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15 November 2021, Volume 42 Issue 21
Invited Papers
Progress in Research on the Effect of Natural Antioxidants on the Antioxidant Capacity and Quality of Surimi and Surimi Products
LI Jianrong, WANG Zhongqiang, YI Shumin, LI Xuepeng, XU Yongxia, ZHOU Xiaomin, WANG Mingli
2021, 42(21):  1-7.  doi:10.7506/spkx1002-6630-20210806-088
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Surimi and surimi products are rich in polyunsaturated fatty acids and protein, and hence, highly prone to lipid oxidation and protein oxidation during storage and transportation, which reduces their flavor, quality and gel properties. Antioxidants can effectively inhibit the oxidation of lipids and proteins in surimi and surimi products. Natural antioxidants are safer and more effective than synthetic ones. Therefore, the addition of natural antioxidants to surimi and surimi products is considered a safer and acceptable means of anti-oxidation, since it can effectively inhibit protein degradation, lipid oxidation, fishy odor and microbial spoilage thereby effectively improving their quality, flavor and gel properties. This paper reviews the types, sources and action mechanism of natural antioxidants and their effects on surimi and surimi products, which will hopefully provide a reference for the application of natural antioxidants in surimi products.
Basic Research
Effects of Tea Polyphenols on Physicochemical Properties of Wheat Starch and Bread Quality and Their Action Mechanism
CHEN Nan, CHEN Long, HE Qiang, SUN Qun, ZENG Weicai
2021, 42(21):  8-16.  doi:10.7506/spkx1002-6630-20200622-296
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Purpose: To investigate the effects of tea polyphenols (TP) on the physicochemical properties of wheat starch and bread quality and their action mechanism. Methods: The impact of TP on the transmittance, gelatinization, retrogradation and gel microstructure of starch was determined together with their influence on the specific volume, texture and color of bread. Furthermore, the interaction mechanism between starch and the major components of TP was observed by molecular dynamics simulation. Results: TP reduced the transmittance of starch paste, promoted the gelatinization of starch, inhibited the retrogradation of starch, and changed the three-dimensional network structure of starch gels. Meanwhile, addition of different amounts of TP had a significant effect on the specific volume, texture and color of bread. TP could change the spatial configuration of starch by affecting the formation of intramolecular and intermolecular hydrogen bonds. Among the phenolic compounds, epigallocatechin gallate bound more stably to starch molecules with a higher proportion of hydrogen bonds and a lower binding free energy. Conclusion: TP show the potential to improve the physicochemical characteristics of wheat starch and bread quality.
Effect of Exercise on Lipid Metabolism and Meat Quality of Sunit Sheep
HUANG Huan, GUO Yueying, ZHANG Min, ZHANG Yue, YAO Duo, SU Lin, SA Rentuya, LIU Peiqing, JIN Ye
2021, 42(21):  17-23.  doi:10.7506/spkx1002-6630-20201124-246
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In order to explore the effect of exercise on the lipid metabolism and meat quality of Sunit sheep, a total of 12 (3-month-old) Sunit sheep with good body condition and body mass of (20.22 ± 0.68) kg were selected and randomly divided into a control group and an exercise group. The animals in the control group were housed in semi-open pens, while those in the exercise group were subjected to exercise by driving about 6 kilometers every day under the same housing environment. The pre-experiment lasted for 7 days and the formal experiment lasted for 90 days. The body mass was measured before slaughter, and Longissimus dorsi muscle was harvested after slaughter for determining meat quality attributes, fatty acid composition and the expression of genes associated with lipid metabolism by gas chromatography-mass spectrometry (GC-MS), and real-time fluorescent quantitative polymerase chain reaction (PCR). The results showed that the slaughter performance (live body mass and back fat thickness) and meat quality (intramuscular fat content, pH, and the color parameters L*, a* and b* values) of the exercise group were significantly lower than those of the control group (P < 0.05) and the meat tenderness was worse than that of the control group. The relative content of saturated fatty acids in lamb meat from the exercise group was slightly lower than that in the control group, while the relative content of n-3 unsaturated fatty acids was significantly lower than that in the control group (P < 0.05). Compared with the control group, the relative expression levels of the hormone-sensitive triglyceride lipase (HSL), fatty acid synthetase (FASN), zinc finger protein PRDM16 (positive regulatory domain containing 16, PRDM16), and uncoupling protein1 (UCP-1) genes in the exercise group were significantly up-regulated (P < 0.05). In general, exercise for 90 days can improve the lipid metabolism of Sunit sheep, but decrease the meat quality.
Effects of Heating Methods on the Structure and Physicochemical Properties of Silver Carp Myosin
LIANG Wenwen, YANG Tian, GUO Jian, WANG Qiukuan, CONG Haihua, CHEN Shengjun
2021, 42(21):  24-31.  doi:10.7506/spkx1002-6630-20201012-086
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This study compared the effect of different heating methods: traditional two-stage water bath heating (40 ℃/30 min + 90 ℃/20 min), and six three-stage heating processes, namely, microwave heating (MH) followed by two-stage water bath heating, microwave-assisted water bath heating (MWH) followed by two-stage water bath heating, water bath heating (WH) followed by two-stage water bath heating, and incorporation of MH, MWH or another WH between the two stages of WH on the structure and physicochemical properties (total sulfhydryl group content, surface hydrophobicity, turbidity, solubility, secondary structure, tertiary structure and thermal stability) of myosin extracted from silver carp. The results showed that the heating time taken by MH and MWH was shortened obviously compared to that taken by WH, indicating an improvement in the heating efficiency. MWH followed by two-stage water bath heating promoted the unfolding of myosin, WH and incorporation of MH between the two stages of WH led to a high denaturation degree of myosin. Both the secondary and tertiary structures were sensitive to MH, leading to the exposure of more amino acid residues. MWH accelerated the heating rate while avoiding excessively high heating rate. Incorporation of MH or MWH before the first-stage WH facilitated the gelation of myosin, and incorporation of WH between the two WH stages promoted myosin aggregation.
Thermal Unfolding and Aggregation Process of Recombinant Staphylococcal Enterotoxin M (rSEM) Associated with Potential Toxin Responsible for Staphylococcal Food Poisoning
LIU Ji, TIAN Wanfan, TANG Junni, CHEN Juan, ZHAO Yanying, YU Jicheng
2021, 42(21):  32-45.  doi:10.7506/spkx1002-6630-20201006-011
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Thermal processing is one of the most useful tools to reduce the amounts of bacteria and toxins that may potentially be present in processed foods. Staphylococcal enterotoxin M is a newly identified group V superantigen with mild emetic activity and has the potential risk of causing staphylococcal food poisoning. In this study, the heat-induced conformational changes of recombinant staphylococcal enterotoxin M (rSEM) were identified by circular dichroism (CD), fluorescence spectroscopy and sodium dodecyl sulfate/native-polyacrylamide gel electrophoresis (SDS/native-PAGE). Below 40 ℃, rSEM had a well-folded structure with high contents of α-helix (17%), β-sheet (32%) and β-turn (21%) and the single tryptophan residue at position 121 (Trp121) on its molecular surface was found be located in the hydrophobic environment of the β-grasp domain. As the heating temperature increased from 42 to 55 ℃, α-helix content decreased, and β-sheet/turn contents increased to compensate for this. The aggregation state of the protein did not change markedly, while a distinct blue shift in the fluorescence emission maxima was observed accompanied by the reverse S-shaped curve for the ratio of fluorescence intensities at 350 and 340 nm, indicating the formation of an alternatively folded state, namely the intermediate state (IS). When the temperature was above 55 ℃, the secondary structure elements persisted even upon heating to 90 ℃. Meanwhile, upon heating from 65 to 80 ℃, the ratio of fluorescence intensities at 350 and 340 nm didn’t show that the protein was in the completely unfolded state. These results on well-folded secondary structure and tertiary structure variations imply stable integrated architecture of the protein and that the flexible β-grasp domain is responsible for binding to the diverse major histocompatibility complex (MHC) alleles. Besides, with increasing temperature from 70 ℃, the aggregation level increased visibly and reached its maximum at 90 ℃. Taken together, all data showed that the β-sheet/turn structure of rSEM and the formation of IS and the aggregation state were predominantly responsible for the structural stability at high temperature. Understanding the heat-induced unfolding process of rSEM will help in clarifying its heat resistance mechanism. In the future, using this method to study the heat inactivation mechanism of other types of staphylococcal enterotoxin will help in improving the food production process.
