The hydrogen bonding was prone to be formed by many components in beer. Different sorts of flavor substances can affect the Chemical Shift due to their different concentrations in beer. Several key factors including 4 alcohols, 2 esters, 6 ions, 9 acids, 7 polyphenols, and 2 gravity indexes (OG and RG) were determined in this research. They could be used to investigate the relationship between hydrogen bonding intensity and the flavor components in bottled larger beers through the Correlation Analysis, Principal Component Analysis and Multiple Regression Analysis. Results showed that ethanol content was the primary influencing factor, and its correlation coefficient was 0.629 for Correlation Analysis. Some factors had a positive correlation with hydrogen bonding intensity, including the content of original gravity, ethanol, isobutanol, Cl−, K+, pyruvic acid, lactic acid, gallic acid, vanillic acid, and Catechin in beer. A mathematic model of hydrogen bonding Chemical Shift and the content of ethanol, pyruvic acid, K+, and gallic acid was obtained through the Principal Component Analysis and Multiple Regression Analysis , with the adjusted R2 being 0.779 (P = 0.001). Ethanol content was proved to be the most important factor which could impact on hydrogen bonding association in beer by Principal Component Analysis. And then, a multiple non-linearity model could be obtained as follows: \( hydrogen\,bonding\,association\,intensity\,(CS) = 4.917 + 0.002\left[ E \right] - 0.006\left[ P \right] + 5.141E - 8\left[ {{K^2}} \right] + 5.378E - 5\left[ {G \times P} \right] + 2.428E - 5\left[ {K \times P} \right] + 2.369E - 5\left[ {{E^2}P} \right] - 1.63E - 5\left[ {{G^3}} \right] - 2.207E - 5\left[ {{P^3}} \right] - 5.247E - 7\left[ {{K^2}P} \right] - 3.037E - 5\left[ {{E^2}K} \right] \). The average error was 1.23 % in the validated experiment.

泡沫稳定性严重影响了纯生啤酒的质量。本文考察了蛋白酶A活性与泡沫稳定性的关系,结果显示二者呈明显负相关的关系。同时考察了影响蛋白酶A分泌的因素,结果发现,蛋白酶A分泌量高的菌株、处于稳定期之后的酵母、较高的酵母代数、较高的原麦汁浓度、发酵阶段末期、较低的酵母活力和较高的酵母死亡率都会导致发酵液中蛋白酶A活性偏高。因此在实际生产中,采用蛋白酶A分泌量少的菌种、调整酵母生理状态、使用小于3代的酵母、采用18°P以下麦汁发酵、尽早结束发酵、提高酵母活力、降低酵母死亡率都会对减少蛋白酶A的分泌量起到积极作用。

A method for the determination of acetaldehyde in beer was established by using the automatic headspace gas chromatography in this paper.Optimization of detection conditions were as below: headspace injector equilibrium temperature 70℃,equilibrium time 30 min;column initial temperature 40℃,temperature-programmed from 10℃/min to 180 ℃;column flow 1.2 mL/min,addition of sodium chloride 1.8 g.The calibration curve showed good linearity in the concentration range of 2~64 mg/L(R2=0.999);good precision was obtained with six easurements.for 10 mg/L standard acetaldehyde solution,RSD,the recoveries and detection limit were 2.5%,96%~108% and 0.4 mg/L,respectively.

The current status of the research on γ-glutamyltranspeptidase(γ-GT) in Saccharomyces cerevisiae is presented in this paper,especially the structure and catalytic mechanisms of γ-GT.γ-GT highly affects the amount of intracellular glutathione in Saccharomyces cerevisiae cells,and plays an important role for the detoxication,resistance to environment stress,and amino acid transportation in S.cerevisiae.Now γ-GT also contains important significance in clinical medicine and the fields of agriculture and industry.

The aim of this study was in order to follow the sour-taste substance change in wheat malt during different malting phase,and to provide technology reference.The amber acid、acetic acid、citric acid、malic acid and lactic acid were chosen as the representative substance in this research,and the malting process was carried through micro-malting operation.The content of sour-taste substance was determined by High Performance Liquid Chromatogram.The results showed that:During the whole germination process,the total sour-taste substance content increased gradually;the malic acid content had been in a dynamic equilibrium throughout the malting process; the contents of acetic,lactic,citric acid and succinic acid in wheat malt by micromalting,increased by 11.2,6.1,7.0 and 4.7 times,respectively.

