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Influence of used oil on the composition and sensory quality of cheese analogues
Coufalová, Dominika ; Zemanová, Jana (referee) ; Vítová, Eva (advisor)
This master thesis deals with the production and characterization of cheese analogues with vegetable oil, specifically almond, hazelnut and walnut oils. The products were characterized by volatile compounds, fatty acids, antioxidant activity and sensory quality, and were compared with the standard product. The samples were described as soft white cheese. Volatile compounds were determined by gas chromatography-mass spectrometry. There were 29 compounds identified both in the standard cheese and the analogue with hazelnut oil, 31 compounds in the analogue with almond oil and 34 compounds in the analogue with walnut oil. The highest content of volatile compounds was found in the analogue with hazelnut oil, and the highest number of terpenes in the analogue with walnut oil. Fatty acids were converted into methyl esters after the extraction of fat by using mixture of organic solvents and then they were determined by gas chromatography with flame ionization detection. There were identified 11 saturated, 3 monounsaturated and 2 polyunsaturated fatty acids in all samples. The higher content was found in all cheese analogues compared to standard sample, moreover the content of unsaturated fatty acids increased. The highest content of polyunsaturated fatty acids was found in the analogue with walnut oil. The cheese analogues showed the higher antioxidant activity compared to standard cheese. A significantly higher content was found in the analogue with hazelnut oil. Oil addition decreased the sensory evaluation of consistence and flavour of samples. The standard cheese reached the highest score of overal acceptability among samples; the strongest nut flavour was described in the analogue with hazelnut oil. The results showed that the addition of oils increases the nutritional value of cheeses (higher content of unsaturated fatty acids, higher antioxidant activity), but reduces their sensory quality and overall consumer acceptability.
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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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Study of changes in the chemical composition of coffee during roasting
Kohoutová, Lenka ; Vítová, Eva (referee) ; Diviš, Pavel (advisor)
This bachelor thesis deals with monitoring of changes in acrylamide and hydroxymethylfurfural levels in coffee during the process of roasting. Green coffee was roasted using two separate roasting modes (medium roast: temperature 210 °C for duration of 14 minutes, City roast: temperature 220 °C for 17 minutes). Concentration of acrylamide and hydroxymethylfurfural for various roasting durations was determined by high performance liquid chromatography. For the determination of acrylamide, linear growth of the concentration was observed. The final levels of acrylamide corresponded with levels given by the literature, although the characteristic trend of acrylamide formation was not observed. Typical trend of hydroxymethylfurfural formation was observed in samples roasted with City roast mode, while the first part of the trend was also apparent in samples roasted with medium roast mode. Final levels of hydroxymethylfurfural in roasted coffee were within the limits given by the literature.
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Modern herbs in the food industry
Adamczyková, Michaela ; Řezáčová, Veronika (referee) ; Vítová, Eva (advisor)
The bachelor thesis deals with the issue of volatile (aromatic) compounds of Plectranthus spp. and Echinacea purpurea. The theoretical part focuses on the general characteristics of the above mentioned herbs, the content of their bioactive and volatile compounds, and on their importance as well as on their potential use in the food industry. Using the HS-SPME-GC-MS method, the volatile compounds of the herbs and extracts prepared from them were identified and quantified in the experimental part. A total of 11 volatile compounds were found in all the samples. The most frequent one in the sample of a fresh Plectranthus was 3-carene (13,78%) as well as in the sample of dried Plectranthus (14,85%). However, in the Plectranthus extract it was -selinene (17,84%). As for Echinacea, it is germacrene D (18,64%) in the sample of a fresh one, camphor (58,46%) in the one of dried Echinacea and -copaene (20,42%) in its extract.
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Influence of oil used on composition and sensory quality of cheese analogues
Buldra, Martin ; Mikulíková, Renata (referee) ; Vítová, Eva (advisor)
This paper deals with the manufacture and characterisation of cheese analogues, which are products, where the milk components are totally or partially replaced by non-milk components. Model samples, edam type cheese and the analogue containing hazelnut oil, were manufactured using the standard way at Brno Mendelu. The main parameters chosen to describe the quality of samples were free and bound fatty acids, volatile compounds and sensory quality. The main aim was to judge the influence of added hazelnut oil on mentioned parameters. For the identification and semiquantification of volatile compounds HS-SPME-GC-MS method was used. Fat extraction from sample was made with a mixture of two solvents (diethylether, petrolether), fatty acids were identified and quantified by GC-FID, with their former acid transesterification using methanolic solution of BF3 as a catalyst. For sensory analysis of the appearance, colour, texture, aroma, taste and overall acceptance of the sample descriptive scales and comparison with standard were used, the structure was observed by electron microscopy. The results show that addition of hazelnut oil affects the sensory properties, ripening process (higher amount of volatile compounds, faster lipolysis), nutrition value (higher amount of unsaturated fatty acids), and the stability of the product.
