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25 April 2023, Volume 44 Issue 8
Food Chemistry
Preparation and Properties of Iron-Soy Protein Nanocomplexes Based on Coordination
ZHAN Hongdong, DIAO Congcong, ZHAO Mouming, ZHOU Feibai
2023, 44(8):  1-8.  doi:10.7506/spkx1002-6630-20220806-080
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In the present study, in order to broaden the application of iron fortifiers in the food industry, alkali-heat treated soybean protein isolate (HSPI) was reacted with FeSO4 to fabricate stable iron-containing nanocomplexes. The results showed that the reaction of HSPI with an appropriate concentration of FeSO4, which was pH dependent, could form stably dispersed nanocomplexes (Fe-HSPI). The size of Fe-HSPI changed with increasing reaction pH, and the color became darker. Fe-HSPI was stable against in vitro digestion, and the binding between protein and Fe2+ was maintained during simulated gastrointestinal digestion, which could be beneficial to prevent free iron stimulating the gastrointestinal tract. Herein, Fe-HSPI prepared at pH 7 (Fe-HSPIpH 7) had good homogeneity (polydispersity index, PDI < 0.2) and the content of soluble iron after digestion was more than 80%, showing a remarkable potential for absorption and utilization. The Fe2+ in Fe-HSPIpH 7 mainly combined with the nitrogen atom of the amino group and the oxygen atom of the carboxyl group in HSPI, thereby facilitating the folding of the peptide chain and resulting in the formation of a structure stabilized by disulfide bonds. Compared with FeSO4, Fe-HSPIpH 7 induced a significantly lower degree of lipid oxidation when applied in oil-in-water emulsions, thus exhibiting lower reactivity and having better potential for application as an iron fortifier.
Preparation and Structural Characterization of β-Dextranase Hydrolytic Products of Konjac Glucomannan
QUE Feng, XIA Yuting, GAO Tianqi, WANG Chao, WANG Lan, XIONG Guangquan, SHI Liu, DING Anzi, WU Wenjin
2023, 44(8):  9-15.  doi:10.7506/spkx1002-6630-20220801-004
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Konjac glucomannan (KGM) was degraded by β-glucanase. The structural characteristics of KGM and its hydrolysate were identified by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), and their molecular masses were determined by gel permeation chromatography with multiple angle laser light scattering. The chemical characteristics of the hydrolysate were evaluated by measuring their intrinsic viscosity, deacetylation degree, soluble polysaccharide content and electrical characteristics. The results showed that the major chain structure of the hydrolysate did not change compared with KGM. After 120 min of treatment with a five-fold excess of the enzyme, a weak crystalline region may appear. SEM results showed that the surface of the hydrolysate gradually became lamellated, and its molecular weight decreased to (36.48 ± 1.23) kDa. The characteristic viscosity decreased by 98%, the degree of deacetylation increased significantly (P < 0.05), and the content of total soluble sugar decreased significantly (P < 0.05). This study can provide a reference for the enzymatic modification of KGM to promote the high-value utilization of KGM hydrolysate resources.
Effects of Dietary Fibers on Gelation Properties of Low-Salt Chicken Breast Surimi
WANG Yu, YUAN Jingjing, ZHAO Dianbo, BAI Gaowei, LI Ke, LI Junguang, BAI Yanhong
2023, 44(8):  16-22.  doi:10.7506/spkx1002-6630-20220811-128
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The differences in physicochemical properties of oat, pea and apple dietary fibers and the effects of their addition on gel properties of low-salt (1% NaCl, m/m) chicken breast surimi were studied. The results showed that the water-holding capacity and swelling power of the three dietary fibers in descending order were pea dietary fiber > apple dietary fiber > oat dietary fiber. The addition of each of these dietary fibers could significantly improve the cooking yield, hardness and chewiness of low-salt chicken breast surimi (P < 0.05), and the effect of pea and apple dietary fibers was more pronounced than that of oat dietary fiber. All the dietary fibers could increase the storage modulus (Gʹ), shorten the transverse relaxation time of free water (T22), increase the relative contents of weakly bound water (P2b) and immobilized water (P21) in the gel, and promote the formation of a compact and dense three-dimensional network structure. Pea dietary fiber significantly increased the relative content of β-sheet structure (P < 0.05), whereas apple and oat dietary fibers significantly increased the relative content of β-turn (P < 0.05). In conclusion, oat, pea and apple dietary fibers can significantly improve the water-holding capacity and texture properties of low-salt chicken breast surimi gel by changing the rheological properties, water mobility and distribution, microstructure and protein secondary structure.
Enhanced Antioxidant Activity and Sustained-Release Property of Curcumin Encapsulated in Glycated Soy β-Conglycinin Nanoparticles
WANG Zijun, LIU Huihui, MA Zhigang, SHAO Dongliang, JIANG Shaotong, ZHENG Zhi
2023, 44(8):  23-29.  doi:10.7506/spkx1002-6630-20220815-176
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Soy β-conglycinin (7S)-dextran conjugates prepared under dry-heating conditions were used to encapsulate curcumin, and the antioxidant activity and sustained-release property of encapsulated curcumin were investigated. Results showed that the grafting degree and browning index of 7S-dextran conjugates increased with increasing reaction time (0, 24, 48 and 72 h), reaching the highest values of 15.02% and 0.24 at 72 h, respectively. 7S-curcumin and 7S-dextran-curcumin nanocomplexes were fabricated by pH-shifting method. The highest curcumin loading of 129.61 μg/mg was observed in 7S-dextran conjugate obtained at 72 h of reaction time (7S-dextran-72 h), which was significantly higher than that in 7S (69.06 μg/mg). Fluorescence spectroscopy indicated that curcumin combined with 7S or 7S-dextran-72 h mainly through hydrophobic interactions. It was observed by transmission electron microscopy (TEM) that 7S-curcumin and 7S-dextran-72 h-curcumin nanocomplexes were spherical. The antioxidant activity of 7S-dextran-72 h-curcumin, which had stable sustained-release property, was approximately 2.36 times higher than that of free curcumin at 100 μg/mL. The bioavailability of curcumin encapsulated in 7S-dextran-72 h was 66.83%, while the bioavailability of curcumin encapsulated in 7S and free curcumin were 48.93% and 33.06%, respectively. 7S-dextran-72 h could be used as an outstanding nanocarrier for curcumin to enhance its antioxidant activity and sustained-release property.
Effect of Banana Flower Extract on Physicochemical Quality and Volatile Flavor Substances of Naturally Fermented Yak Meat Sausage
ZHAO Jiaying, TANG Shanhu, LI Sining, LI Qiaoyan, CHEN Lamei
2023, 44(8):  30-39.  doi:10.7506/spkx1002-6630-20220427-345
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The effects of the addition of different amounts (0.01%, 0.05% and 0.10%) of banana flower extract (BFE) on the physicochemical quality of fermented yak meat sausage were investigated using butylated hydroxy toluene (BHT) as a positive control, and the changes in the pH, moisture content, color, water retention, texture, rheological properties, total bacterial count, volatile flavor substances and sensory quality of the sausage during fermentation and storage were evaluated. The results showed that the sausage with 0.10% BFE had stronger water retention and bacterial inhibition ability, while increasing BFE addition reduced the textural characteristics and storage modulus of the fermented sausage. A total of seven classes of volatile flavor substances, including alcohols, aldehydes, acids and esters, were detected in all samples during fermentation, and three principal components were obtained by principal component analysis, with a cumulative contribution of 75.014%. In conclusion, BFE has strong antioxidant activity and significantly improves the physicochemical properties of fermented yak meat sausage, and the most pronounced effect is obtained with 0.01% BFE addition.
Isolation, Purification and Structural Characterization of Polysaccharides from Chickpea
ZHAO Jiaying, XIN Yue, SONG Xiaoxiao, NIE Shaoping, YIN Junyi
2023, 44(8):  40-45.  doi:10.7506/spkx1002-6630-20220816-190
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In this research, the distribution and physicochemical properties of polysaccharides from the whole seed, cotyledon and hull of Cicer arietinum were analyzed and compared, and the structure characteristics of Cicer arietinum hull polysaccharide (CAHP) were characterized. It was found that polysaccharide was concentrated in the hull of chickpea according to the yield and composition of polysaccharide. CAHP was further purified by column chromatography into six fractions (Fw, F0.1, F0.2, F0.3, F0.5 and F2), and the structure of CAHP-F0.2, which showed relatively high yield and good homogeneity, was characterized. The results showed that CAHP-F0.2 was consisted of mostly homogalacturonan (HG)-type pectic polysaccharide whose main chain was linked by 1,4-GalpA, and contained a small amount of RG-I domain, with arabincan and arabinogalactan-II side chain. This study will provide a theoretical basis for future research on the structure, biological activity and resource development of chickpea polysaccharides.
