*2.2. Preparation of Blank and Quercetin-Loaded Hollow Zein, Hollow Zein-Chitosan, and Hollow Zein-Chitosan/Pectin Particles*

Hollow zein (HZ) particles were fabricated with sodium carbonate sacrificial templet by mixing 1.75 mL of absolute ethanol and 2.5 mL of 50 mg/mL zein in 70% (*v/v*) ethanol– water binary mixture with 0.75 mL of 0.5, 1 and 2 (*w/v*%) Na2CO3 aqueous solution under magnetic stirring at 1000 rpm for 1 min followed by adding to a 20 mL ultra-pure water [1,21]. The HZ particles were mixed with 0.5, 1 and 2 mg/mL chitosan in 1% (*v/v*) acetic acid at a 1:1 volume ratio under stirring at 1000 rpm for 30 min. Ethanol in the particle dispersion was removed under vacuum with a rotary evaporator RE-52C (Shanghai Tianheng Instrument Co. Ltd., Shanghai, China) at 35 ◦C for 30 min. Unstable particles were separated by centrifugation the particle dispersion at 2000× *g* for 15 min; the supernatant was then centrifuged at 15,000× *g* for 30 min to remove unabsorbed chitosan, and the precipitate was redispersed in an equal volume of distilled water to obtained chitosan-coated hollow zein (HZ-chi) particles. The aqueous solutions of pectin at 0.01, 0.025, 0.05 and 0.1 mg/mL were added to the dispersion of HZ-chi particles under stirring for 30 min at pH 4–4.5 to obtain pectin- and chitosan-coated hollow zein (HZ-chi/pec) particles. The quercetin-loaded hollow particles were prepared by adding 2, 3, 4 and 5 mg of

quercetin in 50 mg/mL zein stock solution in ethanol–water binary mixture corresponding to 100, 150, 200 and 250 μg/mL of quercetin in the final particle dispersion.
