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15 April 2021, Volume 42 Issue 7
Invited Papers
Advances in G-Protein Coupled Estrogen Receptor and Its Application in Food Function Evaluation
LU Dingqiang, PANG Guangchang
2021, 42(7):  1-28.  doi:10.7506/spkx1002-6630-20201225-289
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A large number of studies have shown that although phytochemical, Chinese herbal medicines and phytoestrogens are abundant and diverse, they show common structural and function characteristics, and almost all of them have estrogenic characteristics. It has also been found that most phytoestrogens and estrogen receptors (ERs), especially ERα and ERβ, can mutually recognize each other and further interact with the nuclear receptor superfamily to regulate gene expression and modification in the nucleus, thus controlling nutrient and energy metabolism as well as epigenetic adaptation. However, it is crucial that these phytoestrogens not only control the slow transcription-based signaling pathways, but also regulate the fast calcium channel-based neural and endocrine signaling pathways. The latter has been known to rely on G-protein coupled receptors (GPCRs). In recent years, it has found that GPR30/G-protein coupled estrogen receptor (GPER) is the key node that constitutes both signaling pathways. This paper summarizes recent progress in research on GPER and its application for evaluating the functional quality of foods, and it presents an outlook on future prospects in this field.
Basic Research
Purification and Antimicrobial Mechanism of Amylocyclicin W5 Produced by Bacillus amyloliquefaciens DH8030
WANG Wei, LI Jinjin, CHI Hai
2021, 42(7):  29-34.  doi:10.7506/spkx1002-6630-20200407-082
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In this study, amylocyclicin W5, a bacteriocin produced by Bacillus amyloliquefaciens DH8030, was purified by sequential use of ammonium sulfate precipitation, ion exchange chromatography and ?KTA purification system, and it was analyzed by Tricine-sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Bacillus cereus LMGT2805 was employed as an indicator strain to evaluate the antibacterial effect of amylocyclicin W5. The changes in cell morphology and the intracellular structure induced by the bacteriocin were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the optimal degree of saturation of ammonium sulfate precipitation was 70%. In addition, 0.5 mol/L NaCl could significantly elute adsorbed bacteriocin from HiPrep SP XL 16/10 column. The eluate was fractionated by using ?KTA purification system into two fractions (F1 and F2). From bacteriostatic experiments, it was found that F2 but not F1 had a bacteriostatic effect against Bacillus cereus LMGT2805. The molecular mass of F2 was determined to be about 12.3 kDa. Amylocyclicin W5 at high concentration (four-fold higher than the half-minimal inhibitory concentration (MIC50) could completely inhibit B. cereus LMGT2805, and its antimicrobial mechanism was by destroying the cell wall to form holes and thus causing the leakage of intracellular contents, abnormal metabolism and finally cell death. These results provide data supporting the development of amylocyclicin W5 and its application in the field of food safety.
Data Mining Model for Food Safety Incidents Based on Structural Analysis and Semantic Similarity
CHEN Mo, ZHANG Jingxiang, HU Enhua, WU Linhai, ZHANG Yi
2021, 42(7):  35-44.  doi:10.7506/spkx1002-6630-20200505-027
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Food safety concerns public health and the stability of society. In this paper, we analyzed the characteristics of the food safety incidents (FSIs), including spatial distribution, food categories, risk factors, and supply chain links, reported by mainstream media in China. Based on our analysis, we constructed a semantic template for text data related to FSIs. Moreover, we introduced a strategy of multi-layer and multi-level semantic structure of rank (MMSS-Rank) algorithm to measure the similarity between the collected food safety data and the semantic template, and then calculated the overall scores and selected an appropriate threshold to determine the accuracy of the FSI data. Supporting vector machine and semantic structure template are adopted to conduct the classification accuracy comparison via data extraction and cleansing.Results showed that compared with the traditional methods, MMSS-Rank was an efficient and robust method for identifying large-scale FSI data with higher accuracy and recall rate.
Inhibition and Mechanism of Action of Truncated Phospholiase A1 Accessory Protein S from Serratia marcescens against Escherichia coli
GAN Yufei, XUE Zhenglian, ZHOU Jie, WANG Fang, WANG Zhou, LIU Yan
2021, 42(7):  45-51.  doi:10.7506/spkx1002-6630-20200318-273
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The helper protein encoded by the phospholipase A1 accessory protein S (plaS) gene of Serratia marcescens can significantly improve the expression and activity of phospholipase A1 in Escherichia coli, but it can inhibit the growth of the host strain; however, the underlying mechanism has not been reported. The key gene regions involved in the growth inhibitory effect of PlaS were determined by bioinformatic analysis and the growth characteristics of the expression strains constructed by truncating the sequence encoding 23, 24, 25, 26 and 27 N-terminal amino acids of PlaS (dS23P28, dS24P28, dS25P28, dS26P28 and dS27P28), and the inhibitory mechanism was preliminarily investigated by scanning electron microscopy (SEM) and flow cytometry (FCM). The results indicated that dS23P28, dS24P28, dS25P28 and dS26P28 showed growth inhibition to different extents, while dS27P28 did not. Preliminary results showed that the first 27 amino acids at the PlaS N-terminal were crucial for its inhibitory effect. The results of SEM and FCM showed that the expressed PlaS caused serious damage to the cell morphology of E. coli, while this effect disappeared after truncation of 27 amino acids from the N-terminal. These results were consistent with the growth characteristics. This study provides a theoretical basis for further studies on the functions of Serratia marcescens PlaS.
Physicochemical Properties of Muscles from Different Parts of Giant Hybrid Sturgeon
HUANG Pan, GAO Ruichang, BAI Fan, XU Peng, GONG Chen, WANG Ruihong, WANG Jinlin, ZHAO Yuanhui
2021, 42(7):  52-59.  doi:10.7506/spkx1002-6630-20200331-453
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In this study, in order to explore the feasibility of processing sashimi of giant hybrid sturgeon (Huso dauricus × Acipenser schrenckii), muscle samples from different parts of the fish were evaluated for physicochemical properties such as protein content and composition, color, hardness and tenderness, as well as sensory and hygienic characteristics and in vitro digestibility. The results showed that the ventral muscle had lower salt-soluble protein content (47.1%–51.8% versus 55.4%–63.6% and 56.3%–66.1%) and higher water-soluble protein content than the dorsal and tail muscle of giant hybrid sturgeon. The color changed from bright red to dark crimson in the direction from the head to the tail. The hardness decreased first and then increased in the direction from the head to the tail, and the hardness of the ventral muscle (109.2–149.1 N) was higher than that of the dorsal muscle (105.0–122.3 N). The elasticity of the anterior muscle (1.80–1.94 mm) was higher than that of the middle (1.60–1.62 mm) and posterior muscle (1.67–1.68 mm). The shear force of the posterior dorsal (24.2 N), ventral (24.1–24.4 N) and tail (23.4–28.3 N) muscle were lower indicating better tenderness. This is mainly related to the characteristics of muscle fibers in different body parts of fish. Taken collectively, sashimi of the ventral axial and ventral posterior muscle had better meat quality. This study will provide a theoretical basis for the utilization of muscles in different parts of giant hybrid sturgeon.
Dual-Target Antibacterial Mechanism of Phenyllactic Acid against Pseudomonas fluorescens Based on Cell Membrane and DNA Damage
NING Yawei, HOU Linlin, LI Mingrui, YANG Zheng, MA Mengge, WANG Zhixin, WANG Shijie, JIA Yingmin
2021, 42(7):  60-67.  doi:10.7506/spkx1002-6630-20200406-072
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Pseudomonas fluorescens is one of the most common psychrophilic bacteria causing spoilage of refrigerated foods. Inhibiting the growth and reproduction of P. fluorescens is of great significance for extending the shelf life of refrigerated foods and improving food safety. In this study, the antibacterial activity of phenyllactic acid (PLA) against P. fluorescens was evaluated by determining the minimum inhibitory concentration (MIC) and time-inhibition curve. The inhibitory mechanism was explored from different perspectives: membrane potential, membrane permeability and integrity, cell ultrastructure, protein expression and DNA structure. The results showed that the MIC of PLA was 1.25 mg/mL. PLA could depolarize the cell membrane in a dose-dependent manner, and cause significant leakage of intracellular potassium ion (P < 0.05), indicating increased permeability of the cell membrane. After treatment for 0.5 h by PLA at MIC concentration, the propidium iodide staining rate of cells was 57.6% as determined by flow cytometry, and ruptured cells were observed by scanning electron microscopy (SEM), suggesting that PLA could damage the membrane integrity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that PLA had no significant effect on protein expression. Gel retardation electrophoresis and fluorescence spectroscopy showed that PLA could destroy the structure of DNA. Therefore, PLA can exert a bacteriostatic effect by destroying both the cell membrane and DNA, which will provide theoretical evidence for the control of psychrophilic spoilage bacteria in refrigerated foods and the application of PLA in foods.
