• Volume 37,Issue 1,2019 Table of Contents
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    • >Special Edition
    • Contribution of Starch Components to Flavor Formation in Instant Rice Products

      2019, 37(1):1-9. DOI: 10.3969/j.issn.2095-6002.2019.01.001

      Abstract (1334) HTML (1111) PDF 4.36 M (1350) Comment (0) Favorites

      Abstract:Instant rice products are a large group of convenient products and the flavor of these products is the important indicator for the evaluation. Starch, as one of the main components of rice products, is involved in their flavor formation and release. The common mechanism of the contribution of starch com-ponents to flavor was summarized. The role of starch components in the flavor formation and release for six main categories of instant rice products were exampled. These instant rice products included instant rice at room temperature, instant rice by extrusion, fermented rice cake, extruded rice noodles, and rice dump-ling. The trend in research and development of the contribution of starch to flavor is put forward in order to provide important scientific basis for the development of instant rice products with high quality.

    • >Expert Forum
    • Variation Analysis of Cereals Mycotoxin Limit Standards of CAC,EU,USA, and China

      2019, 37(1):10-15. DOI: 10.3969/j.issn.2095-6002.2019.01.002

      Abstract (1155) HTML (687) PDF 967.62 K (1336) Comment (0) Favorites

      Abstract:Mycotoxins are toxic secondary metabolites produced by fungi, and among the most harmful are aflatoxin, ochratoxin A, trichothecenes, zearalenone, fumonision, ergot alkaloid and so on. The establishment of the limit standard for mycotoxins is the main measure for the primary prevention of mycotoxins. Through the comparison and analysis of CAC,European Union, the United States and China's grain mycotoxins limit standards, this study has found out the existing gaps in China's current national food safety standards concerning the mycotoxins pollution index of grains, and provided references for the revision of China's grain mycotoxins limit standards.

    • Variation Analysis of Cereals Heavy Metals Limit Standards of CAC, EU, USA, and China

      2019, 37(1):16-19. DOI: 10.3969/j.issn.2095-6002.2019.01.003

      Abstract (1410) HTML (962) PDF 919.68 K (1112) Comment (0) Favorites

      Abstract:Heavy metal pollution is an important aspect of cereal quality and safety. Countries and organizations all over the world attach great importance to the control of heavy metals in cereals.Through the comparison and analysis of cereal heavy metals limit standards of CAC,European Union, the United States and China, this study has found out the existing gaps in China's current national food safety standards concerning the heavy metals pollution index of cereals, which could provide references for the revision of China's heavy metal limit standards of cereals.

    • >Special Studies
    • Expression, Biochemical Characterization and Structure Resolution of β-Glucosidase from Paenibacillus barengoltzii

      2019, 37(1):20-27. DOI: 10.3969/j.issn.2095-6002.2019.01.004

      Abstract (983) HTML (518) PDF 6.81 M (1022) Comment (0) Favorites

      Abstract:A β-glucosidase gene from Paenibacillus barengoltzii CAU904 was cloned and heterologously expressed in E. coli. The recombinant enzyme was purified and biochemically characterized, and its crystal structure was further resolved. The enzyme had the highest activity at 50℃ and pH 7.5. It exhibited broad substrate specificity on various substrates, including laminarin, barley β-glucan, lichenan, et al. (containing β-1,2,β-1,3,β-1,4 and β-1,6 linkages). Crystal structure analysis revealed that the enzyme exhibited typical glycoside hydrolyase family 3 enzymes, having multiple domain structures. The catalytic packet of the enzyme was composed by a (α/β)5 sandwich domain and a (β/α)8 folding barrel domain linked by a loop region. The side chain aromatic amino acids Trp748 and Trp749 were functioned as -1 and +1 binding site, respectively, while Trp131 was functioned as +2 site. These aromatic amino acids formed a narrow pocked and a hydrophobic environment, which could diminish its transglycosylation activity.

    • Optimization of Fermentation Conditions for β-1,3-1,4-Glucanase Production by Aspergillus flavus

      2019, 37(1):28-35. DOI: 10.3969/j.issn.2095-6002.2019.01.005

      Abstract (906) HTML (532) PDF 2.78 M (938) Comment (0) Favorites

      Abstract:An Aspergillus flavus with the ability to yield high production of β-1,3-1,4-glucanase was found. The fermentation conditions for this enzyme in the shake flask were optimized using a combination of one-single-factor method and response surface methodology. The results indicated that the optimal culture medium components for β-1,3-1,4-glucanase production were 19g/L wheat bran, 30g/L (NH4)2HPO4, 21g/L Tween-60,5g/L NaCl, 0.5g/L MgSO4·7H2O and 0.75g/L KH2PO4 at an initial pH of 8.0. The highest enzyme activity of 155.9U/mL was obtained when the strain was cultured at 38℃ for 6d in the optimized culture medium. The crude β-1,3-1,4-glucanase from Aspergillus flavus could hydrolyze oat and barley powder to mainly yield glucose. These results indicated that the extracellular β-1,3-1,4-glucanase produced by Aspergillus flavus possess great potential for its industrial applications.