Synthesis, Characterization and Antioxidant Activity of Millet Bran Soluble Dietary Fiber-Cr(III) Complexes
QUAN Zhigang, WANG Weihao, ZHAO Shuting, LIU Dezhi, WANG Yifei, WU Yunjiao, SU Youtao, WEI Chunhong, CAO Longkui
2021, 42(21):  46-55.  doi:10.7506/spkx1002-6630-20200902-023
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Soluble dietary fiber (SDF) extracted from millet bran by enzymatic hydrolysis was coordinated with trivalent chromium ions in a weakly alkaline environment to produce SDF-Cr(III) complexes. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) were used to characterize the structures of SDF and SDF-Cr(III) complexes. Gel permeation chromatography (GPC) and high-performance liquid chromatography (HPLC) were used to determine their molecular mass distribution and monosaccharide composition. Their in vitro antioxidant properties were measured by 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH) radical, 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicla cation, and hydroxyl radical scavenging capacity and total antioxidant capacity. The results showed that the surface structure of SDF-Cr(III) was loose and porous, exhibiting a decrease in the aggregation degree of island-like bulges and more scattered intermolecular arrangements compared to SDF. A large difference was found between SDF and SDF-Cr(III) in functional groups. According to FTIR analysis, SDF-Cr(III) showed reduced stretching vibrations of the active functional groups (hydroxyl, ester, and carbonyl groups), a blue shift in the absorption maximum, and a Cr-O stretching vibration at 530.27 cm-1, confirming the binding Cr3+ to SDF. The number average molecular mass (mn), weight average molecular mass (mw) and molecular mass distribution width index (D) of SDF was 0.195 × 104 Da, 0.940 × 104 Da, and 4.81, while those of SDF-Cr(III) were 0.742 × 104 Da, 4.708 × 104 Da and 6.35, respectively as determined by GPC. HPLC showed that the relative content of monosaccharides in SDF-Cr(III) was higher than that in SDF. SDF-Cr(III) had stronger in vitro antioxidant properties compared to SDF. In conclusion, millet bran SDF-Cr(III) may have the potential to be developed into health products with hypoglycemic effect.
Extraction of Superoxide Dismutase from Tomato Using Amino Functionalized Ionic Liquid
WANG Tao, ZHAI Chen, WANG Liang, LI Mengyao, WANG Shuya, XIE Yunfeng
2021, 42(21):  56-62.  doi:10.7506/spkx1002-6630-20200905-062
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In this work, an aqueous two-phase system formed by an amino functionalized ionic liquid as a novel green solvent and inorganic salts was employed for extracting superoxide dismutase (SOD) from tomatoes. We investigated the effects of the type and concentration of ionic liquid, K2HPO4 concentration, extraction temperature and extraction time on the activity of SOD. Through the combined use of one-factor-at-a-time method and response surface methodology, the optimal extraction conditions that provided maximum SOD activity (345.68 U/g) were established as follows: concentration [(H2NC2)Mim]Br ionic liquid, 0.40 g/mL; K2HPO4 concentration, 0.60 g/mL; extraction temperature, 35 ℃; and extraction time, 25 min. Compared with the traditional buffer solution method and the [C4Mim]Br/K2HPO4-based aqueous two-phase extraction method, this method yielded higher SOD activity with smaller standard deviations. This research provides a new experimental idea for the extraction of protease substances in fruits and vegetables.
Inhibitory Mechanism of Mustard Essential Oil Inclusion Complex against Aspergillus aculeatus
LI Yanni, LI Fenfang, CHEN Jiao, LI Yixing, LIU Shisheng, HONG Keqian, FENG Jiancheng, YUAN Debao
2021, 42(21):  63-71.  doi:10.7506/spkx1002-6630-20201124-243
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The antimicrobial activity and mechanism of a mustard essential oil inclusion complex against the rambutan pathogen Aspergillus aculeatus by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and transcriptomics. It was found that the inclusion complex significantly inhibited the growth of Aspergillus aculeatus with a half-maximum effective concentration (EC50) of 1.00 g/L. SEM showed significant changes in the morphology of hyphae, conidia and apical cysts, and a significantly decreased number of spore apical cysts after treatment with the complex. TEM showed that the hyphal cells became no longer full, the cell wall became thin, the cell membrane boundary became blurred, and serious lysis was observed inside the cells. The transcriptomics results showed that there were 1 057 differentially expressed genes identified, of which 528 were up-regulated and the rest were down-regulated. Furthermore, eight differentially expressed genes were confirmed by real-time fluorescence quantitative polymerase chain reaction (qPCR), indicating that the trend of changes in the gene expression levels was consistent with the transcriptomic sequencing results. The antifungal mechanism may involve damaging the cell structure, affecting DNA and RNA synthesis and metabolism, inhibiting related enzyme activities, influencing the transmembrane transport capacity, inhibiting mitosis, and decreasing energy metabolism.
Food Engineering
Effect of Freeze-Thaw Treatment on Structural, Thermal, Mechanical and Physical Properties of Starch-Based Films
GAO Shan, YU Li, DENG Yun, WANG Danfeng, ZHONG Yu
2021, 42(21):  72-79.  doi:10.7506/spkx1002-6630-20201012-088
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A series of edible films were obtained using native potato starch (PS) or modified potato starches, including hydroxypropyl distarch phosphate (HDP), acetate starch (AS) and oxidized starch (OS) by the casting method. The effects of freeze-thaw (F-T) treatment on the physical, mechanical and barrier properties, microstructure and thermal stability of the films were studied. X-ray diffraction (XRD) indicated that potato starch granules displayed a typical B-type crystalline structure, the crystallinity was damaged during the film-forming process, and the peak intensity was decreased obviously after F-T treatment. F-T treatment damaged the microstructure of starch-based films as observed by scanning electron microscopy (SEM), and there appeared obvious cracks on PS film, and honeycomb-like and lamellar structures on AS film, while OS and HDP films maintained a more complete morphology. In the thermogravimetric curves of starch-based films, four stages of mass loss appeared as temperature increased, corresponding to water loss, volatilization of glycerol, and depolymerization and decomposition of starch, respectively. Nevertheless, F-T treatment had little effects on the thermostability. At room temperature, PS film had the best mechanical property with tensile strength (TS) of 2.29 MPa and elongation at break (EB) of 68.82%. After three F-T cycles, film TS increased at least twice and EB generally declined, while solubility and WVP changed only a little. HDP film displayed much better F-T stability considering the microstructure, mechanical property, water vapor permeability and water solubility collectively, indicating its potential applications in frozen low-moisture foods.