Effect of Heat Treatment on the Stability of Hemp Seed Milk and Characterization of Protein Structure
ZHU Xiuqing, WANG Ziyue, LI Meiying, WANG Yuan, LI Zhimin, YANG Hongzhe, ZHANG Na, SUN Bingyu
2021, 42(7):  68-73.  doi:10.7506/spkx1002-6630-20200213-129
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The purpose of this study was to investigate the effect of heat treatment on the stability and protein structure of hemp seed milk. The stability was monitored by the nitrogen solubility index (NSI), centrifugal precipitation rate, emulsification characteristics, emulsion surface potential and particle size. Fourier transform infrared (FTIR) spectroscopy was used to characterize the secondary structure of hemp seed milk proteins. The results showed that with the increase in heat treatment temperature (55–95 ℃), the NSI decreased from 58.55% to 39.81%, the centrifugal precipitation rate increased from 16.58% to 34%, and the average particle size increased from 192.2 nm to 304.6 nm. The results of FTIR analysis showed that the secondary structures of hemp seed milk proteins changed with the increase in heat treatment temperature. The relative content of α-helix decreased from 28.57% to 23.70%, while the relative content of random coil increased from 21.13% to 25.41%. The maximum absolute value of zeta potential of 20.57 mV was observed when hemp seed milk was treated at 65 ℃, accompanied by the best stability and the highest emulsification activity and emulsification stability with emulsifying activity index (EAI) of 0.357 m2/g and emulsion stability index (ESI) of 43.74%. This study will provide a theoretical basis for the processing and application of hemp seed milk.
Determination and Correlation Analysis of Functional Components and Antioxidant Activity of Successive Solvent Extracts from Macadamia Green Husk
GUO Gangjun, HU Xiaojing, FU Jiarong, MA Shangxuan, XU Rong, HUANG Kechang, PENG Zhidong, HE Xiyong, ZOU Jianyun
2021, 42(7):  74-82.  doi:10.7506/spkx1002-6630-20200310-154
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The contents of total phenols, total flavonoids and polysaccharides and the in vitro antioxidant activities of petroleum ether (PE), chloroform (CE), ethyl acetate (EAE), n-butanol (NBE) and water soluble extracts obtained from successive fractionation of the 80% ethanol extract (EE) of macadamia green husk were evaluated and the correlation between the bioactive components and the antioxidant activities was analyzed. The results showed that the contents of total phenols and flavonoids in EAE were the highest among all samples, (40.36 ± 0.48)% and (41.68 ± 0.93)%, respectively, and the content of polysaccharides in NBE was the highest, (22.08 ± 2.09)%. EE and fractions thereof all had strong scavenging capacity against 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cation radicals and reducing power, and also had certain scavenging capacity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and superoxide anion radicals. EAE had?the strongest scavenging capacity against DPPH and ABTS cation radicals and the highest reducing power with half maximal inhibitory concentration (IC50) of 0.67, 0.05 and 0.09 mg/mL, respectively. NBE had the strongest scavenging capacity against superoxide anion radicals with IC50 of 0.08 mg/mL, which was better than rutin at the same concentration. Pearson correlation analysis showed that for all samples, the scavenging effect on DPPH and ABTS cation radicals and reducing power were significantly positively correlated with the contents of total phenols, flavonoids and polysaccharides (P < 0.01), and the scavenging effect on superoxide anion radicals was significantly positively correlated with the content of polysaccharides (P < 0.01). The linear regression equations?between antioxidant properties and the contents of total phenols (X1), flavonoids (X2), polysaccharides (X3) and Saponins and other components (X4) were established as follows: Y1 = 7.634 4 ? 0.071 0X1 + 0.170 2X2 + 0.227 6X3 ? 0.013 3X4 for DPPH scavenging capacity, Y2 = 29.024 5 ? 0.405 0X1 + 0.320 0X2 + 0.597 2X3 for superoxide anion radical scavenging capacity, Y3 = 40.305 6 + 0.188 8X1 + 0.030 4X4 for ABTS cation radical scavenging capacity, and Y4 = 0.298 2 + 0.004 5X2 + 0.006 0X3 for reducing power, respectively. Conclusion: This study provides a certain technical basis for the development and utilization of macadamia green husk.
Effect of Feeding Regimens on Muscle Fiber Type Composition and Meat Quality of Sunit Sheep and Underlying Regulatory Mechanism
HOU Yanru, SU Lin, HOU Puxin, BAI Yanping, SUN Bing, ZHAO Lihua, HUANG Kaibiao, LÜ Ke, JIN Ye
2021, 42(7):  83-89.  doi:10.7506/spkx1002-6630-20200321-312
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The effects of feeding regimens (pasture and confinement) on meat quality, muscle fiber type composition and key factors regulating muscle fiber type in the Longissimus dorsi muscle of Sunit sheep were investigated. The results showed that carcass mass (P < 0.05),L* value (P < 0.05), Warner-Bratzler shear force (WBSF) (P < 0.05), pH24 (P < 0.01), the number and area proportion of type IIB muscle fiber (P < 0.01), the diameter of type I, IIA and IIB (P < 0.01), the cross-sectional area of type I (P < 0.05), IIA (P < 0.01) and IIB (P < 0.01), and lactic dehydrogenase (LDH) activity (P < 0.01) in the pasture group were significantly lower than those in the confinement group. However, the number and area proportion of type IIA muscle fiber (P < 0.01), the mRNA expression of the MyHC I and MyHC IIX genes (P < 0.01), the activity of malate dehydrogenase (MDH) and succinate dehydrogenase (SDH) (P < 0.05), and the mRNA expression of the AMPKα2 and COX IV genes (P < 0.05 or 0.01) were significantly higher in the pasture group than those in the confinement group. The mRNA expression of the PGC-1α gene was no significantly different between the two groups (P > 0.05). Overall, the present study indicated that compared to confinement feeding, pasture feeding could augment the relative mRNA expression level of AMPKα2 in the muscle and activate cytochrome c oxidase IV (COX IV) in the mitochondrial inner membrane, thus promoting mitochondrial biogenesis, enhancing oxidative metabolism, inducing the transition of muscle fiber types from glycolyzed to oxidized types, and finally improving meat quality.
Dynamic Analysis of Organic Acids in a Mixture of Vegetable and Fruit Juices during Fermentation and Changes in Antioxidant Activity and Functional Constituents during Simulated Gastrointestinal Digestion
CHEN Shujun, ZHENG Jie
2021, 42(7):  90-97.  doi:10.7506/spkx1002-6630-20200511-112
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Mixed vegetable and fruit juices fermented and not fermented with either mixed lactic acid bacteria (Lactobacillus plantarum and Lactobacillus casei) or kefir grains were evaluated for changes in the contents of polyphenols and flavonoids, and scavenging capacities against 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cation and hydroxyl radicals after simulated gastrointestinal digestion, and changes in the types and contents of organic acids in the mixed fruit and vegetable juice during fermentation were analyzed by high performance liquid chromatography (HPLC). The results showed that during the simulated digestion process, the contents of polyphenols and flavonoids in the fermented sample increased significantly compared with the unfermented sample (P < 0.05). The radical scavenging capacity of the fermented and unfermented samples increased after digestion, especially simulated gastric digestion. At the end of digestion, the scavenging capacity against DPPH, ·OH and ABTS cation radicals of the kefir grains-fermented sample increased by 10.1%, 13.3% and 6.5% as compared to the lactic acid bacteria fermented sample, and by 12.8%, 14.7% and 16.7% as compared to the unfermented sample, respectively. The contents of polyphenols and flavonoids increased by 1.07 and 0.016 mg/mL as compared to the lactic acid bacteria fermented sample, and by 3.16 and 0.022 mg/mL as compared to the unfermented sample, respectively. The changing trends in organic acids throughout the entire fermentation process were consistent between the two fermented samples. The contents of malic acid, succinic acid and oxalic acid significantly decreased after fermentation (P < 0.01), while the contents of lactic acid, tartaric acid and acetic acid significantly increased (P < 0.01). On the other hand, the content of citric acid did not significantly change (P > 0.05). The results of this study provide a theoretical rationale for developing new lactic acid bacteria starter cultures.