    • Comparison of Immobilization Methods of Sucrose Isomerase PalI with Embedding and Crosslinking

      2019, 37(1):36-40. DOI: 10.3969/j.issn.2095-6002.2019.01.006

      Abstract (1000) HTML (562) PDF 1.37 M (854) Comment (0) Favorites

      Abstract:The immobilization methods using sodium alginate as the embedding medium and flutaraldehyde as the crosslinker was used to improve the cyclic utilization and stability of immobilized sucrose isomerase PalI from Klebsiella sp. LX3.The results showed that the highest enzyme activity was obatained when the concentrations of sodium alginate and CaCl2 were 1.5% and 2%. Meanwhile, the optimum temperature and pH value of embedding enzyme were 40℃ and 6.0. The optimum condition of the crosslinking method was the concentrations of ammonium sulfate and flutaraldehyde were 90% and 2.5%. Meanwhile, the optimum temperature and pH value of crosslinking enzyme were 50℃ and 5.0. Through the comparison of stability, the conclusion was that the enzyme activity of both methods was better than that of free enzyme. The residual enzyme activity of immobilized enzyme with flutaraldehyde and sodium alginate kept in 95% and 60%, while that of the free enzyme was only 30% when enzymes were stored at 4℃ for 20 days. The crosslinking immobilization enzyme was superior to the sodium alginate immobilized enzyme, and its residual enzyme activity was still 80% after repeated use for 12 times.

    • >Foundational Research
    • Study on Relativity of Polypeptides Sequence and Emulsifying Properties in White Chicken Broth

      2019, 37(1):41-46. DOI: 10.3969/j.issn.2095-6002.2019.01.007

      Abstract (647) HTML (576) PDF 1.00 M (824) Comment (0) Favorites

      Abstract:The sequence relativity and emulsifying properties of the polypeptides in traditional Chinese white chicken broth were studied. The white chicken broth stewed for 3 hours was centrifuged and the stable emulsified layer was obtained. The emulsifying polypeptide solution was acquired by defatting and microfiltration of the emulsified layer. The average length of polypeptide was 13 amino acid residues and its critical micelle concentration was 4 mg/mL. The emulsifying polypeptide solution was then treated by 3 kDa ultrafiltration, and 1646 polypeptides were sequenced by HPLC-MS. The average hydrophobility degree of these polypeptides was 4791.70kJ/mol. Most polypeptides consisted of a similar ratio of hydrophilic and hydrophobic amino acids, while they contained a low ratio of strong hydrophilic and hydrophobic amino acids. The either end of these emulsifying peptides were mainly hydrophilic amino acids. This study may be helpful to develop novel natural polypeptide surfactants.

    • Effects of Rhizoma gastrodiae Ethanol Extracts on Mycelia Polysaccharides and β-Glucan Biosynthesis Quantity of Grifola frondosa

      2019, 37(1):47-53, 61. DOI: 10.3969/j.issn.2095-6002.2019.01.008

      Abstract (589) HTML (614) PDF 1.21 M (913) Comment (0) Favorites

      Abstract:Rhizoma gastrodiae ethanol extracts were supplemented into the fermentation system of Grifola frondosa to study effects of R.gastrodiae ethanol extract on mycelia biomass, mycelia polysaccharides and β-glucan yield of Grifola frondosa by submerged fermentation. In addition, the key ingredients in Rhizoma gastrodiae ethanol extracts were identified. Meanwhile, the appropriate concentration of characteristic constituents of R.gastrodiae ethanol extracts were determined by high performance liquid chromatography. The results showed that R.gastrodiae ethanol extracts with the concentration of 7g/L could significantly promote cell growth, mycelia polysaccharides, and β-glucan yield. Under this concentration, the biomass, mycelia polysaccharides and β-glucan yield reached 1.708g/L, 5.974% and 2.055mg/g, and significantly (P<0.05) increased by 0.36,1.29, and 1.44 times, respectively, compared with the control (without additives). The characteristic ingredients of R.gastrodiae ethanol extracts were gastrodin (GA), p-hydroxybenzyl alcohol (HA), and p-hydroxylbenzaldehyde (HBA), and the contents were 5.8375,1.1072, and 0.6601mg/g, respectively. Meanwhile, HBA was the most responsible ingredients to promote the biomass, mycelia polysaccharides and β-glucan yield in submerged culture of Grifola frondosa and the optimum supplemental levels were 100,0, and 150mg/L, respectively.

