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Influence of beer protein on foam stability
Benda, David ; Štursa, Václav (referee) ; Pořízka, Jaromír (advisor)
This bachelor thesis deals with the influence of beer proteins, phenolic compounds, bitterness and selected metal ions on beer foam stability. The theoretical part describes beer foam from the physical aspect, beer foam stability and its measurement and the factors that positively or negatively influences the stability and quality of the beer foam. In the theoretical part are described selected proteins that influence beer foam. In theoretical part is described the origin and technological significance of proteins. The experimental part is dedicated to the measurement of beer foam stability with the NIBEM method, the analysis of total protein content, the analysis of total phenolic content, bitternes and element analysis of beer samples. Measured data indicated correlations between protein content, phenolic compounds content, bitterness and metal ions with the beer foam stability. The results show that proteins and phenolic compounds as isolated parameters don’t essentialy affect the beer foam stability. It was found out, that bitterness as isolated parameter influences the beer foam stability the most.
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Isolation and characterization of beta-glucans of natural origin
Ratsilouskaya, Lizaveta ; Hoová, Julie (referee) ; Márová, Ivana (advisor)
The bachelor thesis deals with the characterization of natural beta-glucans and other active substances isolated from macroalgae and yeasts. The used macroalgae samples differ in the pigment, origin and method of algae processing. The theoretical part focuses on seaweed and yeast species, beta-glucans, their sources and biological effects, other biologically active substances (such as polyphenols and antioxidants) and finally on methods for determining these biologically active substances. In the practical part, samples of selected macroalgae were analyzed, namely samples of Arame, Nori, Kombu, Wakame, Hijiki and Spaghetti. Aqueous, ethanol and acetone extracts of these algae were prepared in this work. The aqueous extracts were used for spectrophotometric determination of phenolic substances, flavonoids and antioxidant activity by the ABTS method. Furthermore, ethanol and acetone extracts of said macroalgae were used to determine total chlorophyll and carotenoid content spectrophotometric. The work also focused on beta-glucan content, analyzing macroalgae and yeast R. toruloides. Arame and Nori algae and R. toruloides were high in beta-glucans. However, beta-glucans were very low in other macroalgae.
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Biologically active substances of the Gotu kola plant
Šumberová, Michaela ; Nábělek, Jakub (referee) ; Zemanová, Jana (advisor)
The Bachelor thesis focuses on the preparation and characterization of the extract of Gotu kola (Centella asiatica). The theoretical part summarizes commonly analyzed groups of biologically active compounds of herbs and introduces potential applications of the extract in food industry. Moreover, an overview of possibly used extraction methods and analytical methods for the evaluation of biologically active compounds of the extract are presented. As for the experiment, the extract of the fresh Centella asiatica herb was prepared by maceration in ethanol and then analyzed by three chosen methods. The total phenolic content of the extract analyzed by the Folin-Ciocalteu test was 0.74 ± 0.08 mgGAE·g-1. As for the quantification of antioxidant activity, the TEAC test was performed and the antioxidant activity of the extract was 289 ± 81 µg·ml-1. The volatiles present in the extract were identified by gas-chromatography mass-spectrometry in combination with solid-phase micro-extraction. Sesquiterpenoid hydrocarbons were the most dominant group of the extract, in which -farnesene (33.28 %), -caryophyllene (25.01 %), and -humulene (20.91 %) were the major compounds.
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Stability and properties of combined beverages and fruit concentrates
Klatová, Kamila ; Vítová, Eva (referee) ; Vespalcová, Milena (advisor)
This diploma thesis deals with the stability and basic properties of combined beverages and fruit concentrates. The theoretical part describes the production and use of fruit concentrates. Furthermore, the work deals with anthocyanic pigments and phenolic substances. The principle and instrumentation of liquid chromatography and electron paramagnetic resonance were described. In the next subchapter, the methods of determination of total anthocyanins and phenolic substances were described. The experimental part of the thesis described the determination of soluble solids, viscosity and antioxidant activity. The total content of phenolic compounds were determined by the Folin-Ciocalteua method and the total anthocyanins were determined by the pH-differential method. In the samples were determined cyanidine-3-glucoside and cyanidin-3-galactoside by liquid chromatography.
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Selected nutritional parameters of some lesser known fruit
Diblíková, Michaela ; Hrstka, Miroslav (referee) ; Vespalcová, Milena (advisor)
Diploma thesis is focused on the chemical analysis of the juices of black, red and white currant and jostaberry (Ribes a Ribes x culverwellii). The theoretical part is focused to the definition of fruit, fruit importance in human nutrition, description of Ribes and Ribes x culverwellii genuses, active substances in the currants and the jostaberry, description of selected chemical parameters and the determination of some of them. The procedures of determining for the following chemical parameters are described in the experimental section: determination of reducing sugars, determination of total and soluble solids, formol number, pH, titratable acidity, determination of total phenols and anthocyanins and determination of vitamin C in two samples jostaberry, six varieties of black currants, one variety of white currant and two varieties of red currants. Based on the evaluation of the obtained results, the comparison was made with different varieties and the thesis that "overall comparison of the different varieties in the content of phenolic compounds, vitamin C and anthocyanins appears to be the most promising variety of blackcurrant demon. It should however be noted that the highest content of phenolics and anthocyanins were determined in jostaberry„ has been suggested.
