiber on Thermal Gelling Properties of Pork Salt-Soluble Proteins
LI Ke, LIU Junya, FU Lei, ZHAO Yingying, ZHANG Yanyan, ZHANG Hua, ZHAO Dianbo, BAI Yanhong,
2019, 40(4):  56-61.  doi:10.7506/spkx1002-6630-20171028-336
Asbtract ( 314 )   HTML ( 14)   PDF (3079KB) ( 283 )  
Related Articles | Metrics
The objective of this study was to understand the effect of bamboo shoot dietary fiber (BSDF) on the gel properties and water-holding capacity (WHC) of pork salt-soluble protein (PSSP). The gel strength, dynamic rheological properties, WHC, water distribution and microstructure of PSSP with different amounts (0%, 1%, 2%, 3% and 4%, m/m) of added BSDF were investigated using a texture analyzer, a rotational rheometer, low field nuclear magnetic resonance (LF-NMR) and scanning electron microscopy (SEM). The results showed that the gel strength was improved significantly with increasing BSDF addition up to 3% (P < 0.05). The storage modulus (G’) and loss modulus (G”) were increased and the cooking loss and centrifugation loss were decreased significantly (P < 0.05) after adding BSDF. LF-NMR analysis showed that the addition of BSDF increased significantly the relative area percentage and decreased the relaxation time (T22) of immobilized water. SEM analysis showed that the homogeneity and compactness of PSSP gels were improved by the addition of BSDF. In conclusion, BSDF can significantly improve the gel properties of pork salt-soluble proteins, making it promising for application in meat products processing.
Comparison of Functional Properties of Macadamia (Macadamia integrifolia) Proteins Prepared by Three Different Methods Related to Their Conformation
CHEN Hao, ZHONG Junzhen, HUANG Zonglan, XIONG Yang, ZHONG Yejun, LIU Chengmei
2019, 40(4):  62-68.  doi:10.7506/spkx1002-6630-20170901-010
Asbtract ( 188 )   HTML ( 13)   PDF (2841KB) ( 294 )  
Related Articles | Metrics
Functional and conformational properties of three proteins from defatted macadamia kernel flour prepared by alkaline (MAPI), Tris-HCl (MTPI) and sodium chloride (MSPI) extraction methods were investigated. MSPI was found to have higher solubility than MAPI and MTPI in the acidic pH range, while the opposite was observed in the alkaline pH range. MSPI had an emulsifying activity index higher than that of MAPI and MTPI. The protein contents of MAPI, MTPI and MSPI were 88.9%, 80.3% and 86.1%, respectively. The three protein isolates had similar protein bands in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and similar amino acid composition except for differences in band intensities and amino acid contents. Furthermore, MSPI showed higher surface hydrophobicity and fluorescence intensity and smaller particle size than MAPI and MTPI. Field emission scanning electron microscopy (FE-SEM) results revealed that MSPI contained more spherical particles of different sizes as compared with MAPI and MTPI.
Kinetic Analysis of the Inhibitory Effect of 4-Hexylresorcinol and Ascorbic Acid on Polyphenoloxidase from Solenocera crassicornis
ZHOU Yufang, HU Jiankun, HAO Yunbin, XIANG Xingwei, YANG Huicheng, ZHENG Bin, XIAO Jinxing
2019, 40(4):  69-74.  doi:10.7506/spkx1002-6630-20171205-060
Asbtract ( 201 )   HTML ( 11)   PDF (2283KB) ( 156 )  
Related Articles | Metrics
The purpose of this study was to investigate the inhibitory effects of 4-hexylresorcinol (4-HR) and ascorbic acid (AA) on the activity of purified polyphenoloxidase (PPO) from Solenocera crassicornis. In addition, the inhibitory mechanism was elucidated through kinetic modelling with respect to the structures of the inhibitors. The results showed that both 4-HR and AA could significantly inhibit PPO activity with a half-maximal inhibitory concentration (IC50) of 0.072 and 2.02 mmol/L, respectively and provoke a lag period for the enzymatic reaction. Each of the two compounds exerted competitive inhibition on PPO activity. The kinetic analysis indicated that both 4-HR and AA could be combined with the di-copper binding active center of PPO. 4-HR could consume PPO continuously and effectively by forming a highly stable complex. In conclusion, both 4-HR and AA have been shown to be effective in controlling the enzymatic reaction rate of PPO, 4-HR being stronger than AA. This result provides theoretical support for the application of sulfur-free 4-HR-AA composite preservative in the catching and processing of shrimp.
Binding Capacity between Porcine Myosin and Aldehyde Compounds as Affected by Hydroxyl Radical
DING Anzi, ZHU Meng, QIAO Yu, WANG Lan, XIONG Guangquan, WU Wenjin, LIAO Li, LI Xin, SHI Liu
2019, 40(4):  75-80.  doi:10.7506/spkx1002-6630-20170918-250
Asbtract ( 277 )   HTML ( 9)   PDF (2993KB) ( 100 )  
Related Articles | Metrics
The effect of oxidation on protein conformation and binding capacity of porcine myosin were investigated in vitro using a FeCl3/Asc/H2O2 hydroxyl radical oxidation system. The contents of total and reactive sulfhydryl groups, secondary structure and surface hydrophobicity were detected as a function of H2O2 concentration, and the interactions between porcine myosin and four typical aldehyde compounds responsible for the flavor were investigated. It was demonstrated that the protein conformation was significantly affected by H2O2 concentration. The content of reactive sulfhydryl groups was significantly decreased while surface hydrophobicity was significantly increased with the increase of H2O2 concentration (P < 0.05). The contents of total sulfhydryl groups and α-helix were significantly decreased (P < 0.05) while the binding capacity between myosin and aldehyde compounds was significantly increased in the H2O2 concentration range from 0 to 5 mmol/L (P < 0.05). The α-helix content was significantly increased while the binding capacity of myosin was significantly decreased with increasing H2O2 concentration to 10 mmol/L (P < 0.05). The binding capacity of myosin was significantly increased again with further increasing H2O2 concentration to 20 mmol/L (P < 0.05). The main binding forces between aldehyde compounds and myosin were hydrogen bond and hydrophobic interaction. Stronger hydrogen bond and/or hydrophobic interaction led to a higher binding capacity of myosin to aldehyde compounds.
Effect of Sodium Alginate on Physicochemical Properties of Fish Skin Gelatin Films
LIU Quanjiao, LU Jianfeng, Lü Shun, JIANG Shaotong, LIN Lin
2019, 40(4):  81-86.  doi:10.7506/spkx1002-6630-20170830-358
Asbtract ( 298 )   HTML ( 12)   PDF (3054KB) ( 182 )  
Related Articles | Metrics
A series of edible composite films were prepared by blending tilapia skin gelatin with sodium alginate. The effects of sodium alginate on physicochemical properties of composite films were investigated. The results showed that tilapia skin gelatin had good film-forming property, but poor mechanical properties. The tensile strength and the elongation at break of composite films were improved compared with pure gelatin films. The maximum tensile strength of 6.6 MPa was obtained upon addition of 40% sodium alginate, an increase of 20% and 43%, respectively compared with pure gelatin film (5.5 MPa) and pure sodium alginate film (4.6 MPa); the maximum elongation at break of 120% was also achieved, an increase of 87.5% and 26.7% over pure gelatin film (64%) and pure sodium alginate film (88%), respectively. The water solubility and hygroscopicity of sodium alginate were as high as 100% and 48.7%, respectively. The water solubility of composite films was controlled below 55% and the hygroscopicity was in the range between 25% and 40%, which were greatly improved. The analysis of rheological properties and X-ray diffraction showed that sodium alginate and gelatin had good compatibility with each other, resulting in a stable composite film. Blended solutions of sodium alginate and gelatin were non-Newtonian fluid. The viscosity and thickening ability of composite films were higher than that of pure gelatin films.
Physicochemical Properties of Potato Dietary Fiber and Its Influence on the Quality of Hot Dry Noodles Made from Potato Starch
CAI Sha, SUI Yong, SHI Jianbin, HE Jianjun, CHEN Xueling, FAN Chuanhui, MEI Xin
2019, 40(4):  87-94.  doi:10.7506/spkx1002-6630-20171213-151
Asbtract ( 270 )   HTML ( 13)   PDF (2994KB) ( 176 )  
Related Articles | Metrics
This study investigated the physicochemical characteristics of potato dietary fiber, and it also examined the influence of adding different amounts of potato dietary fiber on the quality of hot dry noodles made from potato starch. The results showed that the content of insoluble dietary fiber in potato dietary fiber was 48.74%. Water-holding capacity of potato dietary fiber was 11.23 g/g, oil-holding capacity was 1.76 g/g and water swelling was 6.65 mL/g. Glucose adsorption capacity was 0.87 mmol/g and cholesterol adsorption capacity was 2.04 mg/g. Addition of potato dietary fiber improved the quality of hot dry noodles. Water absorption capacity and cooking loss rate of hot dry noodles changed irregularly with increasing addition of dietary fiber. However, shear force and tensile strength gradually decreased. Dietary fiber could delay the decomposition of starch while increasing the digestibility of proteins in noodles. In conclusion, addition of 5%–12% dietary fiber is recommended.
