Structure-function relationships of pearl millet nano-starches prepared by different methods

Area of Science:

• Food Science
• Materials Science
• Biotechnology

Background:

• Pearl millet is a vital cereal crop with significant starch content.
• Developing novel starch nanomaterials offers potential for diverse applications.
• Understanding the impact of different processing methods on starch structure is crucial.

Purpose of the Study:

• To develop starch nanocrystals (SNCs) and starch nanoparticles (SNPs) from two pearl millet varieties.
• To characterize and compare the properties of these nano-starches with native starch.
• To evaluate the influence of acid hydrolysis, ultrasonication, acid-assisted ultrasonication, and gamma irradiation on starch nanomaterials.

Main Methods:

• Starch nanocrystals (SNCs) and starch nanoparticles (SNPs) were synthesized using acid hydrolysis (AH), ultrasonication (US), acid-assisted ultrasonication (AHUS), and gamma irradiation (GI).
• Characterization included particle size, zeta potential, morphology (SEM), functional properties, thermal stability (DSC), structure (XRD), pasting (viscometry), and rheology.
• Two pearl millet varieties (HHB 67 and ProAgro 9444) were used as starting materials.

Main Results:

• Median particle size ranged from 100-200 nm with stable zeta potentials (-12 to -31.2 mV).
• AH and AHUS enhanced thermal stability and crystallinity (up to 37.47%), while US and GI reduced them.
• Pasting analysis revealed Type A behavior for native, US, and GI samples, and Type D for AH and AHUS samples, indicating restricted swelling.

Conclusions:

• The chosen method significantly influences the physical, chemical, and thermal properties of pearl millet starch nanomaterials.
• AH and AHUS methods are promising for producing thermally stable starch nanocrystals with higher crystallinity.
• US-SNPs exhibited unique weak gel-like behavior, suggesting potential for specific food applications.