Effect of Malondialdehyde Oxidation on the Structure and Functional Properties of Myofibrillar Protein in Yak Meat
CHEN Lamei, TANG Shanhu, LI Sining, LI Jinjin, LI Qiaoyan, ZHAO Jiaying
2023, 44(8):  46-54.  doi:10.7506/spkx1002-6630-20220627-299
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To explore the effect of different levels of lipid oxidation on the structural and functional properties of myofibrillar protein (MP) in yak meat, the oxidation of side-chain amino acids, structure, rheological characteristics, and emulsion stability of MP incubated in the presence of different concentrations (0, 0.1, 1, 5, 10 and 20 mmol/L) of malondialdehyde (MDA) were measured. The results showed that with an increase in MDA concentration, the contents of carbonyl group, MDA-MP adducts and dimeric tyrosine and the relative content of β-turn in MP overall increased, while total sulfhydryl content, surface hydrophobicity, endogenous fluorescence intensity, and the relative contents of α-helix and β-sheet decreased. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) results indicated gradual loss of myosin heavy and light chains, implying that interaction with MDA could induce MP oxidation and cross-linked aggregation and result in structural transition from an ordered to a disordered state. In addition, moderate oxidation (with MAD concentration < 10 mmol/L) increased the storage and loss moduli and improved the gel quality of MP; however, excessive oxidation (with MAD concentration ≥ 10 mmol/L) led to serious aggregation of MP and a decrease in the storage and loss moduli as well as a decrease in the emulsion stability and color deterioration. In conclusion, MDA oxidation can promote the oxidation of MP, and alter the structural and functional properties.
Understanding Surimi Protein-Lipid Interaction Based on Protein Structure and Physicochemical Properties
ZHOU Jiaying, HU Zhiheng, HUANG Jiayin, LI Gaoshang, HU Lingping, CHEN Jianchu, HU Yaqin
2023, 44(8):  55-61.  doi:10.7506/spkx1002-6630-20220714-157
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The effects of different concentrations (0%–20%) of soybean oil or lard added to pomfret surimi gel on its physicochemical properties and protein structure were studied. The addition of 8% lard or soybean oil significantly increased the whiteness, water-holding capacity (WHC), gel strength, storage modulus (G’) and sensory evaluation of surimi. When the addition level was higher than 8%, the strength, WHC, and G’ decreased. Surimi gel with 8% lard was better than that with the same concentration of soybean oil. The results of scanning electron microscopy (SEM) showed that lipids not only filled the void between protein molecules, but also formed an interfacial protein film on the surface, which combined with the protein matrix through protein filaments. It was shown that there was an interaction between lipids, the interfacial protein membrane and proteins in surimi gels. Raman spectra showed that the addition of lipids decreased the relative content of α-helix, and the first increases and then decreases of β-sheet. The addition of soybean oil also significantly increased the relative content of random coils, while the change in random coils of lard was not as significant as that of the soybean oil treatment group. Both soybean oil and lard led to the exposure of hydrophobic groups on the side chain of proteins in surimi gels. These results suggest that the addition of oil changes protein structure and microenvironment in surimi, which in turn affects the physicochemical properties of surimi gels. The surimi gel with 8% lard has better properties.
Effect of Five Functional Sweeteners on the Quality of Lotus Paste Filling
WU Jinyuan, LIANG Zijian, LI Shenghua, FU Shuyong, YANG Wen’an, GAO Xiangyang
2023, 44(8):  62-70.  doi:10.7506/spkx1002-6630-20220811-135
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Erythritol, sorbitol, maltitol, fructooligosaccharide or isomaltulose instead of sucrose was used in lotus paste filling. The effects of different sweeteners on the eating quality of lotus paste filling were investigated by gas chromatography-ion mobility spectrometry (GC-IMS), an electronic tongue, a texture analyzer and sensory evaluation. The results showed that sugar alcohol sweeteners significantly increased the brightness of lotus paste filling, and fructooligosaccharide and isomaltulose deepened the color of lotus paste filling. In addition, the water content of lotus paste filling was negatively correlated with the hardness (r = −0.882, P < 0.01), but positively correlated with the adhesiveness (r = 0.620, P < 0.01) and cohesiveness (r = 0.622, P < 0.01). All functional sweeteners except erythritol increased the water content and improved the texture quality of lotus paste filling. The results of electronic tongue test showed that the functional sweeteners reduced the sweetness of lotus paste filling and helped to mask undesirable tastes such as bitterness. A total of 32 volatile substances were detected in lotus paste filling by GC-IMS, including aldehydes (53.94%–70.60%), ketones (10.36%–18.63%), alcohols (5.25%–14.25%), acids (1.62%–2.81%), esters (0.22%–0.57%), furans (0.29%–0.72%) and alkanes (0.47%–0.71%). Oligofructose and isomaltose increased the types and contents of aldehydes and ketones and enriched the flavor of lotus paste filling. The flavor of lotus paste filling with sugar alcohols was bland. Isomaltulose and fructooligosaccharide improved the quality of lotus paste filling, and therefore could be used as a substitute for sucrose in the production of low-sugar lotus paste filling.
Cryoprotective Effect of Enzymatic Hydrolysate of Flaxseed Meal Proteins on Dough
ZHANG Yanyan, GUO Penglei, LU Ye, HUANG Yuanyuan, LIU Xingli, ZHANG Hua
2023, 44(8):  71-77.  doi:10.7506/spkx1002-6630-20220617-180
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Differential scanning calorimetry (DSC), low-field nuclear magnetic resonance (NMR) and in situ Raman spectroscopy were used to explore the cryoprotective effect of enzymatic hydrolysates of flaxseed meal proteins obtained at different hydrolysis times on dough. The results showed that the thermal hysteresis activity of the 60 min hydrolysate, with a 13.62% degree of hydrolysis (DH), was highest (0.83 ℃), and the ice recrystallization inhibitory activity was also highest, minimizing the proportion of large ice crystals. It was found that addition of the hydrolysate had the most significant cryoprotective effect on dough. Compared with the control group, the proportion of strongly bound water in dough increased by 13.2%, and the proportions of weakly bound water and free water decreased by 0.7% and 7.9%, respectively. The maximum fermentation height, the final height and the onset time of CO2 leakage increased by 18.5%, 24.4% and 34.4%, respectively. Protein structure analysis showed that the relative α-helix content of gluten proteins in dough with the hydrolysate was highest and increased by 35.3% compared with the control group, and the relative random coil content decreased by 28.9%. The intensity (I760) of tryptophan band at 760 cm-1 increased by 282.3%, and the ratio (I850/I830) between the intensities of tyrosine bands at 850 and 830 cm-1 decreased by 59.6%. The relative contents of disulfide bond configurations g-g-g and g-g-t were increased by 8.8% and 9.8%, respectively. In conclusion, enzymatic hydrolysates of flaxseed meal proteins improved the water-holding capacity of dough, shortened dough proofing time, and weakened the damage of ice crystals to the network structure of dough, and the effect of the hydrolysate with DH of 13.62% was most pronounced.
Extraction, Isolation and in Vitro Immunological Activity of Polysaccharides from Wine Made from Glutinous Rice and Chinese Chestnut
HU Meiyi, LIANG Jianlan, LI Runfeng, YANG Xiaokuan
2023, 44(8):  78-85.  doi:10.7506/spkx1002-6630-20220616-162
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Polysaccharides (CWP) from nutritious wine made from glutinous rice with added Chinese chestnut as a nutritional fortifier using the traditional fermentation process of Chinese rice wine (Huangjiu) were obtained by fractional ethanol precipitation and purified by ultrafiltration into two fractions: CWP-1 (> 100 ku) and CWP-2 (30–100 ku). CWP-1 and CWP-2 were mainly composed of eight monosaccharides, including galactose, mannose, glucose, arabinose, xylose, fucose, galacturonic acid and glucuronic acid. Infrared spectroscopy analysis showed the typical absorption peaks of both polysaccharides and the presence of α- and β-glycosidic bond conformations in CWP-1. In vitro immunological assays showed that CWP-1 and CWP-2 significantly induced the secretion of tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6) and nitric oxide (NO) by mouse macrophages RAW 264.7, and their capacity to secrete cytokines was higher than that of lipopolysaccharide (LPS) at the same mass concentration. This study will provide theoretical references for the research and utilization of functional components in chestnut processed Chinese chestnut products and new Huangjiu.
Effect of Guar Gum on Structure and Physicochemical Properties of Fermented Wheat Starch
DING Xinxin, FAN Xin, CAI Qiling, LI Xiaoping
2023, 44(8):  86-92.  doi:10.7506/spkx1002-6630-20220712-132
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The structure and physicochemical properties of fermented wheat starch-guar gum (FS-GG) mixtures of wheat starch naturally fermented for 72 h and different proportions of GG (0%, 0.1%, 0.3% and 0.5%, m/m) were studied. The results showed that the addition of GG significantly reduced the amount of leached amylose and the swelling power of FS, and distinctly lowered its peak viscosity and setback value. GG resulted in aggregation of FS granules to form a gel with a tight network structure, and led to an overall increase in the storage modulus (G’) and loss tangent (tanδ). Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) results indicated that the addition of GG reduced the degree of order, gelatinization enthalpy and relative crystallinity of FS. The gel firmness of FS-GG mixtures increased slowly during storage. The results of this study indicated that GG delayed the retrogradation of FS by changing its crystal structure and gel structure, and the effect was most pronounced at an addition level of 0.5% GG.
