Table of Content

15 January 2020, Volume 41 Issue 1
Basic Research
Effect of High Pressure Thermal Sterilization on Physiological Characteristics of Weissella viridescens
YU Longxia, WU Xiang, LI Xinfu, ZHANG Wangang, LI Cong, XU Baocai
2020, 41(1):  1-8.  doi:10.7506/spkx1002-6630-20181121-250
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To explore the killing effect of high pressure thermal sterilization (HPTS) on Weissella viridescens, the physiological properties, morphological characteristics and membrane permeability of bacterial cells treated by either ultra high pressure (UHP) (at 350 MPa and 25 ℃ for 10 min) or HPTS (at 350 MPa and 50 ℃ for 10 min) were evaluated. The results showed that after HPTS treatment total bacteria count was significantly (P < 0.05) lower than that after UHP treatment (5.71 versus 7.67 (lg(CFU/mL))). The synergistic treatment caused the surface of bacterial cells to become seriously wrinkled, caused denaturation and coagulation of cellular contents, and damaged the cell membrane thereby altering membrane permeability and resulting in a significant increase in extracellular ultraviolet (UV)-absorbing substances (P < 0.05). In summary, HPTS could aggravate deformation of bacterial cells and increase cell membrane permeability leading to leakage of intracellular UV-absorbing substances. The results of this study provide theoretical evidence for the mechanisms of Weissella viridescens inactivation by HPTS.
Separation, Purification and Biochemical Properties of Exopolysaccharides from Weissella confusa
JIANG Jing, DU Renpeng, GUO Shangxu, ZHAO Dan
2020, 41(1):  9-15.  doi:10.7506/spkx1002-6630-20190623-270
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A strain of lactic acid bacteria (LAB) with high exopolysaccharides (EPS)-producing ability was isolated from naturally fermented melon. The strain was identified as Weissella according to its physiological and biochemical properties. In addition, the chemical composition, solubility, water-holding capacity, emulsifying property, antibacterial property and antioxidant activity of the purified EPS from this strain were determined. The results showed that the total sugar, protein and uronic acid contents were (93.67 ± 2.08)%, (0.32 ± 0.01)% and (6.01 ± 0.34)%, respectively. The dissolution percentage and water holding capacity of the EPS were (98.78 ± 1.37)% and (426.03 ± 7.26)%, respectively. It exhibited good emulsifying, bacteriostatic and in vitro antioxidant properties in a concentration-dependent manner.
Effect of Smoking Time on Heterocyclic Aromatic Amine Content and Quality of Bacon
DU Hongzhen, ZHANG Pin, TIAN Xinglei, ZHANG Lang, LIU Qian, KONG Baohua
2020, 41(1):  16-23.  doi:10.7506/spkx1002-6630-20181202-022
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The aim of this study was to investigate the effect of smoking time on the heterocyclic aromatic amine content and quality of bacon. Marinated pork belly was smoked for up to 3.0 h at 45–50 ℃. Changes in heterocyclic aromatic amines (HAAs) content and the quality of bacon during smoking were determined. The results indicated that the contents of non-polar HAAs increased significantly with longer smoking time (P < 0.05), while the contents of polar HAAs revealed an initial significant increase (P < 0.05) followed by a decrease, reaching the maximum value after 1 h. The results of color difference analysis suggested that lightness (L*) initially decreased and then increased (P < 0.05), while the opposite trend was observed for redness (a*) and yellowness (b*) (P < 0.05). In addition, water content and water activity decreased significantly, while pH, carbonyl content, and thiobarbituric acid reactive substances (TBARS) content increased significantly with the prolongation of smoking time (P < 0.05). Low field nuclear magnetic resonance analysis confirmed that there was no significant variation in the relaxation time T2b (P > 0.05), but T21 and T22 decreased significantly (P < 0.05). In short, smoking time can significantly affect the HAAs content and quality of bacon.
Characterization and Spoilage Potential of Specific Spoilage Organisms Isolated from Lightly Salted Large Yellow Croaker (Pseudosciaenac rocea)
GUO Quanyou, SHAN Ke, JIANG Chaojun, LI Baoguo
2020, 41(1):  24-32.  doi:10.7506/spkx1002-6630-20181213-166
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The purpose of this work was to investigate the characteristics and spoilage ability of dominant spoilage bacteria including Proteus vulgaris and Hafnia alvei isolated from lightly salted large yellow croaker stored at chilled temperature. The phenotypes, biochemical characteristics, carbon source utilization profiles and cell membrane phospholipid fatty acid (PLFA) compositions of the wo strains were observed. Further, sterile lightly salted fish pieces were inoculated separately with either of the strains and evaluated for changes in sensory, microbiological and chemical quality to explore their spoilage potential. The results showed that both strains grew at low NaCl concentration (≤ 4%) and pH 5–7. The overall carbon source utilization profile and dominant fatty acid components of Proteus vulgaris were similar to those of Hafnia alvei. At 5 ℃, the shelf lives of fish pieces inoculated with Proteus vulgaris and Hafnia alvei were 12 and 14 d, respectively. The total bacterial number at the end of spoilage (Nmax) were (8.90 ± 0.73) (lg(CFU/g)) and (8.70 ± 0.92) (lg(CFU/g)), and the yield factor (YTVB-N/CFU) values were 3.61 × 10-8 and 3.71 × 10-8 mg/CFU in the inoculated fish samples, respectively. Putrescine was less abundant than cadaverine in both samples, and alcohols and aldehydes were the main volatile components in them. In summary, there were some differences in physiological and biochemical characteristics between Proteus vulgaris and Hafnia alvei. Both strains had spoilage potential in lightly salted large yellow croaker and the spoilage potential of Proteus vulgaris was stronger than that of Hafnia alvei. This study provides a theoretical basis for processing optimization of lightly salted large yellow croaker and targeted inhibition of spoilage bacteria to prolong product shelf life.
Antimicrobial Activity and Mode of Action of Monogalactosyl Monolaurate against Bacillus pumilus
XU Miaomiao, ZI Yuxiang, LU Zhaoxin, Lü Fengxia, ZHANG Chong, BIE Xiaomei, ZHAO Haizhen
2020, 41(1):  33-40.  doi:10.7506/spkx1002-6630-20181123-276
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Bacillus pumilus, a foodborne pathogen closely associated with food spoilage, can cause food safety issues and substantial financial losses. Thus, developing an effective natural antimicrobial agent is crucial for controlling B. pumilus. Herein, the antimicrobial activity and action mechanism of monogalactosyl monolaurate (MGML) against B. pumilus was investigated. Results showed that the minimum inhibitory concentration (MIC) of MGML was 313 μg/mL. The antimicrobial activity was concentration dependent. MGML caused leakage of intracellular Ca2+ and K+ and ultraviolet (UV)-absorbing materials, indicating altered membrane permeability of B. pumilus cells. According to scanning electron microscopic observation, the surface of bacterial cells became wrinkled and even ruptured with holes in it after treatment with MGML, indicating that the cells were damaged. Analysis of the ultraviolet absorption spectra and the fluorescence quenching spectra suggested that MGML could cause DNA damage and affect its synthesis. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) results showed that MGML also could affect the synthesis of protein. These results suggested that MGML has the potential to be used as a food preservative against B. pumilus.
Effect of Cooking Time on Glucoraphanin and Sulforaphane Contents in Broccoli Cooked by Different Cooking Methods
LU Xu, MA Shaoying, LI Sheng, ZHANG Congcong, BAO Jinyu, ZHANG Xiumin
2020, 41(1):  41-47.  doi:10.7506/spkx1002-6630-20181201-005
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The common domestic cooking methods include steaming, boiling, stir-frying and microwaving, and vegetables may lose nutrients during the cooking processes. In this experiment, the effect of cooking time on glucoraphanin (GRA) and sulforaphane (SFN) contents, endogenous myrosinase (MYR) activity and cell membrane permeability in broccoli (cv. ‘Ruinong’) cooked by each of the four methods separately. In addition, the effect of exogenous MYR addition on converting GRA to SFN was studied. The results showed that for each cooking method, GRA content decreased with cooking time, SFN content increased first and then decreased, endogenous MYR activity decreased, and cell membrane permeability increased. Steamed broccoli retained higher contents of GRA and SFN. The addition of exogenous MYR could enhance the conversion rate of GRA to SFN in broccoli, producing more SFN.