    • Surface Properties of Pediococcus pentosaceus and Antibacterial Effect

      2019, 37(1):54-61. DOI: 10.3969/j.issn.2095-6002.2019.01.009

      Abstract (819) HTML (756) PDF 1.96 M (868) Comment (0) Favorites

      Abstract:The growth condition and analysis of acid production capacity showed that Pediococcus pentosaceus F28-8 had a good acid adaptability, and the surface structure was observed with transmission electron microscopy. The S-layer was extracted with 5mol/L LiCl and analysed by SDS-PAGE and MALDI-TOF-MS. It was found that the S-layer of F28-8 contained a kind of surface protein with molecular weight of 83.5kDa and 51.1kDa. The further surface property test, collagen adhesion test and antibacterial experiment showed that the stripping of surface protein significantly reduced the surface properties (automatic aggregation ability, surface hydrophobicity and surface charge), with a decrease of 19.0%-56.1%. The surface protein of F28-8 extracted by LiCl significantly reduced the adhesion of Salmonella and Staphylococcus aureus to collagen, with a decrease of 74.59% and 81.16%. The inhibitory rate of surface protein of F28-8 extracted by LiCl against Salmonella and Staphylococcus aureus reached 31.5% and 15.6%, respectively. The results indicate that surface protein of P. pentosaceus F28-8 can change the surface properties of cells, enhance their ability to inhibit the adhesion of pathogenic bacteria and exhibit certain antibacterial ability, and has certain application potential in the field of antibacterial agents.

    • Research Progress in Flavor Chemistry of Famous Green Teas

      2019, 37(1):62-71. DOI: 10.3969/j.issn.2095-6002.2019.01.010

      Abstract (879) HTML (541) PDF 1.08 M (1046) Comment (0) Favorites

      Abstract:The premium green teas are normally characterized by their superior quality and desirable aromas, of which their chemical profiles are similar but also distinctive. Four kinds of famous green teas, including Dongting Biluochun Tea, Xihu Longjing Tea, Xinyang Maojian Tea, and Huangshan Maofeng Tea, were studied in terms of the formation mechanisms of their aromas, their physical and chemical properties, as well as their sensory properties. Some factors, including the tea varieties, growth environment, processing technology and storage conditions, have been found to have significant impact on the tea quality, which will be the research focus of the flavor chemistry of green teas in the future.

    • >Applied Technology
    • Effect of Storage Time on Qualities of High Pressure Treated Fresh Tomato Juice

      2019, 37(1):72-77. DOI: 10.3969/j.issn.2095-6002.2019.01.011

      Abstract (857) HTML (638) PDF 1.51 M (882) Comment (0) Favorites

      Abstract:The qualities and aroma of fresh tomato juice treated by a high pressure treatment (25℃ and 400MPa for 30min) and a thermal treatment (100℃ for 5min) were compared after 3 months storage. The total number of colonies, mold and yeast of fresh tomato juice treated with the high pressure treatment met the National Food Safety Criteria after two month storage. During the two months storage, the pH value, PPO activity, and POD activity of high pressure treated fresh tomato juice decreased while the vitamin C content decreased by about 24%. However, the vitamin C content of fresh tomato juice treated by the thermal treatment was reduced by about 96%. After the high pressure treatment, the aroma of the fresh tomato juice was similar to that of the original tomato aroma, while that was deteriorated after the thermal treatment. Therefore, the high pressure treatment maintained the qualities and aroma of the fresh tomato juice after 2 months storage.

    • Study on Bread-Baking Technology of Super Gluten Wheat Flour

      2019, 37(1):78-83. DOI: 10.3969/j.issn.2095-6002.2019.01.012

      Abstract (565) HTML (506) PDF 949.55 K (801) Comment (0) Favorites

      Abstract:In order to bake out fine bread which can fully express the quality characteristics of super gluten wheat Jimai 229, there are several techniques and methods were used including four time treatments of fermentation, five dosage treatments of yeast and sugar, four flour blending treatments. The results are as followings. Within the four treatments of fermentation time, the bread showed excellent quality when the fermentation time of dough and bread dough were 30min and 50min, respectively.And for the five dosage treatments of yeast and sugar, the bread has the best quality baked by toast procedure with amount of dry yeast and sugar was 6g and 24g, respectively, and the bread showed excellent quality baked by French bread procedure with amount of dry yeast and sugar was 3g and 18g, respectively. For the flour blending treatments between Jimai 229 and Jimai 22, the bread quality was changed markedly, and the bread showed the best quality when 100g Jimai 22 flour was blended to 200g Jimai 229 flour. Therefore, for super gluten wheat proper adjustment dough and bread embryo wake up time, to adjust the material to bake out of good quality bread.

