Table of Content

25 August 2022, Volume 43 Issue 16
Food Chemistry
Preparation and Rheological Properties of Konjac Glucomannan/Surface Deacetylated Chitin Nanofiber Composite Gels
JIANG Haixin, HUANG Yequn, ZHENG Pingyun, ZHAO Jianbo, DUAN Mengxia, PANG Jie, WU Chunhua
2022, 43(16):  1-8.  doi:10.7506/spkx1002-6630-20210717-200
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The microstructure and properties of composite gels prepared from konjac glucomannan (KGM) and surface deacetylated chitin nanofibers (S-ChNF) at different concentrations were studied. The results showed that the KGM/S-ChNF composite gel was a pseudoplastic fluid with shear thinning nature, which conformed to the power law model. With increasing S-ChNF concentration, the gel’s viscosity increased, its shear stress decreased, its viscosity coefficient increased from 23.174 Pa·sn to 29.950 Pa·sn, and its flow index decreased from 0.436 63 to 0.413 08, indicating enhanced pseudoplasticity. Dynamic viscoelastic analysis showed that both the storage and loss moduli were dependent on angular frequency, and displayed an increasing trend with increasing S-ChNF concentration. In addition, the crossing point moved from 6.77 s-1 to 3.77 s-1, indicating that the intermolecular hydrogen bonding was enhanced, increasing the resistance to KGM molecular chain movement and prolonging the relaxation time. Consequently, the gel tended to be an elastic fluid. The results of Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and thermogravimetric analysis showed that increasing S-ChNF content could enhance the intermolecular interaction in the composite system, leading to the formation of a stable network structure, thus improving the rheological properties and enhancing the thermal stability of the composite gel.
Preparation and Characterization of Glabridin/Cyclodextrin Solid Inclusion Complex
YAO Peipei, FAN Jinling, LI Defeng, ZHANG Xiaoyu, REN Guoyan, DU Lin
2022, 43(16):  9-18.  doi:10.7506/spkx1002-6630-20210901-006
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In order to select a suitable cyclodextrin (CD) for the inclusion complexation of glabridin (GLD), the inclusion capacity of different CDs for GLD was studied by molecular docking and phase solubility method. The effects of different drying methods and GLD/CD ratios on the inclusion rate, drug loading and solubility of solid inclusion complexes were investigated. The morphology of inclusion complexes, the existing form of GLD in inclusion complexes, the interaction between GLD and CD and the spatial conformation of inclusion complexes were investigated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy and molecular docking, respectively. The dissolution properties of GLD before and after inclusion complexation were investigated by in vitro dissolution experiments. Methylthiazolyl tetrazolium (MTT) assay was used to compare the inhibitory effect of GLD and its inclusion complexes on the proliferation of human hepatoma cell line (HepG-2). The results showed that various CDs could form 1:1 inclusion complexes with GLD, and 2-sulfobutyl-β-CD (2-SBE-β-CD) had a better capability to include GLD than other CDs and their derivatives. There was no significant difference in the inclusion rate or drug loading of GLD/2-SBE-β-CD solid inclusion complexes prepared by different preparation methods, but the water solubility of the inclusion complexes was different. Appropriately increasing the ratio of GLD to 2-SBE-β-CD reduced the inclusion rate to a certain extent but significantly increased the drug loading. The inclusion rate and drug loading of the GLD/2-SBE-β-CD solid inclusion complex prepared with a 1.5:1 molar ratio between GLD and 2-SBE-β-CD by freeze-drying method were 86.09% and 22.39%, respectively. The saturated solubility of the inclusion compounds prepared with a 1:1 molar ratio between GLD and 2-SBE-β-CD by freeze-drying, spray-drying and kneading were all greater than 83 mg/mL. These inclusion complexes had significantly different morphology, but GLD existed in an amorphous structure in all of them. However, there was no significant difference in the dissolution properties of the inclusion complexes. The cumulative dissolution rates of the GLD/2-SBE-β-CD inclusion complexes in gastric and intestinal fluid were significantly higher than that of GLD and its physical mixture with 2-SBE-β-CD. The GLD/2-SBE-β-CD inclusion complexes had significantly enhanced anti-proliferative activity on HepG-2 cells compared with GLD/H2O. The results of this study confirm that the superiority of 2-SBE-β-CD as a GLD carrier is expected to broaden the application of GLD in food, health products and other fields.
Effect of Baking Soda on the Cooking and Eating Quality of Brown Rice
ZHANG Yili, MEI Dongxu, LI Hang, HAN Wenfang, YANG Ying, LI Jiangtao, XIA Xu
2022, 43(16):  19-25.  doi:10.7506/spkx1002-6630-20210904-047
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The effects of different concentrations of baking soda solution on the cooking characteristics of brown rice including visual appearance, microstructure, color, texture characteristics of cooked rice, and the distribution of branched chain length of amylopectin in rice soup were investigated. The results showed that baking soda solution could make brown rice cortex shrunk or ruptured, increase the water absorption and the expansion rate of rice grains from 10.03% and 212.30% to 15.32% and 224.50%, respectively. Thus, the cooking time of brown rice significantly reduced. Compared with cooked brown rice without baking soda, the surface structure of cooked brown rice with baking soda was more seriously wrinkled and cracked, the degree of whitening increased and the yellow color was deeper. Moreover, the proportion of B2, B3 and A chains of amylopectin in rice soup decreased from 7.834, 2.458 and 24.922 to 6.81, 1.893 and 24.036, respectively. The hardness of brown rice decreased from 1 270.76 g to 983.72 g, and the viscosity increased from 85.79 g·s to 113.71 g·s. The overall sensory score increased, and the eating quality significantly improved. Therefore, adding an appropriate concentration of baking soda in brown rice during cooking can significantly improve the cooking and eating quality of brown rice.
Alkaline Salts to Preserve and Improve the Quality of Fresh Wet Noodles
TIAN Yu, LIU Boye, CHEN Fusheng, CAO Han
2022, 43(16):  26-35.  doi:10.7506/spkx1002-6630-20210927-328
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In order to explore the effects of alkaline salts on the shelf life and quality characteristics of fresh wet noodles, five alkaline salts (sodium carbonate, potassium carbonate, trisodium phosphate, tripotassium phosphate and sodium bicarbonate) at different addition levels were used to make noodles. The optimal addition level of each alkaline salt was determined based on the total plate count, L* value and apparent quality of fresh wet noodles. The effects of the alkaline salts on the quality of fresh wet noodles were comprehensively analyzed by measuring the pH, cooking quality and microstructure of raw noodles and the texture characteristics and sensory quality of cooked noodles as well as the rheological properties of dough. The results showed that compared with the control group, the addition of alkaline salts effectively inhibited microbial growth in fresh wet noodles. Adding 2.0% of sodium carbonate prolonged the shelf life of fresh wet noodles by 2.5 times. The alkaline salts resulted in a bright yellowish color and significantly improved the apparent quality of noodles. The optimum addition level of sodium carbonate in fresh wet noodles was 1.0%, and the optimum addition level of the other four alkaline salts was 1.5%. The alkaline salts regulated and stabilized the pH of noodles during storage, significantly enhanced the water absorption and tensile properties of dough, and reduced the weakening degree of dough; the extensibility of dough with added alkaline salts decreased with proofing time. In addition, the addition of alkaline salts increased the cooking loss, reduce the water absorption, and improve the hardness, tensile strength, elasticity, viscosity and palatability of noodles. Scanning electron microscopy (SEM) showed that the addition of alkaline salts enhanced the degree of cross-linking of protein and starch in noodles, thereby resulting in the formation of a more continuous and dense gluten network structure. Among the alkaline salts, sodium carbonate has the most prominent effect on improving the quality of fresh wet noodles.