Evaluating the Quality of Noodles Incorporated with Potato Flour Dried by Different Drying Methods Based on Coefficient of Variation
LI Yebei, REN Guangyue, QU Zhanping, DUAN Xu, ZHANG Ledao, LU Yingjie
2020, 41(1):  48-54.  doi:10.7506/spkx1002-6630-20181130-357
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In order to select a suitable drying method for composite wheat-potato noodles, this study evaluated and compared the effects of four drying methods of heat pump drying, hot air drying, cold air drying and infrared drying on the drying characteristics, quality attributes and microstructure of noodles. Overall evaluation scores of the four drying methods were obtained based on coefficient of variation. The results showed that the drying methods had significant influence on all investigated parameters (P < 0.05), and breaking rate, hygroscopicity, drying energy consumption, cooking loss rate and chewiness accounted for a larger proportion of the overall evaluation, with breaking rate contributing to the largest proportion. The results of the comprehensive evaluation showed that the quality of the composite noodles dried by heat pump drying was the best (comprehensive score of 0.239), followed sequentially by hot air drying (comprehensive score of 0.201), cold air drying (comprehensive score of ?0.062), and infrared drying (comprehensive score of ?0.701). Accordingly, heat pump drying is the best drying method.
Prediction of Preference for Sausage Based on Self-Organizing Maps Model
LIU Yujia, ZHU Jie, ZHANG Shuyan, LI Lin
2020, 41(1):  55-60.  doi:10.7506/spkx1002-6630-20190619-219
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Sausage preference was predicted using self-organizing maps (SOM) based on sensory evaluation. The texture parameters and color data of 99 sausage samples were collected and correlated versus the sensory evaluation results using linear regression analysis. Principal component analysis (PCA) was used to eliminate the redundant data. An SOM model with the competition layer of 6 neurons and the output layer of 36 neurons was established. The results showed that the accuracy rate was 100% by extracting and classifying the eigenvalues of sausage samples. At this time, the root mean square error (RMSE) of the prediction set was 0.118 4, which implies that the model showed good generalization ability. This study aims to establish an accurate and efficient method for predicting food preference, which will provide useful data for new food product development and market preference prediction.
Antibacterial Activity and Mechanism of Action of Vapor-Phase Linalool
WU Kegang, ZHAO Xinxin, DUAN Xuejuan, CHAI Xianghua, YU Hongpeng, LIU Xiaoli, FAN Yuting
2020, 41(1):  61-67.  doi:10.7506/spkx1002-6630-20181130-365
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The antibacterial activity and the underlying mechanism of vapor-phase linalool against Escherichia coli were investigated in this study. The antibacterial effect of linalool was determined and compared with that of 10 other isolate aroma compounds by vapor phase fumigation. Results showed that linalool, carvacrol, and thymol had significant antibacterial activity, with minimal inhibitory concentrations of 200, 100 and 150 μL/L, and minimum bactericidal concentrations of 200, 150 and 200 μL/L, respectively. The surface hydrophobicity of E. coli, as determined using the fluorescence probe 8-anilino-1-naphthalene sulfonate, increased after linalool treatment, indicating that the cell wall of E. coli was damaged to some extent. Transmission electron microscope (TEM) and scanning electron microscope (SEM) analysis showed that the ultrastructure of E. coli was altered after treatment with linalool vapor. Bacterial cells were shrunk and the structural integrity of both the cell wall and membrane was damaged, leading to the leakage of intracellular contents (mainly ions, nucleic acid and soluble proteins) and uneven cytoplasmic distribution. Fluorescence spectra showed that the fluorescent amino acid residues were exposed on the surface of proteins after linalool treatment. Fatty acid analysis showed that the percentages of C13:0 and C17:1 in the cell wall were increased, while the percentage of C18:0 was decreased. These results demonstrated that linalool vapor exerted antibacterial activity by disrupting the cell membrane structure and changing the fatty acid composition.
Correction for the Determination of in Vitro Digestibility of Grain Proteins
LIU Yanmei, ZHOU Xueyong, FU Rongxia, Angadi Honnursab RAJASAB, XIAO Jianzhong
2020, 41(1):  68-73.  doi:10.7506/spkx1002-6630-20181112-134
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The procedures with and without the addition of trichloroacetic acid (TCA) to determine the in vitro digestibility of cereal proteins are currently available in the literature, both of which feature unregulated deduction of background. The aim of this study was to verify the effect of TCA on the determination of the in vitro digestibility of grain proteins. Four kinds of grains (rice, corn, millet and quinoa) were hydrolyzed by pepsin and trypsin through a two-step procedure. Comparative experiments with and without TCA addition before filtration of the hydrolysates were carried out. Results showed that the protein digestibility values determined by direct filtration without TCA addition were 2.85%, 3.42%, 15.97% and 18.74% higher than those with TCA addition for the four hydrolysates, respectively. However, the values from the latter method decreased by 3.39%, 2.92%, 2.15% and 1.78%, respectively when the background values of pepsin and pepsin were not deducted. Based on these experimental results, a modified formula for the accurate determination of grain protein digestibility by TCA precipitation was proposed. Therefore, it is recommended to add TCA to the protein hydrolysates in the determination of grain protein digestibility in vitro and simultaneously to deduct correctly the blank control values of pepsin and trypsin.
Quality Evaluation of and Raw Material Selection for Wet Rice Noodles
LEI Wanying, WU Weiguo, LIAO Luyan, NI Ting, ZHANG Yu
2020, 41(1):  74-79.  doi:10.7506/spkx1002-6630-20181202-015
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In order to identify the quality indicators of rice correlated with suitability for processing into wet rice noodles and to determine their thresholds, 18 cultivars of rice were used for evaluation of the effects of the main components of rice and the pasting properties of rice starch on the cooking quality, flavor permeability, sensory quality and texture of wet rice noodles. Principal component analysis was used to establish a quality evaluation model to calculate the overall score of fresh rice noodles. The indicators associated with the overall quality of rice noodles were selected by stepwise regression analysis, and their thresholds for rice suitability for processing into rice noodles were obtained by cluster analysis. The results showed that amylose content and starch pasting properties such as trough viscosity, final viscosity, breakdown and setback value had a significant (P < 0.05) correlation with the cooking, sensory and texture quality of rice noodles, while the major components of rice and starch pasting properties were not significantly (P > 0.05) correlated with the flavor permeability of rice noodles. Amylose content and final viscosity were found to be the indicators affecting the overall quality of rice noodles were, and their thresholds in raw rice suitable for processing into wet rice noodles were higher than 26% and 3 852 Pa·s, respectively.
Food Engineering
Effect of High Pressure Homogenization on Rheological Properties and Oxidation Stability of Soy Protein Isolate-Stabilized Emulsion
LIU Jingnan, XU Yeye, WANG Yihe, SUN Hongrui, WANG Xibo, JIANG Lianzhou
2020, 41(1):  80-85.  doi:10.7506/spkx1002-6630-20181119-221
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The aim of this study was to investigate the effect of high pressure homogenization (0–4 cycles) on the rheological properties and oxidative stability of soy protein isolate (SPI)-stabilized emulsion system. The results showed that with the increase of homogenization cycles, creaming index, average particle size, the amount of interfacial protein adsorption, apparent viscosity, elastic modulus (G’) and viscous modulus (G”) increased firstly and then decreased. Hydroperoxide value (primary oxidation product) of the emulsion system continued to increase, and thiobarbituric acid reactive substances (TBARS; secondary oxidation products) value increased firstly, then decreased and finally increased once again. After three cycles of homogenization, no precipitation occurred, and the amount of interfacial protein adsorption, apparent viscosity, and G’ and G” reached their maximum; in contrast, the lowest hydroperoxide value and TBARS value were observed. As explained above, high pressure homogenization can improve the stability, rheological properties and oxidative stability of the SPI-stabilized emulsion system.
