*2.2. Preparation and Characterization of Anthocyanin-Loaded Liposomes* 2.2.1. Extraction of Butterfly Bean Flower Anthocyanin

The butterfly bean flower anthocyanin (BA) was obtained according to a previous study [13]. The dried butterfly bean flower calyxes were crushed into a powder. Then, approximately 100 g of the powder was macerated with 1 L of 75% ethanol for 3 h at 60 ◦C. The solvent extraction solution was obtained using a centrifuge at 3000 r/min for 6 min. After that, the anthocyanin concentrated solution was obtained to remove the ethanol solvent using a rotary evaporator (RE-200A, SHANGHAI YARONG biochemistry instrument factory, China) at 50 ◦C for 2 h. Finally, the concentrated solution was dried in a vacuum freeze-dryer to obtain a BA powder.

### 2.2.2. Preparation of BA-Loaded Liposomes

The BA-loaded liposomes (BALs) were prepared using the ethanol injection highpressure homogenization method with some modifications [14]. Lecithin (0.2%, 0.5%, and 1%), cholesterol (0.2%), and Tween 80 (0.24%) were dissolved in an ethanol solution. The BA solution (0.2%) was prepared in an acetate buffer solution (pH 3.5, 0.05 mol/L). To obtain crude milky liposomes, the BA solution was quickly injected into lecithin mixtures of different concentrations and stirred vigorously for 30 min. Next, the crude liposomes were homogenized using a high-pressure homogenizer (AH-BASIC, Antos Nano Technology Co., Ltd., Suzhou, China) at 20,000 psi for 5 cycles. Then, the cooling solution was passed through a 0.25 μm extruder, and the solvent was removed via rotary evaporation (SY-4000, Shanghai Yarong Co., Ltd., Shanghai, China) to obtain concentrated BALs with different concentrations of lecithin at 0.2%, 0.5%, and 1% (BAL1, BAL2, and BAL3).
