Investigation on Cracking Mechanisms of Dehydrated Corn: Multiscale Changes Driven by Temperature Gradient

Area of Science:

• Agricultural Engineering
• Food Science
• Materials Science

Background:

• Hot-air drying is crucial for corn preservation.
• Understanding drying-induced stress and microstructural changes is vital for quality control.
• Previous research has not fully elucidated the molecular mechanisms linking drying temperature to corn kernel integrity.

Purpose of the Study:

• To investigate the impact of hot-air drying temperature on corn kernel moisture migration, crack formation, and microstructural changes.
• To elucidate the relationship between drying temperature, internal moisture gradients, thermal stress, and crack development.
• To provide a molecular-level understanding of how drying affects cornstarch and protein structures.

Main Methods:

• Multi-scale characterization techniques including low-field nuclear magnetic resonance (LF-NMR), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR).
• Systematic variation of hot-air drying temperatures from 40°C to 80°C.
• Analysis of moisture migration, crack formation, and microstructural (starch granule morphology, protein secondary structure) evolution.

Main Results:

• Elevated drying temperatures accelerated moisture evaporation but increased internal moisture gradients, thermal stress, and crack formation.
• Optimal moisture migration and reduced cracking were observed at medium drying temperatures (60°C-70°C).
• Increasing temperature induced significant changes in cornstarch granule morphology and altered protein secondary structure from α-helix to random coil, increasing crack susceptibility.

Conclusions:

• Hot-air drying temperature significantly influences corn kernel microstructure and crack formation through moisture migration and thermal stress.
• Medium drying temperatures (60°C-70°C) are recommended for optimizing drying efficiency and minimizing structural damage.
• The study provides a molecular-level theoretical basis for optimizing corn drying processes to reduce processing losses.