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

Abstract

We have investigated methods of starch dissolution with the aim of finding an optimum method to completely dissolve starch granules to form a molecularly dissolved starch solution without degradation of the polymers. Glycogen was used as a model molecule for amylopectin, to identify the dissolution conditions under which the degradation of the polymers was limited or not present. Dissolution was performed in water with temperatures up to 200 °C, facilitated by the use of heating in an autoclave or a microwave oven, or in dimethyl sulfoxide (DMSO) at 100 °C. Waxy maize starch was chosen due to its high content of amylopectin and very low content of amylose. The degree of starch dissolution under different conditions was determined enzymatically. The effect of different dissolution conditions on the molar mass and root-mean-square radius of the polymers was determined with asymmetrical flow field-flow fractionation coupled to multi-angle light scattering and differential refractive index (AF4-MALS-dRI) detectors under aqueous conditions. The results suggest that reliable and accurate size separation and characterization of amylopectin can be obtained by dissolution of starch granules in an aqueous environment at 140 °C by autoclaving or in DMSO at 100 °C. The results also clearly show an upper limit for heat treatment of starch, above which degradation cannot be avoided.

Understanding Starch Structure: Recent Progress

“…The size of amylopectin is much larger than amylose. Physicochemical techniques, such as light scattering, viscometry or ultracentrifugation, suggest the weight average molecular weight (Mw) to be in the order of 10 7 -10 8 Da [163][164][165][166][167], whereas number average values (Mn) are only 10 5 -10 6 Da [7,111,168,169]. The polydispersity index (Mw/Mn) is therefore very large [170].…”

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

“…In a recent paper, we reported on dissolving amylopectin from waxy maize starch, using either heating at elevated temperatures (autoclaving or microwave treatment in the temperature range 120 to 170°C) in aqueous environment or dissolution in DMSO at 100°C [3]. These methods have been applied previously to dissolve starch ( Table 1).…”

“…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.…”

Fluorescence-labelling for analysis of protein in starch using asymmetrical flow field-flow fractionation (AF4)

“…The sample solution was quantitatively diluted with water to 100 mL, and injected into the AF4 channel. 25 The sample injection volume was 50 μL.…”

“…[21][22][23] There have been some reports on application of FFF for analysis of starches. 24,25 Successful separations of AMY and AMP in four maize starches having various AMY content (0, 30, 50, and 70 %) have been reported using flow FFF (FlFFF) coupled with MALS-RI with a cross flow-programming. 26 FlFFF with a cross flow-programming also yielded successful separation of AMY from AMP in barley starch.…”