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[摘要]：The roasting process induces structural changes in coffee galactomannans. To know more about the reaction pathways that occur during the roasting of coffee, mannosyl and galactomannosyl oligosaccharides, having a degree of polymerization (DP) between 3 and 4, were used as models for galactomannans. These compounds were dry-heated under air atmosphere from room temperature to 200 degrees C, being maintained at 200 degrees C for different periods of time. The roasted materials were analyzed by mass spectrometry (ESI-MS, MALDI-MS, and ESI-MS") and methylation analysis. In the MS spectra were identified several [M + Na](+) ions belonging to a series from a single hexose to 10 hexose residues ([Hex(1-10) + Na](+)). The ions corresponding, to their respective mono- and tridehydrated derivatives ([Hex(2-10) - H(2)O + Na](+) and [Hex(2-10) - 3H(2)O + Na](+), respectively) were also identified. ESI-MS" as well as deuterium-labeling and alditol derivatization experiments showed that the tridehydrations occur at the reducing end of the oligosaccharides. The identification of (1 -> 2)- and (1 -> 6)-linked mannose residues and (1 -> 4)-linked glucose residues by methylation analysis allowed the conclusion that transglycosylation and isomerization reactions occur during dry thermal processing. |
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