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15 January 2024, Volume 45 Issue 1
Food Chemistry
Differences in In Vitro Digestibility of Curcumin Nanoemulsions Stabilized by Whey Protein Isolate and Whey Protein Isolate-(–)-Epigallocatechin-3-gallate
LI Yanxin, CHEN Liying, LI Yan, XIE Xin’an, LI Lu
2024, 45(1):  1-7.  doi:10.7506/spkx1002-6630-20230228-256
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In this study, the release of free fat acids (FFA) from and the digestion characteristics of curcumin nanoemulsions constructed using whey protein isolate (WPI)-(-)-epigallocatechin-3-gallate (ECGG) graft copolymers with 3% and 4% grafting degrees as emulsifiers were investigated during in vitro simulated digestion and compared with those of curcumin nanoemulsions stabilized by WPI. It was found that binding to EGCG might cause the unfolding of WPI, and the interfacial film thickness of the WPI-EGCG stabilized emulsion increased by 31.6 nm compared with that of the WPI stabilized emulsion. The WPI-EGCG complex stabilized emulsion had a smaller particle size dispersion and average particle size than the WPI stabilized emulsion and was therefore more stable and superior in promoting lipid digestion. After 120 minutes of intestinal digestion, the final release rate of FFA from the nanoemulsion stabilized with 4% WPI-EGCG was 85.13%. Also, the graft treatment improved the bioaccessibility of curcumin encapsulated in the system.
Effect of Adenosine 5’-Diphosphate Ribosylation on Meat Quality of Qinchuan Cattle
FU Qihua, LI Yalei, LUO Ruiming, WANG Xuerong, MA Xuhua
2024, 45(1):  8-14.  doi:10.7506/spkx1002-6630-20230308-076
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This study addressed the effect of adenosine 5’-diphosphate (ADP) ribosylation on the mitochondrial function and quality of Qinchuan cattle meat during early postmortem aging. The Longissimus dorsi muscle of Qinchuan cattle treated with 20 µmol/L rucaparib, a poly(ADP-ribose) polymerase 1 (PARP1) inhibitor, were evaluated for mitochondrial indices, myofibrillar fragmentation index (MFI), shear force, pH, and other quality indices after being stored for 0 h, 6 h, 12 h, 2 d, 4 d, and 8 d and the expression levels of PARP1 and desmin were detected using Western blot. The results showed that the content of reactive oxygen species (ROS) in the treated group was significantly lower than that in the control group (P < 0.05) during 0 h–8 d (except 12 h) after slaughter. The caspase-3 activity and MFI in the treated group were significantly lower than those in the control group (P < 0.05) during 0–12 h. Mitochondrial membrane potential during 2–4 d as well as succinate dehydrogenase (SDH) activity during 4–8 d were significantly higher in the treated group than in the control group (P < 0.05). These findings indicate that PARP1 inhibition, which characterizes ADP ribosylation, can slow down the decrease in mitochondrial membrane potential and increase SDH activity, preserving mitochondrial function to some extents and delaying the decrease in MFI and the degradation of desmin and thereby meat tenderization.
Physicochemical Properties, Structural Characterization, Immunoenhancing and Hypoglycemic Activities of Fucoidan Extracts from Two Sargassums Species
CHEN Shutong, ZHOU Qingling, YANG Ruiyu, WANG Xiaoxiao, DING Rui, LI Rui, LUO Lianxiang, ZHONG Saiyi,
2024, 45(1):  15-22.  doi:10.7506/spkx1002-6630-20230202-015
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In this study, the chemical compositions, structures, immunomodulatory and hypoglycemic activities of fucoidans from Sargassum zhangii (SZ-Fuc) and Sargassum hemiphylla (SH-Fuc) were analyzed and compared. The results showed that the sulfate group content and molecular mass of SZ-Fuc were (29.74 ± 0.01)% and 111.28 kDa, respectively, and SZ-Fuc had a relatively loose surface structure. The main chain of SZ-Fuc was composed of (→1) linked fucose, xylose, glucose, mannose and galactose, (1→3)- and (1→4)- linked xylose, (1→2)-linked mannose, (1→3)-, (1→4)- and (1→6)-linked galactose, and (1→4)- and (1→6)-linked glucose. Meanwhile, the sulfate group content and molecular mass of SH-Fuc were (44.11 ± 0.01)% and 1 166.48 kDa, respectively, SH-Fuc had a compact surface structure, and its main chain contained (→1), (1→3)- and (1→4)-linked fucose, (→1), (1→4)- and (1→6)-linked glucose, (→1) and (1→2)-linked mannose, and (1→4)-linked galactose. Besides, both SZ-Fuc and SH-Fuc had branched structures. They significantly increased NO release from RAW264.7 cells and improved the protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), indicating good immunomodulatory activity. The immunomodulatory activity of SZ-Fuc was better than that of SH-Fuc, while the inhibitory effect of SH-Fuc on α-glucosidase was better than that of SZ-Fuc, suggesting that SH-Fuc had better hypoglycemic potential. This study can provide a theoretical basis for polysaccharides from S. zhangii and S. hemiphylla in the development of functional and nutritional foods with immunomodulatory and blood glucose-reducing activity.
Effect of Covalent Conjugation with Polyphenols by Free Radical Method on Gel Properties of Soybean Protein-Stabilized Emulsion
MENG Ganlu, CHU Yunan, WU Yi, WANG Jubing, JIN Hua, XU Jing
2024, 45(1):  23-31.  doi:10.7506/spkx1002-6630-20230327-252
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In this study, a covalent conjugate between ferulic acid (FA) and soybean protein isolate (SPI) was prepared by free radical method and was used to prepare gluconolactone (GDL)-induced emulsion gels. The effects of covalent binding to FA on SPI structure, emulsion properties and emulsion gel characteristics were investigated. The optimum concentration of FA was determined as 150 μmol/g protein based on intermolecular forces, textural properties, and water-holding capacity of SPI-FA (SFA) stabilized emulsion gels. Under this condition, spectral analysis showed that FA had a fluorescence quenching effect on SPI, and after covalent binding to FA, a decrease in the β-folded content and an increase in the α-helix, β-turn and random coil contents of SPI appeared. The absolute value of zeta potential and interfacial protein content of SFA stabilized emulsions increased, and the mean particle size and apparent viscosity decreased. The final storage modulus (G’) of SFA stabilized emulsion gels increased, and the changes in relaxation times and peak ratios observed in low-field nuclear magnetic resonance (NMR) measurements indicated that the SFA stabilized emulsion gels had better hydration properties. Moreover, they had a more uniform and dense porous network structure. These results show that SPI covalently bound to 150 μmol/g protein of FA is valuable in the preparation of emulsion gels.
