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Determination of volatile substances in wines of Hibernal variety
Burian, Martin ; Rychetský, Matěj (referee) ; Vítová, Eva (advisor)
The subject of the present bachelor thesis was the determination of aromatic substances in wines of the Hibernal variety and subsequent comparison of the aromatic profile of individual samples in order to investigate the possibilities of geographical authentication of these varietal wines on the basis of its volatile compounds content. In total, 19 samples from four Moravian sub-regions were analysed. The analysis of the aromatic profile was carried out using the HS-SPME-GC-MS technique. All samples were then subjected to descriptive statistical analysis. The results show that from the profile of 25 selected volatile compounds, the samples cannot be distinguished according to their place of origin.
Effect of dry matter content on the profile of volatile substances of selected fermented milk products
Kirchdorfer, Jakub ; Gross, Michal (referee) ; Vítová, Eva (advisor)
This bachelor thesis deals with the production of yogurt and its characterization in terms of sensory quality and volatile (flavour) profile. The theoretical part deals with the characterization of yogurt, production technology, sensory quality, and possibilities of determination of volatile compounds in yogurt samples. In the experimental part, the production process of the samples was first optimized to achieve the best possible sensory quality. To achieve the desired thick consistency of the yogurt, the dry matter content was increased by the addition of non-fat milk powder and whey powder. For the sensory evaluation, graphical scales were used to assess appearance, colour, consistency, aroma, and taste, as well as a ranking test and a paired comparison test. The results showed that in the case of milk powder, as expected, the higher addition resulted in the desired thicker consistency, while the higher addition also softened the flavour and aroma of the yogurt. In the case of whey powder, on the other hand, the density of the yogurt decreased with higher additions and the taste and flavour were not significantly affected. Yogurts with 6 % w/w milk powder and 2 % w/w whey powder were selected as “optimal”. Both had an optimum consistency, a pleasant colour and aroma and a slightly sour taste. The volatile matter profile was determined by HS-SPME-GC-MS; a total of 16 compounds were identified in the samples, with ketones and acids predominating. The most abundant compounds were diacetyl, acetoin, acetic acid and caproic acid. The results show that the addition of dry matter did not significantly influence the overall profile of volatiles in the samples, no clear trend can be identified. The effect on the sensory quality of the samples was more evident, but even here the results are not conclusive. While some evaluators preferred the thick consistency of yogurt with the addition of milk powder, some preferred the better taste of yogurt with the addition of whey powder.
Pepper quality in terms of piperine content
Lamplot, Marek ; Vítová, Eva (referee) ; Diviš, Pavel (advisor)
The aim of this bachelor's thesis was to determine the quality of pepper available in the commercial network of the Czech Republic. The quality of the pepper samples was determined based on the piperine content. Piperine was extracted from pepper samples using acetone and the extracts were subsequently analyzed using high-performance liquid chromatography with a mass detector. In all samples, the water content was determined by Karl-Fisher titration, and the piperine content in the samples was subsequently converted to dry matter. The content of piperine in pepper varied from 49 to 90 mg/g and met the requirements of the current legislation, which specifies a minimum piperine content of 4 % in pepper. Statistical analysis showed that there is a statistically significant difference between individual pepper samples in terms of piperine content, which points to the fact that pepper from different producers comes from different sources.
Effect of added carbohydrates on the quality of cereal kvass and kvass bread
Stoklásková, Olga ; Vítová, Eva (referee) ; Diviš, Pavel (advisor)
The aim of this bachelor thesis was to characterize selected chemical, senzoric and rheologic properties of sourdough breads with added particular saccharides in the dough. In the theoretical part, processes during mixing, proofing and scaling of the sourdough in fixed conditions are analysed; researched sugars are characterized and their influence on the sourdough product, resulting from present research, is discussed. The experimental part focuses on particular analyses, that influence the quality of sourdough product and determine so its market demand. According to the analysis, sourdough fortification of low honey concentration tends to the maximal volume of the loaf and the most tender crumb at the same time. Higher additions of white table sugar increase the total acidity of the dough the most significantly; unlike, a malt flour provides a smooth, sweetish aroma to the bread. This is because of inhibition of acetic acid production by maltose during sourdough fermentation. Unfortunately, lower concentration of acetate and higher content of remaining sugars in the same time is a factor of shortening the microbial shelf-life of the bread after its baking.