Polyphenols from Thinned Young Kiwifruits Improved Meat Quality and Delayed Lipid Oxidation in Goat Meat under Repeated Freeze-Thaw Treatments
ZHANG Duoduo, LIU Yongfeng, GU Minghui, YANG Zesha, ZHANG Haoyang
2022, 43(16):  36-45.  doi:10.7506/spkx1002-6630-20211009-074
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Repeated freezing and thawing can cause the deterioration of goat meat quality. This study was designed to investigate the effect of thinned kiwifruit polyphenols in delaying lipid oxidation and improving the quality of goat meat. Goat meat was soaked in separate aqueous solutions of thinned kiwifruit polyphenols, epicatechin and tert-butyl hydroquinone (TBHQ), and then was frozen-thawed once, three or five times. The drip loss, microstructure, physical properties, pH, color, myoglobin oxidation state, thiobarbituric acid reactive substances (TBARS) value, total volatile base nitrogen (TVB-N) and fatty acid contents of goat meat were determined. The results showed that the drip loss rate increased with increasing number of freeze-thaw cycles, and the drip loss rate of the thinned kiwifruit polyphenol group was significantly reduced by 17.57%, 16.83% and 40.10% respectively compared with the epicatechin, TBHQ and blank groups (P < 0.05) after five freeze-thaw cycles. During freeze-thaw cycles, thinned kiwifruit polyphenols could maintain the integrity of the muscle fiber structure and slow down the excessive decrease in the hardness of goat meat (P < 0.05). The pH decreased with the number of freeze-thaw cycles, and the pH of the thinned kiwifruit polyphenol group was significantly 4.55% higher than that of the epicatechin group (P < 0.05). The a* value and the xymyoglobin content decreased with increasing freeze-thaw cycles, while the relative content of metmyoglobin decreased first and then increased. After five freeze-thaw cycles, the thinned kiwifruit polyphenol group showed the lowest metmyoglobin level (34.01%). The TBARS value showed an upward trend with increasing freeze-thaw cycles. The TBARS value of the thinned kiwifruit polyphenol group was significantly 11.92%, 16.12% and 28.21% lower than the epicatechin, TBHQ and blank groups (P < 0.05) after five freeze-thaw cycles, respectively (P < 0.05). As the number of freeze-thaw cycles increased, the relative content of saturated fatty acids (SFA) decreased; the relative content of monounsaturated fatty acids (MUFA) showed an upward trend, while the relative content of polyunsaturated fatty acids (PUFA) remained stable. The relative content of MUFA in the fruit thinned polyphenol group reached the highest value (56.59%) after three freeze-thaw cycles. The TVB-N value of goat meat in the four groups increased with increasing freeze-thaw cycles. During the freeze-thaw period, the TVB-N value of the thinned kiwifruit polyphenol group was significantly lower than that of the other three groups (P < 0.05). It can conclude that thinned kiwifruit polyphenols can improve the quality of goat meat and delay lipid oxidation.
Rheological Properties and Microstructure of Peanut Protein-Pectin Composite Emulsion Gels
DING Ling, TANG Yihua, ZHANG Lifen, CHEN Fusheng, LAI Shaojuan
2022, 43(16):  46-52.  doi:10.7506/spkx1002-6630-20211014-136
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This study investigated the effects of different types and concentrations of oil phase on the texture properties of peanut protein-pectin composite emulsion gels induced by transglutaminase (TG), and it explored the gel formation mechanism by rheological?measurements?and?microstructural?analyses. The results showed that the gel strength of the peanut protein-pectin composite emulsion gels was significantly higher than that of the hydrogel. According to the appearance and the storage modulus (G’), the oil droplets interacted mechanically with the protein-pectin gel matrix, thereby affecting the texture and gel strength of the emulsion gels. Increasing oil phase concentration enhanced the mechanical properties of the emulsion gels and made the network structure more stable. The G’ value and hardness increase with oil phase concentration, indicating that the dispersed oil droplets act as active fillers to interact with the gel matrix. The microstructure of the peanut protein-pectin composite emulsion gel with palm oil at a concentration of 60% (V/V) as the oil phase showed a denser gel network structure.
Mass Transfer Mechanisms for Decolorizing Resin Adsorption of Alkaline Degradation Products of Hexose
LI Wen, JIAO Li, LIAO Chunyu, YU Haiqing, XIAO Yao, XING Weihong, LI Kai, PENG Wenbo
2022, 43(16):  53-60.  doi:10.7506/spkx1002-6630-20211021-227
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Alkaline degradation products of hexose (HADP) were prepared as a representative colorant in remelt syrup to evaluate their adsorption performance onto a decolorizing resin. Four novel phenomenological adsorption mass transfer models, namely, external mass transfer resistance (EMTR), internal mass transfer resistance (IMTR), combined EMTR-IMTR, and adsorption on active sites (AAS), were used to decipher the mass transfer mechanisms for the resin adsorption of HADP. At the initial colorant concentrations of 60, 90, and 120 mg/L, the equilibrium adsorption capacities of the resin for HADP were 190, 270, and 326 mg/g, and the corresponding decolorization rates were 95%, 90%, and 82%, respectively. EMTR combined with IMTR was the rate-limiting step for HADP adsorption onto the resin, and AAS could not be neglected. The dynamic characteristics of HADP adsorption through the liquid film around the resin and the pores inside the resin could be described well using the combined EMTR-IMTR model. The AAS model could accurately calculate the physisorption and chemisorption rates during the whole adsorption process. These models can help provide new insights into the mass transfer behaviors of the adsorption system.
Structural Characteristics and Antioxidant Properties of Polysaccharides from Different Parts of Cowpea
XIN Yue, SONG Xiaoxiao, WANG Yuxiao, NIE Shaoping, YIN Junyi
2022, 43(16):  61-67.  doi:10.7506/spkx1002-6630-20211001-002
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In this study, polysaccharides from the whole seed, cotyledon and hull of cowpea were extracted, isolated and purified, and their structural characteristics and antioxidant activities were compared. The results indicated that the basic chemical composition, monosaccharide composition and molecular mass distribution of the polysaccharides from different parts of cowpea, exhibited both similarities and differences. Structural characteristics of the polysaccharides from the whole seed (VUP) and cotyledon (VUCP) of Vigna unguiculata were similar. The polysaccharide from the hull (VUHP) was mainly composed of pectin, whose molecular mass distribution was more uniform. The antioxidant activity of VUHP was significantly stronger than that of VUP and VUCP, and the scavenging capacity of VUHP against 1,1-dipheny1-2-picryl-hydrazyl (DPPH) radical and 2,2’-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) cation radical?was almost equal to that of vitamin C (VC). In summary, more attention should be paid to seed coat polysaccharides in the research and product development of polysaccharides from cowpea.
Comparative Study on the Characteristics of A1 and A2 β-Casein Yogurt
XU Xiaoshuang, HAN Yiyu, LI Xiaoyao, PENG Qiuqi, LUO Wenjing, YU Jinghua
2022, 43(16):  68-72.  doi:10.7506/spkx1002-6630-20210803-036
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The differences in characteristics between stirred and set yogurt produced from A1 or A2 β-casein milk were studied. The water-holding capacity of stirred and set yogurt produced from A1 β-casein milk was greater than 69%, and the water-holding capacity of stirred and set yogurt produced from A2 β-casein milk was greater than 65%. Textural analysis showed that the hardness and consistency of set yogurt produced from A1 β-casein milk were 41.4% and 59.8% higher than those of set yogurt produced from A2 β-casein, respectively. Compared with A2 β-casein yogurt, A1 β-casein yogurt had better viscosity. The results of rheology and microstructure showed that the hysteresis loop area of A1 β-casein yogurt was 14.6% smaller than that of A2 β-casein yogurt indicating that the former’s structure can be more easily damaged and its network structure is sparser. This study provides theoretical support for the application of A2 β-casein milk in yogurt.
Effect of Ozone Treatment on the Structure and Allergenicity of Milk Whey Protein
XIONG Ziyi, TAN Hongkai, HU Yongxin, WU Yong, CHEN Hongbing, LI Xin
2022, 43(16):  73-80.  doi:10.7506/spkx1002-6630-20211026-292
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In this study, we explored the effect of ozone treatment on the structure and allergenicity of milk whey protein. The changes in amino acid composition, sulfhydryl group and disulfide bond contents of whey protein were measured after ozone treatment for 0, 5, 10, 15, 20 and 25 s. Circular dichroism spectroscopy, ultraviolet spectroscopy and fluorescence spectroscopy were applied for analyzing the structural changes. Finally, the ability to bind to specific antibodies in vitro was determined by indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) to evaluate the potential allergenicity. The results showed that ozone treatment reduced the contents of some amino acids in whey protein. It reduced the contents of free sulfhydryl and total sulfhydryl groups from 5.78 to 2.13 μmol/g and from 14.98 to 12.97 μmol/g, respectively, but increased the content of disulfide bonds from 4.60 to 5.42 μmol/g. Spectroscopic analysis showed that the secondary structure of whey protein was changed. At the early stage of ozone treatment, the tertiary structure became loose, but as the treatment time increased, some protein molecules gathered together and the content of disulfide bonds increased, causing the spatial structure of whey protein to return to its original ordered state. The results of ic-LISA showed that the allergenicity of whey protein decreased significantly after ozone treatment. In conclusion, ozone treatment holds great potential in improving the safety of milk-containing foods.
Effects of Endogenous Polyphenols on the Physicochemical and Functional Properties and Structure of Pine Kernel Proteins
QI Qi, LI Yanxia, YANG Kai, ZHAO Yuhong
2022, 43(16):  81-89.  doi:10.7506/spkx1002-6630-20210510-103
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Protein isolates (PI) were obtained from pine kernel meal (PKM) and dephenolized pine kernel meal (DPKM) by alkali dissolution followed by acid precipitation, and globulin (Glo), albumin (Alb) and gluten (Glu) were prepared from PKM and DPKM by Osborne fractionation method. The effects of endogenous polyphenols on the physicochemical and functional properties and structure of these proteins were explored. It was shown that after the removal of phenolics, the contents of phenolic compounds, ash and carbohydrates decreased, while the protein content significantly increased (P < 0.05). The contents of total and free sulfhydryl groups in the proteins from DPKM were significantly higher than those in the proteins from PKM (P < 0.05), whilst the opposite was observed for the content of disulfide bonds and the surface hydrophobicity. Higher solubility, emulsion stability, foaming capacity and foam stability were observed in the proteins from DPKM, while the emulsifying capacity decreased after the removal of phenolic compounds (P < 0.05). The secondary structure of pine kernel proteins was changed by the removal of polyphenols. Dephenolization could alter the secondary structure of pine kernel proteins. The proteins from both PKM and DPKM had typical absorption peaks, and the positions of the amide I and amide II bands were shifted. In addition, the proportion of β-sheet increased, while the proportions of α-helix, β-turn and random coil decreased in DPKM proteins compared with PKM proteins. Fluorescence spectra showed that polyphenols had a fluorescence quenching effect on PI, Alb and Glu, but not on Glo. The structure and properties of pine kernel proteins can be significantly affected by dephenolization, and this treatment method can be selected according to the application purpose.