Antioxidant Effect of Four Spice Extracts on Porcine Myofibrillar Protein
CHEN Hongsheng, NIU Baihui, LIU Huan, LI Yanqing, ZHANG Ruihong, KONG Baohua
2019, 40(4):  95-101.  doi:10.7506/spkx1002-6630-20171204-046
Asbtract ( 267 )   HTML ( 13)   PDF (2800KB) ( 171 )  
Related Articles | Metrics
The objective of this study was to investigate the inhibitory effects of four spice extracts on the oxidation of porcine myofibrillar protein (MP) during exposure to a Fenton reaction system (FRS) for 0, 1, 3 or 5 h. The results indicated that the addition of clove extract (CE), rosmary extract (RE) or cinnamon extract (CME) significantly inhibited protein carbonyl formation (P < 0.05), but the effect of lcorice extract (LE) was not significant. Both CE and RE significantly inhibited the decrease of Ca-ATPase activity (P < 0.05); however, LE and CME had no inhibitory effect. Each of the four spice extracts strongly inhibited the increase of surface hydrophobicity. CE, RE and LE significantly inhibited the decrease of solubility (P < 0.05), while the effect of CME was not significant. The addition of each of the four spice extracts accelerated the decrease of protein sulfhydryl group content. In conclusion, CE and RE had better inhibitory effect on porcine MP oxidation.
Effect of Glycosylated Gel Enhancers on the Gel Properties of Surimi Products
LIU Jianhua, SU Qi, ZHU Minqi, LUO Yahong, DING Yuting
2019, 40(4):  102-107.  doi:10.7506/spkx1002-6630-20171220-231
Asbtract ( 750 )   HTML ( 10)   PDF (2409KB) ( 211 )  
Related Articles | Metrics
Glycosylated gel enhancers were prepared by glycosylation of egg white with a mixture of locust bean gum?and guar gum under wet-heating conditions in order to investigate their effect on the gel strength, texture, whiteness, water holding capacity and chemical forces of frozen surimi from red gurnard (Aspitrigla cuculus). The results showed that the gel strength of surimi could be significantly improved by the addition of glycosylated gel enhancers (P < 0.05). The optimum reaction conditions were found to be glycosylation at 55 ℃ for 12 hours, and the grafting degree of the glycosylated gel enhancer prepared under these conditions was (23.37 ± 1.62)%. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) confirmed the formation of protein aggregates indicating the occurrence of glycosylation. The addition of the glycosylated gel enhancer significantly increased the gel strength, whiteness and water-holding capacity of surimi. The gel strength was increased by 64%, 26.9% and 4.7%, respectively as compared to surimi without the addition of any gel enhancer, with the addition of the same amount of egg white, and with the addition of non-glycosylated gel enhancer. The results of the present study demonstrated that glycosylated gel enhancers could significantly enhance gel properties of surimi products, making it promising for applications in the surimi industry.
Effects of Wheat Germ on Physicochemical Properties and Antioxidant Activities of Chinese Traditional High-Salt Diluted Soy Sauce
ZHANG Huanhuan, GENG Yuhuan, LI Guoji, WANG Guoshu, YANG Junmei, XIE Jingming
2019, 40(4):  108-115.  doi:10.7506/spkx1002-6630-20170926-366
Asbtract ( 372 )   HTML ( 7)   PDF (3577KB) ( 72 )  
Related Articles | Metrics
The objective of this study was to investigate the effects of wheat germ on physicochemical properties and antioxidant activities of Chinese traditional high-salt diluted soy sauce made with soybean, flour and wheat germ. Antioxidant activities of the raw materials, koji and soy sauce were evaluated by Fe3+ reducing power, 1,1-diphenyl-2-picryhydrazyl (DPPH) radical scavenging, 3-ethylbenzthiazoline-6-sulphonate ABTS radical scavenging and oxygen radical absorbance capacity (ORAC) assays. Meanwhile, correlation analysis between bioactive components and antioxidant capacity of soy sauce was carried out. The results showed that wheat germ could significantly improve the contents of total nitrogen, amino nitrogen, total phenols, total flavonoids and Maillard reaction products in soy sauce (P < 0.05). The antioxidant activity of soy sauce could be improved by using wheat germ and increased with fermentation time. Besides, sample 2 (S2, soybean/flour/wheat germ ratio = 7:1:2) had the highest antioxidant activity, which was significantly higher than that of the control group (S1) (P < 0.05). The greater the amount of wheat germ added, the higher antioxidant capacity of the raw materials and koji, while the antioxidant capacity of soy sauce increased firstly and then decreased. The antioxidant activity of soy sauce was significantly positively correlated with total phenols content and Maillard reaction products (P < 0.01, r > 0.8), so that both of them could be inferred as main antioxidant substances in soy sauce. However, total flavonoid content was not highly correlated with DPPH radical scavenging capacity, ABTS radical scavenging capacity, Fe3+ reducing power and ORAC (r = 0.292, 0.446, 0.703, and 0.397), and so it could not be used to evaluate the antioxidant activity of soy sauce. In conclusion, soy sauce quality and its antioxidant activity can be improved by partial replacement of wheat germ for flour.
Effects of Oxylipins on Spore Production and Ochratoxin A Synthesis of Aspergillus ochraceus and Grain Infection
GAO Jing, LI Caiyan, LI Kexin, PENG Mengxue, LIANG Zhihong
2019, 40(4):  116-121.  doi:10.7506/spkx1002-6630-20180319-239
Asbtract ( 255 )   HTML ( 10)   PDF (3010KB) ( 285 )  
Related Articles | Metrics
This study was intended to clarify the effect of hydroxyoctadecaenoic acid (HODE) on the spore production and ochratoxin A (OTA) synthesis of Aspergillus ochraceus at different population densities. Here we measured the yields of 9S-HODE, 13S-HODE and OTA during the culture process of A. ochraceus, and we also determined the production of spores and OTA after adding 9S-hydroxy-10E,12Z-octadecadienoic acid (9S-HODE) or 13S-hydroxy-9Z,11E-octadecadienoic acid (13S-HODE) and the infection degree of grain seeds with different densities of A. ochraceus. The results showed that the ratio of 9S-HODE/13S-HODE and the yield of OTA were higher at lower inoculation density (103 spores/mL); the addition of 9S-HODE inhibited the sporulation of A. ochraceus and promoted OTA synthesis, while 13S-HODE just had the opposite effect. After infection with A. ochraceus at initial spore density of 103 and 106 spores/mL, the germination rates of peanut, soybean, corn and wheat were reduced by 29%, 21%, 17% and 14%; and by 35%, 29%, 20% and 22%, respectively. These findings indicated that the population density of A. ochraceus could affect 9S-HODE, 13S-HODE and OTA production. 9S-HODE and 13S-HODE may both be A. ochraceus quorum sensing signal molecules, which had opposite effects on A. ochraceus spore production and OTA synthesis. High population density of A. ochraceus was more infectious to grain seeds. Seeds with high levels of fat and protein content were more susceptible to A. ochraceus.
Bioinformatics Analysis of the Key Enzymes of the Hexanoic Acid Metabolic Pathway in Clostridium kluyveri Based on Comparative Genomics
XU Youqiang, SUN Baoguo, JIANG Yuefeng, LU Fazhan, ZHANG Chengnan, ZOU Wei, WANG Wenhua, YANG Ran, TENG Chao, FAN Guangsen, LI Xiuting
2019, 40(4):  122-129.  doi:10.7506/spkx1002-6630-20180413-183
Asbtract ( 265 )   HTML ( 16)   PDF (4113KB) ( 322 )  
Related Articles | Metrics
In this study, the genomic information of three Clostridium kluyveri strains (NBRC 12016, JZZ and DSM 555) were analyzed by comparative genomics with focus on the core enzymes of the hexanoic acid metabolism pathway. It was found that the metabolic pathway of hexanoic acid in NBRC 12016 was not annotated in details and there was mis-annotated information on the core enzyme of the hexanoic acid metabolic pathway in JZZ, acyl coenzyme A dehydrogenase. Bioinformatic analysis was carried out for the key enzyme thiolase (ThlA) of hexanoic acid metabolism in DSM 555. Also, we found that DSM 555 carried three copies of the ThlA gene with sequence polymorphism, which might be related to the substrate specificity of fatty acid chain elongation enzymes. The structural analysis and molecular docking indicated that the catalytic characteristics of ThlA1 contributed to the redox-switch regulatory mechanism. The key catalytic sites and the catalytic process were predicted. The above analysis will be helpful for further improving the hexanoic acid-producing ability of C. kluyveri for application in the brewing of Baijiu.
