Effect of Shearing and Annealing on the Pasting Properties of Different Starches

Abstract

The functional characteristics of starch can be altered by shear force, which makes the impact on its microstructure of great importance to the food industry. This study investigated the effects of freeze-drying on the gel texture, pasting capabilities, and swelling power of starches made from sweet potatoes (SP), chickpeas (CP), and wheat (WS) combined with Cordia (CG) and Ziziphus gum (ZG). The samples were annealed in water without shearing and in a rapid visco-analyzer (RVA) for 30 min at 60 °C while being spun at 690 rpm. Both native and freeze-dried samples were mixed with 1% or 3% ZG and CG. After annealing, the starches were examined using a texture analyzer and RVA. The results showed that freeze-drying had a substantial (p > 0.05) impact on the starch granule, in addition to the effect of annealing. The peak viscosity of freeze-dried native CP and SP starches increased, but the peak viscosity of freeze-dried wheat starch decreased. The setbacks for CP and WS increased, whereas the setbacks for SP varied slightly. Furthermore, it was demonstrated that annealing in an RVA exhibited a substantially lower peak viscosity than annealing in a water bath; the RVA’s shearing effect may have been the cause of this difference. Cordia gum fared better than ZG in terms of peak viscosity, although ZG significantly reduced setback in comparison to CG. Among the various blends, the native WB sample had the lowest hardness (100 ± 4.9 g), while the freeze-dried WB SP sample had the greatest (175.5 ± 4.8 g). Shearing of starches broke up the granules into smaller pieces, which made them gel at lower temperatures. This could be a good thing when they are needed for food uses that require little cooking.

Keywords

• starch
• shearing
• pasting
• annealing