Effect Of Annealing On The Properties Of Wheat Starch And Its Application

Annealing is a process of physical modification only by water and heat at a low cost and in an environmentally friendly way, it is unlikely that any chemical or biological modification will be allowed to introduce chemical reagents or alter gene. In this paper, wheat starch had been selected with a single-step annealing treatment to systematically analyze the effect of annealing on the granule morphology characteristic, crystallization properties, gelatinization characteristics, and some physical properties by a number of modern instruments, as well as the relationship and internal mechanism of properties and structure between native and annealed wheat starch. At the same time explored the impact of annealed wheat starch on noodle quality. The main conclusions are as follows:1. Annealing conditions were optimized according to the studied of the influence of different starch moisture content (40%to90%), annealing temperature (25℃to55℃) and annealing time (1to6d) on gelatinization temperature of wheat starch by Single factor and two-factor no repeat test by using Differential Scanning Calorimetry (DSC). The optimal conditions of the wheat starch were annealed at80%water content for3d at45℃Compared with native wheat starch, To, Tp and Tc annealed wheat starch increased6.44℃,4.4℃and2.74℃, respectively, ΔH has almost no change, and Tg was increased from80.47℃to82.18℃.DSC thermgrams showed that annealing leads to elevation of wheat starch gelatinization and sharpening of the gelatinization rang.2. The native wheat starch and the wheat starches annealed at45℃and55℃were observed by using Scanning Electron Microscope (SEM) and Laser Particle Size Analyzer (LPSA). The results showed surface of the annealed wheat starch granule produced various degrees of sags and breakage, and the average particle size of starch granule increased. Meanwhile, type A crystal of wheat starch was not changed after annealing by using X-ray diffractometer, but crystallinity degree increased from30.02%to30.56%. X-ray diffraction revealed that2°characteristic peak became apparent slightly after annealed, it stated that amylose-lipid complexes were optimized or formed after annealing.3. Macromolecules of the starch granule were reorganized physically by its liquidity increased after annealing by using XRD and DSC:this process was optimized or formed new amylose-lipid complexes, enhanced combining ability of double helix in crystalline region of the amylopectin, increased the integrality of crystal to lead to increase crystalline, but the quantity of double helix was not changed obviously.4. Amylose content, swelling power and solubility of the annealed wheat starch was less than that of native wheat starch, the transparency of starch paste was higher than native wheat starch. Determining the pasting texture properties of wheat starch by using texture analyzer, the results showed that the firmness and consistency of45AW (the wheat starch annealed at80%water content for3d at45℃) starch paste was1.333g and7.017gsec higher than that of NW (native wheat starch) starch paste, the cohesiveness and index of viscosity decreased by1.195g and11.409gsec.5. Adding the45AW starch to the flour for making noodles, its stretch ability, shear force and transparency which addition of5%and10%were all better than sample with no45W starch addition except colour and lustre.