TY - JOUR

T1 - Tunable mixed micellization of β-casein in the presence of κ-casein

AU - Wijaya, Wahyu

AU - Khan, Sanaullah

AU - Madsen, Mikkel

AU - Møller, Marie Sofie

AU - Maria Rovers, Tijs Albert

AU - Jæger, Tanja Christine

AU - Ipsen, Richard

AU - Westh, Peter

AU - Svensson, Birte

PY - 2021

Y1 - 2021

N2 - Casein-casein interactions can be very useful for tuning structural and physical properties of mixed casein micelles for food and biotechnology applications, particularly in the dairy industry. The present work focuses on the structures of mixed micelles formed by stepwise addition of a micellar β-casein solution to either 0.05 or 0.3 mM κ-casein, i.e. below or above the critical micellar concentration (CMC) of κ-casein, respectively. Insight into the thermodynamics of this mixed micellization was achieved using isothermal titration calorimetry (ITC), which indicated a less favorable enthalpy of formation and a downward shift of the CMC of mixed micelles with 0.3 mM κ-casein. Hydrophobic interactions are the main driving force behind the mixed micellization as probed by using pyrene, a hydrophobic fluorophore. Structural characterization by dynamic light scattering (DLS) and small angle X-ray scattering (SAXS) revealed that addition of micellar β-casein to 0.05 mM κ-casein oligomers caused strong perturbation and formation of smaller micelles compared to when added to 0.3 mM κ-casein in micellar state. Thus, association of β-casein with κ-casein in these two different physical forms of loosely interacting oligomers and micelles, respectively, can modulate formation of mixed micelles with regard to structural properties such as shape, size and molecular packing (compactness).

AB - Casein-casein interactions can be very useful for tuning structural and physical properties of mixed casein micelles for food and biotechnology applications, particularly in the dairy industry. The present work focuses on the structures of mixed micelles formed by stepwise addition of a micellar β-casein solution to either 0.05 or 0.3 mM κ-casein, i.e. below or above the critical micellar concentration (CMC) of κ-casein, respectively. Insight into the thermodynamics of this mixed micellization was achieved using isothermal titration calorimetry (ITC), which indicated a less favorable enthalpy of formation and a downward shift of the CMC of mixed micelles with 0.3 mM κ-casein. Hydrophobic interactions are the main driving force behind the mixed micellization as probed by using pyrene, a hydrophobic fluorophore. Structural characterization by dynamic light scattering (DLS) and small angle X-ray scattering (SAXS) revealed that addition of micellar β-casein to 0.05 mM κ-casein oligomers caused strong perturbation and formation of smaller micelles compared to when added to 0.3 mM κ-casein in micellar state. Thus, association of β-casein with κ-casein in these two different physical forms of loosely interacting oligomers and micelles, respectively, can modulate formation of mixed micelles with regard to structural properties such as shape, size and molecular packing (compactness).

KW - Mixed micelles

KW - SAXS

KW - Thermodynamics

KW - Tunable micellar dimensions

KW - β-Casein

KW - κ-Casein

U2 - 10.1016/j.foodhyd.2020.106459

DO - 10.1016/j.foodhyd.2020.106459

M3 - Journal article

AN - SCOPUS:85096134931

VL - 113

JO - Food Hydrocolloids

JF - Food Hydrocolloids

SN - 0268-005X

M1 - 106459

ER -