Different Solvent Extracts from By-products of Corylus heterophylla Fisch. × Corylus avellana L.: Bioactivity Evaluation and Phenolic Composition Analysis by Ultra-high Performance Liquid Chromatography-Mass Spectrometry
SU Kexin, ZHAO Yuhong
2024, 45(1):  32-41.  doi:10.7506/spkx1002-6630-20230225-230
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Phenolics were extracted from the by-products (leaves, green leafy covers, shells, branches and seed coats) of the hybrid hazelnut Corylus heterophylla Fisch. × Corylus avellana L. using four different polar solvents (water, methanol, 80% ethanol and ethyl acetate) and their antioxidant, hypoglycemic and anti-inflammatory activities were evaluated in vitro. The phenolics were identified by ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS). The leaf and branch extracts showed stronger antioxidant, hypoglycemic and anti-inflammatory activities in vitro than the extracts from green leafy covers, shells and seed coats. The biological activities were largely correlated with total phenols and proanthocyanidins in the by-products of hazelnut. The methanol extract of hazelnut branches had the highest content of total phenols (calculated as gallic acid equivalent per dry mass) and procyanidins (calculated as proanthocyanidin equivalent per dry mass), which were (37.13 ± 0.22) and (2.27 ± 0.04) mg/g, respectively. The content of total flavonoids (calculated as rutin equivalent per dry mass) in the 80% ethanol extract of hazelnut leaves was the highest, which was (18.21 ± 1.37) mg/g. For each plant part, the contents of total phenols, total flavonoids and proanthocyanidins in the ethyl acetate extract were lower than those in the other solvent extract, but the ethyl acetate extract inhibited the activities of α-amylase and lipoxygenase significantly (P < 0.05). The ethyl acetate extract of green leafy covers had the best inhibitory effect on α-amylase, while the ethyl acetate extract of leaves showed the strongest inhibitory activity on lipoxygenase. According to UPLC-MS analysis, the majority of phenolic compounds in hybrid hazelnut by-products were flavonoids along with many bioactive compounds such as terpenes, alkaloids, lignans and organic acids. Bioactive ingredients in hybrid hazelnut by-products have the potential to be used in functional foods or pharmaceuticals.
Bioengineering
Non-targeted Metabolomics Analysis of Metabolic Differences among Liuyang Douchi Fermented by Different Strains
LIU Jingjing, DENG Gaowen, HU Jialiang, QIN Yeyou, LIU Yang, JIANG Liwen
2024, 45(1):  42-49.  doi:10.7506/spkx1002-6630-20230227-246
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In order to investigate the metabolic differences among Liuyang Douchi fermented by different starter cultures, the contents of total acid and amino nitrogen in Douchi fermented naturally and by using Aspergillus flavus 7214 (AF 7214), A. flavus 7622 (AF 7622), their mixture (AF 7214 + AF 7622) or A. orzyae were determined, and the difference in metabolites among these fermentation strategies was explored by liquid chromatography-mass spectrometry (LC-MS). The results showed that among the five Douchi samples, Douchi fermented by AF 7214 had the highest contents of total acid (3.52%) and amino nitrogen (1.47 g/100 g). The results of partial least squares discriminant analysis (PLS-DA) indicated that significant differences in metabolites were observed among the Douchi samples, and the composition of metabolites in Douchi fermented by AF 7622 showed the smallest difference from that in naturally fermented Douchi. Further analysis revealed that the differential metabolites between Douchi fermented naturally and by using starter cultures were mainly involved in amino acid metabolic pathways, especially arginine biosynthesis. A total of 62 key differential metabolites among the five samples were identified using variable importance in the projection (VIP) greater than 1.5 and P < 0.05 as criteria, including 26 amino acids and their derivatives such as L-lysine, L-serine and 2-methylserine, which indicated that enhanced fermentation showed the most notable influence on the metabolism of amino acids. This study has provided a new understanding of the formation of metabolites during the enhanced fermentation of Liuyang Douchi.
Transcriptomic Analysis of Chilled Tan Lamb
CHEN Xueyan, YANG Bo, LUO Ruiming, ZHANG Qian, WANG Jinxia, LI Rong, HU Lijun
2024, 45(1):  50-57.  doi:10.7506/spkx1002-6630-20230404-037
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This study was performed in order to uncover the molecular mechanism by which postmortem glycolysis affects meat quality traits for the purpose of promoting the research and development of prediction technologies for the quality change of chilled Tan lamb and promoting the improvement of its processing, storage and transportation technologies. High-throughput sequencing technology was used for transcriptome sequencing and analysis of the hind leg meat from Yanchi Tan lambs after 0, 4 and 8 days of chilling. The results showed that the differential expression genes (DEGs) were mainly enriched in cellular amide metabolism, ATP metabolism, skeletal muscle contraction and ribosomes and involved in glycolysis, ribosomes and the p53 signaling pathway, and these DEGs constituted a key part of muscle cell function. The phosphofructokinase (PFKM), glyceraldehyde-3-phosphate dehydrogenase (GADPH), phosphoglycerate mutase 2 (PGAM2), enolase 3 (ENO3) and pyruvate kinase (PKM) genes were the core genes involved in the glycolytic metabolism of Tan lambs, which changed meat quality mainly by affecting the structure of muscle fibers, the degradation degree of structural proteins, the activity of glycolytic enzymes, the production of ATP and the activity of complexes.
Preparation and Identification of α-Amylase Inhibitory Peptides from Mung Bean Protein
LI Yongfu, WANG Yaru, HUANG Jinrong, SHI Feng
2024, 45(1):  58-64.  doi:10.7506/spkx1002-6630-20230314-141
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In this study, sequential hydrolysis with pepsin followed by trypsin was conducted on total protein and protein fractions from mung bean. The difference in α-amylase inhibitory activity among the resulting hydrolysates was compared and the underlying reason was analyzed in terms of degree of hydrolysis, amino acid composition and molecular mass. The results showed that the total protein hydrolysate had the highest α-amylase inhibitory activity (16.51%). Compared with its fractions, the total protein showed the highest content of hydrophobic amino acids (32.68%) and degree of hydrolysis (6.28%), and the molecular mass of its hydrolysate was the lowest (< 20 kDa). Therefore, the total protein was selected to prepare α-amylase inhibitory peptides. Finally, 17 peptides with potential α-amylase inhibitory activity were discovered by the isolation and identification of peptides from mung bean protein. This study suggests that mung bean protein is a better food source of α-amylase inhibitory peptides than its protein fractions, which can be used in blood glucose-lowering functional foods or drugs.
Separation and Identification of Umami Peptides from the Enzymatic Hydrolysate of Stropharia rugosoannulata and Their Synergistic Umami-Enhancing Effect
CHEN Rongrong, LI Wen, WU Di, ZHANG Zhong, BAO Dapeng, CHEN Wanchao, ZHANG Jingsong, YANG Yan
2024, 45(1):  65-74.  doi:10.7506/spkx1002-6630-20230222-203
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Umami peptides from the enzymatic hydrolysate of Stropharia rugosoannulata were separated by ultrafiltration (UF) and gel filtration chromatography (GFC) combined with sensory evaluation and electronic tongue analysis. Fraction F3, with the strongest umami intensity, were identified by reversed-phase high performance liquid chromatography-tandem mass spectrometry (RP-HPLC-MS/MS). The identified peptides were synthesized and evaluated for their taste characteristics. The results showed that eight umami peptides were identified in fraction F3, namely ELWR, RLVDR, KPDNR, AHLRF, LDWDR, LAEWR, DDWWR and EGHKGW, and all of them possessed umami characteristics and umami-enhancing effects with thresholds ranging from 0.30 to 1.33 mmol/L and from 0.53 to 2.43 mmol/L, respectively. All peptides except LDWDR showed different degrees of umami improvement in monosodium glutamate (MSG) solution, ranging from 0.18% to 61.12%. ELWR, RLVDR, KPDNR, AHLRF and EGHKGW showed good umami-enhancing effects at low concentrations. The peak concentration of RLVDR and KPDNR for synergistic umami-enhancing effect was 5 mg/mL. LDWDR, LAEWR, DDWWR and EGHKGW reached the umami peak at 4 mg/mL. The amino acid composition and the spatial structure of umami peptides could affect their taste properties. The results of this study provide a theoretical basis for the development and utilization of umami peptides from S. rugosoannulata.
