Table of Content

15 December 2018, Volume 39 Issue 23
Basic Research
Development of Predictive Models Based on qPCR for the Growth of Listeria monocytogenes and Vibrio parahaemolyticus Coexisting on Cooked Shrimps Stored at Low Temperatures
NIU Ben1, MU Lili, ZHANG Zhaohuan, LIU Haiquan, PAN Yingjie, ZHAO Yong
2018, 39(23):  1-6.  doi:10.7506/spkx1002-6630-201823001
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The aim of this study was to develop predictive models based on quantitative real-time polymerase chain reaction (qPCR) for describing the growth of Listeria monocytogenes and Vibrio parahaemolyticus co-cultured on cooked shrimps. The strains were inoculated at the same level ((5.0 ± 0.5) (lg(CFU/g))) and cultured at low temperatures (4 and 10 ℃), and then the dynamic changes in microbial load were detected by qPCR. Three growth curve models, modified Gompertz, Logistic and Baranyi were fitted for each of the strains as well as two inactivation curve models, Log-linear and Weibull. The results showed that the modified Gompertz, Logistic and Baranyi models could successfully describe the growth curve of L. monocytogenes at low temperatures, with a coefficient of determination (R2) greater than 0.98. The inactivation of V. parahaemolyticus at 4 ℃ could be clearly described by the Log-linear and Weibull models, with R2 of 0.950 and 0.945, respectively; however, the inactivation models failed to describe the behavior changes at 10 ℃, with R2 of only 0.784 and 0.775, respectively. The results from this study provide a new clue for growth modelling of food-borne pathogens based on molecular biological techniques.
Theoretical Study on Structural Properties of N-Glycolylneuraminic Acid
CHANG Rui, LIANG Meilian, ZHOU Yingzi, LI Hongying, XU Aqi, YAN Yinxue, LIU Chunli, ZENG Xuefeng, ZHU Qiujin
2018, 39(23):  7-15.  doi:10.7506/spkx1002-6630-201823002
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N-Glycolylneuraminic acid, widely found in livestock products such as beef and pork, is considered one of the most important hazardous factors for the safety of livestock products due to its association with various intestinal inflammations. To understand its physical and chemical properties, the molecular structure of N-glycolylneuraminic acid was optimized at the M062X/6-31+G(d,p) level using density functional theory, and electronic structure parameters (molecular surface electrostatics, frontier molecular orbital, conceptual density functional activity index, natural population charge) were calculated as well as physicochemical constants (dissociation constants, octanol-water partition coefficients, bond dissociation energy). Furthermore, a theoretical simulation of infrared and ultraviolet (UV) spectra was conducted. Considering the food processing environment, seven solvents (benzene, carbon tetrachloride, ethanol, acetic acid, lactic acid, formic acid, and water) with different dielectric constants were selected for a comparison of activity parameters. The results showed that N-glycolylneuraminic acid exhibited higher electrophilic activity near the acetyl group and higher nucleophilic activity at the carboxyl group. The theoretical pKa value was 1.84, and the octanol-water partition coefficient was ?3.85. In the presence of lactic acid, the dehydrogenation dissociation energy of hydroxyl group at position O7 was the smallest, 433.413 0 kJ/mol, and the maximum UV absorption wavelength was 180.087 8 nm. The results of this study provide a theoretical basis for the dissociation or reduction of N-glycolylneuraminic acid in foods.
Accumulation and Distribution of GII.4 Norovirus in Artificially Contaminated Pacific Oyster
SU Laijin, MA Liping, LIU Hui, ZHOU Deqing
2018, 39(23):  16-21.  doi:10.7506/spkx1002-6630-201823003
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Oysters are one of the most common vectors for the transmission of noroviruses (NoVs), which are one of the most important food-borne viral pathogens worldwide. The distribution of NoVs in oysters varies significantly with seasons and tissues. In order to understand the accumulation and distribution of norovirus in oysters, oysters were farmed under controlled conditions after being artificially contaminated with GII.4 NoV in the laboratory. The contents and distribution of GII.4 NoV in various oyster tissues were detected by real-time quantitative reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry. The real-time quantitative RT-PCR results showed that the content of GII.4 NoV remained stable in the range of (8.75 ± 0.36) × 104 to (9.12 ± 0.49) × 104 copies for oyster mantle, but initially increased to a maximum of (1.15 ± 0.15) × 106 copies at 6 h and then decreased for oyster gills. The content of GII.4 NoV in oyster digestive tissues was continuously increased to reach a plateau ((1.06 ± 0.14)×106 copies) at 12 h. GII.4 NoV was mainly accumulated in oyster digestive tissues at 24 h. The content of GII.4 NoV was not significantly changed after purification (P > 0.05). The immunohistochemistry results showed that GII.4 NoV was widely distributed in the mantle edge, the gill wall and the inner wall of digestive tissues. The seasonal distribution of GII.4 NoV in various oyster tissues was in accordance with the real-time quantitative RT-PCR results.
Effect of Superfine Plaice Bone Paste on Gel Properties of Nemipterus virgatus Surimi
LI Xuepeng, LIU Cikun, FAN Daming, WANG Jinxiang, YI Shumin, LI Jianrong, LI Tingting, LI Yujin, MOU Weili, SHEN Lin, HUANG Jianlian
2018, 39(23):  22-28.  doi:10.7506/spkx1002-6630-201823004
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Superfine fish bone paste, prepared by using wet superfine grinding from plaice bone, was added to Nemipterus virgatus surimi to develop calcium-rich surimi products. In order to investigate the effects of addition of different amounts (2.5%–12.5%) of fish bone paste on the quality of surimi products, the pH of surimi sol, the Ca2+-ATPase activity of myofibrillar protein, gel strength, texture properties, water-holding capacity, color, solubility and microstructure were examined. The results showed that adding fish bone paste had no influence on the pH of surimi sol. The activity of Ca2+-ATPase was apparently improved with the addition of up to 5.0% fish bone paste, due to the presence of Ca2+ in fish bone paste. The gel strength, texture, water-holding capacity and color were highest, while gel solubility was lowest in the surimi with 5.0% fish bone paste. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and scanning electron microscopy (SEM) indicated that adding 2.5%–5.0% fish bone paste to surimi could promote the cross-linking of myosin heavy chain and facilitate the formation of a compact and homogenous network structure in surimi gel, while excessive addition of fish bone paste could destroy the cross-linking and gel network.
Crispness Variation and Mathematical Modeling of Microwave-Freeze Drying of Chinese Yam Chips
DUAN Liuliu, DUAN Xu, REN Guangyue
2018, 39(23):  29-35.  doi:10.7506/spkx1002-6630-201823005
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In order to determine the crispness variation of microwave-freeze dried Chinese yam chips during the drying process, Chinese yam was dried in a microwave vacuum freeze dryer and the drying characteristics were evaluated. Meanwhile, changes in pore structure and texture characteristics during the drying process were analyzed by scanning electron microscopy, mercury porosimetry and puncture test, and a mathematical model describing the crispness of Chinese yam chips was developed to predict the quality change of Chinese yam chips during the drying process. The results showed that the whole drying process included acceleration and deceleration stages without a pronounced constant speed stage. The moisture content was lower with prolonged drying; the pore network structure was more compact. The higher the microwave intensity, the faster the drying rate, the lower the moisture content, and the denser the pore network structure. The best model was found to be the DoseResp model: y = A1 + (A2?A1)/(1 + 10((lg x0?x)p)) (R2 > 0.99), where x is the moisture content, y is crispness and A, x0 and p are coefficients. This model could better predict the crispness of Chinese yam chips.
Correlation between Egg Internal Quality and Respiration Intensity
WANG Jiaojiao, WANG Qiaohua, ZHU Zhihui, MA Yixiao
2018, 39(23):  36-40.  doi:10.7506/spkx1002-6630-201823006
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The changes of egg albumen and yolk quality during storage are closely related to respiration. In order to further clarify the relationship between egg internal quality and respiration intensity, this study tested eggs from the same chicken breed. The respiratory intensity of eggs was measured by a commercial instrument and it was correlated with Haugh unit, egg albumen height, pH, viscosity, yolk index, yolk proportion and yolk color by SPSS 19.0 software package. The results indicated that respiratory intensity was significantly correlated positively with Haugh unit, egg albumen height, viscosity and respiration intensity (P < 0.01) but negatively with pH (P < 0.01). In addition, there was a significantly positive correlation between respiratory intensity and yolk index and yolk color (P < 0.01), although the correlation of yolk proportion and respiration intensity was not statistically significant. Furthermore, pH was significantly negatively correlated with viscosity, yolk index and yolk color (P < 0.01). Viscosity was positively correlated with both yolk index and yolk color (P < 0.01). The correlation between yolk ratio and other parameters was not significant. It can be concluded that some egg internal quality parameters such as Haugh unit, egg albumen height, pH, viscosity, yolk index and yolk color can considerably affect respiration intensity.
