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Changes in selected local fruits during freezing.
Matějková, Markéta ; Melounová, Jitka (referee) ; Márová, Ivana (advisor)
This diploma thesis was focused on study of low-molecular antioxidants present in various kinds of fruits, namely berries. In theoretical part detailed characterization of antioxidants studied in presented work and their biological effects are introduced. Further, principals of processing and storage of specified species of fruits are discussed. Changes observed during storage of specific fruits are described too. In practical part changes in content of selected antioxidants in berries were followed. As studied material strawberries, raspberries, blueberries, red and black currants were used. All kind of these fruits was stored in fridge for six months using several different kind of processing. Berries were stored as whole fruits, whole osmotically processed fruits by sucrose, raw pulp and sweetened pulp. At first, starting values of selected antioxidant parameters were measured in fresh fruits (ascorbate, total antioxidant activity, total phenolics, catechins and individual flavonoids). After freezing the same parameters were measured regularly in two month periods. As the most suitable method of fruit processing, with regard to antioxidant content, storage of the whole fruits or pulp can be recommended. Content of ascorbate decreased in all forms and species of the processed fruits during all the time of storage. Oppositely, the content of other studied antioxidants exhibited fluctuations or increasing trend. Sensory analysis was proved for the whole fruits and also for whole sweetened fruits.
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Analysis of some active substances in different products from rice
Valentová, Radka ; Melounová, Jitka (referee) ; Márová, Ivana (advisor)
Presented diploma thesis is focused on analysis of selected biologically active substances in different kinds of natural and peeled rice. In rice samples phenolic compounds, antioxidant activity, content of saccharides and vitamin C were analysed. Active substances and saccharides were analysed by UV-VIS spectrophotometry and RP-HPLC-UV/VIS. Content of phenolic compounds and saccharides was measured before and after acid hydrolysis. The content of these compounds increased several times because of release of active substances from glycosides. As a part of diploma thesis basic sensory analysis was performed and consumer questionnaires were evaluated. The highest level of antioxidant activity was detected in Indian Wild rice. The highest content of total polyphenols and flavonoids was detected in Red Rice Natural before acid hydrolysis. After acid hydrolysis the highest content was detected in Indian Wild rice. The highest content of individual flavonoids, phenolic acids and catechins was detected in natural rice Indian Wild, Rice Three colours and in two samples of rice parboiled. The highest content of total and reducing saccharides was found in rice Indian Wild before hydrolysis, while after hydrolysis the content was very similar in all rice samples. The amount of individual monosaccharides after acid hydrolysis increased, while total content of disaccharides decreased. The highest value of simple sugars was detected in rice parboiled and Indian Wild rice. The content of vitamin C was detected only in four rice kinds - in two samples of rice parboiled, Rice Three colours and rice Indian Wild.
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Study of antimutagenic properties of selected kinds of honey
Lichnová, Andrea ; Melounová, Jitka (referee) ; Márová, Ivana (advisor)
This diploma thesis is focused on study of antimutagenic properties in selected kinds of honey and propolis. In honey extracts compounds with antimutagenic and antioxidant effect were analysed by spectrophotometry, RP/HPLC/UV-VIS, HPLC/PDA and on-line LC/MS. Further, effect of long-term storage on active compound levels was studied. Antimutagenic activity was tested by simple eukaryotic system - yeast strain Saccharomyces cerevisiae D7. The highest antimutagenic effect and simultaneously the highest stability of antimutagenity values was found in several kinds of multi-floral honey, rape seed honey, honey from eucalypt and orange flowers and in honeydew honey. Samples obtained from trade network exhibited at general lower antimutagenity values when compared with samples from bee-keeper. The highest content of total phenolics was detected in honey with royal yelly, the lowest content was measured in acacia honey. The highest values of total flavonoids exhibited buckwheat and eucalypt flower honey. Total phenolic content was substantially changed during long-term storage (decrease about 50 -70 %), while total flavonoid content was stable and no significant changes during storage were observed. Honey with high antimutagenity values exhibited also higher phenolic and predominantly flavonoid content and high antioxidant activity. Because of relative stability and low changes in most of honey samples during storage it can be concluded that honey belong to foodstuffs which are able to conserve their positive nutritive properties for a long time.
