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Characterization of lipids in fresh cheeses
Vaňková, Veronika ; Křikala, Jakub (referee) ; Vítová, Eva (advisor)
This bachelor thesis deals with the determination of fatty acids in samples of fresh cheeses with or without the addition of plant extracts (rhyme, echinacea), produced in laboratory conditions at FCH BUT. The theoretical part of the thesis focuses on the general characterization of lipids and fatty acids. The next part discusses the characterization, division, and methods of cheese production, focusing mainly on fresh cheeses. The end of the work is devoted to gas chromatography as a method for the determination of fatty acids in cheese samples. The experimental part aimed to determine the content of fatty acids in the samples of fresh cheese. For the extraction of lipids from cheese samples, the choice of the method was according to ČSN EN ISO 1735. Acid esterification with boron trifluoride as a catalyst was used for the preparation of fatty acid methyl esters. The determination of fatty acid methyl esters was performed by gas chromatography with a flame ionization detector (FID). A total of 14 fatty acids were identified in all samples in a bound and free form. Myristric, palmitic, stearic and oleic acids predominated in all samples, which is in agreement with the knowledge of the composition of milk fat. The obtained results show, that even due to slight differences in the content of individual fatty acids, the addition of extracts does not affect the composition of fatty acids in fresh cheeses.
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DNA extraction from cheeses for polymerase chain reaction analysis
Mohelský, Tomáš ; Rittich, Bohuslav (referee) ; Španová, Alena (advisor)
This work was focused on DNA isolation from cheeses for the use in polymerase chain reaction. First, there was optimised the procedure of homogenisation of different types of cheeses from commercial sources, cell lysis and DNA isolation. DNA was isolated using magnetic microspheres and phenol extraction. It was shown that the DNA was amplified in PCR for domain Bacteria after dilution. Next, there was optimised the procedure of DNA isolation from fresh cheeses and from contaminated fresh cheeses and their pickles. DNA from all samples was amplified in PCR. The presence of DNA of domain Bacteria and yeast DNA was demonstrated. In the last part of the work, there were optimised the preparation of PCR mixtures and bacterial DNA amplification in PCR with primers with clamp (F357-GC and R518). Synthetized PCR products were analysed using DGGE. It was shown that amplicons of DNA isolated from cheeses and pickles differ in positions and numbers. Larger number of bands of different intensities was detected after amplification of DNA isolated from contaminated pickles.
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Processing of fresh cheese depending on selected factors
KOŘÁN, Jakub
Bachelor thesis is focused on processing of fresh cheese depending on selected factors. The cheeses were made in laboratory for this purpose and some factors influencing cheese making were tested. The performed experiments show the effect on cheese yield, milk composition, good manufacturing process and different fermentation temperature. This influence is particularly evident in the overall yield of cheese curd, weight of curd, release rate of whey and pH of curd. The performed experiments can lead to conclusion that each of these factors affects the overall quality of the curd. From the perspective of producers of fresh cheeses is important to monitor these factors as compliance with proper procedure and avoiding the factors reducing yield, will have a positive economic impact.
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