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Characterisation and maturation process of Edam type cheese
Dostálková, Andrea ; Vespalcová, Milena (referee) ; Vítová, Eva (advisor)
This diploma thesis deals with the assessment of aroma compounds and free/bound fatty acids in model samples of Edam type cheeses. Various combinations of microbial cultures, basic mesophilic and four selected strains of thermophilic Lactobacillus casei and Lactobacillus plantarum, were used for cheese production. The main aim was to judge the influence of microbial cultures on content of measured parameters, the changes during ripening were also followed. The HS-SPME-GC-MS method was used for identification and semiquantification of aroma compounds. The lipids from cheese were extracted based on ISO 1735:2004, fatty acids were identified and quantified using GC-FID method after conversion to methyl esters by acid esterification with boron trifluoride in methanol. In total 50 volatile compounds were identified in samples, 11 alcohols, 5 aldehydes, 7 ketones, 6 acids, 10 esters, 3 lactones, 2 sulphur compounds and 6 „others“; all of them are considered as aroma active. About 30–40 compounds were identified in single samples, alcohols, acids and ketones were the predominant. The number as well as the content of compounds identified decreased slightly during ripening. In total 17 free/bound fatty acids were identified in samples, their content also decreased during ripening. Myristic, palmitic, stearic and oleic acids were the predominant. The significant differences (p
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The selection and optimization of the method for assessment of free fatty acids
Koval, Dominik ; Vespalcová, Milena (referee) ; Vítová, Eva (advisor)
This master´s thesis deals with optimization and validation of method for determination of free fatty acids. The theoretical part is focused on possibilities of extraction, extract separation, esterification, gas chromatography determination and brief description of the most important validation parameters. All with main emphasis on applying on free fatty acids. The experimental part describes the selection and procedure of optimizing individual steps of the method. Extraction of lipids was performed by solvent mixture (diethylether/petroleumether), based on the standard ČSN EN ISO 1735, for the extraction of free fatty acid solid phase extraction was tested. The acid catalyzed esterification based on ČSN EN ISO 5509 using methanolic solution BF3 was used for derivatization of free fatty acids and a gas chromatograph with a flame ionization detector was used for their determination. Subsequently, selected validation parameters of the method were verified: repeatability, reproducibility, linearity, limits of detection and quantitation. Sunflower oil and emmental type cheese, bought in common food market, were used as model samples for selection and optimatization of the method.
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The repeatability of the method for assessment of free fatty acids
Buldra, Martin ; Vespalcová, Milena (referee) ; Vítová, Eva (advisor)
This bachelor thesis deals with the assessment of free fatty acids in sunflower oil. Theoretical part focuses on the general characteristics of fatty acids and lipids. The experimental methods suitable for assessment of fatty acids are described, with the emphasis on gas chromatography, the basic method of their assessment. In experimental part two methods for free fatty acids assessment: with/without previous fractionation, were compared and then the repeatability and reproducibility of selected method – the direct esterification of free fatty acids using BF3 as a catalyst, were verified. The assessment of fatty acids methyl esters was done using gas chromatograph with flame-ionization detector.
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Characterization of nut oils
Coufalová, Dominika ; Sýkora, Michal (referee) ; Vítová, Eva (advisor)
This bachelor thesis deals with the characterization of selected nut oils, almond and pistachio virgin oils. The teoretical part concentrates on the description of nut fruits, the characterization of aroma-active compounds, fatty acids and their content in the nut oils. After that, the fatty characteristics, which determines the oil quality, and instrumental methods selected for individual assignment are described. In the experimental part there were 42 volatile compounds identified in the nut oils by the headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry, 35 were found in almond oil and 24 were found in pistachio oil. Free and bound fatty acids were converted into methyl esters using acid-catalysed esterification with boron trifluoride-methanol solution as a catalyst and then they were determined by gas chromatography with flame ionization detection. There were 12 fatty acids identified in almond oil and 14 fatty acids in pistachio oil. Oleic acid and linoleic acid predominated in both samples. The quality and properties of nut oils were valued by determining the fatty characteristics (acid value, saponification value, ester value, iodine value by Hanus method and peroxid value). The increased value of peroxide value was found in both oils which correlates with the trait and storage time of samples.
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The use of solid phase extraction for fractionation of lipids in cheese matrix
Scholzová, Kristýna ; Vespalcová, Milena (referee) ; Vítová, Eva (advisor)
This bachelor thesis deals with Solid Phase Extraction, as a method for isolation of free fatty acids from cheese matrix to be subsequently determined using gas chromatography with FID detection. The theoretical part provides information about milk fat composition and related reactions being a source of flavour compounds, free fatty acids including. The main objective of the theoretical research is to summarize alternatives to determining fatty acids in cheese, focusing on current advancement and use of Solid Phase Extraction for this purpose. The practical part discovers proper technique and conditions for fractionation of lipids by Solid Phase Extraction, using aminopropyl bonded phase columns. Agilent SampliQ Amino columns were utilized to separate lipid mixture and different lipid classes were eluted using suitable organic solvents. Composition and purity of lipid extracts were verified combining thin layer chromatography and gas chromatography. Before being determined by gas chromatography, free fatty acids were converted into methylesters, based on ČSN EN ISO 12966-2. Besides discussing proper experimental conditions, the assesment also comes with solving optimal volumes of sample and eluting solvents to apply. The results of this thesis are considered to be useful base for subsequent experimental optimization and following integration of validated method into process of determining free fatty acids.
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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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