Enlarged processing window of plasticized wheat gluten using salicylic acid

Area of Science:

• Food Science and Technology
• Polymer Science
• Materials Science

Background:

• Wheat gluten is a valuable protein source for food and biomaterials.
• Extrusion processing of wheat gluten is limited by thermal degradation (scorch).
• Salicylic acid is known to inhibit radical reactions and potentially reduce scorch.

Purpose of the Study:

• To investigate the effect of salicylic acid on the extrusion processing of glycerol-plasticized wheat gluten.
• To determine if salicylic acid can widen the processing temperature window and improve extrudability.
• To elucidate the mechanism by which salicylic acid affects gluten processing.

Main Methods:

• Extrusion processing of wheat gluten with varying salicylic acid concentrations.
• Analysis of thermal properties using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).
• Rheological measurements (complex shear modulus) and mechanical testing (tensile tests).
• Spectroscopic analysis including size-exclusion high-performance liquid chromatography (SE-HPLC), chemiluminescence, and electron paramagnetic resonance (EPR) spectroscopy.

Main Results:

• Salicylic acid significantly increased the extrusion temperature window from 95°C to 135°C for 30 wt% glycerol-wheat gluten.
• Salicylic acid acted as a lubricant and viscosity reducer, attributed to reduced protein aggregation/cross-linking.
• EPR spectroscopy confirmed the radical scavenging activity of salicylic acid.
• Extrudates processed at higher temperatures with salicylic acid remained ductile, with slower aggregation/cross-linking rates.

Conclusions:

• Salicylic acid effectively retards scorch and widens the processing window for wheat gluten extrusion.
• The mechanism involves radical scavenging and reduction of protein aggregation, leading to improved processability and maintained material properties.
• This finding offers a viable method for enhancing the industrial application of wheat gluten-based materials.