Solubility Behavior of Granular Corn Starches in Methyl Sulfoxide (DMSO) as Measured by High Performance Size Exclusion Chromatography

Abstract

The extent of corn starch dispersibility and the relative molecular solubility of amylose and amylopectin in methyl sulfoxide (DMSO) were determined. Granular corn starches with <l, 25, 53, and 70% amylose were dispersed in 0–100% DMSO (in water) solutions at 30°C for 30 min. Maximum dispersibility for all starches (98%) was obtained when 90% DMSO/10% water was used; regular (normal) dent corn starch was equally dispersed in solutions with 88–94% DMSO. Molecular solubility, the presence of individual molecules of amylose and amylopectin, of starches was also measured (after centrifugation and filtration) by high performance size‐exclusion chromatography (HPSEC). Starches were dispersed in 90% DMSO and heated for 10 min at temperatures of 35–120ºC. At low temperatures, high coefficients of variation resulted from additional DMSO solubilization after treatment. At 120ºC, 70% amylose starch was >90% solubilized, while waxy starch was only 47% solubilized. When starches were treated for 18–89 h in 90ºC DMSO, solubility stopped increasing after 67 h. High amylose starch (70%) was mostly solubilized, but 53% amylose, waxy and regular starches could only be fully solubilized after exposure to shear. Amylopectin molecules appeared more susceptible to shear induced depolymerization than amylose. The percent amylopectin in the high amylose starches reflected that as determined by iodine binding analysis and the manufacturer; while the percent amylopectin in regular starch was too low (manufacturers: 75%, HPSEC: 65%). Undispersed components were mostly amylopectin. Since amylose is fully solubilized, however, the HPSEC can be used to quickly determine percent amylose in starch.

Rice Starch Diversity: Effects on Structural, Morphological, Thermal, and Physicochemical Properties—A Review

“…High temperatures and high pH increase the solubility of many cereal starches in aqueous solvents, but may result in molecular size reduction resulting from degradation, depolymerization, or oxidation (Yokoyama and others 1998). Dimethyl sulfoxide (DMSO) is the most frequently used polar aprotic solvent for SEC analysis (Jackson 1991).…”

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

“…Such conditions can however cause degradation of the starch polymers [3]. On the other hand, DMSO was reported to dissolve high-amylose starch varieties more completely than high amylopectin starches [23,46]. But in excess of heating and stirring, the dissolution in DMSO can also cause degradation of the starch [13].…”

RESEARCH PAPER Structural changes of corn starch during fuel ethanol production from corn flour

“…However, both the solvent and the solubilization method strongly affect the occurrence of a polysaccharide breakdown. Moreover, the most popular pullulan and dextran molecular weight standards are characterized by slightly different molecular structures and far lower molecular weights when compared to starch, so they can be recommended only for the assessment of the molecular weight of amylose (Lin et al, 2003;Chen et al, 2010;Braun 1993;Jackson, 1991). However, to answer the question regarding the susceptibility of the amylose and amylopectin fractions to amylolysis, knowledge of the absolute values of molecular weight is not essential, in contrast with information on the changes in both molecular weight and percentage of individual fractions.…”