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Study of the aroma profile of selected varieties of Moravian wines
Gross, Michal ; Pořízka, Jaromír (referee) ; Vítová, Eva (advisor)
The subject of this thesis was the determination of the profile of volatile aromatic compounds of varietal wines and the subsequent statistical analysis, aiming to find varietal markers of selected varieties – individual substances, their typical contents, mutual correlations. The HS-SPME-GC-MS technique was used to determine the aromatic profile. The main focus of this work was the analysis of the varieties Pálava, Hibernal, Johanniter and Solaris. The data obtained were statistically processed using descriptive and multivariate statistical methods. On the basis of these analyses, models were developed which, from the contents of 14 selected compounds of the aromatic profile, allow the Piwi varieties Hibernal, Johanniter and Solaris to be distinguished from each other and from the Pálava variety and, for the Pálava variety wines, to determine their origin in the Znojmo or Mikulov wine sub-region.
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Characterization of selected vegetable oils for application in food
Podloučková, Michaela ; Gross, Michal (referee) ; Vítová, Eva (advisor)
This bachelor thesis deals with the characterization of selected types of nut oils made from almonds, walnuts, and hazelnuts. These oils were cold pressed, and they are available on the regular market. The theoretical part deals with the characterization of individual types of nuts and nut oils. The experimental part deals with the comparison of oils in terms of profile and content of volatile substances and fatty acids. The volatile compounds were identified by gas chromatography with mass spectrometry in conjunction with solid phase microextraction. Ten substances, mainly alcohols, were identified in the nut samples. Most substances were found in hazelnut. A total of 44 volatile substances were found in oil samples, mostly in walnut oil. The main substances were aldehydes and alcohols. Fatty acids in free and bound form were converted to methyl esters by acid esterification with methanolic boron trifluoride solution as catalyst. Fatty acids were identified by gas chromatography with flame ionization detection. Unsaturated fatty acids, mainly oleic (almond, hazelnut) and linoleic (walnut) acids, were present in large quantities in the samples.
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Recovery of the method for assessment of fatty acids
Gross, Michal ; Hrstka, Miroslav (referee) ; Vítová, Eva (advisor)
The objective of this bachelor thesis is to verify recovery yield used for determination of fatty acids based on gas chromatography with flame-ionization detection. In the theoretical part, fatty acids and lipids are characterized and extraction of lipidic fraction from food samples with its subsequent adjustments is suggested. Furthermore, the principle and current instrumentation of capillary gas chromatography with flame-ionization detection and standard parameters for validation of the analytical method are specified. In the experimental part, verification of recovery yield of the method for assessment of fatty acids was performed. The used method includes extraction of lipids from a sample in accordance with the standard ISO 1735 regulation and transesterification of both free and bounded fatty acids catalysed by boron trifluoride according to the ISO 12966-2 standard regulation. The produced methyl esters can be effectively determined using gas chromatography with flame-ionization detector. Analysed samples of rapeseed oil and tilsiter-type cheese were purchased in a common food market.
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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.
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Characterization of selected vegetable oils for application in food
Podloučková, Michaela ; Gross, Michal (referee) ; Vítová, Eva (advisor)
This bachelor thesis deals with the characterization of selected types of nut oils made from almonds, walnuts, and hazelnuts. These oils were cold pressed, and they are available on the regular market. The theoretical part deals with the characterization of individual types of nuts and nut oils. The experimental part deals with the comparison of oils in terms of profile and content of volatile substances and fatty acids. The volatile compounds were identified by gas chromatography with mass spectrometry in conjunction with solid phase microextraction. Ten substances, mainly alcohols, were identified in the nut samples. Most substances were found in hazelnut. A total of 44 volatile substances were found in oil samples, mostly in walnut oil. The main substances were aldehydes and alcohols. Fatty acids in free and bound form were converted to methyl esters by acid esterification with methanolic boron trifluoride solution as catalyst. Fatty acids were identified by gas chromatography with flame ionization detection. Unsaturated fatty acids, mainly oleic (almond, hazelnut) and linoleic (walnut) acids, were present in large quantities in the samples.
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Study of the aroma profile of selected varieties of Moravian wines
Gross, Michal ; Pořízka, Jaromír (referee) ; Vítová, Eva (advisor)
The subject of this thesis was the determination of the profile of volatile aromatic compounds of varietal wines and the subsequent statistical analysis, aiming to find varietal markers of selected varieties – individual substances, their typical contents, mutual correlations. The HS-SPME-GC-MS technique was used to determine the aromatic profile. The main focus of this work was the analysis of the varieties Pálava, Hibernal, Johanniter and Solaris. The data obtained were statistically processed using descriptive and multivariate statistical methods. On the basis of these analyses, models were developed which, from the contents of 14 selected compounds of the aromatic profile, allow the Piwi varieties Hibernal, Johanniter and Solaris to be distinguished from each other and from the Pálava variety and, for the Pálava variety wines, to determine their origin in the Znojmo or Mikulov wine sub-region.
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Recovery of the method for assessment of fatty acids
Gross, Michal ; Hrstka, Miroslav (referee) ; Vítová, Eva (advisor)
The objective of this bachelor thesis is to verify recovery yield used for determination of fatty acids based on gas chromatography with flame-ionization detection. In the theoretical part, fatty acids and lipids are characterized and extraction of lipidic fraction from food samples with its subsequent adjustments is suggested. Furthermore, the principle and current instrumentation of capillary gas chromatography with flame-ionization detection and standard parameters for validation of the analytical method are specified. In the experimental part, verification of recovery yield of the method for assessment of fatty acids was performed. The used method includes extraction of lipids from a sample in accordance with the standard ISO 1735 regulation and transesterification of both free and bounded fatty acids catalysed by boron trifluoride according to the ISO 12966-2 standard regulation. The produced methyl esters can be effectively determined using gas chromatography with flame-ionization detector. Analysed samples of rapeseed oil and tilsiter-type cheese were purchased in a common food market.
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