Effect of Jet Milling on Microstructure and Aging Characteristics of Maize Starch
WANG Lidong, HOU Yue, LIU Shilin, LANG Shuangjing, XIAO Zhigang
2020, 41(1):  86-93.  doi:10.7506/spkx1002-6630-20190609-085
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The microstructure and aging characteristics of waxy maize starch, normal maize starch and high amylose maize starch were investigated after superfine grinding with a fluidized bed jet mill. The particle size and size distribution, granular morphology, crystal structure, functional groups, molecular main structure, thermal and aging properties of the three starches were characterized using granularity analysis, scanning electron microscopy (SEM), X-ray diffractometry, Fourier transform infrared (FT-IR) spectroscopy, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). It was found that the particle size of waxy maize starch, normal maize starch and high amylose maize starch were significantly decreased to 6.05, 5.22 and 5.53 μm, respectively after superfine grinding, while the specific surface area increased. The microscopy analysis showed that the superfine grinding destroyed the surface morphology and crystalline areas. The relative crystallinity of waxy maize starch was more decreased (by 13.97%) than was that of normal maize starch (by 13.31%) and high amylose maize starch (by 9.44%). FT-IR spectroscopy showed that no new functional groups were produced during superfine grinding. But the molecular main of starches were broken and as a result, the molecular mass decreased and the molecular mass distribution widened. Besides, the gelatinization temperature, enthalpy and recrystallization rate constant of maize starch were reduced, retarding the aging process and increasing the storage stability of the starchy food. Finally, superfine grinding had different effects on the microstructure and physicochemical properties of maize starch with different amylose/amylopection ratios.
Cavitation Microjet Effects on Structural and Functional Properties of Okara Dietary Fiber
WU Haibo, YU Jingwen, WU Changling, LI Yang, JIANG Lianzhou, TENG Fei, WANG Zhongjiang
2020, 41(1):  94-99.  doi:10.7506/spkx1002-6630-20181119-215
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In this study, we determined the effect of cavitation microjet on the structure and function of okara dietary fiber, a byproduct of aqueous enzymatic extraction of soybean oil. We characterized the molecular structure, crystal structure, water and oil retention capacity, and swelling power as a function of treatment time using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and other analytical methods, and clarified the mechanism behind the effect of cavitation microjet on the structure. The results indicated that the water and oil retention capacity of okara insoluble dietary fiber increased to (9.42 ± 0.05) g/g and (3.92 ± 0.05) mL/g, respectively after the treatment. The swelling power increased by 1.6 folds, but the cellulose crystal configuration did not changed. However, the physical form of okara dietary fiber became smaller solid particles. Therefore, cavitation microjet technology can effectively improve the structure and functional characteristics of okara dietary fiber and thus provide technical support for the development and utilization of soybean residues.
Effect of Electron Beam Irradiation on Microstructure and Hydrolysis Characteristics of Sunflower Seed Protein
JIANG Chengyao, LIN Songyi, LI Dongmei, YANG Ruiwen, SUN Na
2020, 41(1):  100-104.  doi:10.7506/spkx1002-6630-20181220-230
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The effect of electron beam irradiation (EBI) on the microstructure and hydrolysis characteristics of sunflower seed protein was investigated in this study. Defatted sunflower seed powder was treated by different doses (0, 2.5, 5.0, 7.5 and 10.0 kGy) of EBI. Variations in the microstructure, moisture content, and hydrolysis characteristics of sunflower seed protein after the irradiation treatment were analyzed by using scanning electron microscopy, low field nuclear magnetic resonance (LF-NMR), and a laser particle size analyzer. Results revealed that EBI could change the microstructure of sunflower seed protein, and damaged the integrity of the surface structure, giving rise to pores in it and ultimately breaking it; this effect was positively related to the irradiation dose. After treatment with 2.5 kGy radiation, the surface of sunflower seed protein powder displayed many gaps and became rough; nevertheless, it still maintained an intact granular structure. When the radiation dose increased to 7.5 kGy, the surface integrity was damaged, showing fragmented morphology. Moreover, EBI above 7.5 kGy induced an increase of the hydrolysis degree of sunflower seed protein and facilitated the production of smaller peptides, which indicated that EBI improved the hydrolysis characteristics of sunflower seed protein. This study provides a theoretical basis for the application of electron beam irradiation in improving protein properties.
Raman Spectroscopy Analysis of the Effect of Cavitation Microjet on the Structure of Soybean Dreg Protein from Aqueous Enzymatic Extraction of Soybean Oil
LI Yang, HE Mingyu, WU Changling, GAO Yue, WANG Zhongjiang, LI Meng, JIANG Lianzhou, TENG Fei
2020, 41(1):  105-111.  doi:10.7506/spkx1002-6630-20181125-283
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In order to explore the effect of cavitation microjet as a new physical modification technology on the structure of soybean dreg protein from aqueous enzymatic extraction of soybean oil, we determined the Raman spectra of soybean dreg protein subjected to different durations of cavitation microfluid treatment (0, 5, 10 and 15 min). The results showed that after cavitation microjet treatment, the proportions of the secondary structure fractions α-helix and β-sheet increased significantly (P < 0.05), and the proportions of β-turn and random coil decreased. The tryptophan and tyrosine residues were in an exposed state; the proportions of disulfide bond modes g-g-g and g-g-t increased while t-g-t decreased. To sum up, cavitation microjet could result in a structural transformation of soybean dreg protein from a disordered to an ordered state, thus improving its stability. This study provides a basis for the development and utilization of soybean dregs from aqueous enzymatic extraction of soybean oil.
Nutrition & Hygiene
Effects of Grape Seed Proanthocyanins on High-Fat and High-Sugar Diet-Induced Metabolic Syndrome in Rats
ZHANG Yanhua, WANG Xiong, WANG Wenli, ZHANG Lei, CHE Huilian, ZHANG Yali
2020, 41(1):  112-120.  doi:10.7506/spkx1002-6630-20190630-420
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In this study, an SD rat model of metabolic syndrome was established by feeding a high-fat and high-sugar diet (HSHF), aiming to explore the effects of grape seed proanthocyanin extract (GSPE) on body mass, blood glucose, insulin sensitivity, serum lipids and inflammation in rats with metabolic syndrome (MetS). The results showed that the HSHF diet-fed rats developed abdominal obesity, impaired glucose tolerance, atherosclerotic dyslipidemia, liver fat deposition and other phenotypes after 24 weeks compared with the control group; and after GSPE (20, 40 and 80 mg/kg mb) intervention in rats for 8 weeks, fasting blood glucose, serum triglyceride, total cholesterol, low-density lipoprotein cholesterol, and the inflammatory cytokines interleukin-6 and tumor necrosis factor-α were significantly reduced, while high-density lipoprotein cholesterol levels were significantly elevated. In addition, hematoxylin-eosin staining analysis showed that GSPE reduced adipose cell size and liver fat deposition. Therefore, GSPE can reduce the body mass of MetS rats, improve blood sugar and lipid metabolism disorders, and reduce serum inflammatory cytokine levels and are expected to be a potential bioactive product for regulating metabolic syndrome.
Protective Effect of Ganoderma atrum Polysaccharides against Acrylamide-Induced Liver Injury in Rats
JIANG Guoyong, LEI Aitong, YANG Ying, YU Qiang, XIE Jianhua, CHEN Yi
2020, 41(1):  121-126.  doi:10.7506/spkx1002-6630-20190623-269
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Purpose: This study aimed to investigate the protective effect of Ganoderma atrum polysaccharides (PSG) on acrylamide (AA)-induced liver injury in rats. Methods: A total of 60 SD male rats were randomly divided into 6 groups of 10 each: normal control, model (20 mg/kg mb of AA), positive control (N-acetyl-L-cysteine, NAC; at 200 mg/kg mb) and low-, medium and high-dose PSG treatment groups (at doses of 50, 100 and 200 mg/kg mb). The rats in the normal control group were given normal saline at the same volume as the corresponding drugs for the other groups. Starting from half an hour after the administration, the AA aqueous solution was orally administered for 30 continuous days. Pathological observation of liver tissues was performed by hematoxylin and eosin (HE) staining. The activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) and the concentrations of triglyceride (TG) and interleukin (IL-1β and IL-10) in serum were measured. Then, the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) and the content of MDA in liver tissue homogenate were measured. Results: AA significantly increased AST, ALT and ALP activity as well as TG and IL-1β concentration, and decreased IL-10 levels in serum (P < 0.05); significantly reduced the activity of SOD and CAT and GSH-Px and increased MDA content in liver tissue (P < 0.05); and caused pathological liver injury. PSG obviously attenuated all these negative effects. Conclusion: Ganoderma atrum polysaccharides can have a significant protective effect on acrylamide-induced liver injury.