Effect of Different Feeding Regimes on Slaughter Performance, Meat Quality and Lipid Oxidation of Sunit Sheep
WANG Bohui, YANG Lei, SU Rina, LUO Yulong, WANG Yu, ZHAO Lihua, JIN Ye
2018, 39(23):  41-46.  doi:10.7506/spkx1002-6630-201823007
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The aim of this study was to investigate the effect of different feeding regimes (grazing and stall feeding) on slaughter performance, meat quality and lipid oxidation of Triceps brachii muscle in 12-month-old Sunit sheep. The fatty acid composition of muscles was determined by high performance liquid chromatography (HPLC) and gas chromatographymass spectrometry (GC-MS). The results showed that the live mass, carcass mass and net meat mass of stall-fed sheep were significantly higher than those of grazing sheep (P < 0.05). A significant increase in meat lightness (L*) and yellowness (b*) was observed comparing grazing and stall-fed sheep, whereas the opposite was found for shear force (P < 0.05). There were no differences in the contents of protein and cholesterol between the two groups (P > 0.05). The content of intramuscular fat in grazing sheep was significantly lower than that in stall-fed sheep (P < 0.05). The percentage of polyunsaturated fatty acids in grazing sheep was higher than that in stall-fed sheep (P < 0.05), especially conjugated linoleic acid, α-linolenic acid, eicosapntemacnioc acid and docosahexaenoic acid. After three months of storage, the thiobarbituric acid value in grazing sheep was lower than that in stall-fed sheep (P < 0.05), indicating that meat from grazing sheep has higher antioxidant capacity. Stall-fed sheep had better slaughter performance and were more suitable for processing, while the nutritional value of meat from grazing sheep was higher. In practice, different feeding regimes should be chosen according to the use of mutton.
Preparation of Cibacron Blue F3GA Affinity Chromatography Medium and Its Specific Adsorption toward Lectin from Black Kidney Beans
ZHAO Jinlong, LI Yanhong, SUN Hanju, FANG Li, SUN Xianbao, TANG Mingming, ZHANG Yang, WU Xiangyu, HE Shudong
2018, 39(23):  47-53.  doi:10.7506/spkx1002-6630-201823008
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Agarose microspheres (6 g/100 mL) were prepared by reversed-phase suspension regeneration method and they were cross-linked twice with epichlorohydrin and then coupled with the dye Cibacron Blue F3GA as a special ligand to form novel active microspheres (Blue Beads 6FF). The properties of the dye affinity medium were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), pressure against flow velocity curve, swelling rate, leakage rate, and porosity. Our results showed that the microspheres had a good sphericity and uniform size with high porosity and swelling rate, a wide range of pH stability and strong pressure resistance. The average particle size of the microspheres was approximately 56.37 μm. The adsorption properties of the dye affinity medium were evaluated for lectin purification from black kidney beans. By fitting the typical Langmuir adsorption isotherm, the equilibrium adsorption capacity of lectin from black kidney beans was determined as 19.7 mg/mL microspheres. The dye affinity microspheres enabled rapid isolation and purification of lectin.
Protective Effect of Phenolic Compounds from Lycopus lucidus Turcz. on DNA Damage
GUO Qi, GAO Chunyan
2018, 39(23):  54-59.  doi:10.7506/spkx1002-6630-201823009
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Free phenolics (FP) and insoluble cell wall-bound phenolics (ICP) from Lycopus lucidus Turcz. were obtained by ultrasound-assisted extraction. The phenolic contents were determined by the Folin-Ciocalteu method and the phenolic compositions were analyzed by high-performance liquid chromatography (HPLC). The protective effects of phenolic extracts on peroxyl radical (ROO·)-mediated DNA damage were investigated and correlated to phenolic contents. The results indicated that both the phenolic compounds possessed protective effects against ROO·-mediated DNA damage with FP being more effective. Significant positive correlations were observed between ICP from L. lucidus Turcz. on December 15th, 2016 and January 14th, 2017 and protective effects on DNA damage (P < 0.05).
Effect of Addition of Sweet Potato Residue Treated by Steam Explosion on Wheat Flour Properties and Quality Characteristics of Cookies
LIANG Xinhong, FENG Longfei, WANG Tianlin, SUN Junliang, RAN Junjian, LIU Benguo, MO Haizhen
2018, 39(23):  60-65.  doi:10.7506/spkx1002-6630-201823010
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The effect of sweet potato residue treated by steam explosion (SE-SPR) on wheat dough properties and quality characteristics of cookies was studied. The sedimentation index, starch gelatinization properties and farinographical characteristics of wheat flour mixed with different proportions of SE-SPR and the texture properties of cookies made from their mixtures were measured instrumentally. The results showed that the sedimentation index of wheat flour and the peak viscosity, trough viscosity, breakdown, final viscosity and setback of wheat starch paste were decreased with the addition of SE-SPR. The addition of SE-SPR to wheat flour resulted in dilution of gluten. Accordingly, increasing soluble dietary fiber content increased the water-absorbing capacity, reduced dough development and stability time, increased dough softening degree, and decreased farinograph quality number. Furthermore, the texture properties of the cookies made from the mixture were changed as compared with those of pure wheat cookies. According to texture properties and sensory evaluation, the quality of cookies made from low-gluten flour with 6% (m/m) SE-SPR added was best.
Microbial Community Analysis of North Chinese Tofu and Effect of Low-Water Pulping on Controlling Spoilage Microorganisms
LIU Lisha, ZHAO Jinhong, JIANG Huabin, ZHANG Qing, JIN Yang, BAI Jie, LI Yumei, PENG Yijiao
2018, 39(23):  66-72.  doi:10.7506/spkx1002-6630-201823011
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In the present study, the microbial communities in packaged and unpackaged north Chinese tofu were analyzed. The dominant spoilage microorganisms were isolated and identified from these samples and their spoilage capacity and distribution during tofu processing were evaluated. Also, the effectiveness of low-water pulping in controlling microbial contamination in soybean pulp was determined. As a result, we obtained five dominant strains and identified them as Lactococcus lactis (BDF-1), Kurthia gibsonii (BDF-2), Enterobacter aerogenes (BDF-3), Empedobacter brevis (BDF-4) and Bacillus subtilis (BDF-5) based on morphological characteristics and 16S rDNA gene sequence analysis. Each strain was re-inoculated onto the surface of tofu to examine their effect on the total viable count, pH, soluble amino nitrogen content and sensory quality of tofu. All five strains could result in quality deterioration in tofu samples (minimum spoilage concentration 107 CFU/g). BDF-2, BDF-3, BDF-4 and BDF-5 altered the color of tofu, softened tofu, and produced spoilage odor, while BDF-1 produced acid to decrease the pH. BDF-1, BDF-3 and BDF-4 were the dominant spoilage bacteria during the industrial processing of packaged north Chinese tofu. Low-water pulping reduced the microbial load from 2.3 × 108 to 7.0 × 104 CFU/g, improving the processing stability and safety of north Chinese tofu. Thus low-water pulping could provide a basis for automatic processing of north Chinese tofu.
Kinetic Studies on 5-Hydroxymethylfurfural Formation in Six Sugar-Enzymatic Protein Hydrolysate Model Systems
SUN Ying, ZHANG Lili, ZHANG Yuyu, SUN Baoguo, CHEN Haitao
2018, 39(23):  73-79.  doi:10.7506/spkx1002-6630-201823012
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The formation kinetics of 5-hydroxymethylfurfural (5-HMF) was investigated in model Maillard reaction systems consisting of two sugars (glucose and sucrose) and enzymatic protein hydrolysates from pork, beef and chicken. The 5-HMF content of the Maillard reaction products (MRPs) was determined by high performance liquid chromatography (HPLC). Results indicated that 5-HMF content was linearly correlated with heating time during thermal processing at 90–110 ℃ for 0–6 h. The formation of 5-HMF followed zero-order kinetics. 5-HMF content was positively correlated with heating time and temperature. The concentration of 5-HMF formed in the glucose-protein hydrolysate systems was much higher than that formed in the sucrose-protein hydrolysate systems.
