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Effect of antimicrobial substances on "raw food" durability
Horká, Daniela ; Skoumalová, Petra (referee) ; Němcová, Andrea (advisor)
Submitted diploma thesis deals with an effect of antimicrobial substances on raw food durability. Nowadays, the raw food has become very required style of nutrition, which is being practised by more and more people. The issue is that this kind of alimentation, especially vegetable raw food is not prepared in heat treatment which is higher than 42–45 °C. The main aim of the thesis is to study antioxidant and antibacterial properties of the herbal and spice extracts and their following implementation into raw desserts to prolong their durability. At the beginning of the theoretical part, there is an analysis of the issue of raw food and the description of micro-organisms, which are mostly occurred on plant materials. Afterwards, selected herbs and spices, and mechanisms of their antimicrobial effects, and also the methods used to test the products are characterised. The experimental part focuses on characterization of ethanol extracts from 13 selected kinds of spices and herbs. The determination of biologically active substance was accomplished, specifically, polyphenols, flavonoids, anthocyanins and their antioxidant properties. Moreover, these extracts were tested to antimicrobial effect towards gram-positive species of germs Micrococcus luteus, gram-negative species of germs Escherichia coli and yeast Candida glabrata. The molecular part of the thesis contains the DNA isolation from the tested raw material, which was enriched of combination of the selected herbs and spices. Change of expiry date of selected samples of raw desserts was monitored. The presence of chosen micro-organisms was confirmed by the PCR method.
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The negative effect of raw foods due to possible microbial contamination
Šťastná, Martina ; Hlaváček, Viliam (referee) ; Němcová, Andrea (advisor)
Raw diet is the current trend in nutrition, mainly because of the consumption of a balanced diet with a high proportion of health benefits. The basis is the consumption of fresh foods that have not undergone a heat treatment exceeding 42 - 45 ° C. The topic of the bachelor thesis is the general characterization of raw diet, safety of possible microbial contamination and determination of important nutrients and active substances contained in raw products. There are described the most widespread types of meals, approximation of raw diet in terms of its advantages and disadvantages. Also, there are described the most important bacteria, yeasts and molds occurring on fruits and vegetables. By selected methods described in the theoretical part, some nutrients and active ingredients in raw stick samples were determined. The experimental part describes the procedures and principles for the determination of these substances, and last but not least, the real-time PCR methods, agarose gel electrophoresis and the method of sample inoculation for selective solid media that have brought closer the possibility of occurrence of undesirable microorganisms in raw bars and cake. Despite the large number of benefits of raw food consumption and products made from it, it is necessary to take care of its health also in terms of possible contamination by microorganisms. The risk is that the food is not free from unwanted microorganisms during preparation. This is the reason why the raw products are consumed in the shortest possible time after opening, because they become easily a nutrition source for different types of microorganisms due to their composition.
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Microbial contamination of raw food and cereal products
VENGLOVIČOVÁ, Kristýna
Plasma has been increasingly used in recent years due to its lethal effect on microorganisms. Foods treated in this way are not a risk to humans in terms of chemical substance. The literature search is focused on raw foods. Description of pathogenic microorganisms frequently occurring on seeds and methods of disposal feasible in accordance with the rules of the raw diet. The aim of this bachelor thesis was to evaluate the effect of low-temperature plasma on seeds. Seed groups were exposed to plasma for 4, 5, 6, 7 and 8 minutes. Seeds of mung beans, broccoli, watercress, radish and barley were treated with the plasma generated in the vacuum chamber. First of all was evaluated the inhibitory effect of plasma treatment on microorganisms occurring on seeds. Furthermore was monitored the impact on the growth of sprouts and roots. Could not be demonstrated the inhibitory effect of plasma on microorganisms present on seeds. The treated seeds compared to the untreated control group were contaminated with a similar amount of microorganisms. The effect on seed development was different for each species.
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Effect of antimicrobial substances on "raw food" durability
Horká, Daniela ; Skoumalová, Petra (referee) ; Němcová, Andrea (advisor)
Submitted diploma thesis deals with an effect of antimicrobial substances on raw food durability. Nowadays, the raw food has become very required style of nutrition, which is being practised by more and more people. The issue is that this kind of alimentation, especially vegetable raw food is not prepared in heat treatment which is higher than 42–45 °C. The main aim of the thesis is to study antioxidant and antibacterial properties of the herbal and spice extracts and their following implementation into raw desserts to prolong their durability. At the beginning of the theoretical part, there is an analysis of the issue of raw food and the description of micro-organisms, which are mostly occurred on plant materials. Afterwards, selected herbs and spices, and mechanisms of their antimicrobial effects, and also the methods used to test the products are characterised. The experimental part focuses on characterization of ethanol extracts from 13 selected kinds of spices and herbs. The determination of biologically active substance was accomplished, specifically, polyphenols, flavonoids, anthocyanins and their antioxidant properties. Moreover, these extracts were tested to antimicrobial effect towards gram-positive species of germs Micrococcus luteus, gram-negative species of germs Escherichia coli and yeast Candida glabrata. The molecular part of the thesis contains the DNA isolation from the tested raw material, which was enriched of combination of the selected herbs and spices. Change of expiry date of selected samples of raw desserts was monitored. The presence of chosen micro-organisms was confirmed by the PCR method.
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The negative effect of raw foods due to possible microbial contamination
Šťastná, Martina ; Hlaváček, Viliam (referee) ; Němcová, Andrea (advisor)
Raw diet is the current trend in nutrition, mainly because of the consumption of a balanced diet with a high proportion of health benefits. The basis is the consumption of fresh foods that have not undergone a heat treatment exceeding 42 - 45 ° C. The topic of the bachelor thesis is the general characterization of raw diet, safety of possible microbial contamination and determination of important nutrients and active substances contained in raw products. There are described the most widespread types of meals, approximation of raw diet in terms of its advantages and disadvantages. Also, there are described the most important bacteria, yeasts and molds occurring on fruits and vegetables. By selected methods described in the theoretical part, some nutrients and active ingredients in raw stick samples were determined. The experimental part describes the procedures and principles for the determination of these substances, and last but not least, the real-time PCR methods, agarose gel electrophoresis and the method of sample inoculation for selective solid media that have brought closer the possibility of occurrence of undesirable microorganisms in raw bars and cake. Despite the large number of benefits of raw food consumption and products made from it, it is necessary to take care of its health also in terms of possible contamination by microorganisms. The risk is that the food is not free from unwanted microorganisms during preparation. This is the reason why the raw products are consumed in the shortest possible time after opening, because they become easily a nutrition source for different types of microorganisms due to their composition.
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