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Influence of storage on the microbial composition of French Saint-nectaire cheese
Šislerová, Lucie ; Mikulíková, Renata (referee) ; Brázda, Václav (advisor)
The aim of my work is the comparison of microbial composition between farmtype and dairytype of Saint-nectaire cheese and the influence of storage time and temperature on the development of microbial composition, content of fatty acids and aromatic substances. Selected microorganisms were identified by RT-PCR. In addition, Penicillium roqueforti and fuscoglaucum have been identified in the Saint-nectaire farm type compared to the dairy type. In both types of cheese, the highest amount of selected microorganisms was detected in fresh cheese. When stored at 20 °C, an increase over fresh cheese occurred in the following microorganisms: Streptococcus thermophilus, Lactobacillus bulgaricus, Cladosporium herbarum and Penicillium commune and camemberti, and the presence of contaminants and pathogens was noted. After one week of storage at 20 °C, they were Micrococcus luteus, Salmonella enterica and Staphylococcus aureus, and after another two weeks of storage, Listeria monocytogenes was identified. The fatty acid and volatile compounds were compared for five samples: fresh cheese, cheese stored in the refrigerator for one week and three weeks and cheese stored at 20 °C for one week and three weeks. The content of bound and free fatty acids was measured, both by GC-FID. The content of bound fatty acids was comparable in all measured samples. The highest content of free fatty acids was in the cheese after three weeks of storage at 20 °C. The most common fatty acid is palmitic acid. Volatiles were determined by HS-SPME-GC-MS. The most volatiles were identified in the cheese after three weeks at 20 °C and in the cheese after one week in the refrigerator. The most represented groups were alcohols, ketones and acids.
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Monitoring of the influence of yeasts on the chemical and sensory qualities of manufactured wine
Petrášová, Ludmila ; Vítová, Eva (referee) ; Vránová, Dana (advisor)
The thesis deals with monitoring of the yeast's impact to the chemical and sensorial characteristics of produced wine. The aim of experimental part was obtaining of the aroma-active substances in the fermenting must and wine Hibernal and wine Pinot Blanc. SPME-GC-MS methods were used for identify wines and must aroma. The same autochthonous yeasts were used for wine production. This yeast was isolated from surface of grapes in our laboratory. It was found that both wines have a similar aromatic profile. The next aim was the monitoring of chemical parameters of samples and their changes. For this measurement were used spectrophotometric methods and HPLC methods. The last goal of the thesis was the isolation and identification of yeasts from wine Pinot Blanc by PCR-RFLP. These yeasts were then compared with yeasts isolated from Hibernal must. Identification of yeasts were done by amplification 5,8S-ITS DNA stretches using primers ITS1 and ITS4. Restriction endonuclease HaeIII, HinfI, HhaI and TaqI. were used for restriction analysis then.
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Characterization of new czech hop varieties
Faruzel, Vojtěch ; Diviš, Pavel (referee) ; Pořízka, Jaromír (advisor)
In this thesis the problem of characterization of new Czech hop varieties was investigated. The selected new varieties were Mimosa, Jazz and Blues. Their composition was compared with the widely used varieties Žatecký poloraný červeňák and Kazbek. The content of -bitter acids and -bitter acids, total phenolic content, flavonoid content and antioxidant activity were determined by UV-VIS spectroscopy for all hop varieties. The composition of hop essential oils was estimated by SPME-GC-MS. The diversity of the hop varieties was confirmed from the measured data by statistical analysis. The new varieties showed statistically significant differences in all monitored parameters, especially in comparison with the varieties Žatecký poloraný červeňák and Kazbek. The quantitatively different representation of -bitter acids and -bitter acids has an influence on the character and intensity of bitterness of these hop varieties. The composition of the hop essential oils, the content of phenolic substances, flavonoids and antioxidant activity are reflected in the different organoleptic properties of the hops analysed and of the beer.
