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Table of Content

25 April 2020, Volume 41 Issue 8
Food Chemistry
Preparation of Oxidized Starch Hydrogel Encapsulating β-Carotene by Confined Crystallization
BAI Jie, QU Yinzi, WANG Shanshan, HUA Shan, ZHU Yuting, LI Yuan
2020, 41(8):  1-7.  doi:10.7506/spkx1002-6630-20190103-043
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In order to optimize the preparation condition of oxidized starch hydrogels as a carrier to encapsulate β-carotene, this study aimed to explore the effect of organic solvents, oxidized starch concentration and the amount of cross-linking agent on the formation of oxidized starch hydrogels. Considering the solubility of β-carotene and the volatility of organic solvents, dichloromethane was selected as the internal oil phase (O1). The results showed that hydrogels with small pore sizes and high loading efficiency of up to (29 ± 3.2)% were prepared at an oxidized starch concentration of 10%. The hydrogels with a molar ratio of carboxyl group to Fe3+ of 4.58:1 were most stable and could rapidly release the encapsulated β-carotene in an intestinal alkaline environment. The oxidized starch hydrogels can be a potential low-cost food delivery system to improve the stability, solubility and bioavailability of lipid-soluble functional ingredients.
Effect of Protein Oxidation on Rheological and Gelation Properties of Mutton Batters
ZHANG Hailu, HUANG Xiang, YANG Ran, AN Fengping, AI Mingyan, HUANG Qun
2020, 41(8):  8-13.  doi:10.7506/spkx1002-6630-20190618-211
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This study was performed in order to explore the effect of protein oxidation on the rheological and gel properties of mutton batters. Based on a model oxidation system, different degrees of oxidation were applied to mutton. The carbonyl and total sulfhydryl contents of myofibrillar proteins were determined, and the rheological properties, texture properties, gel strength, water-holding capacity and color of mutton batters were analyzed. The results showed that the carbonyl content increased significantly while the total sulfhydryl content decreased significantly with prolonging oxidation time. The shorter the oxidation time, the higher the storage modulus G’ for each frequency. As temperature rose, G’ was changed in three stages: decreasing slowly from 20 to 47 ℃, and then rapidly from 48 to 54 ℃, and finally increasing rapidly from 55 to 75 ℃. G’ gradually increased during the cooling process. Moreover, as the oxidation time was prolonged, the hardness, elasticity, cohesiveness, adhesiveness, chewiness and resilience of mutton batters declined, and the gel strength and water-holding capacity significantly decreased. The values of L* (brightness), a* (redness) and W (whiteness) also decreased with increasing protein oxidation time. This study showed that protein oxidation could lead to the deterioration of the rheological and gel properties of mutton batters, which adversely affects the processing characteristics of mutton.
Green Synthesis of Gold Nanoparticles Using Waste Black Sunflower Seed Shell Extract and Evaluation of Antioxidant and Catalytic Activities
GUAN Huanan, SONG Yan, GONG Dezhuang, LIU Bo, HAN Bolin, YANG Fan, LIU Xiaofei, ZHANG Na
2020, 41(8):  14-20.  doi:10.7506/spkx1002-6630-20181218-199
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Herein, we demonstrated a low-cost and eco-friendly method for the synthesis of gold nanoparticles (AuNPs) using waste black sunflower seed shell extract as both a reducing agent and protectant. The as-prepared sample was characterized by UV-vis spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The results showed that the synthesized AuNPs using 80% (V/V) of waste black sunflower seed shell extract had a characteristic absorption peak at 526 nm in the UV-vis spectrum. The mean particle size of the AuNPs was observed to be (7.25 ± 2.24) nm. The FTIR spectrum and the XRD pattern indicated that the extract could form a protective layer on the AuNPs surface, which conferred the AuNPs not only with high stability toward storage, heat, pH and salt, but also with strong antioxidant activity in scavenging 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. Furthermore, the AuNPs showed good catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol by excess NaBH4. We proposed that the AuNPs could be a potential catalyst for applications in food, biomedical and biopharmaceutical industries.
Preparation and Colloidal Properties of High-Concentration Linseed Oil Emulsions Stabilized by Egg White Protein Isolate
FANG Aihu, LI Lingyun, YANG Zongyun, XU Xinglian, WANG Yuexi, WANG Peng
2020, 41(8):  21-26.  doi:10.7506/spkx1002-6630-20181116-184
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In this study, high-concentration linseed oil emulsions stabilized by egg white protein isolate were prepared by high-speed shearing. The viscoelasticity of the emulsions was determined by rheological measurements, and the distribution of the water and oil phases was investigated by measuring the conductivity. At the same time, the microstructure was evaluated by particle size distribution and laser confocal scanning microscopy analysis. Based on the above investigations, we examined the effect of oil phase concentration on properties of high-concentration emulsions. The results showed that when the egg white protein isolate concentration was maintained at 6% (m/m), the average particle size of the emulsion droplets decreased with increasing the oil phase concentration from 65% to 70% to 75% (m/m), and the degree of flocculation increased, thereby causing an overall increase in the viscosity, storage and loss modulus of the emulsion. As a consequence, the oil droplets began to be tightly compressed to exhibit a polygonal morphology. At an oil phase concentration of 80% (m/m), the average particle size of the emulsion droplets was smaller but the particle size distribution was wider; the emulsion viscosity decreased, but the storage and loss modulus increased, and the emulsion appeared gelatinous with partial aggregation of the proteins in it. The emulsion with 85% (m/m) oil phase concentration contained a large proportion of proteins that did not take part in structuring. The proteins in the emulsion were randomly aggregated and separated from the oil phase, making the emulsion unstable. This study provides a basis for understanding the formation of high-concentration emulsions, and opened up a new way to achieve value-added utilization of egg white protein.
Formation and Removal of 3,4-Benzo(a)pyrene and 3-Monochloropropane-1,2-diol Esters at the Main Stages of Peanut Oil Processing
YANG Wei, LIU Hui, LEI Fenfen, HE Dongping, LUO Zhi, ZHENG Jingcheng, HU Chuanrong
2020, 41(8):  27-35.  doi:10.7506/spkx1002-6630-20190328-376
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High-temperature roasting and high-temperature deodorization during the processing of peanut oil readily lead to the generation of toxic substances. In this paper, the changes in the contents of 3,4-benzo(a)pyrene (BaP) and 3-monochloropropane-1,2-diol esters (3-MCPDE) during the high-temperature steps of peanut oil processing were examined, and the removal of BaP and 3-MCPDE was further explored. Results indicated that there were significant effects of roasting temperature and time as well as deodorization temperature and time on BaP and 3-MCPDE contents in peanut oil. The two parameters increased significantly when the discharging temperature and time exceeded 210 ℃ and 60 min during the roasting step, respectively. BaP content decreased significantly in peanut oil deodorized under high steam flux as compared with low steam flux. When the deodorization temperature was raised from 240 to 250 ℃, BaP and 3-MCPDE contents increased significantly (P < 0.05). Deodorization time had a continuous effect on BaP content while its influence on 3-MCPDE content was limited from 120 min onward. The content of chlorine in peanut oil before deodorization had a significant effect on the content of 3-MCPDE after deodorization. The amount of activated carbon, adsorption time and adsorption temperature had significant effects on the removal of BaP and 3-MCPDE. The best removal efficiency was obtained for both compounds under the conditions of 0.5% YS-900 activated carbon, 30 min and 110 ℃, and the residual amount and removal rate of BaP were 0.52 μg/kg and 77.5%, respectively. Three adsorbents were ranked in order of decreasing adsorption capacity toward 3-MCPDE as follows: YS-900 activated carbon > activated clay > ordinary activated carbon, and the highest removal rate was 23.5%. The adsorbents could not only significantly reduce the contents of BaP and 3-MCPDE in the peanut oil decolonization system, but also have a certain catalytic effect on the formation of both compounds.
