Effects of Damaged Starch on Wheat Starch Properties

BARRERA G; LEON AE; RIBOTTA PD

Nantes

Congreso; I International Symposium on Towards a Sustainable Food Chain Food Process, Bioprocessing and Food Quality Management; 2011

CIGR

The objective of this paper was to evaluate the effects of the mechanical damage on the structural integrity and physicochemical properties of the starch granules, and the influence of damaged starch (DS) on the starch properties. Unmodified wheat starch was milled in a mill disk in order to cause a greater rupture of starch granules. Four samples, with 4, 8, 12 and 23 DS content were prepared mixing partially damaged wheat starch and native wheat starch. The structural changes of starch were observed using SEM and the X-ray diffraction properties was evaluated. Granular size distribution of starch samples was determined at time zero and after 3 hours of hydration by laser light scattering. Thermo-mechanic properties were evaluated by differential scanning calorimetry and visco analysis. The granular surfaces were eroded by effect of the milling and 23 DS sample showed a granule surface distorted, less uniform and irregular. X-ray peak intensities of samples slightly decreased with the level of DS. Relative crystallinity and total mass crystallinity grade of starch decreased with increasing content of damaged granules. The gradual increment of DS caused a displacement of the size distribution curves of hydrated granules toward higher diameters, an overlap of both populations of particles and a decreased of both peaks height of the distribution curves. The d50, d90, D3,2 and D4,3 values of starch samples were increased by DS content. However, d10 decreased. After 3 h of water/starch contact the peaks of both A and B granule populations decreased and the granular size in the four samples increased compared to that recorded at time zero. DS content affected all pasting parameters of the starch suspensions, the increment of damaged starch content produced slight increments on Initial pasting temperature PT and reductions on peak viscosity, hot paste viscosity, final or cool paste viscosity, breakdown and setback. The results indicated that DS content caused significant changes in the Flory–Huggins parameters increase in melting point of the pure polymer and the Flory–Huggins polymer–diluent interaction parameter (x1-2) and a decrease in ΔHu.