Effect of High Temperature Treatment on Chemical Forces of Beef Proteins and Structure of Myofibrillar Protein
KANG Huaibin, ZOU Liangliang, ZHANG Huiyun, CAI Chaoqi, WANG Bo, KE Hairui
2018, 39(23):  80-86.  doi:10.7506/spkx1002-6630-201823013
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Beef longissimus dorsi muscle was treated at different high temperatures (110, 115 and 121 ℃ for 3, 6, 9, 12 and 15 min, respectively). Structural changes in terms of protein chemical bonds, Fourier transform infrared, ultraviolet-visible and fluorescence spectra, and protein fragment size were analyzed in order to investigate the effect of high temperature treatment on chemical forces of beef proteins and the structure of myofibrillar protein. The results showed that contents of ionic bonds and hydrogen bonds in beef proteins significantly reduced (P < 0.05), whereas hydrophobic interaction and disulfide bond content increased significantly (P < 0.05) with increasing temperature and prolonged heating time. The secondary structure of myofibrillar protein was rearranged, and the stretching vibration of N?H and C?N and the bending vibration of N?H were clearly observed. After high temperature treatment, aromatic amino acid residues were exposed on the surface of the molecule, and the local structure of the myofibrillar protein hydrophobic region and the protein tertiary structure were changed. In addition, myofibrillar protein was degraded and aggregated significantly to form a large amount of small molecular mass protein fragments. Therefore, high temperature treatment can significantly change chemical forces of beef proteins and the structure of myofibrillar protein. This finding provides a basis for revealing the mechanisms of change in beef protein at high temperature.
Effect of Oxidation Treatment on Eating Quality and Calpain Activity in Breast and Drumstick Meat from White Feather Broilers
DENG Kaibo, HUANG Yaping, XU Zhengjin, FU Lingyun, ZHENG Baodong
2018, 39(23):  87-92.  doi:10.7506/spkx1002-6630-201823014
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This study explored the effect of oxidation treatment on the water-holding capacity, nutrient contents and calpain activity of breast and drumstick meat from white feather broilers. The results showed that oxidation treatment could decrease the water-holding capacity, increase the cooking loss and consequently reduce the cooking yield of chicken breast and drumstick meat. The concentration of hydrogen peroxide solution (H2O2) affected protein and lipid oxidation. The levels of nutrients such as protein and lipid significantly dropped with increasing concentration of H2O2. Similarly, calpain activity declined with the increase in H2O2 concentration. Thus, it is speculated that changes in calpain activity are closely associated with changes in broiler meat quality.
Food Engineering
Characterization and Stability Evaluation of Docosahexaenoic Acid Delivery Systems under Various High Pressure Homogenization Conditions
WANG Bo, ZHANG Shuwen, LIU Lu, PANG Xiaoyang, LU Jing, Lü Jiaping, YU Jinghua
2018, 39(23):  93-99.  doi:10.7506/spkx1002-6630-201823015
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The purpose of this study was to evaluate the effect of high pressure homogenization conditions on the physical and oxidative stability and microstructure of two different O/W emulsion-based systems, prepared with Maillard reaction products (MRPs) from sodium caseinate with glucose (NaCN-glu) and sodium caseinate (NaCN) as the emulsifier, respectively for the delivery of docosahexaenoic acid (DHA). The physical and oxidative stability and microstructure were evaluated by a vertical scan analyzer (Turbiscan), measurement of total oxidation value (TOTOX) and confocal laser scanning microscopy. The results showed that the NaCN emulsion was found to be much less stable than the NaCN-glu emulsion under the same conditions, and sodium caseinate had excellent emulsifying properties and antioxidant activity after Maillard reaction modification. Moreover, homogenization pressure and cycles had a significant impact on emulsion stability and microstructure. Better NaCN-glu emulsion was obtained through high-pressure homogenization at 95 MPa performed for 3 times. Turbiscan analysis showed that slight creaming at the top and clear bottom were found for the emulsion, with a Turbiscan stability index (TSI) of 1.55, which was lower than that of the other groups; the TOTOX value was the lowest at each time point during storage for up to 28 d at 25 ℃. Confocal laser scanning microscopy revealed smaller uniform droplets with intact morphology mainly distributed between 0.47 and 0.59 μm.
Effects of Ultrasonic Pretreatment with Different Working Modes on Enzymatic Hydrolysis and Structural Characteristics of Lotus Seed Protein
WU Longkun, JIANG Lianzhou, WANG Lijuan, XIAO Zhigang
2018, 39(23):  100-105.  doi:10.7506/spkx1002-6630-201823016
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Ultrasonic frequency is one of the major ultrasonic parameters that affects protein enzymatic hydrolysis. In this study, we therefore investigated the effect of ultrasonic pretreatment with different working modes (single-, dual- and triplefrequency ultrasonic) on the degree of papain-catalyzed hydrolysis of lotus seed protein and the angiotensin converting enzyme (ACE) inhibitory activity of the resulting hydolsates. Twenty, 20/35 and 20/35/50 kHz were found to be the optimal conditions for single-, dual- and triple-frequency ultrasonic treatment, respectively. Moreover, the effect of ultrasonic pretreatment with different working modes on the surface hydrophobicity and amino acid composition of the enzymatic hydrolysates and we also characterized their structure by intrinsic fluorescence spectroscopy. The results showed that the surface hydrophobicity and the number of hydrophobic amino acids with the increase of ultrasonic frequency, primarily because ultrasonic treatment resulted in protein unfolding and consequently exposure of hydrophobic groups buried within the protein molecule. Furthermore, ultrasonic treatment increased the fluorescence intensity of lotus seed protein and the highest fluorescence intensity was obtained with triple-frequency mode followed by dual- and single-frequency modes. The maximum absorption wavelength of the enzymatic hydrolysates showed a slight red shift. The above findings are of great significance for studying the enzymatic hydrolysis of lotus seed protein to prepare ACE inhibitory peptides.
Effect of Irradiation Treatment on Microbial Inactivation and Quality of Pitaya Pulp
DU Xiaojing, BAI Xinpeng, LI Zhuoting, LIU Pin, CAO Jun, JIANG Zefang, DENG Zhiyong, GAO Xiaodong
2018, 39(23):  106-112.  doi:10.7506/spkx1002-6630-201823017
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In order to determine a suitable irradiation dose and storage temperature for prolonging the shelf-life of red pitaya pulp, changes in microbial populations and nutritional and sensory qualities were determined regularly during storage at room temperature after irradiation at different doses. Furthermore, quality changes of red pitaya pulp irradiated at the selected dose were investigated during storage at different temperatures (-4, 10 or 25 ℃). The results showed that the suitable irradiation dose for the preservation of pitaya pulp was 3 kGy. This irradiation treatment significantly delayed the decrease in the contents of anthocyanins, betanin and VC during storage and maintained better sensory quality without syneresis or hyalinization. The decrease in the contents of total sugar, anthocyanins and betanin and pH in pitaya pulp irradiated at 3 kGy was inhibited during low-temperature storage. Therefore, the best storage temperature for the irradiated pitaya pulp was ?4 ℃.
Structure and Solubility of Soybean Protein Isolate-Sugar Conjugates Prepared by Ultrasonic Pretreatment
ZHAO Chengbin, QI Baokun, ZHANG Hao, LIU Jingsheng, XU Xiuying, CAO Yong, WU Yuzhu, WU Fei
2018, 39(23):  113-119.  doi:10.7506/spkx1002-6630-201823018
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Soybean protein isolate (SPI) was glycated with glucose or maltose and the SPI-sugar conjugates were pretreated by ultrasound. We aimed to evaluate the effect of ultrasonic pretreatment on the structure and solubility of SPI-sugar conjugates. Glucose was more easily glycated with SPI than maltose. The SPI-sugar conjugates prepared by ultrasonic pretreatment had higher degree of graft and lower browning intensity. The largest degree of grafting of SPI-sugar conjugates was observed after ultrasonic pretreatment for 20 min. Fourier transform infrared spectroscopic (FTIR) analysis demonstrated the formation of SPI-sugar conjugates. Glycosylation with sugar could attenuate the transition of SPI secondary structure from an ordered to disordered state during heat treatment, making the tertiary structure of SPI more loose. While ultrasonic pretreatment exerted no significant effect on the secondary structure of SPI-sugar conjugates (P > 0.05), it could make the tertiary structure more loose, which might be the major reason for the high solubility of SPIsugar conjugates prepared by ultrasonic pretreatment. Furthermore, the improved solubility could be partially because ultrasonic pretreatment enhanced the degree of grafting of SPI-sugar conjugates.