Effect of Environmental Conditions on the Stability of β-Carotene Nanoparticles
GUO Jing, SUN Xiaolin, PAN Siyi
2022, 43(16):  90-97.  doi:10.7506/spkx1002-6630-20211007-046
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In this study, a ternary complex of zein with lecithin and propylene glycol alginate (PGA) was prepared by an anti-solvent method and applied to encapsulate β-carotene. The structural properties of β-carotene nanoparticles were studied. Moreover, the influences of environmental conditions such as temperature, pH and light on the stability of β-carotene nanoparticles were investigated. The results showed that compared with zein nanoparticles and zein-lecithin complexes, the ternary complex nanoparticles had a higher encapsulation efficiency for β-carotene (93.63%) and showed good stability against temperature and pH. In addition, the ternary complex was extremely effective in inhibiting β-carotene color degradation caused by exposure to ultraviolet light, keeping the average particle size below 250 nm. Therefore, zein-lecithin-propylene glycol alginate nanoparticles are expected to become an effective carrier for hydrophobic compounds.
Effect of Foxtail Millet Flours with Different Particle Sizes on Rheological Properties of Dough and Texture Characteristics of Steamed Bread
LI Shaohui, SHENG Qinghai, ZHAO Wei, SONG Jianing, LI Pengliang, ZHANG Aixia, LIU Jingke
2022, 43(16):  98-106.  doi:10.7506/spkx1002-6630-20210717-199
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This work was undertaken in order to study the effects of the addition of foxtail millet flour on the rheological properties of dough and the textural properties of steamed bread. The damage starch content and pasting characteristics of waxy and non-waxy foxtail millet flours with different particle sizes were analyzed using a damaged starch tester and a rapid viscosity analyzer. The rheological characteristics of doughs made from blends of wheat and foxtail millet flour were measured using a rheometer and the microstructure was observed using a scanning electron microscope (SEM). The texture characteristics of steamed breads made from wheat-foxtail millet doughs were measured using a texture analyzer. The results showed that the iodine absorption rate of damaged starch increased with decreasing millet flour particle size for most cultivars (except Jigu 39 and Huihua Jinmi). The peak viscosity, trough viscosity, final viscosity and setback value of non-waxy millet flour were larger than those of waxy millet flour at the same particle size, depending on the ratio of amylopectin to amylose. Rheological studies showed that the storage and loss moduli generally increased with increasing angular frequency for most cultivars except Huihua Jinmi and Jigu 39. SEM observation revealed that the addition of millet flour made the dough structure looser. The addition of millet flour negatively affected the hardness, chewiness and springiness of steamed bread to a certain extent. Principal component analysis (PCA) showed that the chewiness of steamed bread and the damaged starch, peak viscosity, trough viscosity, final viscosity, disintegration value and setback value of millet flour are useful indicators to distinguish foxtail millet flours and steamed breads from waxy and non-waxy cultivars.
Effect of Soluble and Insoluble Dietary Fibers from Extrusion Cooked Rice Bran on the Properties of Rice Starch and Their Interactions
WANG Leixin, WU Nana, LÜ Yingguo, TAN Bin
2022, 43(16):  107-113.  doi:10.7506/spkx1002-6630-20210918-231
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The effects of soluble and insoluble dietary fibers from unextruded and extruded rice bran on the pasting properties, thermal properties, retrogradation properties, crystallinity properties and microstructure of rice starch were studied. The interaction between dietary fibers from extruded rice bran and rice starch was investigated by means of texture analysis, nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The results showed that compared with un-extruded rice bran dietary fibers, soluble and insoluble dietary fibers from extruded rice bran significantly increased the breakdown value by 74.09% and 128.36%, respectively, but significantly decreased the peak viscosity, trough viscosity, final viscosity, peak time, and pasting temperature of rice starch. Soluble dietary fibers from extruded rice bran facilitated the transformation of free water into strongly bound water in rice starch gels, while insoluble dietary fibers from extruded rice bran promoted the transformation of free water into weakly bound water. Compared with un-extruded rice bran dietary fibers, soluble and insoluble dietary fibers from extruded rice bran decreased the setback value of rice starch by 62.59% and 44.81%, respectively, and also decreased the retrogradation rate, relative crystallinity, hardness, cohesion, resilience, gumminess, chewiness and ratio between peak heights at 1 047 cm-1 and 1 022 cm-1 of rice starch gels. The surface of starch gels added with extruded rice bran soluble and insoluble dietary fibers was smoother with larger crack, showing that extrusion improved the inhibitory effect of rice bran dietary fibers on the retrogradation of rice starch, and extruded soluble dietary fiber had a more prominent effect than extruded insoluble dietary fibers.
Rheological Properties of Gelatin-Based Emulsion and Its Application in Fried Foods
HU Ludan, DU Jie, PENG Lin, ZHOU Yang, MA Liang, ZHANG Yuhao, WANG Hongxia
2022, 43(16):  114-121.  doi:10.7506/spkx1002-6630-20210616-191
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In this study, we investigated the effect of adding different amounts of gelatin on the rheological properties of emulsions, and conducted a microscopic rheological analysis of the emulsions containing gelatin using mathematical models. Besides, we evaluated the stability of the emulsions using an optical microscope, and explored the application of gelatin-based emulsions in Chinese scallion pancake. It was found that the gelatin-based emulsions were pseudoplastic fluids with shear-thinning nature (n < 1). The emulsions had high viscosity, storage modulus (G’) and loss modulus (G’’), showing a strong network structure. The emulsions had temperature dependence and good thixotropy (recovery rate of 69.6%), indicating high stability. At the same time, the observation by an upright fluorescent microscope showed that the particle sizes of emulsions were small and uniform, further confirming their excellent stability. The texture properties and sensory evaluation scores of fried Chinese scallion pancakes coated with soybean oil and a soybean oil emulsion added with gelatin were compared, revealing that the gelatin-based emulsion could effectively improve the brittleness and chewiness of pancakes. Therefore, gelatin-based emulsions can be used as an alternative to vegetable oil in fast foods.
Effect of Ethanol Extract of Pomegranate Peels on the Oxidative Stability of Frying Oil and Acrylamide Content during Deep Frying of French Fries
QI Daisha, LI Shuyun, ZHANG Qing
2022, 43(16):  122-128.  doi:10.7506/spkx1002-6630-20211024-256
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The effect of adding different concentrations (0.01%, 0.02%, 0.03%, 0.07% and 0.14%) of ethanol extract of pomegranate peel (EEPP) on the oxidative stability of frying oil and the content of acrylamide (AA) during the deep frying of French fries were studied in this work. The results showed that EEPP exhibited a high inhibition rate against 2,2-diphenyl-1-picrylhydrazyl (DPPH) (20%–97%), 2,2’-azinobis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical cation (16%–91%) and ferric reducing power (0.3–8.24 mmol/g), and had a total phenol content of 20.14 mg/g. Addition of 0.14% EEPP was the most effective in delaying the increase in acid value (AV), peroxide value (POV), and total polar component content in frying oil, indicating the highest oxidation stability. Moreover, at this concentration, a good inhibitory effect on AA in French fries and frying oil (with inhibition rate of up to 83%) was also observed. Therefore, EEPP has the potential as a novel antioxidant to delay the oxidation process of frying oil and effectively inhibit the production of AA during the processing of French fries to ensure food safety.
Insight into the Regulatory Mechanism of the Microstructure of Myofibrillar Protein-Konjac Glucomannan Gel Systems on Their Textural Properties
YUAN Huagen, SHI Shuai, XI Zhaoshou, PAN Xuefeng, CHEN Xia, CHEN Yinji
2022, 43(16):  129-134.  doi:10.7506/spkx1002-6630-20210528-342
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In the present study, model gel systems of myofibrillar protein (MP) and various concentrations of konjac glucomannan (KG) were evaluated for textural properties, spatial distribution and MP gel networks using a texture analyzer, the paraffin section method and scanning electronic microscopy (SEM), respectively. The regulatory mechanism of the microstructure of MP-KG gel systems on their textural properties was elucidated in order to provide a theoretical basis for the application of KG as a fat replacer in low-fat sausages. The textural analysis results showed that the fracture stress and fracture strain exhibited a parabolic trend with KG concentration, but they reached their maximum at different KG concentrations. The results of low-field nuclear magnetic resonance (NMR) showed that the shortest relaxation time (274 ms) and highest percentage (92.79%) were observed for immobile water in composite gels with 1% KG, suggesting that KG could promote cross-linking of MP and consequently enhance MP binding to water molecules. Paraffin section showed that the spatial distribution of MP-KG gels was transformed from the “trapped structure” to the “penetrated structure” with increasing KG concentration. The SEM micrographs showed that the MP gel networks in the control group were filled with crisscrossed moisture channels and consequently were loose. Addition of a small amount of KG reduced the cross-linked moisture channels, and promoted the formation of compact and well-aggregated MP gel networks. On the other hand, excess addition of KG resulted in the formation of a continuous phase, damaging the MP gel networks. In conclusion, KG could improve the gel strength through stabilizing the water phase and deteriorate the texture of composite gels through the penetrated structure.