Component Analysis
Variation in Contents of Iodine Species in Kelp during Blanching-Salting Process
ZHAO Ruyue, YU Yuan, ZHANG Yating, JIANG Yongyi, LIU Xiaofang, GUO Yingying, MIAO Junkui, LENG Kailiang
2024, 45(1):  75-81.  doi:10.7506/spkx1002-6630-20221213-136
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In this study, the contents of four iodine forms, including iodide ion (I−), iodate (IO3−), mono-iodotyrosine (MIT) and diiodotyrosine (DIT), were determined in the blanching water, rinsing water, saline water and processed kelp to study the dissolution patterns of iodine forms during the blanching, rinsing and salting of kelp. The I− contents in fresh, blanched, primarily rinsed and secondarily rinsed kelp were 1 689.41–8 753.24 mg/kg, and the contents of IO3− ranged from 42.67 to 442.00 mg/kg. The contents of MIT and DIT ranged from 698.22 to 861.90 mg/kg and 123.97 to 158.67 mg/kg, respectively. During the blanching process, the dissolution rates of I−, MIT and DIT were the highest, which were (64.38 ± 2.99)%, (19.35 ± 0.97)% and (6.55 ± 0.53)%, respectively. With increasing kelp addition, the contents of I−, MIT and DIT in the blanching, rinsing and saline water first increased and then leveled off, and the content of IO3− in all waters showed a monotonously increasing trend. With increasing number of kelp rinsed, the dissolution rate of I− decreased first and then basically remained unchanged. Compared with fresh kelp, the dissolution rate of I− in the first rinsed kelp decreased by (80.72 ± 2.66)%, and iodine was released into water mainly in the form of I−, with the maximum release being recorded during the blanching process.
Changing Pattern of Characteristic Components in Black Garlic during Processing Analyzed by Ultra-high Performance Liquid Chromatography-Triple Quadrupole Tandem Mass Spectrometry
WU Peng, LIU Pingxiang, WANG Yutao, GAO Rui, JIANG Yuying, BI Jingxiu, WANG Zhengrong
2024, 45(1):  82-90.  doi:10.7506/spkx1002-6630-20230329-292
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An analytical method based on ultra-high performance liquid chromatography-triple quadrupole tandem mass spectrometry (UPLC-TQ-MS/MS) was established for the simultaneous determination of 10 flavor precursors and 21 free amino acids in black garlic. The method was applied for exploring the changing pattern of characteristic components in black garlic during processing. The results showed that the characteristic components in black garlic changed significantly during processing at 75 ℃ and 85% relative humidity. Among them, γ-aminobutyric acid, S-allyl-L-cysteine, isoalliin, glutamine, methiin, alliin, tryptophan, and γ-L-glutamyl-S-allyl-L-cysteine changed most obviously, and were identified as the chemical markers of changes in small molecular metabolites during the processing of black garlic. The established method has high sensitivity and accuracy, and can meet the detection requirements.
Effect of Steam Explosion on the Aroma Characteristics of Tea Produced from Tender and Mature Leaves of Eucommia ulmoides Analyzed Using Electronic Nose and Headspace Solid-Phase Microextraction Combined with Gas Chromatography-Mass Spectrometry
ZHOU Yunfei, SUN Zhiqiang, DU Qingxin, WANG Zhiyong, WANG Lu, DU Hongyan, DU Lanying
2024, 45(1):  91-100.  doi:10.7506/spkx1002-6630-20230519-193
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In order to investigate the differences in volatile components and major aroma characteristics between tea made from tender and mature leaves of Eucommia ulmoides pre-treated by steam explosion (SE), an electronic nose (E-nose) and headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry (HS-SPME-GC-MS) were applied to analyze the effect of SE on the volatile components in tea made from tender and mature leaves of the Eucommia ulmoides cultivar ‘Huazhong 8’. The results showed that the principal component analysis (PCA) and linear discriminant analysis (LDA) models fitted well the E-nose data, which suggested that the aroma characteristics of both tender and mature leaf tea were significantly different between with and without SE pretreatment. Altogether, 177 volatile components were identified by HS-SPME-GC-MS, among which 24 were selected as aroma active substances by orthogonal partial least squares discriminant analysis (variable importance in the projection (VIP) value ≥ 1) and Kruskal-Wallis H test (P < 0.05). The key aroma substance of tender leaf tea without SE was dihydroactinidiolide. The key aroma substances of tender leaf tea with SE were dihydroactinidiolide, nonanal, benzaldehyde and phenylacetaldehyde, contributing to citrus-like, flowery, caramelic, bitter almond-like, nutty, rose-like and chocolate-like aromas. No key aroma substances were found in mature leaf tea without SE, while dihydroactinidiolide and nonanal were identified the key aroma substances in mature leaf tea with SE, contributing to sweet peach-like, woody, citrus-like, flowery and caramelic aromas. The results of this study can provide a reference for the development of beverage products based on Eucommia ulmoides leaves.
Analysis of Key Aroma Components of Three Representative Oolong Tea Varieties by Stir Bar Sorptive Extraction Combined with Gas Chromatography-Olfactory-Mass Spectrometry
HUANG Huiqing, ZHENG Yucheng, HU Qingcai, WU Qingyang, YANG Yun, OU Xiaoxi, ZHAO Mengying, SUN Yun
2024, 45(1):  101-108.  doi:10.7506/spkx1002-6630-20230519-185
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Stir bar sorptive extraction (SBSE) combined with gas chromatography-olfactory-mass spectrometry (GC-O-MS) was used to identify and describe the key aroma components of three representative oolong tea varieties, Huangdan, Tieguanyin and Jinguanyin. Comparative analysis was conducted in terms of odor activity value (OAV), aroma character impact (ACI) value and sensory evaluation. The sensory evaluation showed that each variety showed obvious aroma characteristics. Huangdan oolong tea had an obvious floral aroma as well as a slight milky aroma. Tieguanyin oolong tea had a strong floral aroma. Jinguanyin oolong tea had a sweet fruity aroma as well as a slight woody aroma. According to the results of OAV and GC-O-MS analysis, geraniol, phytol, methyl jasmonate, trans-nerol tertiary alcohol, 2-nonone, and phenyl ethanol were identified as key aroma components in Huangdan oolong tea, which provided it with clean and high floral aroma and obvious milky aroma characteristics. In Tieguanyin oolong tea, linalool, 3,5-octylodiene-2-one, linalool oxide, cis-jasmonone, dehydrolinalool, and α-terpineol showed diverse floral aromas, which were closely related to the characteristic aroma of Tieguanyin oolong tea. The key aroma components identified in Jinguanyin oolong tea included linalool, canalaldehyde, geranyl acetone, cis-jasmonone and isoeugenol, which were responsible for the characteristic sweet floral and woody aromas of Jinguanyin oolong tea.
Chemical Constituents and Digestion-Promoting Effect of Maojian Green Tea
GAO Jianjian, ZHOU Zhengyang, SONG Yanhua, YU Shuai, LU Wei, LIN Zhi, DAI Weidong
2024, 45(1):  109-117.  doi:10.7506/spkx1002-6630-20230324-238
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In this study, the digestion-promoting function of an aqueous extract from Maojian green tea extract (MJ-GTE) was evaluated by small intestinal motility in mice as well as body mass, body mass gain, food intake, food utilization rate, gastric pepsin activity, and gastric pepsin excretion in rats. The chemical composition of MJ-GTE was then systematically analyzed using metabolomics based on ultra-high performance liquid chromatography-quadrupole electrostatic orbitrap mass spectrometry (UPLC-Q-Exactive/MS). The results of animal experiments showed that the intestinal propulsion ratio of ink in the high-dose MJ-GTE group (0.83 g/(kg·d)) was significantly increased compared with the model group (P < 0.05), and gastric pepsin excretion in the medium-dose MJ-GTE group (0.21 g/(kg·d)) was significantly increased compared with the negative control group (deionized water) (P < 0.05), which collectively indicated that MJ-GTE has a digestion-promoting effect. The metabolomics analysis identified 98 compounds, among which, flavones (apigenin and luteolin, 0.14–0.77 mg/g), flavanones (naringenin and eriodictyol, 0.49–1.49 mg/g), flavone-7-O-glycosides (0.57–9.07 mg/g), and flavanone-7-O-glycosides (4.49–38.98 mg/g) were the major components in MJ-GTE. This study will provide a theoretical basis for the promotion and development of Maojian green tea and related products in the future.