Transcriptomic Investigation of the Mechanism of the Lethal Effect of Microchip Pulse Electric Field on Pichia
ZHU Ning, YU Ning, ZHU Yue, WEI Yulong, ZHANG Jiaying, SUN Aidong
2019, 40(4):  130-137.  doi:10.7506/spkx1002-6630-20171204-027
Asbtract ( 200 )   HTML ( 8)   PDF (2940KB) ( 186 )  
Related Articles | Metrics
In this work, the effect of microchip pulse electric field (MPEF) treatment on inactivating Pichia and the underlying mechanism were investigated. A good inactivation of Pichia was achieved after 80 pulses at 400 V. The differentially expressed genes of Pichia before and after MPEF treatment were analyzed using new generation of high-throughput sequencing, and they were aligned to the gene ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. Results showed that a total of significantly differentially expressed 794 genes between the MPEF and control groups were found, 361 genes of which were up-regulated while 433 were down-regulated. After MPEF treatment, caspase activity and pyruvate transport raised significantly whereas nucleotide metabolism, ribosomal biosynthesis, protein transcription and translation, RNA polymerase activity, superoxide dismutase activity, transmembrane transport regulation, vitamin metabolism were significantly down-regulated. Furthermore, 6 differentially expressed genes were confirmed by real-time fluorescence quantitative polymerase chain reaction (q-PCR), achieving the same gene expression patterns as the transcriptome sequencing results. Destruction of cell structure, gene damage, restriction of protein synthesis and function, and changes in enzyme activities might be the main causes of death for Pichia after MPEF treatment.
Prokaryotic Expression, Purification, and Solution Conformation of Staphylococcus aureus Enterotoxin K
TIAN Wanfan, LIU Ji, ZHAO Yanying, TANG Junni
2019, 40(4):  138-145.  doi:10.7506/spkx1002-6630-20180128-385
Asbtract ( 212 )   HTML ( 7)   PDF (3085KB) ( 96 )  
Related Articles | Metrics
Staphylococcus aureus enterotoxin K (SEK) is encoded by the enterotoxin gene cluster (egc) of S. aureus. Epidemiologic survey showed that the sek gene had a relatively high prevalence in foodborne isolates of S. aureus, which indicates that SEK protein may be an important virulence factor causing staphylococcal food poisoning. In this study, the sek gene from S. aureus without N-terminal signal peptide was firstly ligated into plasmid pET-28a(+). Then, the recombinant expression plasmid pET-28a(+)-ΔNspsek was transformed into competent cells of Escherichia coli. The expression conditions were optimized and the His-ΔNspSEK fusion protein was purified to homogeneity by Ni-Sepharose affinity chromatography. The purified protein without His tag was used to assay polymerization status, thermal stability, fluorescence emission and circular dichroism spectra. The results showed that the recombinant protein ΔNspSEK was successfully expressed and purified. It could be partially degraded by heat treatment. Fluorescence emission spectra of ΔNspSEK exhibited identical tryptophan emission peaks at 278 and 295 nm, as well as excitation at 344 nm indicating that ΔNspSEK is tightly folded in nature. Circular dichroism spectra revealed that His-ΔNspSEK tagged with 6 × His sequence was rich in β-sheet (23.6%), β-turn (28%), and α-helix (29.1%). The results of this investigation will facilitate further study of the structure and function of SEK, and also provide a useful guideline to improve food processing technology and food safety.
Directed Evolution of Alginate Lyase Alg-2 Based on Error Prone PCR
LI Shu, ZHANG Wei, ZHAO Chunmei
2019, 40(4):  146-151.  doi:10.7506/spkx1002-6630-20180207-100
Asbtract ( 237 )   HTML ( 11)   PDF (2374KB) ( 231 )  
Related Articles | Metrics
In order to improve the enzymatic activity of alginate lyase Alg-2, directed evolution based on error prone PCR was carried out on the marine bacterium Tamlana sp. S12. After two rounds of error prone PCR and 96-well plate fermentation, two positive and two negative mutants were obtained with 162%, 241%, 53% and 11% higher enzymatic activity as compared with the control, respectively. According to kinetic analysis, Km value of the positive strain P2-81 was reduced by 50% while that of the negative strain N2-47 was increased by 106% as compared with the parental one, implying that the substrate affinity of the enzyme in the mutant strains is greatly increased or reduced. The results of gene sequencing and amino acid sequence analysis showed that Glu, Thr, Ser, Asp and Tyr played a positive role in the increased activity of alginate lyase whereas mutation of Lys in the conserved region had a negative effect. The role of Asp and Lys was further confirmed by directed mutations. The results of this study can be helpful to gain a deep understanding of the catalytic mechanism of alginate lyases and to provide a theoretical basis for alginate lyases reconstruction using rational design methods.
Analysis of Bacterial Diversity in Daqu and Fermented Grains for Maotai-Flavor Liquor
DAI Yijie, LI Zongjun, TIAN Zhiqiang
2019, 40(4):  152-159.  doi:10.7506/spkx1002-6630-20180228-251
Asbtract ( 307 )   HTML ( 11)   PDF (2998KB) ( 782 )  
Related Articles | Metrics
The Illumina HiSeq 2500 sequencing system was used to perform a comprehensive analysis of the dynamics of bacterial community structure during the high-temperature Daqu making process and the fermentation process of Maotai-flavor liquor. The experimental results showed that the population and community structure of the microflora were diverse for both processes and the bacterial species compositions were basically the same. The dominant bacterial phyla were Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetes for both process. The ecological environment was different between the two processes, resulting in variability in the dominant bacterial community composition. In addition, the bacterial community regularly changed during the fermentation process of Maotai-flavor liquor. The change in the bacterial community in Daqu was related to storage time. The predominant genera in Daqu were Clostridium sensu stricto 1, Escherichia-Shigella, Lactobacillus, Streptococcus, Actinobacillus, Bifidobacterium, Peptoclostridium, Mycoplasma and Citrobacter. The abundance of Escherichia-Shigella, Actinobacillus, Bifidobacterium and Citrobacter increased with increasing storage time, the abundance of Clostridium sensu stricto 1 and Mycoplasma first increased and then decreased, the abundance of Lactobacillus and Peptoclostridium did not obviously change, and the abundance of Streptococcus showed a downward tendency. The bacterial community in fermented grains changed from pit fermentation to high-temperature stacking fermentation. The dominant?microorganisms during the liquor fermentation process were Escherichia-Shigella, Lactobacillus, Clostridium sensu stricto 1, Streptococcus, Actinobacillus, Bifidobacterium and Alternaria. The numbers of Escherichia-Shigella and Lactobacillus, having higher relative abundance, increased during the early fermentation period, then decreased from the second round until reaching a minimum at the high-temperature stacking fermentation stage of the third round, and finally increased gradually again during the late fermentation stage. The abundance of Clostridium sensu stricto 1 and Streptococcus decreased first and then increased. Taken together, our results revealed that the dominant genera during the high-temperature Daqu making process and the liquor fermentation process were basically the same, which indicates that Daqu is the microbial source for the fermentation of fermented?grains. In addition, the growth tolerance of bacteria was strong. As time went on, the variations of temperature and water reached an equilibrium, and the bacterial community was gradually dominated by a single species, which is more conducive for the brewing of Maotai-flavor liquor.
Enzymatic Characterization of Recombinant α-L-Rhamnosidase from Pediococcus acidilactici AS1.2696
GUO Shuangshuang, ZHENG Fangfang, KE Congxue, WANG Zilong, WEI Yutuo, HUANG Ribo, DU Liqin
2019, 40(4):  160-169.  doi:10.7506/spkx1002-6630-20180104-044
Asbtract ( 314 )   HTML ( 9)   PDF (4006KB) ( 139 )  
Related Articles | Metrics
The aim of this study was to evaluate the enzymatic properties of recombinant α-L-rhamnosidases PRHA2 and PRHA3 from Pediococcus acidilactici AS1.2696. The whole genome sequence of P. acidilactici AS1.2696 was analyzed and the two genes encoding α-L-rhamnosidase were amplified by PCR and ligated into expression vector pSE, yielding recombinant plasmids pSE-prha2 and pSE-prha3. The recombinant plasmids were separately transformed and expressed in E.coli XL-blue. The recombinant proteins PRHA2 and PRHA3 were purified by Ni-NTA affinity column chromatography and their enzymatic characteristics were investigated in detail. The results showed the optimal pH and temperature of PRHA2 were 5.0 and 60 ℃, respectively. Its Km and Vmax values were (3.039 ± 0.581) mmol/L and (2.032 ± 0.186) μmol/(min·mg), respectively. The optimal pH and temperature of PRHA3 were 5.5 and 45 ℃, and its Km and Vmax values were (2.797 ± 0.132) mmol/L and (113.35 ± 1.485) μmol/(min·mg), respectively. PRHA2 and PRHA3 could not only hydrolyze the artificial substrate p-nitrophenyl-α-L-rhamnopyranoside (pNPR) but could also hydrolyze the α-1,6 glucosidic linkages of the natural substrates hesperidin and rutin. PRHA2 had hydrolytic activity on 4-nitrophenyl-β-L-arabinoside (pNPA). PRHA3 weakly hydrolyzed the glucosidic linkages at the C-7 position of icariin, icariside I, epimedin A, epimedin B and epimedin C. In addition, PRHA3 could hydrolyze the outer rhamnosidic linkage to the C-3 position of epimedin C through α-Rha(2→1)α-Rha, leading to potential applications in the food and medicinal fields.
