A Kinetic Study of Ovalbumin Fibril Formation: The Importance of Fragmentation and End-Joining

et al. 2019

Both intrinsic and extrinsic factors impact amyloid formation of food proteins. We here review the impact of various conditions and food constituents on amyloid fibrillation of milk and legume proteins. Much less is known about casein and legume protein amyloid‐like fibril formation than about that of whey proteins such as β‐lactoglobulin, α‐lactalbumin, and bovine serum albumin. Proteins of both sources are often studied after heating under strong acidic (pH < 3) conditions. The latter induces changes in protein conformation and often peptide hydrolysis. At higher pH values, alcohols, chaotropic and/or reducing agents induce the conformational changes required to enhance fibrillation. Different types of food proteins can impact each other's fibrillation. Also, the presence of other food constituents can enhance or reduce it. No general conclusions on the mechanisms or impact of different food constituents on food proteins can be made. Optimal conditions for AF formation, that is, heating for several days at low pH, are rare in food processing. However, this does not exclude the possibility of AF formation in food products. For example, slow cooking of hydrolyzed proteins may enhance it. Future research should focus on the prevalence of AFs in complex food systems or model systems relevant for food processing.

Section: Introductionmentioning

confidence: 99%

Conditions Governing Food Protein Amyloid Fibril Formation. Part II: Milk and Legume Proteins

Lambrecht

et al. 2019

“…The initial growth phase was followed by (i) a second growth phase in which the ThT fluorescence still increased, but more slowly than in the initial growth phase and (ii) by a subsequent plateau phase with constant ThT fluorescence. A model for fibril formation that includes seeded linear growth, end‐joining, and fibril fragmentation shows that especially end‐joining (hence the formation of loops) impacts the growth of fibrils at neutral pH (Kalapothakis et al., ). Oxidation of SH groups has little—if any—impact on fibril formation as evidenced by ThT fluorescence (Jansens et al., ).…”

Section: Hen Egg Proteinsmentioning

confidence: 99%

Conditions Governing Food Protein Amyloid Fibril Formation—Part I: Egg and Cereal Proteins

Lambrecht

et al. 2019

Conditions including heating mode, time, temperature, pH, moisture and protein concentration, shear, and the presence of alcohols, chaotropic/reducing agents, enzymes, and/or salt influence amyloid fibril (AF) formation as they can affect the accessibility of amino acid sequences prone to aggregate. As some conditions applied on model protein resemble conditions in food processing unit operations, we here hypothesize that food processing can lead to formation of protein AFs with a compact cross β‐sheet structure. This paper reviews conditions and food constituents that affect amyloid fibrillation of egg and cereal proteins. While egg and cereal proteins often coexist in food products, their impact on each other's fibrillation remains unknown. Hen egg ovalbumin and lysozyme form AFs when subjected to moderate heating at acidic pH separately. AFs can also be formed at higher pH, especially in the presence of alcohols or chaotropic/reducing agents. Tryptic wheat gluten digests can form fibrillar structures at neutral pH and maize and rice proteins do so in aqueous ethanol or at acidic pH, respectively.

“…Finally, the protofibrils self‐assemble into much longer and stiffer mature fibrils (Hill et al., ). However, it is not always clear whether the same mechanism is involved when amyloid‐like aggregates are formed under other conditions (Kalapothakis et al., ).…”

Section: Amyloid Formation Of Food Proteinsmentioning

confidence: 99%

“…Sonication of preformed hen lysozyme fibrils into small particles and mixing a fraction thereof into a solution of fresh intact hen lysozyme allow immediate formation of second‐generation AFs under conditions which, without seeding, only result in AF after a lag phase of 11 days (pH 2.2 at 57 °C; Sasaki et al., ). Temperature‐dependent seeding has been reported for fibril formation of disulfide‐reduced ovalbumin at 50 °C and neutral pH even though also without seeding there was no apparent lag phase (Kalapothakis et al., ). Hamada and Dobson () showed that preformed β‐lactoglobulin fibrils eliminate the lag phase for fibril formation of disulfide‐reduced β‐lactoglobulin in 3.0 to 5.0 mol/L urea at 37 °C and pH 7.0.…”

Section: Seeding and Cross‐seeding Approaches To Tailor (Food) Protein mentioning

confidence: 99%

Rational Design of Amyloid‐Like Fibrillary Structures for Tailoring Food Protein Techno‐Functionality and Their Potential Health Implications

Grootaert

et al. 2018

115

To control and enhance protein functionality is a major challenge for food scientists. In this context, research on food protein fibril formation, especially amyloid fibril formation, holds much promise. We here first provide a concise overview of conditions, which affect amyloid formation in food proteins. Particular attention is directed towards amyloid core regions because these sequences promote ordered aggregation. Better understanding of this process will be key to tailor the fibril formation process. Especially seeding, that is, adding preformed protein fibrils to protein solutions to accelerate fibril formation holds promise to tailor aggregation and fibril techno‐functionality. Some studies have already indicated that food protein fibrillation indeed improves their techno‐functionality. However, much more research is necessary to establish whether protein fibrils are useful in complex food systems and whether and to what extent they resist food processing unit operations. In this review the effect of amyloid formation on gelation, interfacial properties, foaming, and emulsification is discussed. Despite their prevalent role as functional structures, amyloids also receive a lot of attention due to their association with protein deposition diseases, prompting us to thoroughly investigate the potential health impact of amyloid‐like aggregates in food. A literature review on the effect of the different stages of the human digestive process on amyloid toxicity leads us to conclude that food‐derived amyloid fibrils (even those with potential pathogenic properties) very likely have minimal impact on human health. Nevertheless, prior to wide‐spread application of the technology, it is highly advisable to further verify the lack of toxicity of food‐derived amyloid fibrils.