Preparation of Resveratrol Solid Dispersion by Electrospinning and Its Properties
DENG Jiao, LIU Xin, ZHENG Min, ZHOU Jun, LI Xiangzhou
2021, 42(21):  80-86.  doi:10.7506/spkx1002-6630-20200915-196
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A resveratrol/shellac ammonium salt (Res/SRAS) solid dispersion was prepared by electrospinning technology using Res as the core material and SRAS as the base material, and its stability and structure were investigated by physical property measurement, scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Also its in vitro release behavior and antioxidant activity were evaluated. The results showed that the encapsulation efficiency and loading rate of Res in the solid dispersion prepared with 2.0 g of SRAS, 0.222 g of Res and 10 mL of anhydrous ethanol were 79.06% and 7.91%, respectively. SEM analysis showed the solid dispersion was spherical in shape with a smooth surface and an average particle size of (843.75 ± 162.99) nm. FT-IR and XRD analysis showed Res was effectively encapsulated in SRAS forming stable Res/SRAS. DSC analysis showed Res/SRAS was stable thermodynamically. Res/SRAS maintained stable release in simulated gastric juice and the release rate was accelerated in simulated intestinal juice. The cumulative release rate of Res/SRAS in simulated gastric and intestinal juice after 10 h was 51.10% and 65.79%, respectively, revealing that the solid dispersion had enteric release properties. Furthermore, the antioxidant capacity of Res/SRAS was higher than that of free Res. The preparation of Res/SRAS with excellent performance by electrospinning technology is of reference significance for the development and utilization of resveratrol and its analogues in functional foods and health products.
Effect of Vacuum Precooling on Water Mobility and Pore Structure of Cooked Pork Ham Injected with Different Levels of Brine Solution
LIAO Caihu, LI Yifei, LUO Danxian, XIE Siyun, ZHONG Ruimin, YU Yigang
2021, 42(21):  87-96.  doi:10.7506/spkx1002-6630-20201125-256
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Vacuum precooling technology can play an important role in the cooling of low-temperature cooked meat by virtue of its fast cooling rate. In this study, the effect of vacuum precooling on the water mobility and pore structure of cooked pork ham injected with different levels (10%, 20%, 30% and 40%) of brine solution was evaluated, and in turn the effects of the water mobility and pore structure on the cooling rate were discussed using partial least squares regression (PLSR). The results showed that samples injected with 10% brine solution had a higher average cooling rate (0.94 ℃/min) compared to those injected with 20% (0.76 ℃/min), 30% (0.56 ℃/min) and 40% (0.68 ℃/min) brine solution during vacuum precooling (P < 0.05). The nuclear magnetic resonance (NMR) results showed that the relaxation peak areas of bound water (A21 and A22), immobile water (A23) and free water (A24 and A25) in all samples exhibited a decrease during vacuum cooling while the relaxation time of immobile water (T23) remained unchanged. In addition, vacuum precooling produced a wider range of pore size distribution, higher porosity and larger apertures than did the conventional precooling method. The loading plot showed that the average cooling rate exhibited a significant correlation with the transverse relaxation time and peak area of immobile water, cumulative pore volume and area, average pore diameter, tortuosity and permeability. The variable importance in projection (VIP) results revealed that immobile water exhibited a more significant effect on the average cooling rate compared to bound water and free water. In addition, the pore structure parameters average pore diameter, permeability and tortuosity more significantly affected the average cooling rate compared to the porosity determined by mercury porosimetry.
Structural Characteristics and Antioxidant Activity of Polysaccharides Prepared from Sea Cucumber Gonad by Ultrasound-Assisted Enzymatic Hydrolysis
WANG Jingjie, DU Xin, ZHONG Qiang, DONG Heliang, WANG Hao, XIA Xiufang
2021, 42(21):  97-104.  doi:10.7506/spkx1002-6630-20201215-186
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The structural characteristics and antioxidant activity of sea cucumber gonadal polysaccharide (SCGP) by ultrasound-assisted enzymatic hydrolysis (named SCGP-UAE) were evaluated in comparison with those prepared by enzyme-assisted extraction (named SCGP-E) and ultrasound-assisted extraction (named SCGP-U). The results showed that the total sugar content of the SCGP-UAE sample (69.13%) was significantly higher than that of the SCGP-E sample (58.76%) and the SCGP-U sample (62.93%) (P < 0.05). The ultraviolet and Fourier transform infrared (FTIR) spectra of the three polysaccharides showed similar characteristic absorption peaks. The results of Congo red experiment, scanning electron microscopy and thermal stability measurement showed that none of the polysaccharide samples contained a three-stranded helix structure, despite all showing an apparent lamellar structure and having good thermal stability. At 4 mg/mL concentration, the 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cation radical and superoxide anion radical-scavenging activity and Fe2+-chelating ability of SCGP-UAE were 5.59%, 14.05% and 26.63% higher than those of SCGP-U, and 2.16%, 33.59% and 47.10% higher than those of SCGP-E, respectively. In summary, the ultrasound-assisted enzymatic hydrolysis method could extract polysaccharides with good antioxidant activity from sea cucumber gonad in high yield and thus have great application potential.
Nutrition & Hygiene
Physicochemical Properties and in Vitro Digestion Properties of Infant Puree Made from Different Species of Raw Meat
LUO Mingyang, WU Juqing, NIAN Yingqun, ZHAO Di, YU Lili, LI Chunbao
2021, 42(21):  105-110.  doi:10.7506/spkx1002-6630-20201008-035
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This study was designed to investigate the effect of different species of raw meat (beef, pork and chicken) on the nutritional composition, rheological properties, and in vitro digestion properties of infant puree. The results showed that infant puree was found to be a high-protein, low-fat and high-moisture food. There were significant differences in the nutritional composition of the three meat purees investigated (P < 0.05). Beef puree had the highest protein content (11.01 ± 0.53)%, pork puree had the highest fat content (6.19 ± 0.42)% and chicken puree had the highest moisture content (81.15 ± 0.26)%. The rheological analysis showed that all products had a shear thinning behavior and weak gel-like properties dominated by elastic components. Their apparent viscosity and storage modulus (G’) showed a decreasing order of beef puree > pork puree > chicken puree. After two-step digestion with pepsin followed by pancreatin, the digestibility of pork puree was higher than that of the other two products and the particle size ranges of the three purees were reduced from 4.3–550.0 μm to 1.2–118.0 μm. After the digestion process, the particle size of beef puree was the smallest, (8.15 ± 0.94) μm, while there was no significant difference in particle size between pork puree and chicken puree. Overall, there were significant differences in physicochemical properties and digestibility among the three meat purees.
Structural Analysis and Anti-pancreatic Lipase Activity of Flavonoids from Chestnut Shells
HUANG Xuewei, LEI Sichao, TU Fen, XIE Chenyang, LI Jie, YANG Fang
2021, 42(21):  111-118.  doi:10.7506/spkx1002-6630-20201126-275
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This research analyzed the structures of flavonoids extracted from chestnut shells and studied their inhibitory effect on pancreatic lipase as well as the type of inhibition. The flavonoids were extracted with aqueous ethanol as the solvent and purified with AB-8 macroporous resin. The content of the freeze-dried flavonoids was (107.50 ± 1.00) mg/g, and the extraction yield was (5.66 ± 0.05)%. Eight flavonoids were identified from chestnut shells by ultra-performance liquid chromatography-quadrupole/electrostatic field orbitrap mass spectrometry (UPLC-Q-Orbitrap MS). The p-nitrophenol method was used to investigate the inhibitory effect of chestnut shell flavonoids on pancreatic lipase under different reaction conditions. The results showed that chestnut shell flavonoids had a strong inhibitory effect on pancreatic lipase with a half maximal inhibitory concentration (IC50) of 0.074 mg/mL, and resulted in an alkaline shift in the optimum pH of pancreatic lipase. The type of inhibition was measured as noncompetitive inhibition by Lineweaver-Burk plot, with an inhibition constant (Ki) of 53.19 mg/mL. Thus, chestnut shell flavonoids are good pancreatic lipase inhibitors.
