The presented diploma thesis is focused on the preparation and the monitoring of the biological stability of beer enriched with probiotics. Probiotic bacterial strains of Lactobacillus acidophilus, Bifidobacterium breve and Bifidobacterium bifidum were used in this study. The theoretical part is divided into two sections. In the first section, probiotics are generally characterized, and their role within a gut microbiota is described. Next, the microbiology of particular probiotic microorganisms including the genera of Lactobacillus and Bifidobacterium is described. Then, some factors influencing the viability and the growth of probiotics are stated. In this section, biological effects of probiotics on the human organism and their potential clinical applications are described. The second section of the theoretical part deals with the technology of brewing, the chemical composition of beer and particular beer styles. In the experimental part, the methods of probiotic bacterial cell concentration and viability determination were optimized. Several techniques for determination of these parameters were selected, particularly the cultivation method, flow cytometry and the spectrophotometric measurement of turbidity. Then, the growth curves of the probiotic strains were measured in MRS medium. Probiotic bacteria were cultivated in model beer samples, i.e. in MRS media with several different concentrations of ethanol. It is possible to say that ethanol did not have significant effect on probiotics growth. Next, experimental cultivations of individual probiotic bacteria and their mixtures in nine real beer samples were conducted. No increase of viable cells concentrations was detected in the samples. On the contrary, a decrease of the concentrations was observed, mainly in the samples with individual bacterial strains. However, certain values of viable cells concentrations were determined at the end of the cultivations in all cases. A pale, top-fermented beer was brewed and supplemented with probiotics, and the concentrations of viable probiotic cells were monitored during 37 days of fermentation. A decrease of concentrations by two orders of magnitude of CFU/ml was observed in almost all samples. Yet, viable cells of probiotic bacteria were detected in all samples of beer at the end of the fermentation. Maximal concentration of viable probiotic cells in the brewed beer was determined with the cultivation method at (3,80 ± 0,14)10^5 CFU/ml. Chosen samples were analyzed with HPLC-RI method that quantified the common beer concentrations of ethanol in all chosen samples, lactic acid was not detected. Sensory analysis was conducted as well. Based on the results of the experimental part and the bibliography, an optimal technology of the preparation of beer enriched with probiotics is discussed in this study.
| Identifer | oai:union.ndltd.org:nusl.cz/oai:invenio.nusl.cz:401899 |
| Date | January 2019 |
| Creators | Kočnar, Michal |
| Contributors | Mikulíková, Renata, Márová, Ivana |
| Publisher | Vysoké učení technické v Brně. Fakulta chemická |
| Source Sets | Czech ETDs |
| Language | Czech |
| Detected Language | English |
| Type | info:eu-repo/semantics/masterThesis |
| Rights | info:eu-repo/semantics/restrictedAccess |
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