15 July 2020, Volume 46 Issue 13

    

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  Semi-rational design of sucrose phosphorylase and optimization of conditionsfor α-arbutin production

  SHEN Yang, LYU Xueqin, LIN Lu, LI Jianghua, DU Guocheng, LIU Long

  Food and Fermentation Industries. 2020, 46(13): 1-9. https://doi.org/10.13995/j.cnki.11-1802/ts.023866

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  α-arbutin is a high-value glycoside and has a wide range of applications in the cosmetics and pharmaceutical industries. The enzymatic method is the main way for the production of α-arbutin, but the production of α-arbutin is limited due to the lack of enzymes with high catalytic efficiency. In order to improve the biotransformation efficiency of sucrose phosphorylase (SmSP) from Streptococcus mutans UA159 and further improve the production of α-arbutin, four vectors expressing SmSP in Bacillus subtilis WB600 were screened, among which the recombinant plasmid pP43NMK-P₄₃-gtfA achieved the highest α-arbutin yield (40.2 g/L) after 20 h of whole cell transformation. Secondly, site-directed saturation mutagenesis was performed on the loop A around the catalytic active center of SmSP to improve the affinity between the enzyme and the receptor, and a mutant SmSP^I336L was obtained. Its α-arbutin production and the molar conversion of substrate hydroquinone (hydroquinone,HQ) were 71.7 g/L and 72.4%, respectively. The production increased by 78.4% compared to the control. Finally, the reaction conditions for α-arbutin synthesis were optimized by the recombinant strain B. subtilis WB600/pP43NMK-P₄₃-SmSP^I336L.The final α-arbutin productionreached110.3 g/L,and the molar conversion rate of HQ was 88.7%. The production was increased by 2.74 times compared to the control. The obtained high-catalytic efficiency recombinant strains and the analysis of mutant kinetics were of important research significance and application value for the biotransformation of α-arbutin.
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  Heterologous expression and enzymatic properties of laccase isozymes ofPleurotus eryngii var. ferulae

  YUAN Chang, ZHAO Liting, GU Zhenghua, LI Youran, SHI Guiyang, DING Zhongyang

  Food and Fermentation Industries. 2020, 46(13): 10-17. https://doi.org/10.13995/j.cnki.11-1802/ts.023642

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  Co-culture is an effective way to improve laccases fermentation level. The previous study showed that the transcription levels of lacc2 and lacc6 changed significantly during co-culture. In this study, lacc2 and lacc6 were successfully cloned and expressed in Pichia pastoris GS115. The crude enzyme solution of LACC2 and LACC6 were purified to investigate the enzymatic properties. When ABTS was used as the substrate, the optimal temperatures and pH of LACC2 and LACC6 were 50°C and 3.0, respectively. Moreover, low concentrations of K⁺, Cu²⁺, Co²⁺ and Mn²⁺ enhanced the activities of LACC2 more than LACC6. In addition, LACC2 showed better tolerance to organic reagents and surfactants than LACC6, while LACC2 was more vulnerable to the inhibitors than LACC6. The enzyme kinetics results showed that ABTS was the optimal substrate of LACC2 and LACC6, and the K_m of LACC2 and LACC6 were 0.13 mmol/L and 0.24 mmol/L, respectively. This study provided important basic data on the properties of isoenzymes for the mechanism analysis of R. mucilaginosa enhanced P. eryngii var. ferulae laccases production during co-culture, which was beneficial to the comprehensive analysis of the promotion mechanism.
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  Three enzyme coupling to synthesize α-ketoisovalerate in E. coli

  LI Yating, ZHOU Li, ZHOU Zhemin

  Food and Fermentation Industries. 2020, 46(13): 18-23. https://doi.org/10.13995/j.cnki.11-1802/ts.022717

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  As an important intermediate product in the fields of biosynthesis and chemical synthesis, α-ketoisovalerate has been widely studied and applied in pharmaceutical and chemical synthesis field. Three key genes, BsalsS, EcilvC and EcilvD (encoding acetolactate synthase, acetolactate isomerase and dihydroxy acid dehydratase respectively), were cloned in this study into plasmid pETDuet-1 in order to enhance the synthesis of α-ketoisovalerate in E. coli BL21(DE3). And the original strain SDC were obtained. Furthermore, the orders of the three genes in plasmid were optimized to balance their expression. After comparing the co-expression result and the ability to catalyze the substrate sodium pyruvate to α-ketoisovalerate using the crude enzyme solution, the optimal strain CSD was obtained. Moreover, terminators of each gene in strain CSD to fine-tuning gene expression were added so as to get the final strain C_TSD_T. The α-ketoisovalerate conversion level of strain C_TSD_T was 2.28-fold high than that of strain SDC. Using glucose as the carbon source, strain C_TSD_T yielded α-ketoisovalerate of 1.70 g/L after 16 h cultivation, which was 3.36-fold higher than the original strain SDC. These results established foundation for efficient production of α-ketoisovalerate in E. coli BL21(DE3).
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  Effect of ammonia nitrogen on the production of ε-poly-L-lysinein Streptomyces diastatochromogenes

  WEI Xiqing, GUO Fengzhu, HU Chunlei, SONG Fu, ZHAO Zhuo, TAN Zhilei, JIA Shiru

  Food and Fermentation Industries. 2020, 46(13): 24-29. https://doi.org/10.13995/j.cnki.11-1802/ts.023292

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  ε-poly-L-lysine(ε-PL) is a new type of broad-spectrum natural food preservative. Because of its high cost and high price, its application in food industry is limited. In order to reduce the production cost, the effect of ammonia nitrogen (NH⁺₄-N) concentration on the production of ε-PL by Streptomyces diastatochromogenes was studied. Results indicated that the yield of ε-PL was 0.95 g/L,improved by 15.13% compared with the control group and the activities of Ask and Pls were improved when the initial concentration of NH⁺₄-N was 0.5 g/L fermented in shaking flasks for 96 h. An effective increasing ε-PL production method was verified by the batch and fed-batch fermentations: The initial concentration of NH⁺₄-N was 2.5 g/L, ammonium sulfate maintains the concentration of 0.5 g/L in 5 L the fermenter by fed-batch. In this method, the final yield of ε-PL was 27.67 g/L, which was improved by 17.72% contrasting to the control group.
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  High-cell-density cultivation of the recombinant E. coli and itsapplication in the production of Ala-Gln

  PEI Xuze, LI Yimin, DU Cong, YUAN Wenjie

  Food and Fermentation Industries. 2020, 46(13): 30-35. https://doi.org/10.13995/j.cnki.11-1802/ts.023810

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  L-alanyl-L-glutamine (Ala-Gln) is an important functional dipeptide, which has important value in food, medicine and health care products. Using recombinant Escherichia coli to express α-amino acid ester acyltransferase as whole-cell catalyst, which linked alanine methyl ester hydrochloride with glutamine to synthesize Ala-Gln, was an ideal method for the production of Ala-Gln. The high-cell-density cultivation could increase the proliferation concentration of microorganisms and reduce the cost. Firstly, the medium of E. coli BL21-pet29a-SsAET strain which expressing α-amino acid ester acyltransferase was optimized using response surface methodology based on the basic culture medium composition, such as carbon source, nitrogen source, and inorganic salt in flask-shaking experiment. Then, the important factors for fed-batch cultivation, such as pH, feeding medium and feeding mode, were investigated in fermenter. Finally, the recombinant E. coli by the high-density cultivation as whole-cell catalyst were used for the synthesis of dipeptide. The results showed that the optimum concentration of the semi-synthetic medium was: glucose 10 g/L, mixed nitrogen source 24 g/L, KH₂PO₄ 4.62 g/L and K₂HPO₄ 25.08 g/L. And the optimum feeding method was controlled using the automatic feedback by dissolved oxygen against pH-controlled. When the semi-synthetic medium was used with automatic feedback by dissolved oxygen, the OD₆₂₀ value of the bacteria reached up to 67 at 30 h, which was 14 times better than that of flask culture. When the high density-culture of recombinant E.coli was used to synthesize dipeptide, the concentration of Ala-Gln reached 34.56g /L and the production efficiency was 7 g/(L·min), which could further enhance its potential for industrial applications.
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  Analysis of antioxidant activity of ten kinds of Douchi and theirinfluencing factors