Bioactivities of Peptides Derived from Hericium erinaceus Proteins by Enzymatic Hydrolysis
YU Yihan, DU Weining, HU Qiuhui, SU Anxiang, XU Hui, LIU Jianhui, XIE Minhao, YANG Wenjian
2021, 42(21):  119-127.  doi:10.7506/spkx1002-6630-20210104-035
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In this study, papain, flavourzyme, alcalase and trypsin were separately used to hydrolyze Hericium erinaceus proteins, yielding peptides designated as HEPH-P, HEPH-F, HEPH-A, and HEPH-T, respectively. Their antioxidant, anti-inflammatory activity, and antitumor activities were evaluated. The results showed that HEPH-P had good 2,2-di(4-tert-octylphenyl)-1-picrylhydrazyl (DPPH) radical and hydroxyl radical-scavenging activities, with scavenging percentages of (53.01 ± 0.27)% and (55.73 ± 1.52)%, respectively. HEPH-A showed anti-inflammatory activity by effectively controlling the release of NO and interleukin (IL)-6 and promoting the secretion of IL-10 in lipopolysaccharide (LPS)-induced RAW264.7 cells. HEPH-P resulted in the rupturing of the cell membrane, triggered apoptosis and ultimately inhibited the proliferation of liver cancer cells. This study can provide a theoretical basis for the development and application of functionally active peptides from Hericium erinaceus proteins.
Astaxanthin Protects Retinal Pigment Epithelial Cells from Oxidative Stress Induced by Blue Light Emitting Diodes
LIU Ying, MA Ning, LIU Yaojie, GUO Yatu, LI Heyu, SHAN Yanqin, CHEN Yunxia, WANG Hao
2021, 42(21):  128-136.  doi:10.7506/spkx1002-6630-20201017-154
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Objective: To investigate the protective effect of astaxanthin on oxidative stress injury induced by blue light-emitting diode (LED) in ARPE-19 cells and its underlying mechanism. Methods: The cells were pretreated with different concentrations of astaxanthin for 1 h followed by exposure to blue light LED for 24?h to induce photooxidative damage. The cell viability was determined by the MTT method, the cytotoxicity was determined by the lactate dehydrogenase (LDH) assay, the level of intracellular reactive oxygen species (ROS) was measured using 6-carboxy-2’,7’-dichorodihydrofluorescein diacetate (DCFH-DA) as a fluorescence probe, the change of intracellular mitochondrial membrane potential was measured using the fluorescence probe JC-1, and the activity of endogenous antioxidant enzymes was determined by commercial kits. The transcriptional expression level of phase II detoxification genes was measured by real-time fluorescence quantitative polymerase chain reaction (RT-qPCR), and the nuclear protein expression level of nuclear factor erythroid-related factor 2 (Nrf2) was measured by Western blot. Results: Astaxanthin (at 5, 10 and 20?μmol/L) pretreatment inhibited the decrease in the cell viability induced by blue light LED in a concentration-dependent manner, alleviated the cytotoxicity, reduced the production of intracellular ROS, stabilized the mitochondrial membrane potential and increased the activity of endogenous antioxidant enzymes. In addition, astaxanthin induced nuclear translocation of Nrf2 and increased the expression of antioxidant enzymes and phase II detoxification genes, thus protecting ARPE-19 cells from oxidative stress induced by blue light LED. Conclusion: Astaxanthin protects ARPE-19 cells from oxidative stress induced by blue light LED by inducing nuclear translocation of Nrf2 and promoting the expression of antioxidant enzymes and phase II detoxification genes.
Packaging & Storage
Inhibition of ZnO Nanoparticles on Microorganisms during Maize Storage
ZHANG Dongdong, HU Si, Zakir HAYAT, SONG Huiling, ZHOU Xianqing
2021, 42(21):  137-144.  doi:10.7506/spkx1002-6630-20201214-172
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As one of the main grain reserves in China, maize is subject to mildew due to its high moisture content, rich nutrients and high microbial load, resulting in the production of mycotoxins exceeding the safe limit. In this research, antimicrobial zinc oxide nanoparticles (ZnO-NPs) were prepared by a hydrothermal method under the optimized conditions as follows: using water as the solvent, n(Zn2+):n(OH-) of 1:8, water temperature of 120 ℃, and holding time of 6 h. The nanoparticles were spherical with an average diameter of 93 nm, and polydispersity index (PDI) of 0.024 as determined by dynamic light scattering. Characterization by energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) showed that the nanoparticles only contained Zn and O elements and had the unique crystal structure and chemical bond characteristics of ZnO. The ZnO-NPs had a significant inhibitory effect on the growth of bacteria and fungi. After 30 days of storage, the total viable count on maize with the ZnO-NPs was significantly lower than that on the control group, and the deterioration of maize quality was slowed down in the ZnO-NPs treatment group. Therefore, the ZnO-NPs could help to inhibit the growth of microorganisms during the storage of maize, which will provide data support for the development of new grain preservatives.
Respiratory Metabolism is Involved in Defense Responses to Trichothecium roseum in Muskmelon Fruit at Different Stages of Infection
XUE Sulin, NAN Mina, GONG Di, WANG Bin, JIANG Hong, Dov PRUSKY, BI Yang, XUE Huali
2021, 42(21):  145-152.  doi:10.7506/spkx1002-6630-20200717-232
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Objective: To reveal the roles of the tricarboxylic acid (TCA) cycle and the pentose phosphate pathway (PPP) in fruits infected by pathogenic fungi. Methods: Muskmelon fruit (cv. ‘Yujinxiang’) were artificially wounded and inoculated with Trichothecium roseum. The change of lesion diameter was observed during storage at ambient temperature (22 ± 2) ℃ and 55%–60% relative humidity. The changes in the activities of the key enzymes and the contents of intermediate products in the TCA cycle and PPP at the junction of diseased and healthy tissues were measured with the aim of evaluating the roles of the TCA cycle and PPP at different stages of infection. Results: Lesion diameter in infected fruit did not obviously change within 24 hours after inoculation, but then increased greatly at 48 h, and was significantly higher than that of the uninoculated control at 72 h (P < 0.05). At the early stage of infection, the activity of isocitrate dehydrogenase was inhibited significantly (P < 0.05) and the activity of malate dehydrogenase (MDH) was promoted significantly (P < 0.05) compared with the control, showing a 2.14-fold increase at 24 h. Meanwhile, the contents of nicotinamide adenine dinucleotide (NAD) and reduced nicotinamide adenine dinucleotide (NADH) were increased by 50.37% and 50.31% compared with those in the control group at 24 h, respectively. The infection also promoted NAD kinase activity. The activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were enhanced by 1.83 and 2.51 times relative to the control group at 48 h, respectively. The synthesis of reduced nicotinamide adenine dinucleotide phosphate (NADPH) and glucose-6-phosphate was accelerated at the late stage of infection (P < 0.05). In addition, the activity of ribose-5-phosphate isomerase and the content of ribulose-5-phosphate in infected fruit was significantly decreased at the early and middle stages. Conclusion: The TCA cycle in muskmelon fruit is induced at the early stage of Trichothecium roseum infection and PPP is stimulated at the late stage, indicating that the TCA cycle participates in defense responses in infected fruit mainly at the early stage, while PPP plays a more important role in defense responses at the late stage.