Nutrition & Hygiene
Preparation of Peptides Derived from Enzymatic Hydrolysate of Abalone Viscera and Their Inhibitory Effect on MDA-MB-231 Human Breast Cancer Cells
CHEN Shenru, WEI Peixiao, YE Yanjun, CHEN Jun, WENG Wuyin
2018, 39(23):  120-125.  doi:10.7506/spkx1002-6630-201823019
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Peptides were prepared from the enzymatic hydrolysate of abalone viscera by sequential ultrafiltration and nanofiltration. The effect of the peptides at different concentrations on cell proliferation and apoptosis in MDA-MB-231 human breast cancer cells was investigated in this study. Our results showed that the peptides were composed of 71.62% protein, 3.38% carbohydrate and 11.48% ash. The molecular mass distribution of the peptides ranged from 350 to 1 000 Da, and they were mostly concentrated around 350 Da, suggesting that oligopeptides consisting of two or three amino acids were the major constituents. The peptides at all concentrations (1, 2, 4 and 8 mg/mL) could inhibit cell proliferation in MDA-MB-231 cells in a concentration-dependent manner as assessed by methyl thiazolyl tetrazolium (MTT) assay. The number of adherent cells decreased and the number of round cells increased with increasing peptide concentration. In addition, some cell nuclei were condensed. Flow cytometry showed that the cells treated with the peptides were arrested at the S and G2 phases. The peptides could induce cell apoptosis and necrosis and consequently inhibit cell proliferation in MDA-MB-231 cells. In conclusion, the peptides prepared from abalone viscera have potential as a supplementary ingredient in antitumor functional foods.
Identification of a Tripeptide Arg-Asn-His from Chinese Baijiu and Its Antioxidant Activity
HUO Jiaying, SUN Baoguo, ZHENG Fuping, SUN Jinyuan, SUN Xiaotao, LI Hehe, LUO Xuelian, HUANG Mingquan
2018, 39(23):  126-133.  doi:10.7506/spkx1002-6630-201823020
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In this paper, a novel tripeptide was isolated at a concentration of (18.78 ± 0.34) μg/L from Chinese Baijiu by direct condensation, and its structure was identified as Arg-Asn-His (RNH) by high performance liquid chromatographquadrupole- time-of-flight mass spectrometry. The synthetic RNH was used to explore the protective effect of RNH on oxidative damage induced by 2,2’-azobis(2-methyl propionamidine) dihydrochloride (AAPH) in human hepatoma cells (HepG2). The results showed that RNH had a potent scavenging effect against intracellular reactive oxygen species by increasing the activities of antioxidant enzymes (catalase, superoxide dismutase and glutathione peroxidase) and the level of reduced glutathione in the cells. In addition, it prevented the increase of malondialdehyde level and decreased AAPH-induced lipid peroxidation level, thereby enhancing cellular antioxidant defense capacity. The antioxidant activity of the peptide was dose dependent. The results of this study can provide better understanding of the relationship between Chinese Baijiu and health.
Quantitative Risk Assessment of Cross-Contamination of Listeria monocytogenes during Low-Temperature Emulsified Sausage Processing
JIANG Ronghua, DU Jianping, CUI Yang, ZHANG Chunyan, LIU Yangtai, ZHU Jianghui, WANG Xiang, LIU Qing, DONG Qingli
2018, 39(23):  134-141.  doi:10.7506/spkx1002-6630-201823021
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The aim of this study was to quantify the cross-contamination of Listeria monocytogenes during the chopping and stuffing of low-temperature emulsified sausage. After being inoculated with 1 mL of L. monocytogenes suspension, 25 g of cured meat was used to simulate the processing of low-temperature emulsified sausage. The transfer rate of L. monocytogenes between different media was determined during chopping and stuffing to establish an exposure assessment model for L. monocytogenes cross-contamination. Moreover, the morbidity of healthy and susceptible populations after consumption of L. monocytogenes-contaminated sausages were compared using exponential model, Beta-Poisson model, Weibull-Gamma model and Log-Logistic model. The results showed that the transfer rate of L. monocytogenes from the processing equipment to meat samples was higher than that of the opposite direction significantly (P < 0.05). Based on morbidity calculation and risk consideration, Weibull-Gamma model was the most reasonable dose-response model and the morbidity with consideration of L. monocytogenes cross-contamination during chopping and stuffing was significantly higher than that without the consideration.
Effect of Co-administration of Mixed Probiotic Culture and Litchi Polyphenol on Intestinal Morphology and Intestinal Flora of Mice with Diarrhea
ZHANG Junli, TU Du, PENG Xinyu, HUANG Ting, YUAN Minggui, XU Zhihong
2018, 39(23):  142-148.  doi:10.7506/spkx1002-6630-201823022
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The effects of co-administration of a mixed probiotic culture of Lactobaccillus acidophilus and Clostridium butyricum and litchi polyphenol on the intestinal morphology and intestinal flora of mice with diarrhea were explored. A mouse model of diarrhea was established by intragastrical administration of castor oil. After four days of treatment with different medications, the duodenum, jejunum and ileum of mice were harvested and fixed in formalin solution for paraffin sectioning and HE staining, and then examined under an inverted microscope. Intestinal villus length and crypt depth were measured and the ratio of villus length to crypt depth (V/C) was also calculated. Feces were sterilely obtained for analysis of the change in intestinal microbiota by polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE). The dominant DGGE bands were recovered, cloned and sequenced, and the sequences were analyzed by BLAST. Results showed that Lactobacilli acidophilus alone and in combination with Clostridium butyricum could increase the V/C ratio of duodenum and jejunum, and the combination of the mixed probiotic culture and litchi polyphenol could improve the V/C ratio of jejunum and ileum. The DGGE fingerprint and the sequencing results showed that Lactobacilli acidophilus, the mixed probiotic culture alone and in combination with litchi polyphenol could increase the abundance and micro-ecological stability of intestinal flora in mice with diarrhea. In addition, the mixed probiotics could also increase the complexity of the intestinal bacterial community. More dominant bands were observed for all three treatment groups compared with the normal and model groups. Furthermore, new bands were also obtained with the mixed probiotics and its combination with litchi polyphenol. The best effect was observed with the mixed probiotics.
Antihypoxia Activity of Yak Blood Oligopeptides and Underlying Mechanism
XIAO Lan, WANG Wei, WU Yujiao, DU Xin, LI Cheng
2018, 39(23):  149-154.  doi:10.7506/spkx1002-6630-201823023
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This work was performed to explore the antihypoxia activity of yak blood oligopeptides and to elucidate the underlying mechanism. A total of 75 mice were randomly divided into hypoxia model, positive control (Rhodiola rosea L. roots) and high-, middle-, and low-dose yak blood oligopeptide groups. All mice were administered by gavage for 30 continuous days. At 60 min after the last administration, they were kept in airtight volumetric flasks until they stopped breathing and then myocardial and brain tissues were harvested immediately for the measurement of biochemical parameters. The results showed that yak blood oligopeptides had good antianoxic activity, and could protect brain and heart tissues of mice from atmospheric hypoxia. Compared with the model group, yak blood oligopeptides at high dose could significantly reduce malondialdehyde (MDA) content (P < 0.01), H2O2 level (P < 0.01) and lactate dehydrogenase (LDH) activity (P < 0.01) in brain and myocardial tissues of atmospheric anoxia mice, improve superoxide dismutase (SOD) activity (P < 0.01), glutathione peroxidase (GSH-Px) activity (P < 0.01 for myocardial tissue, P < 0.05 for brain tissue) and catalase activity (P < 0.01), and increase the content of adenosine 5’-triphosphate (P < 0.01). The above results showed that yak blood oligopeptides could alleviate oxidative stress injury caused by hypoxia in the body, and the mechanism may be related scavenging free radicals, inhibiting lipid peroxidation, and maintaining antioxidant enzyme activities and normal oxidative phosphorylation in mitochondria.
Effects of Polysaccharides from Crataegus songorica K. Koch. Fruits on D-Galactose-Induced Aging Mice
MA Xue, Lü Haiying, LI Jin, ZHANG Yu, ZHANG Jun
2018, 39(23):  155-160.  doi:10.7506/spkx1002-6630-201823024
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This purpose of this study was to explore the effect of polysaccharides extracted from the residue left after the extraction of anthocyanins from Crataegus songorica K. Koch. fruits on D-galactose-induced aging mice. The polysaccharides were prepared by water extraction and alcohol precipitation and were orally administered to D-galactoseinduced aging mice at three different doses (200, 400 and 800 mg/kg). Glutathione peroxidase (GSH-Px) activity, total antioxidative capability (T-AOC) and malondialdehyde (MDA) content in brain, liver and serum were measured. Histological extraction of liver and brain tissues was carried out as well. The results showed that high-dose polysaccharide could significantly improve the activity of GSH-Px in liver and serum (P < 0.05, P < 0.01), increase T-AOC in brain and liver (P < 0.01, P < 0.05), decrease the content of MDA in liver, brain and serum (P < 0.05, P < 0.01) when compared with the model group. The structure of liver lobule was intact in mice from the medium- and high-dose polysaccharide group, with no apparent fat vacuoles being observed in hepatocytes. The structure of hippocampal nerve cells, arranged orderly, was clear. In conclusion, the polysaccharides from Crataegus songorica K. Koch. fruits can protect against D-galactose-induced aging in mice, which provides a clue for the efficient utilization of Crataegus songorica K. Koch..