  CHEN Yi, LU Minjie, LIU Yang, JIANG Liwen, LI Pao, LIAO Luyan

  Food and Fermentation Industries. 2020, 46(13): 36-41. https://doi.org/10.13995/j.cnki.11-1802/ts.023833

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  The antioxidant activity of Douchi, a traditional fermented soybean, was evaluated by measuring the hydroxide free radical-scavenging rate(·OH)and total antioxidant capacity. And the differences in antioxidant activity were investigated by analyzing the pH, degree of hydrolysis, content of polyphenol, protein and soybean isoflavone. Results showed that significant differences in antioxidant activity of different commercial Douchi was observed. Mucor-type Huangyao Douchi exhibited the strongest total antioxidant capacity of (0.6±0.01) mmol/L while the bacterial-type Binli natto showed the weakest. Mucor-type Daoxiangyuan Douchi exhibited the highest ·OH scavenging activity (65.3±0.62) %. Similarly, the contents of total polyphenols and aglycogenic isoflavones in Aspergillus-type and Mucor-type Douchi were significantly higher than those in bacterial-type natto. Particularly, the Mucor-type Yangjinji and Huangyao Douchi contained the highest level of polyphenols (71.9±0.91) mg/100 g and aglycogenic isoflavones (2 925.4±12.32) mg/kg, respectively. The correlational analysis indicated that the polyphenol and aglycone isoflavone content were significantly (P<0.05) related to the ·OH scavenging activity and total antioxidant. And the pH value also could affect the antioxidant capacity of Douchi.
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  Effect of lactic acid bacteria fermentation on the characteristics of wheyprotein/blueberry juice system

  WANG Wenqiong, SUN Zhiyong, HUANG Dongcheng, ZHANG Jielong, ZHANG Zhixian, LI Ying, GU Ruixia

  Food and Fermentation Industries. 2020, 46(13): 42-48. https://doi.org/10.13995/j.cnki.11-1802/ts.023820

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  The mixture of blueberry juice and whey protein was used as raw material in this study. Then the effect of Streptococcus thermophilus and Lactobacillus bulgaricus fermentation system on precipitation rate, free amino content, color, pH, total phenol and anthocyanin content and the structure changes were investigated. Results showed that the color was slightly changed after 36 h fermentation with S. thermophilus and L. bulgaricus compared with control. Furthermore, the precipitation was reduced by 60% after 48 h. The contents of polyphenols and anthocyanins in the blueberry and whey fermented by L. bulgaricus system were the highest at 24 h and 36 h respectively compared with other fermented samples, and the content of free amino group was the highest at 48 h. In addition, L. bulgaricus could promote protein hydrolysis, while S. thermophilus could promote the binding of whey protein polypeptide with anthocyanin and polyphenol in blueberry juice.
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  Protein composition and degradation of Pixian board bean paste duringsweet petals fermentation stage

  LIN Hongbin, FANG Jiaxing, BI Xiaopeng, ZHOU Binbin, LIU Ping, DING Wenwu, CHE Zhenming

  Food and Fermentation Industries. 2020, 46(13): 49-54. https://doi.org/10.13995/j.cnki.11-1802/ts.023901

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  The protein composition and degradation of Pixian board bean paste were studied during sweet petals fermentation. Total protein content and four components(albumin, globulin, prolamin and glutenin of koji preparation (0, 3, 7 d) and brine fermentation (15, 30, 45, 60, 90 d) were studied, and the changes of protein subunits, peptides and free amino acids combined with the formation of flavor substances were analyzed. The results showed that the total protein content decreased from 31.25 g/100 g to 19.17 g/100 g. The contents of albumin and glutenin increased first and then decreased, and reduced to 7.72 g/100 g and 6.54 g/100 g at the end of sweet petals fermentation stage,respectively. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed that the degradation of albumin and glutenin was dominant in the first 30 days, and then did albumin. A total of 19 free amino acids were detected. After 90 days of fermentation, the total amount of free amino acids increased by 50.219 mg/g. The free amino acids with a high content throughout the fermentation process were alanine, glutamic acid, lysine, arginine leucine and valine(≥1 mg/g). The umami with sweet taste amino acids, umami with sour taste amino acids, and bitter taste amino acids groups increased to 11.829 mg/g, 16.140 mg/g, and 14.652 mg/g, respectively. This study provided scientific basis for improving the utilization rate of protein, increasing the flavor base material content, improving the product quality and the processing technology.
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  Functional properties of low-bitter soybean oligopeptides preparedby a novel tripeptidase

  WU Wenyu, ZHOU Jing, ZONG Hong, LU Xinyao, ZHUGE Bin

  Food and Fermentation Industries. 2020, 46(13): 55-61. https://doi.org/10.13995/j.cnki.11-1802/ts.023300

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  Soybean oligopeptides prepared by a novel tripeptidase and alkaline protease were analyzed. And its functional properties including solubility, degree of hydrolysis, bitterness, umami, antioxidant properties and anti-angiotensin converting enzyme (ACE) properties were deeply investigated. The results showed that the solubility and hydrolysis degree of soybean peptides prepared with tripeptidase and alkaline protease were 80.6% and 7.9%, respectively, which were 60.4% and 29.5% higher than that of the soybean peptides prepared with alkaline protease alone. The main molecular weight was 0.2-1 kDa and the component with a molecular weight of less than 1 kDa reached 81.8% which was 23.7% higher than the alkaline protease prepared-soybean peptides. Meanwhile, free amino acid content increased significantly. Furthermore, the content of sweet and umami amino acids in the free amino acids increased from 22.7% to 47.4%. However, 8.7% decline of bitter value was observed suggesting it was a low-bitter soybean oligopeptide. Moreover, DPPH, hydroxyl and superoxide free radical scavenging rates were increased 48.1%, 100% and 14.2% respectively compared with control. Meanwhile the soybean oligopeptides prepared by a novel tripeptidase and alkaline protease also exhibited good reducing power; the ACE inhibition rate reached 83.6%, which was 11.6% higher than that of soybean peptides prepared with alkaline protease. These results revealed that the double enzyme method (tripeptidase and alkaline protease) can significantly improve the functional properties of soybean oligopeptides, which indicating its potential application prospects of the tripeptidase in functional soybean peptide preparation.
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  Preparation of the acid-resistant freeze-dried Lactobacillus casei CCFM711

  OUYANG Biyan, CUI Shumao, MAO Bingyong, TANG Xin, MA Fangli, ZHAO Jianxin, ZHANG Hao, CHEN Wei

  Food and Fermentation Industries. 2020, 46(13): 62-68. https://doi.org/10.13995/j.cnki.11-1802/ts.023553

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  In order to improve the freeze-drying survival rate and the acid resistance of lyophilized powder of Lactobacillus casei CCFM711, cells were lyophilized with different acid-resistant materials, and with sugars and proteins as protectants for freeze-drying. The lyophilized cell powder was then tested and compared with the sodium alginate microcapsules prepared by the optimized emulsification method. Finally, the vacuum freeze-drying process was optimized. The results showed that stachyose combined with sodium alginate and sodium caseinate, respectively, could simultaneously improve the survival rate in freeze-drying and the acid resistance. Using stachyose as protectant for freeze-drying in preparation of sodium alginate wet microcapsules, the survival rate of bacteria in acidic environment could be significantly improved, but the acid resistance was significantly reduced, which was only (0.37±0.28) %, much less than un-coated lyophilized powder (19.56±1.83) %. Stachyose (100g/L) was used as the protectant for freeze-drying, and sodium caseinate (10 g/L) as the optimal wall material. Mixing the bacterial suspension and the protectants at the ratio of 2∶5, a freeze-drying survival rate of (59.43±6.28) % was obtained, while the highest survival rate was (34.16±7.18) % after 2 hours' treatment at pH 2.5, about 8 times of the control. This study provides guidance for the preparation of lyophilized powder of L. casei.
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  Effects of different fermentation methods on the physicochemicalproperties and flavor of pickles

  YUN Lin, MAO Bingyong, CUI Shumao, TANG Xin, ZHAO Jianxin, CHEN Wei

  Food and Fermentation Industries. 2020, 46(13): 69-75. https://doi.org/10.13995/j.cnki.11-1802/ts.023677