Preparation of Small Molecular Antioxidant Peptides from Flaxseed Meal
ZHANG Wenmin, ZHANG Jian, ZHOU Haochun, ZHAO Di, LI He, LIU Xinqi, XIAO Lin
2020, 41(8):  36-44.  doi:10.7506/spkx1002-6630-20181130-356
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Objective: To extract protein from flaxseed meal and then use it to prepare antioxidant active peptides. Methods: Flaxseed protein was digested with alcalase, neutral protease or trypsin, and the antioxidant activities of the hydrolysates were characterized by measuring total antioxidant capacity, Ferric ion reducing antioxidant power (FRAP), hydroxyl radical scavenging ability and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation scavenging ability. The molecular mass (mw) distribution of the protein and its hydrolysates were analyzed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and gel permeation chromatography. The most antioxidant-active components were identified by HPLC-MS/MS analysis. Results: The smaller peptides (< 3 kDa) isolated from the alcalase hydrolysate had stronger antioxidant activity than did the larger ones (3–10 kDa). The total antioxidant capacity of the smaller peptides at 10 mg/mL was equivalent to (1.77 ± 0.03) mmol/L FeSO4, the hydroxyl radical scavenging rate was (57.13 ± 1.47) %, and the ability to scavenge ABTS radical cation was equivalent to (1.19 ± 0.03) mmol/L Trolox equivalent concentration. The protein content of fraction F2 with the strongest antioxidant activity separated by gel permeation chromatography accounted for 20% of the total amount. The antioxidant activity of F2 at 0.1 mg/mL was equivalent to 0.29 mmol/L FeSO4, accounting for 45.3% of the total. The flaxseed meal protein contained a full range of amino acids including the eight essential ones and thus could be considered as a high-quality plant protein. The antioxidant activity of its hydrolysates seemed to be affected by the specificity of the hydrolases and the molecular mass of the peptides. Flaxseed meal can be used to produce high antioxidant-active peptides.
Preparation and Application of Molecularly Imprinted Polymer in Solid Phase Extraction of Synephrine
LI Ling, SU Xuesu, ZHANG Yaohai, JIAO Bining, LIU Jintao, DONG Jiali
2020, 41(8):  45-51.  doi:10.7506/spkx1002-6630-20190401-014
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In this experiment, molecularly imprinted polymers (MIPs) were prepared by precipitation polymerization using synephrine as a template molecule, acrylic acid and hydroxyethyl acrylate as bifunctional monomers, azobisisobutyronitrile as an initiator, and ethylene glycol dimethacrylate as a crosslinking agent. The synthesis conditions were optimized through static adsorption experiments. The maximum adsorption capacity and specific recognition performance were evaluated under optimized conditions, and the adsorption mechanism was explored. The morphology of the synthesized polymer was characterized by scanning electron microscopy, and its application as a solid phase extraction (SPE) sorbent for separating synephrine extracted from Fructus Aurantii immaturus was investigated. MIPs with good morphology and specific recognition capacity (maximum adsorption capacity of 228.82 μmol/g) for synephrine were obtained using 10 mL of acetonitrile as porogen at a molar ratio of template molecule to functional monomer to initiator to cross-linker of 1:4:2:20. After being purified with the SPE sorbent, the purity of synephrine increased from 1.93% to 93.34% with a recovery of 73.90%.
Effect of Fat Substitute on Physical Properties of Margarine
XU Qunying, ZHAO Jinzhuang
2020, 41(8):  52-56.  doi:10.7506/spkx1002-6630-20191119-219
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A fat substitute was prepared as a mixture of high-ester citrus pectin with carboxymethyl cellulose (CMC) and applied in margarine. The optimum addition level was determined by texture analysis, rheological measurement, and differential scanning calorimetry (DSC). Experimental results showed that as the addition of fat substitutes increased, the hardness, consistency and viscosity of the samples decreased. Moreover, the area of the hysteresis loop increased, the transformation from crystal type β’ to β became more obvious, and the structure gradually became loose. Finally, we concluded that the optimum addition level was 10%.
Effects of Pretreatments on Lipid Concomitants Content in Cold Pressed Canola Oil
ZHANG Huanhuan, GAO Feihu, HUANG Taocui, ZENG Zhihong, ZHANG Ling, ZHANG Xuemei, LI Xue, LIANG Yexing
2020, 41(8):  57-61.  doi:10.7506/spkx1002-6630-20190401-002
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The effects of microwaving and roasting pretreatments on the contents of phytosterols, tocopherols and total phenolics in cold pressed canola oil were studied. The rusults indicated that five phytosterols including cholesterol, brassicasterol, campesterol, β-sitosterol and stigmasterol were detected in both treatment groups. The amounts of individual and total phytosterols showed an overall upward trend with increasing microwaving time and the highest total amount of 982.12 mg/100 g was obtained at 2 minutes, which was 59.85 mg/100 g higher than that of the control group. Roasting pretreatment significantly affected the total phytosterol content of canola oil. The lowest and highest values were found in the samples roasted at 180 ℃ for 5 and 10 min, respectivley. Either treated oil mainly contained α-tocopherol and γ-tocopherol and had significantly higher contents of individual and total tocopherols than did the control. The content of total phenolics continuously increased with prolonging microwaving or roasting time, and it increased faster from 0 to 1.5 min than from 1.5 to 2 min of microwaving, and faster from 0 to 10 min than from 10 to 15 min of roasting at 180 ℃.
Effect of Lotus Seedpod Procyanidins on Bread Quality and Functional Properties
ZHENG Yan, ZHANG Xinyun, SUI Yong
2020, 41(8):  62-68.  doi:10.7506/spkx1002-6630-20181030-348
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The effects of lotus seedpod procyanidins (LSPC) on the baking quality, antioxidant activity and starch digestibility of bread were investigated in this study. The results showed that the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity of bread fortified with 0.25%, 0.50%, 1.00% and 2.00% of LSPC was significantly increased as compared with control bread (P < 0.05), and the antioxidant activity was positively correlated with the amount of LSPC added to bread. The amount of glucose produced after 180 min digestion of starch from bread fortified with 2.00% of LSPC significantly declined as compared with control and other addition levels (P < 0.05). The baking quality of bread was affected by LSPC, as manifested by significantly increased hardness (P < 0.05) and significantly decreased specific volume of bread fortified with LSPC at 1.00% and 2.00% relative to control bread (P < 0.05). In addition, the color and odors of bread fortified with LSPC were significantly different from those of control bread (P < 0.05). LSPC fortification of bread may be considered as a way to supply dietary antioxidant and postpone the digestion of starch in vivo, which provides experimental support for the use of LSPC in staple food.
Effects of Low Acyl and High Acyl Gellan Gum on the Thermal Stability of Anthocyanins from Passion Fruit Peel in Model Beverages
CHENG Hongzhen, CAI Zhipeng, WANG Jing, XU Mingsheng, SHEN Yonggen, LU Jianqing, LIU Fuyuan, LI Xiaoming
2020, 41(8):  69-76.  doi:10.7506/spkx1002-6630-20190422-290
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In this study, the pH-differential method and a fully automatic colorimeter together with the degradation kinetics model were used to examine the effects of low acyl (LA) and high acyl (HA) gellan gum on the thermal stability of anthocyanins from passion fruit peel (PFP) in model beverages in the presence of ascorbic acid, which were heat-treated at 85 ℃ for 0, 1, 2, 3, 4 or 5 h. The anthocyanin components of PFP were identified by ultraperformance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (UPLC/Q-TOF-MS). The results showed that during the heat treatment, the anthocyanin contents in four model beverage systems, i.e., PFP, PFP + VC, PFP + VC+ LA and PFP + VC + HA, showed downward trends, and the degradation of anthocyanins conformed to a first-order kinetic model. The half-lives of anthocyanins in the four systems were 308.44, 155.09, 189.69 and 217.92 min, respectively. Low concentration (0.2%–0.5%) of gellan gum could improve the stability of anthocyanins, and the interaction between HA and anthocyanins was stronger than that between LA and anthocyanins. With increasing heating period from 1 to 5 h, the L* value increased significantly whereas the a* and b* values decreased significantly (P < 0.05), but greater changes in all these parameters were observed between 0 and 1 h. Four anthocyanins from passion fruit peel, namely cyanidin-3-glucoside, cyanidin-3-glucose, cyanidin-3-rutinoside and paeoniflorin-3-glucoside, were identified.
Encapsulation of ACE Inhibitory Peptide with Ferritin-Sodium Alginate Nanoparticles
XIA Weirong, LI Ying, CHAI Zhi, CHEN Xiao’e, ZHOU Jianzhong, FENG Jin, FANG Xubo
2020, 41(8):  77-82.  doi:10.7506/spkx1002-6630-20181209-106
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By taking advantage of the controlled release capacity of sodium alginate (SA) and the reversible assembly characteristics of under extremely acidic conditions, horse spleen apoferritin (HSF) and SA were used as nano-carriers for encapsulation of an angiotensin converting enzyme (ACE) inhibitory peptide, alanine-histidine-leucine-leucine (Ala-His-Leu-Leu, AHLL), aiming to improve the absorption of AHLL in the digestive system. The results showed that the optimal conditions for the preparation of nanoparticles that provided maximum encapsulation efficiency were determined as follows: HSF concentration 1–2 μmol/L, sodium alginate concentration 10 mg/L, and final concentration of AHLL 100–200 μg/mL. The as-prepared nanoparticle system was stable. Preliminary structural representation of HSF-AHLL and HSF-SA-AHLL was performed with transmission electron microscopy, which indicated that a uniform nano-system has been formed. The particle size and potential of the nanoparticles demonstrated the stability of the encapsulation system. Furthermore, AHLL in the nano-system could be well absorbed by the digestive system as revealed by the in vitro transport test uisng Caco-2 cell monolayer model. These results support that HSF-SA could be applied as a nanocarrier for maintaining the homeostasis of bioactive peptides and provide an effective way to improve the absorption of bioactive nutrients.