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Influence of storage on the microbial composition of French Saint-nectaire cheese
Šislerová, Lucie ; Mikulíková, Renata (referee) ; Brázda, Václav (advisor)
The aim of my work is the comparison of microbial composition between farmtype and dairytype of Saint-nectaire cheese and the influence of storage time and temperature on the development of microbial composition, content of fatty acids and aromatic substances. Selected microorganisms were identified by RT-PCR. In addition, Penicillium roqueforti and fuscoglaucum have been identified in the Saint-nectaire farm type compared to the dairy type. In both types of cheese, the highest amount of selected microorganisms was detected in fresh cheese. When stored at 20 °C, an increase over fresh cheese occurred in the following microorganisms: Streptococcus thermophilus, Lactobacillus bulgaricus, Cladosporium herbarum and Penicillium commune and camemberti, and the presence of contaminants and pathogens was noted. After one week of storage at 20 °C, they were Micrococcus luteus, Salmonella enterica and Staphylococcus aureus, and after another two weeks of storage, Listeria monocytogenes was identified. The fatty acid and volatile compounds were compared for five samples: fresh cheese, cheese stored in the refrigerator for one week and three weeks and cheese stored at 20 °C for one week and three weeks. The content of bound and free fatty acids was measured, both by GC-FID. The content of bound fatty acids was comparable in all measured samples. The highest content of free fatty acids was in the cheese after three weeks of storage at 20 °C. The most common fatty acid is palmitic acid. Volatiles were determined by HS-SPME-GC-MS. The most volatiles were identified in the cheese after three weeks at 20 °C and in the cheese after one week in the refrigerator. The most represented groups were alcohols, ketones and acids.
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Characterization of new czech hop varieties
Faruzel, Vojtěch ; Diviš, Pavel (referee) ; Pořízka, Jaromír (advisor)
In this thesis the problem of characterization of new Czech hop varieties was investigated. The selected new varieties were Mimosa, Jazz and Blues. Their composition was compared with the widely used varieties Žatecký poloraný červeňák and Kazbek. The content of -bitter acids and -bitter acids, total phenolic content, flavonoid content and antioxidant activity were determined by UV-VIS spectroscopy for all hop varieties. The composition of hop essential oils was estimated by SPME-GC-MS. The diversity of the hop varieties was confirmed from the measured data by statistical analysis. The new varieties showed statistically significant differences in all monitored parameters, especially in comparison with the varieties Žatecký poloraný červeňák and Kazbek. The quantitatively different representation of -bitter acids and -bitter acids has an influence on the character and intensity of bitterness of these hop varieties. The composition of the hop essential oils, the content of phenolic substances, flavonoids and antioxidant activity are reflected in the different organoleptic properties of the hops analysed and of the beer.
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Monitoring of the influence of yeasts on the chemical and sensory qualities of manufactured wine
Petrášová, Ludmila ; Vítová, Eva (referee) ; Vránová, Dana (advisor)
The thesis deals with monitoring of the yeast's impact to the chemical and sensorial characteristics of produced wine. The aim of experimental part was obtaining of the aroma-active substances in the fermenting must and wine Hibernal and wine Pinot Blanc. SPME-GC-MS methods were used for identify wines and must aroma. The same autochthonous yeasts were used for wine production. This yeast was isolated from surface of grapes in our laboratory. It was found that both wines have a similar aromatic profile. The next aim was the monitoring of chemical parameters of samples and their changes. For this measurement were used spectrophotometric methods and HPLC methods. The last goal of the thesis was the isolation and identification of yeasts from wine Pinot Blanc by PCR-RFLP. These yeasts were then compared with yeasts isolated from Hibernal must. Identification of yeasts were done by amplification 5,8S-ITS DNA stretches using primers ITS1 and ITS4. Restriction endonuclease HaeIII, HinfI, HhaI and TaqI. were used for restriction analysis then.
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