Multi-scale structural changes of starch and proteins during pea flour extrusion

Area of Science:

• Food Science and Technology
• Biomaterials Engineering
• Protein Chemistry

Background:

• Dehulled yellow pea flour is a valuable ingredient with significant starch and protein content.
• Understanding the structural transformations of pea flour during extrusion is crucial for optimizing its functional properties.

Purpose of the Study:

• To investigate the effects of twin-screw extrusion processing on the structural characteristics of dehulled yellow pea flour.
• To determine how varying moisture content (MC), product temperature (T), and specific mechanical energy (SME) influence pea flour's physical and chemical properties.

Main Methods:

• Twin-screw extrusion processing of yellow pea flour at controlled MC, T, and SME.
• Analysis of structural changes using density measurements, X-ray diffraction (XRD), differential scanning calorimetry (DSC), and SE-HPLC for protein and starch solubility.
• Confocal Laser Scanning Microscopy (CSLM) for morphological analysis.

Main Results:

• Extrusion significantly reduced foam density with increasing SME and T.
• Starch remained amorphous, with its water solubility increasing up to 50%.
• Elevated temperatures and SME promoted the formation of protein networks, decreasing SDS-soluble proteins while increasing DTE-soluble proteins, indicating disulfide bond formation and larger protein aggregates.

Conclusions:

• Extrusion processing induces significant structural modifications in yellow pea flour, including starch gelatinization and protein denaturation/aggregation.
• The formation of a protein network and changes in composite morphology are key factors governing the expansion behavior of extruded pea flour.
• Sigmoid models effectively describe protein solubility changes, identifying critical temperature ranges for these transformations.