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  Three kinds of radish pickles were prepared by inoculated fermentation, brined fermentation and natural fermentation, and the physicochemical properties and flavor were investigated. After 96 h of fermentation, the pH values were all below 4.0. The acidity of pickles by inoculated fermentation and natural fermentation reached 5 g/L, and brined pickle increased from 4 g/L to 8 g/L. The inoculated pickle had the highest lactic acid bacteria count (>1×10⁸ CFU/mL). And the odor, taste and total scores were higher than the others. According to the GC-MS analysis, the content of fructose, tagatose and sucrose in the pickle by inoculated fermentation was higher than brined and natural fermented pickles. Moreover, the content of propylene glycol, glycerol, mannitol, lactic acid and oxalic acid in the brined pickle were higher than the other two methods, and specifically the amino acid species were more abundant. Dimethyl disulfide, dimethyl trisulfide, limonene, β-farnesene, 2-nonanone, 2-undecanone, linalool, and eucalyptol were identified as the key flavor active substances by SPME-GC-MS, and all these components were more abundant in the inoculated pickle.
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  Screening and aroma-producing characteristics of salt-tolerant aroma-producingyeasts from high-salt liquid-state Moromi

  PENG Dong, JIANG Xuewei, CHEN You, CHEN Jin, ZHANG Wei, ZHOU Hui, WU Can, FANG Qinjun

  Food and Fermentation Industries. 2020, 46(13): 76-84. https://doi.org/10.13995/j.cnki.11-1802/ts.023913

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  Salt-tolerant aroma-producing yeast can metabolize and synthesize volatile flavor compounds mainly composed of esters during the brewing process of soy sauce. Primary screening was performed by the transparent circle plate method. Secondary screening was implemented by analyzing total esters through bean sprout juice liquid fermentation with 100 g/L NaCl. Then, three salt-tolerant yeasts with good aroma-producing ability were obtained from high-salt liquid-state moromi. The strain CS2.23, CS2.42, and CS2.53 were identified as Millerozyma farinose, Zygosaccharomyces rouxii and Candida parapsilosis, respectively. The screened yeasts were added on the 30th day in high-salt liquid-state moromi during 60 days fermentation. Qualitative and quantitative analysis was performed for volatile flavor compounds by SPME-GC-MS. The results indicated that the esters content of soy sauce fermented by CS2.23, CS2.42, and CS2.53 were increased by 188.60%, 296.13% and 226.87% relatively, compared with the control group.Meanwhile,thecontentofalcohols, aldehydes, phenols, and others had also been improved. The major aroma compounds fermented by CS2.23 were ethyl acetate and 3-methyl-1-butanol, those of CS2.42 fermentation were ethyl acetate, phenethyl alcohol, 1-octen-3-ol, and phenylacetaldehyde. As for CS2.53, ethyl acetate, 4-ethyl guaiacol and 4-vinyl guaiacol were predominant. The three salt-tolerant yeasts provided different characteristic flavors for soy sauce brewing due to their different aroma characteristics.
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  Physicochemical components and antioxidant activity ofliquid and solid Jiaosu

  YU Sijie, OH YOUNG JOO, LI Hongjun, KIM TAE SUK, HE Zhifei, LEE SANG YUN, LI Shaobo, LI Minhan

  Food and Fermentation Industries. 2020, 46(13): 85-91. https://doi.org/10.13995/j.cnki.11-1802/ts.023681

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  A comparative analysis was conducted between liquid and solid Jiaosu (a fermented product rich in enzymes and active components ) in physical-chemical compositions, bioactive substances, and antioxidant activities. The results showed that the contents of total acid, reducing sugar, soluble solids, total polyphenol, total flavonoid, and anthocyanin in liquid Jiaosu products were significantly higher than those in solid Jiaosu. The activity of superoxide dismutase in liquid Jiaosu was between 193.23-1 214.46 U/mL, which was significantly higher than that of the solid one. However, the two kinds of Jiaosu products had low protease, lipase, and α-amylase activity, while almost no α-amylase activity could be detected in liquid Jiaosu. Jiaosu products showed strong antioxidant capacity, and liquid Jiaosu exhibited remarkable DPPH radical scavenging capacity (IC₅₀ values ranges from 5.65 to 21.08 μL/mL) which was stronger than solid Jiaosu (IC₅₀>29.77 μL/mL).The result in here provided a reference to understand the quality of Jiaosu products in different physical states, which played a guideline in contributing to the healthy development of Jiaosu industry.
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  Effect of Tween 20 interacting with proteins on the physical andoxidative stability of emulsions

  ZHANG Taiyu, HE Shan, ZHANG Yuqing, WANG Ning, HUANG Guo, SUI Xiaonan, JIANG Lianzhou

  Food and Fermentation Industries. 2020, 46(13): 92-98. https://doi.org/10.13995/j.cnki.11-1802/ts.023104

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  In this experiment, soy protein isolate (SPI) and walnut oil were used as the main raw materials. By adding different concentrations of small-molecule surfactants Tween 20, and preparing the oil-in-water (O/W) emulsion with high-pressure homogenization technology, the effects of emulsifiers containing protein and small-molecule surfactants on interfacial characteristics, physical and oxidative stability of emulsions were investigated. The results show that when the concentration of Tween 20 increases from 0 to 10 g/L, the particle size of the emulsion tends to be concentrated and gradually decreases, and the microstructure of the emulsion also obtains the same results; the Zeta potential and the surface tension decrease; During this period, the tryptophan fluorescence intensity of protein decreases, and the value of hydroperoxide and TBARS increase. The above results indicate that the increase of Tween 20 concentration in the emulsion improves the physical stability of the emulsion; however, the replacement of SPI at the interface by Tween 20 weakens the emulsion oxidation stability. This study of the effects of interfacial composition on the physical and oxidative stability of emulsions containing mixed emulsifiers provides a reference for the application of protein emulsion containing small molecule surfactants in food processing.
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  Chilling resistance of gibberellin-deficiency tomato fruits

  HUANG Xiaofei, QU Tongtong, DING Yang, LEI Tongtong, ZHANG Jie, TANG Xuanming

  Food and Fermentation Industries. 2020, 46(13): 99-106. https://doi.org/10.13995/j.cnki.11-1802/ts.023044

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  In order to identify the role of gibberellins (GAs) in the resistance of tomato fruits, the present study used the wild type (WT) and GA-deficient mutant (gib-3) tomato fruits at the mature green stage as raw materials and stored them at 4 ℃. The chilling injury (CI) index was measured, the ultra-structure of cells was observed, cell membrane damage intensity, as well as the activity changes of cell membrane lipase, cell wall degradation enzymes, and antioxidant enzymes of tomato fruits were determined. Results indicated that gib-3 tomato fruits showed more severe chilling symptoms and ultra-structural damage than WT tomato fruits. The MDA content, ion permeability and the activity of PLD, LOX, PG and PME of gib-3 tomato were increased. Cell membrane peroxidation and cell wall degradation of gib-3 tomato fruits accelerated, and their integrity of fruit cell membrane and cell wall was damaged. In addition, the activity of SOD, CAT, PAL and GST were decreased in gib-3 tomato fruits, and the ability of free radical scavenging reduced. According to the results, gibberellin deficiency at low temperatures was not good for tomato fruits to resist chilling injury. This study will provide a theoretical basis for the research on the chilling resistance mechanism of postharvest tomato fruits.
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  Synthesis and properties of Fe³⁺ probe based on ring-opening and ring-closing

  LI Changjiang, LI Qing, ZHANG Liyan, ZHENG Yuchuan, PAN Le, KE Zhongcheng, LI Bowen

  Food and Fermentation Industries. 2020, 46(13): 107-113. https://doi.org/10.13995/j.cnki.11-1802/ts.023795

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  Iron is an important trace element in the human body and plays an important role in human health. In this paper, a novel compound (named R1) has been synthesized by using rhodamine B, ethylenediamine and o-vanillin as raw materials. The structure of R1 was characterized by nuclear magnetic resonance and mass spectrum, and the properties just as ion selectivity, reaction complex ratio and sensitivity were tested. Results showed that R1 can selectively recognize Fe³⁺. As the color of the solution changed significantly, the fluorescence also changed. According to the calculation of job's plot curve, the complex ratio of R1 toward Fe³⁺ was 1∶1. Meanwhile, R1 for Fe³⁺ sensing had a remarkable low detection limit of 146 mmol/L (UV) and 129 mmol/L (fluorescence), which is far below the drinking water standards (0.3 mg/L) of China. Furthermore, the cellular imaging and cytotoxicity experiments demonstrated that R1 could be used for sensing Fe³⁺ in vivo due to its low cytotoxicity and good biocompatibility. Therefore, as a new type of visual fluorescent probe, R1 could be effectively applied to the content detection of Fe³⁺ in the fields of food safety, environment, biology, etc.
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  Establishment of tentative microbiological cut-off values and antibioticresistance analysis of Bifidobacterium longum

