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Characterization of selected yeast strains from food
Ostrihoňová, Katarína ; Vítová, Eva (referee) ; Vránová, Dana (advisor)
This bachelor´s thesis is focused on identification of yeasts of the cheeses by PCR-RFLP method and verifying the lipolytic activity of the yeast. In the theoretical part are processed basic information about yeast, their possible positive and negative effects on the quality of cheeses, the technology of production of cheeses, lipolysis and proteolysis in the cheese and of course of PCR-RFLP (The polymerase chain reaction-restriction fragment length polymorphism). Experimental section shows the isolation of DNA, identification of DNA by PCR made by amplification 5,8S-ITS sections of DNA using primers ITS1 and ITS4. The amplified DNA was purified by ethanol and then was subjected to restriction analysis with the enzymes HaeIII, HinfI, HhaI, TaqI. Then there is listed detection of the PCR product and the restriction fragments by gel electrophoresis. Lengths of the fragments obtained after electrophoresis will be used to identify yeast species isolated from cheeses. In the second part of the thesis in the experimental part we have dealt with evidence of lipolytic activity of the yeast by test on Spirit blue agar.
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Elemental analysis of cheese with white mold on the surface
Pavlechová, Alžbeta ; Vítová, Eva (referee) ; Diviš, Pavel (advisor)
This Master's thesis deals with elementary analysis of cheeses with white mold on the surface. Theoretical part describes general characteristics of cheese, classification of cheeses, their nutritional aspects and characteristics of cheeses with white mold on the surface. Large part is focused on description of mineral substances selected for analysis. At the end of the theoretical part, the Kjeldahl method and emission spectrometry with inductively coupled plasma (ICP-OES) were described. Experimental part deals with preparation of samples, approach of analysis and processing of measured results. Eleven samples of cheeses were used for analysis. These samples were from Czech Republic, France and Slovak Republic. Kjeldahl method was used to determine protein contents and ICP-OES was used for elemental analysis. The results were compared to each other and also with results from other studies. Subsequently, they were statistically processed and evaluated in the final part.
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PCR identification of nonpathogenic bacteria strains in cheeses
Jurečková, Nela ; Doušková, Dagmar (referee) ; Španová, Alena (advisor)
Different species of genus Bifidobacterium are part of human and animal intestinal flora. These bacteria have benefit effects and therefore they are used in foods and pharmaceutical products as probiotics. Cheese is now suitable as a probiotic matrix except yoghurts and fermentated milks. This diploma thesis was focused on optimalization of DNA isolation from bacteria of genus Bifidobacterium. Magnetic microparticles (P(HEMA-co¬-GMA)) were used for DNA isolation in presence of 8% polyethyleneglycol PEG 6000 and 5 M sodium chloride. Phenol extraction weas also used as an isolation method. Isolated DNA was used for amplification in domain, genus and species specific PCRs. Optimized method was tested for detection of bacteria of genus Bifidobacterium in experimentaly prepared probiotic cheeses. These cheeses contained potential probiotic bacteria from Laktoflóra collection. Bacteria were identified into species using species specific PCR. Species Bifidobacterium animalis was identified in all samples of probiotic cheeses.
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Monitoring of fatty acids content during cheese production
Rajnochová, Veronika ; Mikulíková, Renata (referee) ; Vítová, Eva (advisor)
This master thesis deals with the monitoring of fatty acids during production of natural Edam cheeses, i.e. natural hard cheeses with low heat curd, and of processed cheeses, which were produced from them. The theoretical part briefly characterizes the natural Edam cheese and processed cheese, the main attention is paid to lipids, fatty acids and the possibility of their determination. In the experimental part the content of fatty acids in the model samples of natural and processed cheese produced at Tomas Bata University in Zlín was determined. The method according to ISO 1735 was chosen for extraction of lipids from the samples, the method according to ISO 5509 using methanol solution of potassium hydroxide was chosen for the esterification of fatty acids. The resulting methyl esters were determined by gas chromatography with FID detection.
