Size exclusion chromatography with triple detection as well as infrared spectroscopy studies of commercially available pyrodextrins proved that these molecules are characterized not only by significantly lower molecular mass, in comparison to that of native starch, but also by increased branching. Therefore, pyrodextrins adopt a very compact structure in solution and show Newtonian behavior under shear in spite of their molecular masses of tens of thousands Daltons. The results also indicate that 50% reduction of digestibility of pyrodextrins is, to a minor extent, caused by formation of low-molecular color compounds containing carbonyl functional groups. The main reason is, as postulated in the literature, transglycosidation that leads to decreased occurrence of α-1,4-glycoside bonds in the molecular structure. In the process of dextrinization starch also undergoes changes in supermolecular structure, which, however, have no influence on digestibility. Likewise, the effect of formation of low-molecular colorful compounds containing carbonyl groups is not crucial.
Keywords: IR spectroscopy; gyration and hydrodynamic radius; molecular mass distribution; pyrodextrins; structure.
© 2016 Institute of Food Technologists®