  ZHAO Fang, ZHAO Jianxin, ZHANG Hao, CHEN Wei, LU Wenwei

  Food and Fermentation Industries. 2020, 46(13): 119-126. https://doi.org/10.13995/j.cnki.11-1802/ts.023578

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  Bifidobacterium longum is a commonly used probiotic in food industry, and its drug resistance is related to food safety issues. The objective of this study was to formulate antibiotic resistance determination criteria for B. longum and to explore the key genes of antibiotic resistance through functional gene analysis. The minimum inhibitory concentrations of 52 B. longum strains towards tetracycline, erythromycin, clindamycin, ampicillin, chloramphenicol, and vancomycin were determined with reference to ISO standard methods (ISO 10932). The species-specific microbiological cut-off values of these six antibiotics of B. longum were evaluated by Turnidge (T) and Kronvall (K) statistical methods and analyzed the antibiotic resistance mechanism from the molecular genetic basis. The results showed that the species-specific microbiological cut-off values for tetracycline, erythromycin, clindamycin, ampicillin, chloramphenicol, and vancomycin of B. longum were 8, 8, 0.25, 8/2(T/K), 8 and 2 μg/mL respectively, and the drug resistance rates were 28.85%, 25%, 28.85%, 3.85%/7.69%(T/K), 0 and 19.23%. Functional gene and comparative genomic analysis revealed that tet(W) and erm(X) both located on mobile genetic elements were the main resistance genes for tetracycline resistance and erythromycin and clindamycin resistancein B.longum.Phylogeneticanalysis indicated that the tet(W) and erm(X) gene sequences of different phenotypic resistance strains possessed significant variation. This study has certain guiding significance and reference value for the safety application of B. longum in food and the development of evaluation criteria for probiotics resistance.
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  Inhibitory effect of Lactobacillus plantarum CCFM8724 oncaries-causing dual biofilms

  QIN Sujia, XU Wanqing, ZHANG Qiuxiang, ZHAO Jianxin, ZHANG Hao, CHEN Wei

  Food and Fermentation Industries. 2020, 46(13): 127-132. https://doi.org/10.13995/j.cnki.11-1802/ts.023436

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  The presence of Candida albicans in dental plaque with Streptococcus mutans enhances the virulence leading to the onset of rampant caries which is similar to early childhood caries (ECC). In order to verify the inhibitory effect of Lactobacillus plantarum CCFM8724 on the dual biofilm which infected by S. mutans and C. albicans at different time points in vitro, the treated biofilms were assessed for crystal violet staining, anthrone-sulfuric method and colony forming unit (CFU) counting. The live/dead bacteria and structure of biofilm were observed by laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Finally, the decalcification of saliva-coated hydroxyapatite discs (SHA) after culture with CCFM8724 and the tolerance of lysozyme were determined. The results showed that L. plantarum CCFM8724 could significantly reduce the biomass of dual biofilm, the production of water-insoluble extracellular polysaccharide (EPS) and the CFU of pathogens. It also reduced the viability of biofilm and destroyed the structure of biofilm. Moreover, it alleviated the decalcification of SHA with the tolerance concentration to lysozyme 1.6-2.0 mg/mL. It is suggested that CCFM8724 has the potential to be used as an oral probiotic for caries prevention.
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  Distillation conditions for the recovery and utilization of the tailliquor of strong-flavor Baijiu

  YUAN Huawei, WANG Lian, WANG Xin, ZHENG Jia, AN Mingzhe, QIAO Zongwei, LIANG Lu, LI Zhizhong

  Food and Fermentation Industries. 2020, 46(13): 133-139. https://doi.org/10.13995/j.cnki.11-1802/ts.023831

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  In order to make full use of the tail liquor of strong-flavor Baijiu, the method and conditions of distillation were studied by flavor analysis combined with sensory evaluation. The distillate was further applied for the blending of the Baijiu liquor, and the addition amount of distillate was evaluated by chromatographic analysis combined with electronic nose, electronic tongue detection and sensory evaluation. The results showed that the vacuum distillation was suitable for the recovery of alcohol and flavor substances in the tail liquor. The optimized distillation conditions were 80 ℃, 0.25 MPa, 120 r/min, and the amount of distillate was 40%. The ethanol in the distillate was completely distilled out and the alcohol concentration in final distillates was 46.82% vol. The content of ethyl lactate and aceticacidinthedistillatedecreased.Andisovaleraldehyde,butyricacid,isobutyl alcohol and isoamyl alcohol decreased slightly. However, other flavor substances increased slightly compared with the tail liquor. When the addition amount of distillate was less than 7%, no significant difference in typical aroma, flavor features and overall style was identified between the blended Baijiu and the original Baijiu. Vacuum distillation could greatly improve the utilization rate of the tail liquor of strong-flavor Baijiu, and this study provided a theoretical basis for the efficient utilization of liquor and flavor components in the tail liquor.
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  The influence of thickness of polymer microporous membrane filter onthe flavor of strong-flavor Baijiu

  JIANG Zhi, ZHAO Jinsong, SUN Yue, ZHANG Mingwen, LI Dan, HU Xue

  Food and Fermentation Industries. 2020, 46(13): 140-145. https://doi.org/10.13995/j.cnki.11-1802/ts.023585

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  High quality and low alcoholicity are the future development trends of Baijiu. To solve the technical problems of turbidity and influence on flavor during the production of low-alcoholicity Baijiu, seven polymer microporous membranes with different thicknesses were used to filter two strong-aroma type Baijiu with different alcoholicity. Principal component analysis and cluster analysis were conducted to evaluate the changes in chromatographic indices before and after filtration. Further, in addition to the changes in the physical and chemical indices, the effects of thickness of polymer microporous membrane filter on the turbidity removal and flavor of Baijiu were systematically studied. The optimal filtering thicknesses for 52%vol and 38%vol strong-aroma type Baijiu were 20 mm and 30 mm, respectively. These results have great significance in guiding the improvement of both the filtration process and the effect of Baijiu.
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  The change and correlational study of biochemical indices of TaoRong-Daqu during the process of production and storage

  CHEN Mengen, HAN Suna, HOU Jianguang, LI Jianmin, CHEN Weiping, LI Hua, DENG Jie, HU Xiaolong

  Food and Fermentation Industries. 2020, 46(13): 146-151. https://doi.org/10.13995/j.cnki.11-1802/ts.023213

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  Taking Tao Rong-type Daqu as the research object, the change and correlational study of biochemical factors of Tao Rong-Daqu during the production and storage were studied. The results showed that yeast, mold, and bacteria multiplied in large numbers. And the fermentation power, saccharification power, protease activity, acidity, and other indicators rose sharply during the initial stage of fermentation. In the middle stage of fermentation, the number of molds and yeasts decreased significantly, while some heat-resistant Bacillus species were predominant. At the end of fermentation, bacteria were predominated in Daqu. When stored for 120 d, the saccharification power, liquefaction power, fermentation power, protease activity and esterification power were up to 700, 0.8, 0.8, 40 and 20 U/g respectively. And the number of bacteria, yeasts, molds and spores were up to 1.4×10⁷ CFU/g, 1.9×10⁵ CFU/g, 2.0×10⁵ CFU/g, 5.6×10⁷ CFU/g. The correlational analysis showed that there was a positive correlation between acidity and the number of bacteria. And the same tendency was also been showed between saccharification power and mold count, fermentation power and yeast countrespectively.Meanwhile,therewerenegativecorrelationsbetweenwatercontentand time, starch content and time, water content and ammonia nitrogen. This work offered reference data for future research on microbial flora and their multi-enzyme system in Daqu. It also helps to improve the process of the production of Tao Rong-type Daqu and Tao Rong-type Baijiu.
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  Optimization of accelerated ageing of esters in brandy byultrahigh-pressure technique

