Formation and properties of whey protein fibrils

Protein fibrils are threadlike aggregates that are about one molecule thick and more than thousand molecules long. Due to their threadlike structure they could potentially be used to form meat-like structures. Protein fibrils can be produced from milk protein and plant protein, opening opportunities for a more sustainable food production. For a successful application of the fibrils it is important to know how fibrils are formed and how to influence the properties of the fibrils. This thesis describes how fast fibrils are formed and determines the energy change involved in this formation. Fibrillar structures show promise as encapsulating material, thickener, gelling and flocculation agent. This thesis provides new insights that facilitate innovations in the area of tasty, healthy and sustainably produced food. </p

The Critical Aggregation Concentration of ß-Lactoglobulin-Based Fibril Formation

The critical aggregation concentration (CAC) for fibril formation of ß-lactoglobulin (ß-lg) at pH 2 was determined at 343, 353, 358, 363, and 383 K using a Thioflavin T assay and was approximately 0.16 wt%. The accuracy of the CAC was increased by measuring the conversion into fibrils at different stirring speeds. The corresponding binding energy per mol, as determined from the CAC, was 13 RT (~40 kJ mol¿1) for the measured temperature range. The fact that the CAC was independent of temperature within the experimental error indicates that the fibril formation of ß-lg at pH 2 and the measured temperature range is an entropy-driven process

The Influence of Concentration and Temperature on the Formation of γ-Oryzanol + β-Sitosterol Tubules in Edible Oil Organogels

The gelation process of mixtures of γ-oryzanol and sitosterol structurants in sunflower oil was studied using light scattering, rheology, and micro-scanning calorimetry (Micro-DSC). The relation between temperature and the critical aggregation concentration (CAC) of tubule formation of γ-oryzanol and sitosterol was determined using these techniques. The temperature dependence of the CAC was used to estimate the binding energy and enthalpic and entropic contribution to the tubular formation process. The binding energy calculated at the corresponding temperatures and CACs were relatively low, in order of 2 RT (4.5 kJ mol−1), which is in accord with the reversibility of the tubular formation process. The formation of the tubules was associated with negative (exothermic) enthalpy change (ΔH0) compared with positive entropy term (−T ΔS0 >0), indicating that the aggregation into tubules is an enthalpy-driven process. The oryzanol–sitosterol ratio affected the aggregation process; solutions with ratio of (60 oryzanol–40 sitosterol) started aggregation at higher temperature compared with other ratios

Fibrillar structures in food

Assembly of proteins or peptides into fibrils is an important subject of study in various research fields. In the field of food research, the protein fibrils are interesting candidates as functional ingredients. It is essential to understand the formation and properties of the fibrils for successful application of the fibrils in food products. This paper describes the impact of recent research on the general view of the process of fibril formation from [small beta]-lg and the properties of the fibrils that are formed, leading to better control of applications for the fibrils. There is a need for a better understanding of the behavior of fibrils in more complex food systems

Fibrillar structures in food

Assembly of proteins or peptides into fibrils is an important subject of study in various research fields. In the field of food research, the protein fibrils are interesting candidates as functional ingredients. It is essential to understand the formation and properties of the fibrils for successful application of the fibrils in food products. This paper describes the impact of recent research on the general view of the process of fibril formation from [small beta]-lg and the properties of the fibrils that are formed, leading to better control of applications for the fibrils. There is a need for a better understanding of the behavior of fibrils in more complex food systems

Fracture of Protein Fibrils As Induced by Elongational Flow

The length distribution of whey protein fibrils is important for application purposes. However, it is hard to influence the length distribution of whey protein fibrils during production. One way of influencing the length distribution of the mature fibrils is exposing them to an external field, like a flow field. In this research whey protein fibrils were exposed to elongational flow to fracture the fibrils. A simple experimental setup was used to establish a range of elongational strain rates. The length distribution of the fractured fibrils was determined using transmission electron microscopy and was shown to be controllable at relatively low strain rates.The length distribution of whey protein fibrils is important for application purposes. However, it is hard to influence the length distribution of whey protein fibrils during production. One way of influencing the length distribution of the mature fibrils is exposing them to an external field, like a flow field. In this research whey protein fibrils were exposed to elongational flow to fracture the fibrils. A simple experimental setup was used to establish a range of elongational strain rates. The length distribution of the fractured fibrils was determined using transmission electron microscopy and was shown to be controllable at relatively low strain rates

The Critical Aggregation Concentration of ß-Lactoglobulin-Based Fibril Formation

The critical aggregation concentration (CAC) for fibril formation of ß-lactoglobulin (ß-lg) at pH 2 was determined at 343, 353, 358, 363, and 383 K using a Thioflavin T assay and was approximately 0.16 wt%. The accuracy of the CAC was increased by measuring the conversion into fibrils at different stirring speeds. The corresponding binding energy per mol, as determined from the CAC, was 13 RT (~40 kJ mol¿1) for the measured temperature range. The fact that the CAC was independent of temperature within the experimental error indicates that the fibril formation of ß-lg at pH 2 and the measured temperature range is an entropy-driven process

Stability of colloidal dispersions in the presence of protein fibrils

We studied the stability of monodispersed polystyrene latex dispersions with protein fibrils at different concentrations at pH 2 using microscopy and diffusing wave spectroscopy. At low fibril concentrations, fibrils induced bridging flocculation due to the opposite charges between fibrils and the latex particles. At higher fibril concentration the dispersions were stabilized due to steric and/or electrostatic repulsion. Upon further increasing fibril concentration, we find that the dispersion is destabilized again by depletion interaction. At even higher fibril concentration, the dispersions are stabilized again. These dispersions have a higher stability compared to the dispersions without fibrils. Interestingly, these dispersions contain single particles and small clusters of particles that do not grow beyond a certain size. Although the stabilization mechanism is not clear yet, the results from microscopy and diffusing wave spectroscopy point in the direction of a kinetic barrier that depends on fibril concentration

Influence of Protein Hydrolysis on the Growth Kinetics of ß-lg Fibrils

Recently it was found that protein hydrolysis is an important step in the formation of ß-lactoglobulin fibrils at pH 2 and elevated temperatures. The objective of the present study was to further investigate the influence of hydrolysis on the kinetics of fibril formation. Both the hydrolysis of ß-lactoglobulin and the growth of the fibrils were followed as a function of time and temperature, using SDS polyacrylamide gel electrophoresis and a Thioflavin T fluorescence assay. As an essential extension to existing models, the quantification of the effect of the hydrolysis on the fibrillar growth was established by a simple polymerization model including a hydrolysis step