A copy of copper response gene (cup1) and a copy of β-glucan synthetase gene(fks1) were extended by PCR reaction from the industrial brewing yeast strain G-03. Recombinant plasmid pKC was constructed by linking cup1 to pTK, which was made up of fks1 and pMD-18T Vector, by restrict enzyme BglⅡ、SalⅠ. The fragment fks1::cup1 obtained through the restrictive enzyme reaction was integrated to the chromosomal DNA of G-03 strain, and recombinants were screened by copper resistance. To test the genetic stability, strain G-03/C was incubated into flasks and transferred continuously 10 times. It could grow on copper resistant medium. When the main fermentation was over, there was no differences in the concentration of C_(8:0) and C_(10:0) between G-03 and G-03/C. Under 25 degree forced autolytic conditions, the content of fatty acids including C_(8:0), C_(10:0), reduced by 57.3%, 81.8% respectively, compared with that of the host strain G-03. Therefore the autolytic ability weakened, while mortality, concentration of diacetyl, turbidity and TBA of G-03/C reduced to a certain extent. Sensory evaluation test of beer demonstrated that the beer flavor of G-03/C was better.

In vitro evolution methods are often used to modify protein with improved characteristics. We developed a directed evolution protocol to enhance the thermostability of the beta-1,3-1,4-glucanase. The thermostability of the enzyme was significantly improved after two rounds of directed evolution. Three variants with higher thermostability were obtained. The mutant enzymes were further analyzed by their melting temperature, halftime and kinetic parameters. Comparing to intact enzyme, the T50 of mutant enzymes 2-JF-01, 2-JF-02 and 2-JF-03 were increased by 2.2 degrees C, 5.5 degrees C and 3.5 degrees C, respectively, the halftime (t1/2, 60 degrees C) of mutant enzymes 2-JF-01, 2-JF-02 and 2-JF-03 were shortened by 4,13 and 17 min, respectively, the V(max) of mutant enzymes were decreased by 8.3%, 2.6% and 10.6%, respectively, while K(m) of mutant enzymes were nearly unchanged. Sequence analysis revealed seven single amino acid mutant happened among three mutant enzymes, such as 2-JF-01 (N36S, G213R), 2-JF-02 (C86R, S115I, N150G) and 2-JF-03 (E156V, K105R). Homology-modeling showed that five of seven substituted amino acids were located on the surface of or in hole of protein. 42.8% of substituted amino acids were arginine, which indicated that arginine may play a role in the improvement of the thermostability of the beta-1,3-1,4-glucanase.This study provide some intresting results of the structural basis of the thermostability of beta-1,3-1,4-glucanase,and provide some new point of view in modifying enzyme for future industrial use.

Glutathione(GSH) is one of the major non-protein thiol compounds.GSH(the reducing form of glutathione) is widely distributed in nature and plays many important physiological roles in living cells.The free radical-scavenging activity of GSH enables to reduce the content of pre-staling compounds and flavor staling compounds.In the early stage,the content of staling compounds was reduced by the free radical-scavenging activity of GSH.Then the beer flavor stability was improved by the reduction of off-flavor and staling compounds. This review gave an overview of the research progress of glutathione in Saccharomyces cerevisiae,as well as application of genetic modification in improving the Saccharomyces cerevisiae GSH.

[Objective]The study aimed to observe the effect of inorganic positive ions(Ca2+,Mg2+,K+,Na+)and negative ions(Cl-,SO2-4)on beer taste,and make a preliminary study on its mechanism.[Method]Chemical shifts of different ion concentration liquor were analyzed through nuclear magnetic resonance(NMR)method.Moreover,the whole harmony characteristic of beer samples was evaluated by sensory evaluation,and after that,the comparison of sensory evaluation results and NMR results was carried out to show the feasibility of studying beer taste difference by proton chemical shifts.[Results]Inorganic ions can destroy or strengthen the hydrogen bonding.Moreover,the change of chemical shift was higher for the beer sample with better taste,vice versa.[Conclusion]The proton chemical shift was consistent with sensory evaluation very well.It's very feasible to explain the mechanism of inorganic ions affecting on beer taste through the angle of hydrogen bonding of the beer body.

