2.2.3. Ultrasound Treatment

The sample was subjected to ultrasonic treatment with a frequency of 20 kHz sonicator (Model JY92-IIN, NingBo Xinzhi Technology Co., Ningbo, China), which was equipped with a titanium probe (6 mm of diameter) in an ice bath.

A volume of 20 mL of zein solution (25 mg/mL, *w*/*v*) and 20 mL of FSG (5 mg/mL, *w/v*) was treated, respectively, by ultrasound at 52.95 W·cm−<sup>2</sup> for 10 min, with pulsed ratios was 5 s on-time/5 s off-time (U). Zein or FSG solution ultrasonicated were termed ZNPU or FSGU, respectively.

#### *2.3. Preparation of Complex Particles*

The complex particles were prepared using different ZNP and FSG by combination with homogenization and/or ultrasonication, and detailed procedures are shown in Figure 1 and Table 1. The differently treated samples were stored at 4 ◦C until use.


**Table 1.** The process of complex particles formation.

"-" in Materials indicates without the addition of a certain ingredient; "-" in Process indicates the sample without treatment by ultrasonication or homogenization.

A volume of 20 mL of ZNP-FSG complexes was also treated by ultrasound at 52.95 W·cm−<sup>2</sup> for 10 min, with pulsed ratios of 5 s on-time/5 s off-time (U). ZNP-FSG solution ultrasonicated was termed (ZNP-FSG)U.

Samples needed to be treated by a high-speed dispersion homogenizer (FJ200-SH, Shanghai specimen model factory, Shanghai, China), the homogenizing conditions were fixed at 15,000 rpm for 3 min, marked as H.

**Figure 1.** Overall schematic diagram of 11 various preparation routes, such as ultrasonicated zein (ZU), zein nanoparticles (ZNP), ultrasonicated zein nanoparticles (ZNPU), flaxseed gum (FSG), ultrasonicated flaxseed gum (FSGU), zein nanoparticles-flaxseed gum complexes by homogenization (ZNP-FSG)H, zein nanoparticles-flaxseed gum complexes by ultrasonication (ZNP-FSG)U, ultrasonicated zein nanoparticles and flaxseed gum complex by homogenization (ZNPU-FSG)H, zein nanoparticles and ultrasonicated flaxseed gum complex by homogenization (ZNP-FSGU)H, ZNP-FSG by homogenization and ultrasonication (ZNP-FSG)HU.