Inhibitory Effect of Pichia guilliermondii Y35-1 against Postharvest Anthracnose Infection in Loquat Fruit and Its Effect on Quality Preservation
ZHAO Luning, ZHOU Qiuyang, YANG Huihui, ZHENG Hongru, WEN Xinyu, SUN Weihong
2019, 40(4):  170-177.  doi:10.7506/spkx1002-6630-20171226-329
Asbtract ( 261 )   HTML ( 11)   PDF (3078KB) ( 106 )  
Related Articles | Metrics
The antagonistic yeast Pichia guilliermondii Y35-1, isolated from loquat fruit was evaluated for its inhibitory activity against postharvest anthracnose infection in loquat fruit. Also, the application of liquid and solid-state cultures of strain Y35-1 as preservatives for loquat fruit was investigated. The results showed that the P. guilliermondii Y35-1 could inhibit spore germination in Colletotrichum gloeosporioides as an anthracnose pathogen for loquat fruit; Y35-1 could inhibit parasitize its hyphae and inhibit its growth. Non-contact culture confrontation test showed that strain Y35-1 could significantly inhibit the expansion and growth of C. gloeosporioide. Both the liquid biocontrol agent and freeze-dried powder of Y35-1 could significantly inhibit decay incidence of loquat fruit during the postharvest storage period. The decay index was only 2.25% and 3.60%, respectively, at day 20 of storage. And these two biocontrol agents played a positive role in the maintenance of fruit firmness, mass loss, soluble solids content, cell membrane permeability in pericarp, total sugar content, total acid content and vitamin C content of loquat fruit. The best storage temperature was 4 ℃ for the liquid biocontrol agent and ?20 ℃ for the freeze-dried powder. Trehalose played a positive role in maintaining the viability and biocontrol efficacy of the freeze-dried powder of Y35-1. In summary, these results showed that Y35-1 had an obvious inhibitory effect on postharvest anthracnose infection in loquat fruit, and both biocontrol agents of Y35-1 could preserve the postharvest quality of loquat fruit.
Nattokinase Production and Metabolic Characteristics during Submerged Fermentation of Buckwheat Using Bacillus subtilis natto
ZHAO Mouming, ZOU Ying, LIN Lianzhu, WU Jian
2019, 40(4):  178-185.  doi:10.7506/spkx1002-6630-20180120-285
Asbtract ( 271 )   HTML ( 7)   PDF (3974KB) ( 189 )  
Related Articles | Metrics
The submerged fermentation conditions of buckwheat for nattokinase production in shake flasks and a 2.5 L fermentor using Bacillus subtilis natto were optimized. Changes in bacterial growth and the metabolism of nutrients (nattokinase, soluble protein, reducing sugar, phenolics and antioxidants) during fermentation using soybean protein isolate hydrolysate and commercial soybean peptone as a supplementary nitrogen source were comparatively studied. The optimized fermentation conditions in a 2.5 L fermentor were obtained as follows: 6 h of buckwheat soaking, pulping at a solid-to-water ratio of 1:10 (g/mL), addition of 0.4% α-amylase, heating for 40 min at 90 ℃, supplementation of 12 h hydrolyzed soybean protein isolate (SPI) with a commercial protease preparation (NS37071), pH adjustment to 7.0, inoculum size 3%, ventilation rate 3.5 L/min, stirring speed 300 r/min, medium volume 1.2 L, and 36 h fermentation. Supplementation of SPI hydrolysate prolonged the logarithmic growth phase and led to increased consumption of reducing sugar and soluble protein as compared with soybean peptone. Residual reducing sugar and soluble protein tended to level off at 36 h of fermentation with supplementation of SPI hydrolysate, and simultaneously the maximum nattokinase activity was obtained. In addition, the specific dissolution rate of phenolics and the specific formation rate of antioxidants reached a maximum at 12 and 6 h, respectively. The nattokinase activity of the fermentation products obtained under the optimized conditions was 152.5 FU/mL, which were rich in phenolics (0.109 mg/mL) and antioxidants (27.43 μmol/mL).
Changes in Gel Properties and Formation Mechanism of Giant Squid Surimi (Dosidicus gigas) during Fermentation by Lactobacillus coryneformis
CHEN Xiaoqian, WU Zufang, WENG Peifang
2019, 40(4):  186-191.  doi:10.7506/spkx1002-6630-20180122-289
Asbtract ( 208 )   HTML ( 7)   PDF (2297KB) ( 198 )  
Related Articles | Metrics
The gel properties of giant squid surimi (Dosidicus gigas) fermented by Lactobacillus coryniformis Lz153 were determined by a texture analyzer. Changes in chemical forces including ionic bond, hydrogen bond, hydrophobic interaction, disulfide bond and non-disulfide covalent bond were examined during the gel formation process, and changes in myofibrillar protein were monitored by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The aim of this study was to determine the mechanism of gel formation. The results showed that the best gel characteristics were achieved between 24 and 36 h of fermentation. Ionic bond content decreased gradually during the fermentation process, and the contents of hydrogen bond and hydrophobic force reached the maximum values at 36 and 30 h, respectively. The contents of disulfide bond and non-disulfide covalent bond increased with the prolongation of fermentation time. Hydrogen bond, hydrophobic force, disulfide bond and non-disulfide covalent bond were the main driving forces for gel formation. SDS-PAGE showed that the myosin heavy chain and actin were degraded gradually during fermentation. Meanwhile, a new salt-soluble protein band within the range of 100–135 kDa appeared at 24 h and was gradually degraded till 48 h. Our results provide a basis for the production of lactic acid bacteria fermented surimi from giant squid muscle.
Component Analysis
Discrimination of Different Characteristics of Chestnut-like Green Tea Based on Gas Chromatography-Mass Spectrometry and Multivariate Statistical Data Analysis
YIN Hongxu, YANG Yanqin, YAO Yuefeng, ZHANG Mingming, WANG Jiaqin, JIANG Yongwen, YUAN Haibo
2019, 40(4):  192-198.  doi:10.7506/spkx1002-6630-20180120-276
Asbtract ( 289 )   HTML ( 13)   PDF (2563KB) ( 374 )  
Related Articles | Metrics
The volatile constitutions of 18 green tea samples with three different types of characteristic chestnut-like aroma were characterized based on gas chromatography-mass spectrometry (GC-MS) combined with multivariate statistical data analysis including principal component analysis (PCA), hierarchical cluster analysis (HCA) and partial least squares-discriminant analysis (PLS-DA). The results showed that PCA, PLS-DA and HCA could achieve good differentiation of three chestnut flavored green teas. In the PLS-DA analysis, 18 chestnut-like green tea samples were well separated according to their aroma characteristics, and the well-explained variance (R2Y =0.843) and cross-validated predictive capability (Q2 = 0.694) indicated the model’s good feasibility. In the HCA analysis, three kinds of chestnut fragrant green tea could be clearly divided into three categories at a distance of 12, of which the chestnut-like and tender chestnut-like tea samples were closer, matching the results of sensory evaluation. In addition, 38 volatile components were identified based on variable importance in projection (VIP) score > 1, which were responsible for the discrimination of green teas with three different flavor characteristics.
Sensomics Characterization of the Key Odorants in Jujube Brandy
REN Xiaoyu, SUO Ran, PEI Xiaojing, WANG Jie, WANG Juntao, ZHANG Shaoyun, XIE Lina
2019, 40(4):  199-205.  doi:10.7506/spkx1002-6630-20171106-060
Asbtract ( 373 )   HTML ( 8)   PDF (1951KB) ( 152 )  
Related Articles | Metrics
Headspace solid phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) was applied to identify and analyze the volatile aroma compounds of jujube brandy. First, the aroma components were determined by gas chromatography-olfactometry (GC-O), time-intensity method (OSME) and aroma extract dilution analysis (AEDA). The odor activity value (OAV) was used to select the characteristic aroma components. Finally, the characteristic aroma components of jujube brandy were determined by aroma recombination and omission/addition tests. The results showed that a total of 63 aroma components were identified in jujube brandy, and 21 of these were screened out as important aroma compounds by quantitative analysis based on their OAV. The aroma of jujube brandy was successfully simulated by the recombinant test using these selected compounds. The aroma omission test further confirmed that ethyl octanoate was the characteristic aroma substance in jujube brandy, and that ethyl octanoate and ethyl valerate butanol 3-methylbutanol pentanoic acid played an important role in the overall aroma.
