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Microbial profile of model cheese
Lavičková, Ivana ; Veselá, Mária (referee) ; Vítová, Eva (advisor)
This Diploma thesis deals with the identification of microorganisms in samples of experimentally produced cheese. Model samples of cheese were produced in association with a private manufacturer. Raw organic milk was used to make the cheese. The theoretical part provides an overview of the issues such as the characteristics of the cheese, its properties and compounds. A special chapter is dedicated to molecular diagnostic methods, which serve for identification of microorganisms. In the experimental part of the thesis were identified some microorganisms in the samples. A polymerase chain reaction was used. The DNA was isolated from coarse lysates using phenol extraction; it was amplified using specific primers and demonstrated by gel electrophoresis. DNA of lactic acid bacteria (Lactobacillus spp., Lactococcus spp.) and yeast was ascertained in the cheese. The samples do not contain DNA of pathogenic genera Bacillus and Salmonella.
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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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Foodborne Staphylococcus Aureus: Identification and Enterotoxin Production in Milk and Cheese.
Hrušková, Vendula ; Španová, Alena (referee) ; Kmet,, Vladimír (referee) ; Kaclíková, Eva (advisor)
Onemocnění z potravin (alimentární onemocnění) vyvolaná bakteriemi jsou stále aktuálním tématem v celosvětovém měřítku. Abychom zajistili výrobu zdravotně nezávadných potravin, je potřeba nových poznatků o virulenci patogenů, které by doplnily již známé skutečnosti o jejich růstu a přeživání v potravinách. Také potřebujeme vyvíjet rychlé a citlivé metody na detekci těchto patogenů. Dizertační práce popisuje metodu na detekci S. aureus v potravinách, která je založená na PCR v reálném čase ve spojení s namnožením v selektivním médium. Dále pojednává o vlivu environmentálních faktorů na růst S. aureus a tvorbu enterotoxinů v mléce a sýrech. Vyvinuli jsme rychlou a citlivou metodu na detekci S. aureus v potravinách s použitím selektivního namnožení a PCR v reálném čase. Nově vyvinutá metoda umožnila detekci S. aureus na druhý den od přijetí vzorku. Tato metoda může být použita jako rychlejší, citlivějsí a vysoce specifická alternativní metoda ke konvenční mikrobiologické metodě. Zkoumali jsme vliv tří různých teplot, 8°C, 12°C a 20°C na růst S. aureus a tvorbu enterotoxinu D v pasterizovaném mléce a na růst, expresi genu sed a tvorbu enterotoxinu D v tekutém médiu s extraktem z mozku a srdce (BHI). Experimenty byly prováděny v malých skleněných fermentorech po 6 dní. Genová exprese byla sledována pomocí qRT-PCR a tvorba enterotoxinu D byla měřena pomocí imunologické metody ELISA. Růstová křivka v BHI měla stejný průběh při 20°C a 12°C, ale v při 12°C začal růst se spožděním. Při 8°C nebyl pozorován žádný růst. Růst S. aureus v mléce byl ve srovnání s BHI menší. sed mRNA byla detekována při 20°C po 4 hodinách a při 12°C po 7 hodinách a produkce enterotoxinu se objevila v exponenciální fázi růstu. V mléce se produkce SED při 20°C a při 12°C objevila dříve, ale celkové množství vyprodukovaného SED bylo nižší než v BHI. Při 8°C nebyla pozorována žádná produkce SED stejně jako v BHI. Dále byl zkoumán společný vliv nízké teploty 12°C a přítomnosti kompetitivní doprovodné mikroflóry pocházející ze surového mléka na růst S. aureus a produkci enterotoxinu v pasterizovaném mléce. Byl pozorován inhibiční účinek na růst a produkci enterotoxinů a vliv kompetice byl výraznější než vliv nízké teploty. Produkce enterotoxinu byla nízká a odpovídala růstu. Snížením množství doprovodné mikroflóry a zvýšením inokula došlo pouze k nepatrnému zvýšení produkce enterotoxinu. V další fázi byly dva různé typy sýrů zaočkovány S. aureus za účelem simulace sekundární kontaminace při výrobě sýrů. Vzorky byly odebírány v průběhu 4 týdnů. Kritické faktory jako jsou kompetitivní mikrofóra nebo pH, které jsou zodpovědné za regulaci virulence S. aureus byly sledovány. Snažili jsem se rozlišit situace při kterých: (i) není pozorován růst, ale objevuje se produkce enterotoxinu a (ii) dochází k růstu ale bez produkce enterotoxinu.
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The assessment of basic chemical parameters of natural cheese
Školová, Dominika ; Babák, Libor (referee) ; Vítová, Eva (advisor)
The aim of this work was to determine basic chemical parameters of natural cheese, namely Camembert type (white mold cheese) and Emmentaler type (cheese with high-heat curd). Model samples of cheese were produced in a pilot plant using unpasteurized milk in"organic" quality. Based on the literature search following parameters suitable for simple and fast characterization of cheese composition were selected: dry matter (drying to constant weight), fat in dry matter (calculated), total nitrogen (resp. determination of protein content) by the Kjeldahl method and fats, resp. total lipids (extraction with solvent). The results were finally compared with samples of the corresponding cheese type purchased on the market.
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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 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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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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Sensory evaluation of cheeses
Pecinová, Ester ; Vránová, Dana (referee) ; Vítová, Eva (advisor)
This bachelor thesis deals with the sensory evaluation of cheeses. The thesis focuses on Edam cheese and the selection of methods for its sensory analysis. In the theoretical part natural cheeses are characterised, their chemical composition, physical and chemical properties as well as their sensory properties are described, further they are classified from several points of view and also individual steps of manufacturing process of Edam cheese are described. After that the literature search was made focused on sensory evaluation, within the methods were chosen for the experimental part, specifically measuring of overall preference and liking/disliking, appearance, colour, texture, aroma and flavour ratings using the hedonic scale and rating of chosen flavour descriptors by the profile method. In the experimental part the selected sensory methods were applied on 3 samples of Edam cheese, manufactured in 3 different modes of heat treatment of milk. Two sensory panels were involved in the evaluation: consumers and experts. Cheese from the first production (65 °C 30 min) was evaluated as the most acceptable; on the contrary cheese from the second production (80 °C 30 s) was evaluated as the least acceptable.
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The assessment of fatty acids in cheeses
Rajnochová, Veronika ; Omelková, Jiřina (referee) ; Vítová, Eva (advisor)
This bachelor thesis deals with the determination of fatty acids in natural Edam cheese. The theoretical part briefly characterize the natural Edam cheese, main attention is paid to lipids, fatty acids and the possibility of their determination by gas chromatography. In the experimental part the content of fatty acids in the model samples of natural Edam 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 assessment of aroma active compounds in cheeses
Ryglová, Hana ; Diviš, Pavel (referee) ; Vítová, Eva (advisor)
This work deals with aroma active compounds of Edam cheese, i.e. natural hard cheese with low heat curd. Aroma active compounds contribute to overal aroma of cheese. They are volatile compounds, which include alcohols, aldehydes, ketones, fatty acids, esters, lactones, terpenes etc. These compounds were identified and quantified using SPME/GC/FID method in the model samples of Edam cheese, produced at Tomas Bata University in Zlin. In total 18 volatile compounds were identified, 3 aldehydes, 4 ketones, 7 alcohols, 1 ester and 3 acids. Differences in number of compounds identified, as well as in the contents of them, were found between samples. Low number of compounds and also their low total content correspond to the initial phase of cheese ripening.
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