Molecular size and mass distributions of native starches using complementary separation methods: Asymmetrical Flow Field Flow Fractionation (A4F) and Hydrodynamic and Size Exclusion Chromatography (HDC-SEC)

Abstract

Starch consists of a mixture of two α-glucans built mainly upon α-(1,4) linkages: amylose, an essentially linear polymer, and amylopectin, a branched polymer containing 5-6% of α-(1,6) linkages. The aim of the present work was to analyze the structural properties of native starches displaying different amylose-to-amylopectin ratios and arising from different botanical sources, using asymmetrical flow field flow fractionation (A4F) and a combination of hydrodynamic and size-exclusion chromatography (HDC-SEC) coupled with multiangle laser light scattering, online quasi-elastic light scattering, and differential refractive index techniques. The procedure, based upon dimethyl sulfoxide pretreatment and then solubilization in water, generates a representative injected sample without altering the initial degree of polymerization. The amylopectin weight-average molar masses and radii of gyration were around 1.0 × 10(8)-4.8 × 10(8) g mol(-1) and 110-267 nm, respectively. For each starch sample, the hydrodynamic radius (R(H)) distributions and the molar mass distributions obtained from the two fractionation systems coupled with light scattering techniques were analyzed. The size determination scales were extended by means of R(H) calibration curves. HDC-SEC and A4F data could be matched. However, A4F enabled a better separation of amylopectins and therefore an enhanced structural characterization of the starches. The two advantages of this experimental approach are (1) it can directly obtain distributions as a function of both molar mass and size, while taking account of sample heterogeneity, and (2) it is possible to compare the results obtained using the different techniques through the direct application of R(H) distributions.

Separation and characterization of food macromolecules using field-flow fractionation: A review

“…The results from the AF4-MALS analyses were compared to capillary viscometry and increases in apparent densities were reflected in increases in the overlap concentration, c*. Recently, several papers with results for various starches utilizing AF4 have been reported (Juna & Huber, 2012a, 2012b, 2012cJuna, Williams, & Davies, 2011;Perez et al, 2011) including an extensive study of natural starches (Wahlund, Leeman, & Santacruz, 2011) and a comparison between AF4 and hydrodynamic/size exclusion chromatography (HDC-SEC) (Rolland-Sabaté et al, 2011).…”

Interphase vs confinement in starch-clay bionanocomposites

“…Thus for starch, which tends to present very large radii of gyration of the order of 100 nm (Rolland-Sabate, Guilois, Jaillais, & Colonna, 2011;Wu, Twitt, & Gilbert, 2013), strong modifications of the macromolecular dynamics can be expected in nanocomposites. Consequently, we propose to study a model system composed of starch macromolecules and nanoparticles.…”

Development and evaluation of methods for starch dissolution using asymmetrical flow field-flow fractionation. Part II: Dissolution of amylose

“…Amylopectin is a highly branched molecule comprising a large number of short α(1→4)-linked glucose chains which are joined together by α(1→6) branch linkages (approximately 4-5 % α(1→6) linkages [1,2]). Amylopectin has a very high molar mass, M (approximately 10 6 <M <10 9 g/mol) [3][4][5][6][7]. Amylose is a linear molecule of α(1→4)-linked glucose units.…”

“…The technique minimizes or eliminates degradation and unwanted interaction [29] (i.e., low shear forces and small internal surface area). AF4 coupled with multi-angle light scattering (MALS) has already been applied successfully for M and root-meansquare radius (r rms ) determination of starches [5,7,15,16,30] (Table 1).…”