Anti-Allergic Mechanism of Glycyrrhizic Acid Based on Calcium Transport Regulation
JIANG Tianyi, SUN Lu, PU Qiurong, ZHANG Yani, CHE Huilian
2020, 41(1):  127-132.  doi:10.7506/spkx1002-6630-20181109-107
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This study aimed to explore the effects of glycyrrhizic acid (GA) on allergic reactions by using sensitized BALB/c female mice model, passive cutaneous anaphylaxis reaction and atopic dermatitis model and rat basophil leukemia RBL-2H3 cells and to explore the underlying mechanism. The results showed that GA could effectively inhibit vascular permeability and histamine level in serum of passive skin allergic mice. The serum tumor necrosis factor receptor-α level in mice with allergic dermatitis, as determined by enzyme-linked immunosorbent assay, was significantly decreased after GA administration at 10 mg/kg mb or above. Experiments with RBL-2H3 cells showed that GA could significantly reduce the release rate of β-hexosaminidase, thereby inhibiting the degranulation of mast cells. The fluorescent calcium probe Fluo-3 AM was used to analyze RBL-2H3 cells sensitized by IgE. It turned out that GA could inhibit the increase of intracellular Ca2+ level induced by antigen. Quantitative real-time polymerase chain reaction and Western blot analysis showed that GA significantly decreased the mRNA transcription and protein expression of calcium channel regulatory proteins STIM1 and TRPC1. These results suggest that GA can inhibit degranulation by regulating the expression of calcium release and transporter factors and decreasing intracellular calcium concentration after antigen stimulation.
Immunoregulatory Activity of Mung Bean Peptides
DIAO Jingjing, CHI Zhiping, LIU Yanbing, QU Liuqing, ZHANG Liping
2020, 41(1):  133-138.  doi:10.7506/spkx1002-6630-20190629-403
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In this study, we aimed to evaluate the immunoregulatory activity of mung bean peptides. Three peptides were separated from mung bean protein hydrolyzed with alkaline protease by Sephadex G-15 column chromatography, and they were screened for their immunoregulatory activity in terms of macrophage proliferation rate, glycogen content, nucleic acid content, and cytokine secretion. Among these peptides, peptide MBPH-3 had the highest immunoregulatory activity, which increased macrophage proliferation rate by 9.05% compared with the blank control group. At the same time, all three mung bean peptides could promote glucose metabolism, increase the content of nucleic acid, and enhance the expression of cytokines such as interleukin (IL), IL-1β and tumor necrosis factor-α (TNF-α). The expression levels of cytokines in the MBPH-3 treated group were 1 566.47, 593.32, 828.13 pg/mL respectively. These values were significantly higher than those in the blank control group (136.55, 139.61 and 436.18 pg/mL) (P < 0.05). Moreover, MBPH-3 could inhibit cytokine secretion induced by lipopolysaccharide (LPS) in macrophages, and the amounts of TNF-α, IL-1β and IL-6 secreted by MBPH-3 treated macrophages were 2 152.94, 1 058.81 and 859.96 pg/mL (compared to 2 923.19, 3 707.09 and 2 880.74 pg/mL for LPS stimulated macrophages), respectively. In summary, the immunoregulatory effect of MBPH-3 is the best among the three mung bean peptides. The average molecular mass of MBPH-3 is approximately 903 Da and its amino acid sequence is Asn-Asn-Tyr-Gly-Pro-Thr-Met.
Effect of α-Lactalbumin with Different Heat Treatments on Proliferation, Cell Cycle and Apoptosis of Human Intestinal Epithelial Cells
SHENG Xue, ZHANG Judian, LI Menghan, CUI Dongying, XI Enze, XU Xiaoxi
2020, 41(1):  139-146.  doi:10.7506/spkx1002-6630-20181119-211
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The effects of α-lactalbumin (α-LA) treated by pasteurization (63 ℃/30 min, 72 ℃/15 s, 85 ℃/15 s, or 95℃/10 min) on the proliferation, cell cycle and apoptosis of normal human intestinal epithelial cells (HIEC) were studied and compared. The secondary structure of α-LA with different pasteurization treatments was determined by circular dichroism spectroscopy. Then, the pasteurized α-LA was digested in vitro under simulated infant intestinal conditions and the effect of the resulting α-LA hydrolysates on the proliferation, cell cycle and apoptosis of HIEC cells at 48 h of culture was detected by cell counting kit-8 (CCK-8) assay and flow cytometry. The results showed that both raw and pasteurized α-LAs could significantly promote the proliferation of HIEC cells in a concentration-dependent manner in a certain range, and the most significant (P < 0.05) effect was achieved under the conditions of pasteurization at 72 ℃ for 15 s and 0.10 mg/mL concentration. Flow cytometry showed that both digested pasteurized α-LA and digested α-LA at a concentration of 0.10 mg/mL significantly reduced the percentage of HIEC cells in the G0/G1 phase (P < 0.05), increased the percentage of HIEC cells in the G2/M and S phase (P < 0.05), and decreased cell apoptosis (P < 0.05). These results indicated that pasteurized α-LA could significantly promote the proliferation of HIEC cells, and its mechanism may be related to the increase of the proportion of dividing cells and the consequent inhibition of apoptosis. The supplementation of α-LA pasteurized at 72 ℃ for 15 s at a recommended concentration of 0.10 mg/mL to infant formulas may improve immune function in infants, which needs to be further explored.
Effects of High-Fat Diet and Sodium Butyrate Intervention on Intestinal Mitochondrial Energy Metabolism and Intestinal Calcium Absorption in Rats
MA Shuhua, TANG Xue, ZHANG Kai, SUN Yongjuan, LI Yingrui, XING Xingan
2020, 41(1):  147-156.  doi:10.7506/spkx1002-6630-20181109-097
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Objective: To investigate the effects of sodium butyrate (NaB) on duodenum mitochondrial energy metabolism and calcium ion transport in obesity prone (OP) and obesity resistant (OR) rats. Methods: Seventy male Sprague-Dawley rats were randomly divided into: normal diet (CON), OP, OP supplemented with 4% NaB (OP + 4% NaB), OR and OR supplemented with 4% NaB (OR + 4% NaB) groups. Body mass gain and food intake were measured weekly. At the end of the 20-week feeding period, all rats were sacrificed. Then, duodenum tissue and plasma were collected quickly for determining antioxidant enzyme activities, mitochondrial energy metabolism, calcium absorption and blood calcium homeostasis-related indicators. Also, the expression of genes related to Ca2+ transport and antioxidant function in duodenum tissue were detected by quantitative real-time polymenose chain reaction (qPCR). The expression levels of important antioxidant proteins were analyzed by Western blot. Results: Compared with the OP group, the OP + 4% NaB group showed significantly decreased body mass gain (P < 0.05); and significantly increased total antioxidant capacity (T-AOC) in the duodenum (P < 0.01), decreased malondialdehyde (MDA) content (P < 0.05), up-regulated mRNA expression of the antioxidant related genes Nrf2 and NQO-1 (P < 0.01), down-regulated mRNA expression of GSK-3β (P < 0.05), and up-regulated expression of Nrf2 protein (P < 0.05). In addition, in the OP + 4% NaB group, the mitochondrial energy metabolism indicators acetyl CoA content and NADH/NAD+ ratio were significantly decreased (P < 0.01), and ATP level was significantly increased (P < 0.01); the level of mitochondrial reactive oxygen species (ROS) was significantly decreased (P < 0.01); the activities of Mn-superoxide dismutase (P < 0.01) and glutathion peroxidase (GSH-Px) (P < 0.05) were significantly increased; urinary calcium excretion was significantly decreased (P < 0.05); and calcium storage level was significantly increased (P < 0.05). Compared with the OR group, the OR + 4% NaB group exhibited significantly increased T-AOC and GSH-Px activity in the duodenum (P < 0.01), decreased MDA content (P < 0.05), up-regulated mRNA expression of Nrf2 (P < 0.05), and increased ATP level (P < 0.05), while there was no significant difference in the other mitochondrial energy metabolism-related indexes (P > 0.05). Also, compared with the OR group, the OR + 4% NaB group showed no significant difference in the indicators related to calcium balance, blood calcium homeostasis and calcium ion transport (P > 0.05). Conclusion: NaB intervention can improve the antioxidant capacity of the duodenum in OP and OR rats, reduce ROS production and maintain mitochondrial redox homeostasis. NaB can increase the intestinal calcium storage level and calcium ion transport capacity of OP rats, and the effect was greater for OP phenotype.