  YAN Haokai, ZHANG Bo, LIU Qi, NIU Jianming, SHI Xiao, HAN Shunyu

  Food and Fermentation Industries. 2020, 46(13): 152-159. https://doi.org/10.13995/j.cnki.11-1802/ts.023784

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  Ageing is an important part to improve the quality of brandy, but long-term ageing limits the rapid production and large-scale promotion of brandy at present. And all current ageing techniques had defects. To expand the methods of brandy ageing, ultrahigh-pressure technique be used and key parameters of ultra-high pressure treatment was optimized by single factor and response surface methodology. The optimized parameters were 309 MPa at 25 ℃ for 51 min. In this condition, the total ester reached 0.86 g/L. The evaluation test showed that with the optimized ultra-high pressure ageing treatment the same result could be achieved as the effect of six years of conventional ageing. And the heat map clustering analysis showed that the main ester aroma substances in brandy obtained by ultra-high pressure could basically reach the effect of 6 years of conventional ageing. Besides, ultra-high pressure treatment had different ageing effect on the content of different ester aroma substances. Therefore, ultra-high pressure technique has a great application prospect in the ageing of esters in brandy. The results provide data support on the development of brandy ageing method and the application of ultra-high pressure technique in brandy ageing.
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  Color change of caramel malt during roasting process at three lowroast temperatures

  HAO Junguang, MO Xiaodan, CHEN Jing, QIU Yanxing

  Food and Fermentation Industries. 2020, 46(13): 160-165. https://doi.org/10.13995/j.cnki.11-1802/ts.023714

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  To better understand the color change of caramel malt at low-temperature roasting process under different mashing conditions, CIE L^*a^*b^* was used to compare the color characteristics of 50%(mass ratio) congress wort, 10% congress wort, 10% saccharification wort mashed at 65 ℃ and its resultant boiling wort under laboratory conditions. The results indicated that the production of yellow colorant was earlier than the red one in roasting. The a^* and b^* showed different changing tendency in distinctive molds which reflecting the complexity of non-enzymatic browning in the roasting process. The variation patterns of a^* and b^* in congress wort of 10% caramel malt were significantly different from those of 50% formula. The change mode of a^* and b^* in the boiling process of 10% caramel malt formula wort with 65 ℃ mashing temperature was also varied from that of 50% congress wort, and its color increased obviously during boiling. With the regard of the fact that 10% ratio of caramel malt is the common ratio for commercial production, it is more instructive to use the 10% EBC wort protocol to evaluate the color characteristics of caramel malt. Boiling the 10% formula wort mashed at 65 ℃ can better provide the reference for the selection of caramel malt and formula screening of beer with specific color characteristics.
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  Effects of interaction of hydrogen sulfide and nitric oxide on postharvestquality and antioxidant system of banana

  CUI Wenyu, XU Xinyue, ZHANG Rentang, GONG Zhiqing, WANG Wenliang, WANG Yansheng

  Food and Fermentation Industries. 2020, 46(13): 166-173. https://doi.org/10.13995/j.cnki.11-1802/ts.023598

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  As important signaling molecules, hydrogen sulfide (H₂S) and nitric oxide (NO) form a complex plant signal network with other signal molecules. In order to further explore the effects of H₂S, NO and their interactions on banana's quality and antioxidant system in low temperature storage, bananas were stored at 7 ℃ for 15 d after treatment with 1 mmol/L H₂S, 2 mmol/L NO, 0.03 mmol/L c-PTIO (NO inhibitor) and distilled water. The results show that H₂S can significantly increase the NO content. Both H₂S and NO treatments can maintain the hardness of banana fruits, inhibit the increase of malondialdehyde (MDA) content and relative conductivity, reduce the chilling injury index, and maintain good gloss and smoothness of banana peel Bright colors. The effect of NO and H₂S treatment is better than that of distilled water and c-PTIO treatment. Both NO and H₂S treatment can increase the superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbic acid levels in banana fruits, as well as antioxidant enzyme activities such as oxidase (APX) and phenylalanine ammonia lyase (PAL), thereby reduces tissue oxidation levels and inhibiting membrane lipid oxidation processes. Among them, the effects of NO and H₂S treatment were significant in the pre-storage period, while the effect of c-PTIO treatment was the worst. It can be seen that the interaction of H₂S and NO plays an important role in inducing cold tolerance in bananas.
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  Evaluation of antioxidant activity of Vc@SeNPs and its effect on thequality of fresh-cut apples

  LI Changjiang, ZHU Shanshan, WANG Na, NIE Mengjiao, ZHENG Guodong, YANG Licong

  Food and Fermentation Industries. 2020, 46(13): 174-181. https://doi.org/10.13995/j.cnki.11-1802/ts.022606

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  The objective of this work was to develop fruit and vegetable preservatives that can supplement human selenium nutrients and maintain the excellent quality of fresh-cut apples. Firstly, ascorbic acid (Vc) was used as the reducing agent and surface modifier in the formation of Vc modified nano-selenium (Vc@SeNPs). Then, the morphology and chemical composition of the nanoparticles was characterized using UV-Vis, Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscope (TEM). Subsequently, the antioxidant capacity of Vc@SeNPs was evaluated by in vitro free radical scavenging indicators, and the effect of Vc@SeNPs on the quality of fresh-cut apples at room temperature (25 ℃) was also examined. The results showed that Vc@SeNPs has uniformly dispersed with spherical morphology and an average particle size of 64.80 nm. The antioxidant results showed that Vc@SeNPs has antioxidant activity. The IC50 of hydroxyl, superoxide and DPPH free radicals scavenging ability is 0.10, 0.24, and 0.50 mg/mL, respectively. Moreover, the reducing power of Vc@SeNPs is stronger than Vc. In maintaining the sensory value and quality of fresh-cut apples, Vc@SeNPs treatment is better than Vc. 10 g/L Vc@SeNPs has the best effect ondelaying the browning of fresh-cut apples; 50 g/L Vc@SeNPs could effectively prevent the oxidation of polyphenols and reduce the water loss in fresh-cut apples. However, in the distilled water group, fresh-cut apples browned rapidly with a large amount of water loss and severe polyphenols oxidation. Hence, Vc@SeNPs is expected to be a new fruit and vegetable preservative.
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  Fouling behavior of soy milk in plate heat exchanger

  ZENG Qingjun, HUA Yufei, CHEN Yeming, KONG Xiangzhen

  Food and Fermentation Industries. 2020, 46(13): 182-189. https://doi.org/10.13995/j.cnki.11-1802/ts.023189

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  When soy milk is heated by a heat exchanger, deposits are formed on the heat exchange surface, thereby affects its heat exchange efficiency. In this study, a small plate heat exchanger system was first assembled. The fouling behavior and compositions of deposit by soy milk with a protein concentration of 3.50% at 105-125 ℃ were studied at different pH and different feed temperatures. The results showed that when the pH of soy milk was ≥6.5, the overall heat transfer coefficient (U) and fouling factor (R_f) showed a gradual change with heating time. At pH 6.3, U and R_f showed a mutation process at about 90 min. The fouling factor of the soy milk increased with the increase of the feed temperature. According to the composition analysis of the deposits, as the pH and feed temperatures of the soy milk decreased, the protein and fat content in the sediment gradually increased, while the ash content gradually decreased. From the perspective of alleviating fouling problems, the first is to ensure that the pH of the soy milk is near neutral, and the second is that the soy milk directly enters the heating section without preheating.
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  Effect of micronized sweet potato residue powder on dough properties

  YIN Xumin, LIU Yueru, YANG Mao, LI Xiaoying, ZENG Zhihong, ZENG Xiaofeng, SHANG Sang

  Food and Fermentation Industries. 2020, 46(13): 190-195. https://doi.org/10.13995/j.cnki.11-1802/ts.023804

