Formation of Amyloid-like Fibrils by Ovalbumin and Related Proteins under Conditions Relevant to Food Processing

Abstract

Protein aggregation is important in food processing, and this work investigated the aggregation of food proteins as a source of amyloid fibrils for use in bionanotechnology. Both purified and crude mixtures of albumin proteins were denatured by heat, which caused aggregation to occur. Protein denaturation was measured by using circular dichroism spectrometry and by following thioflavin T fluorescence, which is widely used as a diagnostic test for amyloid formation. There was a good correlation between the increase in thioflavin T fluorescence and loss of helical structure as the temperature was increased. Formation of thioflavin T fluorescence was dependent on temperature, but less dependent on salt and protein concentration. X-ray fiber diffraction patterns of denatured bovine serum albumin suggested that the protein had a similar cross-beta structure to that of amyloid fibrils. These results are consistent with the aggregates seen during food processing, being amyloid-like in nature.

Understanding amyloid aggregation by statistical analysis of atomic force microscopy images

“…However, many peptides and proteins, including many globular food proteins that are used as gelling agents, foaming agents or emulsifiers, can also form amyloid-like structures in vitro. Such structures can possess desirable mechanical properties and can be used to create useful textures and structures 12,13 .An example of a fibril formation of globular proteins is provided by the fine-stranded heat-set gels formed by heating solutions of various globular food proteins such as ovalbumin, bovine serum albumin 12 and b-lactoglobulin 13 . b-Lactoglobulin has been particularly well studied, because it represents both a relevant model system and a major whey protein of interest to the food industry [14][15][16][17][18][19][20][21][22] .…”

“…However, many peptides and proteins, including many globular food proteins that are used as gelling agents, foaming agents or emulsifiers, can also form amyloid-like structures in vitro. Such structures can possess desirable mechanical properties and can be used to create useful textures and structures 12,13 .…”

“…An example of a fibril formation of globular proteins is provided by the fine-stranded heat-set gels formed by heating solutions of various globular food proteins such as ovalbumin, bovine serum albumin 12 and b-lactoglobulin 13 . b-Lactoglobulin has been particularly well studied, because it represents both a relevant model system and a major whey protein of interest to the food industry [14][15][16][17][18][19][20][21][22] .…”

The Mechanism of Fibril Formation of a Non-inhibitory Serpin Ovalbumin Revealed by the Identification of Amyloidogenic Core Regions

“…In the absence of salt, OVA conformation exhibits a nearly reversible two-state heat-induced transition with a midpoint temperature of 76°C and reaches an almost completely unfolded state with a significant degree of secondary structure at 80°C (23). In the presence of salt, OVA undergoes irreversible heat denaturation with the formation of semiflexible fibrillar types of aggregates (23)(24)(25)(26)(27)(28). Unlike the other serpins, the aggregation mechanism of OVA has been suggested to resemble that of amyloid fibril formation (25,27).…”

“…In the presence of salt, OVA undergoes irreversible heat denaturation with the formation of semiflexible fibrillar types of aggregates (23)(24)(25)(26)(27)(28). Unlike the other serpins, the aggregation mechanism of OVA has been suggested to resemble that of amyloid fibril formation (25,27). The typical amyloid fibril possesses the cross-␤-structure (29), and the kinetics of fibril formation is often approximated to a nucleation-growth model, where the slow formation of the nucleus is the rate-limiting step of the reaction, followed by a rapid fibril extension step (30,31).…”