Changing Wheat Bran Structural Properties by Extrusion-Cooking on a Pilot and Industrial Scale: A Comparative Study

Area of Science:

• Food Science and Technology
• Agricultural Science
• Materials Science

Background:

• Extrusion-cooking is a versatile thermomechanical process used to modify the techno-functional and nutritional properties of cereal by-products like wheat bran.
• Understanding the influence of extruder scale and processing conditions is crucial for optimizing wheat bran modification for various applications.

Purpose of the Study:

• To compare the effects of pilot-scale (BC21) versus industrial-scale (BC45) twin-screw extrusion-cooking on wheat bran properties.
• To investigate the impact of different extrusion types (single-pass, double-pass, acid extrusion) and process parameters (temperature, moisture) on wheat bran characteristics across scales.
• To determine the primary factors influencing wheat bran modification during extrusion-cooking.

Main Methods:

• Wheat bran was processed using pilot-scale (BC21) and industrial-scale (BC45) twin-screw extruders.
• Different extrusion methods including single-pass, double-pass, and acid extrusion-cooking were employed.
• Key process parameters such as temperature, moisture content, specific mechanical energy (SME), pressure, and product temperature were controlled and measured.
• Techno-functional properties like water-binding capacity, extract viscosity, and extractability were analyzed.

Main Results:

• Industrial-scale extrusion resulted in more significant wheat bran structure degradation, evidenced by higher water-binding capacity, extract viscosity, and extractability, compared to pilot-scale extrusion under similar settings.
• This enhanced degradation was linked to higher SME, pressure, and product temperature in the industrial extruder.
• Different extrusion types (single-pass, double-pass, acid) induced similar directional changes in physicochemical properties regardless of extruder scale, although differences were less pronounced on the industrial scale.
• Optimizing industrial-scale extrusion by reducing moisture and increasing product temperature enhanced its differentiating power, as confirmed with a BC72 extruder.

Conclusions:

• Extruder scale is the predominant factor determining the achievable specific mechanical energy (SME) and, consequently, the potential for modifying wheat bran.
• Industrial-scale extrusion offers a greater capacity for wheat bran structural modification compared to pilot-scale extrusion.
• Process parameter optimization, particularly moisture content and product temperature, can further enhance the effectiveness of industrial-scale extrusion for wheat bran modification.