ReviewFormation mechanisms, handling and digestibility of food protein nanofibrils
Introduction
Heat denaturation of proteins can form a wide variety of structures such as fibrils, flexible strands, branched structures and random aggregate (Bolder, Hendrickx, Sagis, & van der Linden, 2006) depending on the pH value, salt type and concentration, heating conditions and protein concentration (Nicolai, Britten, & Schmitt, 2011), among which, the greatest impact belongs to heat (Pearce, Mackintosh, & Gerrard, 2007). The pH value of protein solution is also of profound influence on the organizational arrangement of super-structures. The architecture and life span of these structures are determined by balance between attractive hydrophobic and repulsive electrostatic interactions. At low ionic strengths and at pH values far from the iso-electric point (pI), electrostatic repulsive forces overcome the attractive interactions resulting in formation of fibrillar structures with high aspect ratio (length versus diameter); whilst, at pH values close to pI, spherical microgels (with sub-micron diameters) and random aggregates are formed (Fig. 1) (Bolder, 2007, van der Linden, 2006, van der Linden and Venema, 2007). The stimulant-induced self-assembly of globular food proteins to fibrillar structures has received considerable attention owing to the ability of the fabricated structures to display novel profitable characteristics (van der Linden, 2006). In the assembly process, protein monomers are organized into giant supramolecules in which non-covalent interactions such as hydrogen bonds, and electrostatic, hydrophobic and van der Waals interactions hold the building units together (Bolder, 2007). Fibrils formation may involve covalent linkages (disulfide bridges) in addition to non-covalent interactions depending on pH. Heat treatment at pH 3.35 assembled fibrils not only by hydrogen bonds and hydrophobic interactions but also by limited number of disulfide bridges; whilst, by heating at pH 2.0 merely non-covalent hydrophobic interactions contributed in fibrils formation (Mudgal, Daubert, Clare, & Foegeding, 2010).
Section snippets
The essential characteristics of fibrils
Several types of food proteins such as milk proteins, soy proteins and egg white proteins can assemble in vitro at appropriate condition into fibrillar structures with micrometer length and nanometer thickness (Bolder, 2007, van der Linden, 2006). These objects resemble amyloid fibrils that are associated with neurodegenerative diseases like Alzheimer's, Parkinson's, Huntington's and Creutzfeldt–Jakob diseases. Accordingly they are often called “amyloid-like” (Jones & Mezzenga, 2012). The
Process overview
Beta-lactoglobulin is a globular whey protein with molecular mass of 18400 Da and radius of ∼2 nm (Bolder, Vasbinder, Sagis, & van der Linden, 2007). It exists in three genetic variants A, B and C which differ from each other at the subsititutions in their amino acid sequences. The variants A and B contain Gln at residue 59 while variant C contains His. As well, variant A contains respectively Asp and Val at residues 64 and 118 versus Gly and Ala in variants B and C (Dave, Loveday, Anema,
Post-formation processing and application of nanofibrils
Whey protein nanofibrils may undergo various post-formation processes including storage, high pressure treatment, sonication, drying and freezing. In the study of Bolder, Vasbinder, et al. (2007) post-formation behavior of protein fibrils as function of storage pH was investigated. The viscosity of the fibril sample stored overnight at pH 7.0 increased significantly and the sample stored overnight at pH 10.0 gelled. No remarkable change was however observed for the fibril solution stored at pH
Fibrils digestibility
Bateman, Ye, and Singh (2010) were the first investigators who carried out some work on protein fibrils digestibility. Incubation of β-lactoglobulin-originated fibrils by pepsin within a simulated gastric fluid caused complete digestion of the fibrils very quickly within 2 min. In addition to disintegration of the fibrils, peptides (2000–8000 Da) that build up the fibrils were digested to smaller peptides (<2000 Da). The high gastric digestibility of the fibrils-forming peptides was ascribed to
Concluding remarks and future trends
Whey proteins fibrils are artificially-synthesized analogues to neurodegenerative disease-related fibrils. Various attributes including the aspect ratio and length distribution indices impart the functionality of fibrils providing possibility to generate fibrils with characteristics of interest. The irreversibly formed fibrils have been exploited in preparation of cold-set hydrogels at considerably low concentrations. It has been extensively emphasized that the building units of the fibrils are
References (59)
- et al.
