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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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The possibilities of assessment of free fatty acids
Hornáková, Miroslava ; Vespalcová, Milena (referee) ; Vítová, Eva (advisor)
This thesis deals with the determination of free fatty acids in natural and processed cheese. In the theoretical part the possibilities of extraction, fractionation and determination of lipid fractions, characterization of fatty acids and various methods of their determination are described, including the determination of free fatty acids. In the experimental part the selected method for determination of free fatty acids was optimized and partly validated; this method was then applied to samples of processed cheese analogues and natural Gouda type cheese. For extraction of lipids from the sample the method according to ČSN 0107 was selected, solid phase extraction (SPE) was used for separation of free fatty acids. The method according to ČSN EN ISO 5509, using methanol solution of potassium hydroxide, was applied for esterification, fatty acids methyl esters were determined by gas chromatography with FID detection.
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The optimization and validation of the method for assessment of free fatty acids
Sýkora, Michal ; Diviš, Pavel (referee) ; Vítová, Eva (advisor)
This master thesis deals with the development of method for free fatty acids determination in natural and processed cheese. In the theoretical part the possibilities of extraction, fractionation and determination of lipid fractions, characterization of fatty acids and various methods of their determination are described, as well as determination of free fatty acids. The main scope of the experimental section is optimization and validation of the selected method for determination of free fatty acids in various cheese matrices. For extraction of lipids from the sample the method with the mixture of diethylether and petrolether according to ČSN EN ISO 1735 was selected. Thin-layer chromatography and solid phase extraction were tested and compared for separation of free fatty acids. The method according to ČSN EN ISO 5509, using methanol solution of bortrifluoride, was applied for esterification. Fatty acid methyl esters were determined by gas chromatography with flame-ionization detection.
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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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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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Composition of fatty acids in processed cheese analoques
Sůkalová, Kateřina ; Vespalcová, Milena (referee) ; Buňka,, František (advisor)
This thesis deals with the determination of fatty acids of processed cheese analogues. The aim is to identify and quantify the fatty acids in selected samples of cheese analogues. The introduction is a brief overview of the composition and properties of cheese analogues, technology and application options. The following describes the appropriate method for the determination of fatty acids in cheese and cheese analogues. Of these methods the largest part is devoted to gas chromatography, which is most frequently used method for detection of volatile fatty acids. Individual cheese analogues used for the analysis, contained various types of added fats. Specifically, the milk fat, coconut oil, sunflower oil, palm oil and butter. Samples of these fats were extracted and then converted to methylesters by methanol esterification with catalysis by potassium hydroxide. The most important fatty acids were identified and quantified in samples of cheese analogues using gas chromatography and compared with fatty acids of fats used for the preparation of these analogues are used.
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Production of acid- vs. rennet-curd fresh cheese varieties
Veselá, Vendula ; Suská, Alžběta (referee) ; Vítová, Eva (advisor)
This bachelor thesis‘ focus is on the production and characterization of fresh cheese. Model samples of fresh cheese were produced on VUT Brno using purely acidic curdling (cream cheese culture – lactic acid), combined curdling (cream cheese culture + rennet) and acidic combined with heat curdling (acetic acid. 92 C) The samples were observed for their content of bound and free fatty acids, volatile (aromatic) substances and for their sensory quality. The goal was to determine the influence of the method of curdling on the observed factors. The fats were extracted from the samples using a mixture of diethyl ether and petroleum ether solvents. The fatty acids were esterified with acid to methyl esters under boron trifluoride catalysis and identified by the GC-FID method. In the cheese curdled by combined curdling, a greater amount of free fatty acids was detected compared to the other samples. No significant difference in the amount of bound fatty acids was observed. The greatest fatty acid content overall was observed in the cheese produced by acidic curdling. For identification and semi-quantification of the volatile (aromatic) substances, an HS-SPME-GC-MS method was used. 72 volatile compounds were identified in the samples. The percentual representation of different chemical groups varied significantly, the highest number of volatile substances was observed in the cheese produced by acidic curdling. Sensory evaluation was conducted using an evaluation scale as well as a ranking test. In all the observed indicators, the commercial sample was evaluated the best. The cheese produced by combined curdling was received rather negatively due to the sour taste. The second-best cheese was ranked to be the cheese produced by acidic curdling. The results show that the acidic curdling is the best for taste as well as aromatic substance and fatty acid content. If we, however, consider other factors such as the time taken, the cheese produced by combined curdling appears to be the best overall.