Effects of Different Extraction Methods on the Structure, Physicochemical and Functional Properties of Water-Soluble Dietary Fiber from Cherry Wine Dregs
ZHANG Qiyue, ZHANG Shikai, XI Liangqing, DU Haiyun, WU Peng
2021, 42(7):  98-105.  doi:10.7506/spkx1002-6630-20200518-207
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The effects of enzymatic extraction (cellulase) and acidic extraction (citric acid) on the structural, physicochemical and functional properties of water-soluble dietary fiber (SDF) from cherry wine dregs were compared in this paper. Scanning electron microscopic (SEM) observation, Fourier transform infrared spectroscopy (FTIR), monosaccharide composition analysis, rheological measurement, adsorption capacity characterization, and in vitro antioxidant activity evaluation were carried out the SDFs extracted by the two methods. SEM analysis showed that the surface of the enzyme-extracted SDF was loose and porous, whereas the surface of the acid-extracted SDF was smooth. There were slight differences in the absorption intensity and functional group types of the two SDFs, and they displayed the typical absorption peaks of carbohydrates. The monosaccharide composition was identical between the SDFs, while the monosaccharide content of the enzyme-extracted SDF was 58.7% higher than that of the acid-extracted SDF. Rheological experiments showed that both SDFs were pseudoplastic non-Newtonian fluids, and the apparent viscosity increased with increasing their concentration, but decreased with increasing shear force. The SDFs had strong adsorption capacity toward nitrite at pH 2 and toward cholesterol at pH 7, and the enzyme-extracted SDF was more effective than the acid-extracted one. Both had in vitro antioxidant properties, with the enzyme-extracted SDF exhibiting stronger scavenging capacity against 1,1-diphenyl-2-picrylhydrazyl radical and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) cation radical and total antioxidant capacity. In conclusion, the different extraction methods had a great influence on the structural, physicochemical and functional properties of SDF from cherry wine dregs. The properties of the enzyme-extracted SDF were superior to those of the acid-extracted SDF. This study will provide a reference for improving the utilization rate of cherry wine dregs and further exploring its nutritional value.
Food Engineering
Effects of Casein Types and Secondary Homogenization on Whipping Properties of Recombined Cream
LI Yang, LI Yan, WANG Yunna, YUAN Dongdong, ZHANG Liebing
2021, 42(7):  106-112.  doi:10.7506/spkx1002-6630-20200302-027
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This study aimed to evaluate the effect of three common casein products, micellar casein concentrate (MCC), calcium caseinate (CaC) and sodium caseinate (NaC), as well as secondary homogenization on the whipping properties of recombined cream. The results showed that the whipping properties were related to both the concentrations of caseins and secondary homogenization. The creams with MCC or CaC at concentrations of 1.5% and 2.5% exhibited excellent whipping properties, with maximum foaming rate and leakage rate in the range of 170%–200% and 0–1.5%, respectively, which were little influenced by secondary homogenization. However, a low concentration (0.5%) of NaC gave good whipping properties with maximum foaming rate of (198.2 ± 4.0)%, which decreased to (119.0 ± 15.4)% when NaC concentration was increased to 1.5%. Moreover, secondary homogenization reduced the maximum foaming rate and increased the leakage rate of the cream with NaC. In conclusion, regardless of whether it underwent secondary homogenization, the recombined cream with MCC or CaC had excellent whipping properties.
Preparation and Characterization of Sulforaphane Microcapsules by Electrospraying
WANG Xiao, MENG Guanli, WANG Qilei, WANG Langhong, FAN Daidi, LÜ Xingang
2021, 42(7):  113-119.  doi:10.7506/spkx1002-6630-20200404-043
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Sulforaphane (SF) was microencapsulated with different wall materials using electrospraying. By characterizing the surface morphology, intermolecular interactions, thermal behavior, in vitro release behavior, and storage stability at high temperatures of microcapsules, the microencapsulation efficiency of SF with food-grade polymers was studied in order to select the optimal wall material for encapsulating SF. The results showed that the average particle size of the prepared microcapsules was in the range of 427.80-1 857.04 nm, with spherical shape and smooth surface. Compared to chitosan, zein and gelatin were more effective in SF delivery with encapsulation efficiencies of (95.83 ± 2.37)% and (95.11 ± 2.82)%, respectively. Infrared spectroscopy confirmed successful microencapsulation of SF. Thermogravimetric analysis showed that the microcapsules had high thermal stability as substantial degradation occurred only at temperatures above 300 ℃. The final release rate of SF from the microcapsules in simulated gastrointestinal fluid and food matrices was between 80% and 90%, indicating good gastrointestinal dissolution and release performance. Besides, the heat resistance of SF was significantly improved after microencapsulation. This study will be useful for the development of SF delivery vectors in order to enhance its industrial applications.
Preparation and Structure Characterization of Lemon Seed Cellulose Nanofibrils Using Ionic Liquid-Assisted Ball Milling
ZHANG Huan, DAI Hongjie, CHEN Yuan, GAO Huanqiu, LIU Jiao, MA Liang, YU Yong, ZHANG Yuhao
2021, 42(7):  120-127.  doi:10.7506/spkx1002-6630-20200330-441
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In order to promote the high-value utilization of lemon processing by-products, an high-efficiency method for the preparation of lemon seed cellulose nanofibrils (LSCNF) was developed by mechanical ball milling with different concentrations (0–50%) of the ionic liquid 1-butyl-3-methylimidazole chloride ([BMIM]Cl) as a wet milling medium in this study. The morphology and structure of LSCNF were characterized by atomic force microscope (AFM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetry (TG). The results showed that the length of LSCNF was reduced, while the diameter was increased with the increase of [BMIM]Cl concentration. The LSCNF prepared with 50% [BMIM]Cl showed the smallest length but a large diameter (40–60 nm). The XRD and FTIR results showed that all obtained LSCNFs formed cellulose Iβ crystals, and the addition of [BMIM]Cl had a certain protective effect on the crystallinity of LSCNF. The TG results showed that the residual amount of LSCNF after ionic liquid-assisted ball milling was similar to lemon seed cellulose (LSC) at 500 ℃, and both of them were higher than that of LSCNF prepared by ball milling. The rheological results showed that LSCNF suspensions showed a non-Newtonian behavior, and the relative viscosity of LSCNF with longer length was higher at a constant shear rate. In summary, ionic liquid-assisted ball milling is a green and efficient method to prepare lemon seed cellulose nanofibrils with controllable morphology and structure depending on the concentration of ionic liquids.
Effect of Ultrasound on Freezing Characteristics of Fruits with Different Porosities
CAO Xuehui, WANG Zhenni, BAI Ge, ZHU Danshi, LÜ Changxin
2021, 42(7):  128-133.  doi:10.7506/spkx1002-6630-20200327-394
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In order to study the effect of ultrasonic on the freezing characteristics of fruits with different porosities, apple, pear, and Hami melon (Cucumis melo var. saccharinus) were allowed to undergo ultrasonic-assisted immersion freezing at the same ultrasonic frequency and different ultrasonic intensities. A temperature recorder was used to measure temperature changes at different freezing time points during the freezing process. The drip loss, texture characteristics, color difference, moisture distribution, and ascorbic acid content of frozen-thawed samples were determined. The results showed that at an ultrasonic intensity of 0.145 W/cm2, the phase-changing times of apple, pear and Hami melon samples were 21.67, 21.33, and 16.67 s, respectively, which were significantly shorter than those of immersion frozen samples (P < 0.05). For each ultrasonic intensity, ultrasonic-assisted immersion freezing led to a decrease in drip loss during thawing compared to direct immersion freezing for all three fruits, especially for apple, which showed a significant decrease due to its low porosity (P < 0.05). Moreover, the hardness of the fruits was increased. Compared with the fresh samples, ascorbic acid contents in the treated samples were decreased significantly (P < 0.05). Compared with the samples without ultrasonic treatment, the fruit samples with smaller porosity maintained better quality under ultrasonic treatment.
