A process for preparing saccharide oligomers uses an aqueous feed composition that comprises at least one monosaccharide or linear saccharide oligomer, and has a solids concentration of at least about 70% by weight. The feed composition is heated to a temperature of at least about 40.degree. C., and is contacted with at least one catalyst that accelerates the rate of cleavage or formation of glucosyl bonds, such as enzyme or acid, for a time sufficient to cause formation of non-linear saccharide oligomers. A product composition is produced that contains a higher concentration of non-linear saccharide oligomers than linear saccharide oligomers.