Bioengineering
Effect of C-5 Sterol Desaturase ERG3 on Saccharomyces cerevisiae Halotolerance
WANG Hui, CHEN Xiong, LIN Weichao, LI Yaoling, DAI Jun
2020, 41(8):  83-90.  doi:10.7506/spkx1002-6630-20190304-042
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In order to elucidate the relationship between the sterol composition and halotolerance of Saccharomyccs cerevisiae, strain Bs-1 was constructed by knocking out the key gene ERG3 involved in ergosterol synthesis. The growth of Bs-1 was inhibited on YPD (yeast extract, peptone and dextrose) plates containing 60 g/L NaCl as compared with wild type strain BY4741. It was unable to survive on YPD containing 80 g/L. Using gas chromatography-mass spectrometry (GC-MS), we found that Bs-1 could synthesize 5,6-dihydroergosterol rather than ergosterol. In addition, the metabolites of Bs-1 and BY4741 were analyzed. The maximum OD600 nm of Bs-1 was 5.56 ± 0.30 in YPD containing 60 g/L NaCl, which was 45% lower than that of BY4741; the maximum ethanol yield of Bs-1 was (4.20 ± 0.00) g/L, which was 35% lower than that of BY4741; and Bs-1 produced larger amount of extracellular glycerol than did BY4741, but its ability to retain glycerol was weakened. These results indicate that changes in sterol composition could affect metabolic characteristics and membrane fluidity of yeast cells, resulting in increased intracellular glycerol efflux and decreased yeast salt tolerance.
Extraction and Stability of Monascus Pigments from Fermentation Broth of Monascus purpureus YY1-3 Using Ethanol/Ammonium Sulfate Aqueous Two-Phase System
KONG Weibao, YANG Shuling, YANG Yang, CHEN Dong, GUO Baomin, ZHANG Aimei, NIU Shiquan
2020, 41(8):  91-99.  doi:10.7506/spkx1002-6630-20190408-095
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Monascus pigments (MPs) were extracted from the fermentation broth of Monascus purpureus YY1-3 in a simple and efficient way using an ethanol/ammonium sulfate aqueous two-phase system (ATPS). Thin layer chromatography (TLC) was used to analyze the composition of the MPs and their stability was also tested. The results showed that when the ATPS was composed of 16% (m/m) ethanol and 28% (m/m) ammonium sulfate, the maximum partition coefficient and recovery rate of MPs of 171.91 and 98.13% were obtained respectively. When the volume proportion of the top phase extraction solution-ethanol was 1:0.5, ammonium sulfate could be effectively removed from it. TLC showed that the extract was composed of six components, mainly Monascus red and yellow pigments. The MPs were stable in darkness, pH 4–8 and 25–65 ℃, as well as in the presence of common metal ions and food additives.
Recombinant Expression of Phospholipase D from Streptomyces septatus in Pichia pastoris and Analysis of Its Enzymatic Properties
HUANG Lin, MA Jieying, WANG Shuang, WANG Nan, MORADANA GAMAGE Rasadi Sajeewa Rajakaruna, LU Fuping, LIU Yihan
2020, 41(8):  100-107.  doi:10.7506/spkx1002-6630-20190903-029
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The phospholipase D (PLD) encoding sequence (pld) was amplified from the genomic DNA of Streptomyces septatus TCCC 21057. The optimized pldm sequence was synthesized according to the codon usage bias in Pichia pastoris and then integrated into the expression vector pPIC9K. The resulting recombinant plasmid was then transformed into P. pastoris GS115 competent cells to obtain the recombinant strain GS115/pPIC9K-pldm. The transphosphatidylation activity of recombinant PLD (rPLDM) could reach 2.37 U/mL after shaking flask fermentation. The recombinant enzyme was purified and characterized. Its optimal activity was observed at 60 ℃ and pH 6.5. The yield of phosphatidylserine (PS) could reach 33% after 6 h reaction in a purely aqueous system under the following conditions: molar ratio between the substrates soybean phosphatidylcholine (PC) and L-serine substrate 1:10, rPLDM amount 4.0 U/mL, temperature 40 ℃, pH 6.5, and Ca2+ concentration 10 mmol/L. This study lays a foundation for enzymatic synthesis of PS as a novel food ingredient.
Screening of Lactobacillus for Inhibitory Effects on HT-29 Cell Proliferationand Probiotic Properties
YUE Yingxue, YAN Fenfen, LI Bailiang, SONG Yue, SHI Jialu, GUAN Jiaqi, HUO Guicheng
2020, 41(8):  108-115.  doi:10.7506/spkx1002-6630-20190310-119
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In this experiment, 15 strains of Lactobacillus were studied for their inhibition on HT-29 cell proliferation, and 8 of these were found to have strong inhibition effect and they were texted for their adhesion to HT-29 cells and antioxidant capacity. The results showed that the inhibition rates of the selected strains against the proliferation of HT-29 cells ranged from 10.02% to 15.63%, and the adhesion rates to HT-29 cells ranged from 3.9% to 19.1%. The reducing capacity of the live bacterial suspensions, cell lysates, and fermentation supernatants were 23.43–271.76 μmol/L L-cysteine hydrochloride, and the scavenging rates against 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl and superoxide anion radicals were 10.89%–50.42%, 7.46%–33.16%, and 17.64%–46.13%, respectively, and the inhibition rate against lipid oxidation were 10.45%–51.91%. Principal component analysis showed that L. acidophilus KLDS1.0901 had the best comprehensive performance, followed by L. acidophilus KLDS1.1003. The two strains had good tolerance to simulated gastrointestinal fluids. After digestion, the viable count could still be above 108 CFU/mL, and the survival rate was 50%. In general, L. acidophilus KLDS1.0901 and KLDS1.1003 had a strong ability to inhibit HT-29 cell proliferation and possessed good probiotic properties with L. acidophilus KLDS1.0901 being more effective.
Isolation, Purification and Identification of Dipeptidyl Peptidase-4 Inhibitor from Lactic Acid Bacterial Metabolite
DONG Jie, LIU Lu, JIA Chengli, ZHU Junling, Lü Jiaping
2020, 41(8):  116-122.  doi:10.7506/spkx1002-6630-20190411-138
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In this study, the metabolites of Lactobacillus plantarum BLP12 with inhibitory activity against dipeptidyl peptidase-4 (DPP-4) were separated and purified by organic solvent extraction, ultrafiltration membrane, gel chromatography and high performance liquid chromatography. The substrate N-glycyl-prolyl-p-nitroanilide hydrochloride (Gly-Pro-pNA) was applied to determine DPP-4 activity based on the strong absorption at around 405 nm of the degradation product of Gly-Pro-pNA. The fraction with strong inhibitory activity was selected for chemical composition analysis by liquid chromatography tandem mass spectrometry. A total of 61 substances were identified including dodecyl sulfate, which has been reported as a DPP-4 inhibitor.
Gene Cloning, Expression and Characterization of β-N-Acetylglucosaminidase from Bacillus amyloliquefaciens
CHEN Baoli, QIN Zhen, ZHAO Liming
2020, 41(8):  123-129.  doi:10.7506/spkx1002-6630-20190221-132
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In this study, a novel β-N-acetylglucosaminidase gene was cloned from Bacillus amyloliquefaciens YX-01 and successfully expressed in Escherichia coli BL21. The recombinant protein (defined as BaNagase) was purified by Ni-IDA affinity chromatography and analyzed. The results showed that it encoded 616 amino acids, with the highest similarity (76.97%) to the sequence of β-N-acetylglucosidase (AIY91451.1) from B. subtilis. According to the phylogenetic analysis and multiple sequence alignments, BaNagase belonged to glycoside hydrolase (GH) family 3. The recombinant BaNagase showed specific activity of 16.42 U/mg toward the substrate pNP-GlcNAc. Its optimal pH value was 6.0 and the optimal reaction temperature was 65 ℃. BaNagase showed good stability below 55 ℃ at which more than 70% of initial activity was still retained. BaNagase exhibited strong thermostability and strict substrate specificity. This study provides a theoretical basis for efficient preparation of N-acetylglucosamine.