Widely Targeted Metabolomics Revealed the Dynamic Changes of Metabolites during the Formation of Goose Fatty Liver
MA Qiuxia, WANG Baowei, ZHANG Ming’ai, JIA Yiming, SUN Liqian, ZHANG Zihan, WANG Siyi, WANG Yue, FU Yingying, KONG Min, FAN Wenlei
2024, 45(1):  118-124.  doi:10.7506/spkx1002-6630-20230223-216
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To understand the composition and dynamic changes of metabolites during the formation of goose fatty liver, the metabolite profiles of goose liver at three overfeeding stages were analyzed using widely targeted metabolomics. Three 70-day-old Landes geese with similar body conditions from the same batch were selected randomly for slaughter at the early (day 7), middle (day 16) and late (day 25) overfeeding stages, separately. The tip of the larger liver lobe was collected for widely targeted metabolomic analysis. The results showed that: (1) a total of 1 153 metabolites belonging to 19 classes including amino acids, organic acids, nucleotides and lipids were detected in the liver of geese at the three overfeeding stages; (2) principal component analysis (PCA) showed significant differences in the metabolic profiles of goose liver at the three stages, and identified 142 and 92 differential metabolites at the early versus middle stage, and the middle versus late stage, respectively, the major ones being amino acids and their derivatives, as well as organic acids and their derivatives; and (3) Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathway analysis indicated that the pathways involved in fatty acid biosynthesis, vitamin B6 metabolism, linoleic acid metabolism, lysine degradation, arginine biosynthesis, arachidonic acid metabolism and amino acid biosynthesis changed significantly during the formation of goose fatty liver. This study found that most of the differential metabolites were involved in fatty acid synthesis during goose fatty liver formation. Moreover, the contents of transport-related metabolites showed a continuous increasing trend. Findings in this study will not only enrich the theoretical knowledge of poultry liver metabolism, but also provide a theoretical basis for the precise nutritional regulation and efficient production of high-quality goose fatty liver.
Widely Targeted Metabolomics Analysis of Compositional Differences between Purple Black Rice and Common Rice at Different Harvest Periods
TIAN Chengpiao, LONG Lingyun, LIU Gongde, YE Xueying, XIE Xiuping, TAN Xiaohui, WANG Liping
2024, 45(1):  125-132.  doi:10.7506/spkx1002-6630-20230315-147
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In this study, widely targeted metabolomics based on ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used to analyze the types and contents of differential metabolites between purple black rice and common rice produced in Guangxi and to illustrate the significantly differential metabolic pathways. A total of 667 metabolites were identified, including lipids, flavonoids, phenolic acids, alkaloids, and organic acids. Principal component analysis (PCA), cluster analysis and overall metabolite profiling showed that 239 of the 278 differential metabolites identified in mature rice samples were up-regulated, and 235 of the 267 differential metabolites identified in the 20 day earlier harvest group were up-regulated when compared with common rice. The metabolite composition of purple black rice at different harvest periods was similar, indicating that porridge made from purple black rice harvested in advance will have soft and glutinous texture as well as complete nutritional structure. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that significantly up-regulated compounds such as rhamnose-3-O-glucoside, hesperidin-7-O-glucoside, homoeriodictyol, eriodictyol, hesperidin, catechin, quercetin, naringin and chalcones in purple black rice were involved in the biosynthetic pathways of flavonoids and flavonols, regulating the contents of flavonoids and flavonols, and improving the nutritional quality and antioxidant effect of purple black rice.
Changes in Aroma Compounds and Selected Precursors of Sun-Dried Green Tea during Processing
YANG Yuansi, KUN Jirui, DAI Hongwei, TONG Huarong
2024, 45(1):  133-142.  doi:10.7506/spkx1002-6630-20230408-073
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In order to investigate the changes in the characteristic aroma components of sun-dried green tea during processing, the volatile substances in fresh, fixated, rolled and sun-dried leaves of Yunnan large leaf tea were determined using solvent flavor-assisted evaporation extraction (SAFE) combined with gas chromatography-mass spectrometry (GC-MS), and the aroma active components of sun-dried green tea were identified by odor activity value (OAV). The results showed that totally 67 volatile compounds were detected, the major ones being alcohols, esters and aldehydes, and the total amount of volatile substances increased from fresh leaves to the end of fixation. The total amount of volatile substances slightly decreased in sun-dried leaves compared to fresh leaves, but the number of volatile substances increased. A total of 23 aroma active compounds with OAV > 1 were found in sun-dried green tea, with the major ones being those contributing to floral and green aromas such as linalool, geraniol and nonanal. Aldehydes were the most prominent component in each processing stage. Using gas chromatography-flame ionization detector (GC-FID) and high performance liquid chromatography-photo-diode array (HPLC-PDA), a total of 7 fatty acids were detected, with saturated fatty acids being the major components; 13 carotenoids were detected, including lutein, whose content was the highest in all processing stages. During the processing of sun-dried green tea, the total amounts of fatty acids and carotenoids decreased continuously, especially linoleic acid and linolenic acid, and the content of hexanal as their major degradation product showed the opposite trend. The contents of terpene ketones, ionone and its oxidized derivatives such as β-ionone and 5,6-epoxy-β-ionone significantly increased as a result of the degradation and transformation of carotenoids. The trends of fatty acids and carotenoid precursors during the processing of sun-dried green tea were correlated with their associated aroma products. In conclusion, the results of this study may provide theoretical guidance for the targeted aroma improvement of sun-dried green tea.
Analysis of Sensory Characteristics and Aroma-Active Substances of Milk from Different Farms Using Check-All-That-Apply and Gas Chromatography-Mass Spectrometry-Olfactometry
HAN Haoying, WANG Yadong, HAN Zhaosheng, WANG Bei, FU Cuixia, ZHAO Shuang, QIAO Linya, YAO Huan
2024, 45(1):  143-149.  doi:10.7506/spkx1002-6630-20230228-252
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In this study, the check-all-that-apply (CATA) method, headspace solid phase microextraction (HS-SPME)-Arrow combined with gas chromatography-mass spectrometry (GC-MS) and gas chromatography-mass spectrometry-olfactometry (GC-MS-O) were used to analyze volatile flavor substances that affect the sensory differences among milk from four pastures. The results of the CATA questionnaire showed that milky aroma, creamy aroma, fragrant and sweet aroma, milky aroma, plastic odor, cooked odor and metallic odor were significantly different among the four milk samples (P < 0.05), and milk from pasture I were the most preferred by respondents, and the preference scores of milk from pastures III and IV were lower. Totally 14 aroma-active substances with an aroma intensity greater than or equal to 1 were obtained from the four milk samples through olfactometry. Using partial least squares regression analysis (PLSR), correlation analysis among sensory data, aroma-active substances and milk samples was conducted. The results showed that milky and creamy aroma from pasture I were prominent, which was strongly correlated with 2-heptanone, butanoic acid, decanoic acid, and hexanoic acid. Milk from pasture II showed a fragrant and sweet aroma, which may be related to the concentration of limonene. Milk from pasture III had prominent metallic, plastic, and milky odors, which may be related to 1-octene-3-alcohol. Milk from pasture IV had a cooked odor, which mainly came from hexanal and styrene.
