Characterisation of Fractions Obtained by Isoamylolysis and Ion-exchange Chromatography of Cationic Waxy Maize Starch

Abstract

Despite the work carried out so far, a more detailed knowledge of the location of the substituents within the granules and distribution between the starch components would help to further improve and optimise the modification processes and to develop new products and applications of starch. Therefore, there is a continuous need for the development of analytical methods for the characterisation of modified starches. In what follows an ion-exchange chromatography method is described, by which the charged dextrins released by isoamylolysis of cationic starch can be isolated and further studied. Cationic starches, commonly substituted with a hydroxypropyl trimethylammonium group and widely used in the paper industry, can be produced by either a wet-cationisation [22] or a dry-cationisation method [23,24]. The samples under study in this work were wet-(WC) and drycationised (DC) waxy maize starch with a degree of substitution (DS) of 0.046 and were partly characterised previously [20]. Materials and Methods Starches and enzymesPreparation and characterisation of the wet-and drycationised waxy maize starches used has been described previously [20]. Both samples had a degree of substitution (DS) of 0.046. Isoamylase from Pseudomonas amyIsoamylase hydrolysates of wet-(WC) and dry-cationised (DC) waxy maize starch were fractionated by ion-exchange chromatography on CM-Sepharose into an unbound and four bound fractions. The amount of bound dextrins was higher in the WC than in the DC sample. The fractions were characterised by gel-permeation chromatography and proton-NMR spectroscopy. The unbound fraction from the WC sample consisted mainly of linear chains formed from amylopectin. The dextrins in the bound fractions contained increased amounts, from 1.2-7.9, of cationic substituents per molecule and the degree of polymerisation increased with the density of substituents. Dextrins weakly bound to CM-Sepharose had a linear structure, whereas more tightly bound fractions were mixtures of linear and branched dextrins. In the latter, the debranching was incomplete because of sterical hindrance by substituents at or close to the branch points. Most of the dextrins were partly hydrolysed by β-amylase, but the more highly substituted fractions possessed also a population of β-amylase resistant dextrins, suggesting substituents at the non-reducing ends.

Synthesis and characterization of synthetic polymer colloids colloidally stabilized by cationized starch oligomers

“…The efficiency of enzymes used for quantifying starch is known to be affected by the presence of synthetic polymer and of cationic substituents on the oligosaccharides. 50,53,56 Furthermore, the centrifugate containing the grafted species was not soluble in any common solvent. 8 Infrared could detect the starch and the synthetic polymer, but suffered from too limited a resolution to allow quantification.…”

“…49 When the glucose unit is substituted with hydroxypropyl-trimethyl-ammonium, the anomeric 1 H signal comes out at 5.58 ppm and the CH 3 signal of the substituent at 3.21 ppm. 50,51 Their respective signal areas are denoted as I (1!4)-a , I ared , I bred , I (1!6)-a , I sub , and I CH 3 . The number-average degree of polymerization of the debranched oligomers, X n , is then obtained from: 50…”

“…8 Although this is a well characterized reaction for native starch, it has been observed to be incomplete for cationized starch, as the presence of a cationic substituent close to the branching point affects the activity of the isoamylase enzyme. 50,53 The resulting oligomers have X n $ 34 glucose units, 1-2 charges per oligomers in average, and 7% probability of having a branching point. The enzymatic degradation by a-amylase does not significantly affect the DS or the DB, as expected for the random cleavage of (1!4)-a linkages.…”

Impact of reagent infiltration time on reaction patterns and pasting properties of modified maize and wheat starches

“…The predominant reaction of AP-LC and AM is likely explained by their location within starch granule amorphous regions, which are thought to be most accessible to reagent. Conversely, the lowest reactivities were observed for AP-MC and AP-SC, most likely due to their participation in the granule crystalline structure, making them less available for reaction (Chen, Huang, Suurs, Schols & Voragen, 2005;Kavitha & BeMiller, 1998;Manelius, Buléon, Nurmi & Bertoft, 2000;Manelius, Maaheimo, Nurmi & Bertoft, 2002;Richardson, Nilsson, Cohen, Momcilovic, Brinkmalm & Gorton, 2003;Steeneken, Tas, Woortman, Sanders, Mijland & de Weijs, 2008).…”

Amylose and amylopectin branch chain reactivity in a model derivatization system

“…For reactions conducted in the granular state, chains within amorphous regions are reported to be more available to modifying reagents and chemical modification than those of crystalline regions (Chen, Schols, & Voragen, 2004;Kuakpetoon & Wang, 2008;Manelius, Nurmi, & Bertoft, 2000b;Richardson et al, 2003;Tűting, Wegemann, & Mischnick, 2004). A greater degree of substitution (DS) or molar substitution (MS) has generally been observed for amylose (AM) as opposed to amylopectin (AP) (Chen et al, 2004;Huijbrechts et al, 2007;Kavitha & BeMiller, 1998;Shi & BeMiller, 2000 and for branching regions compared to linear regions of amylopectin molecules (Chen, Huang, Suurs, Schols, & Voragen, 2005;Kavitha & BeMiller, 1998;Manelius, Buléon, Nurmi, & Bertoft, 2000a;Manelius, Maaheimo, Nurmi, & Bertoft, 2002;Richardson et al, 2003;van der Burgt et al, 1998), implying that variations in starch granule structure do impact molecular reaction patterns of starch chains. Nevertheless, enzyme-or acid-assisted approaches to investigate starch reactivity on a molecular level require structural degradation of starch molecules, without retention of original starch chain identities and thus, provide only an indirect determination of molecular derivatization patterns.…”