Volume 35,Issue 2,2019 Table of Contents

1 Study on the Inhibition of Fat Deposition of Caenorhabditis elegans by Fermented Barley β-glucan

SUN Xin-juan , XIAO Xiang , ZHAO Yan-sheng , ZHOU Xing-hua , DONG Ying

2019, 35(2):1-6. DOI: 10.13982/j.mfst.1673-9078.2019.2.001

[Abstract](580) [HTML](228) [PDF 573.60 K](705)

Abstract:
In this work, the effects of the Lactobacillus plantarum dy-1 in fermented barley β-glucan (LFBG) and raw barley β-glucan (RBG) on the fat deposition of Caenorhabditis elegans (C. elegans) were studied. The C. elegans, as the model organism, was treated with different concentrations of LFBG and RBG. The changes of fat content and possible mechanism of C. elegans were analyzed by oil red O staining and real-time PCR, respectively. The β-glucan content in LFBG and RBG reached 71.70% and 72.60%, respectively, and the molecular weight (Mw) of LFBG and RBG were 3.14×104 and 1.66×105, respectively. Compared with the model group, LFBG and RBG could significantly improve the movement behavior of C. elegans, thereby increasing the energy consumption of the nematode to reduce the fat accumulation of nematodes. The fat contents of LFBG treatment decreased by 15.83%, 22.32% and 35.67% on the fat deposition when the concentration was 25 μg/mL, 50 μg/mL and 100 μg/mL, respectively. The inhibition effect of LFBG was more significant than RBG, which showed no effect when the concentration was 25 μg/mL. The fat contents of RBG treatment decreased by 16.28% and 22.29% when the concentration reached 50 μg/mL and 100 μg/mL, respectively. LFBG could significantly down-regulate the expression of daf-16 mRNA, while RBG could up-regulate the expression of cpt-1 mRNA. In conclusion, LFBG and RBG could effectively regulate the accumulation of fat in C. elegans, through different pathways in C. elegans.

2 Differences in Volatile Profiles of Different Soy Sauce Mashes

ZHAO Mou-ming , LIN Han-yu , ZHOU Chao-hui , LU Li-ling , CHEN Zi-jie , FENG Yun-zi

2019, 35(2):7-16. DOI: 10.13982/j.mfst.1673-9078.2019.2.002

[Abstract](539) [HTML](156) [PDF 492.37 K](691)

Abstract:
The use large-scale fermenters in the place of the traditional fermentation ponds in the production of high-salt liquid-state fermented soy sauce represents an important step in the modernization of the soy sauce industry. However, the soy sauce from the fermentation pond (FPSS) tended to have more intense soy sauce flavor than the soy sauce from the large-scale fermenters (LFSS), which might be associated with the differences in the surface area of soy sauce mashes in contact with light and air. Therefore, in this study, the composition and concentrations of volatile compounds in these two kinds of soy sauce mashes were compared. The obtained results showed that some key aroma-active compounds in FPSS, such as 2-methyl-1-propanol, 3-methyl-1-butanol, 2-methyl-1-butanol, phenylethyl alcohol, phenylacetaldehyde, 3-methylbutanoic acid, 2-methylbutanoic acid, 4-ethylphenol, 4-ethyl-2-methoxy-phenol and 2-methoxyphenol, were more abundant in the top mash than in the bottom mash of soy sauce. Whereas, the key aroma-active compounds in LFSS, such as 1-octen-3-ol and methional, were more abundant in the bottom mash than in the top mash. The consistency of such differences in these compounds indicated that the formation of key aroma-active compounds in soy sauce was affected by the surface area of soy sauce mashes. Greater Maillard reaction occurring in the top soy sauce mash while yeast and lactic acid bacteria being more active in the bottom soy sauce mash could be the significant causes of the differences in the aroma-active compounds between the top and bottom mashes.

3 Study on Water Diffusion Characteristics of Taro Slices during Microwave Vacuum Drying Based on LF-NMR

CHENG Xin-feng , ZHOU Shou-biao , HANG Hua , XIAO Zi-qun

2019, 35(2):17-23. DOI: 10.13982/j.mfst.1673-9078.2019.2.003

[Abstract](578) [HTML](194) [PDF 625.18 K](592)

Abstract:
Low field-nuclear magnetic resonance (LF-NMR) was employed in this work to evaluate water mobility and distribution in taro samples during the processing of microwave vacuum drying (MVD) under different microwave intensities of 1.5, 2.0 and 2.5 W/g. Results showed that there was no constant drying rate period, and the entire microwave vacuum drying process occurred in the falling rate period. The average drying rates under microwave intensities of 1.5, 2.0 and 2.5 W/g were 0.149, 0.185 and 0.224 g/(g·min), respectively. The effective moisture diffusivity (Deff) values for MVD taro slices at different microwave intensities were 7.30×10-9、9.46×10-9、1.14×10-8 m2/s, respectively. Among the transverse relaxation time (T2), T21 (2.31~9.32 ms), T22 (10.72~49.77 ms) and T23 (57.22~705.48 ms) were corresponding to bound water, immobilized water and free water in fresh taro samples, respectively. The dramatically decreased content of free water for MVD taro was accompanied (p<0.05) by the increase in the proportion of bound water, although the content of bound water did not changed significantly (p>0.05). The proportion of immobilized water in taro samples increased, and then decreased with the drying time. The MRI results directly showed that the water-desorbing rate of outer layer in taro is equivalent to inner layer during microwave vacuum drying processing. The higher the microwave intensity, the faster relaxation signals disappear. This work obtaineded the laws of moisture diffusion in taro samples during microwave vacuum drying processing that the water diffusion and the conversion between the different components of moisture in MVD taro samples increased by the microwave intensity . It can provide a theoretical basis for industrial production of taro.

4 Effect of Raspberry Extract on Reduceing Oleic Acid-induced Fat Accumulation in HepG2 Cells

LIU Chang , ZHANG Hai-hua , CHAI Yang-yang , SONG Xing-shun , WANG Jin-ling

2019, 35(2):24-31. DOI: 10.13982/j.mfst.1673-9078.2019.2.004

[Abstract](643) [HTML](398) [PDF 634.83 K](977)

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In order to study the effect of red raspberry on human liver cell fat accumulation, the active components in the extracts of raspberry and seed were determined, and the fat accumulation model of HepG2 cells was established by oleic acid induction in vitro. The results showed that the contents of total polyphenols, flavonoid, proanthocyanidins and anthocyanins in red raspberry extract were 15.18±0.94 mg GAE/g, 1.25±0.05 mg RE/g, 20.35±1.06 mg CE/g, and 1.15±0.70 mg CGE/g, respectively. In raspberry seed extract, the contents of total polyphenols, flavonoid, and proanthocyanidins were 15.35±1.55 mg GAE/g, 11.22±0.66 mg RE/g, and 27.08±0.99 mg CE/g, respectively, and no anthocyanins was detected. Liver cell fat accumulation could be successfully induced by incubating HepG2 cells for 24 h with 1000 μmol/L oleic acid moulding agent prepared with bovine serum albumin (BSA) as solvent. Red raspberry extract could significantly reduce hepatocyte fat accumulation induced by 1000 μmol/L oleic acid. When 200 μg/mL red raspberry extract induced cells, the intracellular lipid content decreased by 25.93% and TG content decreased by 37.23% in comparison with the model group. When treated by 4 mg/mL raspberry seed extract, the intracellular lipid content was decreased by 47.12%, and TG content was decreased by 46.23% in comparison with the model group. Red raspberry extract is rich in active ingredients, which can reduce the accumulation of fat in the high-fat cell model, and has a certain preventive effect on diseases such as fatty liver.