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The addition of carbon dioxide to milk for cheese production
Králová, Petra ; Hrstka, Miroslav (referee) ; Kvasnička, Miloš (advisor)
This work deals with the addition of carbon dioxide to milk for cheese production. The first aim was to elaborate a literary search focused on chemical composition of milk and its changes after addition of carbon dioxide and to describe production processes, with or without addition of carbon dioxide. The opening part was in particular focused on production of cheese with carbon dioxide and what all this gas causes during production. Carbon dioxide significantly decreases pH, thereby preventing from multiplication of undesirable microorganisms, it is also very important for shortening of production time, because it shortens the coagulation time. The main aim of experimental part was to determine the optimum addition of carbon dioxide to milk for production of Balkan cheese and using several analytical methods to compare cheese produced with and without addition of carbon dioxide. The sensory methods suitable for following of sensory differences of produced cheeses were also chosen and applied. By request of Dairy in Polná Ltd., the operation economy was calculated, which revealed that production with carbon dioxide is very useful and can reduce production costs of Balkan cheese, which would certainly be positive. The advantages and disadvantages of cheese production with carbon dioxide for consumers as well as for producer are evaluated as conclusion of this work.
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The optimization and validation of the GC-MS method for assessment of volatile aroma compounds in cheese
Koubek, Miroslav ; Babák, Libor (referee) ; Vítová, Eva (advisor)
This work deals with the introducing of the method for the determination of volatile aroma active compounds in different types of natural and processed cheeses. The theoretical part describes the basic groups of aroma compounds. Than the methods used for their determination with focusing on solid phase microextraction and gas chromatography coupled with mass spectrometry are described. The experimental part deals with the optimization of the selected method parameters. For extracting volatile substances from the sample matrix the fiber DVB/CAR/PDMS 50/30 m was selected, these compounds were then determined by gas chromatography coupled with mass spectrometry. In the frame of validating proces the repeatability of the method was verified, RSDs of retention times
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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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Comparison of fatty acids profile of selected type of cheese
Pop, Zdeněk ; Diviš, Pavel (referee) ; Vítová, Eva (advisor)
This master thesis deals with the determination of bound and free fatty acids in selected types of cheeses with/without „Protected designation of the Europen Union“ and their mutual comparison. The theoretical part focuses on a milk fat, a brief overview of cheeses, protected designation of the Europen Union, lipids, fatty acids and a possibility of their determination. In the experimental part, free and bound fatty acids profile in 12 selected samples of white mold cheeses was determined. The declared amount of total fat was verified. The cheeses were compared by a content of bound and free fatty acids, the profile of fatty acids was compared based on a type of milk used. Finally, the results were statistically treated by PCA method. The method according to ČSN EN ISO 1735 was chosen for extraction of lipids from the cheese samples. A methanolic solution of boron trifluoride was used for fatty acids esterification. The fatty acids methyl esters were determined by gas chromatography with flame ionization detection.
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Changes of aroma active compounds during production of model cheese
Školová, Dominika ; Pořízka, Jaromír (referee) ; Vítová, Eva (advisor)
The aim of the work was identification of aroma active compounds in Moravský bochník cheese type, than discuss their changes during ripening and consider influence of aplication different rates of microbial cultures on number of volatile compounds. SPME-GC-MS was used for identification of volatile compounds. In total, 148 of volatile compounds were identified and 82 of them are considered as aroma active compounds. Three microbial cultures (their combination with predominant thermophilic or mesophilic culture) were used for making samples. The influence of predominant thermophilic/mesophilic culture on number of volatile compounds was not proved. From the point of view of sensory quality, combinations with predominant mesophilic culture proved to be more successful. During ripening, the number of identified compounds was reduced in all the combinations of cultures studied. The optimal time for ripening seems to be three months.
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Volatile profile of Edam type cheese
Balej, Marek ; Kovalčík, Adriána (referee) ; Vítová, Eva (advisor)
This bachelor thesis is focused on specification volatile profile of eidam cheese types, which are natural semi hard cheeses with low heat curd. Subject of theoretical part is basic differentiation of cheeses, description of chemical composition and characteristic of eidam cheese types. After that, issue of their manufacturing process is processed and aroma active substances are described. In the last part of this section, the attention is focussed on specification method of solid phase microextraction connected with gas chromatography with mass spectrometry detection. Experimental part deals with HS-SPME-GC-MS method application on identification of volatile compounds in eidam cheese types. Samples of model cheese were manufactured at Tomas Bata University in Zlín with the use of various added microbial starter cultures and eidam type cheeses with various fat content bought on the market. A total of 64 compounds were identified in samples; of those 18 alcohols, 11 esters, 9 ketones, 7 aldehydes, 5 acids, 3 lactones, 2 terpene hydrocarbons, 2 terpene alcohols, 1 terpene ketone, 1 terpene aldehyde, 4 sulphurous compounds and 1 phenol. The differences were found among model cheese samples and market bought samples in the case of number and type of volatiles.
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