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Changes in selected local fruits during freezing.
Matějková, Markéta ; Melounová, Jitka (referee) ; Márová, Ivana (advisor)
This diploma thesis was focused on study of low-molecular antioxidants present in various kinds of fruits, namely berries. In theoretical part detailed characterization of antioxidants studied in presented work and their biological effects are introduced. Further, principals of processing and storage of specified species of fruits are discussed. Changes observed during storage of specific fruits are described too. In practical part changes in content of selected antioxidants in berries were followed. As studied material strawberries, raspberries, blueberries, red and black currants were used. All kind of these fruits was stored in fridge for six months using several different kind of processing. Berries were stored as whole fruits, whole osmotically processed fruits by sucrose, raw pulp and sweetened pulp. At first, starting values of selected antioxidant parameters were measured in fresh fruits (ascorbate, total antioxidant activity, total phenolics, catechins and individual flavonoids). After freezing the same parameters were measured regularly in two month periods. As the most suitable method of fruit processing, with regard to antioxidant content, storage of the whole fruits or pulp can be recommended. Content of ascorbate decreased in all forms and species of the processed fruits during all the time of storage. Oppositely, the content of other studied antioxidants exhibited fluctuations or increasing trend. Sensory analysis was proved for the whole fruits and also for whole sweetened fruits.
|
|
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Analysis of some active substances in different products from rice
Valentová, Radka ; Melounová, Jitka (referee) ; Márová, Ivana (advisor)
Presented diploma thesis is focused on analysis of selected biologically active substances in different kinds of natural and peeled rice. In rice samples phenolic compounds, antioxidant activity, content of saccharides and vitamin C were analysed. Active substances and saccharides were analysed by UV-VIS spectrophotometry and RP-HPLC-UV/VIS. Content of phenolic compounds and saccharides was measured before and after acid hydrolysis. The content of these compounds increased several times because of release of active substances from glycosides. As a part of diploma thesis basic sensory analysis was performed and consumer questionnaires were evaluated. The highest level of antioxidant activity was detected in Indian Wild rice. The highest content of total polyphenols and flavonoids was detected in Red Rice Natural before acid hydrolysis. After acid hydrolysis the highest content was detected in Indian Wild rice. The highest content of individual flavonoids, phenolic acids and catechins was detected in natural rice Indian Wild, Rice Three colours and in two samples of rice parboiled. The highest content of total and reducing saccharides was found in rice Indian Wild before hydrolysis, while after hydrolysis the content was very similar in all rice samples. The amount of individual monosaccharides after acid hydrolysis increased, while total content of disaccharides decreased. The highest value of simple sugars was detected in rice parboiled and Indian Wild rice. The content of vitamin C was detected only in four rice kinds - in two samples of rice parboiled, Rice Three colours and rice Indian Wild.
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Study of antimutagenic properties of selected kinds of honey
Lichnová, Andrea ; Melounová, Jitka (referee) ; Márová, Ivana (advisor)
This diploma thesis is focused on study of antimutagenic properties in selected kinds of honey and propolis. In honey extracts compounds with antimutagenic and antioxidant effect were analysed by spectrophotometry, RP/HPLC/UV-VIS, HPLC/PDA and on-line LC/MS. Further, effect of long-term storage on active compound levels was studied. Antimutagenic activity was tested by simple eukaryotic system - yeast strain Saccharomyces cerevisiae D7. The highest antimutagenic effect and simultaneously the highest stability of antimutagenity values was found in several kinds of multi-floral honey, rape seed honey, honey from eucalypt and orange flowers and in honeydew honey. Samples obtained from trade network exhibited at general lower antimutagenity values when compared with samples from bee-keeper. The highest content of total phenolics was detected in honey with royal yelly, the lowest content was measured in acacia honey. The highest values of total flavonoids exhibited buckwheat and eucalypt flower honey. Total phenolic content was substantially changed during long-term storage (decrease about 50 -70 %), while total flavonoid content was stable and no significant changes during storage were observed. Honey with high antimutagenity values exhibited also higher phenolic and predominantly flavonoid content and high antioxidant activity. Because of relative stability and low changes in most of honey samples during storage it can be concluded that honey belong to foodstuffs which are able to conserve their positive nutritive properties for a long time.
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