Bacterial Community Structure and Diversity during Fermentation of Chinese Fen-Maotai-Flavored Liquor in Pottery Jars
HU Xiaoxia, HUANG Yongguang, JIANG Xiang, ZHU Jiahe, JIN Lei
2020, 41(8):  130-138.  doi:10.7506/spkx1002-6630-20190314-175
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In this paper, high-throughput sequencing technology combined with mathematical statistics software was used to analyze the bacterial community structure during the fermentation of Chinese Fen-Maotai-flavored liquor in pottery jars. The results showed that Firmicutes and Proteobacteria were the dominant bacterial phyla; Weissella, Gluconobacter, Lactobacillus, Staphylococcus, Pseudomonas, Acetobacter, Bacillus, Kroppenstedtia, Oceanobacillus, Lentibacillus, Pediococcus, Enterobacter, Komagataeibacter, Acinetobacter, Leuconostoc, Kozakia and Pantoea were the main bacterial genera, among which, Weissella, Staphylococcus, Lactobacillus and Gluconobacter were dominant. The main bacterial community structure had the characteristics of the main bacterial community structures of both Fen-flavored liquor and Maotai-flavored liquor. On average 73.53% of the main bacterial genera increased significantly while the remaining 20.59% decreased substantially during the fermentation process. During the late stage of fermentation, the composition of the main bacterial genera was relatively stable, and the relative abundance of each genus was less than 25.97%. On average, 81.12% of the major bacterial genera showed a significantly positive correlation whereas the remaining 18.88% showed an antagonistic correlation.
Molecular Docking of Small-Molecule Monosaccharides and Their Analogues with α-Glucosidase
XU Xiaomei, WEN Jiaying, WANG Qinghua
2020, 41(8):  139-143.  doi:10.7506/spkx1002-6630-20181201-001
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The molecular docking study of 20 small-molecule monosaccharides and their analogues with α-glucosidase was carried out with AutoDock 4.2 software. The relationship between the binding free energy and the half-maximum inhibitory concentration (IC50) was analyzed, and the molecular structure of the inhibitor was further optimized according to the interaction between the receptor and the ligand. The results showed that the amino acid residues Asp542, Asp443, His600, Asp327 and Arg526 in α-glucosidase were important sites for hydrogen bonding between each of the compounds and the enzyme. After replacing the O atom on the sugar ring with N or C atoms, the binding free energy of the former became smaller, and the binding of ligand to the receptor was stronger. The docking results after the molecular structure modification of validamine showed that the N atom on the six-membered ring and the presence of the –NH2 substituent on the ring played a very important role in the docking of the molecules with α-glucosidase. This study provides a new idea for the screening and optimized design of high-efficiency α-glucosidase inhibitors in the future.
Screening for and Antioxidant Activities of High Exopolysaccharide-Producing Bifidobacterium from the Intestinal Tract of Uygur Infants and Their Mothers in Xinjiang
CAI Jingjing, XU Xiaoyu, ZHANG Yan, ZHANG Yachuan, WEI Xiaojing, KAN Zeyu, NI Yongqing
2020, 41(8):  144-151.  doi:10.7506/spkx1002-6630-20190305-044
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This study aimed to isolate and identify Bifidobacterium strains from the feces of Uygur infants and their mothers’ in Xinjiang. Using Wilkins-Chalgren anaerobic agar and BSM medium plates, Bifidobacterium strains were isolated and they were identified by repetitive extragenic palindromic-polymerase chain reaction (rep-PCR) fingerprinting and 16S rRNA gene analysis. High-yield expolysaccharides (EPS) producing strains were selected from these isolates and the antioxidant activities of the EPS produced by the selected strains as well as their tolerance and auto-adhesion ability were evaluated. The results showed that a total of 52 stains of Bifidobacterium were isolated from 20 feces samples and they belonged to B. pseudocatenulatum (14 strains), B. pseudolongum (8 strains), B. bifidum (9 strains), B. breve (7 strains), B. longum subsp. infantis (5 strains), B. animal subsp. lactis (6 strains) and B. longum (3 strains). respectively. Through phenotype screening and secondary screening using the phenol sulfuric acid method, we found 7 strains of Bifidobacterium with higher EPS yield. The yield of EPS produced by each of the 7 strains was more than 400 mg/L after 36 h fermentation at 37 ℃. The EPS had the ability to scavenge H2O2, superoxide anion, hydroxyl and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. Besides, strain BF66-16 had stronger tolerance to gastrointestinal juice and auto-adhesion ability than the other six strains. Thus, BF66-16 can be used as a potential antioxidant strain in the pharmaceutical and food industries.
Construction and Application of a Predictive Model for Determination of Polymalic Acid in the Fermentation Broth of Aureobasidium pullulans by Near-Infrared Spectroscopy
ZHANG Yinghao, XUE Zhaoyang, ZHAO Tingbin, YIN Haisong, QIAO Changsheng,
2020, 41(8):  152-158.  doi:10.7506/spkx1002-6630-20190504-013
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High performance liquid chromatography (HPLC) was used to measure the polymalic acid concentration in the fermentation broth of Aureobasidium pullulans. Interval partial least square regression (iPLSR) combined with moving window PLSR (MWPLSR) was used to confirm 5 638–6 024 cm-1 as the waveband for modeling. Multiplicative scatter correlation (MSC), standard normal variate (SNV), Savitzky-Golay 55 points smoothing and 1st derivative spectrum were successively operated as spectral pre-processing methods, and then PLSR with the first 5 factors was used to develop a predictive model with the highest accuracy. The root mean square of prediction (RMSEP) and correlation coefficient of prediction (Rp) of the model were 1.553 g/L and 0.970 0 for the internal test set, and 1.378 g/L and 0.992 4 for the external test set, respectively, and a paired t-test at 95% confidence level demonstrated that the maximum deviations between the HPLC values and the model predicted values were calculated as 1.48 and 0.83 g/L, respectively. There was no significant difference among three parallel predictions for one sample. When the model was applied to medium composition optimization and mutant screening, large prediction errors were found with paired t-test. However, the model could reliably predict polymalic acid concentration under the premise that the model calculated values were larger than 3.19 and 1.44 g/L, respectively, indicating the potential application of the near-infrared model in medium composition optimization and strain screening.
Component Analysis
Analysis of Taste Compounds in Stewed Chicken Broth of Beijing Youji
WANG Tianze, TAN Jia, DU Wenbin, ZHEN Dawei, XIE Jianchun
2020, 41(8):  159-164.  doi:10.7506/spkx1002-6630-20190505-022
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In order to understand taste components in the stewed chicken broth of Beijing Youji, the compositions of free amino acids and nucleotides were analyzed by high performance liquid chromatography (HPLC) and the taste active values (TAVs) of the nucleotide compounds were calculated. The results showed that amino acids with umami and sweet taste together accounted for 54.52% of the total amino acids, much higher than the percentage of bitter taste amino acids (34.47%). Among the free amino acids determined, alanine and glutamic acid, with umami and sweet taste, were more abundant and had higher TAVs, indicating that they contribute highly to the umami taste of the chicken broth. The concentration and TAV of inosine 5’-monophosphate (5’-IMP) were much higher than those of adenosine 5’-monophosphate (5’-AMP) and guanosine 5’-monophosphate (5’-GMP), indicating 5’-IMP to be the major nucleotide contributing to the umami taste of the broth. Furthermore, chromatographic separation of the broth was performed with Sephadex G-15, yielding three taste-active fractions. Fraction 2 exhibited obviously stronger umami taste than that of the chicken broth. High performance gel liquid chromatography analysis showed that the fraction was mainly composed of oligopeptides (accounting for 84.29% of the total peak area) with molecular mass < 3 kDa. Then this fraction was subjected to matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) analysis, and peaks with higher intensity were selected for tandem MS analysis. As a result, four peptides were identified, Leu-Val-Gln-Tyr, Val-His-Ala-His-Ser, Ala-Gln-Asn-Ser-Tyr-Pro-His-Ala, and Ala-Glu-Gln-Tyr-Arg-Leu-Val-Gly. These peptides, mainly composed of umami and sweet amino acids like Gln, Ala and Ser, may contribute to the delicious taste of chicken broth.
