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Study of the spent coffee grounds addition on the physico-chemical properties of the soil
Kavková, Kateřina ; Pořízka, Jaromír (referee) ; Diviš, Pavel (advisor)
The aim of this thesis was to conduct a growth experiment of lettuce and corn in soil mixtures containing 2.5% modified (oxidized coffee grounds, defatted coffee grounds, oxidized defatted coffee grounds) or raw coffee grounds and compared these plants to plants that grew in clean soil without treatment. Both growth characteristics and chemical analyzes were studied - elemental analysis, amount of chlorophyll, etc. In germination tests, the effect of coffee grounds toxicity on seeds was demonstrated, except for the mixture with defatted grounds, when the maize seeds did so well in the leachate that they had sprouted leaves as in the mixture alone. The soil after the cultivation of lettuce and after the cultivation of maize was also analyzed and their values were compared with the soil before cultivation. Changes in pH, elemental composition, content of phenolic substances or content of organic matter were monitored.
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Monitoring process contaminants in coffee roasting using LC-MS
Ilyushchenkova, Alexandra ; Juglová, Zuzana (referee) ; Diviš, Pavel (advisor)
The bachelor thesis focuses on monitoring changes in the concentration of process contaminants during coffee roasting using liquid chromatography with mass detection. Green coffee was roasted at 220 °C for 14 minutes with two-minute intervals. Samples for analysis were taken from 10. by 24. minutes of roasting. Practical monitoring of the acrylamide’s formation during coffee roasting was not carried out, since it was not possible to detect acrylamide in coffee using a mass detector, even after its derivatization with thiosalicylic acid. The relevant data were taken from other scientific articles, which reported a linear increase in concentration with the roasting time up to the maximum value and a subsequent exponential decrease at the end of roasting. By monitoring 5-hydroxymethylfurfural, it was found that during roasting, this substance is gradually formed in coffee due to the decomposition of carbohydrates, however, with increasing roasting time, the degradation of this substance occurs quite quickly. The concentration of 5-hydroxymethylfurfural was also determined in coffee samples purchased in the trade network. Concentrations of 5-hydroxymethylfurfural in these samples ranged from 0,3 to 0,38 mg/kg, which are corresponded to those reported in other expert studies.
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Study of adsorption of organic pollutants on wheat bran biochar
Hanák, Jan ; Pořízka, Jaromír (referee) ; Diviš, Pavel (advisor)
This diploma thesis explores the application of the Diffusive Gradients in Thin Films (DGT) method for determining and monitoring the concentrations of dissolved pharmaceuticals and organic dyes in water and food. The theoretical part introduces the issue of the occurrence of these organic substances in water and food, the principles of the DGT method, the characteristics of adsorption and adsorption isotherms, and the introduction of biochar as an adsorbent. The experimental section primarily focuses on optimizing and validating adsorption gels containing commercial biochar and unmodified biochar from wheat bran for the adsorption of specific substances using the DGT method. Oxytetracycline was primarily tested from a selection of antibiotics and malachite green from organic dyes, which is widely used in aquaristics. The results demonstrate a comparison of the effectiveness of adsorption using these two types of adsorbents and their characteristics, such as infrared spectroscopy analysis or images from a scanning electron microscope. From the Langmuir isotherm, the maximum adsorption capacity for oxytetracycline on commercial biochar was found to be 314,065 mgg-1 and the maximum adsorption capacity for wheat bran biochar was 89,720 mgg-1. The maximum adsorption capacity of commercial biochar for malachite green was 439,406 mgg-1. The work further emphasizes the potential of the DGT method as a tool for food analysis and investigating contaminants in water systems, which further move into the food chain.
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Study of physio-chemical properties of high-protein baking mixtures
Damborská, Alexandra ; Diviš, Pavel (referee) ; Pořízka, Jaromír (advisor)
In terms of nutrition, proteins are an integral part of the diet. They have many functions in the human body, and their lack in the diet has a negative effect on human health. For now, the biggest source of protein is animal production. However, plant sources, which are also rich in protein content, are also starting to come to the fore. Pastries are among the most consumed foods in the world. By adding protein isolates, concentrates or hydrolyzates, you can increase the protein content of baked goods and, in addition, enrich its amino acid profile. The following proteins were selected for the preparation of high-protein bakery mixes - pea protein isolate, wheat bran protein concentrate, beef protein hydrolyzate, brown rice protein isolate, egg white protein isolate, whey protein isolate, soy protein isolate, gluten and hemp protein concentrate. The protein content of plain wheat flour was determined to be 11%. The mixtures were mixed so that the resulting protein content was 20%. The reference sample of plain wheat flour T530 and the high-protein mixture were analyzed to determine the chemical and mainly the rheological properties. From the rheological determinations, a farinographic and extensographic analysis of the formed doughs was performed. The determined parameters were processed by the principal component analysis method to compare the properties against the reference.
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Phloridzin content in selected apple varieties
Křehlíková, Jana ; Mikulíková, Renata (referee) ; Diviš, Pavel (advisor)
Phloridzin, a phenolic compound found in Malus genus, was targeted in this study for detection in apples and apple-based foods via HPLC. The research aimed to assess phlorizin’s potential as a marker for confirming apple presence in food, addressing food authenticity concerns. The methodology encompassed method optimization for sample preparation, considering solvent selection and oxygen impact on stability. Analysis revealed significant phloridzin distribution among apple varieties (Golden Delicious, Red Delicious, Granny Smith, Gala, Champion, Jonagold), averaging 17 ± 10 mgkg1. Further, 15 fruit products were surveyed for phloridzin content, with 5 non-apple-labelled foods also analysed. Phloridzin proved effective in detecting undeclared apple presence in jams, fillings, and fruit purees, highlighting potential for authenticity verification. However, fruit drinks and juices exhibited inconclusive results, suggesting a need for improved sample preparation and analysis methods.
