Casein-based nanodelivery of olive leaf phenolics: Preparation, characterization and release study

Abstract

Olive leaf extract (OLE) as a rich source of phenolics has numerous health benefits for application in food formulations, nonetheless, it has limitations such as unfavorable sensory attributes, low stability and bioavailability. Correspondingly, in this work, OLE was loaded into reassembled casein micelles (r-CM) as natural nanocarriers. Based on Response Surface Methodology (RSM), optimized conditions for loading were 1.483 mg/mL of OLE, 60 min stirring time at pH = 12, and 20 mM of CaCl 2 addition. The optimized carriers were further characterized for morphology, Zeta potential and size along with Fourier-transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and X-ray diffraction (XRD) analyses. The results illustrated the formation of spherical/ellipsoid nanostructures with an average size of 150 nm and PDI of 0.249 reflecting a moderate size distribution pattern. Moreover, the loaded nanovehicles depicted a negative zeta potential (−36.7 mV). FTIR data portrayed the emergence of a peak at 2358.89 cm −1 associated with the C-H stretching related to phenolic groups of OLE. DSC thermograms and XRD tests underlined the disappearance of OLE decomposition peak and a low crystallinity after OLE entrapment, respectively. Last but not least, the release test illustrated a controlled release behavior in acidic food simulants, in addition, a Fickian-diffusion-based release mechanism was observed in all the food simulants. • Olive leaf phenolics were loaded into casein micelles. • The best encapsulation efficiency rate was 87.14%. • The average size of prepared loaded-nanocarriers was around 150.73 nm. • Best release model was Rigter Peppas for acidic and 50% ethanol food simulants. • Casein delivery system demonstrated a Fickian-diffusion release mode.