Physicochemical properties, microstructure, and encapsulation efficiency of rosemary (Rosmarinus officinalis. L) extract microencapsulated by freeze-drying using whey protein isolate and maltodextrin

• C1 sample was the most stable bead structure among treatments. • EE% was mainly affected by maltodextrin /whey protein isolate/ rosemary extract ratios • C1 treatment was the most rounded structure, with highest TPC released . Encapsulation of rosemary extract (RE) with maltodextrin (MD) and whey protein isolate (WPI) at different ratios (30:70, 50:50, and 70:30) as wall materials were studied. The ratios of wall materials: RE were 1:4, 1:8, and 1:12. For assessment of proper encapsulation, fourier transform infrared spectroscopy ) FTIR ( and scanning electron microscopy ) SEM ( were used. The effect of various wall formulations (MD/WPI ratio) on encapsulation efficiency (EE)%, and viscosity, were studied. Moreover, the release of polyphenols in water was measured for 60 min. The beads made of a higher ratio of wall materials: RE (1:12) were C1, F1, and I1 samples with MD: WPI ratio (50:50, 30:70, and 70:30) respectively, presented the highest viscosity among the samples. The EE% of C1, F1 and I1 samples were 88.96±1.0%, 88.74±1.0, and 84.01±0.76 respectively. SEM image showed that the C1 treatment was the most rounded compared to the other treatments. The FTIR spectra showed a suitable intramolecular bond between wall materials and RE. The release amount of total phenolic content (TPC) from the C1 and I1 samples was the highest and lowest respectively among the samples. In conclusion, MD and WPI were suitable wall materials for the encapsulation of RE. .