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Changes in the sensory quality and volatile compounds profile of smear ripened cheese during storage
Šebestová, Adéla ; Zemanová, Jana (referee) ; Vítová, Eva (advisor)
This bachelor thesis deals with the changes in sensory quality, volatile compounds profile and microbial profile of two smear ripened cheese, Olomoucké tvarůžky and Romadur, during their storage for four weeks. The sensory analysis, specifically the assessment of appearance, colour, texture, aroma and taste, showed differences between the two cheeses, which increased during storage (ripening). The greatest differences were observed in the assessment of taste, which improved during ageing for Olomoucké tvarůžky and deteriorated for Romadur. Analysis of volatile compounds by headspace solid-phase microextraction coupled with gas chromatography and mass detection revealed the presence of 57 substances belonging to 9 chemical groups. The composition of the cheese varied in terms of number and content of compounds, with alcohols, ketones and acids being the most abundant. In Romadur, esters predominated quantitatively, and in Olomoucké tvarůžky, sulphur compounds. The total amount of volatile substances in tvarůžky increased during maturation, whereas the opposite was true for Romadur. Microbial analysis showed the presence of a diverse microbiome on the surface of the cheese. There were slight differences between the microbial composition of the cheeses. There was no evidence of change in the microbiome during ripening. The qPCR method was used to identify the microorganisms present.
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Classic vs. bulgarian yogurt - sensory quality vs. chemical and microbiological composition
Podloučková, Michaela ; Němcová, Andrea (referee) ; Vítová, Eva (advisor)
This thesis compares classic and Bulgarian yoghurt in terms of volatile content, sensory quality, and microbial profile. The volatiles were identified and semi-quantified by gas chromatography with mass detection in conjunction with solid phase microextraction, whereas classical culture followed by real-time polymerase chain reaction (PCR) was used to determine the microbial profile. Sensory analysis consisted of evaluation by graphic scales, profile and ordinal tests. In the experimental part, 3 samples were produced, a "classic" white and Bulgarian yoghurt made from commercial yoghurt cultures, and a traditional Bulgarian yoghurt imported directly from Bulgaria. Based on the PCR analysis performed, bacterial DNA was confirmed in all yogurts, only the traditional Bulgarian yogurt also contained yeast DNA. The Bulgarian traditional yoghurt thus differed in its detectable yeast taste, but above all in the qualitative and quantitative composition of the volatile substances. Of the 29 compounds identified, 20 were present in this yoghurt; esters were the main group, while ketones predominated in the other yoghurts. From a sensory point of view, the Bulgarian yoghurt made from commercial culture was the best evaluated, with a pleasant appearance, a pleasant smell and a pleasantly sour taste and an overall excellent sensory quality.
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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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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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