Effect of annealing on the semicrystalline structure of normal and waxy corn starches

Physicochemical and morphological properties of starch from fresh waxy corn kernels

The characteristics on physicochemical and morphological properties of starches were investigated in fresh waxy corn kernels. Starches were isolated from eight waxy corn genotypes at the immature kernel stage growing in Thailand. The starch content showed variation with genotypes and ranged from 77.76 to 90.97 %. Granule size distribution showed a two population of starch granules with peak values ranged from 0.8 to 1.1 μm (small) and 9.0 to 12.2 μm (large). Genotypes were also significantly different for average chain length (CL), unit chain length distribution and pasting properties. The small granule (<5 μm) was negatively correlated with CL and degree of polymerization (DP) 25-36 of amylopectin (-0.82 and -0.67, respectively, P < 0.01). And a strong relationship between trough and final viscosity was consistent with the contribution of pasting properties.

Effects of heat treatment and moisture contents on interactions between lauric acid and starch granules

This study aimed to understand the effects of the moisture content of granular normal cornstarch (NC), heat treatment at 80 °C, and order of adding lauric acid (LA) to starch before or after the heat treatment on the physicochemical properties and digestibility of the starch. LA was added to NC priority heated with different moisture contents (10, 20, 30, 40, and 50%) or added to dried NC and then heated with different moisture contents. The hydrothermal/LA treatments increased the pasting temperature but decreased the peak viscosity of the NC. Light and scanning electron microscopy revealed that the addition of LA retarded gelatinization. The hydrothermal/LA treatments changed the X-ray pattern of the NC to a mixture of A- and V-type patterns. The thermal property and digestibility analysis showed that 40% was the optimum moisture content for the formation of the amylose-LA complex and adding LA prior to heating the NC favored the formation of slowly digestible starch.