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Production and characterization of cheese with the addition of plant extract
Kučerka, Štefan ; Zemanová, Jana (referee) ; Vítová, Eva (advisor)
This master´s thesis deals with production and characterization of fresh cheese with addition of herb extracts, specifically extracts from Plectranthus amboinicus and Echinacea purpurea. The purpose of this thesis was to prepare samples with higher sensory quality and nutritional value. Produced cheeses were characterized in terms of volatile (aroma) substances, fatty acid content, total phenolic substances, antioxidant activity and sensory quality. Cheese sample with added extract from E. purpurea reached the highest value of total phenolic compounds (0,172 ± 0,019 mgGAEg-1 of cheese) and antioxidant activity (91,2 ± 2,2 gTEACg-1 of cheese). Cheese sample with added extract from P. amboinicus, compared to standard cheese sample (without added extract) also reached higher values of total phenolic compounds and antioxidant activity. 43 volatile (aroma) compounds were identified in both samples with added extracts (P. amboinicus, E. purpurea), in standard cheese sample it was 33. In sample with E. purpurea camphor was present in high amount (15,23 %) responsible for the camphor aroma, camphor was also identified in small amount in sample with P. amboinicus. Highest volatile matter content was identified in sample with P. amboinicus. Standard cheese sample was rated as the best from the sensory perspective. Addition of extracts had negative effect on color, taste, and aroma perception of cheese. Strongest herbal taste was identified in sample with E. purpurea, brownish color of this sample manifested in lower pleasantness of color. Obtained results show, that extract addition increases the nutritional value of cheese (higher content of aromatic substances and phenolic compounds, higher antioxidant activity), but lowers sensory quality and overall consumer acceptability.
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Cheese analogue with the addition of fish oil
Damborská, Alexandra ; Juglová, Zuzana (referee) ; Vítová, Eva (advisor)
This barchelor thesis deals with the change in nutritional values of fresh cheese after the addition of fish oil. The subject of research is fatty acids, volatile substances and sensory properties. Fish oil was chosen mainly due to the content of healthy essential omega-3 unsaturated fatty acids eicosapentanoic (EPA) and docosahexanoic (DHA). Samples of fresh cheese (standard) and cheese analogues with various additions of fish oil were prepared on the premises of FCH VUT in Brno. Fat was extracted from the samples with a mixture of petrolether and diethylether solvents. The fatty acids in the fat were converted to methylesters by acid esterification in the presence of borontrifluoride as a catalyst. The methylesters were dissolved in isooctane and determined quantitatively by GC-FID. As the fish oil was added, the fatty acid content of the analogues increased as expected. Identification of volatile (aromatic) substances was performer using the HS-SPME-GC-MS method. A total of 30 volatile (aromatic) compounds were found in cheese/analogues and in fish oil. Cheese analogues with fish oil additions had a common volatile base with the standard and also contained compounds common to fish oil. As a percentage of each group, the cheese analogues resembled the control sample rather than the fish oil. A sensory analysis of a control sample with two analogues with different fish oil additions were performed. The evaluation was recorded in a sensory form with graphic scales and the texture (hardness, disintegration), taste (acidity, bitterness, fishy taste, pleasantness) and smell (intensity, pleasantness) were assessed. At the end, a seriál test was included, which clearly showed that the fish oil in both analogues significantly bothered consumers. The results show that the addition of fish oil increased the content of unsaturated fatty acids including very helthy omega-3 fatty acids (EPA and DHA) in the spectrum of unsaturated fatty acids. However, the results of the sensory analysis show that the increase in nutritional value took place at the expense of the sensory quality of the product. The addition on fish oil did not suit the vast majority.
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