Understanding foods as soft materials

Mezzenga, Raffaele; Schurtenberger, Peter; Burbidge, Adam; Michel, Martin

doi:10.1038/nmat1496

Cited by 616 publications

(510 citation statements)

References 97 publications

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“…Important progress has in particular been made by drawing analogies between food colloids and colloidal model systems, their interactions and the resulting phase behavior [1]. These issues are of central relevance to food science and technology and have already considerably improved our understanding of food materials.…”

Section: Introductionmentioning

confidence: 99%

Rheology and structural arrest of casein suspensions

Dahbi

Alexander

Trappe

et al. 2010

Journal of Colloid and Interface Science

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The rheology of milk powder suspensions is investigated up to very high concentrations, where structural arrest occurs. The main component of the milk powder investigated is casein, so that the suspensions can be regarded as casein suspensions. Four concentration regimes are identified. For effective casein volume fractions less than 0.54 the concentration dependence of the zero-shear viscosity is similar to that of hard-sphere suspensions. However, due to the elastic deformation of the caseins, the viscosity does not diverge at the hard sphere glass transition. In the volume-fraction range of 0.55-0.61 the viscosity exhibits a surprisingly weak dependence on concentration. The shape of the curve of the shear viscosity versus concentration deviates from hard sphere behavior in an unusual way, due to the observation of a region of almost constant viscosity. This concentration regime is followed by a regime where the viscosity steeply increases, eventually diverging at an effective volume fraction of 0.69. Frequency dependent rheology and diffusing wave spectroscopy measurements indicate that the suspensions are jammed for volume fractions above 0.69. Finally we found the concentration dependence of the relative zero-shear viscosity of casein suspensions to be very similar with the one of the micro-gels at volume fractions below 0.50 and above 0.55, which are know to shrink above a certain volume fraction, due to osmotic stress.

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Section: Introductionmentioning

confidence: 99%

Rheology and structural arrest of casein suspensions

Dahbi

Alexander

Trappe

et al. 2010

Journal of Colloid and Interface Science

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“…Furthermore, because the geometry is no longer axisymmetric, two area moments of inertia exist (corresponding to the bending modes with respect to the two main symmetry planes of the ribbon), scaling respectively as I ≈ r 0 . (nr 0 ) 3 and I ≈ (r 0 ) 3 . nr 0 .…”

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confidence: 99%

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confidence: 99%

“…nr 0 . Because the persistence length is proportional to the energy (in units of k B T ) needed to bend the fibril, it essentially reflects the lowest energy bending mode, that is, the one with the lowest area moment of inertia I ≈ (r 0 ) 3 . nr 0 , leading to a scaling behaviour of the persistence length of the form l p ≈ nr 0 4 E/k B T. Thus, for a multistranded helical fibril with twisting ribbon-like cross-section, both the scaling behaviour of the maximum height and the persistence length have a linear relationship with the number of filaments in the fibril, in perfect agreement with the results in Fig.…”

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confidence: 99%

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Understanding amyloid aggregation by statistical analysis of atomic force microscopy images

et al. 2010

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The aggregation of proteins is central to many aspects of daily life, including food processing, blood coagulation, eye cataract formation disease and prion-related neurodegenerative infections [1][2][3][4][5] . However, the physical mechanisms responsible for amyloidosis-the irreversible fibril formation of various proteins that is linked to disorders such as Alzheimer's, Creutzfeldt-Jakob and Huntington's diseases-have not yet been fully elucidated [6][7][8][9] . Here, we show that different stages of amyloid aggregation can be examined by performing a statistical polymer physics analysis of single-molecule atomic force microscopy images of heat-denatured b-lactoglobulin fibrils. The atomic force microscopy analysis, supported by theoretical arguments, reveals that the fibrils have a multistranded helical shape with twisted ribbon-like structures. Our results also indicate a possible general model for amyloid fibril assembly and illustrate the potential of this approach for investigating fibrillar systems.Protein self-assembly is a wide-ranging phenomenon and is of great importance in several areas of science. The reversible formation of fibrils from globular proteins is a phenomenon occurring naturally, in vivo, for proteins such as actin and tubulin 10,11 . Other well-known examples of protein fibrillation include the irreversible amyloid fibril formation of various proteins implicated in neurological disorders such as Alzheimer's, Creutzfeldt-Jakob or Huntington's diseases. Typically, these fibrils have long, unbranched, and often twisted structures that are a few nanometres in diameter 1,8 . 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] .Despite the fact that the individual parameters controlling the aggregation of globular proteins into amyloid fibrils have been well identified, the driving force for such an aggregation process still remains obscure. Studies devoted to the characterization of fibril structures based on light, neutrons and X-ray scattering methods, being bulk techniques, have only provided an average ensemble picture of the fibrils 23 . Single-molecule techniques such as atomic force microscopy (AFM) and transmission electron microscopy (TEM) have recently emerged to probe amyloid fibrils at the molecular level [24][25][26][27] . Nevertheless, so far, a fully comprehensive picture of the aggregation behaviour...

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“…In a previous study, we showed that the parameters obtained from a viscosity model for CM dispersions applied to sets of experimental data from the literature indicate that CM, at high concentrations, behave as soft spheres or microgels (Olivares et al 2013), as also suggested by Mezzenga et al (2005) and Dahbi et al (2010). Also, we showed that the pair interaction energy between CM can be directly obtained from a rheological parameter and it agrees satisfactorily with the values obtained with a previously proposed DLVO-like theory (Tuinier and de Kruif 2002).…”

Section: Introductionmentioning

confidence: 52%

Rheological behavior of concentrated skim milk dispersions as affected by physicochemical conditions: change in pH and CaCl2 addition

Olivares

Achkar

Zorrilla

2016

Dairy Sci. & Technol.

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Understanding the behavior of casein micelles (CM) in concentrated regimes is critical for the design of dairy unit operations such as drying or evaporation but also it is still scarce. In this work, the effect of the decrease in pH and the addition of a calcium salt on concentrated skim milk dispersions was examined by rheometric measurements at 25°C. Control samples (S1), samples with a pH of 5.8 (S2), and samples with 0.04 M CaCl 2 addition (S3) at different concentrations (40, 45, 48, 50, and 52% w/w) were analyzed through flow curves and oscillatory dynamic data by frequency sweep tests. All samples showed a clear shear thinning non-Newtonian behavior and a large dependence on concentration, dispersions being more fluid for samples S2 and S3. A viscosity model for microgels was used to obtain parameters related to the characteristic structure of systems. It was demonstrated that CM had a similar structure for the different physicochemical systems studied and that the decrease of pH and the addition of salt reduced the dispersion stability due to electrostatic and steric potential energy is depleted. Dynamic data showed that dispersions at the highest concentration had dominant and similar elastic behavior and weak gel character. A transition regime from fluid to gel was observed in samples S2 at 45% w/w. No samples obeyed the Cox-Merz rule. This study allowed gaining more understanding related to the structure of CM systems studied.

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Understanding foods as soft materials

Cited by 616 publications

References 97 publications

Rheology and structural arrest of casein suspensions

Rheology and structural arrest of casein suspensions

Understanding amyloid aggregation by statistical analysis of atomic force microscopy images

Rheological behavior of concentrated skim milk dispersions as affected by physicochemical conditions: change in pH and CaCl2 addition

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