3.3.4. Storage Stability

After storage at 25 and 45 ◦C for 7 days, quercetin-loaded HZ and HZ-chi particles precipitated, while no precipitation was observed for quercetin-loaded HZ-chi/pec particles (Figure S3). Figure 8 shows size distribution and ζ-potential of quercetin-loaded HZ-chi/pec particles during storage. Their size distribution remained a single peak during storage at 45 ◦C and increased to around 325 nm after 6 days. At 25 ◦C, the size distribution kept a single peak around 220 nm after 6 days and then showed two peaks. These results indicate quercetin-loaded HZ-chi/pec particles are more stable at 45 ◦C than 25 ◦C, possibly due to the high temperature facilitates adsorption of pectin to the particles more effectively and improves its complex formation capacity [58,59]. At 25 ◦C, a smaller size, around 90 nm was observed after storage for 13 days (Figure 8), probably due to the detachment, depolymerization and hydrolysis of galacturonic acid glycan chains of pectin at pH<5[60]. At 25 ◦C, a larger size around 900–1500 nm was observed after 20 days (Figure 8). The ζ-potential of HZ-chi/pec particles became more negative over time, both at 25 and 45 ◦C. These changes indicate the realignment of pectin during storage and exposure of more charged COO- groups at the interface, leading to an upsurge in ζ-potential [18,54]. Pectin

coating substantially enhances the colloidal stability of quercetin-loaded HZ-chi/pec compared with that of qHZ and qHZ-chi (Figure S3A,B) by preventing aggregation of particles through electrostatic repulsions and steric stabilization as well [61].

**Figure 8.** Size distribution (**A**) and ζ−potential (**B**) of quercetin−loaded hollow zein particles coated with chitosan and pectin at 25 ◦C (red) and 45 ◦C (black) during storage.
