Modulation of hen egg white protein techno-functionality by amyloid formation

Abstract

Hen egg white protein (EWP) is an ingredient in many food products. EWP containing amyloid-like fibrils (ALFs) can be prepared under food processing relevant conditions and have specific techno-functional properties which advantageously can be exploited in specific food products. Here, we investigated whether combinations of heating and NaCl addition or trypsin treatment improve EWP fibrillation and gel properties. Heating (75 °C, 150 min) control 0.2% EWP solutions resulted in limited fibrillation unless they also contained 150 mM NaCl, in which case increased levels of curly ALFs were observed. When similarly heated control EWP solutions were submitted to trypsin treatment (37 °C, 24 h, 150 rpm), both straight and curly ALFs were formed. Gels [5.0%–6.0% (w/v) EWP] prepared by heating (75 °C, 150 min) of 150 mM NaCl containing dispersions or by similar heating without NaCl addition but with trypsin treatment contained ALFs of similar morphology but shorter than those in control EWP solutions. Increased levels of curly or of both straight and curly ALFs in NaCl containing gels or gels prepared with trypsin treatment, respectively, resulted in higher EWP gel stiffness than when the EWP gels were prepared in water. While the presence of straight ALFs in trypsin-derived EWP gels resulted in fast gel breakdown, the presence of both curly and straight ALFs reduced the amount of EWP needed for gel formation. The level and morphology of EWP ALFs can thus be modulated by specific food relevant processing and the resultant ALFs have specific gelling properties.