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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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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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The use of thin layer chromatography for fractionation of lipids in cheese matrix
Pop, Zdeněk ; Vespalcová, Milena (referee) ; Vítová, Eva (advisor)
This bachelors thesis is focused on the use of thin layer chromatography for fractionation of lipids in the cheese matrix. Milk fat, lipids, fatty acids, the possibility of determination of lipid compounds, thin-layer chromatography and gas chromatography are characterized in theoretical part. In the experimental part the conditions for the fractionation of lipids using thin layer chromatography were optimized, selected validation parameters were evaluated, lipid fractions obtained from the solid-phase extraction were verified and fatty acids in lipid fractions in the sample of processed cheese were quantified. The method according to ISO 1735 was chosen for extraction of lipids from the samples. Lipids fractionation was performed on commercially available plates for thin-layer chromatography. The method accrording to ISO 5509 using methanol solution of boron trifluoride as catalyst was chosen for the esterification of fatty acids. The resulting methyl esters were determined by gas chromatography with FID detection.
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Production and characterization of cheese analogues with the addition of vegetable oil
Babištová, Lucie ; Zemanová, Jana (referee) ; Vítová, Eva (advisor)
This thesis deals with the production and characterization of cheese analogues, ie products in which some of the dairy components are mutually or completely replaced by a non-dairy component. Model samples of fresh cheese and analogues of fresh cheese (standard) with the addition of linseed and rapeseed oil were produced by a standard technological procedure in MENDELU Brno. The content of bound and free fatty acids, volatile (aroma) substances and sensory quality was monitored in the samples. The main focus was to evaluate the effect of added vegetable oil on the monitored parameters. The fats from the sample were extracted with a mixture of diethyl ether and petroleum ether. Fatty acids were converted to methyl esters by boron trifluoride-catalyzed acid esterification and subsequently identified by GC-FID. The analysis found a higher content of fatty acids in cheese analogues in comparison with the control sample, also the content of unsaturated fatty acids increased. The HS-SPME-GC-MS method was used for the identification and semi-quantification of volatile substances (aromatic substances). 56 volatile compounds were identified in the samples; The percentage of individual chemical groups differed significantly, the highest content was found in the control sample. Sensory evaluation was performed using a scale and a serial test. In all of monitored indicators (apparence, color, consistency, smell and taste) the control sample was evaluated as best. As for the analogues the taste and smell of used oils were detected, which was unpleasant for the evaluators. The obtained results show that the addition of vegetable oils increases the nutritional value of cheeses (higher content of unsaturated fatty acids), but reduces their sensory quality and overall consumer acceptability.
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Sensory quality of French cheese Brie de Meaux in connection with chemical and microbial composition
Májková, Monika ; Němcová, Andrea (referee) ; Vítová, Eva (advisor)
This thesis deals with the assessment of the effect of storage of French Brie de Meaux (AOC) on its volatile (aromatic) compounds, free and bound fatty acids and microbial composition, in relation to its sensory quality. The theoretical part is devoted to cheeses with white mould on the surface. In the experimental part, the influence of temperature and storage time on the sensory quality and safety of cheese is assessed. In the storage experiment, the cheeses were stored for 21 days at 5 °C (one bulk, one vacuumed) and at 20 °C. The samples were evaluated by SPME-GC-MS for volatile (aromatic) compounds. Fatty acids were identified and quantified by GC-FID after conversion to methyl esters using BF3. RT-PCR method was used for microbial profile. Fifty-nine volatile compounds were identified in the samples and contribute to the flavour characteristics of the cheese. Among the fatty acids, palmitic, oleic, myristic and stearic acids were predominant. The microbial profile confirmed Micrococcus luteus as a contaminant in cheese stored at 20°C, while the other contaminants were not detected positively. From a sensory point of view, the standard cheese (analysed immediately after purchase) together with cheese stored at 5 °C in vacuum form for 21 days was the best performing cheese.
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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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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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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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Sensory quality of French cheese Brie de Meaux in connection with chemical and microbial composition
Májková, Monika ; Němcová, Andrea (referee) ; Vítová, Eva (advisor)
This thesis deals with the assessment of the effect of storage of French Brie de Meaux (AOC) on its volatile (aromatic) compounds, free and bound fatty acids and microbial composition, in relation to its sensory quality. The theoretical part is devoted to cheeses with white mould on the surface. In the experimental part, the influence of temperature and storage time on the sensory quality and safety of cheese is assessed. In the storage experiment, the cheeses were stored for 21 days at 5 °C (one bulk, one vacuumed) and at 20 °C. The samples were evaluated by SPME-GC-MS for volatile (aromatic) compounds. Fatty acids were identified and quantified by GC-FID after conversion to methyl esters using BF3. RT-PCR method was used for microbial profile. Fifty-nine volatile compounds were identified in the samples and contribute to the flavour characteristics of the cheese. Among the fatty acids, palmitic, oleic, myristic and stearic acids were predominant. The microbial profile confirmed Micrococcus luteus as a contaminant in cheese stored at 20°C, while the other contaminants were not detected positively. From a sensory point of view, the standard cheese (analysed immediately after purchase) together with cheese stored at 5 °C in vacuum form for 21 days was the best performing cheese.
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