Effect of Ultrasound-Assisted Alkali Treatment on Structural and Emulsifying Properties of Soybean Protein Isolate and on Its Interaction with (−)-Epigallocatechin Gallate
YAN Shizhang, XU Jingwen, WU Lichun, SUN Yufan, QI Baokun, LI Yang
2021, 42(7):  134-141.  doi:10.7506/spkx1002-6630-20200319-288
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In order to improve the emulsifying properties of soybean protein isolate (SPI) and prevent oxidative degradation of (?)-epigallocatechin gallate (EGCG), the effect of individual and combined alkali and ultrasonic treatments on the structural and emulsifying properties of SPI and its interaction with EGCG was investigated. Fourier transform infrared spectroscopy and fluorescence spectroscopy showed that both individual treatments could promote the unfolding of protein structure, decrease the α-helix relative content in the secondary structure of the protein (P < 0.05) and increase the random coil relative content (P < 0.05). Compared with the control group, the combined treatment group showed a decrease in the α-helix relative content of 13.23% and an increase in the random coil relative content of 8.44%, resulting in the exposure of more hydrophobic amino acid residues. Both alkali and ultrasonic treatments significantly increased the surface hydrophobicity, sulfhydryl content, emulsifying activity and emulsion stability of SPI (P < 0.05), and a better effect was observed when they were combined. Fluorescence quenching analysis revealed that the treated SPI had a stronger binding affinity to EGCG, blocking the degradation of EGCG. Besides, the treated SPI could protect EGCG from being oxidized with the combined treatment being more effective than either treatment alone. Together, this study confirmed that a combination of ultrasonic and alkali treatment can improve the emulsifying properties of SPI, making it a potential protective carrier for functional substances.
Nutrition & Hygiene
Hypolipidemic Activity of Polysaccharides Purified from Bangia fusco-purpurea
ZHAN Hui, SONG Tianyuan, YU Gang, JIANG Zedong, DU Xiping, ZHU Yanbing, NI Hui, LI Qingbiao
2021, 42(7):  142-148.  doi:10.7506/spkx1002-6630-20200302-024
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Objective: To evaluate the in vitro hypolipidemic activity of three sulfated polysaccharide fractions purified from the edible red alga Bangia fusco-purpurea for the purpose of providing a scientific basis for deep processing and high-valued utilization of Bangia fusco-purpurea. Methods: The crude polysaccharide was prepared by hot water extraction followed by 75% ethanol precipitation, deproteinized with the Savage method, purified by Sephadex G75 column chromatography, and fractionated by DEAE-cellulose 52 column chromatography into three fractions (F1, F2 and F3). The inhibitory effects of the polysaccharides on pancreatic lipase were analyzed, and the effect on the viability of Caco-2 and HepG2 cells was measured by the MTT assay. The in vitro hypolipidemic potentials were evaluated using HepG2 cell model and Caco-2 cell model. Results: F3 significantly inhibited pancreatic lipase activity in a competitive and reversible manner. All three fractions showed no significant cytotoxicity at tested concentrations (0–500 mg/mL). Interestingly, F1 significantly inhibited the absorption of free fatty acids by Caco-2 cells, whereas F3 exhibited potent inhibitory effects on triglyceride synthesis in the hyperlipidemic HepG2 cell model and lipid synthesis in the high cholesterol HepG2 cell model. Conclusion: The polysaccharides from B. fusco-purpurea can effectively inhibit pancreatic lipase activity, and obviously suppress the absorption of free fatty acids by cells and the synthesis of cholesterol and triglycerides in cells, thereby exhibiting hypolipidemic potentials.
Effects of Dietary Supplementation with Creatine Monohydrate and Conjugated Linoleic Acid on Muscle Fiber-Related Gene Expression and Enzyme Activities in Mice
SU Lin, LI Huijiao, HOU Yanru, ZHAO Yajuan, BAI Yanping, SUN Bing, ZHAO Lihua, JIN Ye
2021, 42(7):  149-155.  doi:10.7506/spkx1002-6630-20200915-183
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The aim of this study was to investigate the effects and underlying mechanisms of dietary supplementation with creatine monohydrate (CMH) and conjugated linoleic acid (CLA) on muscle fiber-related gene expression and enzyme activities in rats. Totally 40 healthy female Wistar rats were randomly divided into five groups coded A to E. Group A was fed a basic diet as the control group, group B the basic diet supplemented with 0.5% CMH, group C the basic diet supplemented with 1% CMH, group D the basic diet supplemented with 0.5% CLA , and group E the basic diet supplemented with 1% CLA. The feeding period lasted for four weeks. Compared to group A, group B showed a significant decrease in daily feed intake (P < 0.05), and a significant increase in the mRNA expression of myosin heavy chain IIa (MyHC IIa) and MyHC IIb, peroxisome-activated receptor coactivator 1α (PGC-1α), myocyte enhancer factor 2C (MEF2C), glucose transporter 4 (GLUT4), and succinate dehydrogenase (SDH) activity (P < 0.05); group C presented a significant decrease in daily feed intake (P < 0.05), and a significant increase in the mRNA expression of MyHC IIb, MEF2C and GLUT4 (P < 0.05). Compared to group A, group D showed a significant decrease daily feed intake and the mRNA expression of MyHC IIx (P < 0.05), and a significant increase in the mRNA expression of MyHC IIa and PGC-1α, and the activity of SDH, malate dehydrogenase, adenosine 5’-monophosphate-activated protein kinase (AMPK) (P < 0.05); group E exhibited a significant decrease in daily feed intake, lactic dehydrogenase (LDH) activity and the mRNA expression of MEF2C (P < 0.05), and a significant increase in the mRNA expression of MyHC I, MyHC IIa, PGC-1α and GLUT4, as well as SDH activity (P < 0.05). In summary, dietary supplementation with CMH or CLA activated AMPK in the muscle tissue of rats and increased the oxidative metabolism-related enzyme activities, up-regulated the mRNA expression of the muscle fiber-related genes PGC-1α, MEF2C and GLUT4, and enhanced the energy required for oxidative metabolism in muscle, thereby altering muscle fiber types.
Improvement Effect of Mulberry Leaf Alkaloids on Abnormal Glucose and Lipid Metabolism and Liver Injury Induced by Oxidative Stress in Mice
YANG Zhongmin, SHEN Yihong, HUANG Xianzhi, WANG Zuwen, DING Xiaowen
2021, 42(7):  156-161.  doi:10.7506/spkx1002-6630-20200302-032
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Objective: To explore whether mulberry leaf alkaloids can improve abnormal glucose and lipid metabolism and liver injury induced by oxidative stress in mice for the purpose of provide a theoretical basis for the scientific utilization of mulberry leaves. Methods: A mouse model of oxidative injury was generated by intraperitoneal injection of D-galactose at a dose of 1 000 mg/kg mb for 20 days. Following successful model establishment, the mice were randomly divided into five groups, including model, positive control (200 mg/kg mb of glutathione) and low-, medium- and high-dose mulberry leaf alkaloids (50, 100, and 200 mg/kg mb) groups. The changes of fasting blood glucose, lipid level and liver injury indicators were measured at 0, 4, 8 and 12 weeks of gavage. Results: Compared with the model group, fasting blood glucose, plasma total cholesterol (TC) and triglycerides (TG), and the activities of liver alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were significantly decreased in the positive control group and the medium- and high-dose mulberry leaf alkaloids groups (P < 0.05). Meanwhile, there was no significant difference in all these parameters between the high-dose mulberry leaf alkaloids group and the positive control group, and both treatments restored them to normal, demonstrating that mulberry leaf alkaloids can improve abnormal glucose and lipid metabolism and liver injury in a dose but not time-dependent manner. Histopathological observation showed that the degree of liver lesions in the positive control group and the mulberry alkaloids groups was significantly reduced. Conclusion: Mulberry leaf alkaloids can improve abnormal glucose and lipid metabolism and liver damage caused by oxidative stress, and the underlying mechanism may be related to inhibiting the occurrence and development of oxidative stress.
Preparation of Ginsenoside Rh2-Loaded Chitosan Nanoparticles and Its Cytotoxicity to A549 Cells
GU Qian, ZHOU Jing, ZHANG Jianmei, SHANG Zhi, SHEN Ting, YANG Xiaojun, HU Weicheng
2021, 42(7):  162-168.  doi:10.7506/spkx1002-6630-20200311-175
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In this study, chitosan nanoparticles prepared by ionic cross-linking was considered as a new vehicle for the improvement of the water solubility and biocompatiblity of ginsenoside Rh2. Based on the size and zeta potential of nanoparticles, the conditions for preparing ginsenoside Rh2-loaded nanoparticles were optimized with respect to mass ratio between chitosan and sodium tripolyphosphate, the molecular mass of chitosan and the feeding amount of Rh2. The morphology of Rh2-loaded nanoparticles was observed transmission electron microscopy and atomic force microscopy. The change of crystal types was investigated by X-ray diffraction. The anti-proliferation effect of Rh2-loaded nanoparticles on non-small cell lung cancer cells (A549) and the cellular uptake of Rh2 were studied. Under the optimal conditions as follows: mass ratio of chitosan to Rh2 to sodium tripolyphosphate 8:1.5:2 and chitosan molecular mass 50 kDa, Rh2-loaded nanoparticles whose average particle size and zeta potential were (222.70 ± 17.34) nm and (46.50 ± 2.57) mV, respectively were obtained with encapsulation and loading efficiencies of 7.89% and 49.54%, respectively. The as-prepared nanoparticles showed uniform size distribution and good stability, therefore being suitable for drug delivery. It could be uptaken by A549 cells and have higher inhibitory effect on the proliferation of A549 cells compared with free ginsenoside Rh2. Therefore, the chitosan nanoparticles prepared by ionic cross-linking are a promising carrier for the delivery of ginsenoside Rh2.