Effect of Deproteinization or Defatting on Gelatinization and in Vitro Digestion Properties of Coix Starch
ZHANG Liran, GAO Dan, MAN Jianmin
2023, 44(8):  93-100.  doi:10.7506/spkx1002-6630-20220715-175
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The effect of the removal of starch granule-associated proteins (SGAPs) and/or lipids on pasting and in vitro digestion properties of adlay starch was investigated. The results showed that the removal of both SGAPs and lipids increased the swelling power, solubility, and rapidly digestible starch (RDS) and slowly digestible starch (SDS) contents and decreased the ratio of peak intensities at 1 045/1 022 cm-1, peak viscosity, trough viscosity, breakdown viscosity and resistant starch (RS) content. The removal of SGAPs significantly increased the gelatinization transition temperature and the gelatinization enthalpy and significantly decreased the onset gelatinization temperature. The effect of the removal of SGAPs on the short-range ordered structure and digestibility of adlay starch was more pronounced than that of the removal of lipids. The thermal properties of adlay starch were not significantly affected by the removal of lipids, and the crystal type was not significantly affected by the removal of SGAPs and lipids. The results have potential value for understanding the starch characteristics of adlay and for the application of adlay starch in food processing.
Preparation of Dry Fermented Pork Sausage Using Radish Powder as a Source of Nitrite
YAN Rui, TANG Min, CHEN Dongfang, HUANG Shirong, MEI Xin
2023, 44(8):  101-108.  doi:10.7506/spkx1002-6630-20220713-138
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The feasibility of using white radish powder as a nitrite substitute in dry fermented pork sausages was evaluated. Four groups of sausage were prepared by using a multi-strain starter culture (VBM-60, Sacco): negative control (NC, without nitrate or nitrite), positive control (PC, with 150 mg/kg sodium nitrite), 0.5% white radish powder (R0.5), and 1% white radish powder (R1). The effects of nitrite substitution by white radish powder on the physicochemical, microbiological and sensory characteristics of dry fermented sausage during production and storage were investigated. The results showed that compared with the positive control group, the R0.5 group had higher thiobarbituric acid reactive substance (TBARS) values, better visual appearance, and lower pH, redness value, hardness and chewiness. However, no significant difference was observed in moisture content, total volatile basic nitrogen (TVB-N) value, brightness value, elasticity, cohesiveness, total bacterial count, tissue morphology, color or flavor. During storage, the R0.5 group had higher content of nitrite and lower count of lactic acid bacteria. The nitrite content in the R0.5 group was 13.03 and 16.48 mg/kg at the end of the production and storage process, respectively, which are below the national standard limit. The results indicated that 0.5% white radish powder can be used as a natural source of nitrite for the production of dry fermented sausage.
Effect of Mg2+ on the Structure and Gel Properties of Mutton Myofibrillar Protein
LI Silei, WANG Shouwei, ZHAO Bing, ZANG Mingwu, LI Sining, TANG Shanhu
2023, 44(8):  109-117.  doi:10.7506/spkx1002-6630-20211220-230
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In this study, the effect of Mg2+ on the physiochemical, structural and gel properties of mutton myofibrillar protein was studied. The results indicated that with an increase in Mg2+ concentration (0, 0.01, 0.02, 0.03, 0.04 and 0.05 mol/L), the physicochemical properties of mutton myofibrillar protein (MP) including solubility, emulsification activity, emulsion stability and particle size increased significantly (P < 0.05), the absolute value of the zeta potential decreased, the proportion of β-sheet increased significantly (P < 0.05), and surface hydrophobicity increased significantly (P < 0.05). The endogenous fluorescence intensity of tryptophan was largest at a Mg2+ concentration of 0.04 mol/L. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that the band intensity of myosin and relevant light chain proteins increased. Rheological analysis showed that the storage modulus (G’) first increased and then decreased. Compared with the control group, MP gel strength increased by 70.49% at a 0.03 mol/L Mg2+ concentration. Gel cooking loss and water-holding capacity (WHC) were negatively correlated with Mg2+ concentration (P < 0.05). Low-field nuclear magnetic resonance (NMR) analysis showed that with increasing Mg2+ concentration, immobilized water in the MP gel was transformed into free water. Microstructure observed by scanning electron microscopy (SEM) showed that the higher the concentration of Mg2+, the more porous the gel. Correlation analysis showed that Mg2+ concentration was highly correlated with the structure and gel characteristics of MP. Therefore, Mg2+ can significantly improve the gel properties of mutton MP.
Effect of Sodium Carboxymethyl Cellulose on the Quality of Extruded Pea Protein Products
XIAO Zhigang, WANG Haiguan, JIANG Ruisheng, YU Xiaoshuai, WANG Zhenguo, ZHANG Junjie, WANG Zhe, GAO Yuzhe
2023, 44(8):  118-123.  doi:10.7506/spkx1002-6630-20220423-301
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In order to improve the quality of pea protein-based meat analog, this study investigated the effect of interaction between sodium carboxymethyl cellulose (CMC) and protein on the quality of extruded pea protein products. CMC and pea protein were employed as raw materials to prepare protein-based meat analog by high-moisture extrusion (HME). Next, the effects of CMC contents (0%, 2%, 4%, 6% and 8%) on the textural properties, color, microstructure and protein-protein interaction forces of meat analog were explored. The correlation of secondary structure content and protein-protein interaction forces with quality attributes (textural properties and color) was established. The results showed that the main interaction force was disulfide bonds. Compared with meat analog without CMC, the addition of 4% CMC promoted the formation of disulfide bonds and increased the hardness of meat analog by 95%. Meanwhile, pea protein-based meat analog exhibited a smooth and homogeneous surface. It was also found that the random coil content increased, and was correlated with higher lightness, indicating that CMC could improve the quality of pea protein-based meat analog.
Bioengineering
Effect of the Mitochondrial Membrane Permeability Transition Pore Promoter Atractyloside on Mitochondrial Damage and Tenderness of Postmortem Beef
LIU Chunmei, WEI Qichao, HAN Dong, LI Xia, ZHANG Chunhui, HUANG Feng
2023, 44(8):  124-130.  doi:10.7506/spkx1002-6630-20220401-002
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The objective of this study was to investigate the effect of atractyloside, a promoter of the mitochondrial membrane permeability transition pore (MPTP), on mitochondrial membrane permeability, cristae structure, cytochrome c release and tenderness of postmortem beef and to explore the effect of injury on meat tenderness by releasing cytochrome c and activating caspases. The postmortem longissimus dorsi muscle of adult crossbred cattle was treated or not treated (control) with atractyloside, stored at 4 ℃ and evaluated for mitochondrial ultrastructure, membrane potential, the amount of cytochrome c released to the cytoplasm, cell apoptotic rate, caspase-3 and myofibrillary fragmentation index (MFI) after 0, 12, 24, 72, and 120 h. With postmortem aging time, the number of mitochondrial cristae decreased significantly, and swelling and rupture were observed. The mitochondrial membrane potential decreased significantly, and cytochrome c was released gradually. Starting from 72 h postmortem, the activity of caspase-3 and the apoptosis rate of myocytes increased, and so did MFI. Compared with the control group, atractyloside treatment induced mitochondrial damage by destroying mitochondrial cristae structure, reducing the membrane potential and causing cytochrome c release. In addition, the apoptosis of muscle cells and the fragmentation of myofibrils were accelerated by atractyloside. The opening of the MPTP significantly affected mitochondrial injury in beef after slaughter. Apart from increasing cell membrane permeability, atractyloside also significantly altered the structure of mitochondrial cristae. The internal and external mitochondrial membranes could synergistically regulate the release of cytochrome c, which in turn could affect postmortem tenderization of beef.
Inhibition Mechanism of Apigenin-8-C-glucoside on Starch Digestive Enzymes
CAO Shuyun, ZHENG Yuxue, CHAI Ziqi, YE Xingqian, TIAN Jinhu
2023, 44(8):  131-136.  doi:10.7506/spkx1002-6630-20220608-085
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The regulatory effect and mechanism of apigenin-8-C-glucoside on α-amylase and α-glucosidase activity were systematically investigated using enzyme activity kinetics, fluorescence spectroscopy, circular dichroism (CD) spectroscopy and molecular docking. Results indicated that apigenin-8-C-glucoside showed a good inhibitory effect on α-glucosidase in a non-competitive manner with a half-maximal inhibitory concentration (IC50) of 293.5 mg/L. However, no significant inhibitory effect on α-amylase was observed. Fluorescence spectroscopy showed that apigenin-8-C-glucoside could act as a quencher molecule to bind to α-glucosidase and quench its fluorescence statically, thereby changing the hydrophobic environment of the enzyme. The CD spectrum showed that the interaction between apigenin-8-C-glucoside and α-glucosidase loosened the secondary structure of this enzyme and decreased the contents of α-helix and β-turn. The results from molecular docking corroborated that the main interaction force between apigenin-8-C-glucoside and α-glucosidase was hydrogen bonding with a minimum binding energy of −7.2 kcal/mol. The present study provides a theoretical basis for the future development of apigenin-8-C-glucoside as an ingredient of health foods or drugs.
