This study encapsulated walnut angiotensin-converting enzyme (ACE) inhibitory peptides within nanoliposomes and then modified them with chitosan. The resulting effect of the nanoliposome loading and chitosan coating on physicochemical characteristics, stability, bioactivity, chemical structure, and morphology of the encapsulated peptides was assessed. The resulting particle size and polymer dispersity index revealed that the chitosan-coated nanoliposomes loaded with walnut ACE inhibitory peptides (WAIP) (CL-P) exhibited higher physical stability compared with the nanoliposomes loaded with WAIP (L-P). The encapsulation efficiency (EE) of CL-P increased from 73.32% to 76.13% after chitosan modification, and the EE of L-P and CL-P could be maintained by storage at 4°C. In addition, the antioxidant activity and ACE inhibitory activity of the peptides were effectively protected by L-P and CL-P during storage. Fourier transform infrared spectroscopy showed that the nanoliposomes were bound in ionic form with both the peptides and chitosan. Transmission electron micrographs indicated the presence of vesicle-like carriers with a reservoir-type structure. This study highlights the potential of nanoliposomes and their modification with chitosan to increase the stability and bioactivity retention of ACE inhibitory peptides. PRACTICAL APPLICATION: Chitosan-coated nanoliposomes loaded with walnut ACE inhibitory peptides were prepared in this study. Chitosan coating increased nanoliposomes' encapsulation efficiency and provided higher physical stability. In addition, the bioactivity of the walnut ACE peptides was effectively protected during storage. This study was relevant for improving the storage and transportation used for nanoliposome systems applied in the food and health product industry.
Keywords: ACE inhibitory peptide; encapsulation; nanoliposome; stability; walnut.
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