5 Effect of High Hydrostatic Pressure Combined with Freezing Treatment on Shucking and Physicochemical Properties of Myofibrillar Protein of Penaeus vannamei

CUI Yan , XUAN Xiao-ting , LIN Xu-dong , SHANG Hai-tao , KANG Meng-li , YAO Ling-qiao , LING Jian-gang

2019, 35(2):32-39. DOI: 10.13982/j.mfst.1673-9078.2019.2.005

[Abstract](526) [HTML](221) [PDF 533.74 K](773)

Abstract:
In order to determine the effect of high hydrostatic pressure combined with freezing treatment (FT-HHP) on shucking and physicochemical properties of myofibrillar protein of Penaeus vannamei, fresh shrimps were frozen and subjected to high hydrostatic pressure processing (200, 300 and 400 MPa at ambient temperature for 1, 3 and 5 min). And the changes in sensory score of shucking efficiency, myofibrillar protein content, carbonyl content, total sulfhydryl content, surface hydrophobicity and Ca2+-ATPase activity of myofibrillar protein were evaluated. The results showed that FT-HHP is an effective method for Penaeus vannamei shucking. With combined treatment of 300 MPa (1 min) and freezing, the sensory score of shucking efficiency increased by 24.31% as compared to that in freezing samples. Compared with the fresh group, the myofibrillar protein contents, carbonyl contents and total sulfhydryl contents of myofibrillar protein had no significant differences with the treatment of FT-HHP at 200 MPa (1~3 min) and 300 MPa (1 min).However, after treatment with FT-HHP at pressure ≥300 MPa, holding time ≥3 min, the levels of myofibrillar protein oxidation significantly enhanced, and the shrimps showed cooked appearance. As the pressure and holding time increased, the levels of Ca2+-ATPase activity tended to decrease, while the surface hydrophobicity of myofibrillar protein tended to increase. Taking into account both the shucking efficiency and effect of FT-HHP on the physicochemical properties of myofibrillar protein in Penaeus vannamei, the combined treatment of 300 MPa (1 min) and freezing, which can significantly improve shucking efficiency and maintain the good quality of shrimp, was suitable to treat Penaeus vannamei. These results can provide a theoretical basis for the industrial application of FT-HHP in the shucking of Penaeus vannamei.

6 Studyies on the Microbial Profiles and Dominant Spoilage Bacteria in Sausage during Different Storage Periods

TENG An-guo , ZHANG Qin , JIANG Yi , LI Bing-xin

2019, 35(2):40-46. DOI: 10.13982/j.mfst.1673-9078.2019.2.006

[Abstract](543) [HTML](170) [PDF 588.66 K](953)

Abstract:
In this study, the smoked sausage in a natural casing was investigated through extracting DNA from fresh sausage and spoiled sausage for comparison on the microbial profiles by high-throughput sequencing technology and determination of dominant spoilage bacteria. Results showed that the abundance and uniformity of spoilage sausage were lower than those of fresh sausage. At the genus level, the bacteria with the highest abundance was Staphylococcus (90.64%) in fresh sausage, whilst Weissella (65.93%) and Staphylococcus (33.79%) in spoiled sausage had the highest and second highest abundance, respectively. At the species level, Staphylococcus equorum and Staphylococcus vitulinus had the highest abundance in fresh sausage (25.59% and 18.01%, respectively), whilst Weissella viridescens (46.04%) and Weissella cibaria (19.68%) were the most abundant in spoiled sausage. These results indicated that the microbial profile of spoilage sausage differed significantly from that of fresh sausage, and the dominant spoilage bacteria in spoiled sausage was Weissella viridescens (which could proliferate greatly during sausage storage thus would dominate the spoiled products). Accordingly, Weissella viridescens should be eliminated during the production process to prolong the product shelf life and improve product quality.

7 Change of Free Sugars and Amino Acids in Fresh Corn Juice during Autoclaving

NIU Li-ying , LIU Chun-ju , LI Da-jing , SONG Jiang-feng , LIU Chun-quan

2019, 35(2):47-53. DOI: 10.13982/j.mfst.1673-9078.2019.2.007

[Abstract](654) [HTML](196) [PDF 559.93 K](907)

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Aimed at verifying the changes of taste-related components in fresh corn juice during autoclaving, milk-stage sweet corn, waxy corn and common corn juice were processed and the changes of sucrose, fructose, glucose and 19 free amino acids contents were determined using HPLC. Results showed that sweet corn juice had the highest sucrose content 11.94~18.09 mg/mL, while the waxy corn juice had the lowest value 0.12~0.34 mg/mL. During the sterilization, the fructose and glucose content in waxy corn and common corn juice decreased with the extending time, however, all the sugars in sweet corn juice increased first and then decreased. Sweet taste amino acids and umami amino acids were the main amino acids in the corn juices, and they contribute 68.77%~80.20% of the total amino acids. Moreover, the relationships of the 19 amino acids during sterilization were displayed using heat maps and principle component analysis (PCA) profiles. The changes of amino acids in sweet corn juice were similar to those in waxy corn juice. Both of them had six amino acids that increased during sterilization and showed significant correlations, which was different in common corn juice. These results would contribute to fresh corn juice quality improvement during processing.

8 Starter and Actinidin Promote Protein Degradation of Horse Meat Fermented Sausage

YUSUFU Sulaiman , AERZUGULI Abuduwaili , BATUER Abulikemu

2019, 35(2):54-60. DOI: 10.13982/j.mfst.1673-9078.2019.2.008

[Abstract](613) [HTML](285) [PDF 623.49 K](742)

Abstract:
In order to improve the quality of horse meat fermented sausage, starter and actinidin were added to promote the fermentation mature and degradation of muscle protein. Fresh horse meat and horse fat were chose as raw materials. Three test groups were designed. One was the control group and the other two groups were the treatment group. The two treatment groups added 2% starter and 0.05% actinidin, and fermented under the corresponding conditions. the contents of total nitrogen, non-protein nitrogen were detected. The degradation of muscle protein was analyzed by SDS-PAGE. Results showed that the total nitrogen content of each group (0 d) was about 3.09 g/100 g. After processing (28 d), the total nitrogen content of control group (CK group), fermentation group (group A) and actinidin group (group B) were 3.41 g/100 g, 3.85 g/100 g and 4.15 g/100 g, respectively, indicating that the total nitrogen content increased significantly. The effects of starter and actinidin on protein degradation were significant. The non-protein nitrogen contents of the CK group, A group, B group on 28 d were 0.42 g/100 g, 0.52 g/100 g, 0.65 g/100 g respectively. Compared with 0 d (0.22 g/100 g), the non-protein nitrogen content of CK group increased by 1.9 times, group A increased by 2.4 times, group B increased by 2.9 times. Results of SDS-PAGE electrophoresis showed that the sarcoplasmic protein of group A and group B gradually degraded during the whole processing, and the macromolecular bands changed significantly. The starter significantly promoted the degradation of sarcoplasmic protein and myofibrillar protein of horse meat fermented sausage. Actinidin can also promote the sarcoplasmic protein degradation and have better effect than starter, but it has little effect on myofibrillar protein.

9 Evaluation of Properties and Quality of Commercial White Zein Products

XU Bin , SHI Jia-chen , HAN Ji-hua , XUE Ding-ping , LI Yun-tong , LI Bo , WU Qi-fei

2019, 35(2):61-67. DOI: 10.13982/j.mfst.1673-9078.2019.2.009

[Abstract](520) [HTML](142) [PDF 546.24 K](772)

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In order to fill the gap in thinspection standards for the production and application of white zein products in China, this research evaluated comprehensively the quality of commercial white zein via chemically and instrumentally analyzing the chemical composition, heavy metal content, pigment content, zein solubility, molecular weight distribution and protein structure. The results showed that the contents of protein and heavy metals in the white zein met the requirements of the Chinese Pharmacopoeia and National Standards. The pigment content of white zein was only 22.18% of that of yellow zein, and there was no obvious denaturation in white zein. Compared with yellow zein, the white zein had a similar molecular weight and tertiary structure but altered secondary structure (α-helix content, increased from 56.37% to 60.42%; β-sheet content, decreased from 10.51% to 5.92%). These results were mainly due to the decolorization treatment which had reduced the contents of β-zein, pigment and denatured protein whilst increased the content of α-zein. Therefore, a multi-level quality evaluation system should be established by manufacturers and users according to the actual conditions. This study provides a reference for theoretical research related to zein.