Simultaneous Determination of 5 Phenolic Acids Involved in the Phenylpropanoid Pathway of Postharvest Wax Apple (Syzygium samarangenese [Blume] Merrill & L.M. Perry) by High Performance Liquid Chromatography
KUANG Fengyuan, WU Guangbin, ZHANG Shen, HUANG Lina, CHEN Fahe
2020, 41(8):  165-170.  doi:10.7506/spkx1002-6630-20190303-014
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A simple and sensitive high performance liquid chromatography (HPLC) method was established for simultaneous determination of 5 phenolic acids (trans-cinnamic acid, p-coumaric acid, caffeic acid, ferulic acid and sinapic acid) involved in the lignin synthesis of harvested wax apple. The chromatographic separation was achieved using an InfinityLab Poroahell C18 column through gradient elution with a mobile phases consisting of methanol and acetic acid aqueous solution (pH 2.4) at a flow rate of 0.8 mL/min. The column temperature was set at 25 ℃. The detection wavelengths were set at 279 and 320 nm. The method exhibited a wide linear range with correlation coefficients all above 0.999 4. The limits of detection (LODs) were in the range of 0.01–0.03 mg/kg and the limits of quantitation (LOQs) were in the range of 0.03–0.09 mg/kg. The spiked recoveries ranged from 86.18%–99.05%, with relative standard deviations (RSDs) less than 5%. This method proved to be accurate, sensitive and simple and could be applied to determine the 5 phenolic acids in wax apple. The measured contents of trans-cinnamic acid, p-coumaric acid, caffeic acid, ferulic acid and sinapic acid were 11.46–24.69, 0.92–1.45, 2.31–5.32, 8.86–20.58 and 9.48–22.62 mg/kg in wax apple, respectively.
Changes in Flavor Precursors during Postmortem Ageing of Tan Sheep Meat as Determined by Ultra-high Performance Liquid Chromatography-Mass Spectrometry
YOU Liqin, LUO Ruiming, YUAN Yudong, LI Zixin
2020, 41(8):  171-176.  doi:10.7506/spkx1002-6630-20181217-178
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The study aimed to examine the effects of postmortem ageing on the type and contents of characteristic flavor metabolites and on the metabolic pathways of flavor precursors in the Longissimus dorsi muscle of Tan sheep. Metabolites that differed among the samples aged at 4 ℃ for 0, 4 and 8 day were identified by ultra-high performance liquid chromatography-mass spectrometry. The results showed that among the differential metabolites, flavor precursors such as carbohydrates and organic acids metabolism significantly changed on day 4 and amino acids, nucleic acids and lipids on day 8. The flavor metabolites such as citric acid, beta-citryl-L-glutamic acid, N-acetyl-L-methionine, D-phenylalanine, histidinyl-arginine and eicosapentaenoic acid increased with prolonged ageing. Pentose phosphate metabolism, the tricarboxylic acid cycle, the synthesis of amino acid and purine metabolism were the key metabolic pathways related to the formation of flavor precursors. The study may provide scientific evidence for further study on the role of postmortem ageing in regulating the flavor of Tan sheep mutton.
Optimization of Brewing Process for Sweet Rice Wine from Brow Rice and Analysis of Its Volatile Components
SU Jiajia, YANG Tian, TONG Enjie, ZHAO Xueying, HE Chenghao, YANG Na, XU Xueming, WU Fengfeng
2020, 41(8):  177-185.  doi:10.7506/spkx1002-6630-20190418-239
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The preparation of sweet rice wine from brown rice was optimized using single factor and orthogonal array design methods for higher comprehensive sensory evaluation scores as calculated by fuzzy mathematics. Headspace solid phase microextraction (HS-SPME) coupled with gas chromatography-olfactometry-mass spectrometry (GC-O-MS) and partial least squares regression (PLSR) were used to compare the flavor characteristics of brown rice wine with those of glutinous rice wine, and the correlation between flavor components and sensory attributes of brown rice wine was explored. The results showed that the optimum preparation conditions were determined as follows: soaking time of brown rice 8 h, cooking time 35 min, adding 0.4% koji, and fermentation at 35 ℃ for 60 h. A total of 47 flavor substances were identified in the brown rice wine prepared under the optimized conditions; 29 of these could be smelled and recognized. At a split ratio of 27, ethanol, ethyl butyrate, 2-pentylfuran, methylheptenone, hexanol, and mushroom alcohol could still be sniffed and recognized as the main aroma of brown rice wine. PLSR analysis showed that the flavor components such as ethanol and ethyl butyrate had a strongly positive correlation with the winy, fruity and floral aroma of the rice wine, while 2-pentylfuran, methylheptenone, hexanol, and mushroom alcohol had a strong correlation with the rice aroma. These results provide a theoretical basis for the preparation and flavor evaluation of brown rice wine with unique flavor.
Effects of Drying Methods on Nutritional Quality and Volatile Substances of Okra Fruit Harvested at Different Growth Stages
MA Luyao, LIN Haifeng, WANG Zhe, YIN Junyi
2020, 41(8):  186-193.  doi:10.7506/spkx1002-6630-20190519-212
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Fresh okra fruit harvested at different growth stages were subjected to hot-air drying after fixation (SHD), hot-air drying (HD), natural drying (ND) and freeze drying (FD), separately. The effects of these drying methods on the contents of ash, moisture, amino acids and volatile substances in dried products were investigated. The results showed that the moisture content of okra was relatively low after SHD and HD. But FD had less effect on flavonoids as compared with other drying methods. Dimethyl sulfide was the characteristic volatile substance of fresh okra. It was found that the four drying treatments could contribute to increased number of volatile substances to different extents and also result in changes in the relative contents of volatile substances including dimethyl sulfide. The most abundant volatile substances were alcohols and aldehydes after SHD, while the relative contents of alcohols were higher after ND. The relative content of aldehydes was higher after FD and HD. These findings suggested that the characteristic volatile substances of fresh okra fruit were retained, and at the same time new volatile substances appeared after all drying treatments. Combinations of these substances in different proportions imparted distinct aromas to okra fruit dried by?different drying methods.
Effects of Mutton Tallow Subjected to Different Treatments on Aroma Compounds Generated from Thermal Reaction Systems as Evaluated by Gas Chromatography-Mass Spectrometry, Descriptive Sensory Analysis and Partial Least Squares Regression
MA Xueping, ZHAN Ping, TIAN Honglei, WEI Zhisheng, LI Kaixuan
2020, 41(8):  194-201.  doi:10.7506/spkx1002-6630-20190528-341
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Gas chromatography-mass spectrometry (GC-MS) and descriptive sensory analysis (DSA) were used to analyze and identify the flavor characteristics of the Maillard reaction products (MRPs) prepared from native and modified mutton tallow (subjected to enzymatic hydrolysis, low temperature oxidation, their combination or high temperature oxidation). The results showed that there was a significant difference in the flavor characteristics of the four MRPs. The MRPs prepared from mutton tallow subjected to enzymatic hydrolysis and mild thermal oxidization showed obvious meaty, muttony and fatty aromas, and contained a variety of characteristic muttony aroma components, including nonanal, benzaldehyde, S-ethyl ethanethioate, dibutyl phthalate, 2-hexylthiophene, 2-heptylthiophene, 2-acetylfuran, 2-n-pentylfuran, and 2,6-di-tert-butyl-4-methylphenol. It was further confirmed by partial least squares regression (PLSR) analysis that mutton tallow subjected to enzymatic hydrolysis and mild thermal oxidization was the most suitable flavor precursor.
Changes in Flavor Characteristics of Sea Catfish Broth during Cooking Process
FENG Yuan, ZHAO Honglei, QU Shiyao, XU Yongxia, LI Haoyu, ZHOU Xiao, LI Xuepeng, LI Jianrong
2020, 41(8):  202-207.  doi:10.7506/spkx1002-6630-20190523-283
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The effect of cooking time on the flavor characteristics of sea catfish broth were investigated in this paper. Electronic nose, electronic tongue and gas chromatography-mass spectrometry (GC-MS) were used to analyze the flavor composition of fish broth, and the main flavor compounds were determined by relative odor activity values (ROAV). The results showed that the contents of crude protein, crude fat and ash in fish broth increased significantly (P < 0.05) while moisture content decreased but not significantly (P > 0.05) with the prolongation of cooking time. Soluble peptide content increased significantly (P < 0.05) from 1 h onward. Both electronic nose and electronic tongue could well distinguish the smell and taste of fish broth with different cooking times. Meanwhile, a total of 44 volatile compounds were identified by GC-MS, including aldehydes, alcohols, hydrocarbons, ketones, furans and esters, and 24, 33, 21 and 18 volatiles were detected in fish broth cooked for 0.5, 1, 1.5 and 2 h, respectively. With the extension of cooking time, the relative amounts of aldehydes and alcohols significantly increased. Hexanal, heptanal, (E)-2-heptenal, (E)-2-octenal, nonanal, 1-octene-3-ol, D-limonene and 2-pentylfuran were the main flavor substances in sea catfish broth.
