Fibrillization of whey proteins improves foaming capacity and foam stability at low protein concentrations

The Effect of High-Pressure Microfluidization Treatment on the Foaming Properties of Pea Albumin Aggregates

The effect of dynamic high-pressure treatment, also named microfluidization, on the surface properties of thermal pea albumin aggregates (AA) and their foaming ability was investigated at pH 3, 5, and 7. The solubility of albumin particles was not affected by the increase in microfluidization pressure from 70 to 130 MPa. Particle charge depended only on the pH, whereas protein surface hydrophobicity was stable at pH 5, decreased at pH 3, but increased at pH 7 after microfluidization treatment and with the applied pressure. Surface tension of AA measured at air/water interface was favorably affected by the microfluidization treatment at each pH preferentially due to size reduction and increased flexibility of protein particles. The foaming capacity and stability of AA depended on the pH conditions and the microfluidization treatment. The high-pressure treatment had little influence in foaming properties at acidic pHs, probably related to a more compact form of AA at these pHs. At neutral pH, the foaming properties of pea AA were strongly influenced by their surface properties and size associated with significant modifications in AA structure with microfluidization. Changes in albumin aggregate characteristics with pH and microfluidization pressure are also expected to modulate other techno-functional properties, such as emulsifying property. PRACTICAL APPLICATION: Albumins are known for their interesting nutritional values because they are rich in essential amino acids. This fraction is not currently marketed as a protein isolate for human consumption, but can be considered as a potential new vegetable protein ingredient. This document demonstrated that heat treatment or dynamic high-pressure technology can control the foaming properties of this protein for possible use in expanded foods.

Food protein amyloid fibrils: Origin, structure, formation, characterization, applications and health implications

Amyloid fibrils have traditionally been considered only as pathological aggregates in human neurodegenerative diseases, but it is increasingly becoming clear that the propensity to form amyloid fibrils is a generic property for all proteins, including food proteins. Differently from the pathological amyloid fibrils, those derived from food proteins can be used as advanced materials in biomedicine, tissue engineering, environmental science, nanotechnology, material science as well as in food science, owing to a combination of highly desirable feature such as extreme aspect ratios, outstanding stiffness and a broad availability of functional groups on their surfaces. In food science, protein fibrillization is progressively recognized as an appealing strategy to broaden and improve food protein functionality. This review article discusses the various classes of reported food protein amyloid fibrils and their formation conditions. It furthermore considers amyloid fibrils in a broad context, from their structural characterization to their forming mechanisms and ensued physical properties, emphasizing their applications in food-related fields. Finally, the biological fate and the potential toxicity mechanisms of food amyloid fibrils are discussed, and an experimental protocol for their health safety validation is proposed in the concluding part of the review.

Protein oxidation during temperature-induced amyloid aggregation of beta-lactoglobulin

Although the connection between protein oxidation, amyloid aggregation and diseases such as Alzheimer's is well known there is no information on such effects during preparation of beta-lactoglobulin fibrils. Different morphologies of amyloid aggregates of beta-lactoglobulin were prepared by incubation at pH 2 or pH 3.5 for up to 72 h. After 5 h, amyloid aggregates at pH 2 formed typical fibrils, which consisted of peptides. At pH 3.5, the amyloid aggregates were worm-like and consisted of intact protein. After 72 h, the building blocks at both pH values changed towards smaller peptides. The apparent tyrosine oxidation reached a maximum after 5 h at both pH values, whereas N-formylkynurenine and carbonyls increased continuously during 72 h. In case amyloid structures are used as edible material, the health related effects caused by protein oxidation needs to be considered.

A meal concept designed for older adults - Small, enriched meals including dessert

Background

The population of older adults is growing and many are at risk of disease-related malnutrition. This is a serious condition which increases the risk for other diseases and distress, human suffering and puts a high load on health care costs. Meal concepts tailored to suit the needs of older adults are required to decrease the incidence of disease-related malnutrition.

Objective

To evaluate sensory perception regarding a concept of small, protein and energy-enriched multi-component meals designed according to the nutritional needs of older adults.