Effects of OVA-GA-DEX Conjugates on Stability and Antioxidant Activity of Resveratrol
MENG Lingli, ZHANG Han, HOU Huijing, ZHANG Xiaoyan, LEI Dandan, ZHAO Pei, HE Yuwei, WU Zijian
2022, 43(16):  135-144.  doi:10.7506/spkx1002-6630-20220320-235
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Ovalbumin-gallic acid-dextran (OVA-GA-DEX) conjugate was prepared by alkali grafting and dry hot Maillard reaction and its physicochemical properties and effects on the stability and antioxidant activity of resveratrol (RES) were analyzed by comparing with those of ovalbumin-gallic acid (OVA-GA) and ovalbumin-dextran (OVA-DEX). Results showed that covalent binding of GA or DEX with OVA could change the secondary structure compositions of OVA and improve its hydrophilicity and emulsification stability. The particle size distribution of three conjugates (OVA-GA, OVA-DEX and OVA-GA-DEX) in the Pickering emulsion was more uniform. OVA-GA-DEX had a smaller average particle size ((85.07 ± 10.74) nm), suggesting its better stability. The encapsulated OVA-GA-DEX can effectively protect RES from oxidation or degradation, and provide RES with higher antioxidant capacity.
Preparation and Characterization of Dihydromyricetin-Loaded Solid Self-Emulsifying Delivery System
HUANG Juan, YUE Jingjing, FENG Xuan, WANG Lizeng, CHU Lanling, XIE Wenjing, ZHANG Jiajing, LÜ Yiwen
2022, 43(16):  145-152.  doi:10.7506/spkx1002-6630-20210905-053
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Dihydromyricetin-loaded solid self-emulsifying delivery system was prepared by the silica particle adsorption method to overcome the problem of the low stability, solubility and bioavailability of dihydromyricetin. When the mass ratio of silica particles to liquid self-emulsifying delivery system was larger than 0.6, a white loose powder was prepared, which had good flowability. The content of dihydromyricetin in the solid self-emulsifying delivery system was (0.30 ± 0.03)%. The X-ray diffraction and infrared spectral results revealed that dihydromyricetin existed in an amorphous or dissolved state in the sample, and that liquid self-emulsifying delivery system was physically adsorbed into the pores of silica. The in vitro release results showed that compared with an ethanol solution of dihydromyricetin, the release time of dihydromyricetin from the liquid and solid self-emulsifying delivery system was prolonged, and the sustained release lasted for more than 8 h. Silica particles inhibited the release of dihydromyricetin to a certain extent. The in vitro simulated digestion experiments showed that the solid self-emulsifying delivery system was mainly digested in the intestinal juice. After self-emulsification, the bioaccessibility of dihydromyricetin increased from about 34.01% to more than 70%, indicating that the self-emulsifying delivery system can improve the intestinal absorption and utilization of bioactive components. Since the liquid self-emulsifying delivery system could not be dissolved or released from the pores of silica particles in time, the bioaccessibility of dihydromyricetin decreased to a certain extent after the liquid self-emulsifying delivery system was solidified. The solidification of silica particles could prolong the digestion and absorption of dihydromyricetin. Moreover, the solid self-emulsifying delivery system could improve the chemical stability of dihydromyricetin.
Effect of pH on the Interaction of Lutein with Bovine Serum Albumin Studied by Fluorescence Spectroscopy
FAN Jinbo, KANG Zhu, ZHANG Yan, SU Dongyu, ZHOU Suzhen, LÜ Changxin
2022, 43(16):  153-159.  doi:10.7506/spkx1002-6630-20211025-269
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The interaction between lutein and bovine serum albumin (BSA) was investigated using fluorescence emission spectroscopy under different pH (3.0, 5.0 and 7.4) conditions. The quenching constant and thermodynamic parameters were calculated using a mathematical model. The fluorescence quenching and conformation changes of BSA were analyzed, and the binding sites were determined by site marker competitive experiments and molecular docking. Fluorescence spectra showed that lutein had a fluorescence quenching effect on BSA under different pH conditions. The quenching constant was the highest and the binding constant was larger at pH 7.4 and 298 K. The thermodynamic parameters and molecular docking showed that the binding of lutein with BSA was mainly driven by hydrophobic interaction. Synchronous fluorescence spectra indicated that lutein and the change of pH jointly induced the conformational changes of BSA. The results of site marker competitive experiments and molecular docking showed that the binding site of lutein and BSA was located between subdomains IIA and IIIA, but closer to Sudlow’s site II at pH 7.4 and 5.2. At pH 3.0, the binding site was neither near subdomain IIA nor near subdomain IIIA. Altogether, the results revealed that pH influenced the binding of lutein and BSA, which may provide a theoretical basis for understanding the interaction between proteins and bioactive components.
Interaction between Tremella fuciformis Polysaccharide and Soybean Protein Isolate: Rheological Properties of Their Mixtures
LONG Hui, LI Yi, ZHU Yeli, TENG Jianwen, XIA Ning
2022, 43(16):  160-168.  doi:10.7506/spkx1002-6630-20210906-077
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In order to study the interaction between Tremella fuciformis polysaccharide (TFP) and soybean protein isolate (SPI), the complex coacervation process between them was characterized by turbidity measurement as well as using a nano particle size analyzer, a laser confocal scanning microscope, a rheometer and Fourier transform infrared (FTIR) spectroscopy. The results showed that pH, the ratio of SPI to TFP and salt concentration had great influence on the formation of coacervates. When the SPI/TFP ratio was larger than 1, the critical pH associated with complex formation (pHc and pHφ1) shifted to higher pH. When the SPI/TFP ratio was less than 1, pHφ1 shifted to a lower level. The maximum absorption peak for turbidity gradually decreased (pHopt gradually decreased) with increasing level of TFP. When the SPI/TFP ratio was 1, the interaction between them was the strongest at pH 3.0, and the viscosity of the system was the largest (1.30 Pa·s). In addition, the largest amount of coacervates was formed with the largest particle size. The formation of SPI-TFP coacervates was promoted by low salt concentrations (c(NaCl) < 20 mmol/L) but inhibited by high salt concentrations (c(NaCl) ≥ 20 mmol/L) due to shielding. When the shear frequency was 10 Hz, the NaCl concentration was 20 mmol/L, and the SPI/TFP ratio of 1:1, the highest viscoelastic modulus was obtained, along with storage modulus of 9.24 Pa and loss modulus of 3.40 Pa. This study may provide a theoretical basis for the application of TFP in plant protein based beverage.
Effect of Synergistic Induction of Transglutaminase and Magnesium Chloride on Gelling Properties of Cold-pressed Soy Flour
WANG Fengqiujie, YANG Xinxin, GU Xuelian, LUAN Binyu, HUANG Yuyang, ZHU Ying, ZHU Xiuqing
2022, 43(16):  169-176.  doi:10.7506/spkx1002-6630-20210806-081
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In this study, we evaluated the effect of synergetic induction of transglutaminase (TGase) and magnesium chloride (MgCl2) on the gel forming properties of cold-pressed soybean flour. The results showed that the dietary fiber content of tofu prepared from cold-pressed soybean flour using MgCl2 or in combination with TGase as a coagulant increased by three times, and the fat content was only one third compared to tofu prepared from tofu prepared from regular soybean flour using MgCl2 as a coagulant (control). Addition of TGase could obviously improve the internal water content of cold-pressed soybean flour gels, making the gel structure more uniform gel, and resulted in higher storage modulus G′ (10 498 Pa), indicating a stronger gel network structure, Consequently, the highest water-holding capacity (51.01%), product yield (244%) and random coil percentage (21.45%) were obtained. The disulfide bond content of tofu coagulated with TGase + MgCl2 (5.46 μmol/g) was close to that of the control sample (7.02 μmol/g). The scanning electron microscopic (SEM) results showed that the synergistic effect TGase and MgCl2 gave a more compact gel network structure, which was close to that in the control sample. Therefore, the synergetic effect of TGase and MgCl2 could improve the gelling properties of cold-pressed soybean meal proteins. The results of this study can provide a theoretical basis for diversified development of cold-pressed soybean powder.