Preparation and Characterization of Konjac Glucomannan/Oleic Acid Modified ZnO Nanocomposite Antibacterial Film
CHEN Xiaohan, LU Hongzheng, PANG Jie, MU Ruojun
2021, 42(21):  153-160.  doi:10.7506/spkx1002-6630-20200731-419
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In order to improve the dispersion of zinc oxide (ZnO) nanoparticles in konjac glucomannan (KGM)-based films, and enhance the anti-ultraviolet (UV) and antibacterial properties of nanocomposite films, ZnO nanoparticles modified with oleic acid (OAZnO) was used to prepare KGM/OAZnO nanocomposite films by a casting method, and the effects of OAZnO on the structure and physicochemical properties of KGM-based films were studied by rheological analysis, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), microstructural observation, thermogravimetric analysis (TGA) and physicochemical measurements. The results showed that oleic acid (OA) improved the dispersity of ZnO nanoparticles. The FTIR analysis confirmed the formation of strong hydrogen bonds between ZnO nanoparticles and KGM. The XRD spectra showed that Zn2+ in ZnO nanoparticles formed coordination bonds with –OH on the KGM chain. Meanwhile, the appropriate amount (0.49 mL) of OAZnO nanoparticles enhanced the packaging-related mechanical and water barrier properties of nanocomposite films, decreasing water vapor permeability (WVP) by 35.62% and increasing tensile strength by 79.26% when compared with those of KGM films. In addition, KGM/OAZnO nanocomposite films had strong UV barrier and antibacterial properties. Therefore, addition of OAZnO especially at 0.49 mL could improve the overall performance of nanocomposite films, making it a candidate for use as a functional food packaging film to extend the shelf life of packaged foods.
Preparation of Chitosan Sulfobutylether-β-Cyclodextrin Nanoparticles and Its Effect on the Physical Properties of Sodium Alginate Film
SUN Weiyan, SU Zhiwei, ZHANG Fang, MENG Xianghong, LIU Bingjie
2021, 42(21):  161-167.  doi:10.7506/spkx1002-6630-20200826-347
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In order to establish optimal conditions for preparing nanoparticles from chitosan (CS) and sulfobutylether-β-cyclodextrin (SBE-β-CD), the effects of different preparation conditions on the particle size, polydispersity index (PDI) and zeta potential of nanoparticles were studied by single factor experiments. The nanoparticles were characterized by transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). Further, the effects of adding the nanoparticles to sodium alginate film on its mechanical properties (tensile strength, elongation at break) and physical properties (film thickness and water vapor permeability) were investigated. The results showed that the optimum conditions for preparing the nanoparticles were as follows: use of CS with molecular mass of 100 kDa; pH of CS solution, 4.0; CS concentration, 0.75 mg/mL, and mass ratio of CS to SBE-β-CD, 0.8:1. The particle size, PDI and zeta potential of the nanoparticles prepared under the optimized conditions were 245.1 nm, 0.068, and +30.2 mV, respectively. Under TEM, it was observed that the nanoparticles were uniform and regular spheres. FTIR showed that CS was electrostatically combined with SBE-β-CD, leading to enhanced hydrogen bonding. The tensile strength of the composite film with 1.00 mg/mL of CS/SBE-β-CD nanoparticles increased from 18.18 to 29.15 MPa, the elongation at break decreased from 38.91% to 26.42%, and the water vapor permeability rate dropped from 0.36 to 0.21 g·mm/(m2·h·kPa) compared with those of the blank control group. From these results, it was demonstrated that the addition of CS/SBE-β-CD nanoparticles could improve the mechanical and physical properties of sodium alginate film.
Influence of High Voltage Electrostatic Field Treatment on Physiological Quality and Metabolism of Cherry Tomato Fruits during Storage
YANG Zhichao, CAO Yang, SHEN Chaoyi, SUN Chongde, WU Di
2021, 42(21):  168-176.  doi:10.7506/spkx1002-6630-20201006-022
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Cherry tomatoes are popular among consumers because of their bright color and well-balanced sweet and sour taste. However, cherry tomatoes are easy to rot and deteriorate after harvest, and pathogenic bacteria on their surfaces are detrimental to the health of consumers when eaten raw. In this study, we studied the effects of high voltage electrostatic field (HVEF) treatment on the physiological quality and metabolism of ‘Huangfei’ cherry tomatoes by measuring fruit surface bacteria, decay rate and physiological indexes as well as conducting metabonomic analysis. The results showed that HVEF treatment could significantly reduce the total number of Escherichia coli colonies on the fruit surface (P < 0.05) and delay fruit decay during storage, while having no effect on respiration rate or mass loss rate. In addition, it inhibited ethylene release at the early storage stage. The results of metabonomic analysis showed that differential metabolites were identified between the HVEF treatment and control groups, and there were a variety of up-regulation and down-regulation patterns. Particularly, the contents of some flavonoids and alkaloids increased after the treatment. In summary, HVEF treatment could reduce the decay incidence and surface pathogenic bacteria of postharvest cherry tomato fruit and improve its quality.
Comparison of Phenylpropane Metabolism and Callus in Peel and Pulp of Pumpkin during Wound Healing
LIANG Wei, ZHU Yatong, KONG Rui, CHAI Xiuwei, XIE Pengdong, BI Yang, Dov PRUSKY
2021, 42(21):  177-185.  doi:10.7506/spkx1002-6630-20201202-030
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Objective: To compare the differences in the key enzyme activities and product contents related to phenylpropane metabolism and the accumulation of suberin polyphenolics and lignin in the peel and pulp of pumpkin during wound healing. Methods: Artificially wounded pumpkins were kept at room temperature in darkness for healing. The activities of the key enzymes associated with phenylpropane metabolism and peroxidase and the contents of metabolites and H2O2 in the peel and pulp of pumpkins were determined, and the accumulation of suberin polyphenolicand lignin were observed. Results: During wound healing, higher contents of cinnamic acid, p-coumaric acid, caffeic acid, ferulic acid, sinapic acid and total phenolics as well as higher contents of p-coumaroyl alcohol, coniferyl alcohol, sinapyl alcohol and lignin were accumulated in the peel than in the pulp, and the accumulation rates and amounts of suberin polyphenolics and lignin were pronouncedly higher in the peel than in the pulp. The thickness of suberin polyphenolic and lignin cell layers in the peel were 17.55% and 24.37% higher than those in the pulp on the 7th day, respectively. Meanwhile, the activities of phenylalanine ammonia-lyase (PAL), cinnamic acid-4-hydroxylase (C4H), 4-coumaryl coenzyme A ligase (C4L), cinnamyl alcohol dehydrogenase (CAD) and peroxidase (POD) were 24.71%, 42.31%, 21.65%, 13.41% and 37.51% higher in the peel than in the pulp on the 5th day, respectively. Moreover, the H2O2 content in the peel was higher significantly (P < 0.05) than that in the pulp, with a 32.75% increase being observed on the 7th day. Conclusion: The peel of pumpkin showed higher phenylpropanoid metabolism-related key enzymeactivities and products contents and higher H2O2 content and peroxidase activity as well as higher accumulation rates and amounts of suberin polyphenolics and lignin than did the pulp. In summary, epidermis injuries in pumpkin fruit can heal fast, while flesh injuries cannot heal easily but instead aggravate the occurrence of rot. Therefore, deep injuries to pumpkin flesh should be avoided as much as possible during postharvest handling.
Preparation of Inclusion Complex of Boesenbergia rotunda Essential Oil and Its Effect on Preserving the Flesh Quality of Grass Carp during Refrigeration
WANG Ya, LI Rong, JIANG Zitao, WANG Ying, TAN Jin, TANG Shuhua
2021, 42(21):  186-193.  doi:10.7506/spkx1002-6630-20200907-095
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In order to explore an efficient technical solution to preserve the flesh quality of grass carp during refrigeration, an inclusion complex of Boesenbergia rotunda essential oil (BEO-K-β-CD-MOF) was prepared using β-cyclodextrin potassium metal organic framework as the wall material. The inclusion complex was characterized by Fourier transform infrared spectroscopy and X-ray diffraction, and its light, heat and acid-base stability were also evaluated. To evaluate its preservative effect on grass carp flesh, changes in the percentage water loss, thiobarbituric acid reactive substances (TBARS) value, texture and color of fish samples added with the inclusion complex were measured during cold storage ((4 ± 1) ℃). The results showed that compared with the untreated control group, the percentage water loss and TBARS value of grass carp flesh added with the inclusion complex were reduced by 35.0%–64.0% and 46.0%–71.0%, respectively at day 10 of storage. The decrease in hardness, elasticity and chewiness after 10 days of storage were 9.2%–13.6%, 9.9%–22.3%, and 26.2%–38.2% lower relative to the control group, respectively, and the color change (reflected by the proportion of color No. 2712, light grayish brown) was 59.6%–80.0% lower on day 10. It was indicated that BEO-K-β-CD-MOF had an obvious preservative effect on grass carp.