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  In order to study the effect of different amounts of micronized sweet potato residue powder (MSPRP) on dough properties, the micronized sweet potato residue powder was mixed with wheat flour in different proportions (2%-12%). The thermomechanical properties, texture properties, color and dough structure of different flour dough were measured by Mixolab, texture instrument, colorimeter and scanning electron microscope. The results showed that with the increasing amount of sweet potato residue powder, water absorption and stability time of dough were increased, and formation time, weakening grade and setback value of dough were decreased; while peak viscosity, disintegration viscosity and hydrolytic rate of starch of dough were reduced firstly and then increased, when reconstituted doughs made with 8% MSPRP showed lower hydrolytic rate of starch. Meanwhile, hardness, adhesiveness and chewiness of reconstituted doughs were gradually increased, the cohesion and reversion were increased firstly and then decreased. Compared with wheat dough, MSPRP reconstituted dough exhibited worse qualities. Moreover, the color of reconstituted dough became gray and dark; the lightness L^*, a^* and b^* of reconstituted doughs were decreased, and ΔE was increased. The microstructure of dough showed that addition of MSPRP destroyed the smooth and uniform of the gluten network, resulting in increasing exposed starch grains gradually. In conclusion, the addition of MSPRP could destroy the gluten protein network structures and this might influence the changing of rheological properties of the dough; changes of wheat dough characteristics with 4% to 8% MSPRP were acceptable.
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  Study on the technology of emulsifying curcumin in phospholipids oflarge yellow croaker roe

  HUANG Luyao, DU Yanyu, LU Xiaodan, LIANG Peng, CHEN Lijiao, CHENG Wenjian

  Food and Fermentation Industries. 2020, 46(13): 196-202. https://doi.org/10.13995/j.cnki.11-1802/ts.023888

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  In order to verify the emulsifying properties of large yellow croaker roe phospholipids (LYCRPLs), the curcumin was emulsified by LYCRPLs, and the preparation conditions were investigated in terms of emulsion particle size and stability. The emulsifying processing was optimized based on the single factor experiments via response surface methodology. Meanwhile, the emulsion was characterized by transmission electron microscope (TEM). Afterward, the emulsion stability was also investigated. The results showed that the optimum conditions were as follows: homogenization pressure was 724 bar, homogenization time was 141 s, LYCRPLs concentration was 4.275% and oil concentration was 12.89%. Under the above conditions, the emulsions particle size is (0.216±0.0059) μm. The emulsion particles are almost spherical and possess obvious oil-in-water structure. In addition, the LYCRPLs-curcumin emulsion is stable without delamination and aggregation at 5 and 25 ℃ after 4 weeks. The results are meaningful to make high-value utilization of processing by-products of large yellow croaker.
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  Effects of ultrasonic treatment on the sterilization and quality of blueberry juice

  CHU Wenjing, YE Shuangshuang, ZHANG Fulong, WANG Xian, SHANG Chuanxian

  Food and Fermentation Industries. 2020, 46(13): 203-208. https://doi.org/10.13995/j.cnki.11-1802/ts.023927

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  The effects of ultrasonic treatment on the sterilization and quality of blueberry juice were studied. The results showed ultrasonic treatment including ultrasonic power, ultrasonic time, ultrasonic temperature had a significant effect on the sterilization rate of blueberry juice. The sterilization rate of blueberry juice reached 64% when ultrasonic conditions were 180 W of ultrasonic power, 8 min of ultrasonic time, and 40 ℃ of ultrasonic temperature. As the ultrasound power and ultrasound time increased, total phenol content increased and anthocyanin content decreased, but the DPPH radical scavenging rate of blueberry juice remained unchanged. When the ultrasonic temperature was higher than 40 ℃, the radical scavenging rate of DPPH blueberry juice decreased significantly. Ultrasound treatment has little effect on soluble solids, pH and color of blueberry juice.
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  Preparation and properties analysis of arrowhead starch oxidizedby H₂O₂/CuSO₄

  JI Derong, LEI Min, XIE Jianming, DUAN Lili, GUI Chao

  Food and Fermentation Industries. 2020, 46(13): 209-216. https://doi.org/10.13995/j.cnki.11-1802/ts.023691

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  In this paper, arrowhead starch was modified by wet oxidation with hydrogen peroxide (H₂O₂) as oxidant and copper sulfate (CuSO₄) as the catalyst. And the properties of starch before and after oxidation were discussed. Single factor experiments were designed to investigate the effects of additive amount of H₂O₂, CuSO₄, pH value and reaction time on the oxidation of arrowhead starch. Based on the single factor experiment, the carboxyl content and transparency of starch were taken as the response value to design the response surface experiment so as to optimize the preparation process, and the properties of arrowhead starch before and after oxidation were tested. The best oxidation process was obtained as follows: 31.6 ml of H₂O₂ was added into starch emulsion solution (100 g, 40%, w/w) to have pH at 8.35, the amount of CuSO₄ was 0.04% of the dry basis, and the reaction time was 4 hours at 45 ℃. The carboxyl content of the oxidized arrowhead starch was 0.355%, and the transparency was 52.6%. The solubility and swelling degree of oxidized starch increased significantly with the increase of temperature. The coagulability of oxidized starch was better than before; the freeze-thaw stability was worse; the viscosity was lower, and the gelatinization temperature of starch became lower. The particles were broken greatly and the shape increased; in the infrared spectrum, the absorption peak of 1 760-1 660 cm^-1 was sharper and stronger, and the carboxyl vibration was enhanced. The X-diffraction characteristic diffraction peak of oxidized starch became higher, and the crystallinity increased from 44.80% to 55.11%. In conclusion, the arrowhead starch oxidized by H₂O₂/CuSO₄ has high carboxyl content and high transparency. At the same time, the physical and chemical properties, particle state and crystal structure change, which provides a theoretical basis for the development and utilization of the oxidized arrowhead starch.
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  Effects of freezing rates on quality of baked sweet potatoes

  XU Mao, XIANG Min, WANG Zihan, JIANG Heti

  Food and Fermentation Industries. 2020, 46(13): 217-224. https://doi.org/10.13995/j.cnki.11-1802/ts.023770

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  The effects of four freezing methods on the quality of baked sweet potatoes were studied. The baked sweet potatoes were treated by -18 ℃, -25 ℃, -60 ℃ refrigerator freezing and liquid nitrogen quick-freezing, respectively. The changes of physical and chemical indicators, including starch, fat, reducing sugar, ascorbic acid, carotene, L^*, hardness, chewiness and maximum shearing force, were analyzed, and the freezing curves were described. Correlation analysis and principal component analysis were used to evaluate the nutritional quality of the baked sweet potatoes under different freezing rates. Results showed that the time of liquid nitrogen through the maximum ice-crystal formation zone was shortest, and its texture characteristics were closest to fresh-baked sweet potatoes. The preservation for major quality parameters and color was best after freezing at -60 ℃ compared with other freezing methods. Correlation analysis approved that there was a certain correlation among most quality indexes, and the influence of chewiness on the baked sweet potatoes quality was greatest. Principal component analysis indicated that 11 quality characteristics were consolidated into three principal components, and the cumulative variance contribution rate was 93.94%, which reflected the most information of baked sweet potatoes. Protein, chewiness, elasticity and reducing sugar and carotene were selected as the core indexes to evaluate the comprehensive quality of baked sweet potatoes. In a word, -60 ℃ refrigerator freezing is beneficial to maintain the nutritional quality of pre-frozen baked sweet potatoes. The present study provides data support for the comprehensive evaluation and further research and production of pre-frozen roasted sweet potatoes.
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  Analysis of quality differences between manual and machine-made yak butter

  MA Yanqing, LUO Jingwen, WANG Hongwei, SUO Huayi, SONG Jiajia, ZHANG Yu

  Food and Fermentation Industries. 2020, 46(13): 225-229. https://doi.org/10.13995/j.cnki.11-1802/ts.023990

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  Yak butter is a traditional food for Tibetan herdsmen. Market research found that herdsmen prefer manual yak butter. The purpose of this paper is to find the difference in quality between manual and machine-made yak butter. The basic physical and chemical indexes, texture, fatty acid, Sn-2 fatty acid and volatile components of yak butter were analyzed by high performance liquid chromatography, gas chromatography, gas chromatography, texture analyzer and other experimental techniques in this study. The results showed that the moisture content was 13.32 g/100 g, fat content was 83.49 g/100 g, the wiredrawing length was 0.24 mm and viscosity was 5.84 mJ of manual yak butter. They were significantly higher than those of machine-made yak butter (P<0.05). The number of volatile components of some manual yak butter was greater than that of the machine-made yak butter, and the flavor substances were more abundant. It indicated that the taste of manual yak butter was better than that of machine-made yak butter. However, the nutritional index of machine-made yak butter was better than that of manual yak. The protein content was 2.23 g/100 g, unsaturated fatty acid content was 37.52% and Sn-2 palmitic acid content was 41.10% of machine-made yak butter. They were significantly higher than those of manual yak butter (P<0.05). The results of this study can provide theoretical references for the quality improvement of mechanical yak butter.
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  Quality analysis of eight commercial Pixian broad bean-chili pastes

