Enhancing acid stability of citral through internal structure modulation in nanostructured lipid carriers with solid lipids and phospholipids

Abstract

In this current study, the internal structure of nanostructured lipid carriers was modulated by phospholipids (lecithin PC, hydrogenated soybean phospholipid HPC) and solid lipids to achieve stable encapsulation of citral. The presence of high melting point HPC could construct α-crystalline type with more lattice defects and effectively inhibit β-ization. The HPC group could maintain the particle size at 155.9-186.9 nm, the polydispersity index (PDI) at 0.182-0.321, the Zeta potential at -57.58 mV to -49.35 mV and the retention rate of citral at 91.33-98.49 % in the acidic environments of 2 mM and 20 mM hydrochloric acid solutions. The recrystallization index (RI) of NLC increased with the number of solid lipid ester bonds (from 3.57 % to 16.58 % in the PC group and from 0.82 % to 12.47 % in the HPC group). The results illustrated that the number of solid lipid ester bonds and the melting point of phospholipids affected crystallinity of the lipid matrix and thus the stability of encapsulated citral. Hydrogenated phospholipid with high melting points was more beneficial in stabilizing citral. The present study improved the acidic stability of citral and provided a new thought for the application of citral in acidic beverages.

Keywords: Citral; Internal structure; Nanostructured lipid carriers; Polymorphic transition; Stability.