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    Item type:Publication, Access status: without files ,
    Quantitative studies on roast kinetics for bioactives in coffee
    (American Chemical Society (ACS), 2013-11-25)
    Lang, Robert
    ;
    Yagar, Erkan Firat
    ;
    Wahl, Anika
    ;
    Beusch, Anja
    ;
    Dunkel, Andreas
    Quantitative analysis of the bioactives trigonelline (1), N-methylpyridinium (2), caffeine (3), and caffeoylquinic acids (4) in a large set of roasted Arabica (total sample size n = 113) and Robusta coffees (total sample size n = 38) revealed that the concentrations of 1 and 4 significantly correlated with the roasting color (P less than 0.001, two tailed), whereas that of 2 significantly correlated inversely with the color (P less than 0.001, two tailed). As dark-roasted coffees were rich in N-methylpyridinium whereas light-roasted coffees were rich in trigonelline and caffeoylquinic acids, manufacturing of roast coffees rich in all four bioactives would therefore necessitate blending of two or even more coffees of different roasting colors. Additional experiments on the migration rates during coffee brewing showed that all four bioactives were nearly quantitatively extracted in the brew (more than 90%) when a water volume/coffee powder ratio of more than 16 was used.
    Publicationtype: Journal Article
      111
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    Item type:Publication, Access status: without files ,
    Extraction of methylxanthines from guaraná seeds, maté leaves, and cocoa beans using supercritical carbon dioxide and ethanol
    (American Chemical Society (ACS), 2002-07-17)
    Saldaña, Marleny Doris Aranda
    ;
    Zetzl, Carsten
    ;
    Mohamed, Rahoma Sadeg
    ;
    Brunner, Gerd
    New experimental data on the extraction of caffeine from guaraná seeds and maté tea leaves, and theobromine from cocoa beans, with supercritical CO2 were obtained using a high-pressure extraction apparatus. The effect of the addition of ethanol to carbon dioxide on the extraction efficiency was also investigated. Caffeine extraction yields of 98% of the initial caffeine content in both wet ground guaraná seeds and maté tea leaves were obtained. Extractions of caffeine from guaraná seeds and maté tea leaves also exhibited a retrograde behavior for the two temperatures considered in this work. In the removal of theobromine from cocoa beans, a much smaller extraction yield was obtained with longer extraction periods and consequently larger solvent requirements. The results of this study confirm the higher selectivity of CO2 for caffeine in comparison with that for theobromine, and also the influence of other components in each particular natural product on the extraction of methylxanthines. The effect of the addition of ethanol to carbon dioxide on the extraction of methylxanthines was significant, particularly in the extraction of theobromine from cocoa beans. In general, the use of ethanol results in lower solvent and energy requirements and thereby improved extraction efficiency.
    Publicationtype: Journal Article
    Scopus© Citations 95  37