Preparation, Structural Characterization and Probiotics Proliferation-Promoting Activity of Selenized Dandelion Polysaccharide
WANG Libo, GAO Jingyu, LI Tengfei, LI Lianyu, LIU Bo, ZHANG Hongyan, YANG Yu, XU Yaqin
2021, 42(7):  169-175.  doi:10.7506/spkx1002-6630-20200506-043
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In this study, a selenized polysaccharide from dandelion roots (Se-DRP) was prepared by HNO3-Na2SeO3 method. The physicochemical properties, structural characteristics, probiotics proliferation-promoting activity of Se-DRP and its inhibitory effect on α-amylase were investigated. The results showed that Se-DRP was a heteropolysaccharide with a molecular mass of 8 102 Da, and it was composed of galacturonic acid, rhamnose, arabinose, mannose, glucose and galactose with a molar ratio of 0.64:0.73:19.36:0.84:1.00:27.41. Nuclear magnetic resonance (NMR) analysis showed that the major sugar residues in Se-DRP were →6)-β-D-glucose-(1→, →5)-α-L-arabinose-(1→, →3)-β-D-galactose-(1→ and →4)-α-D-galacturonic acid-(1→. Se-DRP possessed probiotics proliferation-promoting activity and could be utilized by Lactobacillus plantarum 10665 and Lactobacillus acidophilus as a carbon source. In addition, Se-DRP exhibited α-amylase inhibitory activity with an inhibitory rate of (52.34 ± 1.45)% at a concentration of 4.0 mg/mL. These results provide a theoretical basis for further studies of Se-DRP and the utilization of dandelion resources.
Effects of n-3 Polyunsaturated Fatty Acids on the Regulation of miRNA in Blood Exosomes and Its Antiobesity Effect in Mice
WU Cong, GE Keli, LU Zongbo, ZHENG Zheng, ZHANG Jinyu, XUE Meilan, GE Yinlin
2021, 42(7):  176-184.  doi:10.7506/spkx1002-6630-20200411-149
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Objective: To investigate the effects of increasing n-3 polyunsaturated fatty acids (n-3 PUFAs) on the body mass and the expression of exosomal miRNAs in the blood of mice, and to explore the antiobesity mechanism of n-3 through the exosomes. Methods: fat-1 transgenic mice were fed a high-fat diet (HFD) to create an obese animal model and the wild-type littermates served as the control group. The body masses of mice were measured, and exosomes from the plasma of mice were extracted and identified. RNA was isolated from the exosomes for high-throughput sequencing of miRNAs and construction of a library. According to the sequencing results, the target genes and related signaling pathways were explored by bioinformatics analysis, and the relationship between miRNAs and their target genes was also elucidated. Finally, the association of miRNAs with obesity and its roles in obesity were validated. Results: The body mass of fat-1 transgenic mice was significantly lower than that of their wild-type counterparts. The exosomes were successfully extracted and identified. High-throughput sequencing showed 46 significantly differentially expressed miRNAs (P < 0.05) with fold change (FC) value ≠ 1. Bioinformatics analysis revealed that six important miRNAs (mmu-miR-665-3p, mmu-miR-122-5p, mmu-miR-122-3p, mmu-miR-194-5p, mmu-miR-34c-5p, and mmu-miR-223-3p) were confirmed to play critical roles in fatty acid metabolism and endocytosis pathways, exerting functions related to lipid metabolism and obesity. Their target genes were Fads1, Elovl2, Elov6, Hadha, Scad1, Scad2, Hsd17b12, Acot2 and Acot4; and Arf6, H2-T-ps, Arrb1, Ist1, H2-T10, Wwp1, Snx4, IL2rb, Mvb12b, Rab11, fip3, Kif5a and Nedd4l in the two pathways, respectively. Conclusion: Increasing n-3 PUFAs can reduce body mass and alleviate obesity in mice. In addition, n-3 PUFAs can regulate the expression of miRNAs in blood exosomes; the significantly differentially expressed miRNAs are related to obesity, and their target genes are mainly involved in fatty acid metabolism pathways, suggesting that n-3 PUFAs may be involved in the molecular mechanism for inhibiting obesity.
Effect of Black Garlic on Inflammation in BALB/c Mice with Ulcerative Colitis
CUI Xiaoyu, ZHENG Hongying, QI Zhanwen, LIN Changqing, WU Xiaotian, GUO Jianpeng
2021, 42(7):  185-190.  doi:10.7506/spkx1002-6630-20200824-309
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Objective: To study the effect of black garlic on inflammatory response in BALB/c mice with ulcerative colitis (UC) induced by dextran sulfate sodium (DSS). Methods: The animal model was established by allowing them to have free access to 4% DSS. Afterwards, the mice were gavaged with a water extract of black garlic at different doses. The changes in the body mass of mice were determined as well as disease activity index (DAI) and histological score, and hematoxylin-eosin staining was used to evaluate the pathological changes in the colon. The serum concentrations of tumor necrosis factor α (TNF-α), interleukin 6 (IL-6), and interleukin 1β (IL-1β) were determined by enzyme-linked immunosorbent assay. Meanwhile, TNF-α expression in the colon was evaluated by Western blot. Results: black garlic at all three doses alleviated the loss of body mass induced by DSS in mice. Compared with the model control group, black garlic at the high and low doses significantly decreased DAI (P < 0.05) and the histopathological score and the levels of IL-6, IL-1β and TNF-α in mice in the high and medium dose black garlic groups were significantly lower (P < 0.01). Conclusion: Black garlic can attenuate the inflammatory reaction in BALB/c mice with UC.
Protective Effect of Walnut Oligopeptides against Gastric Mucosal Injury of Rats
LIU Rui, ZHU Na, HAO Yuntao, LIU Xinran, KANG Jiawei, MAO Ruixue, HU Jiani, YU Xiaochen, LI Zhen, LI Yong
2021, 42(7):  191-197.  doi:10.7506/spkx1002-6630-20200329-426
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The study investigated the protective effect of walnut oligopeptides (WOPs) against absolute ethanol-induced gastric injury, and it also explored the possible underlying mechanism. Male Sprague Dawley (SD) rats were randomly divided into eight groups based on body mas (n = 10), including normal, model, whey protein (440 mg/kg mb), omeprazole (20 mg/kg mb), low-, medium- and high-dose WOP (220, 440, 880 mg/kg mb, respectively) and WOPs (440 mg/kg mb) + bovine collagen oligopeptides (BCOPs, 1.5 g/kg mb) groups. After oral gavage for 30 days, the rats were administered with 5 mL/kg mb of absolute ethanol to induce gastric ulcer, then the gross lesion of gastric tissue was observed and scored, and the levels of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and gastric mucin (MUC), pepsinogen (PG) and gastrin (GAS) were detected. The results showed that administration with WOPs markedly mitigated the hemorrhagic gastric lesions caused by ethanol in rats, inhibited the increase in serum ALT and AST levels and gastric PGI, PGII and GAS levels, and enhanced MUC biosynthesis. These results indicated that WOPs have obvious protective effects against ethanol-induced gastric mucosal injury in rats mainly by attenuating the gastric mucosal damage directly caused by ethanol, inhibiting the biosynthesis of PG and GAS, and enhancing MUC biosynthesis.