10 Preparation of Aspergillus niger Mycelium-chitosan Biosorbent and Its Adsorption Characteristics for Cr (VI)

XIA Yuan-tao , GUO Qian , QIN Nan-nan , TANG Yu , TAN Qiu-jing , SUN Hui-jie , GAO Ya-ting , GUO Qing , ZHOU Gui

2019, 35(2):68-73. DOI: 10.13982/j.mfst.1673-9078.2019.2.010

[Abstract](530) [HTML](234) [PDF 598.68 K](725)

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The adsorption characteristics of Aspergillus niger mycelium-chitosan for Cr(VI) were studied. The waste Aspergillus niger mycelium and chitosan were used as raw materials for the preparation of Aspergillus niger mycelium-chitosan composite biosorbent for Cr(VI), through cross-linking with epichlorohydrin and then immobilizeation with sodium tripolyphosphate. The effects of pH and loading amount of Aspergillus niger mycelium-chitosan on the adsorption of Cr(VI). The experimental results showed that the adsorption rate of Cr(VI) was up to 92.30% when the loading amount of Aspergillus niger mycelium-chitosan was 0.5 g, and reached 84.32% when pH=6. Analysis of kinetic data revealed that the adsorption process of Aspergillus niger mycelium-chitosan biosorbent on Cr(VI) conformed to the quasi-secondary kinetic model (R2=1), and in the meantime, the Freundlich isotherm model (with the maximum adsorption capacity reaching 108.23 mg/g); Scanning electron microscopy (SEM) and infrared spectroscopy (IR) confirmed that the adsorption reaction occurred on the surface layer of the Aspergillus niger mycelium-chitosan adsorbent, involving mainly -OH and -COOH functional groups; The above results showed the good performance of Aspergillus niger mycelium-chitosan towards Cr(VI), which is environmentally friendly and has broad application prospects.

11 Analysis of Rumen Smooth Muscle Myofibrillar Protein Characteristic and Quality Changes in Yak Beef Cattle

LIU Hui , YU Qun-li , ZHU Yue-ming , ZHANG Wen-hua , BO Wen-xi , HAN Ling

2019, 35(2):74-81. DOI: 10.13982/j.mfst.1673-9078.2019.2.011

[Abstract](474) [HTML](222) [PDF 786.92 K](586)

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Law of change of the characteristic and quality of rumen myofibrillar proteins in yak and beef cattle were investigated in this study in order to provide a theoretical reference for the in-depth study of smooth muscles. Taking the rumen of yak beef cattle as the research object, the changes of water loss rate, cooking loss, shearing force, myofibril fragmentation index(MFI), protein solubility, surface hydrophobicity and microstructure were determined during refrigeration at 4 ℃.The results showed that, throughout the refrigeration process, the water loss rate, cooking loss, MFI and surface hydrophobicity of the two rumen showed an upward trend, which rose to the maximum on the 7th day. The shear force and protein solubility showed a downward trend. The rumen shear force, total protein solubility and myofibrillar protein solubility of yak decreased to a minimum of 5.54 kgf, 314.19 mg/g, and 116.37 mg/g, respectively, on the 7th day. The rumen shear force of beef cattle showed the minimum value of 7.82 kgf on the first day and the total protein solubility and sarcoplasmic fibrin solubility decreased to their minimum values of 368.57 mg/g and 221.75 mg/g, respectively, on the 7th day. The myofibrillar protein solubility decreased to a minimum of 139.21 mg/g on the 5th day. The fascia and endomysium showed a scattered arrangement with larger gaps between the muscle fiber bundles becomes. In conclusion, the difference in the regularity of the two rumen quality changes may be caused by the difference in muscle fiber structure and protein solubility.

12 Effect of Adding Green Wheat Flour on the Dough of Steamed Bread and Structure of Its Gluten Protein

ZHANG Kang-yi , KANG Zhi-min , WANG Ji-hong , GAO Ling-ling , WEN Qing-yu , GUO Dong-xu

2019, 35(2):82-88. DOI: 10.13982/j.mfst.1673-9078.2019.2.012

[Abstract](580) [HTML](237) [PDF 625.52 K](677)

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Steamed bread was made using steamed bread specialized flourr and green wheat flour. Analytical instruments such as laser confocal microscope and rapid visco analyser (RVA) and fourier transform infrared (FT-IR) spectroscopy were used to examine the impacts of adding green wheat flour in different amounts (0%~20%) on the characteristics of bread dough, gelatinization properties, microstructure and gluten protein secondary structure. The results showed that the increase of the amount of green wheat flour caused decreased wet gluten content and gluten index, reduced pasting temperature and peak viscosity, shortened gelatinization processing time, decreased dough stability time (from 6.18 to 4.92 min), reduced flour quality index (by 18), weakened gluten strength and tolerance, reduced tensile area, elasticity, maximum tensile resistance of dough at the 135th min, gradual appearance and uneven distribution of voids in the gluten network structure , and shift of individual absorption peaks of gluten protein, and increased beta-sheet and alpha-helical structure contents. In summary, addition of green wheat flour could change dough properties and gluten structure, which may be the main cause of decreased final product quality.

13 Study of Interaction Mechanism between Tannic Acid Complexing Magnesium and DNA

XIE Cai-ling , SHI Ze-yi , WEI Yu-ru , JIN Li-e

2019, 35(2):89-93. DOI: 10.13982/j.mfst.1673-9078.2019.2.013

[Abstract](655) [HTML](277) [PDF 493.35 K](1178)

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Tannic acid (T-A) had the antimicrobial resistance and oxidation resistance. Magnesium ions played an important role in physiological regulation. Tannic acid complexing magnesium (T-Mg) was prepared by complexation reaction with tannic acid and magnesium chloride. In order to further understand some effects of T-Mg, the interactive effect between tannic acid complexing magnesium and DNA has been investigated by electronic absorption spectroscopy, fluorescence spectroscopy, viscosity and thermal denaturation methods in simulated in vivo environment. With the increasing concentration of DNA, the ultraviolet spectrum of T-Mg-DNA system showed a hypochromic effect and a little red shift, and the maximum hypochromism was 1.82%. When the concentration of DNA was increased to a certain value, the hyperchromic effect was observed and the maximum hyperchromism was 5.2%. In an aqueous buffer solution (pH=7.4, at 25 ℃), the maximum absorption wavelength of T-Mg-DNA system was 222 nm. The binding ratio of T-Mg and DNA was n (T-Mg): n (DNA)=5.88:1, and the corresponding binding constant was 6.20×107 L/mol. An increasing fluorescence was observed in T-Mg-DNA system, and the intensity of fluorescence increased 2.14 times, which resulted from that T-Mg inserted into the base pairs of DNA. The results of viscosity and thermal denaturation indicated that addition of T-Mg can reduce the relative viscosity of DNA and increase thermal denaturation temperature. These findings further confirmed that T-Mg can bind with DNA mainly by partial insertion, and the presence of magnesium ions can promote the interaction between T-Mg and DNA.

14 Comparison of Effects of Diatomite Loaded Eugenol Sustained Release on Quality of Different Strawberry Varieties

ZHANG Li-hui , QIAO Yu , HU Yang , CHEN Xue-ling , WANG Chao , WANG Jun , WANG Lan , LIAO Li

2019, 35(2):94-101. DOI: 10.13982/j.mfst.1673-9078.2019.2.014

[Abstract](569) [HTML](412) [PDF 829.54 K](607)

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Eugenol was attached to diatomite to study the preservation effect of four strawberry varieties (Jingyao, Jingyu, Sweet Charlie and Ningfeng) under different slow-release treatments. Results showed that the preservation effect for Jingyao strawberry was better than that for Jingyu, Sweet Charlie and Ningfeng strawberries. The shelf life of the strawberries was longer. The quality of the strawberries was in the order of Jingyao, Sweet Charlie, Ningfeng and Jingyu. Eugenol slow-release could inhibit strawberry fruit spoilage, postpone fruit quality loss and decrease the contents of soluble solids, titratable acids, reducing sugars and Vc, and inhibit the increase of MDA content and the decrease of SOD, POD, CAT and other antioxidant enzymes during cold storage. The decomposition rate and weight loss rate were 31.50% and 1.33% respectively. The contents of soluble solids, titratable acids, reducing sugar and Vc were 8.83%, 0.577%, 5.72% and 31.46 mg/100 g respectively. The contents of MDA were 23.11 nmol/g, SOD, POD and CAT activities were 261.68 U/mL, 1.65 U/mg, 52.49 U/g, respectively. In conclusion, the slow-release treatment of diatomite with eugenol has a certain preservation effect on strawberries, and there are certain differences among different varieties of strawberries.