Analysis of Flavor Characteristics of Stewed Beef from Different Carcass Parts
SONG Ze, XU Xiaodong, XU Rui, JIA Qian, FENG Tao, SONG Shiqing
2019, 40(4):  206-214.  doi:10.7506/spkx1002-6630-20180104-050
Asbtract ( 390 )   HTML ( 18)   PDF (2532KB) ( 261 )  
Related Articles | Metrics
Purpose: To gain a deep understanding of the flavor characteristics of stewed beef from different parts of the carcass (high rib, rump, shin, flank and chuck tender). Methods: Sensory evaluation, electronic tongue, fast GC electronic nose (E-nose) and simultaneous distillation extraction combined with gas chromatography-mass spectrometry (SDE-GC-MS) were used to analyze quantitatively and qualitatively the composition of flavor compounds. Results: Sensory evaluation revealed that stewed flank had a strong beefy and fatty aroma and a fleshy taste with the best stewed mouthfeel. The results of electronic tongue analysis showed that the taste of all samples was significantly different. The fast GC electronic nose revealed significant differences in radar images among the five beef cuts. Meanwhile, a total of 98 volatile compounds were detected by SDE-GC-MS. Among these, aldehydes were the most abundant, followed by alcohols and ketones. There were 44, 50, 20, 31, and 47 compounds detected in stewed shin, chuck tender, flank, rump and high rib, respectively. Conclusion: The results from this study provide a theoretical basis for the establishment of stewed beef flavor database.
Effect of Fermentation Methods on Theabrownin Composition of Pu-erh Tea
WU Enkai, WANG Qiuping, GONG Jiashun, ZHANG Tingting
2019, 40(4):  215-221.  doi:10.7506/spkx1002-6630-20171201-006
Asbtract ( 409 )   HTML ( 19)   PDF (2369KB) ( 185 )  
Related Articles | Metrics
Theabrownins (TB) were extracted from instant Pu-erh tea made by submerged fermentation using Aspergillus tubingensis and from ripened Pu-erh made by conventional solid-state fermentation. Curie point pyrolysis gas chromatography-mass spectrometry (CP-Py-GC-MS) and colorimetry were used to analyze the TB composition of Pu-erh tea. Results showed that the contents of theabrownins, total polyphenols, total flavonoids, total catechins and amino acids in instant Pu-erh tea were significantly higher than those in ripened Pu-erh (P < 0.05), while the contents of total carbohydrate, polysaccharides and theaflavins were significantly lower in instant Pu-erh tea (P < 0.05). On the other hand, no significant difference in protein content between the two teas was observed (P > 0.05). At different Curie point pyrolysis temperatures (380 and 600 ℃), 12 and 9 compounds were found to be common to the pyrolysis products of TB from both tea samples. The majority of these pyrolysis products were phenolic compounds with caffeine being the most predominant.
Effect of Key Processing Steps on Formation of Volatile Flavor Components in Steamed Pork with Rice
ZHANG Zheqi, ZANG Mingwu, ZHANG Kaihua, LI Dan, WANG Shouwei, LI Xiaoman, XUE Dandan
2019, 40(4):  222-228.  doi:10.7506/spkx1002-6630-20180727-324
Asbtract ( 223 )   HTML ( 34)   PDF (2002KB) ( 148 )  
Related Articles | Metrics
The volatile flavor components in steamed pork with rice during various processing stages were extracted and identified by dynamic headspace sampling (DHS) combined with gas chromatography-mass spectrometry-olfactometry (GC-MS-O). A total of 79 volatile compounds were identified from raw marinated (intermediate 1), cooked unmarinated (intermediate 2) and cooked marinated streaky pork (intermediate 3) and the finished product. Intermediate 1 showed the highest abundance (2 044.35 g/kg) but the greatest diversity (69) of volatile compounds. Compared with intermediate 2 (2 706.15 g/kg), the amount of volatile flavor substances in intermediate 3 and the product was increased (2 869.79 and 2 900.12 g/kg); however, there was a significant difference in volatile flavor composition. The contents of esters, alcohols, acids and phenols in intermediate 2 were higher than those in three other groups, and the content of aldehydes was lower in the three cooked samples as compared to the raw meat. Principal component analysis (PCA) showed that all four groups were clearly separated; for intermediate 2 and 3, the cumulative variance contribution rate of the first principal component (PC1) was larger, but no significant difference in the cumulative variance contribution rate of the second principal component (PC2) was observed between the two groups. The finished product showed the lowest cumulative variance contribution rate of PC1, which did not significantly differ compared with the other groups, but exhibited a greater cumulative variance contribution rate of PC2, suggesting a great difference in the main flavor composition between the finished product and the intermediates. In general, rice flour has a great influence on the flavor of the product, mainly by inhibiting the generation and release of flavor substances.
Differences in Free Amino Acid Composition of Fruits of Common Olive and Sweet Olive and Their Glutamine Metabolism Characteristics
PENG Zhenfen, YE Qinghua, WANG Wei, XIE Qian, CHEN Qingxi
2019, 40(4):  229-236.  doi:10.7506/spkx1002-6630-20171228-354
Asbtract ( 296 )   HTML ( 10)   PDF (3169KB) ( 80 )  
Related Articles | Metrics
Using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) combined with multivariate statistical analysis, fruits of the common olive ‘Changying’ and the sweet olive ‘Qinglan 1 hao’ were compared for differences in their free amino acid composition. Meanwhile, glutamine metabolism characteristics of the two olive varieties were analyzed. The aim was to provide the basis for understanding the contribution of amino acids to the differential flavor between common olive and sweet olive. By principal component analysis (PCA), partial least squares projection to latent structures discriminant analysis (PLS-DA) and significance analysis, the differential free amino acids between the two varieties were determined and correlation analysis was also conducted. The results showed that there was a difference in free amino acid composition between common olive and sweet olive with respect to the sweet amino acids serine (Ser) and glutamine (Gln) as well as umami glutamate (Glu). The three amino acids were all more abundant in ‘Qinglan 1 hao’ and made greater contribution to the flavor of this variety. Their average contents were in the descending order: Glu > Gln > Ser for both varieties, and their differences between the two varieties were in descending order: Ser > Gln > Glu, overall suggesting that Gln was a more important amino acid. The Gln content of ‘Changying’ was significantly negatively correlated with asparagine synthetase (AS) activity (P < 0.05) and soluble sugar with correlation coefficient (r) of ?0.792 and ?0.711, respectively, whereas no significant correlation with sucrose or reducing sugar was found (P > 0.05). The Gln content of ‘Qinglan 1 hao’ was not significantly correlated with AS activity, while it was highly significantly correlated with sucrose (P < 0.05, r = 0.953) and soluble sugar (P < 0.05, r = 0.791) and negatively correlated with reducing sugar (P < 0.05, r = ?0.780). Hence, the correlations of Gln content with the metabolic enzyme activities and sugars differed between both varieties. In conclusion, free amino acids made different contributions to the flavor of common olive and sweet olive. Notably, Gln could affect the flavor of olive by regulating the activity of AS and sugar metabolism.
Changes of Fatty Acid Profile of Breast Milk during Different Lactation Periods and Factors Influencing Polyunsaturated Fatty Acid Content
ZHONG Yubei, CHEN Lijun, ZHAO Junying, DONG Xueyan, LI Jufang, LIU Bin, CHANG Lanlan, CHEN Shuxing, JIANG Tiemin,
2019, 40(4):  237-243.  doi:10.7506/spkx1002-6630-20171003-005
Asbtract ( 309 )   HTML ( 15)   PDF (2365KB) ( 207 )  
Related Articles | Metrics
Gas chromatography-mass spectrometry (GC-MS) was used to determine the dynamic changes of fatty acids in breast milk during different lactation periods. The effects of maternal blood type, childbearing age, pre-pregnancy body mass index (BMI), mode of delivery, gestational age, infant sex and parity on the contents of polyunsaturated fatty acids (PUFAs) directly related to infant growth and development such as linoleic acid (LA), α-linolenic acid (ALA), arachidonic acid (AA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) in mature milk were analyzed. The results showed that the contents of saturated fatty acids (SFAs) in colostrum and mature milk were significantly different (P < 0.05). The content of monounsaturated fatty acid (MUFA) decreased gradually with the prolongation of lactation period, but the difference was not significant (P > 0.05). There was no significant difference in the content of total PUFAs during different lactation stages (P > 0.05). The contents of AA and DHA decreased gradually with the prolongation of lactation; they were not significantly different between colostrum and transitional milk (P > 0.05), but were significantly higher than those in mature milk (P < 0.05). LA content in breast milk was relate to infant sex, ALA content was related to pre-pregnancy BMI, the contents of AA and EPA were related to maternal blood type, the content of DHA was related to pre-pregnancy BMI and maternal blood type; all these correlations were statistically significant (P < 0.05).