Apoptosis-Inducing Effect and Underlying Mechanism of Aroma Components from Douchi on Human Nasopharyngeal Carcinoma CNE-1 Cells
LI Guijie, ZHANG Jing, SUN Peng, QIAN Yu, ZHAO Xin
2018, 39(23):  161-169.  doi:10.7506/spkx1002-6630-201823025
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Douchi is a traditional fermented soybean food with many beneficial health effects. The aim of this study was to determine the in vitro apoptosis-inducing effect of the volatile components of Douchi (VCD) and to examine the relationship between anticancer effects and VCD. After treatment with 0.4, 0.8, and 1.6 mg/mL VCD for 48 h, the proliferation of human nasopharyngeal carcinoma CNE-1 cells was inhibited, and treatment with 1.6 mg/mL VCD had the highest inhibitory effect (84.6%). Treatment with 0.4 and 0.8 mg/mL VCD also showed good inhibitory effects with the apoptosis rates of 29.7% and 55.6%, respectively. The flow cytometry results showed that 36.2% of the 1.6 mg/mL VCD treated CNE-1 cells in the sub-G1 phase. Reversed transcription-polymerase chain reaction (RT-PCR) analysis indicated that VCD could significantly induce apoptosis in CNE-1 cancer cells (P < 0.05) by upregulating cysteine-aspartic acid protease (caspase)-3, caspase-8, caspase-9, Bax, p53, p21, E2F1, p73 and IκB-α expression and by downregulating Bcl-2, Bcl-xL, human inhibitor of apoptosis protein (HIAP)-1, HIAP-2 and NF-κB mRNA expression in a dose-dependent manner. VCD contained 63 chemical compounds that could potentially cause apoptosis in CNE-1 cells. These results showed that VCD had in vitro apoptosisinducing effects in CNE-1 cells, and this effect was ascribed to the complex chemical composition of VCD.
Packaging & Storage
Effect of Sugar Alcohols on Water Retention in Frozen Shrimp (Litopenaeus vannamei)
ZHANG Yangyang, ZHANG Bin, HAO Guijuan, DENG Xiaoying, TANG He
2018, 39(23):  170-175.  doi:10.7506/spkx1002-6630-201823026
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The cryoprotective and water-retaining effects of 8 common sugar alcohols on frozen peeled shrimp (Litopenaeus vannamei) were compared in this study. Sodium pyrophosphate and distilled water were used as positive and blank controls, respectively. The results indicated that soaking treatment with 30 g/L mannitol, xylitol or isomaltitol significantly reduced the pressing loss and thawing loss of frozen shrimps stored for 3 weeks at ?18 ℃ when compared with the blank control (P < 0.05). Isosorbitol, sorbitol and xylitol treatments significantly improved the cooking loss of frozen shrimps (P < 0.05). Among the sugar alcohols investigated, isosorbitol had significantly highest water-absorbing and waterretaining capacities (P < 0.05) followed by xylitol and the six others. Sensory evaluation indicated that the appearance, elasticity and color characteristics of frozen shrimps treated with xylitol or mannitol were significantly (P < 0.05) better than those of the positive and blank controls, while no significant difference was observed in odor (P > 0.05). Overall, xylitol, mannitol and isosorbitol exhibited better cryoprotective and water-retaining effects on frozen shrimps during storage and could be potentially applied to improve and guarantee the quality of frozen shrimps.
Effect of Ginger Oleoresin on Postharvest Decay and Storage Quality of Chinese Olive Fruits
CHEN Tuanwei, LU Ju, KANG Binbin, ZHANG Lingyan, LIN Hetong
2018, 39(23):  176-181.  doi:10.7506/spkx1002-6630-201823027
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Pestalotiopsis microspora is one of the dominant pathogenic fungi causing postharvest decay in Chinese olives (Canarium album (Lour.) Raeusch). In order to provide a scientific basis and practical guidance for applying ginger oleoresin in postharvest preservation and storage of Chinese olives, the effect of ginger oleoresin on postharvest decay and storage quality of Chinese olives was investigated in this study. For this purpose, ‘Changying’ Chinese olives were wounded and inoculated with P. microspore, and then injected with different doses of ginger oleoresin. Further, we examined the effect of the selected optimal dose of ginger oleoresin on disease development and quality of Chinese olives during storage at 25 ℃ for 49 days. The results showed that compared to the control treatment, ginger oleoresin remarkably suppressed disease development caused by P. microspore in Chinese olive fruits and the best effect was observed at a dose of 30 μL/mL. This treatment could significantly reduce fruit disease index and browning index (P < 0.01), retard the decrease in the contents of total soluble solids, total soluble sugars, titratalble acid, VC, total phenols and flavonoids, and maintain better fruit color and nutritional quality. From the above findings, it could be concluded that treatment with 30 μL/mL ginger oleoresin could effectively suppress disease development and maintain fruit quality during postharvest storage of Chinese olives.
Effect of Exogenous Ethylene Treatment on Endogenous Ethylene Production and Senescence of Postharvest Pleurotus eryngii
LI Chunhong, ZHANG Leigang, LUO Shufen, ZHOU Hongsheng, HU Huali, LI Pengxia
2018, 39(23):  182-191.  doi:10.7506/spkx1002-6630-201823028
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This study was carried out in order to understand the maturation and senescence mechanism of Pleurotus eryngii and its sensitivity to ethylene. The pattern of endogenous ethylene production in Pleurotus eryngii under normal temperature (20 ± 1) ℃ and 70%–80% relative humidity was investigated, and the effect of exogenous ethylene treatment (1, 10, 100 or 1 000 μL/L) on the endogenous ethylene production in postharvest P. eryngii and its senescence process was determined. The results indicated that the biosynthesis of ethylene gradually increased with the maturation of P. eryngii during postharvest storage and exhibited a peak at 12 h and 36 h of storage, respectively. Furthermore, the two peak values were increased by 12.53 and 7.57 times, respectively, when compared with the sporophores before storage (0 h). Meanwhile, exogenous ethylene treatments accelerated endogenous ethylene production in P. eryngii, delayed the endogenous ethylene production peak, increased PPO (polyphenol oxidase) and PAL (phenylalanine ammonia-lyase) activities; moreover, exogenous ethylene treatments maintained higher browning degree, promoted the increase of relative electrical conductivity and MDA (malondialdehyde) content and the degradation of soluble sugar and protein, decreased APX (ascorbate peroxidase), CAT (catalase), POD (peroxidase) and SOD (superoxide dismutase) activities, accelerated the decrease in DPPH (1,1-diphenyl-2-picryl-hydrazyl) radical scavenging capacity and total antioxidant capability (T-AOC), and maintained lower levels of total phenol and flavonoid contents. In conclusion, exogenous ethylene treatments could significantly accelerate the senescence of postharvest P. eryngii. These findings will be helpful to reveal the regulatory mechanism of ethylene on the ripening and senescence of edible mushrooms.
Effects of Pretreatment with Browning Inhibitor Mixtures and Different Freezing and Thawing Conditions on Quality of Frozen Agaricus bisporus
HU Ye, HU Qiuhui, YU Zhifang, PEI Fei, MA Ning, YANG Wenjian
2018, 39(23):  192-198.  doi:10.7506/spkx1002-6630-201823029
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In this study, in order to solve the problem of quality deterioration in Agaricus bisporus during freezing and thawing, the effects of citric acid, L-cysteine, ascorbic acid, sodium erythorbate on the browning of Agaricus bisporus were evaluated. Furthermore, we determined the effect of different freezing temperatures (?80, ?40 and ?20 ℃) and thawing temperatures (25 and 4 ℃) on some quality indexes, such as drip loss, texture characteristics, microstructure, moisture content and distribution, and peroxidase activity. The results showed that the optimal combination of browning inhibitors was 3.0 g/L sodium erythorbat, 1.5 g/L L-cysteine, 0.4 g/L ascorbic acid, and 10 g/L citric acid. The drip loss of Agaricus bisporus with the browning inhibitor mixture frozen at ?80 ℃ and thawed at 4 ℃ was 1.98%, significantly lower than that in other treatment groups. However, moisture content and texture characteristics showed a pronounced increase compared with other frozen-thawed groups. Thus, the optimal freeze-thaw temperatures were determined as ?80 and 4 ℃. This study provides a basis for developing freeze-thaw techniques for the production of frozen Agaricus bisporus products.
