Combinatorial effects of mechanical activation and chemical stimulation on the microwave assisted acetylation of corn (Zea mays) starch

Abstract

The changes in the physical characteristics of ball milled corn starch (BMS) after chemical modification were investigated. The SEM and XRD analysis of BMS granules showed a fragmented aspect with a total loss of their initial crystallinity and an increase of their potential hydroxyl substitution sites. This morphology facilitated the access of the esterifying solvents into the starch molecule as corroborated by the spectacular increase of the water solubility index (WSI) and water absorption index (WAI). Following the acetylation, the degree of substitution (DS) increased up to 2.83 with the augmentation of the iodine catalyst content (p = 0.011). However, under the same condition of esterification, the DS of the BMS was slightly lower in comparison to the control, due to an increase in the number of free hydroxyl groups. Consequently to the modification, a reduction in the Tg, strong hydrophobicity and important exo‐corrosion affecting the granules were noticed.

Cationic starch derivatives as reactive shale inhibitors for water‐based drilling fluids

“…XRD results for the partially hydrolyzed starch and the cationic starch derivatives (Figure ) show three well defined peaks for the starch at 15.1°, 17.3°, 19,1°, and 23.2° 2θ angles. The observed reflection angles are very close to the angles attributed to A‐type crystallinity of the starch . For the cationized derivatives, only one large peak with a lower intensity at 19.9° is observed in the same region, which confirms that the cationized derivatives have a lower degree of crystallinity than the hydrolyzed starch.…”

Molecular iodine in monomer and polymer designing

“…Xie et al [142,143] acetylated corn starch under microwave assistance (100 W) using acetic acid/acetic anhydride/I 2 system at 100°C. The degree of modification increased from 1.839 to 2.934 when iodine concentration was raised from 0.5 to 1.75 mM.…”

Properties of maize starch modified by ball milling in ethanol medium and low field NMR determination of the water molecular mobility in their gels

“…The X-ray diffraction pattern of native maize starch showed an A-type crystalline pattern illustrated by strong reflection at 2q of about 15 and 23 and an unresolved doublet at 17 and 18 (Diop et al, 2011). The crystalline region of native starch was calculated to be 20.32%, and is mainly characterized by the presence of branched amylopectin but also, the possibility of amylase was suggested, due to its helical structure to form some crystalline structure (Zhang et al, 2010).…”

“…5B). In this particular case, the effect of degree of structural degradation in starch granules as detailed above and enhanced by the milling time could be the main factor responsible for the mentioned variations (Diop et al, 2011).…”

“…The moisture migration has been shown to depend on the diffusion coefficient of water molecules, temperature, pressure, composition, geometrical factors, etc (Cornillon and Salim, 2000). Following the physical modification, the structure of starch granules was subjected to strong destruction, making external agents such as moisturizing agents freely accessible (Diop et al, 2011). Water mobility in starch suspension was observed to be lower for S/E 1:1 and 1:2 (w:v) at pasting temperature below 50 C, and its value increased for S/E 1:0 (w:v) and was more important for S/E 1:3 (w:v).…”