Isolation and Identification of Culturable Microbes during the Fermentation of Liupao Tea
HUANG Ziheng, CHEN Huan, HUANG Li, XIA Ning, TENG Jianwen, WEI Baoyao, CHEN Yu, YU Lian
2022, 43(16):  177-185.  doi:10.7506/spkx1002-6630-20210830-389
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The microbial community structure in Liupao tea at different stages of pile fermentation was studied by traditional microbial isolation and molecular identification. A total of 27 bacteria belonging to 13 genus, 8 actinomycetes species belonging to 7 genus, and 23 fungal species belonging to 11 genera were identified. Aspergillus niger, Aspergillus tubingensis, Blastobotrys adeninivorans and Bacillus spp. were found at all stages of the fermentation process. Totally 22 species of bacteria, 7 species of actinomycetes and 9 species of fungi were reported first in Liupao tea. These findings are helpful to understand the microbial role in the pile fermentation of Liupao tea, and provide a theoretical basis for the pure culture fermentation and microbial safety analysis of Liupao tea.
Hepatic Transcriptomics and Bioinformatics Analysis Reveals that Oleuropein Alleviates Diabetes in db/db Mice
ZHENG Shujuan, XIE Zixin, FANG Jingjing, WANG Yanan, GENG Ruixuan, ZHAO Yuhan, LI Mengjie, TONG Tao, HUANG Kunlun
2022, 43(16):  186-193.  doi:10.7506/spkx1002-6630-20210909-113
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Transcriptomic and bioinformatic analyses were performed to investigate the differentially expressed genes and signaling pathways in the liver related to the role of oleuropein in alleviating type 2 diabetes in db/db mice. The results showed that compared with the db/db control group, 539 genes in the oleuropein treatment group had significant changes, of which 450 genes were significantly up-regulated and 89 genes were down-regulated. The up-regulated and down-regulated differentially expressed genes were annotated in the Gene Ontology database, revealing that they were mainly distributed in cellular processes, cell parts, and binding terms. The results of Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis showed that the up-regulated differentially expressed genes were mainly enriched in the phosphoinositide 3-kinase-protein kinase-B signaling pathway, which involved a total of 27 differentially expressed genes; the down-regulated differentially expressed genes were mainly enriched in arachidonic acid metabolism and ribosomal biogenesis signaling pathways in eukaryotes, which involved four differentially expressed genes, separately. This study lays the foundation for further elucidating the molecular mechanism by which oleuropein alleviates type 2 diabetes.
Purification and Characterization of Dipeptidyl Peptidase-IV from Bovine Kidney
ZHAO Jiani, CHEN Hong, CHEN Yinge, WENG Ling, ZHANG Lingjing, ZHANG Zhigang, LIN Jiashi, CAO Minjie
2022, 43(16):  194-200.  doi:10.7506/spkx1002-6630-20210805-069
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The purpose of this study is to efficiently prepare high-purity dipeptidyl peptidase-IV (DPP-IV) from beef kidney by sequential acid precipitation, ammonium sulfate fractionation and gel filtration chromatography. Under reducing conditions, the molecular mass of the purified protein was estimated to be 106 kDa with a purification fold of 169.9 and a yield of 9.5%. Twelve peptides with a total of 517 amino acid residues were identified from the DPP-IV by mass spectrometry. The matching degree of the 12 peptides with the amino acid sequence of bovine DPP-IV standard was 100%. The DPP-IV was found to be a dimeric glycoprotein (210 kDa), with an isoelectric point of 5.8. The secondary structure of the DPP-IV had a typical β-sheet conformation, and the thermal denaturation temperature was (72.7 ± 0.3) ℃. Metal ions such as Zn2+, Fe2+ and Fe3+ revealed a significant inhibitory effect on the activity of DPP-IV. The inhibition rate of 1 mmol/L Zn2+ on the enzyme’s activity was as high as 98%.
Interaction Mechanism of Wickerhamomyces anomalus and Saccharomyces cerevisiae in Mixed Culture Fermentation
ZHAO Jianlei, QIU Shuyi, WANG Xiaodan, YUAN Meng, ZHOU Hongxiang
2022, 43(16):  201-208.  doi:10.7506/spkx1002-6630-20210902-017
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To evaluate the application potential of Wickerhamomyces anomalus (Wa) K-008 in mixed culture fermentation and its interaction mechanism with Saccharomyces cerevisiae (Sc) ZM-005 in co-fermentation, pure and mixed culture fermentations of the two strains were carried out. The biomass, glucose consumption, ethanol production and fermentation rate were measured during the fermentation process. It was found that after 24 hours of mixed culture fermentation, Wa showed growth arrest and cell death, while the growth of Sc was not significantly affected by the presence of Wa. We preliminarily ruled out that the early death phenomenon was due to Wa autolysis or apoptosis. By analyzing the fermentation supernatant as well as evaluating the ethanol tolerance, we found that the death of Wa at the early stage of fermentation was not due to the lack of nutrients or the toxic effect of Sc. The mixed culture fermentations with high concentrations of viable, broken or dead cells of Sc indicated that cell death in Wa at the early stage was due to the high concentration of live Sc cells in the system but not dead or broken Sc cells. Furthermore, to verify the mechanism of action, the Sc and Wa cells were separated by dialysis to avoid contact between each other. It was found that both Sc and Wa could grow normally in the mixed culture system. In summary, the growth arrest and death of Wa at the early stage of mixed culture fermentation may be caused by the high concentration of live Sc cells through a cell-to-cell contact mechanism.
Screening of Bacteriocin-producing Lactic Acid Bacteria: Isolation and Purification of and Antibacterial Mechanism of Bacteriocin
XU Xiaoyan, PENG Zhen, XIONG Shijin, XIAO Muyan, HUANG Tao, XIONG Tao
2022, 43(16):  209-216.  doi:10.7506/spkx1002-6630-20210902-018
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A strain of lactic acid bacteria (LAB) with an inhibitory effect on Staphylococcus aureus was isolated from naturally fermented pickle. The strain was identified as Lactococcus lactis subsp. lactis and named NCU036018 by 16S rDNA gene sequence analysis and physiological and biochemical experiments. The antibacterial substance in the fermentation supernatant of NCU036018 was sensitive to trypsin, papain, protease K and α-chymotrypsin, but not to pepsine, lipase, amylase or catalase, and retained more than 70% and 90% of its activity at pH 2.0–10.0 and 50–100 ℃, respectively. Then, the antibacterial substance was separated and purified by successive steps of ammonium sulfate salting-out, ultrafiltration and cation exchange chromatography. The obtained bacteriocin was named lactococcin 036018, whose molecular mass and minimum inhibitory concentration (MIC) were 14.4-20 kDa and 0.50 mg/mL, respectively. Lactococcin 036018 could effectively reduce the biofilm formation rate of S. aureus, damage the morphology of the cell surface, reduce the permeability of the cell membrane and consequently inhibit or even killing the cells. The bacteriocin had a significant inhibitory effect on the growth of S. aureus in milk, thereby showing great promise as a food preservative.
Component Analysis
Determination of Trehalulose in Stingless Bee Honey by High Performance Liquid Chromatography with Refractive Index Detector
ZHENG Xing, WANG Kai, XUE Xiaofeng, WANG Zhengwei, PAN Peng, WU Liming, ZHAO Yazhou, PENG Wenjun
2022, 43(16):  217-225.  doi:10.7506/spkx1002-6630-20210520-251
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Objective: This study aimed to establish a high performance liquid chromatography coupled with refractive index detector (HPLC-RID) method for the determination of trehalulose in stingless bee honey, and apply it to actual samples from different stingless bee species, geographic origins, and harvest dates. Methods: We collected stingless bee honey samples produced by different bee species in Yunnan and Hainan as well as Malaysia in 2019–2021 for analysis by HPLC-RID. Results: The samples were dissolved in pure water and filtered through a 0.22 μm nylon membrane. Baseline chromatographic separation of trehalulose from other oligosaccharides in honey was achieved on a Hi-Plex Pb column (300 mm × 7.7 mm, 8 μm) using pure water as the mobile phase. The method had high recoveries (ranging from 93.50%–95.71%, with relative standard deviation (RSD) not larger than 0.61%) and good repeatability and accuracy. The content of trehalulose in stingless bee honey ranged from 7.0% to 30.8%, and varied significantly across harvest years and bee species (P < 0.05). Conclusion: The proposed method is simple, rapid and accurate and can be used for the determination of trehalulose in stingless honey for quality control purposes. Stingless bee honey is rich in trehalulose, which can be a potential quality index for the identification and evaluation of stingless bee honey.
Analysis of Primary Metabolites in Three Plum Varieties Using Ultra-high Performance Liquid Chromatography-Tandem Mass Spectrometry
ZHANG Qin, HUANG Shi’an, LIN Xin, LUO Dengcan, PENG Junsen, ZHU Shouliang, DONG Xiaoqing
2022, 43(16):  226-234.  doi:10.7506/spkx1002-6630-20211009-085
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The primary metabolites in Fengtang, Kongxin and Cuihong plum fruits were qualitatively and quantitatively analyzed by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The differential metabolites among varieties were identified by principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA), and the differential metabolic pathways were analyzed through KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analysis. The results showed that a total of 307 metabolites belonging to 12 categories were detected, including amino acids and derivatives, nucleotides and derivatives, organic acids, sugars, alcohols, and free fatty acids. There were 70 differential metabolites between Fengtang and Cuihong plum, among which, 43 (61.43%) were up-regulated and 27 (38.57%) were down-regulated. Five significantly differential metabolic pathways were recognized, including metabolic pathways, aminoacyl-tRNA biosynthesis, valine, leucine and isoleucine degradation, glucosinolate biosynthesis and lysine degradation. In total, 96 differential metabolites were found between Fengtang and Kongxin plum, of which, 84 (87.50%) were up-regulated and 12 (12.50%) were down-regulated, and only one significantly differential metabolic pathway was identified, namely tryptophan metabolism. A total of 75 differential metabolites were found between Kongxin and Cuihong plum, of which, 19 (25.33%) were up-regulated and 56 (74.67%) were down-regulated, and two significantly differential metabolic pathways were identified, including purine metabolism and glucosinolate biosynthesis.