Label-free Quantitative Differential Proteomic Analysis of Large Yellow Croaker Cultured under Different Aquaculture Modes
WENG Liping, ZHANG Le, LIU Junbo, XIAO Wenfei, WANG Qian, ZOU Ligen
2023, 44(8):  137-142.  doi:10.7506/spkx1002-6630-20220430-395
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Protein differences in large yellow croakers from different aquaculture patterns were investigated by label-free quantitative proteomics. Total muscle protein was extracted from large yellow croakers from common cage aquaculture and deep-water cage aquaculture, and identified and analyzed by high performance liquid chromatography-mass spectrometry (HPLC-MS). The raw data were processed using MaxQuant software to transform the signal peaks into matrix data for peptide/protein expression, followed by graphical visualization using the Perseus software. Differentially expressed proteins between the two aquaculture systems were selected by Student’s t test for gene functional classification, metabolic pathway enrichment and protein network interaction analysis, in which P < 0.05 was considered as statistically significant difference. The results showed that 6 077 peptides, corresponding to 1 232 proteins, were obtained through database alignment. of these proteins, 130 were significantly different between the two groups of large yellow croaker, with 76 being up-regulated proteins and 54 being down-regulated. The most up-regulated protein was TCP chaperone, and the most down-regulated protein was α-1(I) chain collagen. Bioinformatics analysis demonstrated that the major differential proteins were heat shock protein, chaperones, globulin and collagen, and the environmental temperature may be the major factor causing significantly differential expression of large yellow croaker proteins.
Effects of Different Spices on Microbial Community and Physicochemical Properties in Low-Salt Shrimp Paste
BAN Yuhan, YANG Bingbing, MA Aijin, LI Weidong, SANG Yaxin, SUN Jilu
2023, 44(8):  143-151.  doi:10.7506/spkx1002-6630-20220815-177
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In order to develop new shrimp paste products and expand the shrimp paste market, ginger, cinnamon or perilla was added before fermentation of low-salt shrimp paste in this study. The physicochemical indexes of low-salt shrimp paste were determined, and the effect of spice addition on the microbial community composition and diversity of shrimp paste was explored by high-throughput sequencing technology. The results showed that the contents of moisture and salt in shrimp paste were 51.34%–61.77% and 15.61%–17.71%, respectively. The addition of spices decreased the pH and amino nitrogen content of shrimp paste. The addition of cinnamon and ginger reduced the total volatile basic nitrogen (TVB-N) content by 30.41% and 10.28%, respectively, while the addition of perilla increased the TVB-N content by 9.98%. Compared with the control shrimp paste, the diversity of fungi and bacteria in shrimp paste added with perilla was higher. The addition of cinnamon and ginger decreased the richness of bacterial community and increased the richness of fungal community in shrimp paste. The analysis of differential flora showed that the addition of ginger and cinnamon increased the relative abundance of Tetragenococcus and Wallemia, but reduced the relative abundance of Staphylococcus by 99.32% and 98.14%, respectively. The relative abundance of Penicillium and Aspergillus in shrimp paste added with perilla was higher. Pearson correlation analysis showed that Staphylococcus, Wallemia, Rhodotorula and Penicillium had significant correlations with physicochemical indicators, indicating that these microorganisms play an important role in shrimp paste. To sum up, the addition of spices can change the microbial community composition of shrimp paste, enrich the types of shrimp paste and improve the safety of shrimp paste.
Activities of β-Glucosidase and α-L-Arabinofuranosidase from Cordyceps militaris and Their Applications in the Transformation of Ginsenoside Rg1 and Rc
LI Fei, HUANG Qiuting, SUI Xin, XIE Ying
2023, 44(8):  152-161.  doi:10.7506/spkx1002-6630-20220427-349
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In this study, a strain of Cordyceps militaris with high productivity of β-glucosidase was identified and selected. The effects of carbon source, nitrogen source and pH value on the production of β-glucosidase, α-L-arabinofuranosidase, cordyceps acid and biomass by the strain were studied to determine the optimal culture conditions for the production of bioactive substances with high productivity. The transformation pathways and efficiency of ginsenosides Rg1 and Rc by C. militaris were evaluated. The activities of β-glucosidase and α-L-arabinofuranidase were determined by ultraviolet (UV) spectrophotometry. The ginsenoside composition of the transformed products was identified by ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS), and the content of cordycepin and the transformation efficiency of ginsenoside were determined by high performance liquid chromatography (HPLC). The results showed that the highest β-glucosidase activity of ((74.70 ± 0.09) U/mL) was obtained after 120 h culture using cellulose disaccharide as the carbon source and beef extract as the nitrogen source at pH 8, while the highest α-L-arabinofuranosidase activity of ((11.55 ± 0.01) U/mL) was obtained after 72 h culture using lactose as the carbon source and peptone as the nitrogen source at pH 4. The transformation pathways of ginsenoside Rg1 by C. militaris were Rg1→Rh1 and Rg1→F1, and the transformation pathways of Rc were Rc→Rd→Rg3→CK and Rc→CMc. The conversion efficiency of ginsenoside Rg1 and Rc was 54.9% and 83.44% after 168 h, respectively. This study provides a theoretical basis to improve the efficiency of biotransformation of ginsenoside by the medicinal and edible fungus C. militaris, and lays theoretical support for developing food and medicinal products from C. militaris and ginseng.
Enzymatic Characterization and Structural Analysis of Arylesterase from Lacticaseibacillus rhamnosus GG
LI Xinfeng, GUO Tongtong, LI Binchun
2023, 44(8):  162-169.  doi:10.7506/spkx1002-6630-20220426-332
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To obtain novel esterases from probiotic bacteria, the genome of the probiotic Lacticaseibacillus rhamnosus GG (LGG) was analyzed, and the arylesterase gene (LggAE) from LGG was cloned and heterologously expressed. The expressed enzyme was subjected to affinity purification for enzymatic characterization and structural analysis. The results revealed that the optimal pH of the arylesterase was 7.5, which maintained more than 70% of its activity at pH 7.0–10.0. The optimal temperature of LggAE was 50 ℃. LggAE preferentially hydrolyzed medium-chain p-nitrophenol esters, and the most suitable substrate for it was p-nitrophenol octanoate. LggAE was stable at 40 ℃. The enzymatic activity of LggAE was improved by 17.3% in the presence of ethylene glycol. LggAE was tolerant to DMSO. LggAE retained 39.1%–71.0% of its activity in the presence of sodium citrate or NaCl at high concentrations. The enzymatic activity of LggAE was significantly inhibited by sodium deoxycholate at high temperatures. Structural analysis showed that the substrate binding pocket of LggAE was a small hole mainly composed of aliphatic hydrophobic residues.
Component Analysis
Determination of Characteristic Taste Compounds of Crayfish by 1H Nuclear Magnetic Resonance
YAO Jingyu, LIU Jie, BAI Xueying, MO Xueying, CHEN Dewei
2023, 44(8):  170-175.  doi:10.7506/spkx1002-6630-20220615-152
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In order to investigate the nonvolatile taste-active components in crayfish, free amino acids, nucleotides, organic acids, soluble sugars and alkaloids in cooked crayfish muscle were qualitatively and quantitatively analyzed by 1H nuclear magnetic resonance (1H NMR). Their taste activity values (TAVs) and equivalent umami concentration (EUC) were calculated to evaluate the key taste-active compounds and umami attributes, respectively. The results suggested that a total of 33 taste-active compounds were detected, among which arginine, histidine, glutamic acid, alanine, lysine, glycine, adenosine 5’-monophosphate (AMP), inosine 5’-mononucleotide (IMP), succinic acid and lactic acid were the key taste-active compounds with TAVs greater than 1.0, and they played an important role in the taste of crayfish. The EUC of crayfish was 9.1 g monosodium glutamate (MSG)/100 g, indicating very intense umami taste.
Aroma Threshold and Binary Synergy of Furanone, 5-Methylfurfural and 3-Methylthiopropanol in Msalais Wine
QIAO Tongtong, ZHU Lixia
2023, 44(8):  176-183.  doi:10.7506/spkx1002-6630-20220621-224
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In this study, the three-alternative forced-choice (3-AFC) method was used to determine the odor thresholds of three important aroma compounds in Msalais wine including 5-methylfurfural (5-MF), 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF) and 3-methylthiopropanol (3-MTP), and the S-curve and the σ-τ plot were used to analyze the binary interaction of these compounds. The threshold values of 5-MF, DMHF and 3-MTP in simulated wine with an alcohol content of 12% were 190.000, 45.000 and 382.000 μg/L, respectively, and those in dearomatized Msalais wine with 12% alcohol content (sugar contents of 7.4–7.9 °Brix) were 97.580, 798.950 and 196.533 μg/L, respectively. In addition, it was found that sugar contents of dearomatized Msalais wine (with 12% alcohol content) in the range of 7.4–7.9 °Brix and 6.4–7.9 °Brix had little effect on the thresholds of the three aroma compounds. There was no significant difference in the thresholds of these aroma compounds in dearomatized Msalais wine (with sugar contents of 7.4–7.9 °Brix) with 8%, 10%, 12% and 14% alcohol contents. The binary mixtures of these compounds in simulated wine with 12% alcohol content and in dearomatized Msalais with sugar contents of 7.4–7.9 °Brix and 12% alcohol content showed additive effects in the S-curve and the σ-τ plot.