Effect of Pasteurized?Infant Formula on T Cell Subsets and Their Related Blood Immune Factors in Rats
CUI Dongying, XI Enze, XU Jinghan, SHENG Xue, LI Menghan, LIU Yang, WU Yuhao, XU Xiaoxi
2020, 41(1):  157-162.  doi:10.7506/spkx1002-6630-20181028-320
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Infant formula is one of the major infant formula products currently available on the market. In this experimental study, the effect of pasteurized infant formula on T cell subsets and serum immune factors in rats was explored. Healthy SD male rats were divided into 4 ?dietary treatment?groups including basal diet, commercial normal temperature infant formulas I and II, and pasteurized infant formula. Body mass, the serum levels of interleukin (IL)-2, IL-4, interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α) and lysozyme, and the relative contents of CD3+, CD4+ and CD8+ lymphocytes and CD4+/CD8+ ratio in whole blood were measured. The body mass of rats administered with the three infant formulas was significantly higher than that of rats in the basal diet group (P < 0.05). The serum levels of IL-2, TNF-α and lysozyme in the pasteurized infant formula group were significantly higher than those in the other infant formula groups (P < 0.05), and the IFN-γ level was significantly higher than that in the basal diet group (P < 0.05) but was not significantly different from that in the other infant formula groups. The serum levels of IL-4 in the three experimental groups decreased to different extents with administration time, but they were significantly higher than that in the basal diet group (P < 0.05). The relative contents of CD3+, CD4+ and CD8+ lymphocytes in the whole blood of rats given pasteurized infant formula were (34.90 ± 1.15)%, (23.93 ± 2.11)%, and (9.17 ± 0.42)%, respectively. These results showed that pasteurized infant formula promoted the growth of SD rats and the proliferation and differentiation of lymphocytes, enhanced humoral immunity and cellular immune function, and improved immune regulation in rats when compared with commercial infant formula.
SO2 Residue and Potential Dietary Health Risk Assessment in Grapes under Different Storage Conditions
TONG Jixu, ZHU Zhiqiang, QIAN Yongzhong
2020, 41(1):  163-167.  doi:10.7506/spkx1002-6630-20181206-082
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In this study, the residual level of sulfur dioxide in Red Globe grapes was determined as a function of transportation distance, harvest batch, harvest year, storage temperature and SO2 gas concentration. The potential health risk assessment of sulfur dioxide via the consumption of Red Globe grapes was also studied based on the recommended daily consumption of grapes. The results showed that sulfur dioxide was detected in all samples in the range of 5.04–39.33 mg/kg, which was lower than the maximum residue limit specified in the national standard. With the increase in transportation distance, SO2 residue continuously accumulated. The level of SO2 residue in imported grapes ranged from 6.96 to 12.46 mg/kg, lower than that in domestic grapes; the release rate of SO2 from the preservative and grape quality had significant influence on the residue of SO2. The health risk assessment results showed that the risk quotient of SO2 was less than 1 for all groups, indicating low health risk, but it should be considered that the preservative may cause bleaching damage to grapes and reduce commodity value.
Protective Effect of Oligomeric Grape Seed Proanthocyanidins on Cisplatin-Induced Mitochondrial Damage in HEK293 Cells
HAN Hedan, DU Yuemei, WANG Hai, ZHAO Yanmeng, GAO Liping
2020, 41(1):  168-174.  doi:10.7506/spkx1002-6630-20181029-339
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Objective: To investigate the protective effect and underlying mechanism of oligomeric grape seed proanthocyanidins (O-GSP) on cisplatin (CDDP)-induced mitochondrial damage in HEK293 cells. Methods: The contents of malondialdehyde (MDA), reduced glutathione (GSH) and reactive oxygen species (ROS) and the activities of hexokinase (HK), lactate dehydrogenase (LDH) and malic?dehydrogenase (MDH) were measured with relative reagent kit, and the ATP level, mitochondrial membrane potential and apoptosis rate in HEK293 cells treated by O-GSP and/or CDDP were determined by flow cytometry. Results showed that O-GSP pretreatment significantly attenuated the changes in MDA, reduced GSH and ROS contents caused by CDDP. Moreover, O-GSP significantly inhibited the decrease in ATP level and mitochondrial membrane potential and abnormal?glucose metabolism induced by CDDP (P < 0.01), thus alleviating mitochondrial damage and reducing apoptosis in HEK293 cells (P < 0.01). Conclusion: O-GSP has an antagonistic effect on CDDP-induced mitochondrial damage in HEK293 cells, which is likely to be associated with the antioxidant activity of O-GSP.
Cytoprotective Effect of Phaseolus vulgaris Peptides against H2O2-Induced Oxidative Damage in HepG2 Cells
MA Ping, CHENG Tianfu, GUO Zengwang, ZHOU Yi, WANG Xin, CAO Dongmei
2020, 41(1):  175-182.  doi:10.7506/spkx1002-6630-20181103-030
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The purpose of this experiment was to investigate the protective effect of Phaseolus vulgaris peptides (PVPs) on H2O2-induced oxidative damage in HepG2 cells and to elucidate the underlying mechanism. HepG2 cells were cultured in vitro, which were divided into blank group, model group (subjected to 2 mmol/L H2O2 stimulation for 1 h after 24 h culture under normal conditions), and low-, medium- and high-dose PVPs (subjected to 2 mmol/L H2O2 stimulation for 1 h after 24 h culture in the presence of PVPs at 50, 100 and 200 μg/mL) groups. The cell proliferation rate was measured by WST-1 assay, the reactive oxygen species (ROS) level by flow cytometry, and the intracellular antioxidant enzyme activity by enzyme linked immunosorbent assay, and the expression of apoptotic proteins by Western blot. The results showed that PVPs could alleviate growth inhibition induced by H2O2 in HepG2, reduce the levels of ROS and intracellular malondialdehyde, increase superoxide dismutase, catalase and glutathione peroxidase activity, and down-regulate p53 and caspase-3 protein expression. In conclusion, PVPs has a protective effect on H2O2-induced oxidative damage in HepG2 cells through inhibiting the expression of apoptotic proteins, regulating the cellular redox system, scavenging intracellular reactive oxygen species, and increasing intracellular activity of antioxidant enzymes.
Effect of Soluble Dietary Fiber from Defatted Rice Bran on Glucose Absorption and Transport in Small Intestine and Its Mechanism of Action
DING Xiaomeng, HOU Kunyou, HU Xiaoyi, JIA Mengyun, XIE Jianhua, CHEN Yi, YU Qiang
2020, 41(1):  183-189.  doi:10.7506/spkx1002-6630-20190606-061
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Objective: To investigate the effect of soluble dietary fiber from defatted rice bran (DRB-SDF) prepared by Trichoderma viride fermentation on glucose absorption and transport in the small intestine and to ascertain its mechanism of action. Methods: Using Caco-2 cells in vitro, glucose absorption and transport in small intestine were simulated and evaluated in the presence of different concentrations of DRB-SDF (2, 4 and 8 mg/mL). Acarbose (25 μg/mL) was served as a positive control and cells without any treatment were used as a normal control. The effect of DRB-SDF on the proliferation and viability of Caco-2 cells was detected by CCK-8 assay. Glucose concentration in the absorption and transport models was determined using a glucose test kit. Alpha-glucosidase activity was determined using an enzyme assay kit. The mRNA expression of α-glucosidase, SGLT-1, GLUT-2 and Na+-K+-ATPase was examined by reverse transcription real-time quantitative polymerase chain reaction (qPCR). Results: The proliferation of Caco-2 cells was not significantly affected when the concentration of DRB-SDF was less than 8 mg/mL. Compared with the normal control, the level of glucose absorption and transport in the DRB-SDF-treated groups was inhibited in a concentration-dependent way. The activity of α-glucosidase in Caco-2 cells was significantly inhibited after treatment with DRB-SDF, and the expression levels of α-glucosidase, SGLT-1, GLUT-2 and Na+-K+-ATPase mRNA were significantly decreased. Conclusion: DRB-SDF can delay the absorption and transport of glucose in the small intestine possibly by inhibiting α-glucosidase activity, decreasing the expression of glucose transporter proteins such as SGLT-1, GLUT-2 and Na+-K+-ATPase in intestinal epithelial cells, inhibiting carbohydrate hydrolysis, and occupying glucose absorption sites, and ultimately reducing postprandial hyperglycemia.