  FAN Zhiyi, DENG Weiqin, LI Heng, YANG Guohua, LI Jiezhi, ZHAO Zhishuai, CHEN Gong

  Food and Fermentation Industries. 2020, 46(13): 230-236. https://doi.org/10.13995/j.cnki.11-1802/ts.023629

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  In order to clarify the quality of different brand of Pixian broad bean-chili pastes, the quality of eight commercial Pixian broad bean-chili pastes were analyzed. National standard analysis methods were used to determine the contents of moisture, sodium chloride, amino nitrogen, total acidity and reducing sugar. A water activity meter was used to determine the water activities of samples, and HPLC were used to detect biogenic amines. Volatile compounds were extracted by headspace solid phase microextraction and analyzed by GCMS. The results showed that basic quality of the eight samples were consistent with the recommended level in the national standard and histamine, putrescine, tyramine and cadaverine were the main biogenic amines. While, biogenic amine of one sample was more than 1 700 mg/kg indicating its safety risk even though the other samples were lower than 300 mg/kg. Furthermore, 104 kinds of volatile compounds were detected and esters, alcohols and phenolic compounds were predominated. Different commercial Pixian broad bean-chili pastes showed great differences on quality, however, there was no obvious difference between the traditional one and red oil flavored Pixian broad bean-chili pastes.
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  A comparative study between Microbio method and plate counting methodon colony counting

  GUO Jia, WANG Ping, ZHOU Jifu, ZHAO Xiaomei, LIU Jifeng, CHEN Ying

  Food and Fermentation Industries. 2020, 46(13): 237-243. https://doi.org/10.13995/j.cnki.11-1802/ts.023190

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  In order to compare the difference between the automatic colony counting (Microbio) method and the ordinary plate counting method, ten bacteria strains were added to food samples at high, medium and low concentration. And the standard methods of GB 4789.2—2016 and GB 4789.15—2016 were used for colony counting as control. Data accuracy, quantitative limit, the detection time, personnel operation error and different media were compared and analyzed. In terms of data accuracy, personnel operation error and different media, the recovery rate of the two methods were all over 70% and the relative standard deviation (RSD) ≤0.35. When the detection limit ≥5 CFU/mL, the recovery rate ≥70% and the RSD ≤0.35 respectively. The results showed that no significant difference was found between the automatic colony count method (Microbio) and the ordinary plate count method and the quantitative limit could reach 5 CFU/mL. But in terms of the detection time, the automatic colony count method (Microbio) was superior to the ordinary plate method.
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  Analysis and evaluation of nutritional components of four types ofmarine aquatic roes

  ZHENG Tingting, ZHOU Jing, WENG Xin, CHEN Lijiao, CHENG Wenjian, PANG Jie, LIANG Peng

  Food and Fermentation Industries. 2020, 46(13): 244-249. https://doi.org/10.13995/j.cnki.11-1802/ts.023891

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  In order to analyze the nutritional composition of different types of marine aquatic roes, the basic nutrient content, fatty acids, amino acids and mineral elements of large yellow croaker, squid, anglerfish, and capelin roes were determined. The results showed that the water content (6.69±0.29) g/100 g of squid roes was the highest, while the water content of large yellow croaker roes (2.23±0.18) g/100 g was the lowest. The raw fat (18.88±0.06) g/100 g and ash content (14.75±0.13) g/100 g of capelin roes were the highest. Squid roes have the highest crude protein content (89.49±0.38) g/100 g, and the crude fat content is low, which is a high-quality low-fat high-protein food resource. The roes have high contents of phosphorus (P), calcium (Ca), zinc (Zn) and iron (Fe). In addition to tryptophan, valine was the first restricted amino acid of all four types of aquatic roes. The ratio of essential amino acids (EAA) to total amino acids (TAA) of the four types of aquatic roes is between 36.9% and 47.6%. All the mentioned roes are rich in EPA and DHA, among which the content of EPA and DHA is between 33.69% and 43.78%. The results suggest that all the aquatic roes are rich in nutrient elements, and have great potential for further development and utilization.
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  Rapid discrimination of Lycium barbarum L. from Ningxia and Qinghaibased on multi-element analysis combined with chemometrics

  LIAN Siyu, XIE Yujie, ZHANG Zijuan, FAN Chunlin, WANG Minglin, CHEN Hui

  Food and Fermentation Industries. 2020, 46(13): 250-254. https://doi.org/10.13995/j.cnki.11-1802/ts.023771

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  Microwave digestion and inductively coupled plasma mass spectrometry (ICP-MS) were used to determine 44 trace elements in 180 Lycium barbarum L. samples from Ningxia and Qinghai provinces. Nine elements (Sb, La, Tb, Lu, Al, Sc, V, Cr and Se) with significant differences were selected for PCA by element content screening. The results showed that the first two main components could explain 64.2% of the variable, meanwhile the L. barbarum L. samples could be basically distinguished from Ningxia and Qinghai. Based on nine elements with significant differences, the discriminant models of L. barbarum L. from Ningxia and Qinghai were established by partial least squares discriminant analysis (PLS-DA) and back propagation artificial neural network (BP-ANN). In the PLS-DA model, when 100% L. barbarum L. samples were used, the sensitivity and specificity of the model were 100% and 97.5%, respectively. When 75% L. barbarum L. samples were used, the sensitivity and specificity of the model were 98.6% and 98.4%, respectively, and the accuracy of the model was 100% for predicting the remaining 25% L. barbarum L. samples. In the BP-ANN model, when 100% and 75% L. barbarum L. samples were used, the specificity and sensitivity of the model were both 100%. The accuracy of the model was 100% for predicting the remaining 25% L. barbarum L. samples. The sensitivity and specificity of BP-ANN model were better than PLS-DA model. The results showed that the determination of multiple elements in L. barbarum L. by ICP-MS combined with chemometrics could quickly identify L. barbarum L. from Ningxia and Qinghai.
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  Analysis of the flavor compounds in fast-fermented fish sauce fromtilapia by-products during fermentation

  BIAN Hao, CHEN Boyu, DU Jinjing, CHEN Zhiyan, LI Rui

  Food and Fermentation Industries. 2020, 46(13): 255-261. https://doi.org/10.13995/j.cnki.11-1802/ts.024053

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  In order to investigate the change of flavor compounds in fast-fermented fish sauces during fermentation, tilapia by-products were used as raw material, and fast-fermented fish sauces were prepared by adding mixed protease and soy sauce koji. Flavor compounds of fish sauces during fermentation were analyzed by physicochemical characteristics. The results showed that total nitrogen and amino nitrogen exhibited an initial increase and a final decrease with fermentation time, and reached the peak (1.82 g/100 g and 1.46 g/100 g) at the 3rd and the 5th week, respectively. Among inorganic ions, the content of Na⁺, Cl^- and PO^3-₄rose slightly, while the content of K⁺and Ca²⁺changed little, and the content of Mg²⁺ decreased slowly. Among free amino acids, the content of umami and sweet amino acids increased rapidly in prior period of fermentation, reached the highest value (4 692.16 g/100 g) at the 5th week, and then decreased gradually. The content of bitter amino acids increased greatly in the late fermentation stage, the content of lysine and arginine increased by 14.27 and 17.75 times at 8th week comparing with that of unfermented samples. Among organic acids, the content of the lactic acid, citric acid, acetic acid and succinic acid increased during fermentation. The content of acetic acid and succinic acid increased by 3.46 and 2.18 times at 8th week, respectively. Among flavor nucleotides, the content of AMP and Hx increased greatly and reached to the highest value (169.26 mg/100 g and 323.18 mg/100 g) at 6th and 8th week respectively. The change of equivalent umami concentration exhibited an initial increase and a final decrease during fermentation, and reached to the highest value (17.59 g MSG/100 g) at 6th week. This study provided theoretical support for techniques optimization and quality control of fast-fermented fish sauce from tilapia by-products.
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  Research progress on hypoglycemic effect and mechanism of capsaicin