Reviews
Advances in the Correlation between the Subtyping of Listeria monocytogenes and Its Pathogenic Potential Genes
CHENG Ying, DONG Qingli, LIU Yangtai, LI Hongmei, WANG Yuan, WANG Xiang
2021, 42(21):  194-201.  doi:10.7506/spkx1002-6630-20200728-356
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Listeria monocytogenes is a common foodborne pathogen that can be classified into many subtypes. Different subtypes of L. monocytogenes have different pathogenic potentials, depending on their resistance and virulence genes. This review article summarizes the relationship between different subtypes of L. monocytogenes and its potential pathogenic genes. It is found that L. monocytogenes has many heat, cold resistance, acid, hypertonic stress, desiccation, metal and disinfectant resistance genes and genes involved in the regulation of stress protein expression. To date, there has been no clear conclusion on the relationship between these genes and subtyping, although stress survival island 1 has been found to exist only in some strains of lineage I and II. Stress survival island 2 has been found only in ST121 strains. The virulence genes of L. monocytogenes are reviewed from the aspects of functional virulence genes and Listeria pathogenicity islands (LIPI). LIPI-3 and LIPI-4 are mainly found in lineage I strains. Premature stop codons appear in advance in the inlA gene of the ST5, ST8, ST9 and ST121 strains, reducing the virulence of the strains. Therefore, exploring the differences in the potential pathogenic genes in different subtypes of L. monocytogenes will help prevent and control Listeria monocytogenes contamination.
Progress in Research on the Effect of Postmortem Aging on the Quality of Fresh Meat
LIU Zechao, LUO Xin, ZHANG Yimin, MAO Yanwei, DONG Pengcheng, ZHANG Wenhua, YANG Xiaoyin, LIANG Rongrong
2021, 42(21):  202-212.  doi:10.7506/spkx1002-6630-20200710-147
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Postmortem aging has been extensively applied as a value-added approach in the meat industry for many years all over the world. A series of biochemical changes that occur in the transformation of muscle to meat during the early postmortem period and those occurring during the subsequent aging process may have an important effect on meat quality. Therefore, developing the optimal postharvest aging strategy and introducing some innovative technologies in postmortem aging is particularly important for improving meat quality (especially tenderness). In recent years, understanding the postmortem physiological and biochemical mechanisms of muscle and pursuing breakthroughs in developing new aging techniques have been a hot spot in this field. However, a comprehensive review on the latest progress in this field is lacking. Hence, the physiological and biochemical changes in muscle during the early postmortem period that determine meat quality are summarized in this review article. Meanwhile, the effects of the currently available aging methods including dry and wet aging on meat quality are overviewed, and the development of new aging techniques and their effect in improving meat quality are discussed. This review is expected to provide theoretical and technical guidance and development ideas for meeting consumers’ increasing need for high-quality meat and promoting the development of the meat processing industry in China.
Recent Progress in Understanding the Characteristics and Mechanisms of Flavan-3-ols Absorption and Metabolism in Humans
LIU Ruonan, CHEN Wanbing, YAN Fangfang, LIU Min, LU Qun, YANG Hong, LIU Rui
2021, 42(21):  213-222.  doi:10.7506/spkx1002-6630-20200605-069
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Flavan-3-ols are one of the most abundant classes of dietary polyphenols in the human diet. In recent years, flavan-3-ols have attracted much attention because many studies have found that they are associated with reduced risks of many chronic diseases and alleviation of metabolic syndromes. However, the role of flavan-3-ols in the body depends to a certain extent on their absorption and metabolism after being ingested, especially their catabolism by intestinal microbes. In this context, this article focuses on reviewing the signaling pathways related to the absorption, metabolism and biotransformation of flavan-3-ols, which will be helpful for understanding their biological effects in the body.
Advances in the Application of Metal-Organic Frameworks for Food Detection
LI Guanghua, LIU Sha, KANG Kai, DENG Sumei, KANG Weijun, GAO Zhixian
2021, 42(21):  223-234.  doi:10.7506/spkx1002-6630-20200804-058
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Food safety has always been a hot issue of social concern. In order to ensure food safety and human health, the detection of food contaminants is the key to controlling and eliminating the health risk caused by them. Therefore, it is of great significance to develop a sensitive and accurate assay for food contaminant detection. Metal-organic frameworks (MOFs) are a new class of porous crystal materials self-assembled by metal ions or metal clusters and organic ligands. The material has many advantages such as high porosity, large specific surface area, adjustable structure and various functions. MOFs can be combined with a variety of sample pretreatment and analytical techniques, making it a promising candidate for application in food safety analysis. This paper reviews the recent progress in the application of MOFs and MOF composite materials in food detection mainly as sensor materials and sample pretreatment materials for chromatography, and discusses their future applications in the field of food safety.
Progress in Research on Molecular Mechanisms of Decontamination Technologies Applied in Critical Control Points for the Microbiological Safety of Chilled Meat
YANG Jun, LUO Xin, LIANG Rongrong, ZHU Lixian, HAN Mingshan, YANG Xiaoyin, ZHANG Yimin
2021, 42(21):  235-245.  doi:10.7506/spkx1002-6630-20201008-039
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Meat industries use many decontamination technologies to improve the safety and storability of chilled meat during the production and circulation process. Spraying organic acids on carcasses, disinfection with electrolyzed water, and modified atmosphere packaging are commonly used as hurdle factors in the three critical control points for the microbiological safety of chilled meat, namely, slaughtering, carcass segmentation, and storage and distribution, respectively. At present, understanding the molecular mechanisms behind various decontamination technologies using omics approaches has become a research focus. However, there have been few systematic reviews of the molecular mechanisms behind and the associations among various decontamination technologies in recent years. Therefore, this review summarizes the effects of the above three decontamination technologies on physiological and biochemical responses of common pathogenic bacteria (e.g., Listeria monocytogenes and Escherichia coli O157:H7) and spoilage bacteria (e.g., Pseudomonas, Brochothrix thermosphacta and lactic acid bacteria) based on their protein expression and metabolic regulation. It has been found that although the decontamination technologies can influence bacterial intracellular protein expression and metabolic pathways, they work mainly by destroying the cell wall, membrane and flagellum or damaging their structural proteins and other components, and interfering with carbohydrate metabolism pathways such as glycolysis, the pentose phosphate pathway and the tricarboxylic acid cycle and amino acid metabolism pathways such as valine and leucine. This manuscript also reviews the influence of stress resistance in some specific bacteria induced by self-regulation of stress response on the efficiency of the decontamination technologies. This review may provide a theoretical guidance for meat industries to conduct the targeted control of bacterial contamination for improved preservation of chilled meat during the whole processing chain.
Progress in the Study of the Effect of Food Processing Environmental Stresses on Listeria monocytogenes Biofilm Formation
WANG Yuan, SUN Linjun, CHENG Ying, WANG Xiang, LIU Yangtai, LIN Yuhai, DONG Qingli
2021, 42(21):  246-255.  doi:10.7506/spkx1002-6630-20200702-034
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The growth of Listeria monocytogenes biofilm in the environment can lead to repeated food contamination. Refrigeration, drying, acid and disinfectant treatments commonly used in food processing and storage affect the biofilm formation of Listeria monocytogenes because of keeping it in stress environments for a long period of time. This paper summarizes the effects of common environmental stresses relevant to food processing on the biofilm formation of L. monocytogenes with an emphasis on disinfectant treatment. Meanwhile, the mechanism of biofilm formation by L. monocytogenes under stress conditions is elaborated from the perspectives of adaptation strategies related to membrane fluidity, biofilm-associated proteins, gene regulation and expression, which will be helpful to understand the formation and evolution of L. monocytogenes biofilm in real environments. Consequently, setting standards for cleaning and disinfection by taking environmental factors into full consideration is conducive to reducing the potential risk of foodborne pathogen transmission.