Comparison of Fruit Nutritional Traits of Major Cultivars of Chinese Cherry (Prunus pseudocerasus Lindl.)
JIA Chaoshuang, SHAN Changsong, ZHOU Tao, LI Xiangyang, WU Peng, SUN Yugang
2019, 40(4):  244-250.  doi:10.7506/spkx1002-6630-20171220-240
Asbtract ( 428 )   HTML ( 13)   PDF (2417KB) ( 358 )  
Related Articles | Metrics
The main fruit nutritional traits (single fruit mass, pH, and the contents of total sugar, reducing sugar, total acid, vitamin C and anthocyanin) of 30 cultivars of Chinese cherry (Prunus pseudocerasus Lindl.) were measured and analyzed by principal component analysis (PCA) and cluster analysis (CA) in order to select superior cultivars. The results showed significant differences in fruit nutritional traits among different cultivars of Chinese cherry. The coefficients of variation (CV) of single fruit mass and the contents of total sugar, reducing sugar, and vitamin C (VC) were larger than those of other indices, and a simple correlation was observed between some nutritional indices. PCA analysis showed that the first principal component 1 (PC1) and the second principal component (PC2) presented a characteristic value greater than 1, and their cumulative variance contribution rate was 67.718%, suggesting that both PCs could reflect most of the information about the original variables. Cluster analysis divided the 30 cultivars into five types, which differed greatly in fruit nutritional traits. In general, our results showed that the cultivars Red Honey, 13-33 and Qin-Lin had the best quality, and they could be utilized directly or modified for better fruit quality.
Effects of Seven Wild Wine Yeast Strains on the Aroma Compounds of ‘Guipu 3’ Dry White Wines
YU Huan, GUAN Jingxi, YANG Ying, HUANG Xiaoyun, CHENG Guo, XIE Taili, XIE Linjun
2019, 40(4):  251-258.  doi:10.7506/spkx1002-6630-20180207-097
Asbtract ( 201 )   HTML ( 8)   PDF (2169KB) ( 131 )  
Related Articles | Metrics
Seven wine yeast strains isolated in the Vitis quinquangularis Rehd-producing area of Guangxi, Hanseniaspora thailandica MSF1-4, MG4, MG6 and MSF6-2, Issatchenkia terricola MG3-1, Saccharomyas cerevisiae MSF8-1 and Pichia pastoris MG1, as well as commercial yeast K1, were separately used in dry white wine fermentation from ‘Guipu 3’ grape must. The physicochemical properties and flavor compounds of the wines were evaluated. The results indicated that the physicochemical properties of all the seven isolates met the national standard requirements. A total of 68 volatile aroma compounds were identified and in total the experimental wines contained more volatile aroma compounds than the control K1. The proportion of ethyl caprylate to the total amount of ethyl esters was as high as 46.05% for the experimental wines and only 7.12% for the control. The characteristic aroma compounds of MG3-1, MG1 and MSF6-2 fermented wines were phenethyl acetate, 1-nonanal, terpinen-4-ol, linalool, 1-octanol and decyl alcohol. The characteristic aroma compounds of MG6 fermented wine were isopentyl hexanoate and citronellol. The characteristic aroma compounds of MSF8-1, K1 and MG4 fermented wines were ethyl acetate. The characteristic aroma compounds of MSF1-4 fermented wine were rose oxide, ethyl laurate, octanoic acid, decanoic acid, ethyl caprate, ethyl caprylate, ethyl butyrate, hexyl acetate, ethyl caproate and methyl octanoate. The highest similarity in aroma characteristics was observed between K1 and MG4 fermented wines, while the difference between MG6 and MSF1-4 fermented wines was maximal. Our results suggest that all seven wild yeast strains can produce ethyl caprylate, and MG1 and MSF1-4 are the strongest producer of ethyl caprylate and thus deserve further research and development.
Correlation and Path Analysis between Fruit Quality and Mineral Elements of 6 Varieties of Korla Fragrant Pear
WEI Jie, JIANG Yuan, LIN Caixia, SHI Lei, LUO Taofeng, LI Yongfeng
2019, 40(4):  259-265.  doi:10.7506/spkx1002-6630-20180306-070
Asbtract ( 301 )   HTML ( 15)   PDF (2162KB) ( 241 )  
Related Articles | Metrics
In order to screen out the major mineral elements that affect fruit quality for the purpose of providing a theoretical basis for rational fertilization to improve fruit quality and economic benefits in pear orchards, the correlation and path coefficients between mineral elements and fruit quality indicators in six Korla fragrant pear varieties were computed by using correlation and path analysis. The results showed that there were significant differences in fruit quality traits and mineral elements contents between the varieties. The coefficient of variation (CV) of stone cell content was larger than that of other quality indices, while the CV of soluble solid content was smaller. The CV of P content was larger than that of other mineral elements, and the CV of Mg content was smaller. Correlation analysis indicated that there was a simple correlation between some fruit quality traits and some mineral elements. Path analysis further demonstrated that Ca had the maximum positive direct effects on single fruit mass, firmness and soluble solid content, N showed the maximum positive direct effects on soluble sugar, titratable acid and vitamin C content, P had the maximum positive direct effects on the ratio of soluble sugar to titratable acid and stone cell content. On the other hand, Cu had the maximum negative direct effects on fruit firmness, soluble solid and stone cell content, Fe had the maximum negative direct effects on titratable acid and vitamin C content, Zn had the maximum negative direct effects on soluble sugar content, and N had the maximum negative direct effects on single fruit mass and the ratio of soluble sugar to titratable acid. Reasonable proportions of various mineral nutrient elements in fertilizers are required for better production of pear.
Analysis of Monosaccharide Composition of Polysaccharides from Okra by Pre-column Derivatization High Performance Liquid Chromatography
ZHOU Yanqiang, WU Guangbin, CHEN Fahe
2019, 40(4):  266-271.  doi:10.7506/spkx1002-6630-20180130-426
Asbtract ( 880 )   HTML ( 24)   PDF (2056KB) ( 407 )  
Related Articles | Metrics
A simple and sensitive high performance liquid chromatography (HPLC) method for simultaneous determination of eight monosaccharides in okra polysaccharides by pre-column derivatization with 1-phenyl-3-menthy-5-pyrazolone (PMP) was developed. The monosaccharides were separated on an InfinityLab Poroahell C18 column (4.6 mm × 150 mm, 4 μm), maintained at 25 ℃, using phosphate buffer (0.1 mol/L, pH 6.85): acetonitrile mixture (82:18, V/V) as a mobile phase at a flow rate of 1.0 mL/min. The wavelength of the UV detector was set at 250 nm. Under optimal conditions, the method had wide linear ranges for all monosaccharides, with correlation coefficients above 0.999. The detection limits (LODs) were in the range of 0.13–0.45 mg/kg and the limits of quantitation (LOQs) were in the range of 0.43–1.49 mg/kg. The spiked recoveries ranged from 94.51% to 106.44%, with relative standard deviations (RSDs) less than 5%. The method proved to be simple, rapid and accurate, and could meet the analysis of the monosaccharide composition of okra polysaccharides. This method was successfully applied to analyze the monosaccharide composition of three different polysaccharides from sequential solvent extraction of okra with hot sodium acetate buffer, sodium oxalate-EDTA·2Na-sodium acetate buffer and sodium hydroxide-sodium borohydride solution. The first polysaccharide was composed of mannose, rhamnose, glucuronic acid, galacturonic acid, glucose, galactose and arabinose at a molar ratio of 0.1:7.0:0.4:5.8:0.9:14.6:1.5, the second one was composed of rhamnose, galacturonic acid, galactose and arabinose at a molar ratio of 4.7:61.8:9.6:5.3, and the third one was composed of mannose, rhamnose, galacturonic acid, glucose, galactose and arabinose at a ratio of 9.5:5.4:1.3:10.8:2.4:7.6.
