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Study of changes in the chemical composition of coffee during roasting
Kohoutová, Lenka ; Vítová, Eva (referee) ; Diviš, Pavel (advisor)
This bachelor thesis deals with monitoring of changes in acrylamide and hydroxymethylfurfural levels in coffee during the process of roasting. Green coffee was roasted using two separate roasting modes (medium roast: temperature 210 °C for duration of 14 minutes, City roast: temperature 220 °C for 17 minutes). Concentration of acrylamide and hydroxymethylfurfural for various roasting durations was determined by high performance liquid chromatography. For the determination of acrylamide, linear growth of the concentration was observed. The final levels of acrylamide corresponded with levels given by the literature, although the characteristic trend of acrylamide formation was not observed. Typical trend of hydroxymethylfurfural formation was observed in samples roasted with City roast mode, while the first part of the trend was also apparent in samples roasted with medium roast mode. Final levels of hydroxymethylfurfural in roasted coffee were within the limits given by the literature.
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Effect of roasting on the sensory profile of coffee
Šajdlerová, Kristýna ; Vítová, Eva (referee) ; Diviš, Pavel (advisor)
This bachelor thesis deals with the effect of roasting on the content of carbohydrates and aromatic compounds in coffee. It also studies changes in coffee acidity based on different level of roasting. In the practical part there was measured pH, it was conducted setting of glucose, fructose and sucrose content by liquid chromatography, analysis of aromatic compounds using gas chromatography and also sensoric analysis of 17 types of coffee. Each one was roasted using two different temperatures (210 °C and 240 °C). Based on the statistical processing of basic chemical analysis and sensory analysis, significant differences were found between determined parametres of coffee samples roasted at 210 ° C and 240 ° C. Processing of results of sensory and chemical analysis of coffee samples did not manage to differentiate coffee samples from each other based on their geographic origin. At a lower level of coffee roasting there was found weak, but statistically significant correlation between the results of the sensory analysis and the content of aromatic compounds, while for the higher degree of coffee roasting no correlation was found.
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Thermal biomass treatment
Křepela, Petr ; Šnajdárek, Ladislav (referee) ; Baláš, Marek (advisor)
The aim of this work is to provide an overview of biomass processing methods, description of final products and their practical application. Furthermore, a description of the technologies used for each method and the comparison of the efficiency. To achieve these goals, it is necessary to carry out a literature search and to produce a comprehensive set of meaningful information that is comprehensible to every reader, but does not hurt the professional public.
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Influence of selected coffee bean roasting technology on its chemical composition
Šajdlerová, Kristýna ; Mikulíková, Renata (referee) ; Diviš, Pavel (advisor)
The subject of this diploma thesis is the monitoring of chemical changes taking place in the coffee bean during roasting using various devices. For these purposes an industrial coffee roaster and a home roaster were used in the practical part. The theoretical part deals mainly with the characterization of coffee beans in terms of the content of various compounds and a description of the changes that occur during roasting. Different types of roasting machines are also presented. In the experimental part the roasting of coffee beans and the determination of the concentration of selected substances in the samples taken during roasting were performed. The monitored parameters included the concentration of sucrose, organic acids (citric, acetic, lactic, malic, formic and chlorogenic), caffeine and aromatic substances. One of the biggest differences found between the both roasters is the reduction in the concentration of chlorogenic acid, which decreased by 33 % for domestic equipment, while the decrease was almost doubled for industrial roasters. Another significant difference was also observed in the change in sucrose content. Sucrose degradation occurred in 94 % of coffee bean samples roasted on an industrial roaster, while only 75 % of the second type of roaster.