15 Effect of Silicon Window Packaging on Storage Quality of Okra

ZHU He , WU Jian , XING Yan-xia , CHANG Gui-fang , WU Xiao-xia , LIU Sheng-gang , LAN Cai-hong , YUE Feng-li

2019, 35(2):102-108. DOI: 10.13982/j.mfst.1673-9078.2019.2.015

[Abstract](636) [HTML](309) [PDF 510.72 K](781)

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In order to investigate the effect of different sizes of silicon window packaging bags on preservation of okra, post-harvest okra was treated with PVC bags with different sizes of silicon windows (blank group, 6 cm2, 8 cm2, 10 cm2). The sensory quality (decay, rust spot, hardness, color) and physical and chemical indexes (electrical conductivity, Vc, L*) of okra were analyzed. Results showed that the maximum respiratory intensity of okra was found at 10 d at 4 ℃. Modified atmosphere packaging with silicon window can effectively improve the sensory quality of okra during postharvest storage. When treated for 15 days (80.52%, 84.22%, 86.34%) and 20 days (75.92%, 79.36%, 78.26%), there were significant differences between 6 cm2 and 8 cm2, 10 cm2 treatments (p<0.05). These results were significantly correlated with CO2 concentration, O2 concentration, conductivity and L* (p<0.05). The electrical conductivity of tissues was effectively inhibited and L* was increased by gas concentration, which could significantly improve the sensory quality of Okra during storage. From the storage effect, when stored at 4 ℃, PVC bags (30 cm×40 cm, 46 μm) were heated to 8 cm2 (0.7 mm thick) to minimize the spoilage rate of okra after harvest, thus prolonging the shelf life of okra.

16 Preparation and Physicochemical Properties of Glutaric Acid-cassava Starch Esters

ZHANG Ben-shan , LIANG Yi-chao , MA Xi-chun

2019, 35(2):109-117. DOI: 10.13982/j.mfst.1673-9078.2019.2.016

[Abstract](425) [HTML](166) [PDF 906.04 K](633)

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In this paper, aqueous glutarate acid cassava starch esters (AGAC) and ethanolic glutarate acid cassava starch esters (EGAC) were prepared and characterized by FTIR, XRD and SEM. The viscosity, transparency, rheological properties, freeze-thaw stability, salt resistance and other physicochemical properties of AGAC and EGAC were studied. The results of microscopic characterization showed that the glutaric acid groups were successfully incorporated into the two esterified starch molecules, with their crystal structures remaining unchanged and the overall structure not greatly affected. Analysis with the Brabender viscometer revealed that the peak viscosity of AGAC increased, while the gelatinization temperature is significantly lowered. The gelatinization temperature of EGAC decreased along with greatly increased peak viscosity , although the viscosity stability was not improved. The transparency, freeze-thaw stability and shear resistance of AGAC paste and EGAC paste were greater than those of the original starch, with AGAC and EGAC having lower salt resistance than the original starch, that is, their thermal paste stability and salt resistance had not been improved. EGAC had greater transparency than the original starch but smaller than AGAC, with the freeze-thaw stability and shear resistance slightly better than that of AGAC and original cassava starch. After the introduction of glutaric acid group, the transparency, freeze-thaw stability, stability and shear resistance of cassava starch have been improved to some extent.

17 Study on Fish Scale Gelatin Extracted by Gradient Increasing Temperature and Its Physicochemical Properties

WU Xiao-yang , XIONG Shan-bai , YOU Juan , LIU Ru , CHEN Jia-ping , HU Yang

2019, 35(2):118-125. DOI: 10.13982/j.mfst.1673-9078.2019.2.017

[Abstract](604) [HTML](207) [PDF 935.17 K](753)

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Gelatin was extracted from grass carp (Ctenopharyngodon idella) scales under the conditions (60 ℃~80 ℃, 6 h) determined by single-factor tests. The physicochemical properties of gelatin extracted by the methods of gradient increasing temperatures (60 ℃~70 ℃~80 ℃)were studied, with gelatin extracted by constant temperature extraction method(60 ℃, 70 ℃ and 80 ℃) and commerical gelatin as control. SDS-PAGE showed that the gelatin obtained by gradient increasing temperature had a higher molecular weight (130~250 ku) and a higher gel strength than the commercial gelatin and the control group. FT-IR spectra showed that the gelatin obtained by the gradient increasing temperature had a typical amide band of gelatin. The sol-gel point and thermal denaturation temperature for the gelatin extracted by gradient increasing temperature were between 60 ℃ and 80 ℃, but the extraction rate and gel strength were relatively high, the ash content was less than 0.20%, and the fat content was less than 0.60%. In summary, the method of gradient increasing temperature can be used to extract gelatin with high extraction rate and good quality, and has a good application prospects.

18 Identification of a Microorganism Strain Isolated from the Fermented Sausage by 16S rDNA Sequence Analysis and Effect of Antibacterial Peptide Surfactin on Spore Inactivation

HUANG Xian-qing , MENG Jing-nan , SONG Lian-jun , QIAO Ming-wu

2019, 35(2):126-133. DOI: 10.13982/j.mfst.1673-9078.2019.2.018

[Abstract](537) [HTML](245) [PDF 751.88 K](682)

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To control the spoilage of fermented sausages after sterilization and assure safety of fermented sausage were, the microbes in spoiled sausages were detected and a microorganism strain B1 was isolated from the commercial fermented sausage. 16S rDNA sequence analysis showed that the B1 strain belongs to Bacillus cereus. The effect of antibacterial peptide surfactin on the spore growth curve and the effects of two salts NaCl and Na2HPO4·12H2O on surfactin inactivation of spore were studied. No significant inactivating effect of surfactin with different concentrations (20~35 μg /mL) on the spores was found. However, the combined use of surfactin (50 and 100 μg /mL) and NaCl (3%, 5% and 9%) showed inactivation effects. The combined use of surfactin with Na2HPO4·12H2O had no such effect.

19 Mitigating Protein Denaturation of Surimi via Immersion-freezing Using Water-soluble Soybean Polysaccharide(s)

GAO Wen-hong , HOU Rui , ZENG Xin-an

2019, 35(2):134-140. DOI: 10.13982/j.mfst.1673-9078.2019.2.019

[Abstract](645) [HTML](192) [PDF 493.53 K](642)

Abstract:
The effects of water soluble soybean polysaccharide (SSPS) on the freezing efficiency and protein denaturation of surimi were investigated by immersion freezing. The fresh grass carp (Ctenopharyngodon idellus) surimi was used as the raw material. The effect of SSPS addition (1%, 3% and 5%) on the immersion-freezing process of the surimi were firstly studied. Results showed that the characteristic freezing time of the surimi with 3% SSPS was the shortest, and the myofibrillar protein content was the highest after a 14-day frozen storage. Over the 8-week frozen storage, the protein denaturation of surimi was evaluated by measuring the Ca2+-ATPase activity, total sulphydryl content, active sulphydryl content and salt extractable protein content. After 2 weeks of frozen storage, all these four evaluation indices of the treated surimi samples were significantly higher than those of the control surimi, with 3% SSPS providing the greatest cryoprotective effect on protein denaturation. After 8 weeks of frozen storage, the Ca2+-ATPase activity, total sulphydryl content, active sulphydryl content, salt extractable protein content of the myofibrillar protein for the surimi treated with 3% SSPS was 0.35 μmol (pi)/[mg (protein)·min], 3.41×10-5 mol/g protein, 2.37×10-5 mol/g protein, and 41.74 mg/g, respectively, which were increased by 16.87%, 14.94%, 18.10% and 17.35%, respectively, compared to the control surimi. The results indicate that SSPS addition can significantly increase the freezing rate of surimi, mitigate the protein denaturation during frozen storage, thus, SSPS can be used as a low-sweet cryoprotectant for surimi proteins.