Design

A meal concept of small main courses with complementary desserts and protein and energy-enriched products was evaluated using triangle tests, hedonic evaluation and focus group discussion. Enriched sauces and meals were compared to corresponding commercial products regarding appearance, taste, consistency and overall acceptance.

Results

The concept of a small main course with a complementary dessert was generally perceived as positive by the target group. The acceptance scores for the enriched meals were generally lower than for the commercial meals, mainly owing to the packaging of the enriched meals which required covering the food in sauce. Enriched sauces contained approximately 90% more protein than the commercial sauces. However, protein enrichment affected the sensory properties of the sauces and they were perceived as thicker, creamier and less flavour-intensive.

Conclusions

A concept based on small, protein and energy-enriched meals supplemented with a dessert was considered suitable for increasing the energy and protein intakes of older adults provided that the method of enrichment ensures attractive sensorial properties.

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

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.

Foams Stabilized by β-Lactoglobulin Amyloid Fibrils: Effect of pH

β-Lactoglobulin fibrils could serve as a surface-active component and form adsorption layers at the air/water interface. In this study, the physical parameters related to the surface adsorption, foaming, and surface properties of β-lactoglobulin fibrils as a function of pH (2-8) were investigated. Results showed that an increase of pH from 2 to 5 led to a rise of the viscoelastic modulus of the surface adsorption layer and half-life time (t_1/2) of foams, but it decreased foamability. When the pH was close to its isoelectric point (5.2), fibrils had the lowest electrostatic repulsion and entangled at the air/water interface resulting in a tightly packaged adsorption layer around bubbles to prevent coalescence and coarsening. When the pH (7-8) was higher than the pI of fibrils, the negatively charged β-lactoglobulin fibrils possessed good foamability (∼80%) and high foam stability (t_1/2 ≈ 8 h) simultaneously even at low concentration (1 mg/mL). It demonstrated that β-lactoglobulin fibrils with negative charges presented a good foaming behavior and could be a potential new foaming agent in the food industry.

Interfacial properties, thin film stability and foam stability of casein micelle dispersions

Foam stability of casein micelle dispersions (CMDs) strongly depends on aggregate size. To elucidate the underlying mechanism, the role of interfacial and thin film properties was investigated. CMDs were prepared at 4°C and 20°C, designated as CMD_4°C and CMD_20°C. At equal protein concentrations, foam stability of CMD_4°C (with casein micelle aggregates) was markedly higher than CMD_20°C (without aggregates). Although the elastic modulus of CMD_4°C was twice as that of CMD_20°C at 0.005Hz, the protein adsorbed amount was slightly higher for CMD_20°C than for CMD_4°C, which indicated a slight difference in interfacial composition of the air/water interface. Non-linear surface dilatational rheology showed minor differences between mechanical properties of air/water interfaces stabilized by two CMDs. These differences in interfacial properties could not explain the large difference in foam stability between two CMDs. Thin film analysis showed that films made with CMD_20°C drained to a more homogeneous film compared to films stabilized by CMD_4°C. Large casein micelle aggregates trapped in the thin film of CMD_4°C made the film more heterogeneous. The rupture time of thin films was significantly longer for CMD_4°C (>1h) than for CMD_20°C (<600s) at equal protein concentration. After homogenization, which broke down the aggregates, the thin films of CMD_4°C became much more homogeneous, and both the rupture time of thin films and foam stability decreased significantly. In conclusion, the increased stability of foam prepared with CMD_4°C appears to be the result of entrapment of casein micelle aggregates in the liquid films of the foam.

