Native casein micelles as nanocarriers for β‐carotene: pH‐and temperature‐induced opening of the micellar structure

Abstract

Summary To apply native casein micelles (CM) as nanocarriers for lipophilic substances in non‐ or low‐fat food products, they have to be conditioned before loading. In this study, an experimental set‐up for the production and loading of CM was developed. Microfiltration was used to separate CM from skimmed milk. To identify optimal loading conditions temperatures (2, 20, 40 °C), pH values (6.8 and 5.5) and holding times (5, 15, 30, 60 min) were varied. The release of calcium, phosphate and protein from the micellar phase as well as static light scattering and transmission electron microscopy showed that CM were optimally primed at 2 °C and a pH of 5.5 for 5 min. Therefore, loading with β‐carotene was performed under those conditions. After the back‐extraction of β‐carotene, the photometrical analyses revealed total recovery rates of >79% whereby 94% of it was associated with the native CM.

Comparative studies of loading lipophilic substances into casein micelles and investigating the influence of whey proteins and heat treatment on loading stability

“…In previous experiments, minor structural effects could indeed be determined via Fourier‐transform infrared spectroscopy, but transmission electron microscopy (TEM) and static light scattering (SLS) showed no differences between CM from skimmed milk and CM from washed retentate (Moeller et al . ).…”

“…; Moeller et al . ) with MF (average pore size 0.1 μm) and triple diafiltration at 50–55 °C. The retentate obtained contained on average 91.1 ± 3.5% casein and 8.3 ± 2.5% ( n = 31) whey protein with reference to total protein.…”

“…Casein micelle suspension conditioning was therefore conducted as described previously, by lowering the temperature and pH value (Moeller et al . ): 280–285 mL of CMS was tempered to 2 °C using a thermostatic water bath (Julabo FP 40, Seelbach, Germany). Afterwards, the pH value was adjusted to 5.5 by adding HCl (10%).…”

“…Afterwards, the pH and temperature were re‐adjusted (Moeller et al . ). These conditions, which are rather mild, can easily be applied during dairy processing, and this results in 94% of the entrapped β‐carotene ending up in the sediments (=CM) after 15 min of loading.…”

Casein and Ag nanoparticles: Synthesis, characterization, and their application in biopolymer‐based bilayer film

“…Casein acts as a good nanocarrier in food systems as it confirms homogenous distribution, protects the nutritional content against degradation by UV light during processing and oxygen during storage. It is an amphiphilic carrier which is useful for encapsulating lipophilic nutraceuticals on a large scale (Moeller, Martin, Schrader, Hoffmann, & Lorenzen, ). Reversible agglomeration occurs to the AgNPs and forms casein–silver nanocomposites.…”