The effect of the dehydration method on the profile of volatile substances of selected fruits
Prystupa, Anna ; Trenzová, Kristina (referee) ; Vítová, Eva (advisor)
This bachelor's thesis focuses on the identification and quantification of volatile compounds in samples of selected tropical fruits, namely banana, kiwi, mango, pineapple, and pitahaya. The theoretical part provides a detailed description of the lyophilization method as a food preservation technique, its principles, and its applications in the food industry. The principles of conventional drying methods are also explained, along with a brief introduction to various types of drying equipment. Additionally, the characteristics of each tropical fruit species, including their chemical and aromatic composition, are presented. Lastly, the principle and instrumentation of solid-phase microextraction and gas chromatography-mass spectrometry are explained. The experimental part of the thesis focuses on the identification and quantification of volatile compounds in samples of fresh, lyophilized, and dried fruit. The results indicate that the chosen methods of preservation have varying effects on the profile of volatile compounds in different tropical fruit species. Losses of compounds or the formation of new compounds may occur, which lays the foundation for further research in this area.
Microbial diversity of breast milk and its influence on the gut microbiome of infants
Novotná, Jana ; Vítová, Eva (referee) ; Trachtová, Štěpánka (advisor)
Breast milk is considered the most important source of nutrition for infants and newborns due to its content of all the necessary nutrients and bioactive components that positively affect the child's immune system. The theoretical part of my work deals with the microbial composition of breast milk and its transformation depending on the stages of breastfeeding and other factors. The experimental part is focused on the identification of selected bacterial strains in breast milk and stool of a breastfed child and a child fed an artificial milk diet. Collection strains of bacteria belonging to the genera Bifidobacterium, Lactobacillus, and Candida were used for the analysis. DNA was isolated by phenol extraction, using magnetic carriers and a commercial kit. The presence of bacterial DNA was proved by q-PCR analysis using genus-specific primers for selected bacteria.
Study of the chemical profile of wine of Riesling variety
Šumberová, Michaela ; Trachtová, Štěpánka (referee) ; Vítová, Eva (advisor)
This diploma thesis focuses on the chemical profile and authentication of the geographical origin of varietal wine Rhine Riesling obtained from 4 Moravian wine regions. In the experiment, 20 wine samples were analysed with 5 instrumental analytical methods – aromatic compounds were determined by HS-SPME-GC-MS, phenolic compounds by HPLC-MS, total phenolic content by MAS, and elemental analysis by ICP-OES and ICP-MS. In total 36 aromatic compounds were detected, from which 7 were varietal terpenes and 2 of them C13 norisoprenoids. The total phenolic content for the Rhine Riesling wine was measured in the concentration range of 174,22–380,96 mg·l-1. Gallic acid (0,41–34,99 mg·l-1), catechin (0,05–7,44 mg·l-1), epicatechin (0,03–4,14 mg·l-1), caffeic acid (0,14–2,05 mg·l-1), and coumaric acid (0,30–4,04 mg·l-1) were the specific measured phenolics. In total 18 elements were measured in Rhine Riesling wine, macroelements K > P > Mg > Ca > Na with concentrations above 10 mg·l-1, microelements Al > Fe > Zn > Mn > Sr > Cu in the concentration range 0,1–10 mg·l-1, and trace elements Ni > Cr > V > Pb > Mo > Co > Cd in the concentration 0,0001–1 mg·l-1. Potassium was the most abundant element (386,37 mg·l-1). The results were used for the parametric and nonparametric univariate analysis of variance (ANOVA) and multivariate principal component analysis (PCA). Ni60 (p = 0,0029), ethyl benzoate (p = 0,0060), and diethyl succinate (p = 0,0247) were statistically the most significant parameters influenced by the wine region for the significance level = 0,05. Out of the 57 measured variables 7 parameters were identified as statistically significant and used for PCA graphic representation of the samples. PCA results show, that the varietal wine’s origin can be authenticated by chosen chemical compounds and chemometric methods.