Analysis of Terpenes and Cannabinoids in Hemp Oil by Gas Chromatography-Mass Spectrometry and Ultra-high Performance Liquid Chromatography
ZHANG Ruiting, CAI Youxi, ZHANG Hao, SUN Hui, SUN Xiaodong, TENG Yajun, LI Xiaolei
2024, 45(1):  150-157.  doi:10.7506/spkx1002-6630-20230530-275
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Gas chromatography-mass spectrometry (GC-MS) and ultra-high performance liquid chromatography (UPLC) were used to analyzed terpenes, fatty acids and cannabinoids in hemp oil, and the obtained data were analyzed by means of principal component analysis (PCA). The results showed that hemp oil produced in Yunnan contained rich characteristic flavor terpenes including β-caryophyllene, β-myrcene, and limonene. Also, it was rich in fatty acids; particularly the ratio of linolenic acid and linoleic acid was close to the golden ratio, indicating high nutritional value. Trace amounts of multiple cannabinoids were detected in hemp oil irrespective of cultivar or processing method. The content of cannabinoids in hemp oil was significantly reduced by dehulling, and cold pressing was more suitable for hemp oil processing. Moreover, this study discussed the safety of hemp oil for consumption in China and put forward some suggestions. Finally, four hemp oil samples were perfectly distinguished and identified by PCA.
Changes of Metal Element Contents in Base Liquor for Maotai-Flavor Baijiu during Storage and Their Effects on Flavor Compounds
FAN Chenming, HUI Ming, TIAN Qing, YOU Yongsong
2024, 45(1):  158-165.  doi:10.7506/spkx1002-6630-20230224-224
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Inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the contents of 25 metal elements in base liquor of different ages for Maotai-flavor Baijiu from three companies. A discriminant model was constructed using chemometrics to identify key differential metal elements. The results showed that the contents of metal elements in base liquor were positively correlated with age for each brand. Principal component analysis (PCA), hierarchical cluster analysis (HCA) and partial least squares discriminant analysis (PLS-DA) could effectively distinguish among six age groups; among them, PLS-DA had the best degree of discrimination, and the results of the PLS-DA model were consistent with those of the PCA model. Five key differential metal elements, namely Al, Ca, K, Na and Fe, were determined in the base liquor stored for 0–10 years by PLS-DA and one-way analysis of variance (ANOVA). The differential metal elements were found to play a positive role in the storage of base liquor through gas chromatography triple quadrupole mass spectrometry (GC-TQ-MS) detection. The discriminant model could discriminate base liquor of different ages from other companies. In summary, ICP-MS combined with chemometric analysis can effectively classify and identify base liquor of different ages for Maotai-flavor Baijiu, and determine the changes of metal element contents in base liquor for Maotai-flavor Baijiu during storage more accurately and efficiently.
Composition and Functions of Highland Barley Bran with Different Milling Rates
ZHANG Xin, ZHOU Wenju, DU Yan, TU Zhaoxin, LIANG Feng, MA Guilian, LI Juan
2024, 45(1):  166-172.  doi:10.7506/spkx1002-6630-20221226-250
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For a better understanding of the difference in functional components and functions among different parts of highland barley bran, the contents of protein, β-glucan and polyphenol, antioxidant activity, and alkyl radical intensity in highland barley bran with various milling rates were compared. The results showed that the contents of total protein, albumin, globulin, glutenin, free polyphenol, bound polyphenol, free flavone, bound flavone and condensed tannin first increased and then decreased with increasing milling rate. Protein mainly existed in bran flour with a milling rate of 17.74% and 19.22%. Bran flour with 9.7% milling rate had the highest phenol content, and the trend in antioxidant activity was consistent with that in the content of phenols. The contents of β-glucan and gliadin increased from outside to inside, and reached the highest value at a milling rate of 25.99%. Alkyl radical intensity was significantly higher at 1.54%–5.84% milling rates than at 7.67%–25.99% milling rates, indicating a higher susceptibility to oxidation. The findings of this study provide a theoretical basis for the deep processing of different layers of highland barley bran.
Food Engineering
Preparation of Chitosan Microflower and Factors Affecting Its Morphology
JIAO Siyu, XU Dingyu, YAO Xianchao, HE Lixin, LIN Rihui
2024, 45(1):  173-180.  doi:10.7506/spkx1002-6630-20230316-163
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Chitosan (CS) was dissolved with the aid of ultrasound and hydrogen peroxide treatment. Then, sodium tripolyphosphate (TPP) was introduced as a crosslinker into CS solution from bottom to top. Finally, chitosan microflower (CSMF) was obtained by collecting the resulting precipitate and freeze-drying it. CSMF was characterized and the factors affecting its formation were studied. The results showed that the size of CSMF was 1–2 μm in diameter. The Fourier transform infrared (FTIR) spectrum of CSMF showed a vibration peak of phosphate group at 532 cm-1. The crystal form of CS changed from semi-crystalline structure to hydrated polycrystalline structure after conversion into CSMF. X-ray photoelectron spectroscopy (XPS) showed that CSMF produced C-N+ bond, and thermogravimetric analysis (TGA) showed that the thermal stability of CSMF was slightly lower than that of CS. Also, it was found that pretreatment method, ultrasonic time, CS solution temperature and CS/TPP ratio (m/m) but not ultrasound power or hydrogen peroxide addition could affect the flower-shaped structure of CSMF. Furthermore, it was inferred that the formation mechanism of CSMF was related to that fact that after the degradation of CS into short- or long-chain CS within a certain molecular mass range, relatively longer and shorter degraded CS chains were crosslinked by TPP to respectively form the pedestal of the microflower structure and nanosheets which were self-assembled on the substate through the interaction between the –NH3+ and phosphate ions in the structure of CS.
Preparation and Physicochemical Properties of Microcapsules Loaded with Selenium-Enriched Peptides and VE
CAI Jie, FANG Yuan, JIA Jilai, ZHANG Die, CONG Xin, CHENG Shuiyuan
2024, 45(1):  181-190.  doi:10.7506/spkx1002-6630-20230308-079
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A microcapsule system for the co-encapsulation of selenium-enriched peptides, being hydrophilic, and vitamin E (VE), being lipophilic, was developed using a combination of emulsification and freeze-drying. The effects of wall material concentration, selenium-enriched peptide content, and VE content on the encapsulation efficiency was investigated by single-factor experiments. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) showed that the selenium-enriched peptides and VE were effectively encapsulated in the microcapsules, and the microcapsules possessed good water dispersibility and maintained its double emulsion structure after reconstitution. The results of thermal stability analysis and 2,2’-azinobis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) cation radical scavenging assay confirmed that compared with selenium-enriched peptides, the microcapsules had higher thermal stability and antioxidant activity. Furthermore, electronic nose analysis showed that the microcapsule system possessed a good masking effect on the odor of selenium-enriched peptides. In vitro simulated digestion experiments showed that microencapsulation enhanced the stability of selenium-enriched peptides in simulated gastric juice and lowered the retention rate in simulated intestinal fluid; selenium-enriched peptides were effectively released from the microcapsules. This study will provide a theoretical basis for the development of selenium-enriched functional foods and nutritional supplements.