The effect of major flavor compounds in wine on hydrogen bonds of water-ethanol system was studied.PlackettBurman experiments confirmed that hydrogen bonds of water-ethanol system were greatly affected by isobutanol,β-phenylethyl alcohol,ethyl acetate,KCl,NaCl,MgSO4,malic acid,lactic acid and pyruvic acid.Correlation analysis indicated that coefficient between alcohol concentration and hydrogen bond intensity was 0.629.Therefore,alcohol concentration was the primary factor to hydrogen bond intensity although original wort concentration,isobutanol,Cl-,K+,pyruvic acid and lactic acid also exhibited an influence on hydrogen bond intensity to some extent.

13 kinds of the main flavor compounds of thirty different brands of beer were detected and it was analyzed by principle components analysis.The same samples were tasted by some experienced staff and it was adopted by frequent analysis.There was a close relationship between the two analysis results.It was indicated that the beer flavor could be judged and controlled according to the results of the 13 kinds of flavor compounds..

The effect of yeast types and wheat malt varieties on the composition of organic acids in wheat beer was observed.According to the composition of organic acids of German high-grade wheat beer, the relative optimal range of organic acids was determined, and through the L_9 (3~3) orthogonal experiment, respectively. Finally, the best fermentation parameters were obtained as follows: wort pH 5.5; inoculation of 1.0 × 10~7/mL; the main fermentation temperature 10℃.The results showed that the acetic acid and succinic acid content could be effectively reduced,and citric acid content could increase at the same time with yeast strains owing reasonable organic composition,excellent wheat malts and the better fermentation parameters.Therefore, the composition of organic acids,acid sense and flavor of final wheat beer would be improved.

Response surface methodlogy (RSM)was used to optimize the fermentation medium for β-glucanase production by E.coli BL21(DE3)-pET28a(+)-bgl.Firstly,Plackett-Burman design was used to evaluate the influence of six related factors.It was showed that there were three factors which was important for β-glucanase activity,including glycerin,yeast extract powder and NaCl.The optimal concentrations of them was 18.9,45.6 and 5.3g/L respectively after Box-Behnken design,and response surface analysis were used.The β-glucanase activity was reached 2311.84U/mL,which was increased by 23%.

The bitter substances will degrade in beer during storage,and the change of bitter substances in beer during storage was studied by determining cis/trans stereoisomers of iso-α-acid using HPLC. As a result,the trans form of iso-α-acid decreased faster,while the cis form decreased scarcely. The same brand with forced aging and natural aging except of the different brands of beers with forced aging were reviewed. The T/C ratio showed an evident linear relativity with staling time and stale flavor intensity,so it can reflect the extent of beer staling excluding the difference of manufacturing dates even brands,and it would become a new index to estimate beer staling better.

Cell protein was hydrolyzed if brewing yeast autolyzed,and the compositions of hydrolysate such as α-amino nitrogen,amino acids and total nitrogen were different with the different type of yeast,but the rate of non-α-amino nitrogen to α-amino nitrogen in the autolysates was from 2.24 to 7.91. Ideally the rate was 7.91 which shew non-autolysis of yeast. The less was the rate,the more was autolysis of yeast. When yeast autolyzed completely,the rate was near to 2.24.

To compare of performance of beta-1,3-1,4-glucanase gene (bgl) in different expression systems, the beta-1,3-1,4-glucanase gene (GenBank Accession No. EU623974) was amplified from Bacillus amyloliquefaciens BS5582 by PCR and was cloned into three vectors pEGX-4T-1, pET20b(+) and pET28a(+) to construct pEGX-4T-1-bgl, pET20b(+)-bgl and pET28a(+)-bgl recombinant plasmids. The pEGX-4T-1-bgl was transformed into three different Escherichia coli host strains. The pET20b (+)-bgl and pET28a (+)-bgl were transformed into E. coli BL21 (DE3) respectively. Recombinant beta-glucanase was expressed by IPTG inducement in these recombinants. E. coli BL21 (DE3)-pET28a (+)-bgl had the highest enzyme activity. In Luria-Bertani medium, the total enzyme activity was (322.0 +/- 8.8) U/mL, which was 40.1% of original strain in optimal shaking flask condition. This recombinant's performance was studied in Terrific Broth medium under inducement of IPTG and lactose at the same time., and the highest total enzyme activity could reach (1883.3 +/- 45.8) U/mL (818.8% of the original), which indicate that the recombinant strain has a good value in industry application.