20 Analysis of Delphinin and Preparation of Delphindin from Purple Eggplant Peel

JIANG Xiao-lan , FU Zhou-ping , SHI Yu-feng , CHENG Lin , LIU Ya-jun , GAO Li-ping , XIA Tao

2019, 35(2):141-148. DOI: 10.13982/j.mfst.1673-9078.2019.2.020

[Abstract](653) [HTML](184) [PDF 664.34 K](926)

Abstract:
In this work, the low price peel of purple eggplant was used as material to obtain expensive high purification delphinidin monomer. The anthocyanin in purple eggplant peel was qualitatively analyzed by spectrum and mass spectrometry, and 4delphindins were identified. Then the optimized conditions for extraction delphinidin were investigated. Result showed that optimal extraction solvent was 60% ethanol with 1% hydrochloric acid; ratio of solid to liquid was 1:20. AB-8 macroporous resin which eluted with ethanol was used for initial purification of anthocyanin, the concentration of 30% ethanol elute was the optimal, and the UV absorption value of 530 nm at this concentration was 0.49. Subsequently, the delphinidin glycoside was acid hydrolyzed, and delphinidin aglycone was purified by AB-8 macroporous resin and C-18 resin. Finally, delphinidin powder with purity more than 98% was obtained. It provides a practical method for separating and purifying delphinidin pigments.

21 Influence of Different Primary Process on the Quality of Arabica Coffee in Yunnan Province

CHEN Yun-lan , CHEN Zhi-hua , JIANG Kuai-le , DAO Bin , LI Xue-lin

2019, 35(2):149-156. DOI: 10.13982/j.mfst.1673-9078.2019.2.021

[Abstract](626) [HTML](373) [PDF 7.11 M](1092)

Abstract:
In order to excavate high-quality Yunnan fine coffee, red and ripe coffee cherry of Catimor series in Nandaohe, Puwen, Yunnan Province were chosen as test materials, and six different primary processing methods such as non-soaking fermentation with pectin (fresh Fruit Fermentation and water-washing dry fermentation, pulped natural, black honey and dry red honey) and soaking fermentation (triple water-washed fermentation and washed fermentation) were conducted to explore the effects on the content and density of crude protein, crude fat and caffeine of raw beans. The sensory flavor of roasted beans was analyzed by fuzzy mathematics. The results of sensory evaluation showed that the sensory quality of coffee treated with black honey and pulped natural were the best, with a comprehensive score of 5.49 and 5.44, respectively, which was "excellent". The sensory quality of coffee beans treated with triple water washed fermentation was the worst, with a comprehensive score of 3.37, which was "medium". The sensory quality of coffee processed with dry red honey scored 3.85, which was "good". The comprehensive sensory quality score of fresh fruit fermentation, dry-washing fermentation and water-washed fermentation was respectively 3.72 and 3.70, which was "Satisfactory". Physical and chemical results showed that the crude protein, crude fat and caffeine contents of four kinds of processed coffee raw beans with pectin non-immersion fermentation were higher than those of two kinds of immersion fermentation processing; the influence of different initial processing technology on the density of coffee raw beans was not significant.

22 Inhibitors of Polyphenol Oxidase and Peroxidase in Olive and Their Thermal Inactivation Kinetics

WU Qian , YU Yuan-shan , LIU Shu-mei , XIAO Geng-sheng , XU Yu-juan

2019, 35(2):157-162. DOI: 10.13982/j.mfst.1673-9078.2019.2.022

[Abstract](638) [HTML](299) [PDF 9.16 M](1096)

Abstract:
The effects of seven inhibitors (sodium sulfite, alum, O-isoascorbic acid, EDTA-2Na, CaCl2, sodium polyphosphate and disodium citrate) on the activities of polyphenol oxidase and peroxidase in olive were examined in this study. The high-temperature deactivation kinetics of polyphenol oxidase (PPO) and peroxidase (POD) in olive fruits were analyzed using a two-stage model. The results showed that oxidative decomposition of phenolic compounds in Canarium album L. was associated with activities of POD and PPO. O-isoascorbic acid and disodium citrate disodium could the most powerful inhibitors against PPO and POD in olive under certain environmental conditions, e.g. at 0.20g/L, they could deactivate PPO and POD enzyme completely. The blanching time and temperature influenced greatly the activities of PPO and POD in olive fruits. The increase of blanching time and temperature led to an initial decrease in the activities of PPO and POD followed by a plateau. Therefore, the high-temperature deactivation process of PPO and POD in olive could be described using a two-stage model.

23 Effects of Different Treatments on Morphology of Citrus Fibers

ZENG Wei-qi , LIAO Jing-song , QI Jun-ru

2019, 35(2):163-170. DOI: 10.13982/j.mfst.1673-9078.2019.2.023

[Abstract](892) [HTML](257) [PDF 36.19 M](748)

Abstract:
In this study, the differences in the basic composition and physical properties (water holding capacity, oil holding capacity and swelling property) among the three types of citrus dietary fibers (DFs) (AQ-Plus (No. 1), Fiber-Star (No. 2), and DFs extracted in our laboratory (No. 3) were investigated. The effects of high pressure homogenization and ultrasonic treatment on the morphological characteristics of the three citrus DF suspension solutions were investigated by determining their particle size, zeta potential, apparent viscosity and micro-structure. The experimental results showed that No. 1 had better water holding capacity (21.58 g/g), oil holding capacity (14.29 g/g) and expansibility (27.46 mL/g) attributed to its higher cellulose (38.02±1.61 g/100 g) and hemicellulose (29.56±0.63 g/100 g) contents, with No. 2 ranked the second and No. 3 the worst. After high pressure homogenization (30 MPa, 60 ℃), the three types of citrus fibers had decreased particle size with significantly increased viscosity and improved zeta potential. With the increase of ultrasonic treatment time, the particle size of three kinds of citrus fibers decreased and their apparent viscosity increased. During the treatment of 0~5 min, the absolute value of the zeta potential of the three citrus fibers suspensions increased significantly with the increase of the ultrasonic treatment time. Further increase of the ultrasonic treatment time, the zeta potential of the three citrus fibers suspensions did not change significantly.

24 A Method to Remove Glycidyl Esters after Refining by Adsorbent Materials and Its Kinetics

WANG Ge-ping , LIU Guo-qin , LIN Yun-wei , YIN Shi-qin

2019, 35(2):171-178. DOI: 10.13982/j.mfst.1673-9078.2019.2.024

[Abstract](594) [HTML](255) [PDF 19.51 M](802)

Abstract:
A way to remove glycidyl esters (GEs) by adsorbent materials after refining was studied. Results showed that all the adsorbent materials chose in this work had a positive effect on the removal of GEs. Among these, AC1 had the best adsorption capacity, and GEs contents was decreased from 3.77 mg/kg to 0.15 mg/kg after the treatment with AC1. Its adsorbent rate was 95.92%. Adsorbent conditions also had great influences on adsorption efficiency. The most suitable amounts of adsorbent was 1%~5%, and the optimal absorption time and temperature were 30 min and 80~100 ℃, respectively. Results also showed that there were no adverse effects but even a slight improvement for oil quality after adsorption, and the induction time of palm oil treated with AC1 was increased to 19.35 h. In addition, by using adsorption kinetics to study the absorption mechanism of AC1 and KD, both materials accorded with the pseudo-second-order kinetics, indicating that they all happened to chemical adsorption, not just physical adsorption.

25 Comparative Analysis of Different Drying Methods on Physicochemical Properties of Yam Slice

LI Yan-xun , ZOU Jin-hao , GUO Shi-yin , SU Xiao-jun , WANG Feng , LI Yan , LI Qing-ming

2019, 35(2):179-185. DOI: 10.13982/j.mfst.1673-9078.2019.2.025

[Abstract](586) [HTML](293) [PDF 7.56 M](941)

Abstract:
Effects of different drying methods (hot air drying, infrared drying and infrared-hot air drying) on physicochemical properties, antioxidant capacity and pasting properties were investigated. The rehydration rate, color, browning degree, bioactive components, antioxidant capacity, in vitro digestibility, microstructure and pasting properties were analyzed. Results indicated that there were no significant difference in color, browning degree, rehydration rate, reducing sugar and flavonoids content of yam dried with different drying methods (p>0.05), but there have obvious difference in the microstructure and pasting properties. Compared to hot air drying and infrared drying, higher content of flavonoids (0.29%) and allantoin (0.95%) were retained in infrared-hot air drying products, and the higher antioxidant capacity, DPPH scavenging ability and in vitro digestibility (61.64 mmol/L, 7.73% and 25.59%, respectively) were obtained. Therefore, infrared-hot air drying could be a more promising technique to develop the dried products of yam slice.