Safety Detection
Aptamer-Functionalized Magnetic Bead-Based Fluorescence Sensor for the Detection of Cronobacter sakazakii in Milk Powder Using Hybridization Chain Reaction Amplification
WANG Rui’an, DU Zaihui, KANG Shuaishuai, TIAN Hongtao, LI Chen, WANG Xinxin, WANG Miaoshu, XU Wentao
2024, 45(1):  191-197.  doi:10.7506/spkx1002-6630-20230310-100
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In this study, an aptamer-functionalized magnetic bead-based fluorescence sensor for the detection of Cronobacter sakazakii in milk powder using hybridization chain reaction (HCR) amplification was constructed. First, the sequence HP, combining a trigger sequence and an aptamer sequence which complement each other to form a stable secondary structure, and the hairpin sequences H1 and H2 were cleverly designed. Then, aptamer-functionalized magnetic beads were prepared by pentanediol reaction and avidin-biotin reaction. C. sakazakii was incubated with the aptamer magnetic beads. The aptamer sequence in HP recognized the target, causing conformational change of HP to expose its trigger sequence. The chain assembly of H1 and H2 was triggered by HCR to produce long double-stranded DNA, and the fluorescent dye SYBR Green I (SG) bound to the long double strands of HCR products by intercalation and slot binding. Finally, graphene oxide (GO) was added to adsorb free H1, H2 and SG on its surface via π-π stacking, so the fluorescence signal was quenched. However, the HCR products could not be adsorbed on the surface of GO, so SG binding to the HCR product emitted a strong fluorescence signal dependent on the target concentration, thus allowing quantitative detection of C. sakazakii. The detection limit of this method was 2 CFU/mL for pure culture and 8 CFU/g for milk powder. It gave results for milk powder samples in good agreement with those obtained by the traditional microbial culture method. This method has the advantages of no requirement for DNA extraction, fast operation, high stability, specificity and sensitivity, so it provides a potential method for the on-site rapid detection of C. sakazakii.
Identification of Perilla Based on Three-Dimensional Fluorescence Spectra Using Wavelet Packet Decomposition, Fisher Discriminant Analysis and Support Vector Machine
REN Yongjie, YIN Yong, YU Huichun, YUAN Yunxia
2024, 45(1):  198-203.  doi:10.7506/spkx1002-6630-20230518-174
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In order to rapidly identify perilla species and avoid passing off, three-dimensional (3D) fluorescence spectral data of perilla from four regions in China were acquired. A feature selection strategy of fluorescence data based on wavelet packet decomposition fused with Fisher discriminant analysis (FDA) was proposed, and effective identification of the four species of perilla was implemented. First, the 3D fluorescence data were preprocessed by using Delaunay triangle interpolation to remove the adverse influence of Rayleigh scattering and Raman scattering; Savitzky-Golar (SG) convolutional smoothing was applied to smooth the data for the purpose of reducing the interference of noise. At the same time, the 3D fluorescence data were initially screened to remove emission wavelengths with fluorescence intensity less than 0.01. Second, the 3-layer sym4 wavelet packet decomposition of the emission spectrum corresponding to each excitation wavelength was performed, and the wavelet packet energy value of the lowest frequency band was calculated as the amount of spectral data characterization for each excitation wavelength. Third, FDA was used for discriminant analysis of these wavelet packet energy values, and the discrepancy information contained in them was fused to obtain the new variables generated by FDA; the first three FD variables with 99% cumulative discriminative power were selected as variables for the characterization of the discrepancy information of different species, and then a characterization strategy for the 3D fluorescence data was proposed. Finally, two pattern recognition algorithms, back propagation neural network (BPNN) and support vector machine (SVM), were used to analyze the characterization variables, and identification results were obtained with FDA + BPNN and FDA + SVM. A correct rate of 97.5% for the training set and 95% for the test set was observed with FDA + BPNN, and the correct rate obtained with FDA + SVM for both the training and test sets was 98.33%. These results showed that 3D fluorescence spectroscopy combined with wavelet packet decomposition, FDA and SVM algorithms could basically identify perilla from different regions, which will provide a basis for further research on perilla, such as quantitative detection of some active components.
Quantitation and Dietary Risk Assessment of Hexazinone Residue in Blueberry Fruit
HE Hongmei, XU Lingying, ZHANG Changpeng, WANG Xiangyun, JIANG Jinhua, LI Yanjie, ZHAO Xueping
2024, 45(1):  204-209.  doi:10.7506/spkx1002-6630-20230209-093
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In order to determine the residue of hexazinone in blueberry fruit, field experiments in Zhejiang, Jilin, Liaoning and Beijing, China were conducted using 75% hexazinone water dispersible granules. An analytical method was established for determining residual hexazinone in blueberry fruit utilizing ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) with an electrospray ionization source in the positive ion mode (ESI+). The samples were extracted with acetonitrile while vortexing, salted out, and then purified on a column packed with primary secondary amine (PSA) and C18 before measurement. The linearity, matrix effect, limit of quantification (LOQ), trueness (recovery rate) and precision (relative standard deviation (RSD)) of the proposed method were studied. Good linearity (r > 0.999 8) was found in the concentration range from 0.000 1 to 0.01 mg/L. The matrix effect was −7.7%. The LOQ was 0.01 mg/kg. The average recovery of hexazinone from blueberry fruit at spiked concentration levels of 0.01, 0.1 and 1.0 mg/kg ranged from 87% to 91%, with a RSD less than 3.7%. The field experiments showed that the residual level of hexazinone in blueberry fruit was below 0.01 mg/kg at 90 and 100 days after application, which was lower than the maximum residue limits (MRL) established in the US, Japan and South Korea (0.6, 0.2 and 0.05 mg/kg, respectively). The results of chronic dietary risk assessment showed that the estimated daily intake of hexazinone for general populations was 0.002 2 mg. The dietary risk quotient (RQ) was only 0.084%, indicating a low risk of dietary hexazinone intake. Therefore, it is recommended that 75% hexazinone water dispersible granules (WG) be applied in a single dose up to 1 800 g/hm2 to blueberry orchards; the pre-harvest interval (PHI) be 90 days.
Establishment of a Multiplex Real-Time PCR Method for Detection of Four Plant-Derived Components and Its Application to Edible Starches
FAN Wei, GAO Xiaoyue, DONG Yuxin, LIU Hongyu, LI Henan, ZHAO Wentao, GUO Wenping
2024, 45(1):  210-216.  doi:10.7506/spkx1002-6630-20230315-149
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A multiplex real-time polymerase chain reaction (PCR) method for simultaneous and rapid detection of components derived from sweet potato, cassava, potato, and corn was established. The g3pdhs gene of sweet potato and cassava, the UGPase gene of potato and the zSSIIb gene of corn were used as target genes to design specific primers and TaqMan probe, and the 18S rRNA gene was used as the internal reference gene. Methodological validation was performed, and the proposed method was applied to simulated samples with different mixing ratios and actual starch samples. The results showed that this method was high-throughput, sensitive and specific. No cross-reaction was found with 15 non-target sources. The detection sensitivity for template DNA was 3 × 10-3 ng/μL, and the proposed method had a good linear relationship and high amplification efficiency. The detection limit for edible starch samples was 0.1%. The results of the PCR method for 50 actual samples were consistent with those of the reference method, indicating that this method could be used for the detection of common adulterants in edible starches.
Development of ISO Standard for Real-Time Polymerase Chain Reaction Detection of Turkey-Derived Material
PAN Liangwen, NING Xue, WANG Qiang, CAI Yicun, XU Zhenjian, ZHANG Chen
2024, 45(1):  217-224.  doi:10.7506/spkx1002-6630-20230407-067
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In this study, the specific fragment of turkey chromosome Z-DNA sequence was selected as the target sequence for turkey-derived material detection. A real-time polymerase chain reaction (real-time PCR) method was established, which had good interspecies specificity and interspecies consistency. The target sequence was cloned into the plasmid pUC57, and after being diluted to different concentrations, the plasmid was tested by real-time PCR. The absolute detection limit of this method was 5 copies/PCR reaction. An international collaborative validation trial was conducted to validate this method. The results showed that the false positive and negative rates of the proposed method were both 0%, and the absolute detection limit was 5 copies/PCR reaction. The results of qualitative analysis of the diluted plasmid showed that the inter-laboratory standard deviation was 0.30, less than the maximum permitted value of 1; at a detection probability of 95%, the absolute detection limit was 3.2 copies/PCR reaction, less than the maximum allowable value of 20 copies/PCR reaction. Based on voting results and reviewers’ comments, this method was approved by the International Organization for Standardization (ISO) as an international standard method (ISO/TS 20224-8:2022).
