Effects of damaged starch on aging of wheat starch gels

BARRERA G; LEON AE; RIBOTTA PD

Santiago de Chike

Congreso; 2nd ICC Latin American Conference; 2011

ICC

Granular integrity of the starch can be affected by the mechanical action of the wheat milling process thus producing what is called damaged starch (Hoseney, 1994). Starch damage profoundly changes starch granular and polymer structures which influences rheological and functional properties (Faridi, 1990). Damaged starch has the ability to absorb more water than native granules, native wheat starch can absorb between 39% and 87% its weight in water, while damaged starch between 200% and 430% (Berton, et al 2002). The molecular interactions after cooling of the gelatinized starch have been called retrogradation. It is known that the starch retrogradation is controlled by the water present during aging; however, little evidence about the effect of damaged starch content on amylopectin retrogradation process has been published. The objective of this work was to evaluate the effect of damaged starch (DS) on the aging of wheat starch gels. Native wheat starch (Sigma Aldrich) was milled in a mill disk in order to cause a greater rupture of starch granules. Four samples, with 3.8, 8.4, 12.9 and 23.8% DS content were prepared mixing partially damaged wheat starch and native wheat starch. The kinetic of starch recrystallization was evaluated by differential scanning calorimetry (DSC) according to the Avrami model at different storage times (0, 2, 3, 6, 8, 10 and 15 days). The rate constants (k), that represent crystal growth, and the Avrami exponents (n), that describing the type of crystal growth, were obtained by fitting of retrogradation enthalpy experimental data. Texture properties of wheat starch gels were studied by texture profile analysis (TPA) at 0, 7 and 14 days. Gel hardness, springiness and chewiness were determined. Gel syneresis was evaluated at 0, 7 and 14 storage days. The results showed that retrogadation enthalpy (ΔHr) increased significantly by the increment of DS at all storage times. DS content affected significantly kinetics of amylopectin retrogradation, k and n for the starch samples were modified by DS content. The n values decreased and the k values increased by effect of DS. Therefore, DS has an effect on the nucleation process of starch recrystallisation and on the crystal growth rate. Starch gels hardness, springiness and chewiness at 0 and 7 days of storage were not influenced by DS. However, the increments of DS produced gels with lower hardness, springiness and chewiness at 14 days of storage. These texture profile parameters were significantly reduced by DS effects. Water separation of the gels decreased significantly with DS increments at 0 and 7 storage times, however, DS effect was not significant at 14 days. The decrease in syneresis could be attributed to changes in the characteristics of the pastes formed and to the characteristics of the interactions developed in the system.