Schisantherin A Improves Fatigue in Mice by Regulating the Nrf2/ARE Antioxidant Pathway in Liver
ZHANG Xinyun, LIN Huijiao, LI Xin, JING Shu, SUN Wei, JIANG Weihai, WANG Chunmei, SUN Jinghui, LI He, CHEN Jianguang
2020, 41(1):  190-195.  doi:10.7506/spkx1002-6630-20181120-230
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Objective: To observe the anti-fatigue effect and underlying mechanism of schisantherin A (SCA) in mice. Methods: ICR male mice were divided into four groups: normal control group (CON group; orally given distilled water; sit-in test); chronic fatigue model group (MOD group; orally given distilled water; exhaustive exercise test), SCA (C) group (orally given SCA at 2.5 mg/kg; sit-in test), and SCA (M) group (orally given SCA at 2.5 mg/kg; exhaustive exercise test). All mice were treated once daily for 4 weeks. The effect of SCA on exercise endurance in mice was observed by weight-bearing swimming test and rotarod test. Blood urea nitrogen (BUN), lactic acid (LA), lactate dehydrogenase (LDH), creatine kinase (CK), liver glycogen (LG), muscle glycogen (MG), superoxide dismutase (SOD), malondialdehyde (MDA) and glutathione peroxidase (GSH-Px) in mice were determined by chemical colorimetry, and the level of 8-OHdG was measured with enzyme-linked immunosorbent assay; the expression of Keap1, Nrf2 and HO-1 proteins in liver tissue were measured with Western blot. Results: Compared with the CON and MOD groups, the animals from the SCA (C) and SCA (M) groups showed significantly increased exercise endurance (P < 0.05); the levels of BUN, LA, LDH, CK, MDA and 8-OHdG significantly decreased in the SCA (C) and SCA (M) groups (P < 0.05 or P < 0.01), and the levels of LG, MG, SOD, and GSH-Px significantly increased (P < 0.05 or P < 0.01). In addition, the expression of Keap1 extremely significantly decreased (P < 0.01) and the expression of Nrf2 and HO-1 increased (P < 0.01) in both SCA groups. Conclusion: SCA can improve exercise endurance in chronic fatigue mice, which may be related to increasing energy reserves and antioxidant ability in the blood and regulating the Nrf2/ARE antioxidant pathway in the liver of mice.
Probiotic Effects of Two Lactobacillus Strains in Rats Fed a High-Fat Diet
ZHU Jiexu, GAO Li’e, HUANG Wenkang, LI Wenyuan, MA Ying, GUO Xusheng, DING Zitong
2020, 41(1):  196-202.  doi:10.7506/spkx1002-6630-20181207-088
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The objective of this study was to investigate the probiotic effects of two cholesterol-lowering lactic acid bacterial strains isolated from traditional fermented yak milk in the Tibetan plateau in rats fed a high-fat diet. It has been proved that Lactobacillus helveticus BX-1 could produce bile salt hydrolase while Lactobacillus reuteri BX56 could not. Administration of strain BX-1 could significantly reduce cholesterol and triglycerides in the serum and liver of rats (P < 0.05), reduce lipid deposition in the liver, and accelerate the excretion of lipids at the same time. However, BX56 had no significant effect in lowering cholesterol in rats. Overall, BX-1 has a good cholesterol-lowering capacity and may have a potential in hyperlipidemia treatment.
In Vivo Antioxidant Capacity and Flavonoid Composition of the Seeds of Passiflora edulis Sims
LI Yan, HUANG Wei, LU Mingjian, HU Zhimin, Lü Qiujie
2020, 41(1):  203-208.  doi:10.7506/spkx1002-6630-20181102-023
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The in vivo antioxidant capacity of total flavonoids from the seeds of Passiflora edulis Sims were studied by measuring total superoxide dismutase (T-SOD) activity, catalase (CAT) activity, glutathione peroxidase (GSH-Px) activity, malondialdehyde (MDA) content and the content of protein carbonyl in liver and kidney tissues of a mouse model of D-galactose-induced oxidative damage after oral administration with the total flavonoids. Results showed that the total flavonoids could significantly increase T-SOD, CAT and GSH-Px activities (P < 0.05), and reduce the contents of MDA and protein carbonyl in mouse liver and kidney tissues (P < 0.05), indicating good antioxidant capacity in vivo. Based on gradient elution using methanol (A) and 0.25% formic acid (B) as mobile phase, the flavonoids were analyzed by liquid chromatography coupled with electrospray ionization-quadrupole-time of flight mass spectrometry (LC-ESI-Q-TOF-MS). According to the accurate mass spectral information obtained from excimer and fragment ions as well as literature data, 4 constituents were tentatively presumed, including 2-(3,4-dihydroxyphenyl)-5,7-dihydroxy-6-isopentyl-4H-chromen-4-one, 2-(4-hydroxyphenyl)-3,6-dimethoxy-8,8-dimethyl-4H,8H-pyrano[2,3-f]chromen-4-one, 5-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-3-methoxy-7-((3-methylbut-2-en-1-yl)oxy)-4H-chromen-4-one, and 7-((4-methoxybenzyl)oxy)-3-(2-methoxyphenyl)-4-oxo-4H-chromene-2-carboxylate.
Synergistic Protective Effects of Cordyceps militaris Polysaccharide Supplemented Yogurt on Alcoholic Liver Injury in Kunming Mice
HAN Yuwei, LIU Yangyang, CHEN Wei
2020, 41(1):  209-214.  doi:10.7506/spkx1002-6630-20181120-228
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Purpose: The protective effects of Cordyceps militaris polysaccharide supplemented probiotic yogurt on alcoholic liver injury in mice were investigated. Methods: Different doses (0.03%, 0.06%, 0.12%) of the probiotic yogurt following 40% ethanol were orally given to mice on a daily basis for 28 days. Body mass, liver index, serum and liver biochemical indicators were determined. Paraffin sections of liver tissue were prepared for observation of histopathological changes by hematoxylin and eosin staining. Results: In addition to remarkably improving liver damage, the probiotic yogurt at all doses could significantly reduce liver index and alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities as well as total cholesterol (TC), triglyceride (TG) and low-density lipoprotein cholesterol (LDL-C) levels in serum, increase high-density lipoprotein cholesterol (HDL-C) levels in serum and superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities, and decrease malondialdehyde (MDA) level in liver tissue (P < 0.05). Compared with the model group, liver function of mice in the high-dose group was enhanced, and the serum levels of ALT and AST were decreased by 58.87% and 38.89%, respectively. Lipid metabolism in the liver was improved; TG, TC, LDL-C levels were decreased by 39.48%, 26.92% and 38.54%, respectively, and HDL-C level was increased by 20.67%. Liver antioxidant capacity was improved as reflected by the fact that the contents of GSH-Px and SOD in mouse liver were increased by 53.95% and 25.16%, respectively, and MDA content was reduced by 49.57%. Conclusion: The protective effect of probiotic yogurt supplemented with Cordyceps militaris polysaccharides on alcoholic liver injury in mice is significantly higher than that of plain yogurt, which is positively correlated with the concentration of Cordyceps militaris polysaccharides. Therefore, there is a synergistic protective effect of yoghurt and Cordyceps militaris polysaccharides on alcoholic liver injury in mice.
