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Aromatisation of wine by different types of wood
Hrošíková, Monika ; Slavíková, Zuzana (referee) ; Pořízka, Jaromír (advisor)
This thesis deals with aromatised red wines using different woods as an alternative method of colouring. It focuses on the phenolic profile of the wine, more specifically on the substances extracted from the wood into the wine, the organic acids and the overall sensory character of the wines aged in contact with the wood. The theoretical part describes the technology of red wine production, its chemical composition, the method of colouring and its alternatives and the associated treatment and modification of the chemical composition of the wood. It also focuses on the phenolic substances extracted and the changes in the sensory profile during the ageing of wine in contact with wood and the possibilities of determining the chemical and sensory profile of these aromatised wines. The experimental part focuses on the chemical and sensory analysis of the changes of a reference Merlot wine during ageing with different types of wood in a two-week and two-month maceration. Changes in the concentrations of total phenolic compounds by Folin-Ciocalteu method, organic acids by ion chromatography, selected phenolic compounds by LCxMS, furfural compounds by GC-FID and colour parameters were monitored.
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Development of cereal products for specifc nutrition with addition of fruits and vegetables
Růžičková, Magdalena ; Kubalová, Michaela (referee) ; Bendová, Agáta (advisor)
This bachelor thesis focuses on developing gluten-free cereal products for special nutrition. The main focus is on increasing the concentration of phenolic compounds and antioxidants in cereals by adding fruit and vegetable components. The theoretical part includes findings from professional literature on cereals, gluten-free cereals and their chemical composition. A chapter devoted to celiac disease and gluten-free diet was also included. Furthermore, the theoretical part focuses on possible methods of enrichment and also on selected fruits and vegetables used in the experimental part. In the experimental part, five samples of gluten-free cereals were analysed, namely black, red, brown and white rice and corn. The concentration of flavonoids, polyphenols, antioxidants, carbohydrates, proteins, -carotenes, anthocyanins, gluten, -glucans, fatty acids and lipophilic vitamins was determined in the cereal samples. Selected samples were also tested for antimicrobial activity. The black rice sample showed the best results in the majority of the measurements. Selected samples of eight types of fruit (cranberry, raspberry, strawberry, blueberry, blackcurrant, mango, banana, kiwi) and four types of vegetables (broccoli, carrot, green pea, beetroot) were also analysed. The concentration of flavonoids, polyphenols, antioxidants, carotenes, anthocyanins, ascorbic acid and lipophilic vitamins was determined in these samples. Antimicrobial tests were performed on selected fruit and vegetable samples Among the fruit samples, the best results in the majority of measurements were in blueberry and blackcurrant samples. Among the vegetable samples, the best results were obtained from the beetroot sample. From the best cereal, fruit and vegetable samples were created porridges as a final product. In these samples, the concentration of polyphenols and antioxidants was determined. The highest concentration of both compounds was found in the porridge with black rice and blueberry.
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Determination of selected bioactive substances in grapes
Havlíková, Markéta ; Trachtová, Štěpánka (referee) ; Vítová, Eva (advisor)
The subject of this thesis was the determination of selected bioactive substances in grapes and the subsequent comparison of differences between the samples. Two fractions of grapes (skins and pulp with seeds) of 4 grape varieties - Hibernal, Johanniter, Riesling and Aurelius - were analysed. Two methods were used for the determination: for phenolic substances, high-performance liquid chromatography with mass spectrometry and for volatile substances, headspace solid-phase microextraction coupled with gas chromatography and mass spectrometry. For each of these methods, the optimal extraction technique was first selected and then used for the analysis of all samples. The linearity of the external standard method was also verified with a reliability coefficient R2 in the range of 0.9650-0.9989 for high-performance liquid chromatography with mass spectrometry and 0.8571-0.9999 for headspace solid-phase microextraction coupled with gas chromatography and mass spectrometry. 63 volatile and 9 phenolic compounds were identified in the samples. From these, specific compounds of grapes (20 volatile compounds and 5 phenolic compounds) were selected. On the basis of the amount of observed compounds, the two grape fractions and subsequently the grape varieties were compared with each other. There were differences in the content of selected compounds between grape fractions and across varieties, which could probably be due to the geographical origin of the samples.