Regulatory Effect of Cinnamon Essential Oil on Antioxidant Capacity of Liver and Intestine Tissues and Gut Microbiota in Mice
XIAO Ying, XU Haojie, YANG Changming, SONG Xiaoqiu, ZHOU Xiaoli
2021, 42(7):  198-206.  doi:10.7506/spkx1002-6630-20200322-330
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Objective: To explore the effect of cinnamon oil on the enzyme activities involved in hepatic metabolism, the antioxidant capacity of liver, duodenum and colon tissues, and the intestinal flora in mice, and to evaluate the potential health benefits of consumption of cinnamon oil. Methods: Eight-week-old male C57 mice were randomly divided into three groups: control, low-dose (100 mg/(kg·d)) and high-dose (300 mg/(kg·d)) cinnamon oil groups. After 4 weeks of feeding, the body mass, the enzyme activities involved in liver metabolism and the antioxidant capacity of liver, duodenum and colon tissues were measured. Illumina high-throughput sequencing was used to measure the change in gut microbiota at the levels of phylum and genus, and gas chromatography-mass spectrometry was used to detect the change in the contents of short chain fatty acids (SCFAs) in the feces of mice. The results showed that consumption of cinnamon oil significantly reduced the abdominal fat index, and increased the liver alanine aminotransferase activity and the antioxidant capacity of intestinal tissue (P < 0.05). At the level of phylum, the relative abundance of Tenericutes in mouse feces was decreased significantly after consumption of cinnamon oil (P < 0.05). At the level of genus, the relative abundance of conditional pathogens such as Blautia and [Eubacterium]_fissicatena_group was decreased significantly (P < 0.05), while the relative abundance of probiotics such as Roseburia and Coprobacillus was increased significantly (P < 0.05). The contents of fecal acetic acid, propionic acid and total acid were decreased significantly in the high-dose cinnamon oil group (P < 0.05). These results showed that consumption of cinnamon oil could regulate redox balance and the structure of intestinal flora by inhibiting pathogenic bacteria and promoting the proliferation of beneficial bacteria, thus exerting potential health benefits.
Packaging & Storage
Changes in Functional Properties of Myofibrillar Proteins in Three Species of Squid during Frozen Storage
YAO Hui, QI Xue’er, MAO Junlong, QI He, WU Tianxin, ZHANG Bin
2021, 42(7):  207-213.  doi:10.7506/spkx1002-6630-20200521-246
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Changes in the functional properties of myofibrillar proteins in Illex argentinus, Ommastrephes bartrami and Dosidicus gigas were investigated during frozen storage. The squid samples were frozen in a ?18 ℃ refrigerator and were taken at days 0, 15, 30, 45, 60, 75, 90, 105 and 120 to determine the content, solubility and turbidity, emulsifying capacity, Ca2+-ATPase activity, foaming capacity and foam stability, carbonyl content and total sulfhydryl content of myofibrillar protein. Results demonstrated that after 120 days of frozen storage, the turbidity and carbonyl content of myofibrillar proteins in all squid species increased significantly than that 0 day storage. The turbidity increased to 1.303, 0.608 and 1.177, respectively, and the carbonyl content increased by 8.74, 13.95 and 4.79 nmol/mg (P < 0.05). Myofibrillar protein content, solubility, foamability, foam stability, emulsification activity index (EAI), emulsification stability index (ESI), Ca2+-ATPase activity, and total sulfhydryl content decreased significantly. In Illex argentines, myofibrillar protein content, solubility, Ca2+-ATPase activity, and total sulfhydryl content decreased by 72.22%, 69.68%, 93.07% and 76.66%, respectively after 120 days of frozen storage. Moreover, the emulsification activity index (EAI) of myofibrillar proteins in Illex argentinus, Ommastrephes bartrami and Dosidicus gigas decreased by 10.09, 15.48 and 11.63 m2/g, respectively (P < 0.05), and the declining trend in ESI was basically consistent with that in EAI. The foaming capacity and foam stability of myofibrillar proteins in Ommastrephes bartrami decreased by 60.00% and 8.89%, respectively after 120 days of frozen storage, and the declining rates were significantly higher than those of Illex argentinus and Dosidicus gigas. Therefore, the physicochemical properties of myofibrillar proteins in the three squid species showed similar changing trends during frozen storage in spite of the differences in the declining rate and extent.
Anabolic and Catabolic Flux Analysis of ‘Indian Green’ Apples and Optimization of Storage Temperature
YUAN Shuai, LU Dingqiang, PANG Guangchang
2021, 42(7):  214-219.  doi:10.7506/spkx1002-6630-20200310-170
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In this study, the anabolic and catabolic flux of ‘Indian Green’ apples were studied at different storage temperatures. Further, the storage temperature was optimized. The metabolic flux of the glycolytic pathway, trichloroacetic acid (TCA) cycle, sucrose synthesis pathway, and pentose phosphate pathway in different parts of the fruit were measured at storage temperatures of 0, 2, 5, 10, 15, 20, and 40 ℃. The results showed that sucrose had a higher anabolic flux at 2 ℃, with values of 32, 42, 47, and 33.00 for the four parts from the outside to the inside. Similarly, lactate also had a higher metabolic flux at 2 ℃, with values of 1.87, 1.86, 1.86, and 1.86 for the four parts from the outside to the inside. At this temperature, lower catabolism and higher sucrose anabolism were observed. Accordingly, 2 ℃ was the best storage temperature for ‘Indian Green’ apples. In this study, based on the changes in metabolic flux between various parts of ‘Indian Green’ apples at different storage temperatures, a quantitative model could be established to evaluate lactate and sucrose flux, which will provide a novel method and a theoretical reference for future studies to extend the storage life of fruits.
Effect of Chitosan Coating Incorporated with Food Preservatives on the Muscle Quality of Grass Carp during Cold Storage
LI Jiayi, CHEN Sai, LIU Yongle, YU Jian, LI Xianghong, HUANG Yiqun, WANG Faxiang
2021, 42(7):  220-225.  doi:10.7506/spkx1002-6630-20200403-035
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To explore an effective method to preserve the quality of grass carp during cold storage, the effect of chitosan coating incorporated with food preservatives on the flesh quality of grass carp was evaluated by determining quality changes in fish fillet samples treated with 10 mg/mL chitosan + 5 mg/mL tea polyphenols + 2 000 U/mL lysozyme and those treated with sterilize water (control) in terms of freshness (K-value), adenosine triphosphate (ATP)-related compounds content, juice loss rate, texture and volatile components during cold storage. The results showed that K-value, hypoxanthine, juice loss rate, adhesiveness and volatile components increased to different extents with increasing storage time, especially for the preservative-treated group. Inosinic acid and hardness values in the control group kept on declining with storage time, whereas those in the preservative-treated group initially rose and then dropped at a significantly lower rate than that observed for the control group. This study indicated that the chitosan coating incorporated with food preservatives could effectively maintain the flesh quality and delay the quality deterioration of grass carp.
Proteomics Studies on Myoglobin Content and Its Transformation into Derivatives in Muscle of Qinchuan Cattle during Postmortem Storage
ZHANG Xingya, YANG Bo, LI Yalei, LUO Ruiming, RUAN Zhentian, SA Miaomiao, ZHAO Junyi
2021, 42(7):  226-231.  doi:10.7506/spkx1002-6630-20200315-239
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In this paper, 4D-label-free proteomics (4D-LFQ) was used to explore changes in the content of myoglobin and its transformation into derivatives in the Longissimus dorsi muscle in Qinchuan cattle during the first eight days of postmortem storage. The results showed that during storage from day 0 to day 4, the expression of the myoglobin had an upward trend, but then decreased. Totally 14 differentially expressed proteins related to myoglobin and its derivatives were identified, including metabolic enzyme, oxidoreductase, peroxidase and chaperone protein, which could together regulate the change in myoglobin content and the transformation between myoglobin and its three derivatives. Specifically, myoglobin expression showed an overall downward trend, and the relative content of oxymyoglobin continuously declined, while the relative contents of deoxymyoglobin and metmyoglobin gradually rose, resulting in browning in meat color. The results of this study will be useful for understanding the complex biochemical mechanism underlying color changes in the meat of Qinchuan cattle during storage.
Fabrication and Characterization of Antimicrobial Food Packaging Materials Composed of Konjac Glucomannan, Chitosan and Fulvic Acid
CHEN Xiaohan, PANG Jie, WU Chunhua
2021, 42(7):  232-239.  doi:10.7506/spkx1002-6630-20200417-226
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A konjac glucomannan (KGM)/chitosan (CS) antimicrobial film was prepared by a sol-gel method using fulvic acid as the cross-linking agent. The physical, mechanical, structural and antimicrobial properties of the antimicrobial film was evaluated by rheology, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM). Results showed that the introduction of fulvic acid promoted the formation of hydrogen bonds and electrostatic interactions between the functional groups of KGM and those of CS, thereby improving the thermostability and optical properties of the antimicrobial film. Meanwhile, compared with KGM/CS antimicrobial films, the mechanical properties of KGM/CS antimicrobial films added with fulvic acid increased by 16.85 mPa. Water vapor permeability (WVP) of KGM/CS antimicrobial films was 8.65 g/(Pa·s·m) and KGM/CS antimicrobial films added with fulvic acid was 5.25 g/(Pa·s·m). More importantly, the film had good antimicrobial properties and thus could be applied in active food packaging to maintain the quality of foods.