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Use of secondary raw materials from wine production
Lajtman, Roman ; Vespalcová, Milena (referee) ; Diviš, Pavel (advisor)
This bachelor thesis deals with using of grape pomace, waste from wine industry. It also deals with the determining of total phenolic substances in a grape pomace. The theoretical part focuses on the characteristic of grape, the chemical composition of wine, making of wine and mainly on use of secondary raw materials. It also describes phenolic substances, their division and finally something general about using experimental methods. In the experimental part a red grape pomace´s extraction was made. The extractions were made in different solvents, in a mixture ethanol-water (ratio 20:80; 40:60 and 60:40), also in a mixture glycerol-water (ratio 10:90; 20:80 and 40:60) and at the end in water. The extractions were made in a different time and the purpose was to optimize the extractions and to get the highest yield of phenolic substances, antioxidants. Time and economically side played an important role to find out and to choose the best solvent. In the results, as the best and the optimal extraction´s solvent on extraction of red grape pomace was chosen the mixture ethanol-water and ratio was 60:40. That mixture extracted the most phenolic substances and relatively in the shortest time. During the optimization of sample weight was found out that optimal sample weight is 4 g of grape pomace. At the end repeated extraction was made. It is obviously practically worthless. After second step of extraction, the concentration of phenolic substances is more than a half lower than at the first step.
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Extraction of bioactive substances from the pomace of red grapes
Jandrtová, Sabina ; Pořízka, Jaromír (referee) ; Vespalcová, Milena (advisor)
This bachelor thesis deals with the research of chosen chemical characteristics in juice and in extracts of grapevine (Vitis vinifera L.). The theoretical part is divided into three parts. In the first part is described the botanical characteristic of grapevine, then its origin, morphology, chemical composition, species and uses. In the second part are characterized anthocyanin pigments, their occurrence and attributes. There are described methods of the investigation. In the third part are described extractions. The experimental part illustrates extractions of the pomace. The purpose of these extractions is to find out the total amount of anthocyanins and phenolics in the pomace, and which solvent gives the highest yield. Then the chemical characteristics, such as total and soluble solids, pH, the amount of titratable acids, reducing carbohydrates, phenolics and anthocyanins, are described in this section. All determinations are executed and results are compared among grapevine juice and two species (Cabernet Sauvignon and Zweigeltrebe). The most suitable solvent is selected a mixture of water and ethanol in a ratio 50:50. In the most effective hours are determined the chemical characteristics. The titratable acids are expressed as the amount of the tartaric acid. The amount of phenolics is expressed as gallic acid and the amount of anthocyanins as malvidin-3-glucoside.
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Study of geographical authenticity of Moravian white wines
Horáková, Kristýna ; Křikala, Jakub (referee) ; Diviš, Pavel (advisor)
The aim of this bachelor thesis was to verify geographical autenticity of Moravian white wines based on elemental analysis. This data were completed with the analysis of organic acids, fenolic compounds and atioxidants in wines. There were used two spektrometric methods for the elemental analysis (ICP-MS and ICP-OES). The concentration of organic acids was mesured by Ion chromatography. To determine the concentration of phenolic compounds in wines there was used the high performance liquid chromatography (HPLC-DAD), the content of antioxidants and the total content of phenols was measured on spectrophotometer. In total there were 33 samples of wine from 4 Moravian subregions. For the purpose of determination the samples in groups the dataset was firstly corrected by Grubbs test for remote results. From those data the box plots were created which represents the minimal, maximal and mean concentrations of each measured component. Furthermore the analysis of variance was applied, which picked up 12 statisticly valuable parameters from the whole 47. By appliyng the multidimensional statistical methods (Pearson correlation analysis (PCA) and discriminant analysis (DA)) were compiled mathematical models for the division of Moravian wines according to geographical origin. The success rate of the discrimination test was 96,97%. The cross-validation test showed an 81,82% success rate for classifying unknown samples.
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Extraction of bioactive substances from black currant pomace
Sedláčková, Lucie ; Štursa, Václav (referee) ; Vespalcová, Milena (advisor)
This bachelor thesis deals with extraction of bioactive substances from black currant pomace (Ribes nigrum). The theoretical part contains the botanical characteristics of the plant species Ribes nigrum. It is also devoted to the biologically active substances contained in black currant and possibilities of using black currant in the food industry. The fourth chapter deals with description of phenolic compounds, their distribution and methods of determination of phenolic substances. The fifth chapter describes selected extraction procedures. In the experimental part, there were extracted dry black currant pomace in order to optimize the extraction process and obtain the highest yields of dyes. In addition, were determined the selected chemical and physical characteristics of blackcurrant juice and extracts from blackcurrant pomace. A better solvent was a mixture of water and ethanol in a volume ratio of 1:1. After 14 hours maceration of dry pomace, were obtained 769,9 mg anthocyanins per 100 g of dry material.
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Effect of the dry hopping of the stability of beer foam
Benda, David ; Štursa, Václav (referee) ; Pořízka, Jaromír (advisor)
This diploma thesis deals with the influence of dry hopping on the stability of the beer foam. It was observed how this effect affected general characteristics of beer, the content of hop bitter acids, proteins, phenolic compounds, selected micro- and macro elements, organic acids and the stability od the beer foam. Theoretical part characterises raw the materials for beer production, the substances affecting the stability of beer foam and the beer brewing process. Furthermore the beer foam is described froam a physical point of view together with the steps of its formation and drainage as well as other phenomena that lead to its disappearance. A detailed description of used analytical methods is included. The experimental part illustrates the preparation of the model beer and the implementation of dry hopping with the Czech hop variety called Kazbek. Dry hopping was carried out on day 3, day 5 and day 10 with a 3 g/l and a 6 g/l hop dose. The prepared beer was subsequently analysed for general characteristics, the beer foam stability, bitter hop acids, phenolic compounds, protein, selected micro- and macroelements and organic acids. Based on the measured data, there were found correlations between the observed beer parameter and the stablity of the beer foam. The results revealed that dry hopping in beer increases the content of the phenolic compounds and bitter substances, but its effect on the beer foam stability is negative.
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