Recent Progress on Understanding the Effect of Food Processing on Structural and Functional Properties of Hemoglobin
WU Sujuan, LIU Zhanmin, WANG Zhaoming, ZHOU Hui, ZHOU Kai, XU Baocai
2021, 42(21):  256-262.  doi:10.7506/spkx1002-6630-20200801-019
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Hemoglobin is the most abundant protein in blood and can be utilized as an additive in foods. As a high-quality protein with excellent functional properties, hemoglobin can endow foods with good quality during their production, storage, processing and consumption. Many food processing conditions can alter the structure of hemoglobin, which in turn may lead to changes in its functional properties. This review will focus on the recent advances in the understanding of the structural changes of hemoglobin during food processing and the consequently varied functional properties, which is expected to guide the control of the functional properties of hemoglobin in food processing.
Progress in Research on the Evolutionary Lineages of Listeria monocytogenes
ZHOU Jifu, WANG Ping, GUO Jia, ZHAO Xiaomei, CHEN Ying
2021, 42(21):  263-270.  doi:10.7506/spkx1002-6630-20201009-053
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Listeria monocytogenes is one of the most harmful foodborne pathogens. As a facultative anaerobic gram-positive bacterium, it is widely present in foods, the environment and animal hosts. According to different molecular characteristics and epidemic situations, it can be divided into four evolutionary lineages, and strains from each lineage have different virulence and pathogenicity. This article analyzes the pathogenicity and epidemic characteristics of different lineages of Listeria monocytogenes. We expect that this review will provide a reference for studies on foodborne diseases related to Listeria monocytogenes lineages.
Progress in Risk Ranking for Food Safety in China
WANG Fang, SUN Xiaohong, TAO Guangcan
2021, 42(21):  271-277.  doi:10.7506/spkx1002-6630-20210228-303
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The purpose of food safety risk ranking is to ensure food safety through comprehensively evaluating static and dynamic food safety risk factors. Food safety risk ranking can improve the efficiency of food safety regulation by optimizing regulation resources, thereby laying the foundation for food safety management. The current status of research on food safety risk ranking is summarized in this review article, and the advantages of food safety risk ranking for the various entities involved in food safety regulation are analyzed based on the current situation and features of the food industry in China. Problems existing in this field of research are discussed and possible solutions to the problems are proposed. It is hoped that this review will promote the development of food safety risk ranking and thereby improve the efficiency of food safety regulation.
Progress in Research on the Structure and Immune-Regulating Effect of Lactobacillus Lipoteichoic Acid
GUAN Manti, ZHANG Yingchun, LU Weihong, WANG Ao
2021, 42(21):  278-284.  doi:10.7506/spkx1002-6630-20200724-325
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As a probiotic, Lactobacillus is an indispensable microorganism in the intestinal tract of humans and most animals. In recent years, due to the continuous development of science and technology, the focus of Lactobacillus research has shifted from the live cells to the cell surface components. Teichoic acid is one of the major components of the bacterial cell wall. Especially, lipoteichoic acid anchored to the cell membrane has attracted people’s attention as it is an active component responsible for host immune regulation. This paper reviews the physicochemical properties, extraction methods and biological activities of lipoteichoic acid, including participating in the adhesion and colonization of Lactobacillus to the host and intestinal immune regulation in vivo and in vitro, as well as the effect of lipoteichoic acid mutation on the strain. We hope this review will provide a reference for research on the immune-regulating effect of Lactobacillus.
Recent Advances in Quality Deterioration and Preservation of Postharvest Flammulina filiformis
ZHANG Yu, YUN Jianmin, BI Yang, WANG Ting, HE Kui
2021, 42(21):  285-291.  doi:10.7506/spkx1002-6630-20200803-031
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Because of its strong respiration and high water content, fresh Flammulina filiformis is extremely susceptible to a series of deterioration phenomena such as cap opening, browning and wilting during its?storage, which can seriously affect the postharvest sale of F. filiformis. Therefore, this review summarizes the major manifestations and causes of water loss, morphological deterioration, browning, loss of nutrition and flavor and microbial infection of F. filiformis after harvest. The research progress in the field of F. filiformis preservation in recent years was reviewed, including low-temperature preservation, ozone preservation, 1-methylcyclopropene preservation, modified atmosphere preservation, biological preservation agent preservation and compound preservation technology, which would provide a reference for the development of a new green and safe technology for mushroom preservation.
Progress in Research on the Mechanism Underlying the Influence Hypoxia Stress on Fish Meat Quality
ZHAO Manman, XIONG Guangquan, SHI Liu, SUN Weiqing, QIAO Yu, WU Wenjin, DING Anzi, LI Xin, WANG Lan
2021, 42(21):  292-298.  doi:10.7506/spkx1002-6630-20201013-102
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Oxygen is indispensable for fish to survive. Hypoxia stress can activate the cell hypoxia signal transduction pathway and hence cause energy metabolism disorders. Abnormal energy metabolism can cause significant adverse effects on fish meat quality. This article discusses the effects of hypoxia stress on the growth and development of fish and glucose, lipid and protein metabolism, as well as fish meat quality. It is expected to make guiding suggestions for improving fish meat quality, and provide a theoretical basis for uncovering the mechanisms of energy metabolism and meat quality changes in fish during hypoxic stress.
Recent Progress on Application of Cold Plasma Technology in Protein Modification
WANG Junpeng, HE Zhifei, LI Minhan, QI Shichao, LI Hongjun
2021, 42(21):  299-307.  doi:10.7506/spkx1002-6630-20200716-216
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Protein is an essential nutrient for the human body. Its nutritional value and functional characteristics determine the quality and stability of food processing. However, the functional properties of natural proteins cannot meet the needs of the modern food industry and thus needs to be improved. As an emerging non-thermal processing technology, cold plasma technology has the advantages of low-temperature operation, no need for chemical reagents and low cost. It can retain the nutritional value of proteins to the maximum while improving the functional properties. This paper summarizes the advantages and disadvantages of different generation methods for cold plasma and the current status of its application in the field of foods. Recent studies applying cold plasma to improve protein functional characteristics are systematically reviewed in order to provide theoretical support for its application in protein modification.
Food 3D Printing Technology and Its Application in Meat Processing: A Review
YANG Genghan, HUANG Mingyuan, XU Xinglian
2021, 42(21):  308-314.  doi:10.7506/spkx1002-6630-20201012-084
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Food 3D printing technology is a future food processing technology with the functions of customizing specific shapes, realizing personalized nutrition and developing new resources. In the meat industry, the application of food 3D printing technology can upgrade the meat processing industry chain by reducing the waste of raw meat, increasing the added value of products, and developing by-products of livestock and poultry. Therefore, this article introduces the reader to the operating principle of food 3D printing technology, overviews recent studies on the printability of meat materials. Meanwhile, it presents an outlook on the application of food 3D printing technology in meat production and processing. This review is expected to provide a scientific and theoretical basis for the application of food 3D printing technology in the field of meat products.