Widely Targeted Metabolomic Analysis of Different Organs of Single- and Double-Petal Jasmine
HONG Yaping, GU Mengya, GAO Ting, YANG Wenwen, LIN Hongzheng, JIN Shan, WANG Pengjie, YE Naixing
2023, 44(8):  184-193.  doi:10.7506/spkx1002-6630-20220515-199
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In this study, the metabolites in the flowers and leaves of single- and double-petal jasmine were determined and compared by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) combined with multivariate statistical analysis. The results showed that a total of 935 metabolites were identified from all samples, including amino acids and derivatives, phenolic acids, nucleotides and derivatives, flavonoids, lignans and coumarins, tannins, alkaloids, terpenoids, organic acids, lipids, saccharides and sugar alcohols, vitamins, and other compounds. Totally 348 and 337 significantly changed metabolites (SCMs) from the flowers and leaves were identified between single- and double-petal jasmine, respectively. The major SCMs were phenolic acids, flavonoids, lipids, saccharides and sugar alcohols. The leaves of double-petal jasmine were rich in flavonoids. In addition, the flavone and flavonol biosynthesis pathways were more active, leading to accumulation of more compounds with biological and pharmacological activities such as nicotiflorin, cynaroside, quercetin, quercetin-3-O-glucoside, astragalin, and afzelin. Lipids were the major unique metabolites in the flowers and leaves of single-petal jasmine. The unique metabolites in the flowers and leaves of double-petal jasmine were more diverse and abundant than those in single-petal jasmine. The results of this study are very meaningful for guiding the development of jasmine resources.
Effect of Different Processing Technologies on the Key Aroma-Active Compounds of Green Tea
YOU Qiushuang, SHI Yali, ZHU Yin, YANG Gaozhong, YAN Han, LIN Zhi, LÜ Haipeng
2023, 44(8):  194-200.  doi:10.7506/spkx1002-6630-20220718-204
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Green tea was made from one bud with two leaves from the tea cultivar Longjing 43 by stir frying, roasting, steaming or sun drying. Stir bar sorptive extraction (SBSE) combined with gas chromatography-olfactometry-mass spectrometry (GC-O-MS) was applied to analyze the influence of different manufacturing processes on the key aroma-active compounds of green tea. The results showed that 31, 27, 25 and 30 key aroma-active compounds were respectively identified from stir-fried green tea, roasted green tea, steamed green tea and sun-dried green tea, which all had floral, fruity and green flavors. Totally, 13 key aroma-active compounds were common to these 4 types of green tea, including β-ionone, naphthalene, linalool, linalool oxide I, geraniol, 1-octene-3-ol, 2-heptanone, heptanal, hexanal, (Z)-3-hexenyl acetate, (E,E)-2,4-decadienal, α-ionone, and phenylethyl alcohol. It was found that β-ocimene and (Z)-hex-3-enyl 2-methylbutyrate contributed greatly to the aroma characteristics of stir-fried green tea; 2-pentylfuran, phenylacetaldehyde and α-terpineol contributed greatly to the aroma characteristics of roasted green tea; and geranylacetone, γ-terpinene and α-citral contributed greatly to the aroma characteristics of sun-dried green tea. The results obtained from this study will help to understand the formation mechanism of green tea aroma quality and to develop directional processing and regulation technologies for green tea aroma quality.
Using Automatic Thermal Desorption Gas Chromatography-Mass Spectrometry to Detect Dynamic Changes of Environmental Volatile Components in Tieguanyin Oolong Tea during Fine Manipulation
BI Wanjun, WEI Zichun, ZHENG Yucheng, DENG Huili, NI Zixin, LIN Hongzheng, HAO Zhilong, SUN Yun
2023, 44(8):  201-211.  doi:10.7506/spkx1002-6630-20220511-144
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Automatic thermal desorption-gas chromatography-mass spectrometry (ATD-GC-MS) was used to capture and detect environmental volatile components in Tieguanyin tea at the key stages of the fine manipulation process, and short time series expression miner (STEM) and partial least squares-discriminant analysis (PLS-DA) were used to analyze the volatile components. The results showed that a total of 122 volatile components belonging to eight chemical classes, i.e., alcohols, esters, olefins, alkanes, aldehydes, aromatic hydrocarbons, ketones and other compounds were identified, esters being the major ones. The STEM results showed that the detected volatile components could be divided into 19 trends, and there was significant enrichment in two trend models. Among them, the levels of 2-butanol, ethyl acetate, isovaleraldehyde, 3-methyl-1-butanol, 1-hexanol, 2-heptanol, methyl hexanoate, 6-methyl-5-hepten-2-one, and octyl isobutyrate, which have a special aroma, increased significantly with increasing number of fine manipulation cycles. PLS-DA could effectively distinguish between tossing and sun withering, and seven characteristic volatile components (variable importance in the projection (VIP) > 1) were common to the two stages including (Z)-4-hexen-1-yl acetate, (E)-butanoic acid, 3-hexenyl ester, (E)-3-hexen-1-ol, 2-hexenal, 3-methyl-butanenitrile, (E)-4,8-dimethylnona-1,3,7-triene and (Z)-3,7-dimethyl-1,3,6-octatriene. The proportion and composition of environmental volatile components in Tieguanyin tea changed during the fine manipulation process. Most of the volatile components showed obvious and regular changes. The seven shared volatile components could be considered as aroma indexes for judging intelligent fine manipulation.
Differential Fingerprint Analysis of Volatile Compounds in Rice with Remained Germ Roasted to Different Degrees by Gas Chromatography-Ion Mobility Spectrometry and Principal Component Analysis
WANG Ziyan, DOU Boxin, JIA Jianhui, ZHANG Yu, LIU Ying, ZHANG Na
2023, 44(8):  212-218.  doi:10.7506/spkx1002-6630-20220424-308
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The volatile flavor substances of rice with remained germ roasted to different degrees were analyzed and compared by gas chromatography-ion mobility spectrometry (GC-IMS) combined with principal component analysis (PCA), with the aim of establishing fingerprints of volatile components of rice with different roasting degrees. The results showed that the volatile substances of rice samples with different roasting levels could be well separated by GC-IMS, and in total 61 flavor compounds were detected in four rice samples at all roasting stages. Aldehydes, esters and heterocyclic compounds contributed more to the characteristic flavor of roasted rice, while alcohols and ketones also contributed to the characteristic aroma components of roasted rice. The types and contents of aroma compounds of rice with different roasting degrees were significantly different. PCA showed that the GC-IMS spectra of volatile components differed among rice with different roasting degrees, and the cumulative contribution rates of the first two principal components were both 94%, indicating that the flavor fingerprints of rice samples at different roasting levels can be successfully established using GC-IMS.
Identification of Polyphenols in White Currant Fruit and Their Antioxidant Activity
HUO Junwei, GUO Wenrong, QIAO Jinli, QIN Dong, LIU Honglei, YAO Yueying, ZHANG Yan
2023, 44(8):  219-227.  doi:10.7506/spkx1002-6630-20220429-381
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Crude polyphenols were extracted from white currant fruit from the small berry resource garden in Northeast Agricultural University and purified by solid phase extraction (SPE) into polysaccharide, anthocyanin and non-anthocyanin fractions. The chemical composition as well as the contents of total phenols and total anthocyanins in each fraction was determined. 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation scavenging capacity, and ferric ion reducing antioxidant power (FRAP) were used to evaluate the antioxidant capacity of each fraction. The results showed that white currant fruit contained 78 non-anthocyanin polyphenols and only one anthocyanin polyphenol, corninin-3-glucoside, which can be used as a potential raw material for anthocyanin extraction. The contents of total phenols and total anthocyanins in the crude extract from white currant fruit were (34.93 ± 0.47) and (2.99 ± 0.98) mg/g, respectively. It had strong antioxidant capacity.
Analysis of Volatile Components in Chrysanthemum nankingense Leaves Dried by Different Methods by Headspace Solid Phase Microextraction-Gas Chromatography-Mass Spectrometry and Calculation of Odor Activity Value
WU Yuzhen, WANG Jieqiong, YU Haitao, YU Xiaoyu, YU Zhifang
2023, 44(8):  228-237.  doi:10.7506/spkx1002-6630-20220328-350
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To determine the effects of drying methods on the volatile compounds and explore the key aroma compounds in Chrysanthemum nankingense leaves, head-space solid phase micro-extraction combined with gas chromatography mass spectrometry (HS-SPME-GC-MS) was employed for quantitative and qualitative analysis of the volatile compounds in C. nankingense leaves dried by hot air drying, vacuum-freeze drying or microwave-hot air drying. The result showed that a total of 140 compounds belonging to six classes (terpenes, esters, aldehydes, alcohols, aromatic compounds and other substances) were identified in all samples. Of these, 112, 86, 83 and 85 were detected in fresh and dried C. nankingense obtained by hot air drying, microwave-hot air drying, and vacuum-freeze drying, respectively. Among these compounds, terpenes were the most abundant, with contents of 229 474.33, 64 629.68, 56 469.88 and 70 832.87 μg/kg in fresh, hot air dried, microwave-hot air dried, and vacuum-freeze dried samples, respectively. Compared with the other drying methods, vacuum-freeze drying gave better retention of the abundance of volatile compounds. Vacuum-freeze dried C. nankingense had similar flavor to fresh samples, showing camphor-like, turpentine-like, flowery and grassy aromas. GC-MS combined with odor activity values (OAVs) confirmed that β-ocimene, caryophyllene and trans-β-farnesene were the major aroma components. GC-MS combined with E-nose can represent an efficient nondestructive method for the detection of volatile compounds in C. nankingense leaves and allow the discrimination of dried C. nankingense obtained by different drying methods. These results provide a theoretical basis for choosing drying methods and understanding the difference in volatiles components in dried C. nankingense obtained by different drying methods.