Rapid Determination of Nine Acrylates in Food Contact Materials by Ultra Performance Convergence Chromatography
QIU Yue, TAN Chaolan, LIU Xiaoyu, LU Jiali, YU Qiuling
2024, 45(1):  225-231.  doi:10.7506/spkx1002-6630-20230328-276
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Ultra performance convergence chromatography (UPC2) was used to establish a rapid analytical method to determine nine acrylate compounds in plastic food contact materials simultaneously. The samples were extracted with methanol, filtered through an organic membrane, and separated on an ACQUITY UPC2 HSS C18 SB column with gradient elution using a mobile phase consisting of supercritical carbon dioxide and acetonitrile. The photodiode array (PDA) detector was set at 210 nm. Experimental results showed that under the optimal conditions (column temperature, 40 ℃; and back pressure, 13.79 MPa), qualitative and quantitative analysis of the nine acrylates was completed within 4 min. Linear ranges were 0.2–100 mg/L for phenyl methacrylate (PNMA), benzyl methacrylate (BZMA) and ethylene dimethacrylate (EDMA); 0.3–100 mg/L for methacrylic acid (MAA); 0.4–100 mg/L for butyl acrylate (BTA), hydroxyethyl methylacrylate (HEMA) and hydroxyethyl acrylate (HEA); and 0.5–100 mg/L for isobutylmeth acrylate (IBMA) and benzyl acrylate (BZA). The determination coefficients (R2) of the standard curves for all acrylates were higher than 0.998 5, and recoveries obtained at high (30 mg/kg), middle (6 mg/kg) and low (0.2, 0.3, 0.4 and 0.5 mg/kg) spiked concentrations ranged from 89.3% to 109.7%, with relative standard deviations of 0.62% to 3.86% (n = 6). The limits of detection (RSN ≥ 3) were 0.05–0.15 mg/kg, and the limits of quantification (RSN ≥ 10) were 0.2–0.5 mg/kg. The proposed method identified the risk of acrylate residues in 30 batches of actual samples.
Fast Detection of the Emetic Toxin Cereulide in Cooked Rice and Dairy Products by Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry
ZENG Xi, WANG Yu, XU Jucai, HUANG Suidong, WANG Juan, XU Zhenlin
2024, 45(1):  232-238.  doi:10.7506/spkx1002-6630-20230207-064
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A matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) method was developed for the rapid detection of the emetic toxin cereulide in cooked rice and dairy products. The splitting pattern of cereulide standard was analyzed, meanwhile, effects of matrix type, spotting methods, the type and dosage of matrix solvent, and laser intensity on the MS signal intensity of cereulide were investigated. Methodological validation and application to actual samples were conducted. As a result, α-cyano-4-hydroxycinnamic acid (HCCA) was chosen as the matrix and dispersed in a 1:1 acetonitrile-water mixture containing 0.1% trifluoroacetic acid, and the matrix and the samples were sequentially spotted. In MALDI-TOF MS screening of foods using positive ion reflectron and linear modes at 70% laser intensity, the target ion peaks of ([M + Na]+ and [M + K]+) in cereulide were detected with stable signals, high intensity and good response repeatability. The results of methodological validation showed that good linear relationship was observed between the overlapping areas of [M + Na]+ and [M + K]+ peaks and cereulide concentration in the range from 5 to 100 ng/mL, with a correlation coefficients (r) greater than 0.99. The limits of detection (LOD) of [M + Na]+ and [M + K]+ were 3.0 and 5.0 ng/g, respectively; the recoveries of spiked rice and milk samples were ranged from 73.3% to 118.2%, with relative standard deviations (RSDs) of 0.3% to 10.9% (n = 6). This method was characterized by rapidity, high accuracy, good sensitivity, and strong anti-interference ability, and was suitable for the detection of cereulide in cooked rice and dairy products without using any internal standard.
An Intelligent Gel Label for Non-destructive Monitoring of the Freshness of Fresh-Cut Netted Melon
RONG Liyan, JIANG Donghua, LI Li, WANG Yanqun, ZHANG Shuang, MA Yichao, YANG Shuhan, LI Yuexin, WU Zhaoxia
2024, 45(1):  239-246.  doi:10.7506/spkx1002-6630-20230328-270
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In this study, a novel intelligent gel label for the real-time monitoring of the freshness of fresh-cut netted melon was fabricated using carrageenan, sodium carboxymethylcellulose and xanthan gum as the matrix materials and bromothymol blue (BTB) as the chromogenic indicator. The color of the gel label changed from blue to yellow-green, yellow-brown and orange-yellow according to the CO2 concentration inside the package, which could reflect the freshness of fresh-cut netted melon. The morphology and structure of the gel label were characterized using scanning electron microscopy (SEM), attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray diffraction (XRD) and thermogravimetry (TG). The results showed the microstructure of the gel labels did not change with the addition of sodium carboxymethylcellulose and xanthan gum, which indicated the three components were well compatible, while the thermal stability of the gel label was improved with the addition of BTB. The gel label showed excellent color stability during storage at 4 or 25 ℃ and its color changed obviously with the storage of fresh-cut netted melon at 4 ℃. The correlation analysis showed a significant correlation between the label’s color difference and the CO2 concentration in the package as well as the pH and total aerobic plate counts of fresh-cut netted melon. This gel label had excellent pH sensitivity and thus could be used as an effective method for monitoring the freshness of fresh-cut netted melon.
Detection of Pine Nut Allergen in Three Kinds of Food by Ultra-high Performance Liquid Chromatography-Tandem Mass Spectrometry
NING Yawei, ZHOU Hongxin, YANG Zheng, MA Junmei, LIU Zhuo, ZHANG Yan, LI Qiang
2024, 45(1):  247-253.  doi:10.7506/spkx1002-6630-20230118-140
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An ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was established for the detection of pine nut allergen Pin k 2 in food matrices. Pine nuts were ground, degreased, and enzymatically extracted and the hydrolysate was separated and analyzed by using an Easy-nLC 1000-QExecutive high-resolution mass spectrometer, and the mass spectral data obtained were processed using Protein Pilot TM software and the Uniprot protein database. The specificity was verified by Basic Local Alignment Search Tool (BLAST), and three pine nut-specific peptides were selected finally. The developed method exhibited a good linear relationship in the concentration range of 0.001–50 mg/mL, and the limit of quantification was 1 mg/kg. The average recoveries for blank biscuit, chocolate and beverage were 88.50%–107.57%, with a relative standard deviation (RSD) not exceeding 6.08%, and the matrix effect was 89.77%–96.13%. This method has the advantages of high sensitivity and good specificity, and can be applied to the detection of pine nut allergens in food samples such as biscuits, chocolate, and beverages, which provides technical support for the authentication of food labels and the detection of latent allergens in foods.
Identification of Honey Adulterated with Syrup by Raman Spectroscopy and Chemometrics
KOU Zekun, CHEN Guotong, LI Siyu, YANG Zhong, OUYANG Lingxiu, GONG Yan
2024, 45(1):  254-260.  doi:10.7506/spkx1002-6630-20230323-230
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In order to qualitatively and quantitatively identify syrup adulteration in honey, a method for rapid identification of adulterated honey by Raman spectroscopy and chemometrics was proposed. Raman spectroscopy was used to acquire spectral data of honey samples, and principal component analysis (PCA) was used to extract features from the spectral data. Principal components with a cumulative contribution rate of more than 85% were selected for modeling and prediction. By using linear discriminant analysis (LDA) and partial least squares-discriminant analysis (PLS-DA), models to identify honey adulterated with 20% syrup were established. A support vector machine (SVM) model to identify honey adulterated with 5% syrup, and all LDA, PLS-DA and SVM models could distinguish adulterated honey samples with 1% syrup content from pure honey with an accuracy of more than 0.9. Raman spectroscopy combined with chemometrics is a fast and non-destructive method for the identification of adulterated honey with high accuracy, which is significant to maintaining the order of the honey market.