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Assessment of aroma active compounds in elderberries
Kolibačová, Silvie ; Ürgeová,, Eva (referee) ; Vítová, Eva (advisor)
The aim of this diploma thesis was to determine the aroma active compounds in different varieties of black elderberry (Sambucus nigra L.) and in elder juices that were mixed in different proportions with grape juice. The sensory analysis of these juices was subsequently performed with focusing on their tastiness. The theoretical part deals with the description of the black elderberry, its occurrence, composition and use at home and in industrial processing, as well as a description of aroma active compounds, which have been previously identified in elder by various authors. In the experimental part aroma active substances were identified and quantified in seven selected varieties of elder. Solid Phase Microextraction method was used for their isolation and subsequent analysis was performed by gas chromatography. 39 aroma active compounds were identified totally in fruits of the black elderberry, of which 15 alcohols, 11 aldehydes, 7 ketones, 5 esters and 1 acid. 45 aroma active compounds were identified totally in elderberry juices, of which 19 alcohols, 8 aldehydes, 5 ketones, 7 esters and 6 acids. The sensory analysis of elder juices was performed using ranking test and evaluation using the scales.
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Selected inorganic pollutants in foodstuffs
Kroupová, Kateřina ; Vítová, Eva (referee) ; Vitoulová, Eva (advisor)
This bachelor thesis is focus on occurrence of inorganic pollutants in foodstuffs. The introduction is dedicated to apperance of individual selected elements in foodstuffs. Concentration of these elements is very important factor for examination of toxic effects for the human organism. If we want to avoid the harmful effects to the human organism, we have to define border limits. Work is based on the legislative of Czech republic. Second part of this study is focused on the biological monitoring. The biological monitoring is important for precautionary measures. In the third part of this study are described toxical effects of these elements to the human organism. Before qualitative and quantitative analysis by instrumental techniques is important to properly take the sample. In the fourth and fifth part of this work are mentioned methods used for determination of these elements and metods of taking samples. This bachelor thesis provide complex view on the problems of pollutants in foodstuffs and it should be used as a base for following diploma thesis.
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Lyophilized fruits - chemical properties and processing possibilities
Horáková, Klára ; Vítová, Eva (referee) ; Vespalcová, Milena (advisor)
This diploma thesis deals with chemical analysis of selected frozen, dried and lyophilized fruit, specifically Mirabelle de Nancy, Aronia Nero and blackcurrant varieties Gairn Ben and Ben Lomond. In the theoretical part taxonomy and botanical characteristics of selected fruit are given. Subsequently the utilization of fruit in food industry is described. In common the theoretical part focuses on lyophilisation and drying of fruit and raw food. Further in this part the methods of phenolic substances, anthocyanins, antioxidant capacity and finally ascorbic acid and carbohydrates value measurements are specified. In the experimental part the value were determined measurements of biologically active substances: total phenols, total anthocyanins, antioxidant capacity, ascorbic acid and carbohydrates. For all value measurements were compared the frozen, dried and lyophilised samples of every single fruit. Further, the every sort of fruit were compared to each other. Following the raw food preparaon a product of lyophilised fruit was made.
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Effect of roasting on the sensory profile of coffee
Šajdlerová, Kristýna ; Vítová, Eva (referee) ; Diviš, Pavel (advisor)
This bachelor thesis deals with the effect of roasting on the content of carbohydrates and aromatic compounds in coffee. It also studies changes in coffee acidity based on different level of roasting. In the practical part there was measured pH, it was conducted setting of glucose, fructose and sucrose content by liquid chromatography, analysis of aromatic compounds using gas chromatography and also sensoric analysis of 17 types of coffee. Each one was roasted using two different temperatures (210 °C and 240 °C). Based on the statistical processing of basic chemical analysis and sensory analysis, significant differences were found between determined parametres of coffee samples roasted at 210 ° C and 240 ° C. Processing of results of sensory and chemical analysis of coffee samples did not manage to differentiate coffee samples from each other based on their geographic origin. At a lower level of coffee roasting there was found weak, but statistically significant correlation between the results of the sensory analysis and the content of aromatic compounds, while for the higher degree of coffee roasting no correlation was found.
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Aroma profile of processed cheese analogues
Kučerka, Štefan ; Saláková,, Alena (referee) ; Vítová, Eva (advisor)
The aim of this bachelor thesis was to identify and semiquantify volatile (aroma) compounds in samples of processed cheese analogues, produced with full or partial substitution of milk fat with selected vegetable fats/oils (coconut, palm, blended, grapeseed, linseed, apricot kernel, blackcurrant seed). Theoretical part is dealing with characterization of processed cheese analogues, procedure and ingredients used in production. This is followed by a topic of aroma compounds. At the end of theoretical part the method of solid-phase microextraction, gas chromatography and mass spectromectry is described. In the experimental part the model samples of processed cheese analogues were analyzed. They were produced in Tomas Bata University in Zlin. Edam cheese and mentioned fat were used as ingredients. HS-SPME-GS-MS method was chosen to isolate and determinate volatile (aroma) compounds in samples. A total of 152 volatile compounds were identified in samples. Differences in the number and content of the identified compounds were found among samples, aldehydes and acids belonged to the most important groups, sample content speaking.
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