Chemical Characterization of Galactomannans and Arabinogalactans from Two Arabica Coffee Infusions As Affected by the Degree of Roast

Abstract

Galactomannans and arabinogalactans compose almost exclusively the polysaccharide fraction of roasted coffee infusions. To increase the knowledge about the effect of the degree of roast (DR) in the amount and chemical structure of the galactomannans and arabinogalactans, two arabica coffees of different geographical origins (Costa Rica and Brazil) were roasted for three degrees of roast (DRs 4.7-5.0, 8.7, and 10% of dry weight loss of green coffee beans, on a dry basis). The high molecular weight material was extracted with hot water and dialyzed (molecular weight cutoff >12 kDa), and the material was separated in three cold-water-soluble fractions by graded addition of ethanol. The degree of polymerization and the degree of branching of the galactomannans decreased with the increase of the DR. As the DR increased, less branched arabinogalactans were extracted. The relative amount of terminally linked arabinosyl residues of the arabinogalactans decreased with the increase in DR, and the terminally linked galactosyl residues increased. Also, the size of the arabinosyl side chains of the arabinogalactans decreased with the increase in DR.

Characterization of high molecular weight coffee fractions and their fermentation by human intestinal microbiota

“…Coldwater soluble fractions obtained from the light roasted coffee brew showed higher arabinogalactan/galactomannan ratios (1.4 -4.0) than cold-water soluble fractions from medium or dark roasted coffee infusions (0.5 -2.0 and 0.9 -1.3, respectively) ( Table 5). This is in agreement with results of Redgwell et al, who observed that the extractability of mannans is enhanced with increase in degree of roast [7,17]. Lower total Manp/4,6-Manp ratios were found in fractions obtained from light roasted coffee than from medium or dark roasted coffee (11.1 -20.1 a 17.4 -21.8 l 15.6 -22.6, Table 5), indicating that galactomannans extracted from light roasted coffee were more substituted.…”

“…Carbohydrate structural characteristics were determined by methylation analysis as described before [7,1]. In brief, dry samples were activated with powdered NaOH in dimethysulfoxide and methylated with CH 3 I.…”

Structure of arabinogalactan oligosaccharides derived from arabinogalactan-protein of Coffea arabica instant coffee powder

“…3). Its 1 H/ 13 These data confirmed the structure aAraf(1?3)bGal(1?6)Gal of 3 3 (Fig. 3, Tables 3 and 4).…”

“…5 Up to now, several investigations have been aimed at polysaccharides from green as well as from roasted coffee, and many of them have been focused to confirm and further elucidate arabinogalactans (AG) chemical structure and to explore their solution properties and biological activity. [5][6][7][8][9][10][11][12][13][14][15][16][17] It is now well known that AGs from green coffee beans exist as an extremely heterogeneous mixture of arabinogalactan-proteins (AGPs) containing between 6% and 10% glucuronic acid and 0.4-1.9% protein. 11 This heterogeneity mostly resides in both, the degree of branching (Gal/Ara ratio) and a monosaccharide composition of side chains.…”

Melanoidins from Coffee Infusions. Fractionation, Chemical Characterization, and Effect of the Degree of Roast

“…Uronic acids were determined colorimetrically according to a modification (31) of the method of Blumenkrantz and Asboe-Hansen (32). Methylation analysis was performed as described previously (22)(23)(24).…”