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Vliv způsobu zpracování larev potemníka brazilského na barevné a texturní vlastnosti produktu
Čaloudová, Jana
The thesis dealt with the processing of Zophobas morio larvae fed on different feeds by freeze- drying alone and in combination with roasting, with subsequent evaluation of the basic production parameters. The highest increases in length (17.1%) and weight (17.4%) of the individual were detected in the larvae of the control group (K). The highest increase in total weight (42.8%) was observed in group 1 fed fermented wheat bran. Freeze drying caused a decrease in weight of more than 60% in all groups, the water content was reduced to below 1.3% in all groups. Subsequent roasting of larvae did not cause a significant decrease in weight. The most significant decrease in larval length (22.9 %) after freeze-drying was detected in group 1; roasting had no effect. Furthermore, the colour properties of the samples were analysed, and their strength was determined. None of the treatments observed resulted in the production of excessively dark larvae. The differences between the groups studied in the colour parameter a* and b* were not statistically significant. The highest strength of the freeze-dried larvae was observed in group 1, which was freeze-dried only (2.35 N), there was no significant change in strength due to roasting. The technological treatments of edible insects affected the texture and colour of the product. Their correct choice and execution are important for the final product and its perception by consumers.
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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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Influence of selected coffee bean roasting technology on its chemical composition
Šajdlerová, Kristýna ; Mikulíková, Renata (referee) ; Diviš, Pavel (advisor)
The subject of this diploma thesis is the monitoring of chemical changes taking place in the coffee bean during roasting using various devices. For these purposes an industrial coffee roaster and a home roaster were used in the practical part. The theoretical part deals mainly with the characterization of coffee beans in terms of the content of various compounds and a description of the changes that occur during roasting. Different types of roasting machines are also presented. In the experimental part the roasting of coffee beans and the determination of the concentration of selected substances in the samples taken during roasting were performed. The monitored parameters included the concentration of sucrose, organic acids (citric, acetic, lactic, malic, formic and chlorogenic), caffeine and aromatic substances. One of the biggest differences found between the both roasters is the reduction in the concentration of chlorogenic acid, which decreased by 33 % for domestic equipment, while the decrease was almost doubled for industrial roasters. Another significant difference was also observed in the change in sucrose content. Sucrose degradation occurred in 94 % of coffee bean samples roasted on an industrial roaster, while only 75 % of the second type of roaster.
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Study of changes in the chemical composition of coffee during roasting
Kohoutová, Lenka ; Vítová, Eva (referee) ; Diviš, Pavel (advisor)
This bachelor thesis deals with monitoring of changes in acrylamide and hydroxymethylfurfural levels in coffee during the process of roasting. Green coffee was roasted using two separate roasting modes (medium roast: temperature 210 °C for duration of 14 minutes, City roast: temperature 220 °C for 17 minutes). Concentration of acrylamide and hydroxymethylfurfural for various roasting durations was determined by high performance liquid chromatography. For the determination of acrylamide, linear growth of the concentration was observed. The final levels of acrylamide corresponded with levels given by the literature, although the characteristic trend of acrylamide formation was not observed. Typical trend of hydroxymethylfurfural formation was observed in samples roasted with City roast mode, while the first part of the trend was also apparent in samples roasted with medium roast mode. Final levels of hydroxymethylfurfural in roasted coffee were within the limits given by the literature.
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Biologicky aktivní látky v kávě
Leshchuk, Liana
Bachelor thesis deals biologically active substances in coffee. The first part of work is include the history of coffee, the characteristics of coffee trees, the production of coffee from the step of the harvest to the roasting and other adjustments, the types of coffee according to the degree of roasting. The main theme of second part is the chemical composition of coffee beans. We look at biologically active substances in coffee, their content and influence on the human organism, which is the main theme of this work. And finally, following section deals undesirable substances in coffee, its formation during the processing of coffee beans and the effect on health.
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Antioxidační vlastnosti kávy
Lachmanová, Klára
This thesis deals with antioxidant properties of the coffee. It is focused on the influence of the roasting degree and different kinds of brewing methods on the antioxidant capacity of the coffee. A general overview is about the coffee itself, the history and coffee processing. Main part describes the roasting and chemical substances in the coffee. The whole roasting proces and chemical changes are described here as well. In practical part the antioxidant capacity is measured. The influence of individual factors is determineted by statistic methods. Brewing changes are evalueted by sensory analysis.
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