Insight into multi-scale structural evolution during gelatinization process of normal and waxy maize starch

Area of Science:

• Food Science
• Materials Science
• Biochemistry

Background:

• Starch gelatinization is a critical process in food science.
• Maize starch exists in normal (NMS) and waxy (WMS) varieties with differing amylopectin content.
• Understanding structural changes during gelatinization informs food processing.

Purpose of the Study:

• To investigate the multi-scale structural evolution of NMS and WMS during gelatinization.
• To compare the distinct behaviors of NMS and WMS under controlled heating and freezing conditions.

Main Methods:

• Mimicked heating with ex-situ liquid nitrogen flash freezing.
• Scanning Electron Microscopy (SEM).
• X-ray Diffraction (XRD).
• Fourier Transform Infrared Spectroscopy (FTIR) and solid-state Nuclear Magnetic Resonance (NMR).
• Small Angle X-ray Scattering (SAXS).

Main Results:

• NMS granules developed cavities with increasing temperature; WMS granules lost integrity beyond (peak gelatinization temperature (Tp) + conclusion gelatinization temperature (Tc))/2.
• Relative crystallinity decreased in both NMS (32.8% to 15.26%) and WMS (42.43% to 13.09%), with a sharp decline in WMS.
• Short-range order loss was observed in both, while semicrystalline lamellae thinned in NMS and narrowed in WMS.

Conclusions:

• The destruction of amylopectin's double helix structure significantly impacts larger-scale starch structures.
• Distinct structural evolution pathways of NMS and WMS during gelatinization are confirmed.
• This research provides insights crucial for optimizing starch-based food processing.