Differences in Aroma Components of Black Tea Processed from Different Tea Cultivars in Huangshan by Using Headspace-Solid Phase Microextraction-Gas Chromatography-Mass Spectrometry and Odor Activity Value
YANG Jihong, ZHOU Hanchen, LIU Yaqin, WANG Hui, HUANG Jianqin, LEI Pandeng
2022, 43(16):  235-241.  doi:10.7506/spkx1002-6630-20210726-301
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In order to investigate the differences in the aroma composition of black tea samples made from different tea cultivars in the region of Huangshan, fresh leaves of nine tea cultivars widely planted in that region were selected to process black tea, including ‘Keemun Zhuyezhong’, the major cultivar for Keemun black tea processing, and eight clones, namely ‘Cuilv No.1’, ‘Fuzao No.2’, ‘Wancha No.4’, ‘Shuchazao’, ‘Wancha 91’, ‘Zhongcha 108’, ‘Zhenong 117’, and ‘Zhenong 139’. The sensory evaluation results showed that all nine black tea samples had a sweet aroma, and ‘Keemun Zhuyezhong’ black tea also possessed a strong floral scent. ‘Wancha No.4’ black tea also had a lightly floral aroma. The floral aroma of ‘Keemun Zhuyezhong’ and ‘Wancha No.4’ black tea was significantly stronger than that of the other cultivars. Forty-six major volatile compounds were identified by headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS), and 21 volatile components with OAVs greater than one were found. Principal component analysis (PCA) showed that the aroma composition of ‘Zhuyezhong’ and ‘Wancha No.4’ black tea was clearly different from that of the others. Subsequently, seven differential components including (E)-β-ionone, linalool, β-myrcene, geraniol, hexanal, nonanal, and heptanal were identified by orthogonal partial least squares-discriminant analysis (OPLS-DA), with variable importance projection (VIP) values greater than one among all samples. These volatile components may be the dominant factors causing the aroma difference among the nine black tea samples. These results provide insights into the differential aroma compounds among black tea samples manufactured from different cultivars and the ‘Keemun aroma’.
Analysis, Classification and Prediction of Volatile Flavor Components in Milk Powders for Different Age Groups
YE Meixia, LI Rong, JIANG Zitao, WANG Ying, TAN Jin, TANG Shuhua
2022, 43(16):  242-252.  doi:10.7506/spkx1002-6630-20210807-097
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An electronic nose based on ultra-fast gas chromatography (UFGC E-nose) was used to analyze the volatile flavor components of 24 samples of whole milk powder for infants, students, adults and middle-aged and elderly people. The aroma characteristics of milk powders for different age groups were classified and predicted by linear discriminant analysis (LDA) and linear support vector machine (LSVM). The results showed that a total of 54 volatile flavor components were detected in all samples, among which 37 components were common to these samples including propionaldehyde, acetone, hexanal, and caproic acid. Methyl propionate and 1-octen-3-one were exclusively found in infant milk powder. (E,E)-2,4-Decadienal and γ-unsecalactone were unique to students’ milk powder. Heptanal was detected only in adult milk powder. 2-Butanone and benzaldehyde were only found in middle-aged and elderly milk powder. In total, 23 volatile components contributing to the aroma were identified according to their relative odor activity values and aroma radar map, and 10 of them were the key aroma compounds in milk powders for the four age groups, all of which had milky, vegetable-like, fruity, flowery, grassy, caramel-like and tar-like aromas. In addition, infant milk powder had a characteristic apricot kernel-like aroma. The sensory evaluation results showed that the flavor of students’ milk powder and adult milk powder was better than that of infant milk powder and middle-aged and elderly milk powder, which was significantly different from the aroma radar map results. The classification and prediction accuracy of LDA and LSVM for milk powder for different age groups were 93.3% and 94.2%, respectively.
Determination of Chlorogenic Acid in Honeysuckle by Carbon Dot-Molecularly Imprinted Paper Chip
YUE Wei, KONG Jinghua, LIU Shishi, DUAN Fengqi
2022, 43(16):  253-260.  doi:10.7506/spkx1002-6630-20210723-268
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Based on digital imaging, a microfluidic paper chip for the rapid determination of the chlorogenic acid content in honeysuckle was developed and optimized by using carbon dots, which combines the high accuracy of fluorescence carbon dots and the high selectivity of molecularly imprinted polymers. Using nitrogen and sulfur co-doped carbon dots as a fluorescent sensing material and chlorogenic acid as a template molecule, a carbon dot-molecularly imprinted paper chip was made by synthesizing molecularly imprinted polymers on the hydrophilic surface of filter paper. Based on the redness, greenness, and blueness values of colored spots, the experimental conditions were optimized using single-factor experiments. The optimal preparation conditions were molar ratio of chlorogenic acid to 3-aminopropyltriethoxysilane (functional monomer) to ethyl orthosilicate (cross-linking agent) 1:8:8, addition of 1 mL of anhydrous ethanol and 0.2 mL of amino-modified carbon dot solution to 0.01 mmol of chlorogenic acid, and ultrasound-assisted polymerization for 35 min. The optimal color development conditions were sample volume 4 μL, and reaction time 15 min. Under the optimized conditions, a good linear relationship was obtained between the greenness value and chlorogenic acid concentration in the range of 0.025–0.15 mg/mL, with a determination coefficient of 0.991 8, and the detection limit of the method 0.020 6 mg/mL. The recoveries of chlorogenic acid spiked into honeysuckle were 90.77%–102.10%. The paper chip method has the advantages of low cost, good selectivity and rapidity (It can be completed within 20 min). It can be used as a supplementary method for the determination of chlorogenic acid in the field or under primitive conditions.
Gas Chromatography-Ion Mobility Spectrometry and Electronic Nose to Detect Flavor Release from Cooked Indica Rice during Oral Processing
Sailimuhan·ASIMI, REN Xin, ZHANG Min, LIU Dongxiao, GUAN Lina
2022, 43(16):  261-268.  doi:10.7506/spkx1002-6630-20211013-133
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In order to study flavor release from cooked indica rice during oral processing, boluses of cooked indica rice from volunteers at different mastication stages were collected and analyzed for volatile components by gas chromatography-ion mobility spectrometry (GC-IMS) and electronic nose. The differential marker volatile compounds among different mastication stages were investigated. The results of electronic nose indicated that the flavor of cooked rice significantly differed before and after mastication. A total of 33 flavor compounds were identified by GC-IMS. Compared with that before mastication, the content of aldehydes in 25%, 50%, 75% and 100% boluses decreased by 62.01%, 47.60%, 69.19% and 71.78%, respectively; the alcohol content increased by 59.89%, 42.59%, 29.94% and 17.73%, respectively; the ketone content decreased by 31.92%, 17.87%, 34.92% and 38.45%, respectively. Through partial least squares-discrimination analysis (PLS-DA), 11 compounds were selected as characteristic markers, including hexanal and its dimer, octanal, heptanal, 1-propanol, 1-butanol, 2,3-pentanedione, 2-heptanone, 2-pentylfuran and limonene and its dimer.
Widely Targeted Metabolomics Analysis of the Nutritional Profile of Litchi Pulp
JIANG Nonghui, ZHU Huili, LIU Wei, XIANG Xu, XIAO Zhidan, LAI Xuhui, FAN Chao, JIN Feng, ZHU Qianying
2022, 43(16):  269-278.  doi:10.7506/spkx1002-6630-20210702-017
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A total of 539 metabolites in the flesh of 10 litchi cultivars were identified by widely targeted metabonomics based on an ultra-performance liquid chromatography-quadrupole time of flight-tandem mass spectrometry (UPLC-QTOF-MS/MS) in the multiple reaction monitoring model (MRM), and the comprehensive information about the composition and abundance of metabolites in litchi was described. Totally 298 primary metabolites (55.29%) and 228 secondary metabolites (42.30%) were found. Amino acids and their derivatives (82, 15.21%), lipids (60, 11.13%), organic acids (59, 10.95%), nucleotides and their derivatives (53, 9.83%), sugars and alcohols (25, 4.64%) were identified as the main primary metabolites, and flavonoids (129, 23.93%), phenolic acids (54, 10.02%) and alkaloids (31, 5.75%) were identified as the main secondary metabolites. Principal component analysis (PCA) and cluster heat map analysis were used to compare the metabolites of the 10 litchi cultivars. It was found that these cultivars were clearly separated into three distinct clusters according to the time of maturation and the flavor quality of the cultivars. The most important metabolies with relative content of more than 1% in each class were identified, and the contribution of each class of metabolites to the nutrition of litchi pulp was revealed. In addition, γ-aminobutyric acid, inositol, garnet acid and trigonelline were found to be abundant metabolites with unqiue functional and nutritional properties. In view of the fact that the identification of litchi metabolites can be closely related to people’s nutrition and health, as well as fruit flavor and resistance, the results of this study will provide a theoretical basis and reference information for understanding the nutrition of litchi and its cultivation, breeding, and comprehensive utilization.