Effect and Underlying Mechanism of Cold Storage on Textural Properties of Cooked Monopterus albus
ZHENG Hong, SU Xianbo, MA Liang, ZHANG Xiaojie, SUN Yi, MA Mingsi, CAI Luyun, ZHANG Yuhao
2018, 39(23):  199-204.  doi:10.7506/spkx1002-6630-201823030
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The purpose of this study is to assess the effect of cold storage on textural properties of cooked Monopterus albus and to explore the underlying mechanism. Monopterus albus were stored cold for different periods before being cooked at 100 ℃ for 5 min. Cooking loss, textural properties and chemical forces were determined, and sodium dodecyl sulfatepolyacrylamide gel electrophoresis (SDS-PAGE) and Raman spectroscopic measurement were conducted. The results showed that as storage time increased, moisture loss during cooking increased, while hardness and springiness were not significantly changed (P > 0.05); cohesiveness and gumminess were significantly increased on the second and third day (P < 0.05), respectively; chewiness and resilience increased first and then decreased (P < 0.05). Hydrophobic interaction and disulfide bonds were the most important forces between various proteins in cooked Monopterus albus. Hydrophobic interactions tended to decrease gradually whereas the disulfide bonds increased initially and then decreased with increasing cold storage time. For each storage period, disulfide bond content was positively correlated with springiness, chewiness and resilience (P < 0.05). SDS-PAGE showed that protein components with molecular mass less than 30 kDa and equal to approximately 30, 37 and 60 kDa may be involved in the formation of disulfide bonds, thereby possibly affecting textural properties in cooked Monopterus albus. Raman spectroscopy analysis indicated that the hydrophobicity of tryptophan and tyrosine residues decreased, which was consistent with the change of hydrophobic interactions. The secondary structure analysis indicated the transformation of α-helix and random coil structures into β-turn and β-sheet occurred mainly during the first three days of cold storage while α-helix and β-sheet conformations were transformed into β-turn and random coil during the late storage stage, leading to a more disordered structure. Taken together, we concluded that disulfide bonds and hydrophobic interactions are the main forces between various proteins in cooked Monopterus albus, and changes in these forces can cause protein conformation to disordered, thereby leading to changes in textural properties of Monopterus albus after cooking.
Effect of Cold Shock Treatment on Reducing Chilling Injury in Eggplant and Its Relationship with Reactive Oxygen Species Metabolism
ZHANG Tingting, YAO Wensi, ZHU Huiwen, JIN Peng, XU Tingting, ZHENG Yonghua
2018, 39(23):  205-211.  doi:10.7506/spkx1002-6630-201823031
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The purpose of this study was to investigate the effect of cold shock treatment on reducing chilling injury in coldstored eggplant and to explore its relationship with reactive oxygen species metabolism. Eggplants were pretreated with icewater mixture at 0 ℃ for 10, 20, 30 or 40 min before storage for 15 d at 4 ℃. The results showed that 20 min cold shock treatment could significantly reduce chilling injury index, delay flesh browning and mitigate chilling injury symptoms. Moreover, it could also augment the activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), inhibit the production of superoxide anion radical (O2 ?·) and hydrogen peroxide (H2O2) and maintain higher levels of total phenolic content and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capability and lower levels of malondialdehyde (MDA) and cell membrane permeability. Proline and soluble sugar contents were increased after this treatment. Therefore, cold shock treatment could maintain the metabolic balance of reactive oxygen species and increase the contents of osmotic adjustment substances, thereby reducing membrane lipid peroxidation and maintaining cell membrane integrity and consequently delaying chilling injury onset.
Effects of Composite Biological Preservatives Containing Antimicrobial Peptides Derived from Casein on the Shelf-Life of Chilled Beef
HUANG Mingkun, SHI Zhenqiang, LI Zhicheng, XIA Xiaodong, SUN Yanwen
2018, 39(23):  212-220.  doi:10.7506/spkx1002-6630-201823032
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In order to extend the shelf-life of chilled beef and establish a predictive model for the determination of the shelflife, we developed and optimized an effective composite preservative containing antimicrobial peptides derived from casein, chitosan, nisin, tea polyphenols and clove essential oil using a U16(84) uniform design. Total volatile basic nitrogen (TVB-N) value, pH and total viable count were used as response variables. The results showed that the optimal combination was determined as 22.5 g/L chitosan, 0.15 g/L nisin, 9.7 g/L antimicrobial peptides derived from casein, 1.5 g/L tea polyphenols and 13.0 g/L clove essential oil. Compared with the control group, the shelf-life of chilled beef treated with the optimal composite preservative and stored at (4 ± 1) ℃ was extended by over 25 days. The interaction between antimicrobial peptides and nisin, tea polyphenols or clove essential oil, and between nisin and tea polyphenols had a significant effect on the change of TVB-N content (P < 0.01). Total viable counts of chilled beef treated with this composite preservative as a function of storage temperature (?1, 2 and 6 ℃) were fitted with the Arrhenius equation with the coefficients of determination greater than 0.91. The shelf-life (SL) prediction model developed was as follows: SL = 2.75 × 10-9 × exp (6 567.2/T). The actual shelf-life of chilled beef at 2, 4 and 6 ℃ was 61, 53 and 47 d, respectively and the relative error between the actual and predictive values less than 6%, suggesting that the model can effectively predict the shelf-life of chilled beef at ?1–6 ℃.
Effect of Precooling Treatment on Survival of Lateolabrax maculatus during Live Transportation without Using Water
ZHANG Yuhan, XIE Jing
2018, 39(23):  221-226.  doi:10.7506/spkx1002-6630-201823033
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Lateolabrax maculatus reared at 22–23 ℃ were acclimated at a cooling rate of 1, 3 or 5 ℃/h to the critical temperature 4 ℃ before live transportation for 8 h without using water. In order to establish the optimal cooling rate for reducing liver damage and increasing the survival rate during the transportation of fish, the effect of cold acclimation on liver damage in Lateolabrax maculatus was evaluated by detecting caspase-3 activity and malondialdehyde (MDA) content in liver and proprotein convertase subtilisin kexin type 9 (PCSK-9), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity in serum. The results showed that at 0 h of transportation all investigated biochemical parameters in three treatment groups were higher than in the control group. At 8 h of transportation, these five parameters were significantly lower in the 3 ℃/h cooling group than in two other treatment groups but higher than in the control group (P < 0.05). At 2 h, serum PCSK-9 activity was significantly lower in the 3 ℃/h cooling group than in the other treatment groups (P < 0.05). Liver MDA concentration and caspase-3 activity in Chinese sea bass after arousal were decreased compared to those at 8 h but were still high. In addition, serum PCSK-9 activity was increased and AST activity was increased more slowly or declined, indicating that the liver damage caused by precooling treatment could not be recovered in a short time during live transportation without using water. Therefore, Lateolabrax maculatus can be kept alive by low temperature-induced hibernation, and sea bass acclimated at 3 ℃/h cooling rate suffered less liver damage and showed a higher survival rate at 8 h of transportation. In conclusion, a cooling rate of 3 ℃/h is recommended for Lateolabrax maculatus to transported alive without using water.
Effects of Energy Metabolism-Related Enzyme Activities and Protein Oxidation on Texture Properties of Perch (Micropterus salmoides) during Superchilled Storage
HU Jiahui, XIONG Guangquan, QIAO Yu, LIAO Li, WANG Jun, WANG Lan
2018, 39(23):  227-234.  doi:10.7506/spkx1002-6630-201823034
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In order to study the relationship between the texture traits of perch and energy metabolism-related enzymes and protein oxidation during superchilled storage, we investigated the influence of three different packaging treatments (air packaging, vacuum packaging, and tea polyphenols combined with vacuum packaging) on the shear stress, microstructure, differential scanning calorimetric (DSC), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), total sulfhydryl content and energy metabolism-related enzyme (lactate dehydrogenase, Ca2+-ATPase, and Mg2+-ATPase) activities of perch during superchilled storage at ?2 ℃. The results showed that for all three groups, the shearing force, total thiol content and energy metabolism-related enzyme activities were significantly decreased with prolonged storage (P < 0.05), and a significant increase in these parameters was recorded for the third group compared with the two other groups (P < 0.05), indicating that tea polyphenols could preserve the quality of perch during superchilled storage. The SDS-PAGE and DSC analysis showed that myosin was slightly denaturated during superchilled storage for 21 days. The activities of three energy metabolism-related enzymes were positively correlated with the content of sulfhydryl groups (P < 0.05, r = 0.99), indicating that ATPase and lactate dehydrogenase activities are closely related to the degradation of myofibrillar protein, and there was also a significant positive correlation between the total content of thiol and ATPase activity and shear force (P < 0.01, r = 0.92), suggesting that myofibrillar protein oxidation could cause texture deterioration in perch.