Analysis of Phenolic Compounds and Antioxidant Enzyme Activity during the Growth and Metabolism of Red Raspberry Leaves
FAN Qing, LI Cheng, LI Ming, ZHANG Xuemei, ZHANG Jiao, WU Di, GU Yuhong, GUO Suping
2023, 44(8):  238-246.  doi:10.7506/spkx1002-6630-20220628-315
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In order to explore the changes in the content of phenolic compounds and the activity of antioxidant enzymes during the growth and metabolism of red raspberry leaves, the leaves of ‘Heritage’ and ‘Autumn Bliss’ red raspberry were analyzed and compared for the contents of total flavonoids and seven phenolic substances and the activities of three antioxidant enzymes. The results showed that from May to December, the content of ellagic acid and peroxidase (POD) activity in the upper, middle and lower leaves of the two varieties showed a double peak curve during the process of growth and metabolism, the content of salicylic acid showed a downward trend, the contents of ferulic acid, catechin, epicatechin, rutin and total flavones showed a single peak curve, the superoxide dismutase (SOD) activity remained at a high level, and the catalase (CAT) activity decreased, then increased and finally decreased again. The content of caffeic acid in the upper leaves of the two varieties showed a downward trend, while those in the middle and lower leaves showed a single peak curve. The highest contents of salicylic acid, ferulic acid, ellagic acid and epicatechin were determined in the upper leaves of ‘Autumn Bliss’ in May, upper leaves in June, middle leaves in July and upper leaves in July, which were 59.33 mg/100 g, 158.18 mg/100 g, 250.84 mg/g and 350.04 mg/100 g, respectively. The highest contents of rutin, caffeic acid, catechin and total flavonoids were determined in the lower leaves of ‘Heritage’ in June, middle leaves in July, middle leaves in July and upper leaves in July, which were 8.00 mg/100 g, 100.48 mg/100 g, 18.71 mg/g and 34.18 mg/g, respectively. The highest activities of POD, SOD and CAT were determined in the upper leaves of ‘Autumn Bliss’ in July, the lower leaves of ‘Heritage’ in July and the lower leaves of ‘Heritage’ in July, which were 13.05 U/(g·min), 37.00 U/g and 41.12 U/(g·min), respectively. In conclusion, the contents of phenolic substances and antioxidant enzyme activities in the leaves of ‘Heritage’ and ‘Autumn Bliss’ red raspberry are highest from May to July. This study provides an important theoretical basis for the timely harvest and better development and utilization of red raspberry leaves.
Comparative Analysis of the Effect of Pre-Harvest Bagging and Non-Bagging Treatment on Fruit Quality of ‘Younai’ Plum by UPLC-MS/MS and GC-IMS
LIN Yanjuan, ZHOU Danrong, FANG Zhizhen, CHEN Wenguang, YE Xinfu
2023, 44(8):  247-256.  doi:10.7506/spkx1002-6630-20220411-118
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In this study, ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and gas chromatography-ion mobility spectrometry (GC-IMS) combined with multivariate statistical analysis were used to analyze the effect of pre-harvest bagging on metabolites, metabolic pathways and volatile composition in ‘Younai’ plum fruit. The results showed that the peel and pulp of ‘Younai’ plum subjected to pre-harvest bagging treatment were yellow. By UPLC-MS/MS, 604 metabolites were identified, pre-harvest bagging changed the metabolic characteristics and pathways, and 58 significantly differential metabolites were selected, 22 and 36 of which were up-regulated and down-regulated, respectively. Among them, the contents of taste-related substances such as sugars and organic acids were not significantly different, and the contents of taste-active amino acids taste were significantly different between the bagging and non-bagging groups. By GC-IMS, 27 volatile substances were identified, including 14 aldehydes, 5 esters, 4 alcohols, 3 ketones and 1 other compounds. Most esters were more abundant in non-bagged fruits, while most alcohols were more abundant in bagged fruits. The fingerprints of volatile components in ‘Younai’ plum with pre-harvest bagging and non-bagging treatment were different. By searching against the Traditional Chinese Medicine System Pharmacology Database and comparing them with identified metabolites, 199 active ingredients were identified, and 37 key active ingredients were obtained according to the screening criteria. Among them, only quercetin was down-regulated in ‘Younai’ plum after pre-harvest bagging treatment. In conclusion, pre-harvest bagging can improve the appearance quality, but it may also have an effect on the taste-active, aroma-active and functional components of ‘Younai’ plum.
Compositions and Lipid-lowering Effects of Water Extract and Theabrownin from Ripe Pu-erh Tea Prepared by Controlled Fermentation
SHAN Bo, GONG Jiashun, WANG Qiuping, GAO Linrui, JIA Man, CHEN Dandan, DING Zhengjiao
2023, 44(8):  257-267.  doi:10.7506/spkx1002-6630-20220519-252
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The compositions of water extract (WE) and crude theabrownin (TB) extract from ripe Pu-erh tea prepared by controlled fermentation were analyzed by Curie point pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) and high performance liquid chromatography (HPLC) and their regulatory effects on obesity in rats were investigated. SD rats were divided into four groups, namely normal diet, high-fat diet, WE and TB. After gavage for 16 weeks, growth indexes, and serum biochemical indexes, oxidative stress and inflammation indexes were analyzed, and histopathological examination of liver tissues was performed by hematoxylin-eosin (HE) and oil red O staining. Results showed that theabrownin, protein and polysaccharide accounted for a large proportion in WE and crude TB. There were significant differences in the contents of catechin and its derivatives such as gallic acid (GA), epicatechin (EC) and epicatechin gallate (EGCG) between WE and crude TB extract (P < 0.05). The contents of the alkaloids caffeine and theobromine in WE were significantly higher than those in TB (P < 0.05). Seven and 12 compounds were shared by the Curie-point pyrolysis products of WE and TB at 380 and 600 ℃, respectively. In the four samples, the number of phenolic compounds was largest, and caffeine was the most abundant compound. Compared with the high-fat model group, the body mass and Lee’s index of the rats from the WE and TB groups significantly decreased (P < 0.05), and so did the levels of serum triglyceride (TG), serum fasting blood glucose (FBG), liver triglyceride and cholesterol (TC) ( P < 0.05), Moreover, fat accumulation was reduced, the levels of serum superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), nuclear factor E2 related factor 2 (Nrf2), interleukin-6 (IL-6), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α) were lowered significantly (P < 0.05). These findings indicate increased antioxidant activity and decreased inflammatory factor levels. Furthermore, histological observations of liver sections showed reduction in steatosis, the number of adipocytes and lipid droplet aggregation. To sum up, the compositions of WE and TB were significantly different; however, both showed a positive effect on mass loss and blood lipid reduction. This study can provide a theoretical basis for the deep processing of tea resources and the development of functional products.
Effect of Drying Methods on the Volatile Flavor Compounds of the Pileus and Stipe of Hypsizygus marmoreus
WANG Yonglun, LI Xing, YANG Miao, LIN Zina, DONG Xiaobo, XU Huaide
2023, 44(8):  268-276.  doi:10.7506/spkx1002-6630-20220607-065
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The effects of hot air drying (60, 70 and 80 ℃), freeze drying and natural air drying on the volatile flavor compounds in the pileus and stipe of Hypsizygus marmoreus were investigated by headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) and an electronic nose, and the contribution of flavor compounds to the overall flavor of dried samples was analyzed by relative odor activity value (ROAV). Results showed that there were marked differences in the electronic nose data of the ten dried samples; therefore, the electronic nose could effectively distinguish their volatile flavor. Moreover, 32, 41, 40, 53 and 48 volatile flavor compounds were identified in dried pileus obtained by hot air drying at 60, 70 and 80 ℃, freeze drying and natural air drying, respectively, and 34, 33, 33, 43 and 44 volatile flavor compounds in dried stipe obtained by hot air drying at 60, 70 and 80 ℃, freeze drying and natural air drying, respectively. The content of volatile flavor compounds in dried pileus was higher than that dried stipe with the same drying treatment, and hot air drying produced higher contents of new flavor compounds compared with natural air drying and freeze drying. In addition, 25 flavor compounds were obtained from ROAV analysis, among which trimethylamine, iso-valeraldehyde, and 1-octen-3-ol contributed more to the overall flavor. Furthermore, principal component analysis (PCA) was carried out on these 25 flavor compounds to generate a quality evaluation model. It was found that the pileus sample obtained by hot air drying at 80 ℃ had the highest score, indicating it had the best flavor quality.
