Structural determination of some new oligosaccharides and analysis of the branching pattern of isomaltooligosaccharides from beer.

Separation of the low molecular weight fraction of oligosaccharides from beer and subsequent NMR analysis led to the identification of several new derivatives of trehalose, sucrose, maltooligosaccharides glucosylated at O-2 of reducing end Glc, and linear Glc oligomers with alpha-(1-->3) and alpha-(1-->4)-linkages. Reducing oligosaccharides were labeled with 7-amino-4-methylcoumarin by reductive amination, separated according to their molecular weight and the branching pattern was studied using enzymatic (pullulanase) degradation in combination with MALDI-TOF mass spectrometry and HPLC analysis. It was found that up to DP 10 isomaltooligosaccharides mostly consisted of a linear reducing alpha-(1-->4)-linked Glc chain substituted by single maltose or maltotriose residue at O-6 of any residue except the reducing one.