Preparation of Nano-Ag@SiO2-Modified Polyvinylidene Chloride Coating and Its Effect on Quality Maintenance of Clean Eggs during Storage
LIANG Yanwen, YAN Wenjing, ZHAO Jianying, ZHAO Yuan, ZHAO Guofeng, ZHANG Jianhao
2018, 39(23):  235-242.  doi:10.7506/spkx1002-6630-201823035
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In this study, different amounts of nano-Ag@SiO2 were used to modify polyvinylidene chloride (PVDC) coating in order to improve the efficacy of PVDC coating in preserving the quality of clean eggs and consequently to extend their shelf life. The results showed that nano-Ag@SiO2 could significantly improve the bactericidal effect of PVDC coating on pathogens and could also stably fill in the intermolecular spaces of PVDC coating to improve its density and significantly reduce its viscosity and increase its moisture barrier properties (P < 0.05). Moreover, the addition of 0.21% (m/m) nano-Ag@SiO2 was more effective in modifying PVDC coating, and it could significantly reduce mass loss, inhibit microbial growth and preserve the freshness of clean eggs during storage. In summary, nano-Ag@SiO2-modified PVDC coating is a new packaging material for clean eggs that can extend their shelf life up to 7 weeks.
Effect of Treatment with 1-Methylcyclopropene or Ethylene Absorbent on the Quality of Hawthorn Fruits during Controlled Freezing-Point Storage
WANG Liang, ZHANG Xinxian, ZHAO Yingli, ZHANG Lixin, WANG Chunsheng
2018, 39(23):  243-249.  doi:10.7506/spkx1002-6630-201823036
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Changes in physiological indices, bioactive contents and microstructure of ‘Changkou’ hawthorn fruits treated with 1-methylcyclopropene (1-MCP) or ethylene absorbent (EA) were determined during controlled freezing-point storage. The results showed that compared to other treatments, 1.0 μL/L 1-MCP combined with controlled freezing-point storage at ?1.0 ℃ efficiently inhibited ethylene production and respiratory rate, delayed the ethylene production peak and respiratory peaks, lowered the conversion rate of protopectin into soluble pectin, maintained pulp hardness better, mitigated the degradation of flavonoids in pulp and the increase of anthocyanin content in pericarp, efficiently restricted the loss of soluble solids and titratable acid, declined mass loss percentage and browning rate, and increased marketable fruit percentage. Controlled freezing-point storage was an effective means of preserving fruit pericarp and pulp tissue structure. Overall, 1.0 μL/L 1-MCP treatment combined with controlled freezing-point storage at ?1.0 ℃ could be an appropriate method to maintain the quality of hawthorn fruits.
Effect of Tea Polyphenol on Functional Properties of Loach Myofibrillar Protein during Superchilled Storage
DOU Chuanlin, LIN Jing, DONG Wei, SHANG Yongbiao
2018, 39(23):  250-256.  doi:10.7506/spkx1002-6630-201823037
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The objective of this study was to explore the effects of tea polyphenols at different mass concentrations (0, 1, 2 and 3 g/L) on functional properties of loach (Misgurnus anguillicaudatus) myofibril protein during superchilled storage. The changes in solubility, emulsifying properties, surface hydrophobicity, sulfhydryl content and rheological properties were measured after 0, 5, 10, 15, 20, 25 and 30 days storage at ?2.5 ℃. The results showed that treatment with tea polyphenols could inhibit the decrease in solubility, emulsifying properties and sulfhydryl content and the increase in surface hydrophobicity. The rheological curves showed that tea polyphenols could enhance the gel-forming capacity of loach myofibril protein in a concentration-dependent manner. In conclusion, tea polyphenol treatment can significantly inhibit the deterioration of functional characteristics of loach myofibril protein during superchilled storage, and the best effect can be obtained with 3 g/L tea polyphenols.
Effects of Nanoemulsion Coating and 1-Methylcyclopropene on Quality Maintenance of Loquat Fruits
SUN Zhengxuan, CHEN Huiyun, YANG Huqing, SUN Zhidong, WU Yufen, LI Mengzhen
2018, 39(23):  257-262.  doi:10.7506/spkx1002-6630-201823038
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In this study, the effects of nanoemulsion coating (NC)-1, 1-methylcyclopropene (1-MCP) and NC-1 + 1-MCP treatments on the quality and physiological metabolism of white-fleshed loquat fruits during 30 days of storage at 4 ℃. Fruits treated with distilled water were used as control. The results showed NC-1 + 1-MCP had the best effect on preserving the quality of loquat fruits. At the end of storage, hardness, decay incidence and mass loss percentage but not VC content were significantly lower in the NC-1 + 1-MCP treatment group than in the other groups. NC-1 + 1-MCP treatment significantly inhibited the activity of phenylalanine ammonia-lyase (PAL) and consequently inhibiting the accumulation of lignin during storage. At the same time, NC-1 + 1-MCP treatment inhibited polyphenol oxidase (PPO) and peroxidase (POD) activity, thereby delaying pericarp browning and senescence of loquat fruits. The results showed that NC-1 + 1-MCP treatment had a better effect on loquat preservation than single treatment with NC-1 or 1-MCP.
Recent Progress in the Application of Surface Plasmon Resonance Based on Different Recognition Elements in Food Safety Detection
YAN Mengmeng, SHE Yongxin, HONG Sihui, ZHANG Chao, CAO Xiaolin, WANG Mengqiang, WANG Shanshan, ZHENG Lufei, JIN Maojun, SHAO Hua, JIN Fen, LIU Haijin, WANG Jing
2018, 39(23):  263-271.  doi:10.7506/spkx1002-6630-201823039
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Surface plasmon resonance (SPR) sensors have found a wide range of applications in various fields such as biological science, pharmaceutical development, food safety detection and environmental pollution detection owing to the advantages of high sensitivity, label-free, simplicity, low cost, and real-time monitoring. Developing recognition elements is of great significance to SPR sensors because they determine the specificity and sensitivity of SPR sensors. Herein, we review the advances made in the last decade in SPR sensors based on various recognition elements such as antibody, aptamer, molecular imprinting polymer, protein, peptide and enzyme for food safety detection. Our focus is on the features and advantages of these recognition elements. Finally, future technical challenges and prospects for the application of SPR technology in food safety detection are presented.
Advances in Understanding Key Small-Molecule Signaling Pathways of Foodborne Bacteria
WANG Feifei, FU Linglin, BAO Xingyue, LIU Changjun, ZHANG Xiaoshuang, WANG Yanbo
2018, 39(23):  272-279.  doi:10.7506/spkx1002-6630-201823040
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Food spoilage and biofilm formation by foodborne bacteria are hot topics in food science. The quorum sensing (QS) system and the secondary messenger cyclic di-guanosine monophosphate (c-di-GMP) have been reported to be involved in these phenomena. Intensive studies have demonstrated that bacteria can regulate a series of physiological processes via extracellular autoinducers and intracellular c-di-GMP, which perceive cell density and external stimulus, respectively. Considering this context, this review is focused on the QS and c-di-GMP signaling pathways and their effects on food spoilage and biofilm formation. The regulatory network between the two pathways is discussed as well. This review will be helpful to better understand the role of bacterial communication in food spoilage and biofilm formation in food system and to provide novel targets for ensuring food quality and safety.
Recent Advances in Application of Isotopic Dilution Mass Spectrometry in Food Analysis
ZHANG Hongkang, WANG Zhongyuan, YANG Qijin, SHAO Dandan, LI Xiaoyan
2018, 39(23):  280-288.  doi:10.7506/spkx1002-6630-201823041
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Isotopic dilution mass spectrometry (IDMS) is a quantitative analysis method that has been widely used in food analysis due to its rapidity, high sensitivity and accuracy. The basic principle and characteristics of isotopic dilution mass spectrometry are outlined in this article. Meanwhile, recent advances in the application of isotopic dilution mass spectrometry in food analysis in China are reviewed, and the limitations of isotopic dilution mass spectrometry in food analysis and future trends are also discussed.