Dynamic Changes of Volatile Compounds of Beef during the Dry-aging Process
LIU Meng, ZHANG Shunliang, ZANG Mingwu, ZHAO Bing, HUANG Huijia, ZHU Ning, LI Su, WU Qianrong, LIU Bowen, ZHAO Yan, QIAO Xiaoling, WANG Shouwei
2022, 43(16):  279-284.  doi:10.7506/spkx1002-6630-20211108-093
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The dynamic changes of volatile compounds in beef high rib during the dry-aging process were investigated by using electronic nose (E-nose) and gas chromatography-olfactometry-mass spectrometry (GC-O-MS). Samples with different aging periods could be clearly distinguished by E-nose. As the aging proceeded, the content of volatile compounds increased significantly. At the 28th day, the content of volatile compounds was 3.21 times as high as that of unaged beef. Cluster analysis was used to investigate the similarity of changes in volatile compounds, suggesting that the aging process could be separated into three stages. The first stage was from days 0 to 7; the second stage was from days 7 to 21; the third stage was from days 21 to 28. The analysis of relative odor activity value (ROAV) and aroma characteristics demonstrated that during the whole aging process, the key aroma compounds were isopentanol and ethyl hexanoate, with wine-like, malty and fruity flavors. Meanwhile, the key volatile compounds of beef samples varied from period to period. At the 28th day, decanal and dodecanal were identified as key aroma compounds, resulting in a change in the overall flavor of beef from fruity to fatty.
Effects of Different Storage Containers on Flavor Compounds in Feng-Flavor Baijiu
LIU Lili, YANG Hui, JING Xiong, ZHANG Yafang, YAN Zongke, QI Yaohua, XU Chen
2022, 43(16):  285-293.  doi:10.7506/spkx1002-6630-20210910-119
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In order to explore the effects of storage containers on the volatile components of baijiu, gas chromatography (GC), headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry (HS-SPME-GC-MS), and ultra-high performance liquid chromatography (UPLC) were used to analyze the volatile components of baijiu stored in Jiuhai, a pottery jar and a stainless steel tank as well as fresh baijiu. Five classes of compounds, including esters, alcohols, acids, aldehydes, ketones and phenolics, were identified. The results showed that the fresh sample contained the smallest number (79) but largest amount (7 756 mg/L) of volatile components. Jiuhai stored sample contained a relatively large variety (94) but the least amount (4 276 mg/mL) of volatile components. The samples stored in the pottery jar and the stainless steel tank contained the largest number (96) of volatiles components, and the total amounts of volatile components in them were 5 957 mg/L and 5 360 mg/L, respectively, lower than those in the fresh sample but higher than those in the Juihai stored sample. Furthermore, principal component analysis (PCA) and heat map analysis showed that for the baijiu stored in the pottery jar and the stainless steel vessel, there was a high correlation among isoamyl alcohol, isobutanol, ethyl laurate, hexanoic acid-2-phenyl ethyl ester, furfuryl hexanoate and acetal, which have flowery and fruity aroma characteristics. However, the Jiuhai-stored baijiu showed a strong correlation among ethyl octadecanoate, ethyl linolenic acid, ethyl tetradecanoate, phenyl ethanol, and benzaldehyde, which have flowery, fruity, honey-like and almond-like aroma characteristics. The effects of storage containers on the volatile components in stored baijiu may be related to the gas permeability and the transition metal ion-releasing capacity of the storage containers and the pH change during baijiu storage.
Comprehensive Sensory Quality Evaluation of Dianhong Congou Tea Infusions Using Intelligent Sensory Multi-source Information Fusion Technology
CHEN Jiayu, YUAN Haibo, SHEN Shuai, DENG Yuliang, LIU Zhengquan, XIE Jialing, YANG Yanqin, JIANG Yongwen
2022, 43(16):  294-301.  doi:10.7506/spkx1002-6630-20211028-321
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According to the results of sensory evaluation by tea tasters, 21 Dianhong Congou tea infusion samples were divided into three categories: A, B, and C. Using multi-source information fusion based on electronic nose, electronic tongue and electronic eye, a 112-dimensional dataset was obtained to characterize the comprehensive sensory quality of tea infusions. The results showed that orthogonal partial least squares-discriminant analysis (OPLS-DA) could effectively distinguish the three types of tea infusion (R2Y = 0.937, Q2 = 0.900). Seven variables including S1 (AHS), S5 (NMS), B71 and B32 (nerol), B27 (myrcene), S4 (CTS), and B29 (limonene) were considered important in the classification model with variable importance in projection (VIP) score greater than 1.5. Furthermore, quantitative prediction of the comprehensive quality score of tea infusions was achieved using partial least squares regression (PLSR) and stepwise multivariate linear regression (SMLR). The absolute error and the relative error of the former were less than 1.86 points and 2.06%, while those of the latter were less than 3.57 points and 4.07%, respectively. These results demonstrate that multi-source information fusion combined with multivariate statistical analysis can allow for qualitative and quantitative evaluation of the comprehensive quality of Dianhong Congou tea infusions, which provides effective technical support for the quality control and evaluation of tea infusions.
Safety Detection
Effect of Cooking Process on the Potential Safety Risks of Nitrate in Water Spinach and Cabbage
WU Songheng, LIU Yuhuan, CUI Xian, ZHANG Qi, WANG Yunpu, LUO Xuan
2022, 43(16):  302-308.  doi:10.7506/spkx1002-6630-20211011-103
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In this study, the effects of four cooking methods (stir-frying, steaming, microwaving and boiling) on the nitrate and nitrite contents and antioxidant capacity of water spinach and cabbage were investigated, and the potential safety risk of nitrate was evaluated by the antioxidant/in vivo nitrite ratio (A/N). The results showed that stir-frying increased the content of nitrate (28.03%?49.57%) and ferric reducing power (108.88%?218.35%) of leafy vegetables, while boiling was the opposite. Microwaving and steaming decreased the content of nitrate (31.25%?46.61%) and increased ferric reducing power (76.35%?112.99%). Based on the edibility and A/N ratio, the potential safety risk of nitrate in water spinach and cabbage cooked for less than two minutes could be controlled using boiling and stir-frying, respectively. Microwaving is a relatively safe way to cook both kinds of leafy vegetables, but should not exceed four minutes, while steaming is more suitable for longer cooking (> 4 min).
Simultaneous Determination of 11 Pesticides in Rosa roxburghii by QuEChERS-Ultra-high Performance Liquid Chromatography-Tandem Mass Spectrometry
YAO Xiaolong, HAN Lei, LIU Xudong, LUO Yue, WU Qiong, AN Huaming, WU Xiaomao
2022, 43(16):  309-316.  doi:10.7506/spkx1002-6630-20210629-339
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Objective: A method for the determination of 11 common pesticides in Rosa roxburghii Tratt. was established using QuEChERS (quick, easy, cheap, effective, rugged, and safe) extraction and ultra-high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Methods: The QuEChERS conditions were optimized by performing spiked recovery tests. Acetonitrile was used for extraction, and primary secondary amine (PSA) and graphitized carbon black (GCB) were used for purification. The chromatographic separation was achieved using gradient elution with a mobile phase consisting of 0.1% formic acid water and acetonitrile at a flow rate of 0.4 mL/min. In the positive ion mode using an electrospray ionization source, the fragmentor voltage, collision energy and ion pairs for each pesticide were optimized to obtain the best response, and the pesticides were quantified by matrix-matched calibration. Results: The limits of detection (LODs) for all pesticides were in the range of 1.31–8.56 μg/kg, and the limits of quantitation (LOQs) ranged from 4.13–43.57 μg/kg. The correlation coefficients (R) of the calibration curves were in the range of 0.991 2–0.999 9. The average recoveries at three spiked levels ranged from 84.5% to 103.8% (n = 6) with relative standard deviations (RSDs) of 1.2%–8.5%. Conclusion: This method was rapid, sensitive and precise, and could provide technical support for the determination of pesticide residues in R. roxburghii.
