Structure and rheological behavior of casein micelle suspensions during ultrafiltration process

Abstract

The stability and mechanism underlying the formation of deposits of casein micelles during ultrafiltration process were investigated by small-angle and ultra small-angle x-ray scattering (SAXS and USAXS). The casein micelle dispersions consisted of phospho-caseinate model powders and the measurements probed length scales ranging from 1 to 2000 nm. Rheometric and frontal filtration measurements were combined with SAXS to establish the relationship between the rheological behavior of deposits (shear and/or compression) and the corresponding microstructure. The results revealed two characteristic length scales for the equilibrium structure with radius of gyrations R(g), about 100 and 5.6 nm pertaining to the globular micelles and their non-globular internal structure, respectively. The SAXS measurements further indicated that the increase of temperature from 20 to 70 degrees C or the decrease of pH from 6.6 to 6 lead to agglomeration of the globular micelles. In situ scattering measurements showed that the decrease of permeation flows is directly related to the deformation and compression of the micelles in the immediate vicinity of the membrane.

Structural Study on Hen-egg Yolk High Density Lipoprotein (HDL) Granules

“…5. Each component is described in the model by a set of four parameters known from Guinier and power-law fits [40]. The fitted parameters are summarized in Table 2.…”

“…The fitted parameters are summarized in Table 2. As the most important output parameter of the model [40] we used the radius of gyration. At pH 6.5, we obtained a radius of gyration of R g1 =100 nm for the component at low q y and R g2 =3.6 nm for the component at high q y .…”

“…The scattering data contain two pronounced shoulders at q y =0.02 nm −1 and q y =0.2 nm −1 , respectively. We fitted the data using a unified exponential/power-law approach [40] which is suited to analyze small angle scattering of complex systems with a multilevel structure [41]. We assumed two structural levels resulting in two components indicated by dashed lines in Fig.…”

Digestibility and structural parameters of spray-dried casein clusters under simulated gastric conditions

“…The combination of small-angle X-ray scattering (SAXS) and ultra-small-angle X-ray scattering (USAXS) can be used to evaluate the structures of macromolecules since it provides information about clusters ranging from one to several thousand nanometers (Zhang & Ilavsky, 2010). Pignon et al (2004) analyzed casein micelles with SAXS and USAXS, and the results showed that casein micelles are bimodally distributed with two size length scales of around 100 nm for the globular micelles and 5.6 nm for the sub-micelles. Marchin, Putaux, Pignon, and Léonil (2007) also used these techniques to evaluate the effects of pH, temperature, and addition of ethylenediaminetetraacetic acid on the structure of casein micelles.…”

Investigation of surface modification of casein films by rennin enzyme action using micro-beam grazing incidence small angle X-ray scattering

“…Closely related to the heterogeneous nature is the lack of a crystal structure, so low-resolution methods like small angle scattering (SAS) [9,11,16,21], atomic force microscopy (AFM) [6,22] and electron microscopy (EM) [3] are applied in order to elucidate structural details. SAS data, obtained by scattering of X-rays or neutrons on a casein micelle suspension, reveal a multi-level structure, which is interpreted differently.…”