Contribution of Long Fibrils and Peptides to Surface and Foaming Behavior of Soy Protein Fibril System

When soy glycinin (11S) is heated for a prolonged time at pH 2 (20 h at 85 °C), a mixture is formed consisting of long semiflexible 11S fibrils and small peptides. The surface and foaming properties of this mixture were investigated at different pHs, and compared to the behavior of pure fibrils and pure peptides, to determine the individual contributions of these two factions to the behavior of the mixture. The adsorption of these three systems at air-water interfaces and the resulting surface rheological properties were studied by combining drop shape analysis tensiometry, ellipsometry, and surface large amplitude oscillatory dilatational (LAOD) rheology. Lissajous plots of surface pressure versus deformation were used to analyze the surface rheological response in terms of interfacial microstructure. Our results show that the adsorption kinetics, dilatational rheological properties, and the foaming behavior of the mixture were mainly dominated by the small peptides in the fibril system. Compared to pH 2, the fibril mixture at pH 5 and 7 provides much better foam stability and appears to be a very promising protein material to make stable foams, even at low protein concentration (0.1 wt %). The presence of fibril clusters and peptide aggregates at pH 5 and 7 contributed to foam stability of the mixture. In contrast, pure fibril formed an interface with a highly pH-responsive adsorption and rheological behavior, and the foamability and foam stability of the pure fibrils were very poor.

Role of pH-induced structural change in protein aggregation in foam fractionation of bovine serum albumin

For reducing protein aggregation in foam fractionation, the role of pH-induced structural change in the interface-induced protein aggregation was analyzed using bovine serum albumin (BSA) as a model protein. The results show that the decrease in pH from 7.0 to 3.0 gradually unfolded the BSA structure to increase the molecular size and the relative content of β-sheet and thus reduced the stability of BSA in the aqueous solution. At the isoelectric point (pH 4.7), BSA suffered the lowest level in protein aggregation induced by the gas-liquid interface. In the pH range from 7.0 to 4.7, most BSA aggregates were formed in the defoaming process while in the pH range from 4.7 to 3.0, the BSA aggregates were formed at the gas-liquid interface due to the unfolded BSA structure and they further aggregated to form insoluble ones in the desorption process.

A novel porous adhesion material with ink absorbency for digital inkjet printing

A novel porous adhesion material for digital inkjet printing with absorbency for eco-solvent ink has been successfully prepared.

Effect of high pressure microfluidization on the crystallization behavior of palm stearin - palm olein blends

Moderate and high microfluidization pressures (60 and 120 MPa) and different treatment times (once and twice) were used to investigate the effect of high-pressure microfluidization (HPM) treatment on the crystallization behavior and physical properties of binary mixtures of palm stearin (PS) and palm olein (PO). The polarized light microscopy (PLM), texture analyzer, X-ray diffraction (XRD) and differential scanning calorimetry (DSC) techniques were applied to analyze the changes in crystal network structure, hardness, polymorphism and thermal property of the control and treated blends. PLM results showed that HPM caused significant reductions in maximum crystal diameter in all treated blends, and thus led to changes in the crystal network structure, and finally caused higher hardness in than the control blends. The XRD study demonstrated that HPM altered crystalline polymorphism. The HPM-treated blends showed a predominance of the more stable β' form, which is of more interest for food applications, while the control blend had more α- and β-form. This result was further confirmed by DSC observations. These changes in crystallization behavior indicated that HPM treatment was more likely to modify the crystallization processes and nucleation mechanisms.

Glycation as a Tool To Probe the Mechanism of β-Lactoglobulin Nanofibril Self-Assembly

In this study we investigated the effects of different levels of glucosylation and lactosylation on β-Lg self-assembly into nanofibrils at 80 °C and pH 2. Fibrils in heated samples were detected with the thioflavin T assay and transmission electron microscopy, while SDS-PAGE was used to investigate the composition of the heated solutions and fibrils. Glycation had different effects in the nucleation and growth phases. The effect of glycation on the nucleation phase depended on the degree of glycation but not the sugar type, whereas both the type of sugar and the degree of glycation affected the rate of fibril growth. Glycation by either sugar strongly inhibited self-assembly in the growth phase, and lactosylation produced a much stronger effect than glucosylation. We suggest that the varying glycation susceptibility of different lysine residues can explain these observations. The large, polar sugar residues on the glycated fibrillogenic peptides may inhibit fibril assembly by imposing steric restrictions and disrupting hydrophobic interactions.