Packaging & Storage
Inhibitory Effect of Oregano Essential Oil against Spoilage Microorganism Pseudomonas fluorescens and Its Influence on Quality Changes during Chilled Storage of Salmon
YANG Shengping, ZHANG Zhen, CHENG Ying, QIAN Yunfang, XIE Jing
2020, 41(1):  215-222.  doi:10.7506/spkx1002-6630-20190530-380
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This study was intended to evaluate the effect of oregano essential oil against Pseudomonas fluorescens and the quality of salmon during cold storage. The minimal inhibitory concentration (MIC) of oregano essential oil against P. fluorescens was determined in vitro, as well as its effect on the growth curve, membrane fluidity, microstructure, electrical conductivity and alkaline phosphatase (AKPase) activity of P. fluorescens. Salmon fillets were inoculated with P. fluorescens, dipped in oregano essential oil and then stored at 4 ℃. Those not treated with oregano essential oil were served as control. Changes in the quality indicators including sensory quality, bacterial count, total volatile basic nitrogen (TVB-N) content, biogenic amines and T2 parameters of nuclear magnetic resonance were studied during storage. The results showed that the minimum inhibitory concentration (MIC) of oregano essential oil against P. fluorescens was 0.062 5% (V/V). The bacterial cells treated with oregano essential oil at MIC exhibited increased electric conductivity and lose their original morphology. The fluorescence intensity of the cell membrane of P. fluorescens treated by oregano essential oil was higher than that of the control, indicating that oregano essential damaged the cell membrane during cold adaptation leading to the leakage of intracellular compounds and consequently reduced ability of P. fluorescens to regulate membrane fluidity. At the end (day 12) of storage, the total bacterial count of the treated sample decreased by 1.34 (lg(CFU/g)), the TVB-N content by 7.48 mg/100 g, and the contents of putrescine and cadaverine by 48.5% and 33.5%, respectively as compared to the control. In addition, oregano essential oil inhibited transformation of immobilized water to free water, thereby inhibiting the growth of P. fluorescens and maintaining the quality of salmon fillets.
Effect of Near Freezing Temperature Storage on the Shelf Quality of Apricots after Long Time Cold Storage
LIU Bangdi, FAN Xinguang, SHU Chang, WANG Xiaomei, CAO Jiankang, JIANG Weibo
2020, 41(1):  223-230.  doi:10.7506/spkx1002-6630-20181202-016
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Apricots (cv. Mixing) were stored at near freezing temperature (NFT, (-2.2 ± 0.2) ℃) or 0 ℃ for up to 70 days to evaluate the storage and shelf quality. During the shelf life after storage at 0 ℃ for 70 days, fruit maturation, softening and color turning as well as a decrease in sugar/acid ratio did not occur normally. However, the apricots stored at NFT for 70 days could reach normal maturity after the shelf-life period at room temperature. The ethylene production and ethylene metabolism were both higher than those in the apricots stored at 0 ℃. NFT storage also effectively maintained superoxide dismutase, ascorbic acid oxidase and catalase activities, antioxidant compound contents and antioxidant activity, and reduced the accumulation of malondialdehyde (MDA) and hydrogen peroxide. Therefore, NFT storage can not only effectively extend the storage period, but also maintain the normal physiological metabolism of ‘Mixing’ apricots, hence preserving the shelf quality after long-term cold storage.
Effects of Changes in Bacterial Proteins to Metabolites in Fresh Tan Sheep Meat during Chilled Storage
ZHAO Xiaoce, JI Chen, LUO Ruiming, HU Qianqian, YOU Liqin, YUAN Yudong
2020, 41(1):  231-236.  doi:10.7506/spkx1002-6630-20181207-096
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During the chilled storage of fresh Tan sheep meat, the bacterial proteins and their changes were studied by surface enhanced laser desorption ionization time-of-flight mass spectrometry (SELDI-TOF-MS), and the bacterial metabolites and their changes were detected by gas chromatography-time-of-flight mass spectrometry (GC-TOF-MS). Principal component analysis and thermogram analysis were used to investigate the correlation between the changes in bacterial proteins and metabolites. The results showed that the relative contents of some of the bacterial proteins increased with the prolongation of storage period; the relative contents of the metabolites positively correlated with these proteins increased, but the relative contents of those metabolites negatively correlated with these proteins decreased. In contrast, the relative contents of the other bacterial proteins decreased with the prolongation of storage period; the relative contents of the metabolites positively correlated with these proteins decreased, but the relative contents of those metabolites negatively correlated with these proteins increased. Therefore, the changes in microbial proteins on the surface of chilled mutton have an obvious effect on the microbial metabolites during storage. It is speculated that this is because the changes in bacterial protein contents have different impacts the metabolic pathways.
Effect of Lemon Essential Oil Emulsion Edible Coating on Quality Preservation of Refrigerated Pot-Stewed Duck Neck
XI Zewen, CHENG Ce, PENG Shengfeng, ZOU Liqiang, LIU Wei
2020, 41(1):  237-243.  doi:10.7506/spkx1002-6630-20181227-320
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The objective of this study was to assess the effect of an edible coating containing lemon essential oil emulsion on preserving the quality of refrigerated pot-stewed duck neck. The lemon essential oil emulsion and nanoemulsion coatings were prepared by high-speed shearing and microfluidization, respectively and their effects on physicochemical and microbial properties of refrigerated pot-stewed duck neck were comparatively studied. The results showed that the nanoemulsion had lower particle size, whiteness index and viscosity when compared with the emulsion, and the appearance was translucent. The quality of pot-stewed duck neck in the blank group declined with storage period, and complete spoilage occurred on the 12th day. At this time, the thiobarbituric acid reactive substance (TBARS) value and total volatile basic nitrogen (TVB-N) content were 3.23 mg/kg and 33.6 mg/100 g, respectively, and the total bacterial count increased to 5.79 (lg(CFU/g)). The lemon essential oil nanoemulsion had better preservation effect compared with the emulsion and sodium alginate; the TBARS value and TVB-N content of the nanoemulsion coating group were only 2.80 mg/kg and 20.76 mg/100 g, respectively, and the total bacterial count was 4.85 (lg(CFU/g)) on the 12th day. In addition, there was no significant difference in color difference between the lemon essential oil emulsion group and the blank group. The above results showed that the lemon essential oil emulsion edible coating can significantly preserve the quality of refrigerated pot-stewed duck neck, but its effect was inferior to that of the essential oil nanoemulsion coating, which could extend the shelf life of the product from 8 to 12 days.
Improving Postharvest Quality of Apple (Malus × domestica Borkh. cv. Golden Delicious) Fruit by Storage at Near Freezing Temperature
SHU Chang, LIU Bangdi, ZHANG Wanli, CAO Jiankang, JIANG Weibo
2020, 41(1):  244-251.  doi:10.7506/spkx1002-6630-20181202-011
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This study was implemented to investigate the effect of near freezing temperature (NFT) storage on the postharvest quality and antioxidant activity of ‘Golden Delicious’ apple fruit. NFT was set to be (-1.7 ± 0.2) ℃. Compared with storage at 0 ℃, NFT storage suppressed ethylene production and respiration rate, delayed the appearance of respiration peak, and maintained fruit color, higher soluble solids and titratable acid contents. In addition, NFT storage maintained higher levels of total phenols, and total flavonoids as well as higher antioxidant capacity. NFT storage retarded the increase of membrane permeability and malondialdehyde (MDA) content. Based on the results above, NFT storage should be recommended for improving the storage quality and antioxidant capacity of ‘Golden Delicious’ apple. This research provided a reference for the application of NFT storage in apple fruit storage.
Effect of Postharvest Sodium Nitroprusside Treatment on the Storage Quality and Cell Wall Degrading Enzymes of Nanguo Pears
CHENG Yuan, LI Canying, HOU Jiabao, LI Xue, WANG Xiaohan, GE Yonghong
2020, 41(1):  252-257.  doi:10.7506/spkx1002-6630-20181225-289
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In order to investigate the effect of sodium nitroprusside (SNP) treatment after harvest on the storage quality of Nanguo pears, the harvested fruit were treated with 0.25 mmol/L SNP or distilled water (control) and then were stored at room temperature. Changes in fruit quality and the activity of cell wall degrading enzymes were monitored during storage. The results indicated that SNP treatment inhibited the increase in mass loss, and significantly decreased the respiratory peak and delayed the decline in flesh firmness. SNP treatment also maintained a high level of total soluble solids and delayed the decrease in ascorbic acid and titratable acid contents. Moreover, the activity of polygalacturonase (PG), polygalacturonic acid transeliminase (PGTE), pectin methyltranseliminase (PMTE) and pectin methylesterase (PME) was significantly inhibited by SNP treatment. These results suggest that SNP could improve the storage quality of Nanguo pears by inhibiting the activity of pectin degrading enzymes.
