Two-dimensional rotating-frame Overhauser spectroscopy (ROESY) and (13)C NMR study of the interactions between maltodextrin and an anionic surfactant.

Rotational frame nuclear Overhauser effect spectroscopy (ROESY) and (13)C NMR measurements were carried out to study the molecular interaction between maltodextrin, a digestive byproduct of starch, and an anionic surfactant. Significant differences in chemical shifts were observed when sodium dodecyl sulfate (SDS) was introduced into the maltodextrin (DE 10) solutions. (13)C NMR measurement indicated that there were downfield shifts and broadening of peaks, especially in the region of 75-81 and 100-103 ppm, which were assigned to carbons 1 and 4 of the d-glucopyranose residues of maltodextrin, respectively. ROESY spectra indicated cross-peaks between the SDS and maltodextrin protons. These peaks can arise only in the case of the designated SDS protons and maltodextrin protons being less than 0.5 nm apart for a substantial period of time. The most intense cross-peaks are those between the central CH(2) protons of SDS near 1.2 ppm and the maltodextrin protons ranging from 3.5 to 3.9 ppm. The SDS-H3 CH(2) protons were resolved from the bulk of the SDS protons, with peaks and shoulders at 1.25 ppm, which indicated an especially strong interaction of the SDS hydrophobic tail with MD6 and some less intense interactions with MD2, 4, and 5.

Effect of surfactant type on surfactant-maltodextrin interactions: isothermal titration calorimetry, surface tensiometry, and ultrasonic velocimetry study.

Isothermal titration calorimetry (ITC), surface tensiometry, and ultrasonic velocimetry were used to characterize surfactant-maltodextrin interactions in buffer solutions (pH 7.0, 10 mM NaCl, 20 mM Trizma base, 30.0 degrees C). Experiments were carried out using three surfactants with similar nonpolar tail groups (C12) but different charged headgroups: anionic (sodium dodecyl sulfate, SDS), cationic (dodecyl trimethylammonium bromide, DTAB), and nonionic (polyoxyethylene 23 lauryl ether, Brij35). All three surfactants bound to maltodextrin, with the binding characteristics depending on whether the surfactant headgroup was ionic or nonionic. The amounts of surfactant bound to 0.5% w/v maltodextrin (DE 5) at saturation were < 0.3 mM Brij35, approximately 1-1.6 mM SDS, and approximately 1.5 mM DTAB. ITC measurements indicated that surfactant binding to maltodextrin was exothermic. Surface tension measurements indicated that the DTAB-maltodextrin complex was more surface active than DTAB alone but that SDS- and Brij35- maltodextrin complexes were less surface active than the surfactants alone.

Effect of different dextrose equivalent of maltodextrin on the interactions with anionic surfactant in an isothermal titration calorimetry study.

Isothermal titration calorimetry (ITC) was used to study interactions between an anionic surfactant (sodium dodecyl sulfate, SDS) and maltodextrins with different dextrose equivalents (DE) in a buffer solution (pH 7.0, 10 mM NaCl, 20 mM Trizma, 30.0 degrees C). The interaction between SDS and maltodextrin was exothermic, which was attributed to incorporation of the hydrocarbon tail of the surfactant into a helical coil formed by the maltodextrin molecules. ITC measurements indicated that the number of SDS molecules bound per gram of maltodextrin increased with decreasing maltodextrin DE, i.e., increasing molecular weight. It was proposed that SDS only binds to maltodextrin molecules that have a DE greater than 10 glucose units.