Amylopectin Molecular Structure Reflected in Macromolecular Organization of Granular Starch

Abstract

For lintners with negligible amylose retrogradation, crystallinity related inversely to starch amylose content and, irrespective of starch source, incomplete removal of amorphous material was shown. The latter was more pronounced for B-type than for A-type starches. The two predominant lintner populations, with modal degrees of polymerization (DP) of 13-15 and 23-27, were best resolved for amylose-deficient and A-type starches. Results indicate a more specific hydrolysis of amorphous lamellae in such starches. Small-angle X-ray scattering showed a more intense 9-nm scattering peak for native amylose-deficient A-type starches than for their regular or B-type analogues. The experimental evidence indicates a lower contrasting density within the "crystalline" shells of the latter starches. A higher density in the amorphous lamellae, envisaged by the lamellar helical model, explains the relative acid resistance of linear amylopectin chains with DP > 20, observed in lintners of B-type starches. Because amylopectin chain length distributions were similar for regular and amylose-deficient starches of the same crystal type, we deduce that the more dense (and ordered) packing of double helices into lamellar structures in amylose-deficient starches is due to a different amylopectin branching pattern.

On the lamellar width distributions of starch

“…Normal maize, pinhão and waxy maize starches present the main peak position located at q = 0.64, 0.65 and 0.67 nm À1 , respectively. These values are in agreement with those published earlier (Calvert, 1997;Cameron & Donald, 1992;Jenkins et al, 1993;Vermeylen, Goderis, Reynaers, & Delcour, 2004). Surprisingly, the second starch reflection peak, indicated by the arrows in Fig.…”

“…In this work, an important advance on the lamellar starch organization is yielded since the second ordering peak is observed as a result of a careful processing of SAXS data. This surprisingly finding changed the most general view on starch SAXS patterns where a single and broad peak was interpreted as the unique evidence due to the lamellar organization of the granules (Cameron & Donald, 1992;Daniels & Donald, 2003;Thys et al, 2008;Vermeylen et al, 2004). This 'new' starch SAXS pattern containing two broad peaks is highly similar to those of semi-crystalline polymers where the paracrystalline lamellar order is observed (Choi, Vaidya, Han, Sota, & Hashimoto, 2003;Hama & Tashiro, 2003;Ivanov, Bar, Dosiere, & Koch, 2008;Bliznyuk et al, 2008).…”

Calcium bentonite as reinforcing nanofiller for thermoplastic starch

“…Figure 4 shows diffractograms obtained for granular regular starch, and for TPS samples. The well-known pattern, 27,28 described for the A-type crystallinity of granular corn starch may be visualized in trace I. No residual A-type crystallinity was detected for extruded TPS samples, as can be observed in trace II, for a sample analyzed without conditioning, 5 days after processing.…”

Fine Structure of Amylopectin

“…1.2). S-chains constitute the major group and have size distributions from DP 6 up to approximately DP 36 in most samples and a peak DP around 11-15, which depends on the sample (Koizumi et al 1991;Srichuwong et al 2005b;Vermeylen et al 2004;Bertoft et al 2008). L-chains possess normally a peak, or sometimes only a shoulder, around DP 43-50 (Fredriksson et al 1998;Hanashiro et al 2002;Bertoft et al 2008).…”

“…b Jenkins et al (1993) c Genkina et al (2007) d Kalinga et al (2013) e Vermeylen et al (2004) f Jenkins and Donald (1995) g Koroteeva et al (2007b) h Srichuwong et al (2005b) i Kozlov et al (2007a) defect with a lot of elongated granules (Banks and Greenwood 1973;Tester et al 2004;Kubo et al 2010;Jane et al 1994;Glaring et al 2006). The granules in waxy plants, however, are indistinguishable from those of normal amylose-containing granules (Fuwa et al 1978;Jane et al 1994;Song and Jane 2000).…”