Advances in the Properties, Stability and Delivery Systems of (-)-Epigallocatechin-3-gallate: A Review
YAN Xiaojia, LIANG Xiuping, LI Siqi, LIU Chang, LIU Fuguo
2020, 41(1):  258-266.  doi:10.7506/spkx1002-6630-20181206-076
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(-)-Epigallocatechin-3-gallate (EGCG) is a catechin monomer extracted from green tea, and is the main component of tea polyphenols. Because its structure contains a number of phenolic hydroxyl groups, EGCG has strong antioxidant activity and plays an important role in the fight against tumor and cardiovascular disease prevention. However, EGCG is susceptible to oxidation due to external factors such as light, high temperature and pH. Constructing nanocarriers (such as protein-polysaccharides based nanoparticles, hydrogels, and liposomes) can effectively solve the problem of poor stability and low bioavailability of EGCG. This paper mainly summarizes the factors affecting EGCG stability and the effects of different delivery systems on the stability and functional characteristics of EGCG, aiming to provide a theoretical basis for the application of EGCG in the food and pharmaceutical industries.
A Review of the Separation and Enrichment of Functional Peptides
LI Xinwei, LIAO Jia, DONG Xiuyu, ZHOU Xin, YANG Heqi, WU Long, WANG Qiukuan, ZHOU Hui
2020, 41(1):  267-276.  doi:10.7506/spkx1002-6630-20190629-413
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Functional peptides are widely found in nature. The naturally occurring peptides in the human body are referred to as endogenous peptides, which are closely related to the physiological activities such as growth, metabolism, immunity, and signal transduction of living organisms. Exogenous peptides, with various functions such as anti-tumor, blood pressure lowering, and bone health-promoting effects, can be obtained by protein degradation or synthesized from amino acids. However, endogenous peptides are mostly present in low abundance, and are highly susceptible to high-abundance proteins during enrichment; exogenous peptides are mixed with other components. Therefore, the isolation of exogenous peptides and the enrichment of endogenous peptides are prerequisites for studying their structures and functions. In this paper, the current methods available to separate exogenous peptides and enrich endogenous peptides are reviewed, focusing on their principles, applicable objects, advantages and disadvantages as well as future directions. We hope that this paper will lay a theoretical foundation for the structural analysis and functional development of functional peptides.
Microbial Interaction Modeling in Foods: A Review
ZHANG Wenmin, FANG Taisong, WANG Xiang, GENG Fanglin, LIU Qing, DONG Qingli
2020, 41(1):  277-283.  doi:10.7506/spkx1002-6630-20181204-055
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Mathematical models are at the core of research in predictive food microbiology (PFM). The growth of spoilage microorganisms predicted by mathematical models can be used to predict the shelf life of foods. Growth data of pathogens predicted by mathematical models are indispensible in microbial exposure assessment. In recent years, the growth dynamics of bacteria in actual food environments has been one of the major advances in PFM. First, this article presents a brief description of the traditional mathematical models used in PFM. Next, it interprets the interaction between microbes and the environment in actual food samples. Furthermore, two microbial interaction models, known as descriptive and mechanistic models, are described along with analysis of how they are deduced. Finally, future prospects for the application of these models in PFM are discussed. This review could provide useful data for the development of PFM.
Recent Progress in Studies of Factors Influencing Beef Color and Technologies for Controlling It
MING Dandan, ZHANG Yimin, DONG Pengcheng, MAO Yanwei, LIANG Rongrong, YANG Xiaoyin, LUO Xin, LI Hang, MA Wenjian, ZHU Lixian
2020, 41(1):  284-291.  doi:10.7506/spkx1002-6630-20190109-103
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Meat color and its stability are important quality characteristics of fresh beef and have a significant effect on the purchasing desire of consumers. Previous studies have shown that many factors can affect meat color and its stability. This paper reviews the effects of pre-harvest factors associated with the type and concentration of antioxidant compounds in live cattle (varieties, gender, diet and animal management and post-harvest factors (aging, different muscles and sarcoplasmic protein) on meat color and its stability, as well as the underlying mechanism. The effects of selected packaging methods, low temperature sterilization technologies (low plasma and pulsed electric field) and adding exogenous substances in improving the color and color stability of beef products are also summarized. In conclusion, this paper provides a theoretical guidance for improving beef color stability and beef quality.
Advances in Understanding the Structure and Function of Glucosinolates in Brassicaceae
TIAN Yan, DENG Fangming, QING Zhixing, ZHAO Lingyan, PENG Pei
2020, 41(1):  292-303.  doi:10.7506/spkx1002-6630-20190328-354
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Cruciferous plants are one of the most popular and widely cultivated vegetables in the world. They have a strong aroma, bitter taste and spicy flavor and possess multiple biological activities such as anti-cancer, anti-inflammatory and antioxidant effects. The compounds responsible for these special flavors and bioactive functions are mainly the secondary defense metabolite glucosinolate and its hydrolysate isothiocyanate. In this paper, the classes, structures, flavor characteristics and biological activities of glucosinolates and their degradation products in cruciferous plants are reviewed, which will provide a basis for the rational utilization of cruciferous plants and for studying the structure and function of glucosinolates in cruciferous plants.
Recent Progress in Understanding the Effect of Mutton Production and Processing Technologies on the Quality of Meat and Meat Products
LIU Wenying, WANG Shouwei
2020, 41(1):  304-311.  doi:10.7506/spkx1002-6630-20190719-242
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Mutton quality can be affected by many factors and feed composition can impact sheep growth performance, mutton yield, fatty acid composition, oxidation state, antioxidant capacity, color, glutathione peroxidase, cholesterol content, microbial species and quantities, quality stability during storage, and mutton product flavor characteristics, consumer acceptance and so forth. Slaughtering methods and ante-mortem fasting strategies can also affect mutton color and water-holding capacity, and processing methods, supplementary materials and packaging and storage environments can affect physical and chemical properties of meat products and quality stability during storage. The factors that may affect the quality of mutton and its products are summarized in this paper, with the aim of providing useful information for mutton production, processing and storage.
Research on Pickled Tea: Present and Future
YANG Qingyi, HE Caimei, GONG Fuming, TANG Xiaoyan, DONG Mingjie, LIU Chenjian
2020, 41(1):  312-317.  doi:10.7506/spkx1002-6630-20181118-200
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Pickled tea is an ethnic fermented tea with a refreshing flavor and slight sour taste. In recent years, pickled tea has been a popular research subject because of the medicinal and culinary purposes as a rich source of nutrient and its unique ethnic cultural attributes. Most studies to date have focused on the flavor compounds, microbial community structure and antioxidant activity of pickled tea, but the literature lacks systematic studies on the fermentation process of pickled tea and the underlying mechanism. In this paper, the geographical distribution, fermentation process, microbial community structure and physiological characteristics of pickled tea are reviewed. Moreover, future research directions are also proposed, in order to provide valuable data for the inheritance and protection of pickled tea.
Bioactive Substances Produced by Rhodotorula mucilaginosa: A Comprehensive Review
ZHUANG Rongyu, WANG Ruchen, QIU Xiaoting, CHE Jiahao, LI Yongyong, ZHANG Weixiao, YANG Wenge, SHI Yongmei, WU Zufang
2020, 41(1):  318-329.  doi:10.7506/spkx1002-6630-20181213-169
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The red yeast Rhodotorula mucilaginosa is a species belonging to the genus Rhodotorula. It is widely distributed in various ecosystems because of its strong adaptability to different environments. R. mucilaginosa appears to be a very promising industrial strain due to its ability to produce proteins and bioactive substances such as natural carotenoids, β-carotene, astaxanthin, polyunsaturated fatty acids (PUFA) and vitamins. This review summarizes the available data in the literature on the research and application of R. mucilaginosa in the production of lycopene, β-carotene, astaxanthin and alpha-linolenic acid and functional edible oils rich in the essential dietary ω-3 fatty acid, α-linolenic acid (ALA). Its focus is on screening for high-yield strains, construction of genetically engineered strains, and the fermentation and extraction processes as well as the applications of R. mucilaginosa in production of laccase by co-culture, cutinase and in the preparation of novel drugs from whole-cell biotransformation lead compounds.