Rapid Detection of Ametryn and Atrazine by a Novel Molecularly Imprinted Polymer-modified Selective Ion Source Coupled to Electrospray Ionization Mass Spectrometry
MA Hongyue, YANG Minli, ZHANG Feng, YANG Bingcheng, ZHANG Feifang
2022, 43(16):  317-323.  doi:10.7506/spkx1002-6630-20220223-182
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A rapid method for the trace level detection of ametryn and atrazine residues in food matrices was developed by using a selective ambient mass spectrometry (AMS) ion source based on molecularly imprinted polymer modified iron sheet (MIPIS) in combination with electrospray ionization mass spectrometry (ESI-MS). Molecularly imprinted polymer (MIP) using cyanazine as template molecule was prepared by polymerization of methacrylic acid (MAA) and aniline in aqueous solution. MIPIS was used as an extraction tip for rapid enrichment of ametryn and atrazine in soy milk powder, wheat and milk before direct analysis by AMS ion source coupled to ESI-MS. The results showed that the linearity of this method ranged from 0.2 to 200 μg/L, with correlation coefficients of 0.998 2 and 0.999 7 for ametryn and atrazine, respectively. The average recoveries of ametryn and atrazine at three spiked levels ranged from 81.05% to 109.66%. The limits of detection (LODs) and the limits of quantification (LOQs) of the analytes were 0.2–0.5 μg/kg and 0.6–1.5 μg/kg, respectively. This study has provided a simple and sensitive method that can effectively avoid the tedious sample pretreatment and time-consuming chromatographic separation for rapid detection of trace levels of triazine pesticide residues in foods.
Maturity Detection of Camellia oleifera by Hyperspectral Imaging
HU Yilei, JIANG Hongzhe, ZHOU Hongping, XU Linyun, JU Hao, WANG Ying
2022, 43(16):  324-331.  doi:10.7506/spkx1002-6630-20210619-229
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In order to solve the problem of the reduction in the yield of camellia oil caused by inaccurate judgment of the picking date of Camellia oleifera, hyperspectral imaging technology combined with chemometrics was used to qualitatively classify the maturity of C. oleifera. The changes in the physicochemical and spectral characteristics of C. oleifera fruit at different maturity stages were examined. Curvature correction of hyperspectral images was carried out. Four classification algorithms were used to establish a discriminant model for C. oleifera fruit maturity based on the full-band spectral data, and it was found that the support vector machine (SVM) model had the highest classification accuracy (97%). Five feature variable selection methods were used to reduce the dimension of the full-band spectral data, and it was found that the accuracy of the model based on the feature wavelengths selected by competitive adaptive reweighted sampling (CARS) was the highest (82%). The accuracy of the SVM model based on a combination of the color and texture features extracted from the hyperspectral images was higher than that of the model based on single spectral features (whose dimension was reduced by CARS), with classification accuracy for the training and test sets of 95% and 93%, respectively. In conclusion, hyperspectral imaging technology can be used to classify C. oleifera with different maturities, which will provide a scientific basis for the judgment of the best picking date of C. oleifera, and is of great significance in ensuring the maximum tea seed yield and the optimum oil quality.
Preparation of Polyclonal Antibody against Ganoderic Acid A and Establishment of Enzyme Linked Immunosorbent Assay
YUAN Yaowu, TIAN Yiling, LI Shengyun, YANG Xinyi, MA Xiaofei
2022, 43(16):  332-337.  doi:10.7506/spkx1002-6630-20210607-081
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The conjugated antigen of ganoderic acid A was synthesized by the active ester method using bovine serum albumin as a carrier and was used as an immunogen to immunize rabbits according to the immunization procedure to obtain the polyclonal antibody against the conjugated antigen. After analyzing the titer and target of the polyclonal antibody, an indirect competitive-enzyme linked immunosorbent assay (ic-ELISA) for ganoderic acid A was established. The results showed that the polyclonal antibody included idiotypic antibodies targeting three regions of the conjugated antigen, with a total titer of 1:78 125, and a titer of 1:3 125 for specific anti-ganoderic acid A antibody. The detection limit of ganoderic acid A was 0.3 μg/L, and the median inhibitory concentration was 4.0 μg/L. The linearity range of this method was 0.6–27.3 μg/L. The inter-batch coefficient of variation was less than 10%, and the recoveries for spiked samples were between 82.9% and 118.6%. The results of determination of 22 commercial samples of Ganoderma lucidum powder showed that there was a significant difference in ganoderic acid A contents among different brands. The correlation coefficient between the results of this method and those obtained by high performance liquid chromatography (HPLC) was 0.972. The results showed that ic-ELISA was feasible for the determination of ganoderic acid A. This method can provide an auxiliary scheme for the quality control of related products in the G. lucidum health product market.
Determination of Typical Alternaria Toxins in Edible Vegetable Oil by Ultra-high Liquid Performance Chromatography-Tandem Mass Spectrometry
LAN Feng, WANG Xinyu, YAO Jie, JIANG Wei, XU Jingjing, SUN Lin, WANG Zhixin
2022, 43(16):  338-343.  doi:10.7506/spkx1002-6630-20210619-228
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An ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was established for the determination of typical Alternaria toxins in edible vegetable oil. Using an orthogonal array design, the optimal extraction conditions were found to be vortex-assisted extraction with 4 mL of methanol-acetonitrile solution (1:1, V/V) for 10 seconds. Chromatographic separation was conducted on a Waters BEH C18 (100 mm × 2.1 mm, 1.7 μm) column with gradient elution using a mobile phase consisting of acetonitrile and 1 mmol/L ammonium carbonate. Detection was performed using an electrospray ionization source operated in the negative ion mode with multi-reaction monitoring (MRM). Good linearity was observed for tenuazonic acid over the concentration range from 0.02 to 0.2 mg/L, and for alternariol, altenuene, tentoxin and alternariol monomethyl ether over the concentration range from 0.002 to 0.2 mg/L, with correlation coefficients not less than 0.998. At spiked levels from 0.002 to 0.2 mg/kg, the average recoveries of the five toxins in sunflower seed oil and soybean oil ranged from 98% to 118% with relative standard deviations (RSDs) ranging from 2.9% to 17.4%. The limits of quantitation (LOQ) for the analytes were 0.002–0.02 mg/kg. The developed method is suitable for the detection of typical Alternaria toxins in edible vegetable oil.
Rapid Detection of Dichlorvos Using Nitrogen, Sulfur and Silicon Doped Carbon Quantum Dots Derived from Stems and Leaves of Broccoli
LIAN Zhifeng, MAN Huasheng, XIU Lili, HUANG Jianying, DONG Lijuan
2022, 43(16):  344-350.  doi:10.7506/spkx1002-6630-20210523-273
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Using waste broccoli stems and leaves as the precursor, nitrogen, sulfur and silicon doped carbon quantum dots (CDs) were prepared by hydrothermal carbonization method, and their structural characterization and element analysis were conducted by dynamic light scattering (DLS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Furthermore, according to the principle of enzyme inhibition, a CDs/Fe2+/acetylcholinesterase reaction system was constructed and used to fabricate a fluorescence sensor to detect organophosphorus pesticides. The results showed that the new CDs had a graphene-like structure, with a quantum yield of 9.53% and good water solubility and photoluminescence properties. The particle size was measured to be about 30 nm, nitrogen, sulfur and silicon were found to be present in the surface of CDs, and the dots contained functional groups dominated by oxygen and nitrogen. The limit of detection (LOD) of the fluorescence sensor for dichlorvos was about 8 ng/mL. Finally, the oxidized/reduced CDs/Fe2+ fluorescent probe was applied to the determination of dichlorvos in commercial foods. The results showed that the recoveries for the spiked samples ranged from 90% to 97% with relative standard deviation (RSD) not larger than 1% (n = 3), indicating the practicality and accuracy of the probe. The CDs/Fe2+ fluorescent probe has a broad prospect for the detection of organophosphorus pesticides in the fields of biology and food in the future.
Detection of Cu2+ Using Methanobactin-coupled Lipase Biosensor with Differential Pulse Voltammetry
WANG Yan, ZHAO Ning, WANG Yue, LI Hongjia, XIN Jiaying, SUN Lirui, GUAN Huanan
2022, 43(16):  351-358.  doi:10.7506/spkx1002-6630-20210621-249
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In this study, a methanobactin (Mb)-coupled lipase biosensor was constructed based on the fact that Mb can specifically capture Cu2+. Lipase immobilized on gold nanoparticles (Lipase@AuNPs) was successfully prepared and its structure and morphology were characterized by fluorescence, ultraviolet-visible (UV-vis) and Fourier transform infrared spectroscopy (FTIR) and scanning transmission electron microscopy (STEM). The biosensor could monitor the response of electrical signals during the hydrolysis of triolein by lipase. Cu2+ specifically combined with Mb and was enriched around lipase, which inhibited the catalytic activity of lipase and significantly reduced the current intensity, thus allowing rapid qualitative and ultra-trace reverse quantitative detection of Cu2+. The results showed that the optimal detection conditions, as determined by differential pulse voltammetry (DPV), were as follows: substrate concentration 2 g/100 mL and buffer pH 7.5. The sensor current difference had a good linear relationship with Cu2+ concentration in the range of 1–100 nmol/L. The regression equation was as follows: y = 0.228x + 0.774 8, with a correlation coefficient (R2) of 0.995 0, and the detection limit of this method was 0.03 nmol/L (RSN = 3). Therefore, the new lipase biosensor has high sensitivity, specificity and stability, which lays a research foundation for the detection of trace and ultra-trace heavy metals in foods.