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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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Influence of production environment on the occurrence of contaminating Penicillium in smear ripened cheese
Veselá, Vendula ; Brázda, Václav (referee) ; Vítová, Eva (advisor)
The topic of this thesis is the monitoring of the environment in a cheese production plant specializing in cheese ripened under a smear rind. The aim is to evaluate the occurrence of Penicillium mold as the main contaminant microorganism, depending on the sampling location and production time. Air samples were collected throughout the production process using the sedimentation method at 21 designated locations. The total number of microorganisms, selected groups of microorganisms, and the target microorganism (Penicillium mold) were monitored in the collected samples using cultivation (according to ČSN standards), microscopic, and molecular diagnostic techniques. The aim was to evaluate the occurrence of Penicillium citrinum, chrysogenum and commune species in dependence on the sampling location and production time. As part of the production screening, the broader microflora was first evaluated, followed by monitoring for contaminating molds. Using macroscopic and microscopic methods, 36 morphologically distinct colonies were selected. Microscopic analysis confirmed the presence of bacteria, yeasts and molds of the genera Penicillium, Cladosporium and Aspergillus. In order to identify the microorganisms present, an analysis using the polymerase chain reaction (PCR) method was performed, preceded by DNA isolation using the NucleoSpin Microbial DNA kit and phenol extraction. Based on real-time PCR results, the occurrence of contaminating Penicillium and Cladosporium molds was detected even in the early stages of production. Molds from these genera are found throughout the entire facility except for the single room that serves as a curd cooler before forming. Aspergillus mold, in the form of yellow mold with white mycelium on the edge of the colony, was detected only once in the drying room where cheese ripening occurs, and confirmed by microscopic observation. The genus Cladosporium was found in five morphologically distinct forms in the production environment. In addition, DNA was isolated from 11 morphologically distinct bacteria. Real-time PCR identified this DNA as belonging to coryneforms, with four of them belonging to the genus Brevibacterium. The genus Penicillium was represented by 13 morphologically distinct colonies, real-time PCR confirmed the presence of Penicillium commune and Penicillium chrysogenum. In addition to the mentioned molds, 11 morphologically distinct bacteria were detected, from which DNA was isolated. Real-time PCR identified this DNA as belonging to coryneforms, with 4 of them belonging to the genus Brevibacterium. The results of this work completely map the contamination of the production environment of the plant, and based on these results, methods for environmental sanitation were proposed to ensure the decontamination of the production process.
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