Cell suspension culture studies of the Coffea arabica L.
Elizabeth J. Buckland
Cultured tissues derived from the coffee plant, Coffea arabica L., were grown in vitro in the form of both callus and suspension cultures. The suspension cultures grew rapidly and appeared healthy. Microscopic examination showed that the cells characteristically grew in long filamentous chains. Suspension cultures were examined for the presence of three components - free amino acids, caffeine and chlorogenic acid. By examining these components the species specificity could be determined. The free amino acids of the coffee bean are thought to be one of the major precursors of coffee aroma on roasting. The coffee suspension cultures were shown to contain a similar pattern of free amino acids although the total content was much higher in the cultures than in the intact green coffee bean. Aspartic acid, glutamic acid, phenylalanine, alanine, valine, threonine, serine, and glycine were the predominant amino acids present in the coffee suspension culture. Threonine, serine, glycine, alanine and phenylalanine were the major free amino acids in the green coffee bean. The free amino acid content in the suspension culture exhibited an initial rise, decreased during active growth, then increased rapidly to the maximum level during the decline of the culture. Roasted coffee bean extracts were investigated to ascertain whether one solvent could in preference extract some of the major precursors of coffee aroma. Methanol was found to extract material from green coffee beans which on roasting produced coffee aroma. Caffeine was detected in the cell suspension cultures. However, problems with the analytical methods gave rise to questionable results. The suspension cultures, at maximum caffeine yield, contained 0.03% caffeine (dry weight) whereas the green coffee bean contained considerably more caffeine (1.15%, dry weight). The caffeine content of the tissues increased during the lag phase, decreased during the rapid phase and then increased again in the stationary phase and ultimately production levelled off during the d [...]
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