Effects of Freeze-Thaw Cycles on Texture Properties and Protein Properties in Big-Eye Tuna (Thunnus obesus)
LAN Weiqing, SUN Yuqing, XIAO Lei, MEI Jun, XIE Jing
2021, 42(7):  240-246.  doi:10.7506/spkx1002-6630-20200316-254
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In order to explore the effects of freeze-thaw cycles on texture properties, microstructure and protein properties in big-eye tuna (Thunnus obesus), fish samples were subjected to 1-5 freeze-thaw cycles under conditions simulating temperature fluctuations encountered in a supermarket (F1) and those encountered in a household (F2). Changes in physicochemical indexes (thaw drip loss rate, metmyoglobin content, myofibrillar protein content, total sulfhydryl content and Ca2+-ATPase activity) and texture profile analysis (TPA) parameters were measured during freeze-thaw cycles. Quality changes were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI). The results showed that with increasing freeze-thaw cycles, thaw drip loss rate was increased in both groups, hardness, chewiness and springiness were significantly decreased (P < 0.05), and adhesiveness was increased; myofibrillar protein content, total sulfhydryl content and Ca2+-ATPase activity were decreased, and metmyoglobin content were increased. The thaw drip loss rate in group F1 was higher than that in group F2 at the same freeze-thaw cycles, which reached the maximum value after the fourth freeze-thaw cycle, accompanied by a significant decrease in hardness. A slower increase in metmyoglobin content, and slower decreases in myofibrillar protein content and Ca2+-ATPase activity in group F1 were observed compared with group F2. The results of SDS-PAGE showed that repeated freeze-thaw cycles caused partial protein degradation. The degradation rate was accelerated with increasing number of freeze-thaw cycles and freezing temperature. The results of LF-NMR revealed that repeated freeze-thaw cycles could result in the conversion of immobile water in fish myofibrils into free water. The relative content of free water as well as thaw drip loss rate in group F1 was increased with increasing freeze-thaw cycles, which was consistent with the results of MRI analysis. Accordingly, compared with F2, F1 was more effective in inhibiting the increase in metmyoglobin content and maintaining Ca2+-ATPase activity despite increasing thaw drip loss rate and deteriorating texture properties. Increase the number of freeze-thaw cycles could aggravate the deterioration of functional characteristics in fish tissues and proteins, leading us to conclude that the number of freeze-thaw cycles during circulation should be as small as possible.
Effect of Dihydromyricetin on Trimethylamine Oxide Degradation and Quality Attributes in Grilled Squid Fillets during Storage
LI Yingchang, LI Shuangyan, DU Fengxia, LIU Xuefei, WEI Ya, YANG Xianqing
2021, 42(7):  247-252.  doi:10.7506/spkx1002-6630-20200315-234
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In order to reduce the formaldehyde content in squid products and improve the storage quality of squid products, the effect of dihydromyricetin on trimethylamine oxide (TMAO) degradation and quality attributes in grilled squid fillets was studied. The experiment was divided into a control group and a dihydromyricetin group (0.2%). Squid products were stored at 25 ℃. Changes in the contents of TMAO, formaldehyde (FA), dimethylamine (DMA) and trimethylamine (TMA), color difference, thiobarbituric acid (TBA) value, texture, odor, and water mobility were explored during storage. The results showed that dihydromyricetin inhibited the loss of water during storage, and effectively delay the occurrence of browning reactions in grilled squid fillets, thereby inhibiting the color change. Dihydromyricetin decreased fat oxidation, increased the hardness and elasticity of the product, delayed the generation of unpleasant volatile odors, inhibited the degradation of TMAO and reduced the production of FA. Therefore, dihydromyricetin could maintain the storage quality of grilled squid fillets well and inhibit TMAO degradation.
Effect of Superchilled Storage on Water-holding Capacity of Beef Muscle
LU Xiao, DONG Pengcheng, ZHANG Yimin, MAO Yanwei, LIANG Rongrong, YANG Xiaoyin, ZHU Lixian, LUO Xin
2021, 42(7):  253-259.  doi:10.7506/spkx1002-6630-20200330-430
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From the perspectives of protein structure and water distribution, the mechanism of the change in the water-holding capacity (WHC) of beef muscle during superchilled (-4 ℃), chilled (2 ℃) and frozen (-18 ℃) storage were investigated in this study. Superchilled samples exhibited significantly higher juice loss and cooking loss than chilled and frozen counterparts (P < 0.05), indicating the poorest WHC among all samples. During superchilled storage, the relaxation time of water was gradually prolonged; the content of bound water remained stable, the content of immobilized water decreased, and the percentage of free water increased (P < 0.05). As the storage time increased, total and free sulphydryl contents significantly decreased, and protein surface hydrophobicity significantly increase for all storage conditions (P < 0.05). At lower storage temperature, the rate of change was slower. Superchilled storage did not induce severe proteolysis of myofibrillar proteins. The denaturation degree of proteins in superchilled samples was higher at the late stage of storage, thereby improving the fluidity of immobilized water located in the myofibrillar protein network. Partial immobilized water was transformed into free water, thus leading to lower WHC of superchilled beef muscle.
Reviews
Progress in Research on Microbial Inulosucrase and Its Applications in Foods
NI Dawei, XU Wei, ZHANG Wenli, MU Wanmeng
2021, 42(7):  260-266.  doi:10.7506/spkx1002-6630-20200308-128
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Inulin is a soluble dietary fiber that has been reported to show good physicochemical properties and significant physiological functions, enabling it to be applied widely in foods. Inulosucrase (ISase) can use sucrose as the sole substrate to synthesize high-molecular-mass microbial inulin in one step. Currently, 15 microbial ISases have been identified, and the crystal structure of one of them has been solved. There are few studies on Isase in China. This review comprehensively analyzes the crystal structure and catalytic mechanism of ISase. Special emphasis is put on discussing the modulation of inulin chain length and the applications of ISase in the production of inulin, oligosaccharides, novel oligosaccharides and inulin nanoparticles. Based on previous studies of ISase, future development trends are discussed.
Advances in Biological Activity and Functional Mechanism of Peptides from Lactoferrin
SHI Pujie, XU Shiqi, WANG Zhenyu, WU Chao, LU Weihong, DU Ming
2021, 42(7):  267-274.  doi:10.7506/spkx1002-6630-20200429-379
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Lactoferrin is an iron-binding natural glycoprotein, which is distributed widely in the milk of various mammalian species and most biological fluids. Ingested lactoferrin is mainly adsorbed as peptides by the human body after protease digestion to exert its physiological functions. In recent years, a great number of bioactive peptides with antimicrobial, antitumor, antihypertension, anti-inflammatory and immune modulator activities derived from lactoferrin hydrolysates have been reported. These peptides have dual functions of regulating the body’s physiological functions and providing nutrients for the body, thereby playing an important role in human health. In this review, the species, structures and mechanisms of action of functional peptides from lactoferrin are summarized and their applications in the field of food science are discussed to provide a theoretical basis for the research of these bioactive peptides and their applications in the functional food field.
Stability Mechanism of Pickering Emulsion and Its Application in Food Industry: A Review
WU Yuchun, CHEN Xiaocao, ZHANG Qi, DING Yuting, ZHOU Xuxia
2021, 42(7):  275-282.  doi:10.7506/spkx1002-6630-20200325-373
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Pickering emulsion is an emulsion system based on particle stability. Due to its excellent biocompatibility, Pickering emulsion holds great promise for application in the field of foods such as bioactive substance carriers and fat substitutes. The excellent emulsifying properties and stability of the particles are important for the stability of Pickering emulsions. However, the commonly used natural food-grade particles such as starch, cellulose and protein cannot meet the requirements for stabilizing emulsions. Hence, how to modify the natural materials in order to improve their stability and emulsifying properties is currently a difficult task. This article reviews the stability mechanism of food-grade Pickering emulsions, the commonly used food-grade particles, the methods used to modify them, and the potential applications of food-grade Pickering emulsions, which will provide a reference for the application of food-grade Pickering emulsions in the food industry.