Effects of Different Dietary Sugars for Honeybees on Metabolite Composition in Royal Jelly Investigated by GC-QTOF-MS-Based Metabonomics
ZHANG Wenwen, PANG Qian, WANG Kang, CHEN Xiaomei, FAN Rongli, CHEN Guohong, JI Ting
2019, 40(4):  272-278.  doi:10.7506/spkx1002-6630-20171026-293
Asbtract ( 266 )   HTML ( 13)   PDF (2671KB) ( 297 )  
Related Articles | Metrics
This study aimed to examine the effects of different dietary sugars for honeybees on the quality of royal jelly. Metabonomics analysis of royal jelly produced by honeybees fed three different sugars, white sugar, honey and high fructose syrup was conducted using gas chromatography-quadrupole time-of-flight mass spectrometry (GC-QTOF-MS). The results showed that the contents of proline, isoleucine, valine, lactose, hydroxyproline, capric acid and L-sulfanalanine were significantly higher in the honey-fed group compared with the sugar-fed group (P < 0.05). The contents of sucrose and maltose were significantly higher (P < 0.05), whereas the contents of glycerol, cellobiose, isoleucine, xylose, hydroxyproline, lactose and L-sulfaalanine were significantly lower in high fructose syrup group compared with the honey-fed group (P < 0.05). The contents of palmitic acid, maltose, threonine and galactose were significantly higher in the high fructose syrup-fed group (P < 0.05), while the contents of cellobiose, pine disaccharides, xylose, lactose and erythritol were significantly lower in the high fructose syrup-fed group compared with the sugar-fed group (P < 0.05). These differences may affect the growth and development of honeybee larvae and also have an impact on royal jelly quality. The results of this study provide a theoretical basis for the selection of appropriate dietary sugars for honeybees and for further research on the factors that affect the composition of royal jelly.
Processing Technology
Preparing Zinc Enriched Rice by Extruding Broken Rice
WANG Yuqi, ZHANG Ruchun, ZHANG Xin, YU Changhua, HAN Fujiang, ZHANG Hongwei, YU Dianyu
2019, 40(4):  279-285.  doi:10.7506/spkx1002-6630-20180429-378
Asbtract ( 200 )   HTML ( 12)   PDF (3508KB) ( 114 )  
Related Articles | Metrics
This investigation studied the preparation of zinc-enriched rice from broken rice by extrusion using zinc lactate as zinc fortifier. Broken rice was crushed to pass through 100 mesh and the amount of zinc lactate was 2.0%. Response surface methodology was used to investigate the effects of feed moisture, screw speed, and barrel temperature on the texture characteristics of zinc-enriched rice. Under the optimized conditions: feed moisture of 20%, screw speed of 80 r/min, and barrel temperature of 100 ℃, the hardness of zinc-enriched rice was 1 339.05 g, adhesiveness was 0.75 mJ, elasticity was 0.79 mm, chewiness was 967.42 mJ, and zinc content was 450.0 mg/kg. X-ray diffraction showed that the crystallinity of starch granules in fortified rice was significantly lower than that of glutinous rice. Scanning electron microscopy showed that the zinc-fortified rice starch granules were aggregated with an irregular scale-like surface. The gelatinization temperature decreased from 77.9 to 56.2 ℃, and after enzymatic hydrolysis, the amount of reducing sugar increased by more than 23.0%, which was beneficial to the enzymatic hydrolysis of rice starch granules. The taste and appearance of cooked glutinous rice with zinc-enriched rice added at a ratio of 1:10 were good, and the zinc content was 48.0 mg/kg.
Extraction Optimization by Response Surface Methodology and HPLC Analysis of Organic Acids from Pixian Broad Bean Paste
YU Xiaoyu, FANG Jiaxing, XIANG Qin, CHE Zhenming, LIU Ping, LIN Hongbin
2019, 40(4):  286-291.  doi:10.7506/spkx1002-6630-20180125-320
Asbtract ( 274 )   HTML ( 16)   PDF (2878KB) ( 101 )  
Related Articles | Metrics
The extraction of organic acid from Pixian broad bean paste was optimized by one-factor-at-a-time method and response surface methodology based on central composite design. The optimum extraction conditions were obtained as follows: ethanol concentration 72%, solid-to-solvent ratio 1:21 (g/mL), and ultrasound irradiation for 37 min. The organic acids in six different samples were qualitatively and quantitatively analyzed by high performance liquid chromatography (HPLC). Citric acid was found to be the most abundant organic acid in Pixian broad bean paste, in the range of 4.0–6.5 mg/g, followed by malic acid (2.1–3.6 mg/g) and lactic acid (1.7–2.4 mg/g).
Processing of Flavored Meat Analogues by High-Moisture Extrusion
XUN Chongrong, XUE Hongfei, LIU Baohua, JIANG Lianzhou, XIE Fengying, LI Yang, SUI Xiaonan, WANG Zhongjiang
2019, 40(4):  292-298.  doi:10.7506/spkx1002-6630-20180119-273
Asbtract ( 379 )   HTML ( 10)   PDF (2651KB) ( 284 )  
Related Articles | Metrics
In this study, we prepared flavored meat analogues from a mixture of soybean protein isolate and wheat gluten with added natural flavor-active oil powder as a flavoring agent by high-moisture extrusion. The volatile flavor compounds of meat analogues were identified and quantified by solid phase microextraction coupled with gas chromatography-mass spectrometry (SPME-GC-MS). The effect of wheat gluten content, moisture content, extrusion temperature and screw speed on the flavor retention of meat analogues was investigated. The optimum processing parameters were established as follows: wheat gluten content 20%, extrusion temperature 150 ℃, and screw speed 300 r/min using a combination of one-factor-at-a-time method and response surface methodology. Under these conditions, the retention rate of volatile flavor compounds was 44.07%, which decreased with the increase of moisture content. The water content of the raw material was determined as 60% in order not to affect the chewiness of meat analogues.
Safety Detection
Isolation and Identification of Bovine-Derived Non-O157 Escherichia coli Strains
YU Jinlong, DONG Chen, WANG Xianjing, JI Saisai, FU Wenjing, HU Jie, JIANG Yun
2019, 40(4):  299-304.  doi:10.7506/spkx1002-6630-20180103-041
Asbtract ( 203 )   HTML ( 8)   PDF (2128KB) ( 95 )  
Related Articles | Metrics
Objectives: The aims of this study were to isolate and identify non-O157 Escherichia coli strains from bovine fecal and beef samples and to detect the virulence genes of the isolates, in order to understand the contamination status of non-O157 E. coli. Methods: After selective enrichment of beef and fecal samples by the USDA method with slight modifications, multiplex PCR was used as a prescreening method to determine the O-groups (O157, O121, O111, O103 and O26). The enriched positive sample was streaked for isolation and purification on chromogenic rainbow agar, and tested for the O-groups. The flagellar antigens were identified by PCR-restriction fragment length polymorphism (PCR-RFLP) and the positive isolates were further verified by means of serum agglutination test. The virulence genes (stx1, stx2, eae, and hly) of the positive isolates were detected by PCR. Results: A total of 153 fecal samples and 49 beef samples were collected. Overall, 40 samples were tested positive for one O-group, and the detection rate in feces was higher than that in beef, 19.3% of which were tested positive for non-O157, and 0.50% positive for O157. After purification, 30 positive isolates were identified. O26 was detected most frequently, accounting for 73.3% of the total isolates, followed by O26, O121, O103, and O157, accounted for 73.3%, 16.7%, 6.7% and 3.3%, respectively. The results of virulence gene analysis showed that two strains of O26:H11 were isolated from beef, one being positive for stx1 and hly and the other being positive for hly. One strain of O26:H11 harboring the hly gene was obtained from feces. Therefore, 10.0% of the 30 strains were positive for virulence genes, and 3.4% were non-O157 STEC. Conclusion: The contamination rate of non-O157 E. coli, especially O26:H11, in feces and beef was significantly higher than that of O157. Shiga toxin-producing E. coli was even detected in the beef samples, which suggested that there is a potential risk of non-O157 E. coli contamination in the retail beef market. The detection and monitoring of non-O157 E. coli should be strengthened in China.
Multiplex PCR for Simultaneous Detection of Four Food-Borne Bacteria and Common Mold
XIONG Suyue, MI Ruifang, CHEN Xi, QI Biao, LI Jinchun, LI Jiapeng, QIAO Xiaoling, WANG Shouwei
2019, 40(4):  305-311.  doi:10.7506/spkx1002-6630-20180521-283
Asbtract ( 315 )   HTML ( 11)   PDF (2542KB) ( 178 )  
Related Articles | Metrics
In this study, a multiplex polymerase chain reaction (PCR) method was developed to simultaneously detect Staphylococcus aureus, Listeria monocytogenes, Salmonella, Escherichia coli O157:H7, and mold in foods. Species-specific primers were designed targeting the heat-resistant nuclease gene (nuc) in S. aureus, the invader upregulation protein gene (hilA) in Salmonella, the flagellum gene (flic) in E. coli O157:H7, the virulence regulation protein gene (prfA) in L. monocytogenes and the V5 region of the 18S rRNA gene in mold, and the PCR reaction system and conditions were optimized for highly specific amplification. Sausage, bread and tofu artificially contaminated with the five food-borne pathogens were enriched at 37 ℃. The detection limits of the five food-borne pathogens within 20 hours all reached 100 CFU/25 g. The multiplex PCR method established in this study is suitable for rapid detection of common pathogenic organisms in foods. Compared with traditional detection methods, it has the advantages of rapidity, simplicity and high specificity and thus, can be used to simultaneously detect bacteria and mold in foods.