Correlation Analysis of Amino Acids and Amino Acid-Derived Aroma Compounds of Chinese Kushui Rose Petals with Planting Locations
BA Lingzhen, WANG Bo, LEI Chunni, WANG Huijun, ZHANG Zhen, ZHOU Xiaoping, LI Jixin, JIANG Yumei
2023, 44(8):  277-283.  doi:10.7506/spkx1002-6630-20220402-024
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This study evaluated the correlation of amino acids and amino acid-derived aroma compounds in Chinese Kushui rose petals with soils from different planting locations. The composition of amino acids and amino acid-derived aroma compounds in rose petals from three different production areas (Kushui, Hongcheng and Datong towns) in Yongdeng, Gansu were analyzed by an automatic amino acid analyzer and solid phase micro-extraction combined with gas chromatography-mass spectrometry (SPME-GC-MS). The chemical composition and pH of soil samples from these areas were determined and the ion composition was measured by ion chromatography. The results showed that the petals of Chinese Kushui rose were rich in amino acids, with significant differences in the content of amino acids being among samples from different planting areas. Glutamate, alanine, lysine and proline were the major amino acids of all rose samples. The contents of glutamate, lysine and proline in rose samples from Datong were highest among the three production areas. A total of 11 amino acid-derived aroma substances were detected in the samples, with differences in their contents being observed among these samples. The content of amino acid-derived aroma substances was highest in rose from Datong. There was no significant similarity in physicochemical indexes among soils from the three production areas. SO42-, effective phosphorus and HCO3- were most affected by the region, and the soil properties were correlated with the contents of amino acids and amino acid-derived aroma components to different degrees.
Safety Detection
Ultra-high Performance Liquid Chromatography-Tandem Mass Spectrometry-Based Metabolomic Analysis of Primary Metabolites in ‘Fengtang’ Plum Fruits from Different Geographical Origins
ZHANG Qin, DONG Xiaoqing, LIN Xin, PENG Junsen, LUO Dengcan, HUANG Shi’an, ZHU Shouliang
2023, 44(8):  284-292.  doi:10.7506/spkx1002-6630-20220401-014
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Ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS)-based metabolomics was used to investigate primary metabolites in ‘Fengtang’ plum fruits from three production regions in Guizhou province. Multivariate statistical analyses such as principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) as well as metabolic pathway analysis were employed to explore the effect of the geographical origin on the primary metabolites of ‘Fengtang’ plum fruits. The results showed that a total of 307 metabolites were identified, and the geographic affected the type and content of metabolites in ‘Fengtang’ plum fruits. Meanwhile, 13 differential metabolites were identified between ‘Fengtang’ plum fruits from Liangtian and Liuma, and 49 differential metabolites were identified in ‘Fengtang’ plum fruits from Huishui versus Liuma, and Huishui versus Liangtian. In addition, the OPLS-DA results showed a clear discrimination between ‘Fengtang’ plum fruits from different geographical origins, and the samples showed an obvious clustering distribution, indicating that the geographical origin had a profound impact on the primary metabolites of ‘Fengtang’ plum fruits. Metabolic pathway analysis showed that the major mechanism for the difference in the primary metabolites of ‘Fengtang’ plum fruits from different production areas lay in the metabolism of amino acids, and it was found that the geographical origin imposed the most significant impact on amino acids. The results from this study can provide a theoretical basis for identifying and tracing the geographical origin of ‘Fengtang’ plum fruits.
Detection of Maillard Reaction Products at Different Stages in Prepackaged Foods by Ultra-high Performance Liquid Chromatography-Stable Isotope Dilution Mass Spectrometry
LI Huatao, ZHANG Qiaozhi, BAO Zongyu, CAI Qingting, NI Haojie, ZHENG Ruixing, ZHANG Shufen, CAO Lili, WANG Yanbo, FU Linglin
2023, 44(8):  293-300.  doi:10.7506/spkx1002-6630-20221026-272
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A method was developed for the simultaneous determination of seven Maillard reaction products (MRPs), namely Nε-(carboxymethyl)-lysine (CML), Nε-(carboxyethyl)-lysine (CEL), methyglyoxal-derived hydroimidazolones (MG-H1, MG-H2 and MG-H3), glyoxal-derived hydroimidazolone (G-H1) and furosine in prepackaged foods by ultra-high performance liquid chromatography-triple quadrupole-tandem mass spectrometry (UPLC-QqQ-MS/MS). The chromatographic separation was performed on a Kinetex C18 column and quantification was performed in the multiple reaction monitoring (MRM) mode. The recoveries of the method ranged from 88.4% to 111.3% with relative standard deviations (RSDs) less than 9% in terms of precision, and the limit of detection and the limit of quantification were 2.1–14.2 and 7.4–41.2 ng/mL, respectively. The developed method was applied to 134 typical prepackaged foods, and the obtained data was analyzed by principal component analysis (PCA) and correlation analysis (CA). The results showed that CML, MG-H1/3, MG-H2 and G-H1 were the major MRPs in prepackaged foods, and they had significant positive correlations with each other and with protein, fat and total sugar contents. This method shows acceptable linearity, accuracy and precision and is suitable for the rapid determination of multiple MRPs in prepackaged foods.
Rapid Determination of Acid and Peroxide Values in Frozen Pork by Using Raman Spectroscopy
BAI Jing, ZANG Mingwu, QIAO Xiaoling, ZHAO Jiansheng, ZOU Hao, WU Jiajia, XU Chenchen, SHI Yuxuan, WANG Shouwei, ZHAO Yan
2023, 44(8):  301-306.  doi:10.7506/spkx1002-6630-20220422-286
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The rapid detection of lipid oxidation in frozen pork was carried out by using Raman spectroscopy combined with chemometric methods. Frozen pork stored for 0–360 days was selected in this study, and the regression relationship between acid value or peroxide value and storage time was established by the least squares method. Raman spectra were collected with a portable Raman spectrometer and were preprocessed by Savitzky-Golay with five-point smoothing (SG-5), standard normal variate correction (SNV) or adaptive iteratively re-weighted penalized least squares (airPLS). The partial least square regression (PLSR) was used for modeling and analysis. Then competitive adaptive reweighted sampling (CARS) was used to select the Raman characteristic variables for the best preprocessed spectra to establish a CARS-PLSR model. It was found that the correlation between peroxide value and storage time was more significant during the storage period (P = 0.000 3 < 0.05). The prediction models with spectral preprocessing by using SNV and airPLS performed best. The CARS-PLSR model showed improved prediction performance. The CARS-PLSR models for prediction of acid and peroxide values had the following performance parameters: coefficient of determination for calibration (R2c), 0.88 and 0.84; root mean square error of cross-validation (RMSECV), 0.31 and 2.33; coefficient of determination for prediction (R2p), 0.76 and 0.75; root mean square error of prediction (RMSEP), 0.17 and 1.87, and ratio of performance to deviation (RPD), 2.59 and 1.90, respectively. In conclusion, our results show that the peroxide value of frozen pork is significantly correlated with storage time. The degree of lipid oxidation in frozen pork can be rapidly determined by using Raman spectroscopy.
Rapid Detection of Procymidone in Vegetables by Nanobody-Based Colloidal Gold Immunochromatography Assay
HE Xiaoting, CHEN Zijian, HUANG Song, XIAO Zemiao, LIU Jia, ZHONG Min, WANG Hong, SHEN Yudong, XU Zhenlin
2023, 44(8):  307-316.  doi:10.7506/spkx1002-6630-20220218-143
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To explore the feasibility of applying nanobodies in colloidal gold immunochromatography assay (GICA) for small-molecule harmful substances, this study systematically investigated the effects of colloidal gold labeling parameters, colloidal gold working buffer and sample pretreatment methods on GICA using the pesticide procymidone as a model. The results showed that the size of colloidal gold particles, labeling pH and the amount of antibody used were the key factors to ensure the stability of the nanobody-gold-labeled probes. Under the optimal conditions, the limit of detection, half-maximal inhibitory concentration (IC50) and visual detection limit of GICA for procymidone were 0.44, 6.29 and 200 μg/L, respectively. The sensitivity was 5.1-fold higher than that of conventional monoclonal antibody-based GICA. The quick, easy, cheap, effective, rugged and safe (QuEChERS) procedure was used for the pretreatment of Chinese leek, cucumber and tomato samples. Based on the excellent organic solvent tolerance of nanobodies, the organic solvent blow-drying procedure was omitted. The average recoveries of the spiked samples ranged from 80.1% to 109.6%, and the results for the actual samples were consistent with those of gas chromatography-mass spectrometry (GC-MS). This study showed that nanobodies are a potential alternative to conventional antibodies for immunoassays for the rapid detection of small molecules. The proposed nanobody-based GICA can be used for the rapid screening of procymidone in vegetables with the advantages of high sensitivity, high accuracy, rapidity and simplicity.
Establishment and Application of Multiplex Real-Time PCR Method for Rapid Detection of Four Animal-Derived Components in Donkey Meat Products
FAN Wei, GAO Xiaoyue, LI Henan, DONG Yuxin, LIU Hongyu, LI Yuxuan, GUO Wenping
2023, 44(8):  317-323.  doi:10.7506/spkx1002-6630-20220406-056
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A multiplex real-time polymerase chain reaction (PCR) method for simultaneous rapid detection of donkey-, horse-, pig- and duck-derived components was established. For this purpose, the Nad5, ATpase6, ATP8 and cytb were used as target genes to design specific primers and Taqman probes, and the 18S rRNA gene was used as internal reference gene. The developed method was validated and applied to detect simulated adulterated meat products, simulated processed meat products and actual donkey meat samples. This method was characterized by high-throughput, and excellent sensitivity and specificity. The system had no cross-reaction to non-target sources when the cycle threshold (Ct) value did not exceed 35.0. The sensitivity was 2 × 10-4 ng/μL of template DNA. The detection limit for raw and cooked meat was 0.001% and 0.01% of the meat content, respectively. The results of this method for 100 actual samples were consistent with those of the national standard method, indicating that the multiplex real-time PCR method can be used for the detection of commonly adulterants in meat and meat products.