Progress in Research on Iron-Loaded Complexes Based on Structural Assembly of Food Macromolecules
XU Kai, YAO Xiaolin, LIU Huabing, YAO Xiaoxue, CHEN Xiaoyu, LIU Ning, LI Na
2021, 42(7):  283-291.  doi:10.7506/spkx1002-6630-20200331-450
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Iron is a very essential element for human life, and iron deficiency anemia is an important problem for human health. Iron fortification is the most direct and effective method to treat iron deficiency anemia. In this paper, the characteristics of iron fortifiers, the absorption characteristics of iron and the history of the development of iron fortifiers are reviewed. The principle of constructing iron fortifiers based on the structural assembly of food macromolecules and their advantages are highlighted. This review is of great guiding significance for the development of new iron fortified food ingredients.
Advances in Food Allergen Epitope Localization Technologies
HU Yongxin, LI Xin, CHENG Jianfeng, MA Xin, MENG Xuanyi, CHEN Hongbing, WU Yong
2021, 42(7):  292-300.  doi:10.7506/spkx1002-6630-20200316-242
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Food allergens are the major causes of food allergies, which are mainly proteins. The antigen epitope is a special chemical group in the antigen molecule, which can react with antibody or be recognized by the antigen receptor, and trigger the body’s immune response. Understanding food allergens at the epitope level can reveal the material basis of food allergic reactions and provide precise targets for solving the problem of food allergy. This paper reviews the development of food allergen epitope localization technologies based on different epitope structures and localization methods, and discusses further prospects for the application prospects of allergen epitope information for improving the existing food allergen identification technologies and hypoallergenic food processing methods.
Recent Progress in the Application of Liquid Chromatography-High Resolution Mass Spectrometry in the Identification of Food Adulteration: A Review
WANG Bingfeng, XU Lei, XU Zhenzhen, CHEN Ailiang, YANG Shuming, LIAO Xiaojun
2021, 42(7):  301-310.  doi:10.7506/spkx1002-6630-20200325-371
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Food fraud refers to the act of deliberately misdescribing foods and making claims inconsistent with the true attributes. Food adulteration is the most common form of food fraud. Four kinds of adulteration behaviors, namely counterfeiting, dilution, illegal addition and mislabeling of ingredients, account for a large proportion of the numerous food fraud incidents. With the diversification of food processing methods, the globalization of food trade and the complication of the food supply chain, food adulteration is becoming more and more hidden, making it difficult to identify food adulteration by conventional targeted analysis methods. Therefore, non-targeted analysis technology has gradually become more and more popular in the field of food adulteration identification. In this review, the application of omics technology based on liquid chromatogram-high resolution mass spectrometry in food adulteration identification is summarized.
A Review of Studies on the Effects of Transportation Stress on Fish Physiological Characteristics and Meat Quality
YOU Xiaopeng, WANG Lan, XIONG Guangquan, QIAO Yu, WU Wenjin, LI Xin, DING Anzi, SUN Weiqing
2021, 42(7):  311-318.  doi:10.7506/spkx1002-6630-20200302-036
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Stress response is a widespread physiological reaction in nature. It directly affects the metabolic process and physicochemical conditions of living organisms, and is likely to adversely affect the meat quality of food animals. The transportation of live fish is an indispensable intermediate link in the production process of fish products, and it is also a major factor triggering stress response in live fish. Accordingly, this article reviews the existing literature on the effects of stress response on fish physiological characteristics, flesh quality and metabolism, and on how fish transportation affects the metabolic pathways related to flesh quality. Next, it describes the application of transcriptomics in studies on stress response in fish. This review highlights the importance and necessity of fundamental studies on stress response and its regulatory mechanism in fish.
Preparation, Characterization, Physicochemical Property and Potential Application of Enzyme-Modified Starch: A Review
ZHAI Yitan, BAI Yuxiang, LI Xiaoxiao, WANG Yu, QIU Lizhong, BIAN Xiliang, JIN Zhengyu
2021, 42(7):  319-328.  doi:10.7506/spkx1002-6630-20200306-094
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Enzymatic modification of starch granules is a method to modify starch below the gelatinization temperature. The morphology, structure, crystallinity, solubility, and gelatinization and rheological properties of starch are changed after modification, improving the processing characteristics and application value of starch. This article summarizes the changes in the structure and properties of starch granules before and after enzymatic modification as well as the enzymes and methods used for starch modification, which is expected to provide reference for the application of enzyme-modified starch granules.
Novel Strategies for Reducing Phosphates in Emulsified Meat Products: A Review of Phosphate Replacers and New Processing Technologies
ZHAO Honglei, CHANG Jingyao, CHEN Jiaxin, WANG Hao, LIU Hui, KONG Baohua, LIU Qian
2021, 42(7):  329-335.  doi:10.7506/spkx1002-6630-20200323-348
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Phosphates are widely used as common food additives in emulsified meat products. Phosphates can potentially synergize with sodium chloride to enhance the solubility of myofibrillar protein in salt solution, and promote the water holding and oil holding capacities of meat batter, thereby imparting good tenderness and juiciness to emulsified meat products. Currently, excessive contents of phosphates in emulsified meat products are a widespread problem. Excessive intake of phosphates can increase the burden on the kidney, reduce the absorption of various minerals in the body, and cause cardiovascular and cerebrovascular diseases. Thus, in order to provide healthier emulsified meat products to consumers, it is important to develop novel strategies for reducing the phosphate content in the products. However, due to the unique role of phosphates and consumers’ attaching increasing importance to clean label processed meat products, how to reduce the phosphate content of processed meat products while maintaining the original quality has become a very challenging task. Based on previous studies, this paper systematically reviews the mechanism of action of phosphate in improving the quality of emulsified meat products, and new strategies to reduce the phosphate content in the products, which will provide a theoretical reference for the development of processing technologies for phosphate-reduced emulsified meat products.
Progress in Application of Intelligent Packaging Technologies in Food Supply Chain
ZHOU Yunling, WEI Na, HAO Xiaoxiu, WANG Zaiying, LI Yuhan
2021, 42(7):  336-344.  doi:10.7506/spkx1002-6630-20200320-306
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Food waste is a worldwide problem to be solved urgently. Intelligent packaging allows real-time tracking of products, and provides supporting information for food packaging decision making, thereby reducing food loss. This article reviews the concept of intelligent packaging, the intelligent packaging technologies (time-temperature indicators, leak indicators, freshness monitoring technology, maturity monitoring technology, barcode technology, radio frequency identification technology and augmented reality technology), and the problems of applying them in the food field. It proposes that intelligent packaging would develop a low-cost, multi-functional and safe direction. This review is expected to help promote the intelligent packaging technologies to reduce food waste.
Application of 3D Printing Technology in Foods Based on Fruits and Vegetables
WANG Mingshuang, JIANG Hanqian, LI Lin, ZHANG Liang, LIU Ruihai, LI Dongnan, LI Bin
2021, 42(7):  345-351.  doi:10.7506/spkx1002-6630-20200311-182
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3D printing, a newly emerging digital production technology, has been widely used in many fields. Its applications in the field of foods can meet people’s demands for customized or personalized nutrition and digital nutrition, and can simplify the food supply chain system and broaden the source of available food materials. Fruits and vegetables, rich in a variety of nutrients, is an important part of the human diet. Compared with some food materials such as dough, chocolate and minced meat, fruits and vegetables are characterized by high water content, difficult to shape and vulnerable to browning, making them difficult to directly 3D print. In order to better understand the application of fruits and vegetables in the field of 3D food printing, this paper reviews the material requirements of 3D food printing, the characteristics and processing technology of 3D printed fruit and vegetable products. Future development trends are also proposed.
Recent Progress in Hazards and Control of Clostridium perfringens in Foods
REN Hongrong, LI Miaoyun, ZHU Yaodi, ZHAO Gaiming, ZHAO Lijun, WU Huilin, XIAO Kang, CUI Wenming
2021, 42(7):  352-359.  doi:10.7506/spkx1002-6630-20200325-363
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Clostridium perfringens is a Gram-positive anaerobic spore-forming pathogen that is widely distributed in the environment and the gastrointestinal tract of animals and humans. It can break down sugars in muscles and connective tissues to produce large amounts of gas and can form capsules. It can grow with low environmental requirements and is a common pathogen in nature. This bacterium, a major food spoilage bacterium, can form spores as a hypopus under environmental stress such as low temperature, water deficiency and nutrient deficiency, which has strong resistance to adversity. Its spores can survive in the sterilization process. Therefore, controlling contamination of C. perfringens has become a widespread concern in the field of food research. In this article, the characteristics and hazards of C. perfringens are summarized systematically and the physical and chemical methods used for controlling C. perfringens pollution are described in detail. Besides, the current research hotspots are discussed. The aim of this review is to provide the theoretical foundation for further studies to control the hazards of C. perfringens, improve food safety and promote the healthy development of the meat products industry. The information gathered here is of important practical significance for the food processing industry.