Optimization of the production of yogurt with increased protein content from wheat bran
Adamczyková, Michaela ; Vítová, Eva (referee) ; Pořízka, Jaromír (advisor)
This thesis deals with the use of wheat bran in the form of protein isolate as an additive in the food industry, optimalization of the formula of fortified yoghurts and the encapsulation of plant proteins, used as a method to mask the negative sensory properties of products with the addition of these proteins. The theoretical part deals with the characterization of fermented milk products, wheat bran as a source of protein and the possibilities of masking the negative sensory properties of protein isolates. The produced yoghurts were sensory evaluated and their nutritional and technological properties were analyzed in the experimental part. By sensory analysis of yoghurts made from different types of milk, full-fat UHT milk was determined to be the best for the production of fortified yoghurts. Yoghurts prepared from this milk were fortified with wheat bran protein isolate. The products thus had an increased nutritional value, but their sensory values deteriorated. The yoghurts had a gritty feel, which was subsequently mitigated by grinding the protein isolate to finer parts. The formula for the production of fortified yoghurts was optimized by the addition of alternative protein, which had a positive effect especially for yoghurts with a 10% protein content. Yoghurts with protein isolate were evaluated with a negative score for the bitter taste parameter. Encapsulation of proteins significantly reduced the intensity of the bitter taste. Synergy of all prepared samples was determined by filtration. Yoghurt from full-fat UHT milk showed a syneresis of 31.76 ml per 100 g of yoghurt. The addition of protein led to a change in the synergy of this yoghurt. From the rheological analysis, it was determined that 10% yoghurt with encapsulated particles had a higher value of dynamic viscosity and yield stress. Sensory analysis data were evaluated using principal component analysis.
Classic vs. traditional bulgarian yogurt - chemical, microbiological and sensory characterization
Jasimová, Zahraa ; Zemanová, Jana (referee) ; Vítová, Eva (advisor)
This diploma thesis deals with the production and characterization of yogurt. In total, three types of yogurt were produced: "classic" white yogurt, Bulgarian yogurt made from commercial culture, and traditional Bulgarian yogurt obtained by inoculation of yogurt brought from Bulgaria. The products were characterized in terms of sensory quality, volatile profile (HS-SPME-GC-MS), and microbial profile (qPCR). The aim was to find out whether and how the mentioned samples differ in terms of the mentioned parameters. In the theoretical part, Bulgarian yogurt and its method of production technology are characterized. Sensory quality, the possibilities of sensory evaluation of yogurts, the determination of the presence of volatile substances, and the method of their determination are also mentioned. In the last chapter of the theoretical part, the microbial profile is characterized, the possibilities of identifying microbial cultures, and finally the nutritional value of yogurts is described. In the experimental part, the production process of Bulgarian yogurt samples was first optimized, and these were subsequently compared with "classic" white yogurt. For sensory evaluation, graphic scales were used to evaluate appearance, color, consistency, aroma, and taste, as well as a profile test (sweet, sour, bitter, yeasty, and possibly other tastes) and an ordinal test. The results show that the Bulgarian yogurts were assessed sensorially worse than the classic yogurt, mainly because of the sour taste. Samples of Bulgarian yogurts also showed a yeasty taste, the presence of yeast was confirmed using the qPCR method. The profile of volatile (aromatic) substances in the samples was determined using the HS-SPME-GC-MS method. A total of 24 volatile substances were identified in all yogurt samples, of which 6 alcohols, 2 esters, 6 acids, 7 carbonyl compounds, 3 and sulfur compounds.
Optimization of fresh cheese production and their characterization
Bittnerová, Eva ; Pořízka, Jaromír (referee) ; Vítová, Eva (advisor)
This thesis deals with the optimization of fresh cheese production and their characterization in terms of free and bound fatty acids, volatile (aromatic) substances and sensory quality. The theoretical part deals with the characterization of fresh cheeses, their production technology and sensory quality. It also includes options for determining volatile substances and fatty acids in fresh cheeses. In the experimental part, produced fresh cheese samples were analyzed during 14-day storage. The fat was extracted from fresh cheeses with a mixture of diethyl ether and petroleum ether, fatty acids were converted to the appropriate methyl esters by acid esterification with boron trifluoride as a catalyst and determined by gas chromatography with a flame ionization detector. Volatile substances were identified based on the comparison of mass spectra with a library of spectra and retention indices (according to Van den Dool and Kratz). The content of the identified substances was expressed semi-quantitatively using the areas of the respective peaks. A total of 20 fatty acids were identified, palmitic, myristic, stearic, capric, caproic and lauric acids predominated as representatives of saturated fatty acids, oleic acid as a representative of monounsaturated fatty acids, and linoleic acid was abundantly represented among polyunsaturated fatty acids. In terms of volatile substances, a total of 37 compounds were identified in the frozen samples and 42 compounds in the fresh samples. Alcohols, acids, aldehydes and ketones were the most represented. The results of the sensory evaluation show that the evaluators liked the stored cheeses better, so the cheeses maintain a good quality of min. for 14 days when stored in the refrigerator.

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