Analysis of Nutritional Composition and Aroma Compounds of Potato-Rice Wine
LIANG Qiang, YAO Yingzheng, ZENG Shiqin, XIONG Wei, DONG Ling, XUAN Pu
2020, 41(8):  208-214.  doi:10.7506/spkx1002-6630-20190513-128
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The nutritional composition of potato-rice wines made from glutinous rice, fresh potatoes and their mixtures in different proportions (25:75, 50:50 and 75:25) was determined, and their volatile aroma compounds were analyzed by headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry to study the influence of potatoes on the nutritional composition and aroma compounds of rice wine. The results showed that addition of potatoes to rice greatly increased dietary fiber content, and enhanced vitamin C content from 0 to 3.95 mg/100 g and alcohol content from 0.64% to 3.34% compared with pure rice wine. Potato addition reduced sugar-to-acid ratio and the total amount of amino acids but increased the amount of tryptophan, and improved the amino acid composition of rice wine. A total of 61 aroma compounds were identified in all wine samples, mainly including isoamylol, isobutanol, phenylethyl alcohol, hexanol, ethyl palmitate, isoamyl acetate, ethyl caprylate, acetic acid, hexanal, acetoin, β-caryophyllene, and 2-amylfuran, and 67% of these compounds were alcohols and esters, whose amount together accounted for over 80% of the total aroma compounds. In potato-rice wines made with 0%–50% and 75% potatoes, isoamylol and phenylethyl alcohol were the most abundant aroma components, respectively. Principal component analysis (PCA) indicated that addition of different levels of potatoes had a great influence on the aroma composition of rice wine. In general, addition of proper amounts of fresh potatoes (25%–50%) could impart well-balanced nutritional composition, improved taste and abundant aroma compounds to potato-rice wine.
Composition and Sources of Haze-Active Proteins in Chinese Yellow Rice Wine
XIE Guangfa, FAN Shiying, FU Jianwei, HU Zhiming, LU Jian, TAN Xinyong, SUN Junyong, FU Zukang, WANG Lan, MAO Qingzhong, LI Guolong
2020, 41(8):  215-219.  doi:10.7506/spkx1002-6630-20190617-177
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The main components of haze-active proteins in Chinese yellow rice wine were separated by two-dimensional electrophoresis (2-DE), and then identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS). The haze-active proteins derived from wheat included avenin-like protein A, avenin-like protein B, avenin-like precursor, dimeric alpha-amylase inhibitor and trypsin precursor, and those derived from rice included hypothetical protein OSJ_04535, hypothetical protein OSI_17439 and protein H0313F03.18. By analyzing the major protein components of raw materials for the rice wine and samples collected during the fermentation process by Tricine SDS-PAGE, it was found that the haze-active proteins were mainly derived from rice and wheat koji. The haze-active proteins were difficult to degrade by microorganisms during fermentation and existed throughout the whole fermentation process.
Evaluation of Muscle Nutritional Value and Differences in Main Flavor Substances of Pseudosciaena crocea in Two Cultivation Modes
ZHANG Yanxia, XIE Chengmin, ZHOU Fen, ZHANG Ling, JIANG Jiwei, WANG Yueke, WANG Xichang
2020, 41(8):  220-227.  doi:10.7506/spkx1002-6630-20190513-133
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The nutritional components of the muscle of Pseudosciaena crocea cultured in traditional net cages or seine net cages were analyzed by routine methods. The volatile flavor compounds were determined by headspace solid phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS). Relative odor activity (ROAV) was calculated and used in combination with sensory threshold and odor characteristics to determine the main flavor substances and overall odor profiles. The results showed that the contents of water and protein were higher in P. crocea cultured in seine net cages while crude fat content was higher in those cultured in traditional net cages, but there was no significant difference in ash content. The total amount of amino acids in P. crocea cultured in traditional net cages (68.83 mg/g) was slightly higher than that in P. crocea cultured in seine net cages (67.93 mg/g). For the two culture modes, the essential amino acids in P. crocea muscle accounted for 40.96% and 40.95% of the total amino acids, respectively. Amino acid score (AAS) and chemical score (CS) values of P. crocea muscle were both higher than 1 for each culture mode. The essential amino acid index (EAAI) of P. crocea cultured in traditional net cages was higher than 2.47. Umami and sweet amino acids were the main flavor amino acids for the two culture modes. The relative contents of unsaturated fatty acids were as high as 65.47% and 62.75% for P. crocea cultured in traditional net cages and seine net cages, respectively, and the content of EPA + DHA was 18.39% for P. crocea cultured in seine net cages, higher than that of P. crocea cultured in traditional net cages. In total, 48 and 42 volatile components were detected for the two culture modes, respectively. The key flavor substances identified were aldehydes, alcohols and aromatic substances. P. crocea cultured in traditional net cages possessed a strong fishy, rancid and grassy flavor, while those cultured in seine net cages had a strong mushroomy, fatty and fruity flavor.
Analysis of Nutritional Components and Comprehensive Quality Evaluation of Citrus Fruit from Eleven Varieties
LI Xunlan, HONG Lin, YANG Lei, WANG Wu, HAN Guohui, NONG Jiangfei, TAN Ping
2020, 41(8):  228-233.  doi:10.7506/spkx1002-6630-20190526-307
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This study aimed to explore the characteristics of main nutrient contents in citrus pulp from different verities and to develop a comprehensive evaluation method for citrus fruit quality. A comparative analysis of the contents of 20 phenolic substances in fruit pulp and eight conventional fruit quality indicators was carried out among 11 varieties. Factor analysis was applied to comprehensive quality evaluation. The results showed that hesperidin as the major flavonoid and ferulic acid as the chief phenolic acid were detected in the pulp of all these varieties. Five cultivars of sweet orange (Citrus sinensis L. Osbeck) were richer in vitamin C and sinapic acid than six mandarin cultivars (C. reticulata Blanco). The total contents of phenolic compounds in pulp of the mandarin cultivars Gold Nugget and Shasta Gold were the highest among the 11 citrus varieties. The comprehensive quality of sweet oranges was generally better than that of mandarins. The comprehensive quality of the five new mandarin cultivars was better than that of the major cultivar W · Murcott, and the comprehensive quality of the four new sweet orange cultivars were poorer than that of the major cultivar Newhall. Overall, our results demonstrated that the contents of flavonoids and phenolic acids in pulp were important indicators of fruit quality. The comprehensive evaluation of citrus fruit quality by factor analysis could provide a basis for selecting citrus varieties with high quality.
Determination of the Characteristic Aroma Components at Different Fermentation Stages of Zhejiang Rosy Vinegar
FANG Guanyu, JIANG Yujian, MU Xiaojing, SHI Si
2020, 41(8):  234-242.  doi:10.7506/spkx1002-6630-20190411-158
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In this study, response surface methodology was used to optimize the solid-phase micro-extraction conditions of volatile components from Zhejiang rosy vinegar. The optimal conditions were determined as follows: NaCl amount 2.4 g, extraction temperature 49.6 ℃, and extraction time 44.4 min. The volatile components during the fermentation process of Zhejiang rosy vinegar were determined under the optimized extraction conditions. The obtained data were analyzed by principal component analysis (PCA), systematic clustering analysis (SCA) and partial least square discriminant analysis (PLS-DA). PCA and SCA divided Zhejiang rosy vinegar samples into three categories: early, middle and late fermentation. PLS-DA analysis showed that the samples at the three fermentation stages could be well separated from each other based on the volatile components with R2Y = 0.994, and Q2 = 0.933, indicating that the developed model has good stability and extremely strong prediction ability. By PLS-DA analysis, the volatile components with variable importance in the projection (VIP) values larger than 1 were obtained. According to the PLS-DA factor loading plot, the characteristic aroma components at the early stage were ethanol, ethyl dodecanoate and 2-phenylethanolacetate; the characteristic aroma components at the middle stage were propionic acid-2-phenyl ethyl, cyclohexyl propionate, n-propanol, n-propyl acetate, isoamyl acetate, decanoic acid, ethyl acetate, ethyl phenylacetate, lauric acid, 2-ethylbutyrate, 3-methyl phenyl ester and ethyl oleate; and the characteristic aroma components at the late stage of fermentation were (E)-9-octadecanoic acid ethyl ester, ethyl octadecanoate, benzaldehyde, 4-ethyl phenol, diethyl succinate, ethyl hexadecate, furfural, acetate-2-ethylhexyl ester, phenyl ethanol, 2-methylpropionic acid, and 3-hydroxy-2-butanone.
