Effect of oil on the rheological properties and reaction behavior of highly concentrated wheat gluten under conditions relevant to high moisture extrusion

Abstract

Understanding the rheological behavior of highly concentrated proteins is critical for the development of meat analogs. To enhance their sensory appeal, plant oil is often added during extrusion. The objective of this study was to gain a better understanding of how oil affects the rheological properties of gluten. Gluten doughs with different oil contents (0% to 6%) were prepared by adding emulsified and non-emulsified oil. Rheological measurements were performed under extrusion-relevant conditions using a closed cavity rheometer. In addition, the oil phase was visualized by CLSM imaging before and after rheological measurements. It was found that the complex modulus |G*| of the wheat gluten decreased with increasing oil concentration. When oil was added as emulsion, |G*| was significantly higher compared to when non-emulsified oil was added. The CLSM images revealed that the oil droplet size increased with increasing oil concentration. The doughs with emulsified oil had significantly smaller oil droplets. The results suggest that oil droplets act as fillers, weakening the protein matrix. By reducing the oil droplet size, this weakening effect could be reduced. Therefore, we concluded that the oil droplet size is a critical parameter influencing the rheological properties of oil-containing wheat gluten doughs under extrusion-relevant conditions.

Keywords

• Wheat gluten
• High moisture extrusion
• Meat analog
• Oil droplets
• Closed cavity rheometer
• CLSM