Effects of Humidification on Bran Layer Mechanics and Microstructure of Brown Rice: Mechanism and Optimization

Area of Science:

• Agricultural Engineering
• Food Science
• Materials Science

Background:

• Humidification conditioning is used in brown rice milling to enhance processing.
• The mechanisms behind humidification's effects on bran mechanical properties and microstructure are not fully understood.

Purpose of the Study:

• To investigate humidification's impact on brown rice bran mechanical properties and microstructure.
• To determine optimal conditioning parameters for improved milling performance.

Main Methods:

• Tensile testing, 3D surface profilometry, and scanning electron microscopy were used.
• A quadratic orthogonal rotatable composite design optimized conditioning parameters.

Main Results:

• Humidification reduces bran layer tensile strength and wear resistance.
• Moderate humidification (16% moisture) improves head rice yield (HRY) by weakening bran structure.
• Excessive humidification leads to kernel breakage.

Conclusions:

• Humidification alters bran layer microstructure and mechanical behavior.
• Optimal parameters (16% moisture, 30s humidification, 36min equilibration) maximize HRY and minimize energy use.
• Findings offer practical guidance for improving rice milling quality and energy efficiency.