26 Study on Optimization of Enrichment of Staphylococcus aureus by Bare Magnetic Particles

WU Jun , LU Li-xia , LIU Yuan-jian , LIN Li-jun , XIONG Xiao-hui

2019, 35(2):186-192. DOI: 10.13982/j.mfst.1673-9078.2019.2.026

[Abstract](549) [HTML](192) [PDF 687.86 K](796)

Abstract:
The adsorption efficiency of bare magnetic particles for different concentrations of Staphylococcus aureus and for mixed bacteria was studied. And the method was applied to the detection of S. aureus in beef samples. The quantity of beads, the broth volume and the reaction time were optimized for enrichment the bacteria, to examine if the method of Real-Time Fluorescent Quantitative PCR is suitable for measuring the content of bacteria. The results showed that the bare magnetic particles had high adsorption rate to S. aureus in the broth, with the content of 102 ~107 cfu/mL in the culture broth. The adsorption rate was over 95%. The DNA from the bacterium cells enriched by 10mg beads and 5mL culture broth for 10 minutes could be detected by Fluorescent Quantitative PCR. The DNA extracted from S. aureus was detected by Fluorescent Quantitative PCR after enriched by beads in beef broth at the concentration of 102 cfu/mL. Moreover, the DNA extracted from S. aureus was tested after enriched by beads from the mixture broth with Escherichia coli. The method could be used for enrichment and detection of S. aureus in food.

27 Effects of Different Heat Treatments and Storage Conditions onQuality of Blend Oil

WANG Zhen-jie , ZHAO Lei , XUE Peng , ZHANG Feng-xiang

2019, 35(2):193-201. DOI: 10.13982/j.mfst.1673-9078.2019.2.027

[Abstract](517) [HTML](437) [PDF 28.15 M](792)

Abstract:
The effects of different treatment conditions on oil quality were studied by using acid value (AV), peroxide value (POV), fatty acid composition and rheological properties. Under different treatment conditions, both AV and POV showed an increasing trend with time. The AV and POV of the high temperature cooking group and the light storage group above 200 ℃ were higher than those of the microwave treatment group and the high temperature storage group, respectively. With the increase of cooking temperature and illumination, the AV and POV increased rapidly, and their highest values were reached under the processing conditions, 1.17 mg/g and 22.75 mmol/kg, respectively; treatment time and treatment temperature, heat treatment method and light had an effect on fatty acid content, and the change trend was not nearly the same. Long-term treatment at high temperature reduced the content of oleic acid and linoleic acid. After treatment at 300 ℃ for 20 min, the content of oleic acid and linoleic acid decreased from 38.94% and 31.46% to 37.76% and 30.53%, respectively, while the content of linolenic acid increased from 0.26% to 0.28%, and the content of EPA and DHA polyunsaturated fatty acids also increased. For the long-term storage under high temperature and light conditions, the above unsaturated fatty acid content was reduced; the rheological properties of the oil after different conditions were not changed with the change of shear force for the high temperature cooking group and the microwave group above 200 ℃. The viscosity of fat increased with the increase of treatment time, and then decreased. The viscosity of the oil in the storage group increased with the treatment time.

28 Optimization of Enzymatic Modification of Steviosides by Alpha-amylases

LI Le , YUAN Ying , MA Shuang

2019, 35(2):202-208. DOI: 10.13982/j.mfst.1673-9078.2019.2.028

[Abstract](476) [HTML](473) [PDF 2.57 M](884)

Abstract:
In order to improve taste quality, enzymatic modification of stevia by grafting glucose was investigated using soluble starch as glucose donor. The hydrolysis was catalyzed by acid-resistant mesophilic α-amylase, whose trade name is Taka-diastase, that was screened from three different α-amylases. Using stevioside conversion rate as an indicator, the enzymatic processes were optimized and the optimum conditions obtained were donor starch concentration 100 g/L, substrate ratio 1:10 (m/m), reaction temperature 60 ℃, and enzyme concentration 1.50 U/mL. The conversion rate of the modified stevioside was determined as 42.5% by high performance liquid chromatography (HPLC). The organoleptic evaluation results showed that the enzymatic modification improved the taste quality of stevia significantly. The sweetness became mild and soft, and a slight bitter taste still remains at high concentration, but disappears at low concentration. Desirable taste quality with significantly reduced production cost could be achieved by enzymatic modification of stevia.

29 Adsorption Characteristics of Alkali Fuchsia by Sweet Potato Dregs by Chemical Modification

CHEN Li , XIONG Xiao-ming , LI Xin

2019, 35(2):209-215. DOI: 10.13982/j.mfst.1673-9078.2019.2.029

[Abstract](493) [HTML](212) [PDF 57.58 M](747)

Abstract:
The modified sweet potato residue biosorbent was obtained by chemically modifying the waste sweet potato residue as raw material, and it was used for the adsorption of the basic fuchsin of the printed matter in the aqueous solution. Effects of modified sweet potato slag addition amount, particle size, initial concentration of basic fuchsin solution, solution pH, adsorption temperature and adsorption time on the adsorption rate were investigated. The initial concentration, addition amount and time showed significant effects. By using quadratic orthogonal rotating combination design, the optimum initial concentration, addition amount and time were determined as 200 mg/L, 0.8 g and 140 min, respectively. The measured adsorption rate was 97.38%, which is similar to the predicted maximum value of 97.66%. The adsorption equilibrium test showed that the adsorption of sweet potato residues on basic fuchsin was consistent with Langmuir and Frundlich model, and the maximum adsorption capacity was 37.17 mg/g. The adsorption kinetics can be described by quasi - second order kinetic equations. BET test and SEM observation showed that the modified sweet potato residue was optimized for porous surface and increased wrinkles, which was beneficial to the adsorption process. According to FTIR and EDS, hydroxyl and carboxyl groups play major roles in the adsorption process.

30 The Use of COI Sequence for Non-directional Screening to Detect Adulteration in Mutton

WANG Wei-ting , LIU Yao-bo , DU Peng-fei , HU Peng , RU Yi , CAO Hong-fang , WANG Shou-jing

2019, 35(2):216-222. DOI: 10.13982/j.mfst.1673-9078.2019.2.030

[Abstract](532) [HTML](236) [PDF 32.90 M](755)

Abstract:
This study investigated non-directional screening of other animal source materials incorporated in mutton by using COI sequence, while distinguishing goat meat and sheep meat. DNA barcoding technology was used to screen the mitochondrial genome cytochrome gene fragment of six sheep breeds (lines), and the selected primers were used to amplify the COI fragments of seven animal source samples to determine whether or not the primer can effectively distinguish the lamb from other animal source samples. Using LCOI490/HCO2198, F1-1/R1-1, and ITS3/ITS4 as primers, PCR amplification was performed on the genomic DNAs of 36 blood samples (3 goat species and 3 sheep species), with the PCR product obtained using F1-1/R1-1 as the primer being clear and reproducible. F1-1/R1-1 was used as the primer in the amplification of the COI fragment of chicken, pork, donkey meat, beef, Laiwu black goat meat, mutton sheep meat and duck meat samples, and then the amplified fragments of the seven kinds of meat samples were sequenced. The sequence homology between goat and sheep was only 36.62%, and the sequence difference among other breeds was also obvious The results showed that F1-1/R1-1 can be used as a special primer to distinguish effectively between mutton meat and meat from other animal sources, and also between goat meat and sheep meat samples.