Simultaneous Determination of Eugenol and Its Five Derivatives in Aquatic Products by Ultra-high Performance Liquid Chromatography-Tandem Mass Spectrometry Combined with Quick, Easy, Cheap, Effective, Rugged and Safe Extraction
LIN Chen, WU Min, WANG Kai, ZENG Sanmei, WU Jiawen, ZHONG Liping, LING Songjiang
2023, 44(8):  324-329.  doi:10.7506/spkx1002-6630-20220818-218
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An ultra-high performance liquid chromatography-tandem mass spectrometric (UPLC-MS/MS) method was developed for the simultaneous determination of eugenol and its five derivatives including isoeugenol, methyl eugenol, methyl isoeugenol, acetyl eugenol and acetylisoeugenol in aquatic products. The samples were extracted with acetonitrile, and then the extracted supernatant was cleaned up with 50 mg of primary secondary amine (PSA) and 100 mg of C18 and 150 mg of MgSO4. Separation of the targets was performed on a Kinetex C18 (2.1 mm × 100 mm, 2.6 μm) chromatographic column by gradient elution using a mobile phase of water and methanol. The six eugenol derivatives were detected using an electrospray ionization (ESI) source with fast switching between the positive and negative ionization modes in the multiple reaction monitoring (MRM) mode, and quantified by the internal standard method using eugenol-D3 as the internal standard (IS). The calibration curves showed a good linearity in the range of 2–100 ng/mL for eugenol and isoeugenol, and 1–100 ng/mL for four other eugenol derivatives with correlation coefficient (r) ≥ 0.999. The average recoveries of spiked samples were between 67.0% and 106.4% with relative standard deviations (RSDs) of 1.2%–15.7%. The limits of detection (LOD, RSN = 3) and quantitation (LOQ) were 0.5–1.5 and 2.0–5.0 μg/kg, respectively. The method is an accurate, rapid and reliable assay for the detection of eugenol and its derivatives in aquatic products.
Preparation of Graphene-Incorporated Chitosan-Polyvinyl Alcohol Composite Film Loaded with Copper-1-(2-Pyridylazo)-2-naphthol Complex and Its Application to Monitor Shrimp Freshness
GUO Yaping, CHEN Linmin, CHEN Quansheng, CHEN Xiaomei
2023, 44(8):  330-336.  doi:10.7506/spkx1002-6630-20220412-143
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A colorimetric composite film (Cu-PAN@G-CS/PVA) for the detection of H2S in shrimp meat by indicator displacement was prepared by tape casting method using copper (II)-1-(2-pyridylazo)-2-naphthol complex (Cu-PAN) as a H2S-sensitive material, chitosan (CS) combined with polyvinyl alcohol (PVA) as a film-forming material and graphene as a sensitizing material. The morphology and functional groups of Cu-PAN@G-CS/PVA were investigated by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR), and the sensing performance to H2S was examined by ultraviolet-visible (UV-vis) absorption spectroscopy. Experimental results showed that the color of the Cu-PAN@G-CS/PVA film changed from purplish red to yellow with increasing H2S concentration. This film was used to monitor the freshness of Penaeus chinensis stored at 4 or 25 ℃. It was shown that the trend of the color difference value (ΔE) of the Cu-PAN@G-CS/PVA film had a good correlation with the total volatile basic nitrogen (TVB-N) content of the sample. Therefore, the Cu-PAN@G-CS/PVA film could accurately and rapidly indicate the freshness of P. chinensis, which may provide a reference for the development of intelligent packaging of aquatic products.
Determination and Health Risk Assessment of 3-Chloropropanol and Glycidyl Esters in Infant Formula Milk Powder by Gas Chromatography-Tandem Mass Spectrometry
HAO Yu, MA Yiying, YU Litao, LI Guangzhi, WEI Zhichun, LIU Shuping, SHI Changbo
2023, 44(8):  337-344.  doi:10.7506/spkx1002-6630-20220419-240
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A gas chromatography-tandem mass spectrometry (GC-MS/MS) method for the detection of 3-chloropropanol and glycidyl esters in infant formula milk powder was established, and the content of 3-chloropropanol and glycidyl esters in different commercial infant formula milk powders was determined. Ester contamination and health risk assessment in infant formula milk powder was carried out. 3-Chloropropanol and glycidyl esters in samples were extracted with n-hexane, hydrolyzed, derivatized with phenylboronic acid, detected by GC-MS/MS, and quantified by an internal standard method. The results showed that the total amount of 3-chloropropanol and glycidyl esters was in the range of 0.040 0–4.00 μg/mL, and good linearity was observed for 3-chloropropanol esters in the concentration range of 0.020 0–2.00 μg/mL with correlation coefficient (R2) greater than 0.999. The limit of detection (LOD) was 10.0 μg/kg, and the limit of quantification (LOQ) was 25.0 μg/kg for both esters. At spiked levels of 25.0, 100 and 300 μg/kg, the average recoveries ranged from 95.0% to 98.1%. The developed method had high accuracy and recovery, and could be used for the detection of 3-chloropropanol and glycidyl esters in infant formula milk powder. In 150 commercial infant formula milk powder samples, the detection rate of 3-chloropropanol esters was 12.7% at levels of ND–52.4 μg/kg with an average of 29.8 μg/kg. The detection rate of glycidyl esters was 6.67% at levels of ND–40.1 μg/kg with an average of 31.9 μg/kg. The average exposure level to 3-chloropropanol esters was 0.33–0.66 μg/(kg·d). Therefore, attention should be paid to the problem of contamination of 3-chloropropanol and glycidyl esters in infant formula milk powder.
Development of a Dual-Probe Competitive Enzyme-Linked Immunosorbent Assay Based on Magnetic Nanoparticles for the Detection of Fumonisin B
SUN Yu, MENG Xianmei, LIN Chao, LI Bing, ZHANG Liang
2023, 44(8):  345-351.  doi:10.7506/spkx1002-6630-20220402-021
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In this study, a dual-probe competitive enzyme-linked immunosorbent assay (ELISA) based on magnetic nanoparticles for the simultaneous detection of fumonisin B1 (FB1), FB2 and FB3 in maize samples was established. A magnetic capture probe (MNPs-FB1) was synthesized by the active ester method, and a monoclonal antibody-horseradish peroxidase (McAb-HRP) probe was prepared by a modified sodium periodate method. The reaction conditions of the assay were optimized. The linear ranges for FB1 and the total amount of FB1, FB2 and FB3 (FBs) were 0.07–1.98 and 0.10–9.86 ng/mL, respectively. The average recoveries of FBs from spiked maize samples ranged from 86.2% to 105.1%. The correlation coefficient between the results of the developed assay and those of liquid chromatography-tandem mass spectrometry (LC-MS/MS) was 0.996 6. These results suggest that this assay is characterized by rapidity, high accuracy and good repeatability and provides a new method for the detection of FBs in maize samples.
Optimization and Application of Ultra-high Performance Liquid Chromatography-High Resolution Mass Spectrometry for Determination of the Bitter Compound Trihydroxyoctadecenoic Acid in Chinese Baijiu
YANG Junlin, TIAN Dongwei, YIN Yanyan, JIANG Lili, LI Lulu, ZHANG Erkang, HU Feng, CHENG Pingyan
2023, 44(8):  352-359.  doi:10.7506/spkx1002-6630-20220614-140
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An ultra-high performance liquid chromatography-high resolution mass spectrometric (UPLC-HRMS) method was developed, optimized and applied to analyze the bitter compound trihydroxyoctadecenoic acid in Chinese baijiu. The samples were diluted and filtered through a 0.22 μm membrane before analysis. Acetonitrile was selected as the organic phase and 0.1% formic acid as the aqueous phase with a flow rate of 0.3 mL/min and an injection volume of 2 μL. The analyte was separated on a Hypersic Gold (100 mm × 2.1 mm, 1.9 μm) column by gradient elution, and qualitative analysis was achieved by comparison of secondary daughter ions and theoretical simulation of molecular ion fragment structures using the Mass Frontier 8.0 software, which could avoid false positive results. This method had the advantages of simple pretreatment, fast analysis, low detection limit (0.2 ng/mL) and high accuracy, and could meet the requirements for the detection of baijiu samples. This method was used to study the change in the content of trihydroxyoctaenoic acid during the production process of Maotai-flavor baijiu. The results showed that with the prolongation of fermentation time, a large amount of linoleic acid in the raw materials was likely to be oxidized and decomposed into trihydroxyoctadecenoic acid, and then transferred into the base liquor by distillation. The content of trihydroxyoctadecenoic acid in the base liquor did not obviously change during storage, indicating that it was affected little by storage time. The content of trihydroxyoctadecenoic acid in Maotai-flavor base liquor was lowest among the three typical bodies of Maotai-flavor baijiu, so Maotai-flavor base liquor could be used as one of the major base liquors for packaged products.