Occurrence, Control and Determination of Ochratoxin A Contamination in Fruits, Nuts and Related Products
WANG Liuqing, JIANG Dongmei, WANG Yao, WANG Meng
2018, 39(23):  289-298.  doi:10.7506/spkx1002-6630-201823042
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Ochratoxin A (OTA) is a secondary metabolite produced by Aspergillus ochraceus, A. carbonarius, and Penicillium spp., which may contaminate a broad variety of fruits, nuts and related products, especially fresh grapes and grape products. OTA is highly toxic, carcinogenic, extremely stable, and difficult to eliminate. Therefore, maximum limits for OTA have been set in many countries. In this review, we summarize the current knowledge on the biosynthesis of OTA, the technologies used for OTA detection in fruits, nuts and related products, and the current status of OTA contamination and propose some countermeasures to control OTA contamination. Future prospects for rapid detection as well as green and safe prevention and control of OTA are addressed. It is expected that this review will provide a theoretical basis and guidance for highly efficient analysis and effective control of OTA contamination in fruits, nuts and related products.
A Review of the Literature on the Effect of Somatic Cell Count in Raw Milk on the Quality and Safety of Milk
SU Chuanyou, ZHENG Nan, LI Songli, QU Xueyin, ZHOU Xuewei, ZHAO Huifen, DU Bingyao, WANG Jiaqi
2018, 39(23):  299-305.  doi:10.7506/spkx1002-6630-201823043
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Increased milk somatic cell count (SCC) can alter milk composition, affect milk flavor and shorten the shelf life of milk products, and can also increase the risks of antibiotic and veterinary drug residues in milk. SCC not only can reflect the quality and safety of milk and the health of dairy animals, but also is an important indicator of the incidence of subclinical mastitis. To guarantee milk quality and safety, a maximum level has been set for SCC in milk in many countries. The impact of SCC on the quality and safety of milk, regulatory limits for SCC in raw milk in different countries, the factors that influence SCC, and SCC detection methods are reviewed in this paper.
Recent Advances in Research on Biotransformation of Polypheonls during Pu-erh Tea Pile Fermentation
Lü Haipeng, WANG Mengqi, ZHANG Yue, ZHU Yin, LIN Zhi
2018, 39(23):  306-312.  doi:10.7506/spkx1002-6630-201823044
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Pu-erh tea is a unique fermented tea produced from the sun-dried leaves of large-leaf tea species (Camellia sinensis (Linn.) var. assamica (Masters) Kitamura) in Yunnan province of China. The special sensory characteristics and beneficial health effects of Pu-erh tea arise from the multitudinous chemical changes and transformations (oxidation, polymerization, condensation and decomposition) of polyphenolic constituents in sun-dried green tea leaves during the pile fermentation process. Recent studies have revealed that structural modification of polyphenols catalyzed by microbial extracellular enzymes during the pile fermentation of Pu-erh tea, such as methylation, glycosylation and other substitution patterns is an important pathway of polyphenol biotransformation in sun-dried green tea leaves, forming a wide variety of derivatives, which have been demonstrated in previous studies for their important influence on the flavor quality and bioactivity of Pu-erh tea. These compounds are marker ingredients and quality constituents in Pu-erh tea, and are of significant research interest. This paper reviews recent advances in research on chemical modification of polyphenols during the pile fermentation of Pu-erh tea.
Recent Progress in the Development and Application of Technologies for Rapid Detection of Campylobacter
SHEN Jinling, ZHAO Lina, HAN Wei, YANG Jielin, CUI Siyu, JIANG Yuan
2018, 39(23):  313-320.  doi:10.7506/spkx1002-6630-201823045
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Campylobacter is one of the major pathogens causing human diarrhea. Therefore, rapid and specific detection of Campylobacter is of vital importance to control the transmission of this pathogen. In this article, the analytical methods at the protein and nucleic acid levels that have been applied in the rapid detection of Campylobacter are described. Furthermore, future research directions for the development of new detection technologies are discussed. This review is expected to provide useful information for the development of rapid, accurate, efficient, low-cost and high throughput detection methods for Campylobacter.
Recent Advances in Molecular Biological Research on Cordyceps militaris (L.) Link
QIAO Yuchen, LIU Guijun, WANG Ping, ZHOU Sijing, ZHENG Jie, SHANG Hongzhong
2018, 39(23):  321-328.  doi:10.7506/spkx1002-6630-201823046
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Cordyceps militaris (L.) Link is the type species of the genus Cordyceps, with anti-inflammatory, anti-oxidant, anti-tumor and immunoenhancing effects, and it can be artificially cultivated in large scale for high economic and medicinal value. C. militaris has become a hot research subject as an edible and medicinal fungus. This paper summarizes the recent progresses in research on the genetic diversity, molecular genetics, genomics, transcriptomics and proteomics of C. militaris and discusses future prospects.
Recent Advances in Chemical Components, Extraction and Pharmacological Effects of Nelumbinis Plumula
ZHAO Xiuling, DANG Yali
2018, 39(23):  329-336.  doi:10.7506/spkx1002-6630-201823047
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Nelumbinis Plumula is the dried spire and radicle of the mature seeds of Nelumbo nucifera Gaertn., a plant of the Nymphaeaceae family. It can clear away heart fire and soothe nerves, relieve cough and reduce sputum. Moreover, it has hemostatic, anti-inflammatory, hypolipidemic, anti-human immunodeficiency virus and antithrombotic effects and protects the liver, lung and kidney as well as the central nervous system. The major chemical components of Nelumbinis Plumula are alkaloids, along with flavonoids, polysaccharides and volati le oils. This paper reviews the methods used to extract the major chemical constituents from Nelumbinis Plumula and summarizes recent progress in understanding the structure and pharmacological effects of some chemical components. This review is expected to provide the basis for the development and utilization of Nelumbinis Plumula.
Recent Progress in Electrochemical Detection of Nitrite in Foodstuffs Using Graphene-Based Composite Materials
LIU Xiaopeng, HE Quanguo, LIU Jun, LI Guangli, LIANG Jing, DENG Peihong
2018, 39(23):  337-345.  doi:10.7506/spkx1002-6630-201823048
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Nitrite is a common food additive. However, excessive nitrite can react with amides in the human body to form carcinogenic nitrosamine compounds. Therefore, it is necessary to detect nitrites for food safety and human health. Compared with traditional detection methods, the electrochemical method has many advantages including easy and convenient operation with simple instruments, rapid detection, and high sensitivity. Since graphene possesses many attractive electrochemical properties (i.e. a wide electrochemical window, high electrocatalytic activity and fast electron transfer rate), graphene and its composites have become ideal electrode modifying materials for electrochemical sensors for the detection of nitrite. The dispersibility and processing suitability of graphene can be improved by modifying electrochemical sensors with graphene-based composites, thereby enhancing the electrocatalytic activity and detection selectivity. In this article, we review recent progress in the application of nano-metal particle/graphene, metal complex/graphene, metal oxide nanoparticles/graphene, polymer nanosmaterial/graphene and non-metallic nanoparticle/graphene composites for the determination of nitrite in foodstuffs, with focus on the design principles and the electrode reaction mechanism. Moreover, the detection performances of electrochemical sensors modified with various graphene-based composites are compared. This review demonstrates that the graphene-based composites are advantageous over traditional methods. Finally, the shortcomings of graphene-based composite modified electrodes are discussed, and future prospects and directions for their application in nitrite detection in foodstuffs are presented.
On the Concept of Decision-Making for Food Safety Legislation
HE Hui, REN Duanping, GUO Zeying
2018, 39(23):  346-351.  doi:10.7506/spkx1002-6630-201823049
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The concept of decision-making for food safety legislation is of great significance to food safety legislation decision-making, which is the value standard that shall be followed in food safety legislation decision-making, and is gradually formed in the practice of food safety legislation decision-making and food safety supervision. From a review of food safety work in China, we conclude that the licensing system has made positive progress in recent years, the pass rate of food safety sampling inspection has steadily increased, and the investigation and punishment of food safety violations has produced marked results. However, there is also unscientific decision-making in food safety legislation. At present, food safety legislation decision-making should follow the concept of adherence to a people-centered approach, adherence to the Party’s leadership, adherence to the principle of emancipating the mind and seeking truth from facts, adherence to reform and innovation, and adherence to the awareness of problems and problem orientation. The concept system of decision-making for food safety legislation is gradually formed in the practice of food safety work.