31 Analysis of the Element Content Characteristic of Wild Boletaceae Mushrooms and Its Species Identification

SU Jiu-yan , ZHANG Ji , LI Jie-qing , DUAN Zhi-li , LI Tao , LIU Hong-gao , WANG Yuan-zhong

2019, 35(2):223-231. DOI: 10.13982/j.mfst.1673-9078.2019.2.031

[Abstract](545) [HTML](281) [PDF 36.18 M](811)

Abstract:
The nutritional value and exposure risk of wild Boletaceae are related to consumers’ health and safety, and influence market stability and trade exports seriously. In this paper, the contents of 12 kind of element contents in eight wild Boletaceae (429 samples in total) were determined and their corresponding infrared spectra data were collected by inductively coupled plasma atomic emission spectroscopy and Fourier transform infrared spectrometry. The content characteristics of elements and edible health risk were analyzed. Meanwhile, partial least squares discriminant analysis and support vector machine (SVM) discriminant models were established using element contents, infrared spectroscopy, low-level data fusion and mid-level data fusion. The classification results were compared. The results demonstrated that wild Boletaceae were rich in Ca, Mg, Na, Zn and other mineral elements, and moderate intake can supplement the nutritional needs of human body. Meanwhile, attention should also be paid to the risk of heavy metal exposure of some Boletaceae. The SVM discriminant model based on mid-level data fusion has the accuracy of training set and test set of 100%, which could be a promising technique to rapidly and accurately discriminate the species of Boletaceae. It can effectively avoid the occurrence of poisoning incidents caused by accidental ingestion. Analyzing the element contents, assessing the health risk and identifying the species of Boletaceae systematically, can provide a reference for the quality safety assessment and the development and utilization of resources.

32 Development of Droplet Digital PCR for Quantitative Detection of Porcine Circovirus Type 3

SHI Lei , LIU Yu-qi , LI Li-li

2019, 35(2):232-237. DOI: 10.13982/j.mfst.1673-9078.2019.2.032

[Abstract](625) [HTML](229) [PDF 443.27 K](790)

Abstract:
Porcine circovirus type 3 is a novel porcine circovirus that can cause diseases associated with porcine infection. In this experiment, primer probes were designed based on the OPF2 gene sequence of porcine circovirus type 3, and a droplet digital PCR (ddPCR) method for accurate and quantitative detection was established. After optimization of the primer probe concentration and annealing temperature for the ddPCR reaction system, the optimal primer probe concentration ratio was 800 nM: 800 nM: 400 nM; and the optimal annealing temperature was 60 ℃. The correlation coefficient R2 of the ddPCR standard curve was 0.999, showing a good linear relationship. The sensitivity was high with the limit of detection being 4.4 copies/μL and good specificity (no cross-reaction with the common pig pathogens ). The detection results of the clinical samples revealed that the ddPCR method established in this study was more sensitive than the real-time fluorescent PCR method by one order of magnitude, and could generate results consistent with those obtained by the fluorescent PCR and analyze quantitatively suspicious samples. The results showed that the newly established ddPCR method in this study had high sensitivity and specificity, thus could be used for quantitative detection of porcine circovirus type 3.

33 Rapid Detection for Sulfonamide Antibiotics Residues in Swine Urine Using TLC-SERS

ZHU Xiao-yu , SHANGGUAN Xin-chen , AI Shi-rong , PENG Xiong-xin , YANG Hong-fei , CHEN Tao , WU Rui-mei

2019, 35(2):238-246. DOI: 10.13982/j.mfst.1673-9078.2019.2.033

[Abstract](651) [HTML](202) [PDF 51.45 M](942)

Abstract:
A rapid detection method for sulfonamide antibiotics residues in swine urine was developed based on thin layer chromatography (TLC) and surface enhanced Raman spectroscopy (SERS) technology. Position samples were made by antibiotics being added to negative swine urine. Chloroform-ethanol-petroleum ether (1:1:2) was used as a mobile phase to separate antibiotics from swine urine. The excitation wavelength was 785 nm. Gold colloidal was used to enhance Raman signals. Coupled with Density functional theory, sulfadiazine characteristic peaks 877 cm-1 and 994 cm-1, sulfamethazine characteristic peak 661 cm-1, sulfathiazole characteristic peaks 862 cm-1 and 1127 cm-1 were found and used to qualitatively and quantitatively analyze antibiotics residues in swine urine. The minimum detection amounts of sulfadiazine, sulfamethazine and sulfathiazole in swine urine were 0.1, 0.1 and 0.2 mg/L, respectively. And TLC can achieve the separation of mixed antibiotics in swine urine. The characteristic peaks of each antibiotic are easily distinguished when the concentration of three mixed antibiotics in swine urine was 0.01 μg. TLC-SERS technology showed to be suitable for rapid detection of antibiotic residues in pig urine.

34 Development and Application of On-line System for Wheat Flour Quality Detection by Near Infrared Spectroscopy

ZHANG Bin , SHEN Fei , ZHANG Lei

2019, 35(2):247-252. DOI: 10.13982/j.mfst.1673-9078.2019.2.034

[Abstract](824) [HTML](287) [PDF 523.09 K](901)

Abstract:
In this work, an on-line detection system for flour quality testing was developed by near infrared spectroscopy. C++Builder 6.0 was applied for secondary development of NIR 1.7/S micro spectrometer based on hardware platform. A custom software with functions such as spectral acquisition, flour quality prediction, model update and data storage was also wrote. A total of 170 wheat flour samples collected from the market were subjected to NIR analysis and water content was chosen as the representative index for wheat flour quality. Different spectral pretreatment methods were tried and the spectra without any treatment combined with partial least square (PLS) regression obtained the best performance. The determination coefficient (R2) of calibration and prediction obtained were 0.947 and 0.841, respectively. The root mean square error (RMSE) of calibration and prediction as well as RPD value were 0.146%, 0.198% and 2.53, respectively. The established model was then imported into the software, and 30 samples were used for external validation. Results indicated that determination coefficient (R2) between the predicted value and the reference value was 0.883, and the RMSE was 0.206%. In conclusion, the prediction of the moisture of wheat flour by this on-line system is feasible, which can provide a technical reference for the application of on-line NIR spectroscopy technique.

35 Microbial Community Analysis of Mussel (Mytilus edulis) Based on High-throughput Sequencing

ZHAO Jin-li , WEI Wan-ying , SHEN Chun-lei , ZHANG Xiao-li , ZHANG Bin

2019, 35(2):253-258. DOI: 10.13982/j.mfst.1673-9078.2019.2.035

[Abstract](581) [HTML](207) [PDF 21.92 M](747)

Abstract:
To explore the composition of microbial flora attached to the surface of mussel (Mytilus edulis) under different conditions. The fresh mussel, the frozen mussel, the stored mussel, the homemade mussel, and the commercial mussel were used as objects by microbial extraction and high-throughput sequencing analysis of the surface of mussel (Mytilus edulis). The composition and changes of microorganism in different samples of mussel were obtained. The experimental results showed that the effective sequence range of each sample was from 30066 to 40563, and the operational taxonomic unit (OTU) range was from 28 to 128. The OTU number of commercially available mussels was the lowest, while the OTU number of frozen purple mussels was relatively higher compared with the other samples. Based on the analysis of microorganisms, it was found that the Pseudomonas and Acinetobacter were mainly found in fresh mussels and homemade mussels, and the Psychrobacter was detected in frozen mussels as the dominant microorganisms. In addition, the Pseudomonas and Acinetobacter were confirmed as the major microorganisms in the stored mussels, while the dominant flora in the commercial mussels were found as Staphylococcus and Enterococcu, respectively. The results indicated that there were significant differences in the microbes, microbial structure, abundance and mutual proportion of the mussel samples when they were under different states. It is necessary to design different controlling techniques for different types of mussel products. The composition of the mussels under different conditions had remarkable difference, which indicated that the state of the mussels, the processing process and the storage and sales environment all had a great influence on the composition of the mussels. The results of the study can provide a reference for ensuring the quality and safety of mussel products.