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Study of the effect of adding coffee grounds to the soil on the growth of selected plants
Kopková, Pavlína ; Vítová, Eva (referee) ; Diviš, Pavel (advisor)
Due to the globally high consumption of coffee, a large amount of spent coffee grounds is generated. This study aims to evaluate the potential use of this waste material in agriculture as fertiliser for field crops. Growth experiments were conducted with brown soil enriched with 2.5 vol.% of coffee grounds or modified coffee grounds, followed by soil and lettuce (Lactuca sativa L.) and corn (Zea mays) plant characterisation. Although germination tests did not demonstrate phytotoxicity of the soil mixtures, the addition of any modified coffee grounds led to a decrease in plant biomass. Differences between lettuce and corn were observed during growth. After harvesting, a decreased chlorophyll content or mineral substances was found in the cultivated plants. Prepared soil mixtures affected soil pH, with the greatest pH decrease measured after the addition of oxidized coffee grounds. Elemental analysis of the soils before cultivation showed an increase in the content of some essential mineral elements for plants (K, Ca, Na, Mg), but at the same time, there was a decrease in the concentration of one of the most important elements, phosphorus (P).
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Optimizing the production of non-chocolate sweets with the addition of Filipendula ulmaria extract using various sweeteners
Malyszová, Markéta ; Diviš, Pavel (referee) ; Vítová, Eva (advisor)
The aim of this master's thesis was to optimize the production process of jelly candies using various alternative sweeteners and subsequently adding herbal extract of meadowsweet, achieving not only better nutritional properties but also enhanced sensory characteristics of the final product. Sensory analysis was utilized to determine the ideal combination of sweetener type and amount, which most closely aligns with consumer preferences for sweetness and texture, while maintaining a low energy component content. Based on these criteria, maltitol was selected as the sweetener in a 50% w/w solution. The study also focused on optimizing the addition of Filipendula ulmaria extract to the candies made with the "ideal" sweetener. Again, using sensory analysis, the optimal concentration of the extract and the type of gelling agent were selected to achieve the desired consistency, taste, and other sensory parameters that make the product attractive for consumers. Following these experiments, the ideal values were determined to be 50% w/w for sweetener, a 5 % addition of Filipendula ulmaria extract, and the use of gelatin as the gelling agent. Subsequently, a chemical analysis of the produced samples and meadowsweet extract was also carried out. Identification and quantification of volatile aromatic compounds were performed using the HS SPME GC-MS method, which identified 39 different substances, predominantly from the group of alcohols and aldehydes. To determine the total content of phenolic compounds, the Folin-Ciocalteu spectrophotometric method was used, and the pH differential method was employed to determine the content of anthocyanins. The total content of phenolic compounds in the extract amounted to 1418.16 ± 6.56 gml-1, and the total anthocyanin content was determined to be 249.19 ± 27.40 gml-1. Antioxidant activity was tested using two methods, TEAC and DPPH. The results of the antioxidant activity measured by the DPPH method were higher, confirming the greater robustness of this method. However, both tests confirmed the antioxidant activity of the tested samples. Finally, the antimicrobial activity of the samples was tested using the diffusion well method against strains of Bacillus cereus and Escherichia coli. The samples exhibited antimicrobial activity against both tested microorganisms, but showed more effective action against Bacillus cereus, which may be due to the simpler structure of their cell wall.
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Production and characterization of protein isolates from different kinds of bran
Vybíral, Lukáš ; Diviš, Pavel (referee) ; Pořízka, Jaromír (advisor)
This diploma thesis deals with the use of various types of bran as a by-product in the milling of cereals. Mills create a huge amount of this material per year. The most common way of processing bran is mostly incineration and to a lesser extent it is used as feed for livestock. Depending on the type of cereal, bran contains 10-20% of protein, which disappears from the food chain due to combustion. Within the framework of sustainability and valorisation of waste, which has recently been largely discussed, great emphasis is placed on waste minimization whether in the field of its production or further processing. Due to the relatively high protein content, bran appears to be a suitable starting material to produce protein supplements. Proteins can be extracted from bran based on their different solubility at different pH. In the alkaline method, the proteins are first dissolved in an alkaline pH and then precipitated in an acidic medium. Lyophilization is followed by characterization of the extract in terms of yield, protein content, moisture, amino acid profile and digestibility. The highest yield was obtained with the oat bran isolate (13,5 ± 0,6 g of isolate per 100 g of bran). In terms of protein content, the best protein isolate was also obtained from oat bran (95,2 ± 0,4% protein in the isolate). Another determination was the analysis of the amino acid profile, in which a high content of arginine was found in all analyzed protein isolates from bran. Determination of digestibility showed very good digestibility of all produced protein extracts from bran.
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Determination of mercury in selected fish species and in fish products
Kroupová, Kateřina ; Ing.Tomáš Gregor, Ph.D. (referee) ; Diviš, Pavel (advisor)
Theoretical part of the master thesis deals with the occurrence of different mercury species in the environment and describes analytical methods used for determination of mercury in biological samples. In practical part of the master thesis mercury concentration in 14 samples of selected fish and fish product was determined using single purpose absorption spectrometer AMA 254. Measured results were statistically processed and consulted with EU legislative norm.
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