    • Extraction and Antioxidant Activities of Polyphenols in Black Jerusalem Artichoke

      2019, 37(1):84-89. DOI: 10.3969/j.issn.2095-6002.2019.01.013

      Abstract (810) HTML (566) PDF 1.03 M (872) Comment (0) Favorites

      Abstract:The orthogonal experiment was used to determine the optimization extraction condition of polyphenols from black and fresh Jerusalem artichoke. The optimal conditions were ethanol concentration 55%, the material solvent ratio 1∶ 35g/mL, temperature 85℃, and time 45min. Under this condition, the polyphenols extraction yield of black Jerusalem artichoke was 6.41mg/g while the extraction yield of fresh Jerusalem artichoke was 1.13mg/g. The results also showed that the antioxidant activities had relevance with polyphenols contents and a positive correlation between polyphenols contents and ferric reducing antioxidant power was obtained (R=0.9946). Polyphenols from black Jerusalem artichoke had higher DPPH scavenging ability, hydroxyl radical scavenging ability, and ferric reducing antioxidant power, which were 1.08~1.54 times, 1.02~1.28 times, and 2.56~3.98 times higher than fresh Jerusalem artichoke.

    • Preparation of Quality Control Sample for Poppy Shell in Solid Compound Spice

      2019, 37(1):90-97, 110. DOI: 10.3969/j.issn.2095-6002.2019.01.014

      Abstract (517) HTML (639) PDF 1.08 M (682) Comment (0) Favorites

      Abstract:To establish a method for quality control samples for the poppy shell in solid compound spices. The spice matrix materials and the poppy shell were dried by microwave, mixed, pulverized,sieved, and then mixed again. After added with antagonist, the samples were dried, sieved, and mixed again.The homogeneity and stability of the samples were strictly examined.The concentrations of each chemical constituent in the samples were collaboratively analyzed using liquid chromatography-tandem mass spectrometry in 10 laboratories and then the uncertainty was assessed.The results showed that the characteristic values of the codeine, thebaine,morphine,papaverine,noscapine in these samples were (907±20.9), (918±18.4), (315±16.5), (171±12.6), (139±15.8)μg/kg respectively. The uniformity and stability was good. The methodology is suitable for verifying alkaloids in solid compound spices to control the quality.

    • Effect of Process on Lipid Oxidation of Chicken Crisp Floss

      2019, 37(1):98-103. DOI: 10.3969/j.issn.2095-6002.2019.01.015

      Abstract (519) HTML (456) PDF 995.88 K (755) Comment (0) Favorites

      Abstract:To study the effect of processing technologies on lipid oxidation of chicken crisp floss, effects of cooking time, cooking temperature, and frying time on 2-thiobarbituric acid reactive substrates were investigated, and effects of frying technologies on comprehensive scores and lipid oxidation of chicken crisp floss were also analyzed. The results showed frying time significantly affected lipid oxidation, while the initial cooking time did not have significant impact on lipid oxidation. In addition, the sequences of factors influencing the comprehensive evaluation score were frying time, initial cooking time, and cooking temperature. The optimal conditions were initial cooking time 50min, recooking time 10min, cooking temperature 90℃, and frying time 20min, and the finial content of 2-thiobarbituric acid reactive substrates was 2.26mg/kg. Furthermore, the trend of the comprehensive score was not entirely consistent to the 2-thiobarbituric acid reactive substrates value. The technologies during the processing of chicken crisp floss affected the fat oxidation and product quality.

    • >Safety Supervision
    • Salting-Out Assisted Liquid-Liquid Extraction Coupled to UPLC-MS/MS for Determination of Tetracyclines in Milk Powder

      2019, 37(1):104-110. DOI: 10.3969/j.issn.2095-6002.2019.01.016

      Abstract (806) HTML (791) PDF 1.10 M (838) Comment (0) Favorites

      Abstract:The use of salting-out assisted liquid-liquid extraction (SALLE) combined with UPLC-MS/MS has been evaluated for the determination of tetracyclines in milk powder. The samples were extracted with Na2EDTA-Mcllvaine buffer, and then the target analytes were extracted with acetonitrile assisted with (NH4)2SO4. After concentrated, the target analytes were separated on a BEH C18 column with gradient elution using acetonitrile and water containing volume fraction 0.1% formic acid as mobile phase. MS detection was performed with the positive ion mode in multi-reaction monitoring. The samples were quantified with external standard method. The result showed that, under the assisted with (NH4)2SO4, the extraction and purification effect of acetonitrile was improved. The limit of detection was 0.36μg/kg, which was much lower than 50μg/kg for the solid-phase extraction method. The linear range was from 1 to 100μg /kg with the correlation coefficient R>0.999. The recoveries of the method were ranged from 71.88% to 107.13% at the spiked levels of 1,5, 50μg/kg and the relative standard deviation was less than 8%. This method was simple, sensitive, economical, reliable and environmentally friendly. The method was suitable for the qualitative and quantitative of tetracyclines in milk powder.

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