Quantitative Analysis of Phthalic Acid Esters in Sesame Seeds and Their Migration Patterns during Oil Production
LIU Yulan, LIU Yan, HU Aipeng, MA Yuxiang, WEI Anchi, XU Yanhui
2019, 40(4):  312-317.  doi:10.7506/spkx1002-6630-20170813-165
Asbtract ( 273 )   HTML ( 13)   PDF (1914KB) ( 127 )  
Related Articles | Metrics
In this paper, the contents of phthalic acid esters (PAEs) in 20 sesame seed samples collected from different areas were analyzed. The migration of PAEs into crude sesame oil during oil processing was studied. The effects of raw materials and processing technologies on PAEs migration into sesame oil were clarified in order to develop technologies for accurately preventing and controlling the risk of PAEs migration and consequently to ensure and enhance the quality and safety of sesame oil. The results showed that all samples were found to contain PAEs. Dibutyl phthalate (DBP), di(2-ethtlhexyl) phthalate (DEHP) and diisononyl ortho-phthalate (DINP), with limits set for all of them (DBP ≤ 0.3 mg/kg, DEHP ≤ 1.5 mg/kg, and DINP ≤ 9.0 mg/kg) in the Chinese national standard, were detected in 100% of the samples in the range of 0.040–0.337, 0.085–1.971 and 0.343–0.806 mg/kg with an average of 0.137, 0.560 and 0.559 mg/kg, respectively. A total of 8ΣPAEs were detected in all samples in the range of 0.209–2.828 mg/kg with an average of 1.165 mg/kg. Five and 10 percent of the samples exceeded the national standard limits for DEHP and DBP, respectively. The PAEs were gradually migrated from sesame into crude oil and accumulated during oil production. The contents of DBP, DEHP and DINP and total PAEs content of the crude pressed oil were 1.16, 1.03, 1.11 and 1.07 times higher than those of sesame seeds, respectively. The solvent extracted oil contained 1.49, 1.27, 1.24 and 1.33 times more DBP, DEHP and DINP and total PAEs than sesame seeds, respectively. The content of PAEs in the peeled sesame oil was about 20% lower than that in the whole sesame oil, and the PAEs content in the extracted oil was about 1.2 times higher than that in the pressed oil.
Hyperspectral Imaging for Quantitative Quality Prediction Model in Digital Blending of Congou Black Tea
NING Jingming, LI Shuhuan, WANG Yujie, ZHANG Zhengzhu, SONG Yan, XU Qian, LU Guofu
2019, 40(4):  318-323.  doi:10.7506/spkx1002-6630-20171120-247
Asbtract ( 236 )   HTML ( 14)   PDF (3248KB) ( 138 )  
Related Articles | Metrics
Both spatial and spectral information of Congou black tea blends from superior fifth-grade and sixth-grade raw Keemun black tea leaves winnowed through 6 and 8 pores per inch were acquired by hyperspectral imaging technology. Spectral features were selected by successive projections algorithm (SPA), and all the obtained hyperspectral images were analyzed by principal component analysis (PCA). According to the weight coefficient, five dominant wavelengths were extracted for the collection of textual features by gray level co-occurrence matrix (GLCM). Subsequently, partial least squares (PLS), least squares-support vector machine (LS-SVM) and back propagation-artificial neural network (BP-ANN) classification models for prediction of the optimal blend ratio of raw tea leaves were developed based on the spectral features, textural features and data fusion, respectively and they were comparatively evaluated. It was indicated that the discrimination accuracy of the LS-SVM model based on data infusion was up to 94.5%. Our results may provide a theoretical basis for the digitization and standardized production of tea blends.
Authentication of Cow and Goat Milk Products by Two-Dimensional Electrophoresis
LIU Mingchang, HOU Yanmei, WANG Bin, YANG Yange, WU Yajun
2019, 40(4):  324-331.  doi:10.7506/spkx1002-6630-20180118-242
Asbtract ( 244 )   HTML ( 8)   PDF (4999KB) ( 81 )  
Related Articles | Metrics
Two-dimensional gel electrophoresis (2DGE) was applied in protein fingerprinting of cow and goat milk products. First of all, the protein profiles of cow and goat milk were compared to find out the differential proteins. Afterwards, the specificity of this method was tested by applying it to infant formula and whey protein powder from cow and goat milk and the sensitivity was evaluated by using different proportion mixtures of cow milk infant formula and goat milk infant formula. Finally, commercialized infant formula, liquid milk and yoghurt samples were tested. 2DGE method was confirmed to be highly informative and highly repeatable and it could visually present protein profiles. As proved by our data, liquid milk, whey protein and infant formula could be distinguished clearly by 2DGE and the detection limit reached 5%. Of 8 commercialized samples, one labelled as fermented goat milk was identified as cow milk with a clear protein fingerprint which could visually reflect the authenticity of the product
Detection of Norovirus Genogroup II in Lettuce by Droplet Digital PCR
CHEN Jiayin, FANG Ling, WU Shiwei, TANG Shuze, Peter C.K. Cheung, LI Hui, WU Xiyang
2019, 40(4):  332-337.  doi:10.7506/spkx1002-6630-20170915-214
Asbtract ( 265 )   HTML ( 11)   PDF (2080KB) ( 93 )  
Related Articles | Metrics
Objective: To develop a rapid and sensitive one-step reverse transcription droplet digital polymerase chain reaction (RT-ddPCR) assay for the detection of norovirus genogroup II (NoV GII) in lettuce. Methods: The RT-ddPCR system was optimized; the detection limit was tested using a series of 10-fold diluted enzyme digested plasmids containing the target gene sequence of NoV GII. The specificity was validated by using nucleic acids from Nov GII and other enteric viruses as targets. The repeatability of the method was also examined. Lettuce samples artificially infected with different concentrations (high, moderate, and low levels) of NoV GII were detected by RT-ddPCR following RNA extraction performed as described in ISO/TS 15216-1:2013. The influence of removal of inhibitors on the performance of RT-ddPCR was evaluated in comparison with reverse transcription quantitative polymerase chain reaction (RT-qPCR). Results: The maximum and minimum detection limits of RT-ddPCR were 8.47 × 104 and 2.12 copies/μL, respectively. The amplification efficiency was 95.44% (r = 0.997 3). The existence of inhibitors in lettuce showed no significant difference in the recovery RT-ddPCR at different contamination levels. The recovery rates of RT-qPCR at low contamination level with and without inhibitors were 1.43% and 9.71% respectively, which were significantly different from RT-ddPCR (11.80% and 12.53% respectively). Conclusions: The RT-ddPCR assay developed was stable in detecting food samples regardless of the presence of inhibitors such as lettuce. It could efficiently detect low concentrations of NoV GII virus in food without false-negative results, which may occur in RT-qPCR because of the existence of inhibitors. Therefore, this one-step RT-ddPCR assay was able to detect low levels of NoV GII in contaminated food samples, which indicates a considerable application prospect in the field of foodborne virus detection.
Geographical Traceability of Soybeans by Organic Composition Combined with Mineral Element Fingerprint
LU Baoxin, MA Nan, WANG Xia, LI Chaonan, QIAN Lili, ZHANG Dongjie
2019, 40(4):  338-344.  doi:10.7506/spkx1002-6630-20171009-033
Asbtract ( 257 )   HTML ( 7)   PDF (2334KB) ( 277 )  
Related Articles | Metrics
This study aimed to improve the stability and accuracy of mineral element fingerprinting for the geographical traceability of soybean. In this experiment, the contents of mineral elements in 168 soybean samples and the corresponding soil samples from Nenjiang county and Bei’an county in Heilongjiang province were determined by inductively coupled plasma mass spectrometry (ICP-MS). The contents of protein, fat, total soluble sugar and ash were determined as well. The results showed that the discriminant model established based on 10 characteristic indicators (seven mineral elements plus three organic compounds) selected by the stepwise selection method has an overall accuracy rate of 96.4% for the training set. Besides, the discrimination accuracy for soybean samples from Nenjiang county and Bei’an county were 98.1% and 95%, respectively. The overall discrimination accuracy for the validation set was 98.2% in the back substitution test, and the discrimination accuracy for soybean samples from Nenjiang county and Bei’an county were 100% and 96.7%, respectively. The overall discrimination accuracy for the validation set were higher than the test set (98.2% > 96.4%) indicating that all ten characteristic indicators carry sufficient information about geographical traceability.