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Bioactive compounds in cruciferous vegetables
KOVAČIKOVÁ, Karolína
This diploma thesis deals with bioactive compounds in cruciferous vegetables (Brassicaceae). The thesis aimed to determine the content of phenolic compounds, chlorophyll A, chlorophyll A+B, carotenoids and also vitamin C, in selected species of cruciferous vegetables: Brussel sprouts (Brassica oleracea var. gemmifera), Fodder Kale (Brassica oleracea var. acephala), Curly Kale (Brassica oleracea var. sabellica) and Ornamental Cabbage (Brassica oleracea var. capitata). The highest amount of chlorophyll A was represented in the sample of ornamental red cabbage, variety Pigeon Victoria F1. The highest content of chlorophyll B, chlorophyll A+B, carotenoids and also vitamin C was determined in curly green kale, a variety Tuscan. The highest amount of phenolic compounds was measured in curly red kale, variety Scarlet.
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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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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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Cereals - Active Substances, Biological Effects and Selected Applications in Food Industry
Lichnová, Andrea ; Tremlová, Bohuslava (referee) ; Vávrová, Milada (referee) ; Márová, Ivana (advisor)
The presented doctoral thesis is focused on the study of the biological effects of active compounds found in cereals, on the development of methods of analysis these effects, on the determination of the content of active substances and characterization of the relationship between composition and biological effects of cereals and cereal products. For the analysis several kinds of raw cereal samples (flakes, flour, germ, bran), flavored extruded cereal products and also samples of paddy and husked rice were chosen. To major types of analysed active compounds belong mainly phenolic compounds in the form of glycosides and aglycones, and also saccharides. Group parameters such as total polyphenols, flavonoids and total and reducing saccharides were determined spectrophotometrically, individual phenolics and saccharides were determined by high performance liquid chromatography (HPLC). TEAC, DPPH and CLAMS methods were used to determine the antioxidant activity. Indirect methods of determination of substances with antioxidant effect were used as well. Results of the total antioxidant activity were compared with values of antimutagenic/genotoxic activity obtained by several microbial test systems. Antimutagenic effect was expressed as a percentage of inhibition of effect of standard mutagen and could be considered as a potential preventive effect of cereals to DNA arising primarily by free radicals effect. The highest values of group and individual phenolics, antioxidant and antimutagenic activity were found in germs, bran, in buckwheat products and in coloured and raw rice. In flavoured cereal products addition of chocolate or fruit positively influences content of active phenolic substances as well as sugars, antixidant and antimutagenic activity. In a representative sample of Czech population, questionnairy study was performed to monitor interest in cereals and consumer preferences. The most of consumers consider cereals with chocolate flavour as less healthy than confirmed results of laboratory analyses. In this study some new food products were developed. Several types of model cereal products containing plant (fruit, vegetables) extracts were proposed. Extracts were added to cereals in freeze-dried and encapsulated form. The highest positive effect exhibited addition of local forrest fruit extract. Within preparation of encapsulated extracts several methods of preparing lipid or saccharides particles were also tested. The encapsulation efficiency of the methods and stability and size of particles were analysed. Optimal type of fortified cereal foods could be suggested based on the acquired results. Selected cereals were used as alternative carbon substrates (processed or raw) for the cultivation of microorganisms to produce enriched biomass usable in the feed industry. We can conclude that cereals in raw as well as processed form belong to universal foods and rich sources of biologically active substances. They can be processed by many ways. They can be used for direct consumption, as a part of new products and also undirectly as a substrate for feedstock.
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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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Analysis of active phenolics in some cereal products
Vondráčková, Hedvika ; Vávrová, Milada (referee) ; Márová, Ivana (advisor)
Presented diploma thesis was focused on study of phenolic substances in various cereal products. Flours, brans and germs from various cereals, flakes and extruded cereals were chosen as samples. Phenolic substances were analyzed by spectrophotometry, RP-HPLC/UV-VIS and RP-HPLC/PDA/ESI-MS. Studies of saccharide content which were analyzed by spectrophotometry and HPLC/RI was incorporated to this thesis. Differences in the content of phenolic substances released from glycosides after acid hydrolysis of samples and differences in saccharide content determined after acid and enzymatic hydrolysis of samples were investigated. Simple sensory analysis of extruded cereal products of different flavour (cocoa, honey, chocolate) was carried out too. In analyzed samples the highest content of total phenolics and total flavonoids was measured in wheat germs. Especially in wheat germs and also in buckwheat and oat flakes, maize brans and cereals products Teddy (cereal balls with cocoa) and Ferda (cereal grains with honey) high levels of individual catechins, phenolic acids and flavonoids were determined too. The quantity of phenolic substances increased for several times in samples processed by acid hydrolysis in comparison to non-hydrolyzed samples. The high content of total saccharides, reduced saccharides and individual mono- and disaccharides was found mainly in extruded products. Concentration of monosaccharides increased in acid hydrolyzed samples in spite of disaccharides concentration that was higher only in some of hydrolyzed samples. In several cases final disaccharide concentrations were lower in hydrolyzed samples than in non-hydrolyzed ones.
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