Solvent Effects on Starch Dissolution and Gelatinization

Abstract

The disruption of starch granular structure during dissolution in varying concentrations of N-methyl morpholine N-oxide (NMMO) has been studied using three maize starches with varying ratios of amylose and amylopectin. Behavior in NMMO has been characterized by differential scanning calorimetry (DSC), microscopy, rapid viscosity analysis (RVA), and rheometry. Exothermic transitions were observed for the three starches in both 78 and 70% NMMO; the transition changed to an endotherm at 60 and 50% NMMO. Consistent with DSC, hot stage microscopy showed that starch granules dissolved at NMMO concentrations of 78 and 70%, whereas in 60 and 50% NMMO, gelatinization behavior similar to that found for starch in water was observed. Mechanical spectroscopy revealed the dominant viscous behavior (G″ > G') of starch at NMMO concentrations of 70 and 78% and more elastic behavior (G' > G″) at lower concentrations. Starch solutions in 78% NMMO obey the Cox-Merz rule, suggesting that the solutions are homogeneous on a molecular level.

Effect of granule organisation on the behaviour of starches in the NMMO (N-methyl morpholine N-oxide) solvent system

“…When heating is continued in the hot stage, after 20 min at 95 • C, nearly all the granules disappear. This again indicated the process is kinetically controlled, as found for maize starch and reported in Koganti et al (2011).…”

“…Potato and tapioca starches, which do not contain any native lipids, exhibited higher enthalpies than cereal starches. All starches exhibited exotherms in 78% NMMO, which has been interpreted as a sign of strong polymer-solvent interaction and further dissolution of starch granules as explained in Koganti et al (2011). It can be seen that all starches had higher onset temperatures in 78% NMMO than in water.…”

“…The behaviour of maize starches in NMMO has been studied previously (Koganti, Mitchell, Ibbett, & Foster, 2011). In particular the structural changes occurring on heating in different concentrations of NMMO in water have been examined.…”

Loss of crystalline structure and swelling kinetics of maize starch and flour granules in glycerol excess: The role of the envelope structure

“…Starch gelatinization has been studied for a long time (Olkku and Rha, 1978;Donovan, 1979;Ratnayake and Jackson, 2006), essentially in water, but also more recently in other liquids, like glycerol , NMMO (Koganti et al, 2011(Koganti et al, , 2015 and ionic liquids (Liu and Budtova, 2013;Mateyawa et al, 2013Mateyawa et al, 2013. Different methods were used to characterize gelatinization kinetics and mechanisms, like differential scanning calorimetry (DSC), optical and electron microscopy, birefringence, wide angle X-ray diffraction, light scattering, viscosity measurements.…”

Understanding the role of water-ionic liquid mixtures on the gelatinization and dissolution of maize starches

“…It has been reported that small amounts of water can dramatically influence the liquid properties of ionic liquids, in particular the diffusion coefficient, viscosity, polarity and surface tension of ionic liquids (Kohno & Ohho, 2012 with G50 and G80. The gelatinization and swelling properties of starches are known to be influenced by the amylose and amylopectin ratio in the starch (Koganti, Mitchell, Ibbett & Foster, 2011). A series of investigation with maize starches containing varying amylose contents indicated that gelatinization temperatures increased with increasing amounts of amylose using the DSC.Without heat (at room temperature), only the low amylose starches are susceptible to gelatinization.…”