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The influence of coffee bean grinding and brewing method on the content of selected substances in a coffee cup
Dvořáčková, Sabina ; Vítová, Eva (referee) ; Diviš, Pavel (advisor)
This thesis deals with the influence of barista methods on the content of selected aromatic substances and caffeine in variously ground coffee. In the theoretical part, general information about the coffee plant, the chemical composition of the coffee bean, cultivation, post-harvest processing technology, including individually discussed barista preparation methods are presented. Furthermore, this part is devoted to the description of 10 selected volatile compounds that are part of the aromatic coffee profile, together with the characterisation of the xanthine alkaloid caffeine. The experimental part was filled with the analysis of 100% Arabica coffee samples that were prepared through a lever coffee machine, moka pot and Vacuum pot. These methods were used to prepare coffee samples that were ground to the finest, medium and coarse grinding grades as the effect of relative coffee particle size on the extraction efficiency of the studied compounds was investigated. Based on the results obtained, it was found that the highest caffeine concentrations were measured in espresso samples of medium ground coffee, which were extracted using a lever coffee machine and contained up to 110 mg of caffeine in 30 ml. Similar results were obtained for coffee samples made from the coarsest ground beans prepared using a moka pot, with caffeine concentrations averaging 176 mg per 50 ml of beverage. The most abundant volatile flavouring substance was furfuryl acetate. Its highest concentrations were recorded in the coarsest coffee samples from the vacuum pot, which proved to be the method with the best repeatability. Calculated values based on 1 kg of coffee identified 2-methylpyrazine as the most abundant volatile, which, like furfuryl acetate, was followed by high furfuryl alcohol.
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