Fingerprint Analysis of Volatile Organic Compounds in Coffees from Different Geographical Origins by Headspace-Gas Chromatography-Ion Mobility Spectrometry
HONG Zishan, TAN Chao, MIAO Yue, GONG Jiashun
2020, 41(8):  243-249.  doi:10.7506/spkx1002-6630-20190516-186
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In this study, the volatile organic compounds (VOCs) in coffee beans from 8 different geographical origins in the world were fingerprinted by headspace-gas chromatography-ion mobility spectroscopy (HS-GC-IMS). We compared the differences in the VOC fingerprints of these coffee samples using matching matrix and clustering analysis, and we investigated the changes in the VOC fingerprints before and after roasting in the form of data visualization. The results showed that for both raw and roasted coffee powders there were differences in VOCs among geographical origins and there were differences in VOCs between raw and roasted coffee powders from the same geographical origins. According to the fingerprint analysis, three-dimensional principal component analysis (3D-PCA) and matching matrix analysis, when the matching degree was 90%, the differences in the subtle characteristic components in the fingerprints could accurately distinguish raw from cooked coffee powders and discriminate the geographical origins. In conclusion, HS-GC-IMS provides a useful tool for identifying the varietal and geographical origin of coffee beans.
Application of High Performance Liquid Chromatographic Phenolic Compound Fingerprint in Quality Control of “Hongyingzi” Sorghum Raw Material
NI Derang, YE Xingqian, LIN Lin, SUN Chongde, KONG Xiangli, WANG Heyu, WANG Li
2020, 41(8):  250-255.  doi:10.7506/spkx1002-6630-20191008-043
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This study aimed to establish a characteristic high performance liquid chromatographic (HPLC) fingerprint for the sorghum cultivar “Hongyingzi” based on phenolic compounds. A total of 17 “Hongyingzi” sorghum samples collected from Renhuai and surrounding regions in Guizhou and 8 other varieties used for Chinese liquor brewing collected from regions outside Guizhou were fingerprinted by HPLC. The chromatographic conditions were set as follows: gradient elution using 0.1% formic acid aqueous solution as mobile phase A and acetonitrile as mobile phase B, column temperature 25 ℃, flow rate 0.5 mL/min, and detection wavelength 288 nm. Common peaks found in all the fingerprints were used to evaluate the similarity among these samples and they were analyzed by cluster analysis and principal component analysis. Results indicated that all the “Hongyingzi” sorghum samples showed high similarities over 0.97 under the common pattern while the similarities among the other sorghum samples were lower than 0.90. In the cluster analysis and principal component analysis, the “Hongyingzi” sorghum samples were mostly clustered into one category at a discriminant distance of 5 and were distinguished from the other varieties. The established HPLC fingerprinting method was a convenient and efficient method to identify “Hongyingzi” sorghum from the other varieties and for quality control of “Hongyingzi” sorghum.
Processing Technology
Preparation and Structural Characterization of Bovine Bone Polypeptide-Calcium Chelate
GAO Min, WANG Jianming, ZHEN Linghui, YU Jinghua, ZHANG Weiwei
2020, 41(8):  256-261.  doi:10.7506/spkx1002-6630-20181217-183
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This study aimed to produce calcium supplements that can be efficiently absorbed and utilized by the human body with high bioavailability in order to improve the utilization of bovine bone. The laboratory-made bovine bone polypeptide was subjected to calcium chelation. The preparation process was optimized based on the chelation rate and calcium content. Ultraviolet absorption spectroscopy, fluorescence spectroscopy, infrared spectroscopy, scanning electron microscopy, particle size and stability analysis were used to compare the changes before and after the reaction. The results showed that the optimum preparation conditions were as follows: mass ratio between peptide and calcium 2:1, reaction temperature 60 ℃, reaction time 40 min, and pH 8.0. Under these conditions, the chelation rate was 38.97% and the calcium content was 21.29%. Spectroscopic analysis showed that amino and carboxyl groups were involved in the chelation reaction, and the coordination reaction mainly occurred between them; scanning electron microscopy showed that the molecules were aggregated during chelation, making their structures more compact. Taken together, a novel peptide-calcium chelate with potential health benefits was formed.
Potassium Ethanolate-Catalyzed Preparation of Conjugated Linoleic Acid Ethyl Ester from Safflower Seed Oil Ethyl Ester and Its Structural Characterization
BI Yanlan, ZHANG Feihong, XU Guangwei, LIU Wei, YANG Guolong
2020, 41(8):  262-269.  doi:10.7506/spkx1002-6630-20190415-192
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In this paper, the effects of reaction temperature, reaction time and the amount of potassium ethanolate as catalyst on the purity and yield of conjugated linoleic acid ethyl ester (CLAEE) prepared from safflower seed oil ethyl ester were investigated. The main physicochemical indicators, fatty acid composition, and structure of CLAEE were determined. CLAEE meeting the market requirements was prepared under the following optimized conditions: reaction temperature 110 ℃, catalyst amount 5% (m/m), reaction time 3 h, vacuum degree ?0.1 MPa, and rotation speed 60 r/min. The content of active conjugated linoleic acid ethyl ester in the product was (75.44 ± 1.18)%, and the content of double trans conjugated linoleic acid ethyl ester was (0.24 ± 0.09)%. The yield of the product was (69.50 ± 3.09)%. The total yield of CLAEE and conjugated linoleic acid was 90%. The structure of the CLAEE product was characterized by infrared spectroscopy (IR), UV absorption spectroscopy, gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR). It was verified to contain four isomers, namely c9,t11-CLAEE, t10,c12-CLAEE, t9,t11-CLAEE and t10,t12-CLAEE, the main ones being active conjugated ethyl linoleate, namely c9,t11-CLAEE and t10,c12-CLAEE.
Safety Detection
Fluorescence Detection of the Spoilage of Fresh-Cut Lotus Roots
LIU Yongle, TANG Qian, YU Jian, LIU Xiaofang, CHEN Shanhui, LI Yan, WANG Faxiang
2020, 41(8):  270-274.  doi:10.7506/spkx1002-6630-20191017-166
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In order to overcome the disadvantages of the traditional microbial hygiene indicator tests, a fluorescence method based on spoilage indicator bacteria for determining the spoilage of fresh-cut lotus root products was developed. The samples were refrigerated at 4 ℃. Total colony count (TCC) and the fluorescence of the indicator bacteria were measured at 3 d intervals, and their correlation was analyzed. The optimum conditions for fluorescence detection were also studied. The results showed that the TCC of the samples stored for 6 d was 6.4 × 104 CFU/g, indicating spoilage. The fluorescence of the suspension culture of lotus roots was detected starting from the sixth day, suggesting that the time point of fluorescence detection and spoilage were consistent. The fluorescence intensity detected with confocal laser scanning microscope showed an increase with storage time but a decrease with the dilution of the suspension, indicating a positive correlation between the fluorescence intensity and the number of microorganisms. Finally, the optimal conditions for this fluorescence method were determined as follows: 10-fold dilution of the suspension, and inoculum volume 5 μL. The accuracy of this method was up to 90% when it was verified with 10 randomly selected samples. It proved to be a simple and convenient method.
Differentiation between Authentic and Adulterated Ziziphi spinosae Semen by 1H NMR Spectroscopy Combined with Partial Least Squares
SHEN Chenxi, DU Chenhui, LI Zhenyu, LI Aiping, QIN Xuemei, YAN Yan
2020, 41(8):  275-281.  doi:10.7506/spkx1002-6630-20190314-180
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In the present study, the chemical composition of pure powders of Ziziphi spinosae Semen (ZSS) and Ziziphi mauritianae Semen (ZMS) and their mixtures in different proportions was compared by 1H nuclear magnetic resonance (1H NMR)-based metabolomic fingerprinting. Then the obtained spectral data were analyzed by multivariate analysis to develop a new method for rapid detection of ZSS adulteration. Principal component analysis (PCA) performed on the 1H NMR data revealed that only a few samples at low adulteration ratios were overlapped with ZSS. In addition, the data were also analyzed by partial least squares-discriminant analysis (PLS-DA). A clear separation was seen between ZSS and 40% adulterated samples. Then a PLS model was established based on the 1H NMR data and was applied to detect adulteration in ZSS falsified by intentional addition of different concentrations of ZMS, and a quantitative calibration model was established. The PLS regression approach provided a highly reliable and accurate prediction model. The results demonstrated that 1H NMR spectroscopy coupled with PLS is a fast and effective technique for checking adulteration in ZSS. Meanwhile, the method provides a potential tool for quality control of ZSS.