Properties of protein fibrils in whey protein isolate solutions: microstructure, flow behaviour and gelation
International Dairy Journal
(2008) - et al.
Heat-induced whey protein isolate fibrils: conversion, hydrolysis, and disulphide bond formation
International Dairy Journal
(2007) - et al.
Formation of nano-fibrils from the A, B and C variants of bovine β-lactoglobulin
International Dairy Journal
(2015) - et al.
The effect of limited proteolysis by different proteases on the formation of whey protein fibrils
Journal of Dairy Science
(2013) - et al.
Amyloid fibrils – self-assembling proteins
- et al.
Encapsulation systems based on ovalbumin fibrils and high methoxyl pectin
Food Hydrocolloids
(2011) - et al.
Self-assembly and aggregation of proteins
Current Opinion in Colloid & Interface Science
(2007) - et al.
Whey protein nanofibrils: kinetic, rheological and morphological effects of group IA and IIA cations
International Dairy Journal
(2012) - et al.
Tuning the properties of β-lactoglobulin nanofibrils with pH, NaCl and CaCl2
International Dairy Journal
(2010) - et al.
Self-similar assemblies of globular whey proteins at the air–water interface: effect of the structure
Journal of Colloid and Interface Science
(2010)
Inhibitory effects of β-ionone on amyloid fibril formation of β-lactoglobulin
International Journal of Biological Macromolecules
Formation of thermally induced aggregates of the soya globulin β-conglycinin
Biochimica et Biophysica Acta (BBA)-Protein Structure and Molecular Enzymology
Cold-set thickening mechanism of β-lactoglobulin at low pH: concentration effects
Food Hydrocolloids
Kinetic study of β-lactoglobulin thermal aggregation at low pH
Journal of Food Engineering
β-Lactoglobulin and WPI aggregates: formation, structure and applications
Food Hydrocolloids
Controlled food protein aggregation for new functionality
Current Opinion in Colloid & Interface Science
The effect of high pressure microfluidization on the structure and length distribution of whey protein fibrils
International Dairy Journal
Fibrillization of whey proteins improves foaming capacity and foam stability at low protein concentrations
Journal of Food Engineering
Heat-induced aggregation of β-lactoglobulin AB at pH 2.5 as influenced by ionic strength and protein concentration
International Dairy Journal
Agitation and high ionic strength induce amyloidogenesis of a folded PDZ domain in native conditions
Biophysical Journal
Improvement of heat-induced fibril assembly of soy β-conglycinin (7S Globulins) at pH 2.0 through electrostatic screening
Food Research International
Thiol compounds inhibit the formation of amyloid fibrils by β2-microglobulin at neutral pH
Journal of Molecular Biology
Recent development of peptide self-assembly
Progress in Natural Science
Morphology and persistence length of amyloid fibrils are correlated to peptide molecular structure
Journal of the American Chemical Society
Micrometer-sized fibrillar protein aggregates from soy glycinin and soy protein isolate
Journal of Agricultural and Food Chemistry
Enzyme-induced formation of β-lactoglobulin fibrils by AspN endoproteinase
Food Biophysics
Peptides are building blocks of heat-induced fibrillar protein aggregates of β-lactoglobulin formed at pH 2
Biomacromolecules
Strong impact of ionic strength on the kinetics of fibrilar aggregation of bovine β-lactoglobulin
Biomacromolecules
Multiple steps during the formation of β-lactoglobulin fibrils
Biomacromolecules
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Recent advances of interfacial and rheological property based techno-functionality of food protein amyloid fibrils
2022, Food HydrocolloidsCitation Excerpt :Protein amyloid fibrils (PAF) are grouped into pathological and functional types (Grigolato & Arosio, 2021; Onur, Yuca, Olmez, & Seker, 2018; Qiao et al., 2012). The functional PAF formed by assembling protein monomers or peptides into fibrillar structures, have gained increasing popularity for applications in food science due to their unique advantages, such as high aspect ratio (length versus diameter), tunable flexibility (Moayedzadeh, Madadlou, & Khosrowshahi asl, 2015), ordered alignment, and superior mechanical property (Schleeger et al., 2013; Xu et al., 2022). For instance, PAF with a high aspect ratio formed a space filling network at a low volume fraction, which was considered as pronouncedly promising candidate for utilization in weight-efficient structurants (Kroes-Nijboer, Venema, & Van Der Linden, 2012).