Fructo-oligosaccharides and sucrose crystal growth morphology II. Verification of nonsucrose absorption through chromatographic analysis and x-ray diffractometry

In the first part of this study it was pointed out that sucrose microcrysta ls nucleated in the presence of a commercially mixture of fructo-oligosacch arides (Actilight(R)) showed a quite unusual triangular morphology, which, in turn, changed to a rhombic morphology during growth. With the aim of cla rifying how the Actilight(R) components. i.e. 1-kestose (GF2), nystose (GF3 ) and fructosyl-nystose (GF4), affected the growth morphology of the sucros e crystals, an investigation to determine their presence and distribution i nside the crystals was carried out. Both whole single crystals and samples cut from their right and left poles were analyzed using planar chromatograp hic techniques. GF2 and GF3 were found together with evidence of another do minant unknown oligosaccharide throughout the whole crystals, and these oli gosaccharides were more concentrated in the right poles. In fact, the same unknown oligosaccharide was identified as a minor component of Actilight(R) , even though its presence was not indicated by the manufacturers. This oli gosaccharide was later shown to be neo-kestose by means of NMR and GC-MS an alyses. The high concentration of neo-kestose with respect to other oligosa ccharides inside the Sucrose crystals, in spite of its negligible concentra tion in the growth solutions, supports the preferential incorporation of ne o-kestose into the sucrose crystal lattice. X-ray powder diffractograms of sucrose crystals grown in the presence of two different concentrations of A ctilight(R) also confirmed the incorporation of some of its components into the crystal lattice. This can be seen from the modification and splitting of several diffraction peaks, as they come out from the variation of the su crose unit cell parameters. In the light of these results, it is believed t hat neo-kestose may be the most efficient habit-modifier among the Actiligh t components, its power being comparable to that of raffinose.