36 The Leaching Rules and Rapid Measurement of Cadmium, Lead and Arsenic in Tea

TAO Ze-hong , ZHANG Ming-zhou , HAO Pei-ying

2019, 35(2):259-263. DOI: 10.13982/j.mfst.1673-9078.2019.2.036

[Abstract](619) [HTML](286) [PDF 15.25 M](860)

Abstract:
In order to clarify the leaching regularity of cadmium (Cd), lead (Pb) and arsenic (As) in tea, and to explore a fast method for measuring these heavy metals, microwave digestion and boiling water leaching was used for pre-treatment. Then the content of Cd, Pb and As in tea water, tea residue and tea was determined by inductively coupled plasma mass spectrometer (ICP-MS), respectively, to explore the leaching rules of these three elements and develop a rapid determination method. The results showed that the content of Cd, Pb and As in tea did not exceed the corresponding national standard of China. Under the extraction conditions in this study, the contents of Cd, Pb and As in tea water soaked 20 minutes all have a linear relationship with those in tea, and the linear equation of Cd, Pb and As is, Y=7.40623X+0.0235 (r=0.9999), Y=5.44998X+0.03008 (r=0.9935), and Y=2.25405X+0.01115 (r=0.9822), respectively. Therefore, the total amount of Cd, Pb and As in tea can be assessed by measuring the content in tea water, fulfilling the rapid measurement of Cd, Pb and As in tea. This study clarified the leaching rules of Cd, Pb and As in tea, and provided a method for rapid pre-treatment and determination of Cd, Pb and As in tea.

37 Study on the Identification of Pork Fraction Proportion in Mixed Meats with Dual Real-time PCR Based on Homo-tag Assisted Non-dimer System

SHAO Jian-hong , LIAO Xiu-yun , LUO Bao-zheng , ZHAO Fu-zhen , SHA Cai-hua , CHEN Xuan , BO Qing-ru

2019, 35(2):264-269. DOI: 10.13982/j.mfst.1673-9078.2019.2.037

[Abstract](705) [HTML](191) [PDF 13.18 M](704)

Abstract:
The beef & mutton and their products in the market always mixed with pork, which is relatively cheaper. In order to identify the proportion of pork, a dual real-time PCR assay was established on the basis of Homo-tag Assisted Non-dimer system (HANDS). The assay applied a simple mathematical maodel to calculate the percentage of pork fraction according to the Ct (cycle thresholds) values shown on the real-time PCR assay. Universal primers and probe sequences were designed according to the House-keeping gene that consist in all livestock-poultry chromosome named Myostatin, while specific primers and probe sequences were designed according to the beta actin gene sequences in swine chromosome. The homologous tag primer sequences were added to the 5’-end of all primer sequences. To establish the real-time PCR assay, the universality and specificity of the primers & probes were assessed, and the concentration of primers & probe and annealing temperature of reaction were optimized. After testing of 5 mixed meats which were prepared in advance, the calculation of pork proportion was based on the Ct values which were obtained from the assay. Comparing the proportion differences between the calculation and actual preparation, the feasibility of identification pork proportion in mixed meats was evaluated. The efficiency of amplification of two reactions in dual Real-Time PCR detection is approximate. The calculation results are in agreement with the actual proportion according to the detection results of the mixed meats which have been prepared in advance. The newly established assay is stable, sensitive and accurate, so it is suitable for the supervision of food in market.

38 Traceability of Five Steroid Hormones in Butter Investigated by Gas Chromatography-combustion-isotope Ratio Mass Spectrometry

ZHAO Chao-min , GU Shu-qing , QU Li , HAN Li , XIAO Chen-gui , DENG Xiao-jun , YUE Zhen-feng , WANG Chuan-xian , FANG Ke-yan

2019, 35(2):270-278. DOI: 10.13982/j.mfst.1673-9078.2019.2.038

[Abstract](568) [HTML](169) [PDF 695.62 K](597)

Abstract:
A gas chromatography-combustion-isotope ratio mass spectrometry method was developed for investigating the traceability of five steroid hormones (estrone, α/β-estradiol, estriol and progesterone) in butter. The samples were first extracted by ethylacetate/cyclohexane (1:1, V/V). The sample was extracted with ethyl acetate-cyclohexane (1:1, V/V), purified by gel permeation chromatography (GPC) and semi-preparative liquid chromatography (Pre-HPLC), separated through a HP-5MS column (30 m × 0.25 mm, 0.25 μm), before traceability analysis by gas chromatography-combustion-isotope ratio mass spectrometry (GC/C/IRMS) and qualitative and quantitative analyses by GC/MS. The δ13C values of the exogenous hormones in butter were <-30‰ while the δ13C values of endogenous hormones were >-27‰, among which the δ13C value of exogenous progesterone in butter was -30.59‰±0.12‰ and the δ13C value of endogenous progesterone ranged from -26.83‰±0.25‰ to -23.80‰±0.33‰. One-way analysis of variance (p-value=0.009<0.05) indicated a significant difference in the δ13C values between the endogenous and exogenous progesterone. The simulation experiments showed that the δ13C value of the sample spiked with an exogenous hormone was homologous with the δ13C value of the exogenous hormone. The sensitivity of the method for the five hormones was in the range of 15~100 ng. The within-batch precision of the method ranged from 0.11‰ to 0.17‰ and the between-batch precision was 0.16‰. The step of Pre-HPLC fraction collection was critical for isotopic fractionation and analysis accuracy. The obtained results showed that the established method is accurate and specific, and GC/C/IRMS is an effective tool for investigating the origin of steroid hormones.

39 Determination of 10 Kinds of Synthetic Colorants in Variety of Food Substrates by SPE-HPLC

LI Tong-hui , SHANG Wei , ZHOU Nan , WANG Mei , YUAN Li-jie

2019, 35(2):279-284. DOI: 10.13982/j.mfst.1673-9078.2019.2.039

[Abstract](624) [HTML](219) [PDF 6.99 M](865)

Abstract:
To establish a separation and analysis method for the simultaneous determination of 10 kinds of synthetic colorants, such as lemon yellow, sunset yellow, new red, amaranth, indigo, carmine, tempting red, bright blue, red peony and acid red. Comparing the separation of 10 colorants with Eclipse XDB-C18, Venusil XBP C18 and Symmetry C18 columns, the recovery rates of three solid phase extraction cartridges on Sep-Pak Plus QMA, ProElut PWA-2 and Cleanert PWAX-SPE for ten kinds of Synthetic colorants were characterized for qualitative and quantitative purposes. This method could realize the separation and analysis of ten synthetic colorants in 27 min. It has a good linear relationship in the range of 0.20~50.00 μg/mL (R2>0.999). The recovery ratio of the standard mixture was 69.71%~103.80% (n=6) in the samples, relative standard deviation range was 0.72%~9.41% (n=6). The pretreatment of this method was simple and efficient, with high accuracy and good reproducibility. The recovery rate, detection limit and precision could meet the requirements of national standards. The false negative rate was suitable for large-scale matrix foods in grassroots laboratories.

40 Study on 18 Heavy Metal Elements in Oral Liquid Health Foods

CHENG Min , ZHAN Min , TAN Li-rong , YAN Shi-kai , LI Sha-sha , XIAO Xue

2019, 35(2):285-290. DOI: 10.13982/j.mfst.1673-9078.2019.2.040

[Abstract](682) [HTML](165) [PDF 909.99 K](679)

Abstract:
A kind of heavy metal elements (Pb, Cd, As, Hg, Cu, Pt, Pd, Ir, Rh, Ru, Os, Mo, Ni, Cr, V, Mn, Fe, Zn) in oral liquid health foods derived from Chinese herbal medicine based on inductively coupled plasma mass spectrometry (ICP-MS) was established in this work. The oral liquid samples were pre-treated by microwave digestion. The Ge, In and Bi elements were used as the internal standard elements for correcting the matrix effect and signal drift. The contents of 18 heavy metals in ten batches of samples were determined by ICP-MS. Results showed that good linear relations of 18 heavy metal standard curves were found, R2≥0.999, the detection limit of each element was between 0.0001~2.743 ng/mL, the precision RSD was between 0.49%~4.29%, and the repetitive RSD value was between 1.2% and 15%, the recovery rate of the sample was between 82.74% and 122.7%. The 18 heavy metal elements in the two oral liquids were not exceeded. Results showed that this method is easy to operate, fast in analysis, high in sensitivity and good in accuracy. It is suitable for the detection of heavy metals in oral liquid health foods, and can provide a basis for health food safety evaluation.

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Volume 35,Issue 2,2019 Table of Contents