Speciation and Distribution Characteristics of Cadmium and Arsenic in the Edible Tissues of Oratosquilla oratoria
ZHAO Yanfang, KANG Xuming, NING Jinsong, ZHAI Yuxiu, SHANG Derong, DING Haiyan, SHENG Xiaofeng
2020, 41(8):  282-287.  doi:10.7506/spkx1002-6630-20190119-229
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The present study was aimed to investigate the distribution characteristics and speciation of cadmium and arsenic in the edible tissues of Oratosquilla oratoria. The contents of total arsenic and cadmium and their species in the edible muscle and gonad were measured by using inductively coupled plasma mass spectrometry (ICP-MS). The free inorganic Cd2+ and different species of arsenic were analyzed with the high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS). The results showed that O. oratoria could accumulate high concentrations of cadmium in the edible tissues, and the concentration of total cadmium in all samples collected in the present study exceeded the maximum permissible concentration (MPC) of 0.50 mg/kg wet mass in China. In addition, the concentration of total cadmium was not significantly related to gender. The concentration of total cadmium in the gonad was almost 10 times as high as that in the muscle. Speciation analysis showed that the percentage of the most toxic free inorganic Cd2+ in relative to the total cadmium was below 20% for most of the samples, and there was a significantly positive relationship between the inorganic Cd2+ concentration and the total cadmium concentration. The total arsenic concentration in the edible tissues of O. oratoria was high regardless of gender. However, the concentration of total arsenic in the gonad was higher than that in the muscle. Inorganic arsenic was detected in all samples, and monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) were also found in some of the samples. The highest concentration of inorganic arsenic of 0.46 mg/kg was found in the muscle, which was below the maximum standard limit in our country, and the percentage of inorganic arsenic in relative to total arsenic in the muscle ranged from 1.71% to 6.14%. In addition, there was no significant relationship between inorganic arsenic and total arsenic for both the edible tissues examined. The organic arsenic AsB was the main species present in both the muscle and gonad of O. oratoria. Because of the high accumulation capacity for total cadmium and arsenic, it is urgent to establish a more accurate MPC of Cd for the edible tissues of O. oratoria. The metal bio-accessibility and bioavailability must be considered in order to improve the risk assessment analysis.
Simultaneous Determination of Residues of 38 Pesticides in Fruits by QuEChERS Combined with High Performance Liquid Chromatography-Tandem Mass Spectrometry
LIANG Xiumei, ZHANG Weiyi, ZHANG Wei, XIE Shibing, HE Ruyi, XU Jing, SU Laijin, SUN Bolun, ZHANG Jing
2020, 41(8):  288-296.  doi:10.7506/spkx1002-6630-20191018-199
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A method for the determination of the residues of 38 pesticides in fruits was established. After being ground, the pesticide residues in samples were extracted with 1% acetic acid-acetonitril and dehydrated with anhydrous magnesium sulfate. Then, the pesticide residues in the supernatant were cleaned up with octadecylsilane (C18), primary secondary amine (PSA) and diatomite before being subjected to high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) analysis. The separation was performed on an Accucore aQ column. The electrospray ionization mass spectrometry was operated in the positive mode using multiple reaction monitoring (MRM) and the analytes were quantified by the external standard method. The results indicated that the limits of detection (LODs) for all the pesticides were in the range of 0.3–26.2 μg/kg, and the limits of quantitation (LOQs) ranged from 0.6 to 52.4 μg/kg. The correlation coefficients (R) of the calibration curves were in the range of 0.999 5–0.999 9. The average recoveries at three spiked levels ranged from 70.1% to 119.3% (n = 6) with relative standard deviations (RSDs) of 2.7%–12.4%. The method was rapid, sensitive and precise, and could provide technical support for the determination of pesticide residues in fruits.
Quantitative and Qualitative Determination of Illicit Sildenafil in Health Foods by Surface Enhanced Raman Spectroscopy
HU Jiayong, ZHANG Man, PI Jiangyi, PENG Qingzhi, FENG Hao, ZHOU Taohong
2020, 41(8):  297-302.  doi:10.7506/spkx1002-6630-20190103-031
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In this paper, a method was established for the qualitative and quantitative determination of illicit sildenafil in health foods by surface enhanced Raman spectroscopy. By taking advantage of the specificity of Raman spectrum, we qualitatively determined sildenafil. Melamine was used as an internal standard to quantify sildenafil. Linear regression fitting was carried out using the peak height ratio between sildenafil at 1 234 cm-1 and melamine at 707 cm-1 as the y axis and sildenafil concentration as the x axis. Results indicated that a good linear relationship was observed in the concentration range of 0–50 mg/L with a correlation coefficient of 0.996 9. The limit of detection (LOD) was 0.05 mg/L, and the limit of quantitation (LOQ) was 5 mg/L. The recoveries of spiked solid and liquid samples were 85.6%–92.6% and 98.7%–105.2%, separately with relative standard deviations (RSD) of 4.14% and 3.25%, separately. In addition, this method was used to detect actual samples, and the results were basically consistent with those obtained by high performance chromatography-mass spectrometry (HPLC-MS). This method is accurate, sensitive and rapid, and can be used for the qualitative and quantitative detection of illicit sildenafil in health foods.
Effects of Black Spot Disease on Nutritional Composition of Red Jujubes Grown in Xinjiang
FAN Yingying, HU Dongqiang, ZHANG Ruili, LI Xiaolong, HE Weizhong, HUA Zhenyu, LI Jing, WU Aibo, WANG Cheng,
2020, 41(8):  303-307.  doi:10.7506/spkx1002-6630-20190610-095
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In order to study the changes of the nutrients in red jujubes after being infected with black spot disease, we analyzed 14 infected and healthy jujube samples collected from 7 jujube orchards in South Xinjiang for 31 nutritional components (sugars, amino acids, total acid, total sugar, reducing sugars, proteins and mineral elements) and four main toxic metabolites (Alternaria toxins). Results showed that the contents of 7 mineral elements were decreased significantly in infected jujubes as compared with healthy ones. Among the 17 amino acids detected, the contents of 8 bitter amino acids (Val, Iie, Leu, Tyr, Phe, His, Lys, and Arg) were all increased while one sweet amino acid, Pro, was significantly decreased. The contents of fructose, sucrose, reducing sugar, total sugar, total acid and water-soluble protein were significantly reduced, whereas glucose content was increased. Tenuazonic acid (TeA), the most toxic among the four metabolites, was detected in all samples, at a significantly lower level in health jujubes than in infected ones. In addition, by partial least squares discriminant analysis we found that alternariol (AOH), aspartic acid, methionine, TeA and lysine could act as main indicators to distinguish between healthy and infected jujubes. This research provides novel ideas for future metabolomics research of red jujubes infected with black spot disease.
Determination of 3-Monochloro-1,2-propanediol and Its Fatty Acid Esters in Chinese Dishes
ZHANG Jinglin, LIU Tingzhu, HUANG Mingquan, SUN Baoguo
2020, 41(8):  308-320.  doi:10.7506/spkx1002-6630-20181217-182
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This study aimed to investigate the ranges of 3-monochloro-1,2-propanediol (3-MCPD) and its fatty acid esters concentrations in the Chinese diet in order to offer supporting data to establish a maximum tolerable daily intake for 3-MCPD in China. The research objects in this study were 39 Chinese dishes. In this method, sulfuric acid methanol was used as ester cleavage reaction of chloropropanol esters, and then the extracts were derivatized with heptafluorobutyrylim idazole (HFBI) and analyzed with gas chromatography-tandem mass spectrometry (GC-MS/MS). Good linearity was obtained with correlation coefficients from 0.997 2 to 0.999 5. The spiked recoveries were in the range of 95.0%–115.0%, with relative standard deviations (RSDs) ranging from 2.9% to 6%. The results showed that both 3-MCPD and its esters were found in all dishes analyzed. The average concentrations of 3-MCPD esters and 3-MCPD were 516.11 and 17.88 μg/kg in restaurant dishes, and 75.86 and 10.43 μg/kg in school canteen dishes, respectively. Difference cooking methods had different influences on the generation of 3-MCPD and its esters, in decreasing order of importance: deep frying > griddling > stir frying > braising > stewing. The concentration of 3-MCPD in both canteen and restaurant dishes did not exceed the provisional maximum tolerable daily intake (PMTDI) established by the Joint FAO/WHO Expert Committee on Food Additives (JECFA), and the concentration of 3-MCPD esters in canteen dishes did not exceed the PMTDI either, while that in restaurant dishes was 2.2 fold higher than the PMTDI.