  ZHANG Shiqi, TANG Lanlan, SUN Jinyi, YANG Juan, HUI Yonghai

  Food and Fermentation Industries. 2020, 46(13): 262-269. https://doi.org/10.13995/j.cnki.11-1802/ts.023790

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  As one of the most widely consumed vegetables and spices in the world, chili pepper not only gives food a special flavor, but also has unique physiological functions. A large amount of research evidence indicates that as one of the natural active ingredients extracted from chili pepper, capsaicin has significant effects in preventing and treating diabetes and complications. The anti-diabetic effect of capsaicin and its mechanism of action are described from five aspects: regulation of glucose metabolism, improvement of pancreatic function, mediation of TRPV1 (transient receptor potential vanilloid 1) ion channels, regulation of endocrine system, and intestinal flora. Simultaneously, the paper evaluates the potential of capsaicin as an anti-diabetic drug or adjuvant, intending to provide a theoretical basis for subsequent research on the prevention and treatment of diabetes.
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  Progress in nano- and micro- particle-stabilized foams and theirimplications in food technology

  LI Mengsa, ZHAO Guohua, YE Fayin

  Food and Fermentation Industries. 2020, 46(13): 270-279. https://doi.org/10.13995/j.cnki.11-1802/ts.023695

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  The foam is a dispersion system in which gas is dispersed in a liquid or semi-solid phase, and plays an important role in the formation of the qualities such as texture, appearance, and consumers' acceptability of interface-dominated foods like cakes, ice cream, beverages, and whipped cream. Due to their unique surface/interface characteristics and controllable morphology and size, food-grade nano- and micro- particles have attracted a lot of attention for their potential to suspending, emulsifying, and foaming and other interfacial effects in complex food systems. The interface characteristics, preparation methods and foaming process of such kinds of food particles were reviewed. The properties of the particles-stabilized foams were expounded. Meanwhile, related technical methods based on particles' characteristics design for the improvement of foam stability were discussed. The food use of the particles and the foams created by them was elaborated. The review is expected to provide a reference and theoretical basis for the development of new food foaming agents and analysis of the quality formation mechanism of foamed food which is mediated by nano- and micro- particles.
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  Application of metabolomics in detection and analysis of plant polyphenols

  YU Miao, WANG Changyuan, WANG Xia

  Food and Fermentation Industries. 2020, 46(13): 280-285. https://doi.org/10.13995/j.cnki.11-1802/ts.023747

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  Metabolomics is a new discipline that conducts a qualitative and quantitative analysis of all low-molecular-weight metabolites of a certain organism or cell in a specific physiological period. It is an emerging "omics" after genomics, proteomics, and transcriptomics. Plant metabolomics is regarded as an important branch of metabolomics. Polyphenol is a substance with high content and many functional activities in plants. It is a secondary metabolite in plant metabolism. The application of metabolomics in the study of polyphenols is more helpful in explaining the mechanism of their functional activity based on qualitative and quantitative analysis. Moreover, it is beneficial to the research and application of polyphenols. This review discussed the application of metabolomics technology in the qualitative and quantitative detection of polyphenols, summarized the application of qualitative and quantitative polyphenols in different processing methods, production regions, quality grades, and polyphenol functional activities, as well as the application of multi-omics technology to the functional activity of polyphenols.
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  Research progress on the mechanism of bile salt hydrolase in probiotics

  TANG Hongyu, SONG Xin, XIA Yongjun, AI Lianzhong, WANG Guangqiang

  Food and Fermentation Industries. 2020, 46(13): 286-292. https://doi.org/10.13995/j.cnki.11-1802/ts.023950

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  Bile salt hydrolase (BSH) is a kind of metabolite, which is produced by microorganisms during the period of growth and reproduction. This enzyme has the ability to catalyzes hydrolysis of conjugated bile salts into amino acid and bile acids. A number of studies have shown that probiotics can increase the survival rate and stability in the intestine through BSH. Moreover, probiotics can achieve part of potential health-promoting functions by BSH participating in the regulation of bile acids, such as cholesterol lowering. Therefore, BSH in probiotics has always been a research hotspot. In order to understand BSH deeply, this article mainly reviewed the research progress on characteristics, distribution, physiological functions, and its role in reducing cholesterol and alleviating inflammatory bowel disease, aiming at providing theoretical basis in food, Health products and clinical applications of BSH-producing probiotics.
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  Research progress in the application of Clostridium butyricum and itsmetabolites in food processing

  FU Junjie, LI Li, LIU Jun, LIAO Ting, TIE Yu, WEN Xueping

  Food and Fermentation Industries. 2020, 46(13): 293-298. https://doi.org/10.13995/j.cnki.11-1802/ts.023798

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  Clostridium butyricum is a typical anaerobic Clostridium probiotic with good stability, strong adaptability and safe. It was widely used in medicine and feed industries. However, up to date, there was less research on food production and the processing of food raw materials. This paper reviewed the biological traits and physiological function of Clostridium butyricum,and summarized the application of its metabolites in food processing including flavor additive, antiseptic, antioxidant effects and vitamin fortification. Finally, the problems and prospects of its metabolites in the food industry were discussed.
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  Application mechanism and research progress of gaseous and liquidnitrogen in food processing

  CHENG Lina, YU Yuanshan, WU Weijun, ZOU Ying, ZOU Bo, LI Jun, XU Yujuan, XIAO Gengsheng

  Food and Fermentation Industries. 2020, 46(13): 299-304. https://doi.org/10.13995/j.cnki.11-1802/ts.023936

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  This paper reviewed the application mechanism and research progress of gaseous and liquid nitrogen in food processing, including modified atmosphere package, cold plasma and modification, gas hydrate concentrating, and liquid nitrogen freezing, according to the properties of environment adjustment, ionization, crystallization, and gasification. The physical and chemical characteristics of gaseous and liquid nitrogen were introduced. The application mechanism, current state, and future challenge of the above technologies were analyzed. Cold plasma and modification and gas hydrate concentrating were belonged to novel technique and mainly stay in the lab the research stage, but with the wonderful prospect; the emphasis of future work was to enlarge the research objects, expand the application scope and develop stable devices. Modified atmosphere package and liquid nitrogen freezing have been applied in the industrial process, however, due to the complicated properties of food and upgrade requirements of consumers, both of them still need to be improved, which include the combination of other techniques and diversification and scale of equipment.
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  Analysis of utilization status and application prospect of yak skin in food field

  WU Qian, LIU Fangfang, MIAO Yu, LYU Lili, CHEN Yi, ZHAO Zhifeng

  Food and Fermentation Industries. 2020, 46(13): 305-309. https://doi.org/10.13995/j.cnki.11-1802/ts.024034

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  Yak skin, a by-product of yak processing, has rich collagen and important nutritional value. As a potential food raw material, most of the yak skin is used to produce leather products, except for a small part of which is used to prepare yak leather. This not only wastes the nutritional value of yak skin, but also easily causes environmental pollution. Therefore, exploring the application of yak skin in the food field and enhancing the added value of yak skin is of great significance for increasing the economic value of yak skin. This article elaborates on the nutritional content and characteristics, utilization status and application prospects of yak skin, and focuses on the development direction of yak skin, to provide a theoretical basis and reference for the development and use of yak skin in food field.
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  Research progress on processing technology and quality analysis ofapricot fruit wine

  MA Qian, XU Jia, ZUO Yong, XU Nuqian, HU Kun

  Food and Fermentation Industries. 2020, 46(13): 310-314. https://doi.org/10.13995/j.cnki.11-1802/ts.023877

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  In recent years, apricot is widely concerned because of its rich nutritional content, and the variety of related products is gradually increasing. Apricot fruit wine is a kind of low-alcohol beverage made from apricot. It retains most of the nutrients and unique flavor components of apricots. According to domestic and foreign research, the product development and quality research status of apricot fruit wine from the aspects of optimization of fermentation conditions, breeding of strains, quality optimization, stability control, nutritional and flavor components analysis were summarized in this review. The shortcomings of the existing studies on apricot fruit wine, such as the lack of research on browning mechanism and control measures, reduction of acidity, stability control, flavor composition analysis, establishment of relevant standards, etc., were also pointed out. In addition, the future research direction and development prospect were also discussed to provide theoretical reference for the product development and industrialization of apricot fruit wine.