Mycotoxin Contamination and Prevention Measures in Dry-Cured Meat Products: A Review
GUO Keyu, WANG Song, TANG Lin, OUYANG Wanlin, LIU Mengru, LIU Shuliang, YANG Yong, GUO Hongxiang, CHEN Shujuan
2021, 42(21):  315-321.  doi:10.7506/spkx1002-6630-20200721-274
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Dry-cured meat products are susceptible to contamination by fungi during their production and storage. Some filamentous fungi in dry-cured meat products can produce mycotoxins under certain conditions, increasing the risk of toxin contamination in meat products and threatening human health seriously. In the current review, we provide a systematic discussion on the sources, types and hazards of mycotoxins in dry-cured meat meats such as aflatoxins, ochratoxin A, citrinin and cyclopiazonic acid, and summarize the current status of mycotoxin contamination in dry-cured meat meats in China and around the world with special focus on the prevention measures. It is hoped that this review could provide inspirations for the production of safer dry-cured meat meats.
Progress in Research on the Hypoglycemic Effect and Mechanism of Plant-Derived Active Ingredients
JIN Fei, ZHU Liyun,, GAO Yongsheng, ZHAO Qian, XU Xiaohui, LOU Chengnan
2021, 42(21):  322-330.  doi:10.7506/spkx1002-6630-20200926-327
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Diabetes is a metabolic disease characterized by hyperglycemia. Controlling and lowering blood glucose is an effective way to treat diabetes. Discovering and developing natural plant-derived active ingredients superior to traditional antidiabetic agents and exploring their hypoglycemic effects and mechanisms are of great significance for the prevention and treatment of diabetes. This paper analyzes the ingredients and potency of the traditional Chinese patent medicines commonly used for lowering blood glucose. Plant-derived volatile (essential oils, active monomer components) and non-volatile (polysaccharides, saponins, polyphenols and alkaloids) ingredients with hypoglycemic activity are reviewed with respect to their potency and mechanism of action as well as the experimental models used in this regard. It is expected that this review could provide a theoretical basis for the application of plant-derived hypoglycemic ingredients to defend against diabetes.
Regulation and Developmental Strategies of Cultivated Meat: An Overview
LI Shilei, LI Yingying, LI Yushuang, LIU Wenting, WANG Shouwei
2021, 42(21):  331-337.  doi:10.7506/spkx1002-6630-20210126-290
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Cultivated meat is also called biocultivated meat and cultured meat. Because it can provide humans with real animal protein while bypassing animal feeding, cultivated meat is considered to be one of the most potential solutions to the dilemma of meat production and consumption by humans in the future. Therefore, it has an extremely high potential commercial value. However, global regulatory systems have not had any regulatory practical experience on this new type of meat food. It is urgent to establish a regulatory policy system covering the entire process from the production to the consumption of cultivated meat. As the world’s most populous country, China has a huge annual meat production and consumption volume with a rapid growth rate, making it a promising market for the development of the cultivated meat industry. Therefore, China needs to make an overall plan for the construction of a regulatory system for cultivated meat at the national level in advance in order to cope with the new challenges posed by the continuous progress of science and technology and to promote the rapid development of related industries. This review article summarizes the regulatory practices and innovative explorations of the United States, Singapore and the European Union on cultivated meat and proposes some policy recommendations for the establishment of a cultivated meat regulatory system in China following the strategic, guiding and practical principles based on the current status of the development of cultivated meat and related regulatory practices in the country.
Progress in Research on Formation Mechanism and Control Methods for Acrylamide and Heterocyclic Amines during Food Frying
QI Daisha, ZHANG Qing
2021, 42(21):  338-346.  doi:10.7506/spkx1002-6630-20201009-052
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During food frying, various components from foods and the frying oil can undergo strong chemical reactions to produce a variety of chemical products, which may ultimately affect the eating quality of the fried foods and the useful life of the frying oil. A variety of harmful substances can be produced at amounts that cannot be ignored, such as concomitant acrylamide and heterocyclic amines related to constituents of fried foods. The production of these harmful components can be inhibited or controlled by selecting appropriate frying conditions, such as the type of frying oil, frying time, frying temperature, and the addition of exogenous antioxidants. This article reviews recent findings on the formation pathways, hazards, and control of acrylamide and heterocyclic amines during food frying, which will hopefully provide valuable information for exploring effective methods to inhibit the production of hazardous concomitants during food frying.
Electrochemical Immunosensors and Their Application in the Detection of Proteins: A Literature Review
YANG Qianwen, LIU Xiaofeng, ZENG Haijuan, WANG Jinbin
2021, 42(21):  347-354.  doi:10.7506/spkx1002-6630-20200729-375
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Electrochemical biosensors are a rapid qualitative or quantitative detection method that combines sensing technology with immunoassay. In recent years, with the fast development of nanomaterials, electrochemical immunosensors have become promising candidates for application in the field of protein detection with higher sensitivity, portability and specificity. This article focuses on the construction principle of electrochemical immunosensors and on recent progress in the development and application in protein detection of electrochemical immunosensors based on new nanomaterials. Moreover, future directions in this field are also discussed. It is expected to provide technical reference for rapid detection of protein.
Progress in Understanding the Effect of Lipid Oxidation on the Formation of Four Types of Harmful Substances in Meat Products
YANG Yifang, YU Qinxin, XIAO Zihan, WANG Yilun, LIU Yuxuan, HUANG Xiaohong, YANG Yong
2021, 42(21):  355-364.  doi:10.7506/spkx1002-6630-20200929-367
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Lipid oxidation concomitantly occurs during meat processing. Existing research shows that lipid oxidation can affect the formation of harmful substances such as heterocyclic amines (HAs), N-nitroso compounds (NOCs), advanced glycation end products (AGEs) and polycyclic aromatic hydrocarbons (PAHs) in meat products. The substances mentioned above will reduce the food safety of meat products and endanger human health. This article reviews the mechanism of lipid oxidation in meat products and the reactivity of oxidation products, as well as the influence of lipid oxidation on the formation of the above four harmful substances in meat products and the available control measures for it. It is expected that this review will provide guidance for improving the food safety of meat products by controlling lipid oxidation.
Progress in Understanding the Emulsification Properties of Soy Protein Modified by Extrusion Pretreatment and Enzymatic Hydrolysis
ZHU Xiuqing, LIU Yanqing, ZHU Ying, JIANG Yongpeng, LIU Linlin
2021, 42(21):  365-371.  doi:10.7506/spkx1002-6630-20200819-245
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Soy protein has poor emulsification characteristics due to its large molecular mass, compact structure, and slow oil droplet adsorption rate, hindering its application in food processing. Therefore, improving the emulsifying properties of soy protein is becoming a research hotspot. This article reviews the latest progress in understanding the effect of extrusion pretreatment and/or enzymatic hydrolysis on improving the emulsifying properties of soy protein. The conformational changes of soy protein during the modification processes, the protein-protein interactions, and the improvement of emulsifying properties are analyzed. We believe that this review will provide theoretical support for exploring the mechanism by which extrusion combined with enzymatic hydrolysis can improve the emulsifying properties of soy protein and for its industrial application.
Characteristics and Development of Milk Fat Globule Membrane and Its Applications in Simulating Human Milk Fat Globule Structure
LI Xiaodong, PAN Yue, LIU Lu, ZHU Qipeng
2021, 42(21):  372-379.  doi:10.7506/spkx1002-6630-20200817-212
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The milk fat globule membrane (MFGM) is a three-layer membrane structure that surrounds milk fat globules. The structure of fat globules in cow milk-based and soy-based infant formulas, lacking MFGM, is quite different from that in human milk. Therefore, addition of exogenous MFGM and preparation of infant formulas with fat globule structure similar to that in human milk have become the focus of recent research. In this article, we review the characteristics and development of MFGM, as well as the application of bovine MFGM in emulsions and infant formulas mimicking the human milk fat globule structure. Simulated in vitro infant gastrointestinal digestion and rodent studies in vivo have demonstrated that the mimic structure of human milk fat globule in emulsions and infant formulas can promote fat digestion and improve lipid metabolism in infants.