Reviews
A Review of the Antibacterial Activity of Chitosan and Its Application in Antibacterial Packaging
LIU Mengqi, LÜ Rui, CHEN Ju, JIAO Ruiwen, MI Chunxiao, LI Xiang, REN Dandan, WU Long, WANG Qiukuan, ZHOU Hui
2024, 45(1):  261-271.  doi:10.7506/spkx1002-6630-20230119-146
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Chitosan can be used as an active antibacterial agent or film-forming substrate in foods, and has become a powerful substitute for synthetic plastic polymers because of its good biodegradability, film-forming capacity and antibacterial activity. However, chitosan films have several limitations such as poor water solubility and weak mechanical properties, which limit its application in antibacterial food packaging materials to a certain degree. The safety of applying the antibacterial activity of chitosan in foods has attracted much attention in recent years. In order to provide new ideas for further development and utilization of chitosan-based antibacterial composite materials, this paper expounds the antibacterial mechanism of chitosan and the methods to improve its antibacterial performance, and summarizes the current status of the application of chitosan-polysaccharide, protein or lipid composite films in food preservation.
Advances in Microbial Diversity and Interactions in Kefir
LI Shiwei, BAI Ying
2024, 45(1):  272-280.  doi:10.7506/spkx1002-6630-20230111-090
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Kefir is a fermented dairy beverage produced by using natural microbiota which mainly contains specific microbial communities such as lactic acid bacteria, yeast and acetic acid bacteria, and it has good flavor and health beneficial functions. However, the formation mechanism of kefir grains is not clear at present, and it is generally believed that the formation of kefir grains is based on bacterial biofilm as the precursor. This paper reviews the microbial diversity of kefir from different regions and the effects of microorganisms in kefir grains on the function and flavor of fermented milk, as well as the microbial interactions and succession during kefir fermentation. The role of biofilm formation in kefir grain formation is also described in order to provide some references for future research on the formation mechanism of kefir grains.
A Review of Factors Influencing the Preparation of Bigels and Its Application in Food Field
CHENG Chuansen, LIU Yanqing, BIAN Miaomiao, LIU Jun, TU Yixian, JING Siqun
2024, 45(1):  281-288.  doi:10.7506/spkx1002-6630-20230730-330
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Bigels are a new type of biphase system produced by the combination of hydrogel and organogel (oleogel), which have the characteristics of both aqueous and organic phases. Bigels exhibit superior performance to single-component gels, with the advantages of being able to deliver both hydrophilic and hydrophobic substances, ease of preparation, excellent spread ability, good physical stability, and long shelf life. In recent years, bigels have been of wide concern, and more and more studies have shown that bigels have a wide application prospect in the field of foods. This paper briefly reviews the structure of bigels, the effects of several major factors in the preparation of bigels such as the type and concentration of gelling agent, oleogel/hydrogel ratio and homogenization conditions on the physicochemical properties of bigels. It also explores the application of bigels in bioactive compound delivery, 3D food printing, fat substitution, and other aspects in the field of food industry. This review will contribute to further research and application of bigels in the food industry.
Progress on Research and Application of New Non-destructive Testing Techniques in Tomato Quality Inspection
HAN Zixin, ZHANG Lili, ZHANG Bo, ZOU Fanglei, SHANG Nan
2024, 45(1):  289-300.  doi:10.7506/spkx1002-6630-20230103-014
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Tomatoes are one of the most widely cultivated vegetables in China and are popular among consumers. In recent years, as the demand for healthy food has grown, the quality of tomatoes has aroused increasing attention. While tomatoes are generally uniform in shape, there are significant differences in size, fruit type and color among tomato varieties, and tomatoes contain a variety of nutrients with complex chemical structures, so its quality is difficult to assess. The traditional tomato quality testing methods are subjective, destructive, time-consuming and laborious, and thus cannot meet the demand of large-scale quality testing. Recently, with the development of non-destructive testing technologies, new detection methods such as machine learning, multispectral techniques, and electronic nose/electronic tongue have been developed and applied for the rapid and non-destructive testing of tomato quality. This paper provides a summary of the development and application of artificial intelligence based on image recognition, electronic nose technology and spectroscopic technologies for the non-destructive testing of tomatoes in order to provide a reference for future research and development of tomato quality inspection.
Food-Derived Natural Products Prevent Neurodegenerative Diseases by Regulating Mitophagy: A Review of Research Progress
CAO Yuxin, ZHANG Yanqing, QI Wuqin, XIE Junbo
2024, 45(1):  301-312.  doi:10.7506/spkx1002-6630-20230113-104
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Neurodegenerative diseases are often characterized by progressive dysfunction and loss of neuronal structure and function, including Alzheimer’s disease, Parkinson’s disease, Huntington’s disease. Mitochondria, the center of energy metabolism in the body, are often damaged and accumulated in neurodegenerative diseases. As an efficient way of removing these damaged mitochondria, mitophagy usually shows an abnormal state in the development of these diseases, which aggravates the cognitive and motor dysfunction of the body, and finally speeds up the process of related diseases. In recent years, it has been found that food-derived natural products, such as quercetin, curcumin, resveratrol and silymarin, play significant roles in regulating mitophagy to improve neurodegenerative diseases, which have unique advantages, such as lower toxicity than chemical synthetic drugs and cost-effectiveness. Here, we summarize recent studies on the regulation of mitophagy by food-derived natural products to slow down neurodegenerative disorders in order to provide new ideas for researchers to develop and utilize food-derived natural products.
Research Progress on Preparation and Functions of Alginate Oligosaccharides with Different Structures
HUANG Youtao, LIANG Qingping, GAO Xiaoya, LI Dongyu, MOU Haijin
2024, 45(1):  313-325.  doi:10.7506/spkx1002-6630-20230112-096
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Alginate is one of the most abundant marine polysaccharides, which can be degraded into alginate oligosaccharides (AOS) by chemical, physical and biological methods. AOS, linear oligosaccharide composed of guluronic acid and mannuronic acid, have a variety of biological activities such as antimicrobial, anti-inflammatory, and immunoregulatory activities, and these biological activities are closely related to their structural diversity. AOS prepared by different degradation methods have different uronic acid compositions, polymerization degrees and special structures. Therefore, exploring the structure-function relationship of AOS will help to fully understand the activity of AOS and improve its application value. In this paper, the reaction mechanisms of the various methods to prepare AOS, the structures of the resulting products, and the structure-function relationship of AOS are reviewed in order to provide a reference for further research and application of AOS.
Progress on Research and Application of Postbiotics
LIU Hongxia, LI Xueli, WU Xiuying, Feng Xudong, Guo Yanrong, Jiang Yunyun, Lai Mengxuan, Ma Hairan
2024, 45(1):  326-333.  doi:10.7506/spkx1002-6630-20221229-272
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Postbiotics are a preparation of inanimate microorganisms and/or their components are beneficial to the health of the host, with multiple advantages such as safety, stability, easy storage and production, and clear chemical structure. This article reviews the major bioactive ingredients, probiotic functions and current application status of postbiotics; elaborates the health benefits of inactivated bacterial cells, bacterial components and bacterial metabolites to the host; summarizes recent progress in understanding the health benefits of postbiotics such as enhancing immunity, regulating gastrointestinal function, alleviating obesity, maintaining oral health, and preventing osteoporosis; outlines commercially available postbiotic products in Japan, the United States, Germany and China; and proposes the challenges and new research directions of postbiotics.