Author:

Abstract:

The most important food protein source is wheat with an average consumption of 16 g protein/capita/day. Wheat gluten (WG) is relatively abundant in wheat flour (ca. 12%) and cost-effective to isolate. Protein structure and functionality are inseparable. Altering the structure of proteins can impact their functionality and lead to new wheat-based applications. Amyloid protein fibrils (APF) are highly ordered nanofibers composed of cross β-strands stacked perpendicularly along the fibril axis, which are stabilized by intermolecular hydrogen bonds. They can exhibit enhanced techno-functionality (e.g. gelling and foaming capacity), which make them attractive in food applications. The aim of this research is to understand and optimize WG APF assembly under relevant food processing conditions. For this purpose, an I-optimal response surface design was used. WG was hydrolyzed with trypsin to a degree of hydrolysis (DH) 2 and DH 6. The hydrolysates were incubated at different temperatures (65 °C - 85 °C), pH values (5.0 - 7.0) and protein concentrations [0.5 - 2.0% (w/v)]. Using thioflavin T (ThT), the fluorescence was monitored over 60 h as an indicator of APF formation. After the incubation, a pellet was formed. In the soluble fraction, ThT fluorescence was similar for WG DH2 and DH6. The insoluble fraction was extracted (room temperature, 16 h, 150 rpm) with 0.05 M Tris/HCl buffer (pH 7.5) containing 50% (v/v) 1-propanol. Protein extractability was ca. 18% for both WG DH2 and DH6. However, ThT fluorescence was higher in WG DH6 (ca. 12%) extracted protein material than for WG DH2 (ca. 5%). Fourier transform infrared spectroscopy and transmission electron microscopy images indicated the presence of APF derived from WG DH6 prepared at optimal conditions [85 °C, pH 5.0, 1.8% (w/v) protein, 60 h]. These results indicate the potential of assembling wheat gluten into APF under food processing conditions.